Blow Through Setup - Questions

[2.5T_/<ouki]

So I'm planning on going the blow through route on my RB25, however I have some questions regarding the crankcase after i relocate the MAF.

Right now, MY PCV valve is connected to the IM and Both of my breathers up top are connected to the turbo inlet pipe via a nipple after the MAF & before the turbo.

Can i still run the crankcase breathers to the same spot now that the MAF will be on the IC cold pipe? Do i need to find a new location to run them? I do NOT want to run a catch can setup. Absolutely hate the look of it.

Thank You.


http://i1117.photobucket.com/albums/k584/rbkoukis14/1C74166E-DF33-4ED6-BC48-C214ECE3409B-22293-00000DE07400B88D_zps732b8b9d-1_zps1926da16.jpg

[ashtonroche]

Whats wrong with a catchcan setup? You can get a smaller can and locate it just as hidden as connecting it to the intake pipe.

Either way dude, its not going to make any difference whether you keep the breather lines on the intake pipe. Its just going to be remetered. You losing the metered air anyways as blowby and basically counts as getting used up by the engine.

I honestly would do a catch can though dude. Keep all the oily grime out of your chargepipes. Seriously. Its the proper way to do things. The SR comes with a catchcan from the factory as do many other motors. Its to help keep the intake manifold and intake pipes clean.

Anyways one last thing if you dont already know is when you go blowthru your a/f's will change a bit to the leaner side of things. I ran blowthrough on all my turbo setups and noticed the difference from setups that i did for others that wanted it draw through was the draw through setups always ran richer. So just keep a close eye on the A/F's when its first done. It might need to be retuned if it runs too lean under boost.

[2.5T_/<ouki]

Whats wrong with a catchcan setup? You can get a smaller can and locate it just as hidden as connecting it to the intake pipe.

Either way dude, its not going to make any difference whether you keep the breather lines on the intake pipe. Its just going to be remetered. You losing the metered air anyways as blowby and basically counts as getting used up by the engine.

I honestly would do a catch can though dude. Keep all the oily grime out of your chargepipes. Seriously. Its the proper way to do things. The SR comes with a catchcan from the factory as do many other motors. Its to help keep the intake manifold and intake pipes clean.

Anyways one last thing if you dont already know is when you go blowthru your a/f's will change a bit to the leaner side of things. I ran blowthrough on all my turbo setups and noticed the difference from setups that i did for others that wanted it draw through was the draw through setups always ran richer. So just keep a close eye on the A/F's when its first done. It might need to be retuned if it runs too lean under boost.

There are just too many lines/tubing all over the place with a catch can, i truly just do not like it. This motor does not come with a catch can from factory so I'd like for it to be as "close" to factory as possible.

So, it honestly wont matter that the line is going to the turbo inlet even after i relocated the MAF? Also, i did read online that my AFR's will be a lot learner and also learned that i would need a tune for it to work anyways. I planned on switching to blow through right before i go to the dyno to get tuned. I am on NIStune/z32 ECU. I just don't want to pressurize my crankcase and have things go bad.

[Matej]

It will still work fine in the same location.

[2.5T_/<ouki]

It will still work fine in the same location.

Thank you very much.

[Matej]

Though it may slowly sludge up your MAF sensor, especially if you drive hard often. I have no idea how effective the valve cover baffling is on RB's.

[2.5T_/<ouki]

Though it may slowly sludge up your MAF sensor, especially if you drive hard. I have no idea how effective the valve cover baffling is on RB's.


I drive like a granny. Throttle never sees over 40% throttle lol and thats when im stepping on it ;P. This is my daily driver.

[ashtonroche]

Again the amount of actual air going out of the crankcase is very minimal unless you damage the ring lands or melt something, lol.

As long as you dont have the lines on a pressurized pipe your good, which the intake pipe is not. It actually creates a vacuum to draw air out of the crankcase.

I didnt have to retune my setup going from drawthrough to blowthrough, a/fs just went from 11.3:1 or so to about 11.7-11.8:1 Not enought to need a retune. Still safe. Im just saying to make sure and monitor the a/f's

[2.5T_/<ouki]

Again the amount of actual air going out of the crankcase is very minimal unless you damage the ring lands or melt something, lol.

As long as you dont have the lines on a pressurized pipe your good, which the intake pipe is not. It actually creates a vacuum to draw air out of the crankcase.

I didnt have to retune my setup going from drawthrough to blowthrough, a/fs just went from 11.3:1 or so to about 11.7-11.8:1 Not enought to need a retune. Still safe. Im just saying to make sure and monitor the a/f's

Gotcha, will look out for that. I've got a wideband so wont be hard to monitor these. :) Do you have an RB? Did you use the stock MAF? If so, where did you place the BOV and where did you place the MAF?

[ashtonroche]

No this was on my SR, Id place the maf on the coldside chargepipe. Having hot air blow on the maf just makes the a/f's even leaner. Place it on the coldside pipe at least 6" away from the TB, preferably with at least 4-6" of straight piping before it. So on yours probably just before the bend when it comes back into the bay. Should be enough straight pipe before that that it will meter properly.

[2.5T_/<ouki]

No this was on my SR, Id place the maf on the coldside chargepipe. Having hot air blow on the maf just makes the a/f's even leaner. Place it on the coldside pipe at least 6" away from the TB, preferably with at least 4-6" of straight piping before it. So on yours probably just before the bend when it comes back into the bay. Should be enough straight pipe before that that it will meter properly.

Yeah, exactly where i was thinking of putting it. Did you have your BOV still on the coldpipe before the MAF or did you place it on the hotpipe? Mine is on the Coldpipe so i think i may need to relocate it before the MAF or put it on the hotpipe.

[ashtonroche]

Oh and at the time i was using a z32 maf. I see you sealed yours with silicon. I highly recommend coating the edges of it with jb weld if your gonna be using that one. If your getting one of the maf's in the metal housing then you should be fine.

But definitely seal that thing up tight. Also do not use a 4 bolt adapter to the maf. Easiest thing to do with the z32 maf is to just cut the adapter part off and leave a lip and a 3" coupler fits right over it with enough room for a t-bolt to fit. Ive never had one pop off the ones ive done this way and zero chances of leaking like the adapter.

[ashtonroche]

Had my bov on the hotside. You dont want the bov between the maf and tb. It can be before the maf on the coldside but yeah further away the better.

[2.5T_/<ouki]

Oh and at the time i was using a z32 maf. I see you sealed yours with silicon. I highly recommend coating the edges of it with jb weld if your gonna be using that one. If your getting one of the maf's in the metal housing then you should be fine.

But definitely seal that thing up tight. Also do not use a 4 bolt adapter to the maf. Easiest thing to do with the z32 maf is to just cut the adapter part off and leave a lip and a 3" coupler fits right over it with enough room for a t-bolt to fit. Ive never had one pop off the ones ive done this way and zero chances of leaking like the adapter.

Thanks for the heads up. Ill be using the stock RB25 MAF so I'll have to cut the adapter part off and leave a lip like you said. I do plan on using 3" silicone couplers w/ t-bolt clamps. Looks like I'll be relocating my BOV further down the cold pipe before the MAF or on the hot pipe haven't decided yet.

[2.5T_/<ouki]

QUESTION: When running a blow through setup, will the close of the TB cause any reversion to the MAF? Will it freak out in voltages? The whole reason for me going this new blow through route is to get rid of MAF reversion?

I plan to have my MAF about 8"-10" away from the TB on the cold pipe side.

Thanks

[Precision Flow Labs]

QUESTION: When running a blow through setup, will the close of the TB cause any reversion to the MAF? Will it freak out in voltages? The whole reason for me going this new blow through route is to get rid of MAF reversion?

I plan to have my MAF about 8"-10" away from the TB on the cold pipe side.

Thanks
It will be fine as long as the BOV is big enough..

[2.5T_/<ouki]

It will be fine as long as the BOV is big enough..

The BoV is after the MAF so how does that make sense? ( TB > MAF > BOV > IC > Turbo )

The TB closes the waves have to travel through the MAF before they get BoV.

Sorry if I'm sounding ignorant, i truly just don't understand.

[Precision Flow Labs]

The BoV is after the MAF so how does that make sense? ( TB > MAF > BOV > IC > Turbo )

The TB closes the waves have to travel through the MAF before they get BoV.

Sorry if I'm sounding ignorant, i truly just don't understand.

That is correct, when I say before I am talking the path of the air.. filter>turbo>IC>BOV>maf>tb. There won't be very much of a wave if the pressure is somewhat equal before and after the maf. The BOV won't vent all of the air.. there will always be some that is still pushing against the TB.

[2.5T_/<ouki]

That is correct, when I say before I am talking the path of the air.. filter>turbo>IC>BOV>maf>tb. There won't be very much of a wave if the pressure is somewhat equal before and after the maf. The BOV won't vent all of the air.. there will always be some that is still pushing against the TB.

Ok, I'm hoping it wont have any reversion. The BoV is right after the MAF so I'm not 100% sure if the pressure is somewhat equal as it will be escaping right there lol.

Also, My IACV is plumbed into the cold pipe as well and will be right AFTER the maf. This is still fine correct? Sorry again for the noob questions, i just want to get it right the 1st time.

[Precision Flow Labs]

Ok, I'm hoping it wont have any reversion. The BoV is right after the MAF so I'm not 100% sure if the pressure is somewhat equal as it will be escaping right there lol.

Also, My IACV is plumbed into the cold pipe as well and will be right AFTER the maf. This is still fine correct? Sorry again for the noob questions, i just want to get it right the 1st time.
Your before and after is confusing me lol You need to meter the air for the IACV so it needs to be downstream of the maf. Having the BOV extremely close to the maf can cause you problems.

The air goes through the turbo, AFTER that it hits the IC After that it hits the bov lol

[2.5T_/<ouki]

I might want to put the BoV on the hotpipe then because there is absolutely no room on the coldpipe unless it's really close to the MAF.

And yes, the IACV plumb is in between the MAF and TB so it will be sucking in metered air. This is fine correct?

[PrimeDirective]

Why??? Honestly, this all seems like a bad idea.

[Precision Flow Labs]

I might want to put the BoV on the hotpipe then because there is absolutely no room on the coldpipe unless it's really close to the MAF.

And yes, the IACV plumb is in between the MAF and TB so it will be sucking in metered air. This is fine correct?

That's fine.. There is nothing wrong with putting it on the hot pipe.

[Precision Flow Labs]

Why??? Honestly, this all seems like a bad idea.
Because in blow through the maf is no longer a restriction, you can vent the bov to atmosphere, drivability is much better because you are metering the air right as it actually enters the engine instead of 5' away as in draw through. Think about how long the pulse of air takes to go from the TB through the IC through the turbo finally making it to the maf.

[2.5T_/<ouki]

That's fine.. There is nothing wrong with putting it on the hot pipe.

Thank you very much. I truly appreciate your responses.

[Precision Flow Labs]

Thank you very much. I truly appreciate your responses.

Just noticed you're blowing through the stock Z32 plastic maf.. DO NOT put it on the hot side

[2.5T_/<ouki]

Just noticed you're blowing through the stock Z32 plastic maf.. DO NOT put it on the hot side

?
I'm running the stock RB25 MAF (J60) not z32 and was NOT planning on running the MAF on the hot side, I was saying I was going to put the BOV on the hotpipe.

Just out of curiosity, would I need a filter or even a turbo inlet for this setup? Doesn't seem like I would but ill have one anyways for my breathers. Just wonder if I could be cool like those huge top mount setups you see with no filters on the turbos, ha! :P

[Carl H]

i found your problem with your setup after looking at the picture a little longer... you have no pcv valve on your setup.
when you removed the stock one and put that 90* fitting on the valve cover you removed any checkvalve on the system.
whats happening is you're blowing boost pressure into the crank case and its causing the maf to proverbially shit a brick because of the reversion induced boost pressure into the maf pipe.
didnt happen with the stock setup accordion because it was angled, i assume the maf pipe is just straight on.

put a check valve on the intake side valve cover (brake booster valves work great) and i bet your problem will go away.

as far as blow thru?
ran my car for 6 years on it...works great but it can mess with the tune and you may need a retune for it, some cars do some cars dont.
your mileage may vary.

[2.5T_/<ouki]

i found your problem with your setup after looking at the picture a little longer... you have no pcv valve on your setup.
when you removed the stock one and put that 90* fitting on the valve cover you removed any checkvalve on the system.
whats happening is you're blowing boost pressure into the crank case and its causing the maf to proverbially shit a brick because of the reversion induced boost pressure into the maf pipe.
didnt happen with the stock setup accordion because it was angled, i assume the maf pipe is just straight on.

put a check valve on the intake side valve cover (brake booster valves work great) and i bet your problem will go away.

as far as blow thru?
ran my car for 6 years on it...works great but it can mess with the tune and you may need a retune for it, some cars do some cars dont.
your mileage may vary.

I appreciate your response Carl, however I do have a check valve on my PCV line going to the IM. It's literally right under the IM and the flow of direction is only able to go from valve cover to IM.

Also, I plan on doing the setup right before I get my tune.

Thank you.

[PrimeDirective]

Because in blow through the maf is no longer a restriction, you can vent the bov to atmosphere, drivability is much better because you are metering the air right as it actually enters the engine instead of 5' away as in draw through.

Besides the BOV vent which I think is dumb there shouldn't be air entering in any other part of the system, this is a moot point. He's not running a catch can so he will be putting oil and crud through his maf, and he will be pressurizing a maf sensor that was not designed to do so, so it is prone to poping.

Think about how long the pulse of air takes to go from the TB through the IC through the turbo finally making it to the maf.

This doesn't even make sense. So what, the mass of air never changes once it enters the system.

Finally, OP is getting his car tuned and they can tune it to drive just fine with a pull through set up as 99% of people do.

Also, OP I would not recommend running the car with no filter! If you DD the car this would be DUMB, you are going to suck all sorts of shit into your motor. Look how dirty an engine bay gets over time. You want to put all that stuff into your motor? I can't believe you would even consider this.

Anyways, put the MAF where it is factory and get, the car tuned and be done with it. Don't put oil through the maf and don't suck in every piece of random shit into your engine.

[Precision Flow Labs]

Besides the BOV vent which I think is dumb there shouldn't be air entering in any other part of the system, this is a moot point. He's not running a catch can so he will be putting oil and crud through his maf, and he will be pressurizing a maf sensor that was not designed to do so, so it is prone to poping.



This doesn't even make sense. So what, the mass of air never changes once it enters the system.

Finally, OP is getting his car tuned and they can tune it to drive just fine with a pull through set up as 99% of people do.

Also, OP I would not recommend running the car with no filter! If you DD the car this would be DUMB, you are going to suck all sorts of shit into your motor. Look how dirty an engine bay gets over time. You want to put all that stuff into your motor? I can't believe you would even consider this.

Anyways, put the MAF where it is factory and get, the car tuned and be done with it. Don't put oil through the maf and don't suck in every piece of random shit into your engine.
Actually there is a tip in fuel parameter in the ecu strategy that accounts for the lag in response from the maf if we are getting technical. You are right blowing through a maf that was not designed for it is a bad idea. But, a properly set up turbo car (catch can etc.) will always run better and have better drivability with a blow through maf. My point with venting the bov wasn't for the super sweet whoosh should it was for simplicity and aesthetics in the engine compartment.
The mass does change for a split second when the throttle is opened and a low pressure area is created in front of the TB that progressively smaller as you move away. The mass in the complete intake tract doesn't equal again until enough air flows past the maf to equalize the pressure. At that point the mass of air flowing through the maf is finally the same as the mass of air flowing into the throttle body. We're you referring to the volume instead?

[Precision Flow Labs]

?
I'm running the stock RB25 MAF (J60) not z32 and was NOT planning on running the MAF on the hot side, I was saying I was going to put the BOV on the hotpipe.

Just out of curiosity, would I need a filter or even a turbo inlet for this setup? Doesn't seem like I would but ill have one anyways for my breathers. Just wonder if I could be cool like those huge top mount setups you see with no filters on the turbos, ha! :P
You need to run a filter.. And if you have a well designed filter with an internal Venturi it will actually flow more than no filter at all.

[2.5T_/<ouki]

You need to run a filter.. And if you have a well designed filter with an internal Venturi it will actually flow more than no filter at all.

Will do
Thank you very much

[2.5T_/<ouki]

Oh and at the time i was using a z32 maf. I see you sealed yours with silicon. I highly recommend coating the edges of it with jb weld if your gonna be using that one. If your getting one of the maf's in the metal housing then you should be fine.

But definitely seal that thing up tight. Also do not use a 4 bolt adapter to the maf. Easiest thing to do with the z32 maf is to just cut the adapter part off and leave a lip and a 3" coupler fits right over it with enough room for a t-bolt to fit. Ive never had one pop off the ones ive done this way and zero chances of leaking like the adapter.

So "cutting" the adapter part on the MAF would mean that you would actually be cutting away one side of the screen correct? I wouldn't think that's a good idea. How did you put the screen back on if you ended up doing it this way?

[ashtonroche]

Remove the screen, it has no ill effect on the motor. You dont have to cut where the screen is held in by the clip. Basically just take the square and turn it into a circle and leave a ridge kinda like a a rolled or beaded pipe would be. Your just cutting off the corners where the adapter would bolt and just making a circle. A dremel with a cutting disk works perfectly for the job. Take your time and you have nothing to worry about.

Ive ran every z32 maf blowthrough an removed the screen on each one with no issues. You would rather have it off than have it break away and go into the motor anyways.

[OrangeVirus1]

Don't know if it has been said before, but I will throw it out there, I have ran some blow through setups before on cars, and if you don't have a way of tuning, it won't go well. I can almost guarantee you will max your maf out too soon.

I've ran a turbo with no filter, just a screen, if it is a top mount, away from the ground, you should be ok. but low to the ground no way. also prepare to loose some power, spool time etc from a screen.

and yeah a well placed filter with a Trumpet / velocity stack can flow more/better air than no filter at all.

[2.5T_/<ouki]

Remove the screen, it has no ill effect on the motor. You dont have to cut where the screen is held in by the clip. Basically just take the square and turn it into a circle and leave a ridge kinda like a a rolled or beaded pipe would be. Your just cutting off the corners where the adapter would bolt and just making a circle. A dremel with a cutting disk works perfectly for the job. Take your time and you have nothing to worry about.

Ive ran every z32 maf blowthrough an removed the screen on each one with no issues. You would rather have it off than have it break away and go into the motor anyways.

Awesome, thanks for your response. I've heard the screen helps stabilize the airflow coming in and this is exactly what I need.

Don't know if it has been said before, but I will throw it out there, I have ran some blow through setups before on cars, and if you don't have a way of tuning, it won't go well. I can almost guarantee you will max your maf out too soon.

I've ran a turbo with no filter, just a screen, if it is a top mount, away from the ground, you should be ok. but low to the ground no way. also prepare to loose some power, spool time etc from a screen.

and yeah a well placed filter with a Trumpet / velocity stack can flow more/better air than no filter at all.

Thanks for your input. I plan on putting this blow through system on right before my tune. It's NIStune

[ashtonroche]

the screen straightens the air coming in and yes stabilizes it. But like I said if you give at least 4-6" of straight pipe before the maf it wont matter. Just take the screen out. I saw no difference with one in vs out. None.

[2.5T_/<ouki]

the screen straightens the air coming in and yes stabilizes it. But like I said if you give at least 4-6" of straight pipe before the maf it wont matter. Just take the screen out. I saw no difference with one in vs out. None.

Does it matter how many inches are AFTER the MAF? Right now, I'm trying to put it in the longest run of straight pipe i have, however there isnt about 4-6" before the MAF as i have placed the MAF about 8" away from the TB. There is probably about 2" BEFORE.

If i can run the MAF closer to the TB i would then be able to have 4-6" straight pipe before the MAF

Thanks

[ashtonroche]

It doesnt matter on the after, its the before the maf that counts.

[2.5T_/<ouki]

It doesnt matter on the after, its the before the maf that counts.

Thanks for that info.
I've read a lot that people so to have it at least 6-8" away fromt the TB, but It sure does seem like the before is what would matter the most. I think i'll rework my sketch so i have more run before the MAF.

Something i just realized. Wouldn't having it too close to the TB cause reversion? Seems like it would and again, reversion is the whole reason im going blow through as i get it with my setup now.

[OrangeVirus1]

Don't put it tooo close to the throttlebody, the velocity of the air moving at the throttlebody is different then where it would be stock, it would be reading False airflow because of the velocity of the moving air

[2.5T_/<ouki]

Don't put it tooo close to the throttlebody, the velocity of the air moving at the throttlebody is different then where it would be stock, it would be reading False airflow because of the velocity of the moving air

I was thinking the same thing. The only spot i can put it would leave me with about 5" from the TB and about 3-4" of straight pipe after it before it hits the 90* that goes to the IC. Hopefully it will work at this location.

Does velocity really matter with our style hotwire MAF's? I was under the impression that only "volume" was accounted for.

Can anyone chime in on this?

[ashtonroche]

That will be fine.

[[email protected]]

I was thinking the same thing. The only spot i can put it would leave me with about 5" from the TB and about 3-4" of straight pipe after it before it hits the 90* that goes to the IC. Hopefully it will work at this location.

Does velocity really matter with our style hotwire MAF's? I was under the impression that only "volume" was accounted for.

Can anyone chime in on this?

After the maf is less of a concern. Its the flow before the maf that really matters. The longer the straight section before the maf the better in terms of linearity of the airflow. Stock mafs expect perfect linear airflow.
If you want an example, some GM mafs are part of the throttle body.

[2.5T_/<ouki]

After the maf is less of a concern. Its the flow before the maf that really matters. The longer the straight section before the maf the better in terms of linearity of the airflow. Stock mafs expect perfect linear airflow.

Great info thank you.

So how far from the butterfly on the TB should the MAF be, and is it to the start of the MAF or the where the sensor is located?

I'm afraid of getting reversion on the MAF from the TB closing, but if it's not an issue i wont worry about it.

[[email protected]]

If you want a pretty safe bet, take 2.5-3 times the diameter of the TB blade and stay that far away from the TB, that will keep the reverberation to a minimum. Like I said before, the longer the straight section before the maf the better and is more important.

[2.5T_/<ouki]

If you want a pretty safe bet, take 2.5-3 times the diameter of the TB blade and stay that far away from the TB, that will keep the reverberation to a minimum. Like I said before, the longer the straight section before the maf the better and is more important.

I have a 90mm Q45 TB, so that would be about 7-10.5 inches. So is that TB butterfly to actual sensor in the middle of the MAF ? OR should that be butterfly to start of the MAF?

Thanks.

[[email protected]]

I have a 90mm Q45 TB, so that would be about 7-10.5 inches. So is that TB butterfly to actual sensor in the middle of the MAF ? OR should that be butterfly to start of the MAF?

Thanks.

At most, take midline of the tubing at the throttle plate to the maf sensor. This is really just a guide line, not exact. Like I said, GM meters are integrated into the throttle bodies with no ill effects.

[2.5T_/<ouki]

At most, take midline of the tubing at the throttle plate to the maf sensor. This is really just a guide line, not exact. Like I said, GM meters are integrated into the throttle bodies with no ill effects.

Ok great, I'll go ahead and do this. Hopefully all is well.

I appreciate the info.

[[email protected]]

Good luck. blow through is what we are pushing towards. we have a set up we are working on, hopefully this works for you as well.

[OrangeVirus1]

The maf's don't actually measure The true amount of air, like most 0-5V mafs what they do is measure the Resistance between two points, determined by how much air is moving between them, the more velocity there is the quicker the air is moving past those two points, the more the resistance goes up.

I say velocity, not amount, because @ the throttle plate there is alot more velocity then the stock location. The maf resistance would be telling the ecu "we are getting 3 volts worth of air!" when truly you might be betting like 1.2 volts.

[Precision Flow Labs]

The maf's don't actually measure The true amount of air, like most 0-5V mafs what they do is measure the Resistance between two points, determined by how much air is moving between them, the more velocity there is the quicker the air is moving past those two points, the more the resistance goes up.

I say velocity, not amount, because @ the throttle plate there is alot more velocity then the stock location. The maf resistance would be telling the ecu "we are getting 3 volts worth of air!" when truly you might be betting like 1.2 volts.
Very close

In a hot-wire MAF sensor, the wire is heated to about 210 degrees F above the incoming air temperature.
As air passes through the element, it cools it and thereby increases the amount of current needed to heat it up again.
Because the necessary current varies directly with the temperature and the density of the air entering the intake, the amount of current is directly proportional to the air mass entering the engine.
The circuit in the maf maintains a constant temperature differential between the two wires.

velocity is inversely proportional to the area of the maf housing only. not what is behind the maf. In testing we have found that only about one times the area of the maf needs to be given before any cross sectional area change. This is verified in late 90's and early 2000's gm vehicles where the mass flow sensor is placed directly in the throttle body (about two inches in front of the throttle blade).

Velocity * cross sectional area = Volumetric flow
Volumetric flow * air density = Mass flow

[2.5T_/<ouki]

Very close

In a hot-wire MAF sensor, the wire is heated to about 210 degrees F above the incoming air temperature.
As air passes through the element, it cools it and thereby increases the amount of current needed to heat it up again.
Because the necessary current varies directly with the temperature and the density of the air entering the intake, the amount of current is directly proportional to the air mass entering the engine.
The circuit in the maf maintains a constant temperature differential between the two wires.

velocity is inversely proportional to the area of the maf housing only. not what is behind the maf. In testing we have found that only about one times the area of the maf needs to be given before any cross sectional area change. This is verified in late 90's and early 2000's gm vehicles where the mass flow sensor is placed directly in the throttle body (about two inches in front of the throttle blade).

Velocity * cross sectional area = Volumetric flow
Volumetric flow * air density = Mass flow


Excellent info! Thanks for that.

So it sounds like what matters most is the area before the MAF.

[Razi]

I recently changed to a blow-through setup, and the MAF is very close to the bend and I haven't had any ill effects.

If you guys want something to straighten out the air, you can buy a honeycomb to put in front of the MAF.
Honeycomb for MAF (http://saxonpc.com/100mm-cells-for-100.html)

One question I have is, since I don't need to recirc my BOV, would putting a filter on the end of the recirc hose and letting it pull air help the turbo suck in more air? Or would that make little difference?

[2.5T_/<ouki]

I recently changed to a blow-through setup, and the MAF is very close to the bend and I haven't had any ill effects.

If you guys want something to straighten out the air, you can buy a honeycomb to put in front of the MAF.
Honeycomb for MAF (http://saxonpc.com/100mm-cells-for-100.html)

One question I have is, since I don't need to recirc my BOV, would putting a filter on the end of the recirc hose and letting it pull air help the turbo suck in more air? Or would that make little difference?


Close to what bend? The one right before the TB or right after the IC and before MAF?

I'm not sure I follow what you meant by filter on the recirc hose. Are you refgering to the turbo inlet pipe? I wouldn't see the need to have a hose connected to your BOV if it isn't recirculated lol.

[2.5T_/<ouki]

So i got around to hooking up my blow through setup to just make sure everything is good to go before i go in for the tune this Saturday. Everything seemed good and hooked up well, however im still confused on some parts.

Now like you guys did say it will run LEAN without a tune and thats exaclty what it is doing. I didn't bother driving it as i didn't want to ruin anything but i did let it idle and the AFR's are off the chart, probably 20+ as i am getting " - - - " on my AEM Uego.

QUESTION: If you look at my crankcase breathers up top, they run to the turbo inlet pipe. Now, to me this looks like a vacuum leak now that the MAF is in blow through setup. Am i correct? The intake manifold is now pulling in air after the MAF if you think about it. Wouldn't this mean it's pulling in non metered air?

I'm hoping someone can clear this up for me.

Thank You.

[[email protected]]

Any air being vented from the crankcase is technically not metered air to begin with. It is air that should have already been consumed in the combustion event and makes its way mostly through blowby of the rings, valves, and or turbo seals. The turbo intake is not sealed, it is open to atmosphere all the time whether blow through or draw through maf setup, or even throught the stock air box, which is how fresh air enters the system. So it is not a leak. It just adds the pull of the turbo to help evacuate the crankase pressure when the engine is under high load. On an engine in good condition, the crankcase will actually pull fresh air from the intake pipe into the engine crankcase at idle and low loads. Which actually uses metered air that doesn't make it to the combustion chamber. This is one reason there are fuel trims or closed loop at idle and cruise.

In a blow through set up the maf only sees what is about to enter the engine until it passes the intake valve, that is all that needs to be completely leak free/sealed. Because of this, blow through set ups are usually better because it is reading only what enters the engine at that time. Of course this is assuming an appropriate sensor that can be used as a blow through is utilized.

Hope that helps.

[2.5T_/<ouki]

Any air being vented from the crankcase is technically not metered air to begin with. It is air that should have already been consumed in the combustion event and makes its way mostly through blowby of the rings, valves, and or turbo seals. The turbo intake is not sealed, it is open to atmosphere all the time whether blow through or draw through maf setup, or even throught the stock air box, which is how fresh air enters the system. So it is not a leak. It just adds the pull of the turbo to help evacuate the crankase pressure when the engine is under high load. On an engine in good condition, the crankcase will actually pull fresh air from the intake pipe into the engine crankcase at idle and low loads. Which actually uses metered air that doesn't make it to the combustion chamber. This is one reason there are fuel trims or closed loop at idle and cruise.

In a blow through set up the maf only sees what is about to enter the engine until it passes the intake valve, that is all that needs to be completely leak free/sealed. Because of this, blow through set ups are usually better because it is reading only what enters the engine at that time. Of course this is assuming an appropriate sensor that can be used as a blow through is utilized.

Hope that helps.

Thank you for your input.
So, in an idle situation, the crankcase is being vented becuase the intake manifold is sucking in air from the PCV valve, and when under boost, the turbo is then created the vacuum and the crankcase is then being vented from the breathers through the turbo. Is this correct? This seems like a vacuum leak to me under idle. I see that when the MAF was in draw through it didnt seem like a vacuum leak because the air that was being sucking in by the intake manifold through the PCV valve, through the breathers, was actually metered air right after the MAF. Now it just seems like it's a huge vacuum leak coming from the intake manifoldbecause the MAF has changed it's location.

Would it be best to just block off the PCV valve and then vent the breathers to the turbo inlet pipe like i have?


PCV valve to intake manifold. There is a check valve right under the manifold.

http://i1117.photobucket.com/albums/k584/rbkoukis14/F3803D3B-3A0A-4657-94AD-74D9AF03917E-14041-0000043DB9FC45C0_zpsd122afce.jpg


Crankcase breathers to Turbo inlet


http://i1117.photobucket.com/albums/k584/rbkoukis14/F9FB2859-343F-43B4-8E75-23526CF69FB1-14041-0000043DC04BB5B0_zps8b745005.jpg

http://i1117.photobucket.com/albums/k584/rbkoukis14/760A9164-18FB-4746-9235-81E076A60B5E-14041-0000043DC5D0EB62_zps0c6dacb4.jpg

[feito]

Either vent or cap off the pcv, kinda youre only option with ur new setup

[[email protected]]

My experience on a daily driven turbo car is to keep a pcv setup like you have with the check valve on the manifold to keep the most possible vacuum on the crankcase during idle and cruise. It keeps your rings seated better preventing blowby and oil form pushing past turbo seals. I used to put an air/oil seperator inline to prevent additional oil ingestion. I like to use a catch can set up for breathers however to stop oil from getting back into the intake.

Your set up in no way is a vacuum leak. It is the same as stock, the location of the maf is not relevent for that. In stock location the maf won't meter air coming from the crank case. It gets pulled back into the turbo and back to the engine. With a blow through that air is now completely metered at all times.

[[email protected]]

I may have just got what you are asking.....Air does not go from breather to pcv to intake manifold. Its in vacuum, its pressure, not flow.

[2.5T_/<ouki]

Either vent or cap off the pcv, kinda youre only option with ur new setup

I was thinking the same thing. I think I'll cap off the PCV port and leave my crankcase breathers as is.

[2.5T_/<ouki]

I may have just got what you are asking.....Air does not go from breather to pcv to intake manifold. Its in vacuum, its pressure, not flow.


Ok, so I will explain exactly what my system is doing. If you're looking at my engine.

@ Idle:
IM<---Check Valve<---PCV port<---Breathers<---Turbo Inlet

@Boost:
IM xxx Check Valve xxx PCV Port--->Breathers--->Turbo Inlet

This is exactly how my engine is functioning at the moment. Looks like a vac leak to me. The check valve is allowing a vacuum from IM to PCV port which is then causing the breathers up to to have a vac which is pulling in air from the turbo inlet. Once boost hits, my check valve closes off the connection from PCV to IM.

I got the diagram for over on a DSM forum.


This is on a stock system with MAF in orginal place.
Now since my MAF is moved, it seems as tho it's a vac leak.

http://www.dsmtuners.com/forums/attachment.php?attachmentid=108090&d=1270306303

http://www.dsmtuners.com/forums/attachment.php?attachmentid=108091&d=1270306303

[[email protected]]

I know the set ups very well. I have been running that setup on blow through for many years. It doesn't matter where the maf is. There will be no vacuum leak.
I still don't recommend removing pcv set up. I have always had oil blowing into past turbo, smoking, and oil in IC pipes on daily driven cars because of not evacuating enough crankcase pressure at cruise.


At the end of the day, it is your car and you can do what you want.

[2.5T_/<ouki]

It doesn't matter where the maf is. There will be no vacuum leak. It will actually be better than the stock set up, because stock doesn't read the additional air getting back into the system from the breathers when at wot.
I still don't reccomend removing pcv set up. I have always had oil blowing into past turbo, smoking, and oil in IC pipes on daily driven cars because of not evacuating enough crankcase pressure at cruise.

I have run many cars the way your set up is in blow through with no ill effects.

At the end of the day, it is your car and you can do what you want.

Gotcha. I'm not sure why it seems like a vac leak to me. Technically my breathers have a vac to atmosphere because of the PCV being hooked to the IM. Connecting the breathers to the turbo inlet pipe is just like having it unhooked dangling there sucking in any and all atmospheric air it wants to. Am i making any sense?

It just seems that air is being pulled in from the IM that is NOT metered... With stock setup the IM was pulling in air from the breathers right AFTER the maf which was metered air.

[[email protected]]

http://i2.photobucket.com/albums/y23/antilag_200/evo/DSC01531.jpg

That is our set up on an evo. 35r turbo for 60000 miles with pcv and 2 breathers in blow through configuration. Exactly the same as your current set up.
Had oil blowby if pcv was removed.

[2.5T_/<ouki]

Looks nice man.

My AFR's were in the 20's at idle yesterday with how I'm describing, and once i blocked the PCV port they went back down to 17.5 at idle.

I know it's because i need a tune with the blow through setup, but being in the 20's and then back to 17's with plugging it seems like it was running super lean as it had a vac leak.

[[email protected]]

It actually richens up 3 points? I have never noticed any afr change when removing a pcv set up. Are you sure the clamp on the nipple for the pcv the one way valve and to the manifold were air tight and not drawing in fresh air?

[2.5T_/<ouki]

It actually richens up 3 points? I have never noticed any afr change when removing a pcv set up. Are you sure the clamp on the nipple for the pcv the one way valve and to the manifold were air tight and not drawing in fresh air?

Yes 100% completely tight. And yes it is drawing in fresh air from the breathers up top lol. This is the whole reason why i think it's a vac leak lol. It is entering the system unmetered from the breathers up top going into the valve cover, through the PCV port and into the IM AFTER the maf.

[silverv35]

maybe a retarded question but do u have a vac/boost gauge or just a boost. you should have very crappy vacuum at idle and rev decel if its an actuall constant leak as you describe.


ok i just re-read your whole thread, i think your just using the term "vac leak" but what might in fact be happening is as you said. At only at Idle should it run leaner cause your crank case is sucking in fresh un-metered air. at boost though ur pcv should work and shut and af readings should be more normal maybe a bit leaner do the the maf relocate shouldnt be off the scale. any one please feel free to correct me if im worng.

[2.5T_/<ouki]

maybe a retarded question but do u have a vac/boost gauge or just a boost. you should have very crappy vacuum at idle and rev decel if its an actuall constant leak as you describe.


ok i just re-read your whole thread, i think your just using the term "vac leak" but what might in fact be happening is as you said. At only at Idle should it run leaner cause your crank case is sucking in fresh un-metered air. at boost though ur pcv should work and shut and af readings should be more normal maybe a bit leaner do the the maf relocate shouldnt be off the scale. any one please feel free to correct me if im worng.

Sadly, its jusr boost ans the idke was very crappy.

Exactly what I'm trying to say. At idle it is a vac leak since the crankcase is sucking in fresh unmetered air; correct at boost it closes off and the crankcase vents to turbo inlet.

I'm thinking about just capping off the PCV port and leaving the breathers connected to turbo inlet like they already are.

[silverv35]

honestly i dont have the blow-trough but i do have the pcv blocked to intake and instead routed the pvc with vent to intake plumbing so i lose the suck at idle but i am just waiting to do a catch can setup < Sr btw.

[2.5T_/<ouki]

honestly i dont have the blow-trough but i do have the pcv blocked to intake and instead routed the pvc with vent to intake plumbing so i lose the suck at idle but i am just waiting to do a catch can setup < Sr btw.

I absolutely hate the look of a catch can. Thats the only reason i wont do it. That an the funds lol. I'm just not a fan of having plumbing all over the place in the engine bay. I think im going to block off my PCV.

:w00t:

[silverv35]

i run mine like this. block vent up to the valve cover vent capped off the t so its basically a 90 into the head then used the pcv to the intake piping after the maf. i did this to make the crank case fumes use up the entire valve cover baffling before its comes out now i have verrry little oil from the venting of the crank case but thats just a sr thing.

im just wondering if when they tune it they will just tune the idle/ cruise to compensate for the extra air. so u should be ok leaving as is after tune. not a perfect scenario but i wouldnt sweat it since its not an issue under load

[2.5T_/<ouki]

i run mine like this. block vent up to the valve cover vent capped off the t so its basically a 90 into the head then used the pcv to the intake piping after the maf. i did this to make the crank case fumes use up the entire valve cover baffling before its comes out now i have verrry little oil from the venting of the crank case but thats just a sr thing.

im just wondering if when they tune it they will just tune the idle/ cruise to compensate for the extra air. so u should be ok leaving as is after tune. not a perfect scenario but i wouldnt sweat it since its not an issue under load

Well, i really don't put load on my car as this is my DD so I'm going to tune for patial throttle. I honestly could care less about WOT and all that as i never even step on it. I mostly do city driving so having a vac leak would def not be good as it would be killing my MPG.

[Precision Flow Labs]

Ok I understand what you are saying. You are correct the way it is set up now, at idle anything going through the PCV is un-metered. Any time you use breathers the same is true. Blow through or draw-thru. You just need to account for this in the tune. If your AFR is in the 20's your fuel trims are obviously pegged in one direction. The fuel trims will target 14.7 and will allow you about + or - 20%. If your tune is correct the O2 feedback will correct for the small amount of un-metered air passing through the PCV.

[2.5T_/<ouki]

Ok I understand what you are saying. You are correct the way it is set up now, at idle anything going through the PCV is un-metered. Any time you use breathers the same is true. Blow through or draw-thru. You just need to account for this in the tune. If your AFR is in the 20's your fuel trims are obviously pegged in one direction. The fuel trims will target 14.7 and will allow you about + or - 20%. If your tune is correct the O2 feedback will correct for the small amount of un-metered air passing through the PCV.

Exactly!
Thank you for understanding. I was almost 100% certain it was a vac leak under idle/no boost (which is most of my driving).

I'm just going to block off the PCV port and run the breathers like i currently am.

[Precision Flow Labs]

Well it's not really a vac leak. It's just unmetered air. That small amount of air passing through the pcv was accounted for when the engine/ecu was designed. Even stock when the Crankcase vents go to the inlet of the turbo that inlet has VERY little negitive pressure. The manifold vac is way lower. so it's really no different than venting the crankcase with breathers. (not speaking to the metered air part).

[2.5T_/<ouki]

Well thank you to all that have helped me go blow through setup. I set everything up and got it all hooked up and running today. It actually runs pretty well without a tune! AFR's were pretty good as well. I will hopefully be going in for a tune tomorrow.

There is one thing i need to sort out tho. When i get on the boost, i hear a whistling noise from where the MAF is. Sounds like it could be a boost leak, probably the top part of the MAF about to blow out lmao.

[Ilya]

Could you summarize what you did/ how your set up works? setup, tune, etc, picture of how everything is connected.

Thank you

[2.5T_/<ouki]

Could you summarize what you did/ how your set up works? setup, tune, etc, picture of how everything is connected.

Thank you

I'll have to take some pictures tomorrow for you when there is sunlight but ill try and explain.

I moved the MAF to the Intercooler Cold Pipe side about 6" from the TB. I then had to relocate my BoV to the hotpipe.

I'm running a z32 ECU w/ mods for RB25 w/ RB25 base image (No Tune yet).

Here is a lil pic that i just drew up lol.

http://i1117.photobucket.com/albums/k584/rbkoukis14/bt_zps7dfe40c0.jpg

[Ilya]

I like the pic!!! GREAT WORK!!! :) the PVC valve on the valve cover is eliminated? are you able to drive around without a tune?

[2.5T_/<ouki]

I like the pic!!! GREAT WORK!!! :) the PVC valve on the valve cover is eliminated? are you able to drive around without a tune?

PCV port on my VC is eliminated yes. I have pluged it as well as the port on the intake manifold it was running too. I am able to drive around with this and i do get pretty decent AFR's. It's about 14.2-15 while cruising around city and about 14.7-15.2 while idling. I know it would be better when i do get a tune, but for now it's running so i can get from point A to point B. I'm hearing a little hissing noise, probably from the couplers that are on the MAF, so hopefully i sort that out.

[smoked240]

Good job man!! I was just about to convert to blow-through but went MAP instead :) Make sure to post some numbers later if it's going on the dyno!

[2.5T_/<ouki]

Good job man!! I was just about to convert to blow-through but went MAP instead :) Make sure to post some numbers later if it's going on the dyno!

Thanks! It's def going on the dyno. MAP would have been Ideal but NIStune does not support it.

[2.5T_/<ouki]

For anyone wanting to see how I did things.
&
Thank you to all those that helped me achieve this setup.



http://i1117.photobucket.com/albums/k584/rbkoukis14/6FE4EB09-F71E-4E21-8581-A2CDD60E1E19-3774-00000179104D0235_zps56aa2b75.jpg

http://i1117.photobucket.com/albums/k584/rbkoukis14/41AEE4F2-1094-4271-BA18-678BF0E0978D-3774-000001791904AD6F_zps798ceb04.jpg

http://i1117.photobucket.com/albums/k584/rbkoukis14/F6124D83-B7B7-4689-B545-C117F14A63CC-3774-000001791FF94883_zps12f94504.jpg

http://i1117.photobucket.com/albums/k584/rbkoukis14/2C9D9E95-534B-4146-B198-93E873743DE8-3774-00000192F50684A9_zps66b54bcf.jpg

[silverv35]

Good work :-)

[Precision Flow Labs]

Now it's time for you to buy one of our blow through mafs :)

[2.5T_/<ouki]

Now it's time for you to buy one of our blow through mafs :)

Haha i was thinking about it to be honest. The Stock RB MAF is actually holding up for what i need. I'm only running a stock RB.

[2.5T_/<ouki]

Soooo I got some dyno time and the car tuned today. I'm diss appointed :[
VTC not working but getting power to the plug so maybe the solenoid is stuck/jammed.
MAF is maxing out (5v) @ 6500 RPM - Not sure why. Thought it could hang with stock RB

It made a sad 230HP


@ Precision Flow Labs, I'm considering purchasing your blow through setup, but is there any way to get it in a 3" housing instead of 90mm? How does this compare to the lightning MAFs?

[[email protected]]

3" tubes is how we will be selling the blow through mafs. I know our maf will emulate the z32 curve in a larger housing where the lightening maf's curve is not close at all. We can also calibrate the maf for whatever setup you are running to prevent pegging no matter what power level you are trying to achieve. The lightening mafs also have a 4 bolt flange on one end that would need an adapter and large reducer couplers before and after to get into blow through set ups.

[2.5T_/<ouki]

Does anyone have any experience with both J60 & N62 MAF's in blow through? My J60 maf maxed out @ 5v around 6500 RPM. Im in need of a different MAF and just wondering if the N62 will be able to handle blow through better than the J60.