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.

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

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

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

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

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

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

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

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

2.5T_/<ouki

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

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

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

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

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

Precision Flow Labs

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

Thank you very much. I truly appreciate your responses.

Precision Flow Labs

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

2.5T_/<ouki

?
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.

__________________
Of all the things I've lost, I truly miss my mind the most.

2.5T_/<ouki

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

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.