News on Cobra MAF/50#inj/stock ECU

[AceInHole]

Here's the FA thread by asad:
Stock ECU with larger MAF and injectors (http://forums.freshalloy.com/ubbthreads/showflat.php?Cat=&Board=UBB9&Number=67267054&page=0&view=collapsed&sb=5&o=&fpart=1)

Short answer: "It works, but."

So.... for now the "best" way is the stock MAF with a bypass.... although it's unknown exactly how large a bypass you can use (and thus how large injectors you can use).

[Jeff240sx]

*YAY!*
Now I can get the Cobra MAF and not have to spend $$$ on a JWT ecu.
I do have an S-AFC, so I can make some adjustments on the car. My only question is: Will I have to adjust the voltage to/from the MAF with the afc? Or will it just work, assuming no cold starts?
-Jeff

[AceInHole]

Well... all the AFC does is adjust the volatage from the MAF...

It seems as though all you'd have to do is adjust the A/F at and near idle and it would run fine. As I have said before, I'm pretty sure all MAFs work on the same voltage range overall. So, if the curves are close enough in general you shouldn't have a prob.

What might be a problem is if the overall curve is different altogether, in which case you could use the AFC to adjust the entire curve. Time with a wideband O2 would make those adjustments much easier and more precise. As for me.... I'm going to be attempting to make my own wideband O2 controller :P www.diy-wb.com

[Jeff240sx]

Ok. Then my next question.
What does the JWT computer do for it's $595? I know that the timing has to be retarded as the engine sees boost, so does the JWT ecu account for that? But then isn't the factory ECU retard timing too? They map the fuel curve, but for 1/2 the price, so does an AFC. So what, what do they really do?
-Jeff

[DarkRaptor42]

Id think that the JWT ECU simply adjusts the fuel curve with a chip in the ECU, possibly making more fuel in certian places yada yada. I dont know for sure but I figured that anything you can do with the JWT can be done with greddy emange or SAFC. Im glad this all worked out.

There was a guy on the Nissan infity boards who got banned because all he did was wage war on the JWT ECU, he said it was trash, guess he was right.

[DarkRaptor42]

ACe, I just read the thing on the DIY WB O2 sensor. Thats insanely cool. How do you find this stuff??

[AceInHole]

Originally posted by Jeff240sx
Ok. Then my next question.
What does the JWT computer do for it's $595? I know that the timing has to be retarded as the engine sees boost, so does the JWT ecu account for that? But then isn't the factory ECU retard timing too? They map the fuel curve, but for 1/2 the price, so does an AFC. So what, what do they really do?
-Jeff

JWT ECU takes out tip-in retard, takes off the fuel cut, and you can set a higher rev limit if you want.
Otherwise, the timing maps and fuel maps are adjusted along all the stock points, afaik. The advantage of the JWT over an AFC is that you get more adjustment points (i THINK) and you're "guaranteed" a working/ optimized fuel and timing map, compared to having to go to a dyno with a wideband O2 to optimize or even adjust your fuel map to something useable. One problem Asad brought to mind is that the stock ECU might use a different timing map since it's seeing less airflow... but so far at least with 370cc injectors that problem hasn't come up.

As far as the JWT ECU being trash.... I wouldn't say that. The Greddy E-manage only has like 5 or 6 points where you can adjust the fuel map. The stock ECU has something like 16x16 points (or so I'm told... and told unsurely). All in all, you get the JWT name, and a more "secure" method of controlling your fuel.

As for the wideband O2... it was brought to my attention by a friend when we were talking about the accuracy of O2 sensors, and what would be needed if you want to control the wideband. www.google.com will actually find it under a search for "DIY wideband". the setup doesn't look THAT complicated... and apparently anyone with basic electronics skill can build it. I'm at least hoping that I can.... although I've got my eyes on that nifty LCD display setup that shows the numerical value :D

[Jeff240sx]

The S-AFC v.II has 12 adjustable points, at 200 rpm intervals.
And what page are you talking about. I can give you hints as I have a basic knowledge of electronics and wiring. And my grandfather is an electrical engineer.
We need to team up man!
-Jeff

[AceInHole]

Originally posted by Jeff240sx
The S-AFC v.II has 12 adjustable points, at 200 rpm intervals.
And what page are you talking about. I can give you hints as I have a basic knowledge of electronics and wiring. And my grandfather is an electrical engineer.
We need to team up man!
-Jeff

www.diy-wb.com

The controller can be made from parts available from there (kit and board) for around $30. Hey.... if you can do one for me I'd give ya $50 for it :D

[DuffMan]

Ok, this is nice but it makes absolutely no sense.

So the cobra mafs and 50lb injectors and cobra mafs work well enough to drive the car. Yippee!

If you are going to tune it with an SAFC then why not just get a Z32 or Q45 or even a Lexus GS400 MAFS which the SAFC is ACTUALLY PROGRAMED FOR instead. They are all cheap in junk yards.

This way you select the input as the mafs you got, the output as the KA24 mafs, and add a correction factor equal to the change in injector size. That would give you a baseline to tune from which would theoretically be perfectly equal to stock.

Playing arround with a mystery MAFS and guessing on correction factors and such with an SAFC would really require a dyno to be safe on boost. And getting part throttle and part boost right would be pretty difficult. Using a known-to-the-SAFC mafs would be pretty much plug and play.

[AceInHole]

Well... the hope was that you wouldn't need the AFC if the curves fit. There's still the possibility that correcting the overall curve by changing fuel pressure would work... or possibly just adjusting the idle speed.

The problem with setting up the S-AFC with its preprogrammed settings is the correction factor. You're still limited to the 50% adjustment using the S-AFC, since its program is set for the stock injectors. The only advantage is that you're freeing up any restriction you might have had with the stock MAF by going to a larger one.
Basically, say you use the S-AFC's preprogrammed map for the z32 MAF to the stock KA MAF. The S-AFC sets the z32's 0-5v range to output along the stock KA MAF's 0-5v range. The problem is.... what do you do at the end of the range?? You can't really tune up from 5v. I'm wondering what the S-AFC does when, say, the z32 MAF is reading 4.5v, which might be equivolent to the KA reading 8v for instance, since that's what would seem to be the problem.... the way I see it (untill I can find out if it can get by that problem), you'd need to adjust the fuel curve without the built in programs in order to really use the MAF and corresponding injectors to their potential.

As for tuning, using the DIY wideband O2 would be almost as good as getting on a dyno with a wideband O2.... which is why I brought it up.

[240racer]

I plan to use the 50lb (or 550) injectors and Cobra MAF with the safc, I also plan on running on the dyno. So when I figure out the settings on the afc, I'll let you guys know. That is if somebody doesn't beat me to it. What I'm planning to start out with is the same mafs setting as I used with the stock mafs. Since the stock ecu had no problem reading the cobra mafs, then the afc shouldn't either. When I was starting this project I was actually thinking of using a MAP sensor with the afc and converting it to a mafs output to the ecu, but I never got a maps and never looked into if it would work. With turbo cars it's just better to run a maps instead of a mafs and throttle position sensor.
If somebody has a good reason why the stock mafs setting on the afc won't work, let me know.
Also, how do the infiniti, etc. mafs compare sizewise to the cobra maf? Maybe one of those could be run with 440s or something, which are super available and pretty cheap for people that aren't running much over 10psi boost.

[Foxcolt]

JWT ECU: What they do is take a stockie KA ECU (yours) multiply all the variables by the percentage difference of the injectors you tell them, adjusts the mafs remove the rev limiter blah blah and send it back to you.

Problem with it is it leaves no room for tuning. Everyone knows that a car is built and broken on tuning alone. Since every car is different how can they make a generic ECU for your specific application. Hence the reason everyone with a JWT ecu for a turbo charged car runs so rich.

The greddy emanage has a lot more points to change fuel. However just like the AFC it's limited to plus or minus 50%. Now what they don't do is adjust timing maps and that's where power can easily be made.

What Ace is saying about the %50 limiting the overall changes you can make is completly correct and the number one reason why most people shy away from piggy back systems. However if he can make his baffle project run well with 50lbs's on and tune with the afc he's good to go. Ultimitly that's what everyone with a JWT does. They get a piggy back system to further tune.

Rant mode off:D

[DarkRaptor42]

Im gonna throw a tangent in here, exactly how many tunning points does the greddy emanage have? Its a little more than apexi's safc's but I figured it had more too it. No one has really said that they have used it and greddys site is pretty unexplanitory on it. So I pose this question as I too plan on using the cobra MAF and 50#ers, greddy emanage or SAFC?

stupid raiders....

[Foxcolt]

Originally posted by DarkRaptor42
Im gonna throw a tangent in here, exactly how many tunning points does the greddy emanage have? Its a little more than apexi's safc's but I figured it had more too it. No one has really said that they have used it and greddys site is pretty unexplanitory on it. So I pose this question as I too plan on using the cobra MAF and 50#ers, greddy emanage or SAFC?

stupid raiders....

I'd say emanage all the way. Once you get the harnesses software and cable you'll have a pretty powerfull tool on your hands. But remember your still gonna be limited by that 50 percent tuning factor.

So for example you have 270's right now right? Lets say you upgrade to 550's. First thing you have to do is find the percentage difference between the two. Then your gonna have to up everything on the fuel table by that percent. What you have left is what you can tune with. With a big jump to 50lbs you not gonna have much.

And I belive the emanage has 16 points where fuel can be added or subtracted but don't quote me on that.

[DuffMan]

Originally posted by AceInHole
The problem is.... what do you do at the end of the range?? You can't really tune up from 5v. I'm wondering what the S-AFC does when, say, the z32 MAF is reading 4.5v, which might be equivolent to the KA reading 8v for instance, since that's what would seem to be the problem.... the way I see it (untill I can find out if it can get by that problem), you'd need to adjust the fuel curve without the built in programs in order to really use the MAF and corresponding injectors to their potential.
.

What do you mean the AFC is set up for stock injectors. It's not setup for any injectors. I was assuming you'd be running bigger injectors, since this thing started out with a cobra mafs/bigger injector combo. My point is with an extra 300 bucks you can tune it perfectly, up to 1 bar of boost and maybe more.

Because you are correcting for the bigger injectors, the voltage to the ecu doesnt max out.

The AFC doesnt go voltage => corrected voltage.

It goes voltage =>airflow x correction factor => corrected voltage.

If the stock MAFS maxes out before the stock inectors do (which i kind of doubt) then maybe there is a small amount of headroom you need in injector size but for the most part its not an issue.

[Grandpa]

emanage does have 16x16 maps, the same as the stock ECU.

[240racer]

The stock mafs is good for calculated 250rwhp from my trap speed of 104mph. I was getting 76% max airflow on the afc on those runs. I don't know if the stock mafs will go to 100% though, but I do know it isn't maxed out. I did have 370 injectors running without correction on the high end to keep it plenty rich.

Duffman has is right as far as the afc and voltage correction goes. All the afc does is adjust voltage according to the settings you make, it doesn't care what kind of maf you run as long as it knows what voltage range to output with.

[DuffMan]

The 89-90 MAFS is different than the other 240sx one. It might have a higher maximum since it is the same one that is used on the SR20DET.

[DarkRaptor42]

Isnt the KA24E MAF smaller than the KA24DE MAF though? I still dont see the problem with running the Cobra Maf on the Stock ECU with the adjustments. From what I understood it works with a bit of tunning right? So why not use it, or is everyone endorsing it just pointing out the things that need to be accounted for.

[AceInHole]

Originally posted by DuffMan
What do you mean the AFC is set up for stock injectors. It's not setup for any injectors. I was assuming you'd be running bigger injectors, since this thing started out with a cobra mafs/bigger injector combo. My point is with an extra 300 bucks you can tune it perfectly, up to 1 bar of boost and maybe more.
Using the AFC's pre-programmed settings would cause a z32 MAF, or any other MAF which it already has a program for, "act" like a stock KA MAF, AFAIK. Simply put: if you're using a z32 MAF and setting the AFC to recognize it and output to the KA MAF settings, you're basically using the fuel curve for the stock injectors, size and all.
Thus you CAN use the 50% increase to control injectors from the stock injector size.... BUT, 50# injectors are about 94% larger (525cc/270cc = 1.94). Even with 370cc injectors, which are 37% larger, you'd have to allow some 37% increase over the stock MAF, and I'm not exactly sure if you can go any percent over the MAF's max voltage. Like I said though.... I'm not sure what the AFC does when it goes beyond the stock MAF's range.

Because you are correcting for the bigger injectors, the voltage to the ecu doesnt max out. But... what happens when the MAF maxes out?? I'm pretty sure using the AFC's pre-programmed settings will basically follow the stock MAF's range, not the range of the new MAF you're adapting, unless you specify your OWN settings, not using the AFC's preprogrammed settings.

The AFC doesnt go voltage => corrected voltage.

It goes voltage =>airflow x correction factor => corrected voltage.

Yes, but the preprogrammed settings have to have some correction factor to bring the new MAF to the stock MAFs voltage. In the case of using a larger MAF than stock, you're correction factor is going to be positive, so when you're at the stock MAF's 5v equivolent on the new MAF, what correction factor will the AFC use for any more airflow?

If the stock MAFS maxes out before the stock inectors do (which i kind of doubt) then maybe there is a small amount of headroom you need in injector size but for the most part its not an issue.
The stock MAFS maxes out a bit after the injectors.... it should be good for about 6psi of boost, or so I'm told, based off of an S14 KA MAF voltage to airflow chart.

[Bernard]

............

[some guy]

What about using the SR's MAF for SR injectors? Would this work for the CA also? (without AFC)

[240racer]

Originally posted by DuffMan
The 89-90 MAFS is different than the other 240sx one. It might have a higher maximum since it is the same one that is used on the SR20DET.

I'm using a '91 MAF.

also, I have no plans of using preprogrammed afc settings with a different maf. I plan on letting the fact that the cobra maf and the 550 injectors almost work with the stock ecu take care of getting close. Then I'll use the afc to slightly modify the maf output telling it that it's the stock maf. I'll be tuning on the dyno. Does anybody have any reasons why they think that won't work.

Also, darkrapter, I plan on using the setups we are mostly just discussing the aspects of the setup so we all get it right and don't blow up our motors again.

[Jeff240sx]

I also plan on goin with this setup. As soon as my engine is finished, installed, and broken in with 1,000 miles, I'm strapping to a dyno and hooking up the Cobra MAF, 50# injectors, and the AFC. Gonna try to make it work at 14-16 psi, too.
-Jeff

[DarkRaptor42]

Ok so we got three people going with this setup: Jeff, 240racer, and I. So you two will be using the AFC, im thinking of the greddy, but Im also thinking I might just follow you guys and we can all three share our ideas on the setup. What do you guys think, should I embark on my own with the Emanage or should I go with the AFC and we can all bounce ideas off each other? Or will the tuning be similar enough with the Greddy to the SFAC?

[240racer]

I'm running the SAFC and Jeff is planning on running the SAFC II in case that makes any difference to you. We will definatly be bouncing ideas of each other and if you want to join in that would be cool. I think for the price I would get the SAFC II right now since it's pretty cheap.

[Jeff240sx]

I think that using the same settings, assuming basically the same turbo setup is fine. Jim Wolf does it with the cookie-cutter ecu programs, so for his Cobra MAF, 50# injector program, it is the same, whether you have exhaust, cams, t3 vs. t04e, or even 6psi vs. 18psi. I don't see why running someone else's S-AFC setup is bad. If you're knowledgeable, you would only need to do dyno pulls to figure out the settings. Start with an approximate horsepower level, and adjust for fuel. Make less power, use the Brake Specific Fuel Consumption formula, and adjust the S-AFC accordingly.
The only problem with this is that there is a baseline tuning level for this project, so one person would have to go to the dyno for $350 worth of tuning. This leaves one person paying for others to not.
Just my thoughts.
-Jeff

[DuffMan]

Ace, i think you are getting mixed up in the math here.

The 50% correction is for AIRFLOW not for fuel. That means you can run twice as big injectors. The maximum on a stock KA ecu is 540cc, so it would work with a 50 # set up.

You see, .5 (airflow) X 2(injectors) = 1 (proper fuel)

Also if the injectors max out before the mafs does, than it is imposible for the ecu to see 5v, unless your injectors are already maxed out, because the ecu is assuming stock injectors and mafs. It could never happen, it's just physicly not possible.

240racer, it's not that using a cobra mafs, stock ecu, and s-afc wouldn't work, it's that it's pointless. A mafs that that it has a program for will match up the curve. Because the s-afc is not a complete tuning solution (only so many rpm points and 2 throttle points) a Z32 or Q45 mafs would be more driveable.

[DuffMan]

Originally posted by Jeff240sx
The only problem with this is that there is a baseline tuning level for this project, so one person would have to go to the dyno for $350 worth of tuning. This leaves one person paying for others to not.
Just my thoughts.
-Jeff

Or you could get a Z32/Q45/GS400/ect. mafs and have a baseline already. If you guys don't believe me on this ask asad.

[Jeff240sx]

A z32 maf is also pointless at higher boost, according to JWT. They said that the z32 MAF will max out at 12-14 psi. The Cobra maf is good to 500hp or so.
And by having a maf that is 2x bigger, the cooling on the sensor would be 1/2 as much. If it's reading 1/2 the voltage, it'll dump 1/2 the fuel from the injectors. Assuming the injectors are 2x larger, it would dump the stock ammount of fuel (actually, a little more, cuz it's not the exact ratio). This doesn't benefit you untill higher boost, when the airflow is above 2.5v in the cobra maf. When that happens, the ecu will open the injectors more than the stock 270cc ever could, allowing for more power.
Why would the z32 be better? Also, a cobra maf is cheaper.
-Jeff

[DarkRaptor42]

I know I dont have the evidence to back it up but this is what I was thinking about and the earlier post of the cobra maf kinda backs it up (at least in my head). So here I go:

Why didnt anyone think of the cobra MAF and bigger injectors before. This hit me when I was talking to my girlfriend last night, she was talking about somthing that I didnt really care about and I zoned out. In my haze I was thinkning about the autometer temperature sender and the stock sender off of the KA. The autometer one doesnt work, its like trying to stick a square peg in a round hole, so I went to go see if I could find an adapter. None of the auto parts stores had such a thing and they all told me the same thing, a thermometer is a thermometer dispite the difference in size. This just got me thinking. The post about the Cobra MAF and how the ford computer interprets it an calibrates with the injector size for that, then someone said that the MAFs are made by the same company, hitachi. So as I thought about it and isnt a MAF, a MAF? Why would one calibrate any differently than another especially if made by the same company. Mass produced parts arent exactly made to be special. Now this is all speculation but there is proof, Asad made the stock ECU work with the setup. Now could someone explain to me this, couldnt you take the Cobra MAF then and drop it with stock injectors and have it work? That would tell if my assumption is right wouldnt it? Has anyone done that? Cause if they have theres proof that a MAF is a MAF and the benefit of the cobra MAF is a bigger hole for an incresed air flow. Maybe im just lost on all of this but Im doing my hardest to contribute and learn, so someone slap me or tell me im right, cause I think thats what duffman was trying to say too.

[Jeff240sx]

Duffman is saying use a MAF that is already calibrated for the AFC.
If you double the cross-sectional area in a cylinder, then the airflow wouldn't fill the same ammount of the cylinder. Thus, the MAF sensor element wouldn't cool as fast, sending out a lower voltage (about 1/2 of previous) signal to the ecu. The ecu will interpret the lower voltage signal to dump less fuel. That's good if your injectors are 2x bigger, but not good on the stock injectors. At 5v, the 270cc injectors will dump near 270cc. At 2.5v (all the ecu would recieve from a MAF 2x larger), it will only dump about 135cc at wide open throttle. That would suck tremendously.
-Jeff

[DarkRaptor42]

So I was wront and tried to go off on a tangent there. But Im still right though, a MAF is just a MAF, as far as the electronics go right? The size makes a difference but the rest is the same. Cool.

[Jeff240sx]

I'd disagree on the maf is a maf theory. Why would the afc have controls for a z32 maf, if they're all the same?
-Jeff

[DuffMan]

The elements arent all the same, and different elements produce different voltage/airflow curves. The curves aren't linear so accounting for a different mafs cant be done by simply increasing fuel. In asad's case it worked enough for the car to run, with no boost. Actually a lot of people have done this, and got a car ti run but not well.

Increasing the cross section of the mafs like ace did IS linear, so that will work at least to a certain point. Don't have a lot of tuning flexability there though.

I don't know how much a cobra mafs cost, but used Z32 ones go for like 50 bucks. 12-14psi sounds low, i would say more like 20psi on a KA. For JWT they are completely programming the ecu so they can pretty much use whatever they want and compinsate for it. A Q45 or GS400 one might go higher, and those are cheap too.

An SAFC isn't as perfect a solution when using a cobra mafs. Here's an example. Because of the different curves, the correction factor at 3psi could be different than the correction factor at 10psi. The problem is the S-AFC doesn't know psi. It knows throttle and rpm. But at x rpm, you could be making different amounts boost especially if you plan on running a boost controller. Even if you tune for a constant boost level, transient responce will be off.

With a "known" mafs, the safc automaticly does the correction factor for the mafs at any amount of airflow. The only thing you need to adjust for is the bigger injectors (which is constant), and then do some fine tuning.

[Foxcolt]

Originally posted by Jeff240sx
A z32 maf is also pointless at higher boost, according to JWT. They said that the z32 MAF will max out at 12-14 psi. The Cobra maf is good to 500hp or so.
And by having a maf that is 2x bigger, the cooling on the sensor
-Jeff

That's utter BS. One of the many reasons why I don't like JWT. You'll be hard press to max out a z32 mafs at 600hp. Ask the 300zx guys if they ever have to upgrade.

[Jeff240sx]

Originally posted by DuffMan

I don't know how much a cobra mafs cost, but used Z32 ones go for like 50 bucks.
They go for how much?
Oh. $227.50:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2400932683&category=33621
Also.. most people here and on FA that sell them get $120+ for the z32 maf.
The Cobra maf from carparts.com is $127

Also, the ecu doesn't know boost either. I don't see how that scenario would be any different. If you got an aftermarket engine management unit, with a MAP sensor, then you could account for boost.
You could change the fuel map according to the voltage readout, and have a functional fuel curve for, say, 14psi. Then on the "low boost" setting on the afc, say wastegate regulated boost at 6.5psi, you'll have a completely different fuel map corresponding to the voltage readout.
What's the problem here? 2 boost settings, 2 tuned fuel maps.
I haven't done much research on this... so if I'm wrong, correct me.
-Jeff

[DuffMan]

The ecu can see the difference in boost because it would see different air flow. The airflow values would be corrected by the safc. With the cobra mafs, you would have to guess and manually correct it, but it wouldnt be correct for all airflows at the rpm you specificed.

Z32 mafs, on car-part.com there are 115 places selling them for under $100 and 15 places selling it for $50 or under.

[AceInHole]

Originally posted by DuffMan
Or you could get a Z32/Q45/GS400/ect. mafs and have a baseline already. If you guys don't believe me on this ask asad.

True... but in theory that's about as good as my MAF setup. The correction factor is adjusted by the bypass. So... really what these guys should do is just run a MAF bypass and not "waste" money on an AFC altogether :p

[Jeff240sx]

Originally posted by Foxcolt
That's utter BS. One of the many reasons why I don't like JWT. You'll be hard press to max out a z32 mafs at 600hp. Ask the 300zx guys if they ever have to upgrade.

Yup. You're right. It is hard to max out two (2) z32 mafs at 600hp. But you can max out one at ~350hp. That should equate to 14-16psi. z32 maf is 1.5x the size of the KA maf, so should handle 1.5 times the power the KA maf does. KA can handle 250-ish, so the z32 should handle 375 (well.. thats closer to 18psi). The Cobra maf is 2x the size, so should handle ~500hp
-Jeff

[DuffMan]

Originally posted by AceInHole
True... but in theory that's about as good as my MAF setup. The correction factor is adjusted by the bypass. So... really what these guys should do is just run a MAF bypass and not "waste" money on an AFC altogether :p

They could, but if it was me i'd want a way to tune it.

[Foxcolt]

Originally posted by Jeff240sx
Yup. You're right. It is hard to max out two (2) z32 mafs at 600hp. But you can max out one at ~350hp. That should equate to 14-16psi. z32 maf is 1.5x the size of the KA maf, so should handle 1.5 times the power the KA maf does. KA can handle 250-ish, so the z32 should handle 375 (well.. thats closer to 18psi). The Cobra maf is 2x the size, so should handle ~500hp
-Jeff

Maybe, however I have seen/heard of sr's running that amount of hp using z32 mafs. I've never heard of one conking out at 350hp.

And it's not the size of the mafs that amounts to what hp it can make it the range of which the sensor can dedect amounts of air flowing through. The size makes the mafs less restrictive that's all.

[240racer]

And it's not the size of the mafs that amounts to what hp it can make it the range of which the sensor can dedect amounts of air flowing through. The size makes the mafs less restrictive that's all.

That's true, but unfortuantly we don't really know where that is for each mafs so we assume that the size is relative to the amount of air it can measure and go from there.

Everybody is making good points in all they are saying about the AFC, it is not the best tuning tool available. However, I don't think that the preprogrammed maf settings are that much, if any, better then running the car on the dyno and tuning it yourself. Driveability is sacrificed when you run the SAFC. I think the emanage and SAFCII are going to be better, but I don't have much info on them. I'm not worried about driveability too much for now, I'd rather have power and then work on smoothing it out later. I'll just make sure I'm on the rich side. If driveability is a large concern and you want to make power, then a stand alone is in order and a person that is good at tuning is important. Both of the people that had my SAFC before I did now have AEM EMS. They "grew up" so to speak. Also, they are lucky because AEM makes a PNP version for their cars, but one of them isn't using it because he was ancy and got one before the real version came out. If I decide to stick with the 240 for a while, in other words, if I'm in it for the long haul, then I'll be going AEM too (or something similar)

Also, the ecu doesn't know boost either. I don't see how that scenario would be any different. If you got an aftermarket engine management unit, with a MAP sensor, then you could account for boost.

You are correct, in fact you would just have your map be dependent on MAP and RPM and you wouldn't worry about throtle position. Every performance turbo car is set up that way. They don't even have MAFS. In fact the SAFC has an input for MAP sensor and I was thinking of doing it that way, and it's still not out of the question. If this cobra/550 plan doesn't work like I think it will, then I'll probably look into that more. My friends with AEM aren't running a maf anymore. On our FSAE race car (yamaha R6 engine) with MoTec we didn't run a maf and it was NA, there was load (throttle position) and RPM and a map sensor.

[DarkRaptor42]

How would you even go about getting a MAP sensor to work with a 240? I have 4 of them lying around at my GF's house (honda crx) but I dont see how they could adapted. Enlighten the Raptor to the MAP theroy.

[240racer]

Ok so far it looks like running the map instead of the maf is a dead end, unless it's with standalone. However, there is still a benifit of running a MAP on a turbo 240. The SAFC has two TP settings, different fuel maps for different throttle positions. However, with a turbo car, manifold pressure is more important then throttle position. So instead of running the two maps on TP, you run them with the MAP. So you can have a high boost, like over 1 atm abs. and a low boost, less then atmospheric, or something like that. Instead of having the maps switch at a certain throttle position they switch at a certain manifold pressure. This is a better turbo setup, and actually better then the JWT, since we are sensing boost and it's not. Sorry, couldn't help the dis, I'll try not to let it slip again.

[240racer]

Originally posted by DuffMan
The elements arent all the same, and different elements produce different voltage/airflow curves. The curves aren't linear so accounting for a different mafs cant be done by simply increasing fuel. In asad's case it worked enough for the car to run, with no boost. Actually a lot of people have done this, and got a car ti run but not well.

Increasing the cross section of the mafs like ace did IS linear, so that will work at least to a certain point. Don't have a lot of tuning flexability there though.

I don't know how much a cobra mafs cost, but used Z32 ones go for like 50 bucks. 12-14psi sounds low, i would say more like 20psi on a KA. For JWT they are completely programming the ecu so they can pretty much use whatever they want and compinsate for it. A Q45 or GS400 one might go higher, and those are cheap too.

An SAFC isn't as perfect a solution when using a cobra mafs. Here's an example. Because of the different curves, the correction factor at 3psi could be different than the correction factor at 10psi. The problem is the S-AFC doesn't know psi. It knows throttle and rpm. But at x rpm, you could be making different amounts boost especially if you plan on running a boost controller. Even if you tune for a constant boost level, transient responce will be off.

With a "known" mafs, the safc automaticly does the correction factor for the mafs at any amount of airflow. The only thing you need to adjust for is the bigger injectors (which is constant), and then do some fine tuning.

Ok, after reading the SAFC manual again, I figured out where you are coming from and why it won't work for us in this case. If you were going to run stock injectors and change MAFS, then you are absolutly correct. You could run the Q45 mafs which apexi labels as a HW-1 type (Hot wire) and set the IN to hw-1 and set the OUT to HW-5 which is what the KA24DE is. then it would work just fine. However, if you want to run larger injectors, then it won't work. The ecu will still be getting a "stock" signal from the afc. What we need is to lie to the AFC and tell it that we are using the stock MAF and stock injectors, but in reality we are using injectors that inject twice as much fuel for a given pulse width and a MAFS that outputs half the voltage signal for a given amount of air. That way the afc is really not even being used, except for minor adjustments in which case it lies to the Stock ECU.

[DarkRaptor42]

well ya, youd just keep the AFC at stock settings since it works and tweak it, hasnt that been what weve been planning to do the whole time? Because the 50# injectors and the larger maf are nearly double stock together so they work together right? So we just tune it from stock settings or did I miss out on somthing yet agian.

[240racer]

no you didn't miss anything that's still the plan. I'm going to try to use a MAP sensor instead of a TP sensor though. That should help the tuning some under boost. Especially part throttle boost.

[DuffMan]

you WANT the ecu to see the "stock" value from the mafs. If you are running bigger injectors (say 370 for example) you set the airflow at a decrease of 27% at all rpm points and then tune from there.

The ecu sees what it would see with a stock mafs less 27% of the air, which works out into a proper mixture with the bigger injectors.

[DarkRaptor42]

thats what I figured was going on. I might just stick with the emanage though, for that all you have to do is plug in the bigger injectors and it self accomodates for them. Sweeeetttt...

[Bernard]

.........................

[240racer]

Originally posted by DuffMan
you WANT the ecu to see the "stock" value from the mafs. If you are running bigger injectors (say 370 for example) you set the airflow at a decrease of 27% at all rpm points and then tune from there.

The ecu sees what it would see with a stock mafs less 27% of the air, which works out into a proper mixture with the bigger injectors.

If I am running 550 injectors then my initial setting on the AFC is more then 50% (out of range) so I can't use that system on anything larger then 370 injectors. BTW, the setup you metioned is what I have right now, and the correction is 37%. With 550 injectors the correction is 103% way out of range for the afc, so we have to fool the afc as well and give it less voltage per airflow as well as then telling the ecu whatever we need to to tune it properly for good AFRs under boost.

Update on the setup I am going to run a MAPS to tell the AFC whether it should be in high or low mode. Usually they use TP for this, but MAP is better for turbo cars.

[DuffMan]

Originally posted by 240racer
If I am running 550 injectors then my initial setting on the AFC is more then 50% (out of range) so I can't use that system on anything larger then 370 injectors. BTW, the setup you metioned is what I have right now, and the correction is 37%. With 550 injectors the correction is 103% way out of range for the afc, so we have to fool the afc as well and give it less voltage per airflow as well as then telling the ecu whatever we need to to tune it properly for good AFRs under boost.

Update on the setup I am going to run a MAPS to tell the AFC whether it should be in high or low mode. Usually they use TP for this, but MAP is better for turbo cars.

We already went over this above. The limit is not a 50% increase in fuel. The SAFC does not effect fuel directly. It effects airflow readings. 50% decrease in airflow equates to a 100% increase in fuel. That is the limit of the SAFC,

[240racer]

Even if that is true, we are still at the limit of the AFC and it does no good for us, we need to get closer to the middle to have any room to tune.

[DuffMan]

So you would run 3% rich. The greddy e-manage is good though and almost as cheap. It depends what you're looking for really.

The safc - simple easy to use, gives you some feed back while driving.

E manage - more complicated but more powerfull. Not as much feedback when driving.

[240racer]

I am thinking you may be right "but I'm just not sure about that right now" (lumbergh- office space) I was doing some calcs and I see where you come up with the 27% now, and I think that's correct it's just different then what I have been doing for a while now and I am not going to just jump on ideas when they sound good (sorry)

[240racer]

Originally posted by DuffMan
So you would run 3% rich.


yeah I guess that wouldn't be bad to be only that rich at the worst. I still don't see the reason to not fool the afc and run a different mafs

[DarkRaptor42]

what calculation did you do and why wont there be any room to adjust for boost?

[240racer]

I was wrong about not having room for boost, and edited my post, sorry

[240racer]

the calcs I did are not really following any set forumla or anything, I just used math to figure out what numbers are correct instead of talking about it, but you can't explain it with out talking through it and it's kinda a pain.
basically, if you adjust the AFC -27% it will tell the injectors to inject 27% less fuel which is just right for the 370s setup. since the 270s are 73% of the 370s
and if you adjust it to -50% then it will tell the injectors to inject 50% less fuel which is about right for the 550s setup. Since the 270s are 49% of the 550s

basically before I was doing [new inj]/[original ing] and that's wrong

now I am doing [orig ing]/[new inj] and DuffMan thinks that is correct and I'm coming around.