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Old 07-27-2008, 06:56 PM   #1
TurboQueef
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Default I am maxing out MAS with my FP Red, need advice

Hi,

Sorry if this info is somewhere on the net ... I did try to search for a couple of weeks now...

I am at the point where I need to address the limitations of the stock ECU & mass air sensor.

I am running an FP Red with Axis engine... I am happy with results to date on pump fuel.. I got 380 AWHP and a 12.29 @ 115 (wimpy launch) out of it so far with 22.5 PSI of boost.

My MAS voltages are up to 4.94 with the 22.5 PSI.

I am running the stock ECU, APS 70mm intake and APS DR 725 FMIC. Tuning with RomRaider & StreetTUNER

I don't really want to change the ECU or run a piggyback system. I have been looking into speed density or moving the MAS to the cold side of the APS FMIC pipe.

I also wonder if there is any kind of electronics that would manipulate the MAS sensor signal to give it more headroom.

My goal is to run 28PSI with race fuel... my only hold back at the moment is the MAS.

My specific questions:

** Has anyone heard of any electronics that can manipulate the MAS sensor to get around the problem (5v max)? If so, please provide details!

** Does anyone know of any off the shelf intake that is larger than 70mm? How about an off the shelf TMIC cold side pipe that has the sensor mount installed to a larger section of piping (75 ~ 85mm)?

** Does anyone have any other ideas for correcting the problem (besides stand alone or piggyback ECU or re-locating the MAS to larger pipe)

Thanks a bunch...

Jeff B
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Old 07-27-2008, 08:46 PM   #2
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I read in a thread somewhere that when you run out of MAF all you do is increase the diameter of the pipe it is in - then scale everything. You lose some resolution, but you gain more headroom.

I'm sure someone who knows will correct me if I am wrong.

Check out the engine tuning section - particularly the "open source tuning" section
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Old 07-27-2008, 08:53 PM   #3
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Quote:
Originally Posted by wrxsti.l View Post
I read in a thread somewhere that when you run out of MAF all you do is increase the diameter of the pipe it is in - then scale everything. You lose some resolution, but you gain more headroom.

I'm sure someone who knows will correct me if I am wrong.

Check out the engine tuning section - particularly the "open source tuning" section
Thanks for the reply.. that is one of my options but I was hoping for something a bit easier (I can't find any leads for a larger intake, seems that 70mm is largest). Seems like there should be some electronic solution (other than piggyback or stand alone ECU)

Thanks again...
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Old 07-27-2008, 10:07 PM   #4
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http://pandlmotorsports.com/osCommer...roducts_id=352

3" = 76.4mm. good for almost anything you can throw at it.
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Old 07-27-2008, 10:22 PM   #5
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Quote:
Originally Posted by TurboQueef View Post
Thanks for the reply.. that is one of my options but I was hoping for something a bit easier (I can't find any leads for a larger intake, seems that 70mm is largest).
Any good machine shop should be able to fab you something up to whatever measurements for a few dollars without much hassle.

Saying that, there is always the "mega maf" option from KS Technology HERE or the 76mm MAF intake from Zerosports HERE.

After those options, there is the Z32 MAF (80mm) but I am unsure how to get this to work without an aftermarket or piggyback ECU upgrade.
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Old 07-28-2008, 01:22 AM   #6
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I modify stock older Legacy JECS MAFS to flow about 30plus psi. $80 plus shipping. If it doesnt work, money back. Are you suck or blow through?

ANOTHER THING!!!!!

If you are at 4.94 volts, you are out of injector! A bigger MAF will not make small injectors flow more......
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Old 07-28-2008, 01:27 AM   #7
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So what you really need is just some bigger injectors......
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Old 07-28-2008, 03:47 AM   #8
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hey my buddy has a 83mm ks tech mega maf for sale. brand new. let me know if your interested.
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Old 07-28-2008, 03:53 AM   #9
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Quote:
Originally Posted by reddevil View Post
...ANOTHER THING!!!!!

If you are at 4.94 volts, you are out of injector! A bigger MAF will not make small injectors flow more......
Thanks... I want to understand a bit more about this statement... my understanding is there is no relationship between maxed out injectors and the amount of air mass the MAS is detecting. How would maxed out injectors influence the voltage offered by the MAS?

Thanks
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Old 07-28-2008, 04:00 AM   #10
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Quote:
Originally Posted by hettchen View Post
hey my buddy has a 83mm ks tech mega maf for sale. brand new. let me know if your interested.
Thank you.. I would like to keep CAI but will keep this in mind!
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Old 07-28-2008, 11:16 AM   #11
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"In General", the ECU will be flowing the injectors from minimum to maximum, as the MAF signal goes from minimum to maximum. This is making the assumption the injectors are in scale to the MAF AND THE TUNE!!! So there is no way for the injetors to flow more than 100% by the time the MAF hits 5 volts.

Now if you put in larger injectors, you need to change the tune to accomadate them. And in doing so the MAF signal is interpreted differently and is actually decreased (not physically, but by the tune) and you can make more power. This is also true with the race gas, as it kind of acts as "bigger injectors" because you actually flow less gas to make the same power (SOMETIMES).

But back to your original question, the MAF.

If you were to simply increase the MAF size, your current injectors would max out BEFORE the MAF hits 4.94.

So see the correlation? Anyway, bigger injectors with bigger MAF with a new tune is the way to go.
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Old 07-28-2008, 12:12 PM   #12
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Quote:
Originally Posted by reddevil View Post
"In General", the ECU will be flowing the injectors from minimum to maximum, as the MAF signal goes from minimum to maximum. This is making the assumption the injectors are in scale to the MAF AND THE TUNE!!! So there is no way for the injetors to flow more than 100% by the time the MAF hits 5 volts.

Now if you put in larger injectors, you need to change the tune to accomadate them. And in doing so the MAF signal is interpreted differently and is actually decreased (not physically, but by the tune) and you can make more power. This is also true with the race gas, as it kind of acts as "bigger injectors" because you actually flow less gas to make the same power (SOMETIMES).

But back to your original question, the MAF.

If you were to simply increase the MAF size, your current injectors would max out BEFORE the MAF hits 4.94.

So see the correlation? Anyway, bigger injectors with bigger MAF with a new tune is the way to go.
I don't follow what you're saying. If what you say is correct then one would never have to get a bigger maf just bigger injectors. There is more than one way to scale injectors and I think the way you describe above is by scaling the MAF to match the injectors which isn't necessarily the preferred method.
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Old 07-28-2008, 12:53 PM   #13
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Yes, one can just get bigger injectors. And it works.

But how well?

Lets just say its best to match injector size to MAF versus overblowing the injector size to make a "small" maf work.
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Old 07-28-2008, 02:13 PM   #14
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I see no point in trying to scale the injectors to the MAF physically instead of just using the injector scaler. You need a MAF housing that will not max out at the planned air volume. You also need injectors that will be able to provide enough fuel for that air. Obviously going too small with either is bad. Going too big will give you driveability and tuning problems. However, there is no direct relationship between them that you need to worry about.

If there was, Subaru would have included a larger MAF housing on the 2.5 vs the 2.0 and kept the same injector scaler. In fact, there would be no reason for an injector scaler in the ECU...
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Old 07-28-2008, 06:07 PM   #15
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Either way youre going to have to rescale/retune. So id be inclined to go blow through as then you can also use the MAF for charge temp too
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Old 07-28-2008, 06:13 PM   #16
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Quote:
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Either way youre going to have to rescale/retune. So id be inclined to go blow through as then you can also use the MAF for charge temp too
I'm one of the few blow through guys.... I also reccomend it. Initial tuning is a bit annoying but its worth it in the end... drivability with a BOV is so nice too...
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Old 07-28-2008, 08:18 PM   #17
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KS-Tech has both shortram and CAI MegaMAF's in a couple of sizes to suit your setup
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Old 07-28-2008, 08:25 PM   #18
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at 380whp there should be no way that you should max out the maf
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Old 07-28-2008, 08:29 PM   #19
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Originally Posted by Turbo_Mike View Post
I'm one of the few blow through guys.... I also reccomend it. Initial tuning is a bit annoying but its worth it in the end... drivability with a BOV is so nice too...
Hi Mike.. thanks for the comment... What size blow through do you have?

Also, did you tune the blow through yourself? If so, can you give me a very high level comparison to tuning a 70mm. I tuned my APS 70mm and I wonder what key tuning challenges I will face with the blow through as compared to the 70mm.

Finally, do you consider your set up a daily driver? I don't want to deal with stalling at stop lights etc.

Thanks a bunch

Jeff B
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Old 07-28-2008, 08:35 PM   #20
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Originally Posted by novacivic View Post
at 380whp there should be no way that you should max out the maf
Don't know what to say... my datalog says 4.92 V on a cool day running 22.5psi on 93 octane... ran 12.29 (with mega pu$$y launch) @ 115
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Old 07-28-2008, 08:37 PM   #21
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Originally Posted by brcewane View Post
KS-Tech has both shortram and CAI MegaMAF's in a couple of sizes to suit your setup
Thanks for the lead.. I have been e-mailing them regarding the MegaMAF's and a prototype blow through they are working on!
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Old 07-28-2008, 08:45 PM   #22
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Quote:
Originally Posted by reddevil View Post
Yes, one can just get bigger injectors. And it works.

But how well?

Lets just say its best to match injector size to MAF versus overblowing the injector size to make a "small" maf work.
Hi reddevil,

Thanks for the info... but I am still confused... because my understanding is that when the MAS hits its limit of 5 volts.. no matter what you do the ECU is not going to understand that more air is going through the engine therefore it will not respond by offering increased injector pulsing which would result in more fuel delivery to each cylinder. Am I still missing something?
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Old 07-28-2008, 09:56 PM   #23
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When you oversize the injector size versus MAF signal/stock injector size, you need to pull/tune the MAF signal down because otherwise you would be giving too much fuel. ie, if the stock 550 injector gives X amount of fuel at Y signal, a 850 cc injector would give 50% more fuel at Y signal, therefore the Y signal would be interrupted and modified to read smaller, so smaller amount of fuel would be givein.

Now this can be done several ways, of which the "easiest" is to set you injector settings to whatever size injector you choose to run. However, I am not fluent in that area. But get the concept now?
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Old 07-28-2008, 10:39 PM   #24
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Quote:
Originally Posted by reddevil View Post
When you oversize the injector size versus MAF signal/stock injector size, you need to pull/tune the MAF signal down because otherwise you would be giving too much fuel. ie, if the stock 550 injector gives X amount of fuel at Y signal, a 850 cc injector would give 50% more fuel at Y signal, therefore the Y signal would be interrupted and modified to read smaller, so smaller amount of fuel would be givein.

Now this can be done several ways, of which the "easiest" is to set you injector settings to whatever size injector you choose to run. However, I am not fluent in that area. But get the concept now?
That's the way its done by the majority of tuners out there and the reason there is a fueling map that gets modified when tuning a car. Tuning the MAF to compensate for the injector is the older, more ghetto way of tuning and the way most piggyback add on computers get around the fueling thing.

The issue still remains that if the raw MAF voltage is maxed out the only way to get more range out of it is to move to a bigger diameter pipe.

EDIT: also with properly scaled MAF and injector values you can change one with out having any effect on the other. What are you tuning with Reddevil?
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Old 07-28-2008, 11:23 PM   #25
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haha, I am tuning with a PP6. I have to modify the MAF signal to accomadate the injector size.

But I think the concept is there, you need to TUNE the MAF to the injector size. It doesnt matter HOW you do it, it is the END RESULT that matters.
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