I just want to try to learn this stuff and get familiar with a lot of the tables that are in these Bin files. Any explination or help would be very usefull.

I'm using Tunercat with a 6E.tdf and a stock '89 TPI 350 Bin. Amongst many of the tables that are editable are these tables titled "Mass Air Flow 1-5". On the left of the table is "Counts" and on the right is "gm/Sec". The counts go from 0 to 1536 using all five tables consecutively. Obvioulsy gm/Sec is the ammount of air that is flowing, but what are the counts refering to?? Is this basically a conversion that the ECM uses to know how much air is coming in? So for example... If the gm/sec=22.2 and the counts=512 on the table, then the ECM knows that 512 is equal to 22.2gm/sec of air? Wait a sec... I think I just figured my way through this one! Well why would anyone want to change these values then??? It just seems like they would always be a constant. So many gms/sec equals so many counts. The only use I can think of to change these values is if your eninge is consuming more air than the max count of the MAF can register. Then all you would do is rescale the counts to a higher gm/sec at max count?? Am I making any sense?? Does somebody have a good understanding of this that can explain it concisely.

Thanks for the help

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Tom Milmont
'89 Formula 350
13.4sec@101mph
My Page

 

Those numbers are about the flow characterists of the intake tract. Changing a air filter type slews them. Cams and the reversion they generate effect the MAFs sencing of air flow.
I change one scaler from 6 to 9 and the idle went from 600 to 1000. then one other tried 2 and got rid of an off idle sag (very minor).
If I had more of a system to work with them I'd tell ya, just I haven't gotten them dialed in yet

 

Ok, but does what I was saying apply to this at all?? Obviously they're about the flow characteristics of the intake tract. But shouldn't the MAF just adjust to the air filter change?

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Tom Milmont
'89 Formula 350
13.4sec@101mph
My Page

 

There is no need to fool with them if your block learns are in order. Real simple. If you find an area let say at idle for example, where you car in closed loop has a block learn of 114 at 10 gps flow. Since ideal would be 128, you need 11% less fuel at that air flow. Find in the MAF table where 10 gps is. Adjust those values down (to lean out) at and around 10 gps. It takes some practice. Chage a little at a time. Usually porting your MAF cause it to under report airflow.
Jason


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89 Vette 6 speed
CNC heads, crane cam, Miniram, headers
Soon to be 396 Small Block!

 

So is the key to maintain the block learn near or at 128?

Since I have the 165 ECM, I can't get this info during a WOT test (at least I can figure how how to diacom to hookup). however I can monitor the O2 sensor.

Is there a better MAF ECM out there?

MArk.

 

The best update to a 165 is just going to a 730, and MAP, IMO
What kind of BLs are you running?.
Use plug readings, O2v are just slightly better then calling the psyhic hot line all they say is >.44v is rich and less then that is leaner the 14.7

 

Grumpy,

I have tweaked my fuel pressure to get the BL right around 136 or so. At least this is where is has placed itself. I would really like to see what is happening at WOT since I have 19lb injectors on a 350. My pressure is at 55lbs (which calculates out to 22lbs/hour), however I know the fuel increase is anything but linear. I had my injectors flowed up at 50 and 55, and the increases started to drop off. 55 was about it before you started to notice the "better" injectors of the bunch.

Perhaps a wideband O2 would be a good investment ... rather than paying those psyhics.

Mark.

 

Just to jump in and ask a silly question here, but with these tables could you actually compensate for a larger MAF tube?

 

Yes, but the limit of the computer on max gm/sec is still 255, so flowing beyond that amount of air you are no longer getting an accurate(read:useful) info from the MAF.

 

Once I finish the turbo setup on my tpi, would it be; 1)Use the 165 ECM and work from there? or 2) Better to bite the bullet and change to a 730 ECM first and go from there? My realistic goals from this little project of mine is 425-450 HP. I don't need anything more, tho yes +500 HP would be interesting. Its going into a weekend cruiser with a trip to the local test and tune once in a while. I would rather not waste time on the 165 if the 730 would really benifit me at this power level. Thanks, Bob
www.turbotpi.homestead.com/SATURN5.html

[This message has been edited by SATURN5 (edited December 04, 2000).]

 

How about visiting www.syty.org and look around at all the data on the 749 ecm.
How about a calibration that uses a 2 bar MAP. And allows running 15 PSI with proper resolution

 

Thanks Max.

Now, can anyone tell me what you can do after you reach the 255 gm/sec threshold? I notice the buick guys have some potentiometer type contraption that allows something around 510 gm/sec? What does the stock system do after reaching 255 gm/sec? Thanks guys!!

 

Just uses that last entry.
A hot GN can be pegging the MAF and still run 11s. But, real easy to blow headgaskets doing that (and many do).
It's not a pot. It's a microprossor device that allows running a late LT1 MAF, and the software to run to 510 grams/sec. The LT1 MAF is the late 3.5" one. Better part of $300 for all the bits, and it'd GN specific to date.
It's called a translator.

 

Ok, so the ECU uses the last reading, but does it use the MAF info at WOT? If not you could conceivably swap out to a bigger tube, adjust the tables and then take advantage of the extra flow at WOT?? Is this feasable?? How do forced induction guys cope? I assume this is why the have the overheating problems?
After the 255 gm/sec is reached does the ECU then use other sensor reading predominantly?
Anyone know how the heck the GN translator works? The V6 MAF was digital just like the new LT1s, is there a way to convert it to an analog signal we could use?
What exactly is the program used? How is it incorporated with the stock ECU? Could something lkike this be used to swap out to a digital MAF w/o a conversion?

 

All you need to do is data log the oem mafs ouput to the ecm reported output, while also recording this other MAFs output.
Then just build a device to translate the 2nd MAFs out put to look like the first ones.
Then test it in all kinds of operating conditions.
The late MAFs are of such a different range you can't input them to the ecm.

What overheating problem do you know of for the Turbos?. I'm curious about since I own a turbo car.

 

The Buick guys system also top out at 255 GMs/sec. The way they compensate is to just program for a much richer mixture at 255gm/sec than they are trying to really get. I had the same problem years ago with my supercharged MAF IROC-Z. I didn't have the means to burn a chip. (I am going to get the stuff and start now) My engine ran fine at part throttle & all RPMs but at full throttle it ran good up to 4300 RPMs. At that point the mass air sensor was maxxed out at 255 gms/sec and it leaned out above that. The way I solved my problem was to install 36#/hr injectors, still using the stock 5.0 ltr chip. I cut the 3" air duct tube off of my MAF and epoxied a 3½" tube on. I then fine tuned the mixture by adjusting fuel pressure. My block learn numbers stay around 128 and wide open throttle mixture is good. The big injectors made a richer mixture but the modified MAF leaned out the calibration & expanded it's range. It still only has 255 units of measurement but more grams are measurable. But that was with a 305 and then 350 using a paxton with only 8 lbs boost. I am installing an intercooled procharger with around 15PSI soon and will need to make prom changes for that.

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• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo

 

Grumpy, come to think of it, they've all been supercharged. The two turbo cars I've worked on have both been GN's and the guys that owned them never told me of overheating problems. As for the supercharged cars that have had overheating problems, it's been the ones with the intercoolers in chickens/TAs/GTAs. I always assumed it was the blocking of the radiator by the intercooler, coupled with the leaner mixtures at WOT and the combustion pressures associated with forced induction. BUT I'm not too familiar with forced induction so that's only my esteemed guest... er guess. And... um... could you explain the first sentence? I'd have to data log each one consecutively and then compare? Also, The new MAFs are what the Buick guys are using right? Do it's a digital signal? Isn't there a way to translate the digital signal to an analog one that we use?

I*4ME, Well that is actually what I'm trying to do now (read: I would appreciate any help/tips). I wanted to increase the diameter of the MAF and then compensate with the 24lb. injectors (n/a not forced ind.). I wanted to hammer this out now before I go with the new motor. I'm having problems figuring out how to relate the various fuel curves and pressures of these injectors and then to relate that to different size tubes/airflow. I'm waiting for my Diacomm to come in and I think a pocket programmer is coming in Jan. I've had enough futzing with second hand numbers and mathematical calculations. I just can't do it like this, I was hoping to get it done ahead of time so I had a clue when I started futzing with the ECU, but it seems I have to dive right in.

So here is the setup I'm toying with to hammer it out...
eng ----
'89 roller blk. 350
stock bottom end
TFS TW G2 heads (out of box)
custom cam 218º/224º - .480/.480 - 112º LS
big mouth
AS&M LTR
ported plenum
24# inj.
48 TB w/ airfoil
home made cold air ind. w/ K&N
AFPR

Exh.----
Edel. coated headers
3" Catco
3" MB homemade exh. w/ flowie crossover

Even with this mild of a motor I think that the engine is being choked up top as well as leaning a bit. The 24#s suck in open loop, but are OK once in closed loop. What I'd like to do is figure out how to increase airflow in a manner which can be repeated by others (if you are going to hack your MAF might as well do it right!) and while I'm tinkering I'd rather blow this than the 383 sitting in the garage. I also have a couple manifolds that we fabricated that I'd like to try, but only after I free up the flow. This is one of those problems that have been sitting in the back of my head for a while. As I go along I pick up some parts to work on it. There is always a plan even if the wife doesn't see it!! I do realize that SD would in the long run be easier, but I do prefer the MAF setup and it is a bit more forgiving of trailing mods.

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"The people always have some champion whom they set over them and nurse into greatness... This and no other is the root from which a tyrant springs; when he first appears he is a protector.
-Plato

 

I happen to be running a GN.
Maybe that's the way you did it, but for up to about 320 HP the stock MAF is just fine.
You can push it up to 375 and still be OK, above that is when you start having resolution problems, at that stage just tuning with FP is done for WOT and then fudging the low end for drivibility is done.
The Ford MAF is an entirely different strategy with the sampler tube principal.
The run out of maf and go lean is programming issue,
To blanket say pegging the MAF forced a leanness is wrong

BTW, I've run 20 PSI on the GN without a hint of leanness or detonation with the stock maf

 

RD,

The PW MAF Translator interpretes the digital signal from a larger LT1 MAF and offsets the zero point, then re-spans the output for interpretation by the older ECMs. The maximum digital value of 255 is reached by the MAF translator output at the correct air flow point for the ECM to pulse 24-30 lb injectors at a near-factory pulse width. At WOT, the ECM and MAF don't care about intake air, since the TPS is indicating an 80% or higher opening. As long as the MAF signal to the ECM is relatively high (255 or so) the ECM will continue to deliver the maximum fuel pulse widths of 80% duty cycle. If the intake air flow happes to increase beyond 255, the ECM would never interpret it and still deliver maximum fuel.

The Translator is a relativly simple digital/digtal converter scaled for the task. (Sound like a familiar project?)

------------------
Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

[This message has been edited by Vader (edited December 12, 2000).]

 

Grumpy, perhaps I should have been more specific about my MAF adventure. At WOT the MAF could meter my air intake and supply a linear sensor output up until the engine was turning around 4300 RPM. At that point MAFs output signal was 5v. It had maxxed it's useful range. At all RPM above 4300 RPM the engine continued to draw more air at an increaseing rate. However the MAF output was already pegged at 5v. Therefore, since the ECM (with a stock PROM, injectors & FP) was metering fuel for the factory calibrated 255 gms/sec and the engine was inhaling much more air than that a lean condition ensued. This all occured in '92 and options were few. I had worked with some GNs & T-types in the late '80s and if you did enough to the intake tract (head porting, free flowing intercooler, etc.) & turned up the boost it was pretty easy to get them flowing way more than 255 gms/sec. The easiest way we had at the time for dealing with it (we used the stock MAF) was to call up a chip burner, explain our situation and they burned a PROM that just overly richend the mixture (on paper anyway) to well over 11 or 10 : 1. When installed on the car it atually only created a mixture of around 12:1. It was a crutch but it worked well and guys are still doing it that way today. However In '92 there weren't a lot of places with the same experience with forced induction TPIs. To get a "good chip" I would be sending it back & forth over & over until we got it right. That would have meant $500 up front for the first PROM, and $100 for each reburn until we got it right. That wasn't an option at the time. I needed a better (read as cheaper & faster) way out. I got a good deal (trade) on a bigger set of injecters. knowing if just installed them alone the system would be fighting a rich condition all the time. To "lean out" the calibration I "tricked" the MAF by modifying it. I reasoned that the only airflow actually measured by the MAF was that passing through the venturie in the center, and that if I changed the size ratio of the outer duct to the venturie that would alter the calibration of airflow VS voltage output for the MAF. I gave it a shot with a spare MAF and it worked. There are still only 255 units of resolution but I am now measuring more than one gram of air per unit. Max MAF voltage is still 5v. This mod cured my problem and is still working today. I would like to burn My own PROMs now that info is floating around everywhere and maximize power. It is also something interesting that I just haven't done myself yet. Also when I install a new compresser + intercooler & flow even more air, I will likely not be able to compensate the same way again. If I reduce the resolution of the MAF much more it may hurt Idle & drivability (too many grams/sec of airflow per millivolt MAF output). I will learn what I can about PROM editing starting on the 165. Also I was interested in what was mentioned about the 749 from a Typhoon/Syclone. If it can control the ancillary devices on an '86 F body I will try a swap. If it won't perhaps I can disable what I dont need in the 165 and piggyback it with the 749 letting the 749 handle the fuel metering. sounds interesting...

------------------

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo

 

Kinda brain fade in what I was seeing in several post back.
Yes, on a 165 system, I'd set WOT with fuel pressure, and then work back with and forth with the injector constants to get the drivibility vs WOT right.
There is just so much you can do without getting into the scaler MAF table stuff.
You can't just piggy back ecms. They use different pull up resistors for things, and get way outta hand, HOWEVER, running say fixed inputs to a 749 and then switching to it for a MAP system at WOT is doable.
I've thought at lenght about doing that with a GN. Trouble is the 148 is SEFI, and
would take a nest of external injector drivers to do it.

 

Allright guys, sorry to beat a dead horse but...

1. Does the ECM query the MAF sensor or does it read a constant signal?
2. Does it even look at the MAF at WOT?
3. If not, does the ECM just peg the injectors at 80% duty?
4. Can anyone try and explain in layman terms what is meant by losing resolution in modified MAF cars?

Gimpy questions I know, however you don't learn a thing without questions, right?
Thanks!

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"I don't want to be right - I just want to know if I'm right"
-Einstein

 

Answers in above text

 

The Bosch MAF can read WAY more than 255g/s intake air, it's just that the output is scaled to a maximum signal of 5V at which point the ECM can only read a maximum of 255g/S.

I keep mentioning the timing thing, but nobody but Red Devil has caught on yet. Too late, the patent search has begun...

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Question
Would it be possible to take the impedance of the MAF and put an equal load in series with it thus cutting the MAF voltage in half for a specified gm/sec count and compensate by doubleing the fuel amount in the tables? Making the ability to flow 510 gm/sec with a stock MAF