Maxing out Maf sensor

Just curious when I have to worry about maxing out my MAF? What do I do to fix it? Thanks

Mine is maxing it shortly before shiftpoint now at the current power level.

Rog

Most supercharged cars will max out the MAF pretty easy, the best way I have found to fix the problem is to tune the PE tables with a wideband. They sell something that is called a MAF Massager that is supposed to keep the MAF from maxing out but I dont have much experience on it nor have I researched it. Rich Krause told me about the PE tables and I took his word for it, he's a pretty knowledgable guy.

The MAF massager doesnt prevent the MAF from maxing out, all it does is keep the code from being triggered so you dont get a SES light.

If you have the OBDI, which you both have for 94 and 95, all you do is tune for it in the PE. You will still max out the MAF and it may throw a code, but nothing else will happen as long as you tune for it. Then just turned off the MAF code with your program. OBDII will be a different issue.

cheers

Is there an aftermarket MAF that doesnt max out? Is tuning the PE tables more of a band-aid than a fix. I would think if you are maxing out the MAF and still pushing more air it wont add the additional fuel past the max reading on the MAF

You will not max out the MAF at part throttle cruising, the only time you will max out the MAF is during full throttle high RPM driving. At WOT the PCM adds fuel according to the PE tables, during part throttle cruising and idle fuel is still added as required by the MAF and O2 sensors.

You will not max out the MAF at part throttle cruising, the only time you will max out the MAF is during full throttle high RPM driving. At WOT the PCM adds fuel according to the PE tables, during part throttle cruising and idle fuel is still added as required by the MAF and O2 sensors.

That is absolutely incorrect for WOT, The PCM uses the MAF at all times. The PE table is just a % of fuel added per RPM cell. If the PE tables were the only thing used at WOT then we wouldn't be having this problem with the MAF maxing, the PCM wouldn't care.

After the MAF maxes the PE table is the only thing left for fuel enrichment, and should be used exclusively at this point.

Did anyone ever get the pro-m maf to work? The pro-m was supposed to read over 900 gps.

You can get the stock MAF to do the same, just need a frequency divider circuit. My friend and I have designed a circuit from readily available sources on the internet (just search for freq divider) but that is as far as we have went. My friend is just thinking of going MegaSquirt and doing away with the MAF.

Dividing the MAF freq in half or a third would require some retuning, possibly just a change in the injector constant to give the car more fuel for the less air it thinks it's getting. The circuit is not real complicated, If I remember right it just uses a 555 chip and a few resistors.

That is absolutely incorrect for WOT, The PCM uses the MAF at all times. The PE table is just a % of fuel added per RPM cell. If the PE tables were the only thing used at WOT then we wouldn't be having this problem with the MAF maxing, the PCM wouldn't care.

After the MAF maxes the PE table is the only thing left for fuel enrichment, and should be used exclusively at this point.
We have a communication error, I didn't mean that the MAF was not used, only that once it is maxed it no longer has useful input and the PE tables must be used to compensate.

We have a communication error, I didn't mean that the MAF was not used, only that once it is maxed it no longer has useful input and the PE tables must be used to compensate.

That is absolutely correct ;)

You can get the stock MAF to do the same, just need a frequency divider circuit. My friend and I have designed a circuit from readily available sources on the internet (just search for freq divider) but that is as far as we have went. My friend is just thinking of going MegaSquirt and doing away with the MAF.

Dividing the MAF freq in half or a third would require some retuning, possibly just a change in the injector constant to give the car more fuel for the less air it thinks it's getting. The circuit is not real complicated, If I remember right it just uses a 555 chip and a few resistors.

Interesting. Let me know how it turns out.

You know of anyone else thats tried this?

Later

Dividing the MAF freq in half or a third would require some retuning, possibly just a change in the injector constant to give the car more fuel for the less air it thinks it's getting. The circuit is not real complicated,
If I remember right it just uses a 555 chip and a few resistors.

You will have an issue with the 555 being stable in an under the hood environment (freq shift with temperature gradients).


Another issue is that the hot wire can only sense so much so even with freq division it is still capped. (Both in terms of freq output and accurate range) If the snsor only puts out 11.6khz max at 500something gms, you will still be limited to maxfreq/2

The best approach is to do kinda like we have to do on the Mustangs. Have a much larger sensor calibrated for the stock lookup of freq vs airflow but halve the airflow. Now double the physical size of the injectors. This is all in an effort to reduce calculation accuracy issues in the PCM

or take two mafs run them in parallel.. add the frequencies together then divide by two.

As stated, just dividing the signal by 2 on a single maf wont work, because the actual maf is not accurate above a certain level.

or take two mafs run them in parallel.. add the frequencies together then divide by two.

I could see that would be possible with some effort, however you either have really bad inlet piping on a single head unit or a twin head unit system. Possible, but as cramped as our engine bay already is, if you've gone that far with a twin system and have room for the extra MAF's, you probably have the extra bit to go to a standalone.

On the megasquirt issue - I did some searching a while back after a guy I know who does RX7's adapted it to his car (dont ask me how, I dont know enough about them), but he was telling me some things about it. I dont know how true they are (havent read a lot yet, but after reading this thread I'll search some during lunch) but not many lt1 guys are using it. I searched the forums a while back and you dont find much on it...

There are several options available - the only issue is finding a solution where you dont loose accuracy and are somewhat "plug and play" without too much hassle. I've yet to find something that made me happy. And just to throw some more gas on the fire, there's always the Sy/Ty ecu idea. :p

Jordan, the freq to airmass lookup isn't linear so a simple addmul wont do.

You have to do a freq to mass lookup per sensor, add the results , divide by two (or three with some of your monsters ;)) then do a mass to freq lookup, finally output that pulsetrain.

I thought of building one of these a while back then I realized that a MAFT could be programmed and retrofitted to do this. Now days, the ProM jobby should work.

Exactly. Multiple MAF's take a bit of work that almost negates it, though I say the space issue is more annoying then the electronics (I looked into it a little bit too, but I'm guessing not as much as you Luna) but I dont know enough about the Pro M's construction and the inner works of the lt1 ecu to really make a decision quite yet - and someone (highlander?) was going to try the proM at some point.

yea, it would take some tuning in the MAF table to make it work, certainly wouldnt be plug and chug!

I think the prom MAF is the best route.

Can someone fill me in on the Pro-m?

i would also like to know more about the pro m, i was told by a friend of mine that they went out of business, but started a new company under a new name...

I noticed Pro-M site was down.

Welcome to the world of P0103. The MAF table, is only translating a frequency received from the Mass Air Sensor for a grams/sec reading to be used in calculating actual air volume entering the intake. Lucky non-FI guys never experience this problem.

If the intake volume is 3" in diameter and the maximum flow of the MAF before frequency overload is XXX gm/s (non FI)...

Can I add another, in parallel, unrestricted bypass port to the intake (a Y connector) that is not measured (no MAF) but equal to the same flow characteristics as the airflow through the MAF, (1:1) that allows air to enter the intake?

Then, the air entering the engine (xxx gms) would be incorrectly (obviously)measured at the existing MAF by some percentage less (~50%) than actual. At that point, you could adjust the MAF table to accomodate for the actual flow of air, for the frequency. If twice as much air was actually entering, (of which 1/2 was routed around the MAF), then adjusting the MAF table would be as simple as just doubling the gms at the designated frequency.

(i.e. Current: 2.46khz=3.442 gm/s; New 2.46khz=6.884 gm/s)

Of course, these numbers would rarely be exactly 1:2 throughout the spectrum, especially at higher frequencies/flow rates and very low frequencies/flow rates. Also, air, like water and electricity, tends to move in the path of least resistance and the MAF would add some resistance that would push some air into the unrestricted port, resulting in some mis-measurement....

So, is this doable or just another crazy scheme? (of course, our SMOG-Gods would hissy-fit like crazy, but we already know their take on anything we want to do..)

This is just my opinion and what worked for me ... and it follows that the simplest idea usually works really well.

I have been running my OBDII for almost three years at 611rwhp using the regular MAF?! If you look at my dyno chart in my signature, you can see that it is smooth and the A/F is flat. Secondly, many people ran high power using the regular MAF with OBD1. LJ ran 9.9 with that setup and is still running his car in the lower 9s.

Although we did port our MAF (not recommended), this is not what made it worked. With OBD1, it works just fine, as posted earlier, by tuning the PE table (using this file http://para.noid.org/~lj/PCM%20Tutorial/DynoTune.zip ). All the PCM does is it will send out a code but will not affect any thing else. Go here to OBDI - http://para.noid.org/~lj/PCM%20Tutorial/Abbreviations.htm for more information. On OBDII, it is more complicated because when the code occurs the car appears to be cutting the fuel by half! The power drops, engine goes way lean, and you feel like it hit a brick wall. On OBDII, there is a trick that we did on my car. I couldn't say this before since it was not my idea, but since it is mentioned here, I want to clarify that it does work.

LJ helped me dyno tuned my car and it ran in the CA traffic jam in 90F no problem. We did do the dividing the MAF table by half and dividing the Injector Constant by half. Then we dyno tune it and it works just fine. I had dyno tuned the car 12-14 times consistently. It may not be the best solution but it definitely works well. I have been driving this car for almost three years, road raced on the track all day in +90F six times, and autocrossed a dozen times already.

Hope this help people. And always dyno tune your car before you do anything since different car behave differently. For example, I just found out my car was running without the Hi-6 hooked up for these three years and through all the dyno tuning!! I just came back from Thunderhill and it ran perfect if I don’t connect the Hi-6TRCII (which I think is bad now), so well that I finally broke my u-joint and twisted the 1LE DS going 115mph in the middle of the front straight in fourth and fifth gears.

cheers

Any more info on this Pro-m maf? And would cutting the injector constant and maf table by half work on forced induction OBD2 cars? how would a 2 or 3 bar map fit into this (possible solution?)?

Also, since fuel is cut in half on OBD2 cars once the maf is maxed out, could the maf massager eliminate this problem by fooling the computer into not throwing a code (if in fact that is all the maf massager does)?

hey guys, i dont know the first thing about tuning. i dont even have a scan tool. but when i put my blower on my maf freaked out. i hit about 4000rpm and i thought i blew something up. it lost all power and it ran like crap afterward. my brother in law took it to work and ran the code and of course it was 103. we took the maf out and it ran fine, a little rich, but it ran well.

so i figured the easiest thing to do was to get the maf massager. after that it has been running fine and the af mixture was fine when i dynoed it.....

just thought id throw out my maf massager experience.

For obd2, LT1 edit version 2,2 has a program feature for setting high maf failure point. I also was running onto the obd2 limit, then, got the upgrade and maxed the high threshold value to 60K+ from stock setting of 10k. Took care of the problem. LT1 edit is around $550, but, you can tune just about everything.

For obd2, LT1 edit version 2,2 has a program feature for setting high maf failure point. I also was running onto the obd2 limit, then, got the upgrade and maxed the high threshold value to 60K+ from stock setting of 10k. Took care of the problem. LT1 edit is around $550, but, you can tune just about everything.
Wouldn't you still run into the problem of the MAF sensor itself maxing out (i.e. too much flow for it to read)? Are the PE tables still just taking over after that like in the OBDI cars without issue?

. . . LT1 edit is around $550, but, you can tune just about everything.

Can you tune accelerator shot? (fuel adder for change in TPS)

Mike

I believe you can get tunercat for obd2 lt1s for approximatly $400. and I think it does everything that lt1 edit does.

Sorry if I seem to be hijacking your post, but this thread has got me thinking. I was previously using the Maf Massager to stave off the dreaded high Maf fault. But after purchasing LT1 Edit I pulled it thinking by disabling the fault code I was ok. But can anyone with rock solid knowledge on the subject tell me if I've made a mistake here. Does the Maf still max out and cause the fuel to be cut in half on OBDII cars even with the fault code disabled?

Sorry if I seem to be hijacking your post, but this thread has got me thinking. I was previously using the Maf Massager to stave off the dreaded high Maf fault. But after purchasing LT1 Edit I pulled it thinking by disabling the fault code I was ok. But can anyone with rock solid knowledge on the subject tell me if I've made a mistake here. Does the Maf still max out and cause the fuel to be cut in half on OBDII cars even with the fault code disabled?
I believe your question is directly related to this thread. I'm curious myself to the answer to that question, but I think we may be looking at an unmarked (unexplored) territory because I've seen this question asked before with no answer.

I've read comments by people who claim the injector pulse width is cut by half on an OBD2 system when the MAF threshold is exceeded. I have no physical data to support this. Most of what I have learned on obd2 programming is from L J and Christian M. L J's document helped me. Possibly I can experiment since now I have a wideband o2 to test with.