I understand this all but 1 thing...will not a ported maf sesnor give you up/down afr on the dyno not a stright line or curve..and if so how do you fix this...

Why not just let the maf sensor max out and adjust from there, what is the big deal, or is it because you want to push it higher up in the rpm range..

 

Well, for me the MAF will max out around 4000rpm. Pretty much once my turbo is fully spooled.

Issue is this. Lets say you have a Supercharger and you tune your car for 14psi. Get on the dyno, tune it all out. With the MAF maxed, if you change the pulley the ECU cannot adjust for that. If you change the pulley you will need to have it re-tuned.

With a turbo, adjusting the boost is much easier, hence why so many turbo guys blow up their motor. Just turn a **** and more power. Easy, but only if your system can account for it. However, a supercharger builds boost and is limited by rpm and pulley. It cannot suddenly produce 4-5psi more then you expect for no reason. It cant. A turbocharger uses a wastegate to limit the boost by controlling the speed of the turbine. You run a vacume line from your intake manifold to the wastegate. Once there is so much pressure on the wastegate from that line, it opens. What happens if that line breaks or clogs? The wastegate will not open, and your boost may increase 4..5..6..7..8 or more psi then you wanted.

On an engine even tuned a tad rich, a tune running 14psi then running 18psi on the same tune will probably kill your motor. Not to mention the other issue is that turbos (depending on setup) will spool very fast (within a few hundred RPM) and when this is the case, by the time your eye notices the guage is too high and tells you to think "!!!" and lift your foot off the gas, your motor has probably already spent half a second under maximum load and a very lean condition. That might be too late for your motor.

I want to make the ECU able to read the MAF at such values (and the MAP as well) so that if for some reason a hose breaks and my 14psi jumps to 18 or 20 my motor has atleast a chance of lasting another half second longer till I get off the throttle. Some would say I should thusly use a FAST or DFI, but my car is a street car, and tuning a FAST/DFI for daily driving is rediculous.

I'm all about backup/safety systems, and this seems like a good one. If this could work, it would be able to provide something that might account for additional air in the event of something going wrong.

But I have no intent to rev the engine past 6000. 6500 maybe... No need to spin it that high.

 

There is a simple fix for a MAXED MAF.

Using the newest Tunercat def file or LT1_Edit 2.2 you can Increase your MAF max fail point. Stock is set to 407 GPS.....the factory MAF table goes above 500 GPS. Just increase the MAF MAX frequency fail point and it will work fine.

 

That's a pretty interesting article. I had no indea there were adaptors available to us a Ford MAF on a GM vehicle.

Has anyone tried this before?

 

One very important point that eveyone here are missing is that - what is the main difference in how a LT1 OBD1 handles the max MAF situation versus a LT1 OBDII (snorkelface 97). They will both send out a max MAF error code that we can turn off easily. However, the OBDI (like Rich) will do nothing else. Therefore it can be programmed around it. However, on an OBDII, it does not just sent an error code but something drastic will happen. At around 4800rpm, in an OBDII LT1, when the MAF is max out, it will look as if the PCM cuts the fuel by half and the A/F will go straight up! If someone try to dyno tune this and not look at the real-time A/F to let off, the motor will go boom!

Go here for more information and look under "OBDI" - http://para.noid.org/~lj/PCM%20Tutor...reviations.htm LJ (www.acceleronics.com) has a great deal of experience and information about this.

I agree with TriPinTaZ that the MAF can still measure beyond what the PCM has set as the max point. The old way that this is fix is to go back to an OBDI. However, if you can figure how to trick the PCM away from or around this max point then problem is solve.

For Schurters LT1, I can't tell if you have an OBDI or OBDII. If you have an OBDI, you will just need to add fuel in the PE. Most SC cars are running with maxed MAF, especially when they are beyond 500rwhp.

Like Rich, I ported and descreened my MAF four years ago, when we all thought that this is great. Now, I would probably not do this, unless I am pushing beyond 550rwhp. In my dyno chart (in sig), my A/F does not jump around.

cheers

 

What is this new tunercat file..there is an update..and this can change the maf tables....

I do have an old ported maf case i can switch over to that, so just port the case as much as i can and leave it, as this will lean out the car what about reg driving around town....

 

I have OBD2, all I did was disable the SES code for max maf and raise the fail point frequency. I was experienceing my AFR jumping to 15:1 at high RPMs (6500+) when the MAF would hit its fail point.

 

what is the latest tunercat revision??? version number??

i did 607rwhp with the maf and i never maxed it... i ported the max to heaven... seemed to work...

I bought a pro-m maf that is setup from 0-11000hz and 0-900g/s to solve this problem... maybe... but.. if the stock maf works... one less thing i might need to worry about adding to the stock pcm... $560!!!!!

the problem i see here is this... after the 11216hz table, what does the PCM reference???? does it just interpolate or something? does it interpolate linealy?

 

no, it just stops adding fuel. I dont see how you made 600rwhp and didnt max the maf, if you do the math- its not possible (unless you are talking nitrous).

another problem is drivability. If you max the maf at part throttle (which is easy to do if you make a lot of power) you could easily go dead lean.

 

Dont know because i tuned another supercharged stock headed 350 and i maxed the maf SUPER EASILY, but mine didn't.... it just didn't max and i tuned around it... i thought it was because it was REALLY PORTED.

 

Good that someone brought up the OBD II issue. Tht completely slipped my mind.

Rich

 

THe maf limitation is addressed or bypassed only on obd2?

i see no maf limits on the $EE calibration for tunercats...

still... i guess i'll give the pro-m a break...

but i might convert to obd2 just to have the IAT timing table.

 

I increased the GPS reading in the maximum part of MAF table 4 to 510, but it still doesn't change what frequency output of the MAF it maxes out on. Just adds a little more fuel up to the point where it maxes. I haven't checked out the new tunercat file either, so I'll see if anything has changed.

 

What is the maximum afgs that the maf reads???

 

From what I have herd, and not generally concidered to be true because I haven't taken apart the computer and looked, the circuit consists of 2 256 bit registers giving a theoretical max of 512 gps. I have had mine at 510, and I have logged this reading several times when the MAF is maxed. It occures at the same time as the stock 471gps, however like I said before when the MAF is maxed it adds a little more fuel to the mix as the PCM thinks it is locked at 510 gps of air and not 471. still doesn't get around the fact that tuning still needs to be done in the PE table per RPM to get things right.