Has anyone experienced the PCM learning to tune out the MAFT settings. I am seeing some variations with AUTOTAP. I also think the Recalibrated MAF temperature sensor is adding timing causing KR at WOT..I think I'm gonna trash it.

 

you're right about the recalibrated MAT sensor, get rid of it!
I went through the same thing!

I'm sure about the PCM compensating for the MAFt, you have a good point there.

be sure to post your results! :cheers:


[Modified by RPOZ4Z, 1:29 PM 4/13/2002]

 

The PCM will learn the part throttle setting on the MAFT and compensate. It will not learn the WOT setting. It really isn't a big deal anymore, as LS1 Edit gives you the ability to do what you want. The MAFT will soon be a museum piece.

Todd

 

I just wish the price of LS1 edit would come down a bit..... :(

 

How much does LS1 edit costs and where can I get it?

 

Pricing and description at http://www.carputing.com.




[Modified by ToplessTexan, 7:17 PM 4/13/2002]

 

dittos on that.

 

can someone tell me why LT1 edit only costs $200.00 and LS1 edit is $550.00? :confused:

 

That's a question for Ken or Dave. ;)

Folks fell all over themselves to buy mail order tuning at nearly that price. Also, consider how much one could spend on MAF ends, MAFTs, etc. I look at a tool that I can continue to use as having more value. With all the software folks around here, maybe someone will come forward with a better (i.e. cheaper) mousetrap. I won't be holding my breath though...

The good news is that it's the same for F-body and C5. :jester

 

will I still need autotap with LS1 edit?

 

Yes, you will still need some way(s) of measuring the effect of your changes. Scan tool, dyno, timeslips, etc.

 

Damm....
I figured if I sold the MAF translator and autotap I would only have to add the difference to get LS1 edit. :(

 

You can still sell the MAFT. (Still a market for that among those for whom PCM programming is not an option for whatever reason.) Plus any other MAF gadgetry you have laying around. I keep meaning to do this and get some shelf space back :D

 

First you have to understand what the PCM does and what the MAFT changes. Once you understand that, then the question can be answered correctly.

Fundamentally, the MAFT modifies the MAF frequency going to the PCM. It either tells the PCM there is a greater or lesser perceived load based on this frequency manipulation.

During part throttle operation, the PCM uses inputs from various sources to determine the base fuel equation, and timing. The fuel equation is used to fire the injectors. The inputs for non-wot operation include the MAF signal, RPM, IAT, Throttle Position, and long term, and short term fuel trims. The fuel trims are registers in the PCM, which are modified by the PCM, based on O2 sensor input. If the O2s detect a lean condition, or a rich condition the fuel trims are skewed accordingly. They are then added to the equation until a stociometric ratio of 14.7:1 percent air/fuel is achieved. Its a basic control systems method that constantly normalizes the operation.

If you took a MAFT, and dialed in some richness (or a greater perceived engine load), the O2's would pick this up and skew the fuel trims to achieve 14.7:1 ratio. What you have done is permently changed the perceived load on the motor, and forced to PCM to normalize to 14.7:1 ratio during non-wot.

So did the PCM "learn out" the maft? YES and NO. YES, it went back to 14.7:1, but NO, the fuel trims were permently modified, which changed the overal perceived load of the engine, which effects timing.

Since fuel trims are frozen from being updated during WOT, and 14.7:1 is not the objective of the PCM in this mode, changes made to the air/fuel ratio are permenant.

Is this a crude method over PCM programming? Yes. Is it still a simpler and viable option for some that dont want to delve fully into that world? Yes it is.

Nonetheless, all these principles of understanding are needed before even using LS1 Edit.

For more info, see my web site.




[Modified by kewlbrz, 11:45 AM 4/14/2002]

 

Hey Now:
Once again your posts make hard to understand things,for me at least :lol: , easy to understand. Thanks again, for your postings. :cheers:

 

Thanks kewl... I have read your tech tips....by "PERMANENT" you mean as long as the MAFT settings are undisturbed or the MAFT is removed...correct...than back to stock fuel trims..correct.

 

Just remember that the PCM will use the fuel trims to achieve 14.7:1 air/fuel ratio during non-wot. From the factory the long term trims should theoretically be within +/- 5% of 0.

Then if for instance you added MAF ends or increased air flow with heads, cam, headers, displacement, etc... and performed no tuning and had no maft, then engine would temporarily go lean. The Fuel trims would skew over a period of time in a positive direction to add more fuel to the base equation. Perhaps to +15%. If nothing else changed, and no tuning occurs, then the long term fuel description would stay at about +15% so it could maintain 14.7:1 a/f ratio.

Now lets say you add a MAFT, and dial in some richness (more perceived engine load. Then the engine would temporarily go rich, and the fuel trims would begin moving in a negative direction back towards 0 from +15%. Mabey even beyond 0 into a negative state if you dial in enough enrichment (more perceived load) on the MAFT. Lets say you dial in +20% clockwise on the base setting on the MAFT. Then Long term fuel trims would skew perhaps to -5% (to lean the mixture, - ie. take away fuel from the base fuel equation). If you did not change the maft setting. Then the long term fuel description would stay at or near -5% to maintain 14.7:1 a/f ratio.

During all these mods and MAFT usage, you'll notice the PCM always normalized back to 14.7:1 no matter what, but that the perceived engine load changed dramatically via the permanent fuel trim changes.

Change the perceived load, and you permenently change the fuel trims during non-wot operation. Which in effect changes timing, and what timing tables are chosen. Both in base operation and during WOT.

Remember that during WOT, fuel trims are frozen from being updated, so manipulating perceived load, does not change the state of the fuel trims.

As a side note: depending on the year, the PCM can only adjust (compensate) the fuel trims to about +/- 25%. After that a PCM code will typically set, indicating a too rich or lean state.

Another side note: You will notice that during WOT that often times fuel trims are all "zeroed out", and sometimes that have a value that is not 0. What happens is that the PCM during WOT, will look at its state of operation during non-wot, and if the fuel trims were adding fuel for a lean condition, lets say +5%, then you will see that +5% carried over into the WOT fuel cell. However, if the fuel trims were removing fuel for a rich condition, then during WOT, you will see the fuel trims locked at 0. This is sort of a built on safety net if you will. This is why the WOT potentiometer is a handy tool on the MAFT to fine tune WOT. The WOT pot is a signal that is added to the BASE signal above a specific frequency. But is not, nor may need even need to be adjusted to use the MAFT and the BASE setting effectivly.


[Modified by kewlbrz, 11:07 PM 4/15/2002]