In my eternal quest to find easier, lazier ways of doing things, I was thinking of how to handle the AE on my new setup. Obviously, the MAP AE provided in stock TBI computers can handle the fuel settling/wetting during transitions, but the TPS AE that provides the actual enrichment seems cumbersome.

I was instead thinking of providing the actual enrichment via the AFR rather then a pulsewidth as its done in the stock routines. It seems to me to be a reasonable way to provide the enrichment as an independant parameter during throttle transitions. I was testing the MAF, and it seems to reach steady state during transitions in < .1 secs, provided the airflow is greater then 10 gms/sec or so, so it should be able to respond fast enough to allow for accurate fueling during transtions.

Any reasons why it really shouldnt work?

 

TBI really needs a crapload of fuel immediately, and trying to do that with % is difficult (picture a base PW of 2 ms, but needing 8 ms to wet that huge manifold, from idle, and then tapering that off quickly so that 400% isn't applied to 6 ms). A PW AE is independent of the underlying base.

It can be done with % (or AFR, same difference), but you'd have to have a more complicated algorithm.

What MAF are you talking about? Are you using one with TBI? I've read that MAF is actually well suited to TBI (I think Grumpy said that).

I may have misunderstood your post though - are you wanting to just enrich a little during transients, such that it actually shows richer, and match a newly commanded AFR? Or are you wanting a transient control algorithm that compensates for the wetting and inherent lags found in EFI?

 

Im wanting to just enrich during acceleration with the AFR. The PCM has a routine that provides the additional fuel needed to compensate for manifold wetting during acceleration thats based on the MAP. This isnt really used in the stock cal, but does work in practice. They seem to mainly use the TPS routine for all the AE.

I was going to primarily use the MAP/stock MAP AE code to handle the actual needed transient fueling, and use the TPS as well as the AFR to add the additional enrichment. I wont be using a KS, so some added fuel and maybe some reduction in spark wouldnt hurt, and it would be nice to have some easy way to control/dial it in.

 

It works quite well. Much easier to tune and is not affected by temperature like the SD was with a wetflow system. I was using a freq.to voltage converter and a stock ECM, but the A/D and 8-bit signal handling resolution wasnt very good and the converter had some issues. It worked, but was crude at best. Ran like it had a holley carb.


I found out when going through the code for the 93-95 PCMs that the transmission output speed input is set up to accuratly read in FM frequencies up to 35 kHz (low-pass filter cuts off after that) and an input for 0-5V square wave is provided in addition to the one for the magnetic pickup. Low and behold, plug the LS1 MAF in place of the function generator, and it reads it just fine. The HC11 can also handle the 32-bit calcs needed to generate the mass air per cylinder and needed pulsewidth. I wrote and tested most of the code for it, but havnt had a chance to put it through its paces in real life yet.

 

So, I guess this would probably be a legit way to handle the enrichment, then? It should make dialing things in a little easier.

 

If you think it would help tuning, then it won't hurt to try and find out!

Curious: Are you chosing AFR as an easy way to get into the PW calculation? Or do you want AFR to match actual AFR?

 

It certainly would be nice if the actual drop in AFR and the commanded drop in AFR matched during AE, which is what im shooting for. Id assume that there will probably be some difference in what I call for vs. what I actually have during transients. In theory, it should provide a way to enrich the fueling during transitions thats independant of the engine as its strictly an AFR.