Hi,

Are PE tables used in a 100% open loop tune or does it default to VE tables for WOT fueling? There are contradicting theories that suggest that PE tables are only used on Closed Loop tunes, but I am not sure if this speculation is just for 94-97 FBody's. If your answer is no, would the following work.

Since the latest $DA definition file allows us to lock both Long-Term / Short Term integrators, I was thinking of enabling Closed Loop, but allow zero fuel corrections in Long-Term learning by setting the min/max to 128. Since the PCM will still make short-term corrections, I can also set min/max to say 124/128. This will allow minimal correction when in Closed Loop and not affect my WOT/PE fuel curve when at WOT condition.

This may work, but it may be pointless if PE Tables are used in a 100% Open Loop tune. Please help a MAN OUT!!!!

Thanks

 

Take a look at the tables Open Loop %Change to Fuel/Air Ratio Vs MAP and versus coolant temp. Also, why do you want to run open loop? If your VE table is correct, LT and ST trim will both go to 128 when the system goes into PE.

 

Idling is the problem, at start-up my car runs fine in open loop, but once it goes into closed loop all problems start. Long-Term BLM's dropped to 108, and hence WOT/PE fueling is affected because it defaults to BLM's of 108 to make fuel corrections (runs WOT very lean).

I tried adjusting VE tables, under the rpm range and MAP conditions for idling, (brought back the %'s as much as 25%) and it brought no change to Closed Loop operation, in matter of fact when in Open Loop the car would cut-off (too lean) under idle/part throttle conditions. So I knew, what I was doing did affect my idle fueling (I could tell in Open Loop), but under Closed Loop my BLM's never moved over 108.

This tells me my 0'2 sensors do not read correctly, but I have replaced them numerous times, or have other problems that I cannot identify. I do not have any leaks, compression is strong throughtout all cylinders. The cam is rather mild (XE230/236/112), but may be on the edge of being "too big" for the 1993 Speed Density computer because of the overlap, or cam reversion.

I know that limiting myself to Open Loop operation can be dangerous to the car as it will have no means of adjusting for extreme lean/rich conditions if something were to happen, but at this point I just dont care, and its a toy car anyways.

 

The '93 system should be able to accomodate your 230/236 cam, but you may have to lie to it. If your LT fuel trims are at 108, that means the system is trying to pull all the fuel it can (108 is typically the limit for lean trim, although it can be changed). With any type of performance cam worth a damn, overlap is sufficient that a lot of raw fuel gets into the exhaust system. That makes O2 sensor readings inaccurate, but you can compensate for that by entering a different injector size. I've found that you usually have to go about 2 pounds over the actual size. If you have 36-pound injectors, try 38-38.5 as the injector constant. That will cause the computer to shorten pulse width, which will lean out the mixture and get fuel trims back in line. The only problem is that you'll have to redo your VE and PE tables because the change in injector size affects every aspect of air/fuel. You may also have to make some adjustments to the open loop tables. If you like, PM me and send me your calibration file. I'll take a lok and make some suggestions. And just to make sure you're not chasing your tail-- are you sure your injectors are the size they're supposed to be? I've seen a lot of problems like this caused by mislabeled or poorly operating injectors.

 

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Thanks