SABLT194

I have been where you have been. I scratched my head for an hour on the dyno wondering why my PE table changes weren't doing squat, and I made massive changes ( like a 25% fuel add) just to proove that I wasn't having brain fade. I was doing my pulls right after firing it up and not waiting for the Closed loop timer to time out and set the CL flag. Then, in a moment of desperation, I let her go CL before doing the pull, OMFG, It went friggen rich like you wouldn't believe. I did the rest of my pulls in Closed Loop (with BLM locker) and I was able to put actual AFR any place I wanted.

This brings up a good point, It may be a bit dangerous to go WOT in open loop with a heavily modified car. We may be going lean (even though open loop tables are enriched) and not ever know. Makes me want to go do an open loop pull just to make sure every thing is hunky dory.

Oh yea, This is on a 94 PCM, I wont speak for the 93's or earlier 730's, they're a different animal with a memcal.

Alvin, Do a test on a 94/95 next time your doing one and see if you're results support what we've seen.



Steve

Alvin@pcmforless.com

I'll ask Bryan, He should have an idea one way or the other.

I dont' do many 94-95's. I focus on chip cars.

Thanks guys,

engineermike

I decided to do a test with mine. My car makes a little over 600 rwhp at 13 psi boost using the stock ECM and 84 lb/hr injectors. I've added ~33% fuel to the PE tables since the MAF max's out around 500 rwhp and I run mine rich (10.5/1) on top of that.

I had the engine warmed up, then killed it for about 15 minutes. Cranked it up, pulled out, and floored it within 1 minute of starting. The air/fuel gauge pegged rich. At 600+ rwhp and no PE, I would have expected it to run lean, like 15/1.

Mike

Alvin@pcmforless.com

So PE did work in openloop on 94/95? Still haven't asked Bryan... just hasn't come up.

SABLT194

Mike,

Do you live life on the edge? Doing a test to run a boosted motor lean is more than my stomach could deal with. I'm a bit surprised at your results. If your motor was warm, It will go closed loop within about 50 seconds or so. Did you verify that you were in open or closed loop with Datamaster during the pull?

Thanks for running the test.

Steve

engineermike

He he. . . some might say that. I've blown up several motors at 18 - 20 psi, but have become rather comfortable at "only" 13 psi. With 8.5/1 compression, retarded timing, a large water/air intercooler, and 93 octane, the engine's actually pretty safe. I would never try that at higher boost levels, though (actual I did - on accident).

What about this 3 minute timer I keep hearing about? I did not verify with a scanner.

SABLT194

I could not find the timer setting in either Tunercat or LT1 Edit. I looked at older 8D mask (90-92 TPI) and the stock setting for Hot Closed loop timer was 30 seconds. If I recall my 94 switches to CLosed Loop in about 45 seconds when the temp is at 180F. I tried to run out to the garage to do a test, but my battery finally bit the dust - no crankie

Steve

engineermike

I was just looking through TunerCAT and noticed something. There is a Low Coolant threshold TPS for WOT (PE), as well as a High Coolant threshold TPS for WOT (PE). The stock computer is set up such that, if the coolant temp is over 151 deg C (303 deg F!!!), then the car runs in PE mode. My guess if this is a safety feature, though there's an entirely different table that's %PE versus Coolant temp.

If someone were to play with the "Cool Thres for TPS for WOT (High Temp)" and modify the "%TPS Threshold for WOT vs. RPM (High Cool)" or "%TPS Threshold for WOT vs. RPM (Low Cool)", then I could see where you might get into the situation where it won't use the PE table when the coolant is cold.

I have to believe that it will use the PE table in Open Loop because the "Min Coolant Temp for Closed Loop" is set at 90 deg F, but the "% Change to Air/Fuel Ratio vs. RPM at WOT" (PE table) goes all the way to -40 deg F. If it doesn't use PE in Open Loop, then it would never use 2/3 of that table.

Mike

infinitebird

When I start my car with it warm it goes into closed loop almost immediately.

Hotwire

as long as both o2s are warmed and show ready and the coolant and iat show decent temps it'll go into closed loop.

Alvin@pcmforless.com

Theres usually a timer for CL no matter what temp your at.. I've seen them anywhere between 30 sec and 100sec depending on the mask.