My block learn is stuck at 108 cell 4 at idle. This is obviously way to rich. The only way I can lean it out is to add artificial vacuum to the MAP sensor. The motor makes 10-11hg at 1,000rpm. If I bring the vac up to 14.5hg or so the car leans out to 128, but the cell never moves from 4. If I am right the cell should be at 0 at idle and 15 at full throttle. I have replaced the o2 and the ECM and tried leaning the thing out to 30lbs but to no avail. The WOT is just about right at 42psi.(.868v) The car is so rich that I got 86 miles to a full tank of gas. Even at part throttle cruise it is block 108 cell 4. T.P.I.Spec has already taken 4lbs an hour out of the program. I have 30lb Accel inj. Thier answer seems to be to just lean the whole program out, then play with fuel pressure. Isn't there different parts to a program they can work with. I have read something about the VE table or something. Please help. Some of my combo is in my sig but I can post the rest if need be.

 

I can't really help you as I have MAF and haven't really looked at the SD setup. But just an observation, my car's cell #s don't follow what you said about 0 at idle 15 at WOT. I took a long road trip yesterday with my scanning software hooked up and the cell # varied from 0 to 15 at different throttle positions (No WOT at all, and no hard acceleration- going for gas mileage).

I don't think that helped any, but if the cell is supposed to be 0 at idle and 15 WOT I'm curious because I have something wrong it looks like.

Sparks a flyin'

 

I understand what you are saying, but my cell never goes below cell 4. If your car cycles from 0-15 I would say your stuff is fine.

 

Lethal, I have noticed that while idling (open or closed loop) that the ECM stays in Cell 4. I am currently going through the hac for the SD ECM, and it looks like Cell 4 is a "special cell" for idle. As I learn more, I will attempt to explain the intracies of it. But idle is a special situation with the ECM and the BLM Table.

Also, I have modified the "Edge Boundaries" of the BLM table for MAP and RPM values, to try and use as much of the table as possible. I specifically modified the "boundaries" to ensure that in "Idle" it should NOT hit Cell 4, but it still does. That is when I started to review the code and started finding "special code" for Idle.

But I do feel it is worthwhile adjusting the "Edge Boundaries" for the MAP and RPM to use as many of the 16 cells available. But you will find some of the cells are impossible to use or only in unsual circumstances. (e.g. Lowest RPM range with highest MAP range is a good example).

Large cams are a challenge with SD due to the low vacuum (high MAP reading). Adjusting the VE table at the proper MAP value in the low RPM area can help. Another area you might be able to play with is the "Injector Pulse Correction vs Battery Voltage" table, especially if there is a noticeable voltage difference at idle due to underdrive pullies.

Lastly, have you noticed that even though you may have adjusted your "Idle Speed (RPM) vs Coolant Temp" to give the engine a higher idle that when you put the car in gear that the RPMs drop to 800 rpm max?

 

The Idle drops to around 800rpm in drive. Is that low? I read an article where they built the same motor and they said it should have 950rpm curb idle. Is curb idle in gear or what? Yes I also have underdrive pulleys but the voltage stays around the 13 mark on the guage unless I turn on the lights of something. Could that have something to do with it?

 

You aren't going to get an idle higher than 800RPMs with the car in-gear if you are using Speed Density with the latest GM Code (AUJP, etc). GM limits the RPMs to 800 when the car is put into gear. You need to make a couple changes if you want a higher idle.

Tim

 

Any chance you know a little more about this? I guess my question is this: the calibration says that the ECM is in an "idle mode" if below x mph and a y% TPS. Are the BLM readings that are obtained in that range of operation just as valid as the ones obtained outside that range? I have always noticed being in Cell 4 at idle and very low acceleration/coasting, but still treated the BLMs just the same as any other non-PE BLMs. Thanks Glenn, -Matt-

 

Matt, at this point I too am treating the readings I obtain while Idling in Closed Loop the same as any other reading I obtain (regarding BLM/INT). As I said, I am still going through all this code "the hard way" (documenting Source Code to get a complete understanding of what is happening). Once I have finished that part of the code, I will share all the information I have found - the good, bad and ugly.

Another area that is quite fascinating and I am also trying to get a better knowledge of, is the "updating" of the BLM and the interrelationship of the BLM/INT. I have noticed (when I have an unlocked BLM) incidents where I may have a BLM > 128 and an INT < 128, while in other situations the BLM may be < 128 and the INT > 128. From what I have seen so far, BLM/INT values as the following: 128/128, 129/127 and 127/129 all appear to be the same - but I am still reading up on this and not prepared to say that they are DEFINITELY the same value. But basically, it appears that if you were to take an "average" of the BLM/INT value would be the same as a "locked" BLM and relying on the INT value alone - but I am still reviewing that part of the code and I am not prepared to state that that is exactly what is happening.

 

I've seen and heard LETHALRACER's car, and with his size cam 234-244 duration, it seems to me that the speed density computer is having a hard time adjusting to the low vacuum signal at idle. If he is only getting 10 inches of vacuum at idle, wouldn't that be the reason that the ecm is adding fuel (BLM at 104) thinking that the car is at part-throttle, or am I wrong?

It seems to me that since his cam is bleeding off cylinder pressure, that he would have to raise his idle vs. coolant temp almost as high as possible when the engine is cold just to get the rpm's high enough to create some decent vacuum. He has a vaccum reserve canister, but the thing only stores vacuum.

The car being in cell 4 makes me think that either he has to increase his initial timing, or add more timing at lower rpm's and idle in order to raise vacuum so the map sensor gets enough air to idle correctly at 128.

Someone please correct me if I am wrong. His chip was burned by TPIS, and I don't think they have a clue what to do to fix it. I'm trying to help by getting some suggestions to tell the guy at TPIS.

 

B. It's Brett, The cam is a 236/242. But that is besides the point. What I wanted to tell you is that the module was bad from D.U.I. Well not bad just messed up. I put the stock module back in and the Set Timing Connector works now. I set the IAC and the Timing (6)and the TPS. The car smoothed out compleatly, and is extreamly responsive in spite of the rich condition. It still feels like it has no power in second though. Taking out the Hyd-Rev didn't make a difference so far. But it was in drive at about 50mph and matted it, it spun the Nittos for about 15ft then fell off and wouldn't pull. I am starting to suspect the tranny. The rich condition continues and I havn't rechecked the vacuum to see if it is any better. I found another problem in the T-Body. The EGR port is now blocked off and that is where it gets its idle air from. Check yours out and you will see what I mean. That is probably why it needs so much throttle angle to idle. But it happily idles at 800-865rpm in drive still with a noticeable lope but smooth.

 

What does your INT and BLM cell and O2 info look like now?

 

What is INT? The rest of the stuff is the same as before. It is still way to fat.

 

So just advancing your initial timing smoothed out the idle?

Is it still runnin rich?

I still think your VE table needs to be tweaked.

 

Still runs rich. But fixing the module, setting the timing, and setting the idle smoothed it out alot. Now it revs clean and smooth. The block learn is still at 108. I set the timing at 6deg using 0 on the gun. When I used 6 on the gun the timing read 10deg.