cerino2000

I put this in the tech section but didn't get much result plus I have some more info to add so I am going to list it here too.

Car is a 96 with an eagle 383 rotating assembly. Fairly small cam specs here: http://www.compcams.com/Technical/Dy...4HR-10_001.asp

The entire rest of the car is stock with the exception of dynomax turbo mufflers. Stock heads, intake, manifolds etc.

The car had two problems:

1.) A slight surging idle when in gear. Turning on the A/C while the car was in reverse would sometimes stall the car!

2.) Car had more ping in it than what I like to have.

Prior to going to the dyno, did a bunch of logging. BLM's across the board stayed pretty much +/- 3% including at the surging idle.

On the dyno, we put it in open loop and it showed running at an AFR of about 19:1 at idle which would explaing the surge! We fattened that up. Took quite a bit of timing out of it to keep it from pinging. Making what seemed to be the appropriate changes to the VE table didn't quite net us enough AFR so the tuner scaled some of the MAF calibration. That worked and we were able to keep everything during idle and cruise around stoich. Gained 40HP from the tune.

Drove it home that night, all was well. No check engine lights and the timing curve was a LOT better ragarding pinging and knock retard.

The car did have a pretty rich smell during the rips on the dyno. We kept it for the most part about 12.5:1. I attributed the smell to the fact that I was just used to it being lean the whole time (I have owned it for about 2 weeks).

The next day (Wednesday) I noticed that it still had a bit rich smell to it just normal driving around put it ran great. I put the scan on it towards the end of the day and realized that it was never going into CL. The tuner forgot to set the threshold back that permitted CL. I changed it back and flashed the PCM and it went into closed loop just fine.

The BLM's however are not nearly as nice as they were prior to the tune. However, the car now idles just fine. The BLM's at idle for the most part always go back to -15.6% (108 BLM).

After heat soak takes place from driving it for a while, the timing curve STILL needs to be adjusted some.

I spent quite a bit of time with the car today looking to see if maybe I had a vacuum leak or something and I can find nothing. I used the spray bottle around the intake, found nothing. Inspected ALL of the vacuum hoses. Found nothing. Still have no Check Engine Light on. The rich smell is subsiding with CL taking control.

So, those are the facts. Something just doesn't seem right. It should not be hitting a 108 at idle but when the BLM's were at +/- 3%, the car wouldn't idle. I actually questioned the tuners wideband but he said that he had just calibrated it prior to us using it.

So what do those of you who know what you are doing think of all this?

STL94LT1

Hopefully, some of the more knowledgable tuners will chime in (Tom Wong. ect.). But again, I think you need to redue your part-throttle and idle tuning in closed loop. Also, think the 19:1 idle A/F was a result of the air pump running.

cerino2000

Hmmm...I never even considered the AIR pump. Not sure if the tuner did or not.

Beth396

Good morning,

Just to recap: you tuned the engine open loop to an AFR of 12.5:1, now you place it in CL and want to know why it's running at BLMs of 108?

In CL your narrow band O2 sensor feedback system will try to set the AFR back to 14.7

Can can't have it both ways. Either you run it open loop full time at a "performance" AFR or you run CL and the computer will try to offset the performance AFR and take fuel out to get to stoich.

Personally I like running OL full time. This has worked the best for my combo.

Beth

cerino2000

We tuned idle and cruise to 14.7 in OL. WOT was done to 12.5.

Beth396

Ok, so in OL the AFR was 14.7 at idle and cruise but once you go back to the stock O2 sensor your running rich. Doesn't add up does it? I really recommend that you buy a WB O2 sensor. They're not that expensive and you really don't need one that records data as long as you can see the display while your driving. Also once you get the hang of tuning yourself you get a better understanding of the tuning in general rather than looking over someone elses shoulder that's charging you by the hour.

I agree you don't want to smell gas while in idle. I idle right around 13.5 depending on air temp, but cruise all conditions at AFR 12-13. I didn't look at your combination but if it's anything radical why run CL? It's much easier on the brain to run OL. Once you get that down and have more of an understanding then go back and tweek the CL operation.

Really how often do you run WOT? ...which is just OL with fuel added (if that's the way your program it setup) anyway.

cerino2000

It is looking now like the reason we were running so lean is that the air pump was not turned off. This kinda throws things in a loop. I am going to revert back to the stock tune later this afternoon and start from there. I hate the fact I dropped the cash on the dyno tune and am going back to stock but I did get a good timing curve that I will put back in. Am I correct in thinking that the LS1's don't use an air pump? The guy who is my tuner is actually a great guy and I hold no ill feelings towards him. I mentioned the air pump and he sent me a new file. I am thinking that it was just totaly spaced since the majority of tunes he has been doing for quite some time are either LSx tunes or Ford tunes.

What really bothered be is that making the changes to the VE table weren't quite doing it (still running a bit lean) and that we had to go to the MAF Calibration table to get it to richen up. I am pretty sure now that this was all due to the air pump.

Do you know the conditions for the air pump? I know there is a threshold for minimum temperature, but what else determines when it is going to come on or go off? Should my WOT values still be ok? (i.e. does going to WOT turn off the air pump). Point I am getting at is I want to make sure that it wasn't affecting my AFR's at WOT.

Thanks for the info. Like I said, I am going to make some changes in just a while and see how they come out. I am thinking that the idle issue was likely the fact that it was still running a CI variable for the 350.

STL94LT1

At WOT your car should automatically go into open loop. So, your WOT tuning should be OK.

The air pump will only run at warmup, and for a few minutes after the car is warm and restarted.

As stated above any engine but the most radical should be ran in closed loop for the best driveabillty.



Good luck
-Mike

Atok

Are you sure your stock O2 sensors are Ok?

I agree with the comment someone made above. If you want to do your own tuning then you should invest in your own WBO2 to get you in the ball park. Then go to the dyno to fine tune it.

cerino2000

Ok, here is what I have done. I got a hold of the stock tune for the car and went through all of the tables to see where the changes were made.

There were mild (in a compare, they showed an average change of about 2.0) changes made to both the main VE table as well as the MAF calibration table. I really don't like the idea of changing the calibration of the MAF. The reason he had done that was because changing the VE alone wasn't giving us the correct results. We would make the change and it still was showing lean. At times though, all of the suddent the AFR would go to about 14.7ish out of the blue despite the car being shown as in OL the whole time. I am thinking that when things were suddenly going to 14.7ish, that was in fact correct and not the car finding a way to manage CL but instead I think it was the air pump shutting off. So all of the settings we made are kinda not worth anything (other than the timing).

I put the stock tune back in the car. The only changes I left in were the timing changes (which still need just a bit of work), the displacement changes (showing now a 383 instead of the 350) and the fan changes. I changed the MAF cal table back to stock as well as the main VE table.

I bought a wide band today with RPM module as well. I already have a bung. I will just have to try it out.

With this tune in place, my LTFT's at idle are back to about -3%. At no time at all during the log did the LTFT's go to the extreme. The highest I saw was a -10% which was under a float condition. The idle is still pretty decent too. Has a very very slight surge to it but only if you hold the brake while idling in gear and tap the gas real quick.

I would almost swear that the car feels stronger (SOTP) than with the other tune.

I am going to put in the wide band tomorrow and take it for a ride and see what it shows for AFR.

Just so I am on the right page here, I should see 14.7 or close to it with the air pump off going down the road correct? And then WOT will be undecided at this point, right?

STL94LT1

With your mild combination the car should run pretty well with the stock tune.

Yes, you want ~14.7:1 a/f at cruise.

You might be able to use your WOT fuel enrichment tables from your dyno tune.

It looks like you are well on your way to doing your own tuning.

MaxLean

And since no one mentioned it yet, the VE tables are used for speed density operation only. At least that's the general opinion and my personal experience (currently running a home made speed density tune on my 383. Got LOTS of VE table experience.) This would explain why nothing was changing when you were altering the table. Also don't forget that the ol afr vs load vs temp tables are set somewhat rich. At stock settings, the pcm targets something like mid 13s at cruise, so you shouldn't expect 14.7 under these conditions.
Scott

cerino2000

This is a very interesting statement and could explain a few things that I learned today. See below.

I officially did my first tune! On my own car. Used the LM-1 I bought yesterday and it worked fine.

I took the tuners tune out and put it back to stock with the exception of the timing and the fan settings. I bumped the idle targets by about 100 RPM. I reverted what he had in the VE tables and MAF calibration to stock values. I did leave the adjustment for the 383 vs the 350.

I am 99% sure that the AIR pump not being turned off was the source of the problem from the original tuning. I was able to tune the WOT AFR using the WOT vs Coolant table and then tweaked it at the top end of the WOT vs RPM table and came up with a beautiful 12.5 AFR under WOT after a handful of passes with tweaking in between.

The idle is pretty decent.

The timing curve STILL needs more work. It is becoming a major PITA but I am enjoying the challenge.

Back to what you said about the VE table, under what conditions is the VE table used? The reason I ask is that I adjusted the idle RPM ranges in the VE table slightly in both directions to find what it liked and the bottom line is that it liked the stock settings and in fact I am not definate that the changes made much of a difference. I felt like either direction made it a tad worse but it may have been because I was expecting a change. If what you are saying is true, then maybe in fact it didn't make any change at all and I just thought it did.

If what you say is true, then maybe you have answered a question from my other thread where I asked why you would ever want to change MAF calibrations.

If the VE tables are only for SD mode, then what table(s) do you tune if your BLM's are showing way rich or lean? The MAF calibration?

So again, what driving/running conditions would be effected by tuning the VE tables? Cold start? WOT? Anything at all not CL?

Thanks for all the help.

STL94LT1

You can also try adding timing in your closed TPS spark advance to help your car's idle. It will clean up the combustion.

To get the car to idle with the A/C on, add IAC counts to the IAC Offset for A/C vs A/C Pressure table. This is a Tunercat table, but I'm sure LT1 Edit has a similar table.

STL94LT1

My car is not running in SD mode, and I changed the VE Tables (via VeMaster) to do my part-throttle tuning. This is on a MAF car, but it's a 94 not a 96. There may be a difference.

MaxLean

The whole VE table debate as to weather it's used in MAF mode or not has been a long debated subject. My personal opinion is that the table is NOT used. When I was running in MAF mode, I found that BLMs were pretty stable with the exception of some decell and idle. Otherwise, light load, heavy load would show about the same BLM. I used the injector constant as a global adjustment to get the BLMs in the 125-128 range. At this point, I found my idle to be in the 135-140 range, but everything else was stable. Considering that I was using a Granatelli MAF I figured it was slightly misreporting the actual airflow at low flow so I tweaked the MAF table only at that range, and all was fine. Just for fun, I ran VE master and started playing with the VE tables. I found that nothing I did made any difference. Later on, I decided to try my hand at a speed density tune. As expected the VE tables had a MASSIVE effect on fueling. No surprise really as speed density mode requires these lookup tables. Anyway, if your MAF is stock (screen and all) then I wouldn't think there would be any reason to alter the MAF tables after you get the injector constant set correctly. BTW, I'm happy to say that after over 38 iterations, I've got SD working pretty well. Well enough that I've removed the MAF and am running SD all the time now.
Scott

MaxLean

Actually LT1 edit does not have this parameter. I own both programs and Tunercat has many more variables than LT1 edit. I started using LT1 edit over seven years ago, but have pretty much switched over to tunercat completely now.
Scott

cerino2000

I am using the tunercat (Jet DST for my 96). I like it. The biggest thing I like it for over LT1Edit is that I get 4 licenses with it and it will work in LS1 world which is something I will move into once I am done with this car. I have to use AutoTap to scan but it does a decent job. Only thing I don't like about it is that it's recording intervals are too wide apart. Needs to collect a little more information.

I spent a few hours creating a conservative timing table that I think is pretty decent. I am going to drive it for a few days and scan it here and there to see how it does.

Thanks again guys for all the help.

Atok

I have mild bolt on mods on my '95. Exhaust and 1.6 RRs. After these mods my trims were off a little mainly at higher RPM (better breathing). I started tuning the VE tables and found nothing I changed made any difference at all. I even went to the extreme, no change to trims.

Then I data logged various engine conditions (load / rpm) and averaged the error relating it back to airflow. I adjusted my MAF calibration table based on the error/air flow and bingo, fuel trims are now pinned at 128 again.

So, it appears to me that the VE tables play a very minor role on a MAF based car. They have no effect on my car.

Here's my MAF table analysis (many samples averaged). Blue line is stock, purple is my adjustment scaling for trim error. This covers from idle to 5700rpm on a clear typical summer day for my car:

Dominic Sorresso

I am assuming you have gone from a 350 to a 383. The cam you are using is small for a 383. I had it in my 350 Xfire and it ran great with tuning. With a Xfire using SD not MAF. Question. Was the Base Pulse Width constant changed in the tune to reflect a 383? Tuning with a WB for 14.7 in O/L won't automatically give you 128 in C/L.