Cammed LS1 idle hunts at stoplight

[detroitmuscle07]

Hello everyone,

I'm looking for some advice on how to resolve the idle hunting that I'm experiencing on my cammed M6 ls1 C5 vette. When I come to a stop with the gear shifter in neutral the rpms will sometimes drop to 400 then raise to commanded 850 and back down again before it settles . I also notice that the AFR drops down to low 12's as well. The car was tuned by a local tuner that is no longer around and I'm pretty satisfied with the cruising and PE portions of the tune. I currently have a friends Flashscan V2 and have been familiarizing myself with it's functions. Can someone please offer some tips? Is it spark related perhaps? Please see list of mods and current tune below. Thanks a bunch! -Josh

-227*/231* 6xx 6xx 111lsa cam
-Longtubes
-Catless exhaust
-LS6 intake
-Blackwing filter

[joecar]

Post log files.

[detroitmuscle07]

Please see attached log.

[statesman]

The car was tuned by a local tuner that is no longer around

After looking at your tune file, I can fully understand why this tuner is no longer around.


Can someone please offer some tips?

Yeah, I'll offer you some tips...

The tune file you posted is not a good tune. Don't think that changing one or two parameters will miraculously fix the issues you're having.

If you want to fix this yourself, then you need to learn how to tune... and it can be a really steep learning curve if you've never tuned an engine before, so you need commitment. There are plenty of resources to help you along, both here and on other tuning forums... but it's up to you to spend the time reading and learning.

If you don't want to put in all the effort of learning how to tune... then find someone who actually knows what they're doing and pay them to fix it properly.

This might sound a bit blunt and it's probably not really what you want to hear... but that's just the way I am. :beer:

[detroitmuscle07]

Thanks for the reply. I'm definitely willing to put in the effort to learn. Can you please be specific about some of the things that you consider "not good" with the tune? Thanks again.

[statesman]

Okay, if you really want to put the effort into learning then the first thing I would suggest is for you to download a stock file for your car. The member "gmperformancecentre" has posted a dropbox link to stock files... go find it. I could put a link in here for you, but you need to learn to find things for yourself in this site. Then compare a bone stock C5 tune with the tune you have now (there is a compare feature in the tuning software).

When doing a compare, a few things really stand out to me. The first is the MAF curve. It hasn't been tuned, it's been hacked. From 1500Hz to 3500Hz the stock curve has been bumped up by 27%. From there to 7000Hz it's been bumped up by 14%. From there up to 7750Hz it's been bumped up by 12% and the rest of the curve has been bumped up by 9%. This is not how you tune a MAF curve... this is a quick and nasty hack. All this does is fatten your fueling up and if you look at the log you posted, you'll see the crazy negative trims created by this hack.

Then I looked at your VE table... this has just had a bit of smoothing applied... it's almost certainly not tuned for a cammed engine.

Then I looked at your spark.... only WOT has been tuned, part throttle spark is completely stock.

Then there's some really crazy shit, like he's made a random adjustment to {B4308} Airflow Parked. There are very few people who know what this table actually does and how to tune it... he should never have adjusted that table. You should put that table back to stock.

I know that your issue is with idle hunting but I would suggest you get your fueling right first... then move onto idle tuning.

[detroitmuscle07]

Wow! I'm a bit disappointed to say the least. I'm currently studying calc.vet and it's effects. Would you recommend this process as a solution?

[statesman]

Yep... do a calc.vet. It will correct MAF and VE at the same time. Read the instructions very carefully.... use only as directed. Make sure you put yourself into 'MAF only' mode when doing this.

[detroitmuscle07]

I've spent that last few hours trying to set-up the calc pids to begin calc vet. Both calc.ven and ext.wo2LAM1 are coming up as "invalid pids" in the scan software. Also, both maps (calc.vet and calc.selben) do not seem to be functioning correctly. it appears that they are just creating a cell count rather than any useful data. My calc.vet map does not have the correct "Col labels" regardless if I copy Main VE table data displayed in PSI or kPa. It begins with 2.2 and ends with 15.2 instead of what is required by the tutorial. I've copied the calc pids text into the V7.5 text file as instructed. I do not see in the tutoral where I am required to go "MAF only" either. Please see the attached log. Thanks!

22761

[detroitmuscle07]

I increased the precision on the calc.selben map and was able to get useful data. Calc.vet is still displaying data as 0 even after I made sure that I was logging in metric (kPA) and got the correct "Col labels" information per the tutorial.

[statesman]

I did tell you that it was a steep learning curve.

[joecar]

Post some screenshots.


That spark table has too much advance, that's easy to increase advance to make a little more torque, but at the expense of knocking.

[detroitmuscle07]

I've seemed to have figured it out. The fuel trims also seem to be in a more reasonable position. I'm not currently seeing any KR, but I will take the advice and work on correcting spark next. Please take a look at my most current log and see what you think.

22772

Please see my most recent tune file as well. 22773

[statesman]

I've seemed to have figured it out.

Setting things up can be a bit hard when you first start out... but you've got it happening now.

Fueling looks a lot better now. If you're happy with the fueling, then move onto idle tuning. There's a lot to learn with idle tuning, so take your time and do the reading and learning before you attempt to deal with your idle surge.

I will give some handy hints...

Make sure your desired airflow and actual airflow match... if you've got drive by cable, then correct the IAC effective area table by shifting the entire table to make the airflows match.
Don't assume all surging is airflow related... sometimes spark can be contributing to it.
Log all the airflow pids... it will give you better insight into what's actually happening when you get a surge.

Joecar is right, you appear to have too much spark advance... but I have personally seen engines which have carried more spark than you would normally expect, so just make sure you always log for KR and don't worry too much about it if you're not getting any knock.

[detroitmuscle07]

Thanks again gentlemen. I'm pretty satisfied with the current fueling. May do a few more logs and see if I can clean it up some more. I'm looking into the idle tutorial material now.