Cold Start Issues - TVS Supercharged 2.4 Cobalt SS

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Hey guys,

I have a 2.4L cobalt on E85 with a TVS supercharger (lsj throttlebody, 160# Injectors, intake/full exhaust (catless). A friend tuned the car, but due to the fact he never sees the car when its cold he hasnt had a chance to mess with the cold start symptoms im having.

first id like to say im 99% sure there are no vacuum or boost leaks. ive checked all over and have even removed and reinstalled most of my set up and still had same issues.

On cold start the car will want to idle at 500-600rpm The entire time the car warms up despite having changed the minimum idle speed to as high as 900 at times. Eventually after the car hits the 120-130 degree range the idle begins to surge hard and it will eventually stall the car making it a huge pain in the ass to warm this thing up.

Can anyone shed some light on some changes I might need to make to improve this? or do i have something disabled or conflicting with another table? my ecu has been through a few different tuners and i dont have an exact stock file to reference. two log files attached, in both log files i turn the car on and i dont touch the throttle, any throttle fluctuation is caused by the car

once the car is warmed up the fuel trims are perfect but occasionally it will drop below 500 rpms when coming to a stop and sometimes stall.

Thanks,

Beck

bump. anyone?

Look at your baro reading in your logs, it is 50. Now go through your tune and look at all the baro multiplier tables....Go to the supercharger tab and select not fitted and take another log and it will read correctly. It is looking for a sensor that you don't have. Just pretend that tab does not exist. That is your biggest problem. This screws with a few tables as you will see(you won't even have control of your cam angles). After that you need to dial in your maf in the idle areas.

I had instability at idle on e85 and this method cleared it up very fast: Use the VCM controls special idle. Idle down to as low as it will comfortably go before it gets chunky (about 500rpm). Slowly work your way up allowing a few hundred hits in each cell until you max out at like 12-1400rpm(I forgot). Copy mult %. Do it again by half and again if needed. Now...the important thing is not to touch these maf cells when you are copy pasting % from your driving logs because they are obviously already dialed and you will skew them. Another thing (I can't remember its been a while)lower your min base airflow table after the first maf calibration a little so it is not affecting idle. Since you are commanding an idle speed with the vcm control you will be able to see what airflow amount it wants. Then set the base min table accordingly just slightly below the values you see after your final maf iteration. Set up a histo to log the airflow per rpm to help with that. Sorry thats a bunch of mush if its not clear lmk.

nice ill give it a shot

LMK if your baro reads properly after this. If it still reads 50 figure that out because it is not working properly. Then try fitted again to see if I am right. I had my car tuned by ccss3 and he changed these settings. I explained what was going on and that all I had to do was select not fitted and I got my baro reading back. He said this was the first time its happened and all his tunes are that way for SC setups. I tuned it on my own after that. You may notice a little more KR in your logs because the baro multiplier cuts the attack rate in half so adjust accordingly. The KR comes in very very slow(not safe) if the baro reads 50. I may as well have just pulled my knock sensor off for him.

Its still reading 50kpa so im going to talk to my tuner and see if there is something he may have disabled or altered. weve been tuning the car pretty much exclusively through maf. hell ill swap the sensor and see what happens

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even if i command the car to idle at a specific rpm it wont want to leave 650-700rpm

HHRfreek what map sensor are you using on your car? im using the TMAP sensor from the lsj and wondering if the map is causing some sort of problem. doesnt look like the car has a removeable/replacable Baro sensor any ideas?

Just put in a stock ecu with a stock tune and it still reads 50kpa think there is a problem with a related sensor

Starting to think map isn't scaled properly for the 2.5 bar

you should check everything over before running it further. if you cant command a change and see it then you need to review everything over again before you loose valuable parts like the nice gentleman on here who just lost a lnf engine.

I haven't had that car since 2012, but I recall a lot of it. I had this 2.5bar sensor with iat: http://www.bmotorsports.com/shop/pro...oducts_id/1720

It is not scaled properly in your tune(yours is for 1 bar still). Go to Engine diagnostics>airflow>map sensor. Change linear to 270.59 and offset to -3.30 if you have a 2.5bar. I can't recall if LSJ are 2 or 2.5. That should at least get you close. I got that info from the forum somewhere when I installed it.

okay well now im getting baro 99kpa which sounds right because im right about at sea level (using same 2.5 map sensor as you). car still idling and running a little funny and still no idle control with vcm scanner. baby steps!

Hhrfreek you by chance have a copy of your tune file from The hhr I can take a look at?

PMd. Also if you don't mind checking just to clear up the SC fitted/not fitted for baro reading.

youre correct. when i fitted the supercharger it went back to 50kpa baro reading. when i unfitted the s/c it went back to 99/100kpa

Couldn't attach the hpt file in my email for some reason so I just put it out here.

Attached is probably one of the last iterations I had on my HHR. It appears I may have been testing some things now that I look at it so don't just throw any settings into your tune necessarily, though I know this was perfectly drivable and after I had my idle dialed in(I usually made drastic changes so I could see how it changed things to better understand). This was with a 2.6"M62, lsj tb, E85, 80s, exhaust, cams, ported head. Hopefully you figure out the VCM controls for idle. I could not do it any other way it was just touchy. Do you have an aluminum flywheel? I did and I think it made tuning harder to dial in at idle. I think the heavier stock flywheel provides a little more stability. Try some other VCM commands to see if they are working. Look at my throttle body settings. It could just be your percent max being 1%. Raise it to see if you can idle higher.

I lowered my base running airflow below what the maf showed at idle. Then made VCM commands and dialed in the maf. This made the biggest impact on idle quality. After you are done with the MAF, raise the base table back up to what you logged at those rpms. Also you may want to see how it responds to more spark at idle and repeat. Look at the adaptive idle settings after this if needed, proportional, integral airflow/error and the idle settings on the spark table overspeed/underspeed. You could end up with values far different than mine. Make drastic changes to see how they affect idle stability and adjust your tables.

Any progress?