warm start up issue

[mbtecalley]

I'm having an issue with warm start up on this 06 TBSS, 630 lift cam, intake, headers/full exhaust, edlebrock intake manifold, mild head work. On cold starts it fires up great, but it seems like once it starts to get a little heat in it it tends to hesitate with a slow rise in rpm on starts even just a few seconds after the initial cold start. I've smoothed out and gotten rid of the negative values in the cranking spark table and have been adding to the cranking fuel in the warmer ECTs. It has seemed to have gotten slightly better, but i cant help feeling like I'm missing something or possibly having a fuel pressure problem. I plan to connect a fuel pressure gauge to monitor while cranking to eliminate that possibility. I've attached 3 start up logs and my most recent tune file. Any input would be greatly appreciated.

caps startup 2.hplcaps startup idle 4.hplcaps startup 3.hplChevy Trailblazer SS 06 Caps Garage 630 lift cam edlebrock intake minor head work idle partial t.hpt

[jsllc]

Your vehicle starts in Open Loop. Once ECT is above 131 it switches to Closed Loop. On subsequent warm starts it will wait 10 seconds after start to switch to Closed Loop. Your MAF is off causing the STFT to add 13-18% and LTFT are turned off. You need to FIX the MAF soon. Took a look at MAF someone has messed with the cells used at idle. You are using a MAF only tune so with the MAF calibration off your will have issues.

[5FDP]

The VE table looks way different than stock too, even though you have it running off the MAF it seems odd that it would be that drastic of a difference down low in the VE.

Kinda to go with what he said above, the start up and running commanded AFR at the beginning is like 12-13afr but your wideband is already bouncing around 14-15 if it's correct. Showing that fueling is pretty far off there.

[mbtecalley]

The VE table looks way different than stock too, even though you have it running off the MAF it seems odd that it would be that drastic of a difference down low in the VE.

Kinda to go with what he said above, the start up and running commanded AFR at the beginning is like 12-13afr but your wideband is already bouncing around 14-15 if it's correct. Showing that fueling is pretty far off there.

This truck was at another shop where they started to tune it and then it sat for about a month. I honestly hadn't even looked at the VE yet, but yes its way off. I will get the MAF scaling straighted out at idle and update. Thank you both for the advise!

[jsllc]

There are other issues in this tune. Compare to stock and replace with stock values when in doubt. If it were me i would figure all of the build changes, start with the stock OS make my own mods and go from there.

[mbtecalley]

There are other issues in this tune. Compare to stock and replace with stock values when in doubt. If it were me i would figure all of the build changes, start with the stock OS make my own mods and go from there.

Yea, knowing someone else was in there, that's what i should have done to begin with.

[mbtecalley]

I replaced most the values back to stock and started fresh. Ive only begun to work on start up and idle but it seems I'm now on a better path

[jsllc]

So add injector tip temp to log. +2% across the board on MAF and run it. It all looks okay but need way more data. If AFRs stay below 15.5 keep going. Stay out of PE as much as possible. When you get ready set PE to 1.225 (12) to start safe. Really should not go above 12.5 on a car being pushed hard with a tune that is accurate across the board. Until the MAF is hitting commanded everywhere and you have SD down keep PE rich.

[mbtecalley]

So add injector tip temp to log. +2% across the board on MAF and run it. It all looks okay but need way more data. If AFRs stay below 15.5 keep going. Stay out of PE as much as possible. When you get ready set PE to 1.225 (12) to start safe. Really should not go above 12.5 on a car being pushed hard with a tune that is accurate across the board. Until the MAF is hitting commanded everywhere and you have SD down keep PE rich.

what exactly am i looking for in the injector tip temp? I ran it and made some maf changes at partial throttle. however now i am having cold start issues having to give it throttle to get it to start. when cranking its only getting about 15.3% throttle and wont fire until i open it to about 35% with the pedal, Ive tried making subtle to drastic changes in the colder areas of the start up airflow table with no change in throttle percentage when cranking.

[mbtecalley]

I did notice that on the warm start up from the first log the injector tip temp was at 32* and slowly rose. However in the second log on the cold start up it jumped from 32* to 75.2* in a matter of about .2 seconds which seems unlikely.

[jsllc]

It is a chicken or the egg thing. They affect each other. Most cars seem to run 122 - 131F on injector tip temp. I pick one as my zero cell. In my case it was 122F. If you zero all of these (VERY BAD IDEA) the cells below will get progressively richer the further away from 122 and the cells above will get progressively leaner. Every car will run much hotter after heat soak. Do not be surprised to see injector tip temps of 165F+ after a car was sitting on a hot day. This table is an injector pulse width adder so usually below 122F they are minus values and above they are positive values. Now for me ... all of this "close enough is good enough system" is how hard you want to work at it. My cars I try to be within 1-3% under ALL environments. Anyone that says they do better is yanking your chain. This is not possible for cars tuned for customers. They will not pay for the 100 hours it takes to do this. I am no engineer but am a CS major with a mathematics minor so i can work the math and logic pretty well. Once I have good (not great) injector tip table I work on the MAF and filter so that MAF values only are populated +-10F of 122 injector tip temp. ESPECIALLY if WOT and PE.

When you log the inj temp it will work up from cold. I run until it starts filling in all the way through my zero cell (in my case 122F). This is done at a constant RPM with NO throttle change so you do not have to worry about transient. You can use the controls section to force the car to idle a 1000 or 1100 to move the process along. I put those in Excel and subtract the value found in my zero cell from all those below. Then reflash the car with these values. This will force a very hot inj temp. Log and it will walk its way down to 131 take the value you had for 122 from the previous log and subtract it from all the values above. this should give you a pretty good table with just a couple of tries. The value from your zero cell is how far the the MAF is off at hertz value. Once you are happy with the values one above your zero cell and one below your zero cell and the rest are safe (not going lean) tune your MAF and SD/VVE.

I always do MAF first on GM because that is how it supposed to run plus I have formulas that build SD/VVE from and accurate MAF.

Cut and past from the other threads where I have posted this.

[mbtecalley]

It is a chicken or the egg thing. They affect each other. Most cars seem to run 122 - 131F on injector tip temp. I pick one as my zero cell. In my case it was 122F. If you zero all of these (VERY BAD IDEA) the cells below will get progressively richer the further away from 122 and the cells above will get progressively leaner. Every car will run much hotter after heat soak. Do not be surprised to see injector tip temps of 165F+ after a car was sitting on a hot day. This table is an injector pulse width adder so usually below 122F they are minus values and above they are positive values. Now for me ... all of this "close enough is good enough system" is how hard you want to work at it. My cars I try to be within 1-3% under ALL environments. Anyone that says they do better is yanking your chain. This is not possible for cars tuned for customers. They will not pay for the 100 hours it takes to do this. I am no engineer but am a CS major with a mathematics minor so i can work the math and logic pretty well. Once I have good (not great) injector tip table I work on the MAF and filter so that MAF values only are populated +-10F of 122 injector tip temp. ESPECIALLY if WOT and PE.

When you log the inj temp it will work up from cold. I run until it starts filling in all the way through my zero cell (in my case 122F). This is done at a constant RPM with NO throttle change so you do not have to worry about transient. You can use the controls section to force the car to idle a 1000 or 1100 to move the process along. I put those in Excel and subtract the value found in my zero cell from all those below. Then reflash the car with these values. This will force a very hot inj temp. Log and it will walk its way down to 131 take the value you had for 122 from the previous log and subtract it from all the values above. this should give you a pretty good table with just a couple of tries. The value from your zero cell is how far the the MAF is off at hertz value. Once you are happy with the values one above your zero cell and one below your zero cell and the rest are safe (not going lean) tune your MAF and SD/VVE.

I always do MAF first on GM because that is how it supposed to run plus I have formulas that build SD/VVE from and accurate MAF.

Cut and past from the other threads where I have posted this.

Are you talking about the Normal ECT table under Fuel > Injection Timing?

[jsllc]

No offset vs injector tip temp ECM 12303

[mbtecalley]

I'm not 100% sure im understanding this properly, but it sounds like i should set up a graph that matches that table and log afr error in those cells at a steady 1100 rpm

[mbtecalley]

also i believe i forgot to mention it has fast 33lb injectors

[jsllc]

Actually no it is different. It is a pulse width modifier so I do in ms.