Autocross STX tune?

[jboogie67]

the disclaimer > HPT noob here very limited FI tuning knowledge other than some SAFC stuff.

So, I'm building my 09 cobalt ss for STX class in autocross. This allows tuning to the ECU. But, not to alter the boost. With the allowed mods I can do an intake and full exhaust. I guess I can adjust,rev limiter, ignition timing, cam timing to help spool a little quicker. As I understand it the way you guys get around the "learn down" is my adjusting the desired airload, and adjusting the desired airload would increase boost.

"Boost changes indirectly resulting from
allowed modifications are permissible, but directly altering or
modifying the boost or turbo controls, either mechanically or
electronically, is strictly prohibited."

So, there's my delema. Is it worth tuning at all without increasing boost? Ideas? comments?

[Jaxon]

Leave the dals, do they mean stock 16psi boost or just what ever is limited, say 13psi down low? You could add timing, cam timing, torque limiters, air to fuel. Alot of things can be changed other than boost itself.

[jboogie67]

but isn't the way the learn down works is by the stock tune commanding a certain desired air load? so would any gains from timing and other areas be pointless cause the computer would reduce boost to compensate?

[Terminator2]

but isn't the way the learn down works is by the stock tune commanding a certain desired air load? so would any gains from timing and other areas be pointless cause the computer would reduce boost to compensate?

Yes. It will still make more power than stock by changing the PE lambda and timing. Should make 20 whp more than stock easily on the same boost level.

[jboogie67]

hey, thanks term time to add HPT to the list of things to buy before spring.

[tommyk]

I know this is an old thread, but jboogie and I have talked about this STX tune on cobaltss.net. I am nearing my purchase of HP so I can legally run in STX as I currently have the GSM1 tune. So I have a few questions about doing this tune as well.

1. If we make a tune that leaves air load the same, isn't the learn down just going to stop the gains?

2. How much gains can really happen while leaving boost the same? I realize its not all about adding power.

3. Can we get the turbo to spool up and have a lot more power down low in the 1500+ RPMs?

4. If the learn down feature stops more power, can we load the base GSM1 OS / tune that does NOT have the learn down feature and setup the base air loads from the stock tune to achieve the same boost while not having the learn down?

Sorry if these questions are dumb, I am also a total newb about tuning but I want to learn!

[shabby]

1. not sure if the learn down feature monitors other factors like ignition and cam timing, you might see some gains changing those parameters
2. no clue, you're gonna have to do some test and tuning and look at the logs to see if you notice any difference
3. the turbo doesn't spool at 1500rpm, especially not in 1st and 2nd gear, maybe 5th.
4. who said the gms1 tune doesn't have the learn down feature? its still there

[tommyk]

1. not sure if the learn down feature monitors other factors like ignition and cam timing, you might see some gains changing those parameters
2. no clue, you're gonna have to do some test and tuning and look at the logs to see if you notice any difference
3. the turbo doesn't spool at 1500rpm, especially not in 1st and 2nd gear, maybe 5th.
4. who said the gms1 tune doesn't have the learn down feature? its still there

So does HP have a different base file that removes the learn down feature? How are people achieving 400+ HP?

[shabby]

No, that's simply how the ecm functions, it has a set of parameters and its supposed to stay as close to them as possible. That's why when you add a downpipe and intake you basically see no increase in power, if you want more power you simply change those parameters.

[jboogie67]

I havent been playing with my STX tune to much, the high boost tune is just to much fun to resist I can tell you 22* of timing up top (vs 10* stock) really makes a HUGE difference and the 7k rpm redline has made a big difference also. I'll do a 60-100 run with it soon and report back.

[Leafy]

Take that 22 psi peak boost you get with GMS1 and make it hold it for as much of the RPM range as possible. That way you are not increasing boost. Throw some e85 in there and crank the hell out of the timing. Then if you're daring figure out cam timing.

[jboogie67]

Take that 22 psi peak boost you get with GMS1 and make it hold it for as much of the RPM range as possible. That way you are not increasing boost. Throw some e85 in there and crank the hell out of the timing. Then if you're daring figure out cam timing.

Can't legally run the gms1 cause its a dealer option not a factory. Can't touch the dal or wg tables at all. Now I just need to tinker with these etc tables to get rid of this delay. Tips anybody?

[Leafy]

I need to study the rule book again. I thought that if it could be bought on the car installed then it was a legal trim package.

[jboogie67]

Has to be installed from the factory not the dealer. It would be like adding a trd supercharger to a scion and still running h-stock

[Wangspeed]

I havent been playing with my STX tune to much, the high boost tune is just to much fun to resist I can tell you 22* of timing up top (vs 10* stock) really makes a HUGE difference and the 7k rpm redline has made a big difference also. I'll do a 60-100 run with it soon and report back.

You're not trying to run 22* on 93 are you? 93 will usually only take 14-15*.

[jboogie67]

You're not trying to run 22* on 93 are you? 93 will usually only take 14-15*.

Yup, and have never seen any knock up top. I'm gonna keep going up and see where it starts showing KR then back it off a degree and go real conservative on the IAT vs spark table to be safe on track.

Are you talking about up top or at the torque peak? Even with my full boost street tune I'm at 18* from 6k rpm up. You guys must have terrible gas up there.

[silverbullet08]

some one made a thread about a autocross tune a while back. I believe the results were just slightly added timing from stock due to high EGTs and the constant on and off the throttle causing knock after a few laps "on 93 gas". Run a 50/50 E85 tune at about 18*-20* and you should be safe especially at lower boost levels. you can gain quite a bit of power from cam timing. There is a thread here with a lot of good tables in it to test out. Just getting the fuel trims dialed in right will make the car more responsive and net you a few more hp in certain areas plus it will help keep knock down. If they get out of wack these motors will show kr. A .88 lambda PE is a good AFR to stick with. Some people will say its rich some will say thats lean, but that area is where most people have had good luck including myself. take it to the track and log a entire session from start to back to the pits. Make sure your logging all the correct perameters and go from there.

[Leafy]

I think that was road racing. With auto-x you make about a 1 minute run and then the car gets to cool off for a while.

More spark advance should lead to lower egt's not higher ones.

[Wangspeed]

some one made a thread about a autocross tune a while back. I believe the results were just slightly added timing from stock due to high EGTs and the constant on and off the throttle causing knock after a few laps "on 93 gas". Run a 50/50 E85 tune at about 18*-20* and you should be safe especially at lower boost levels. you can gain quite a bit of power from cam timing.

You're confusing issues. We're talking about ignition timing, not cam timing.

I mentioned before that the car won't go more than a minute or two at almost constant WOT on a typical street tune before it starts knocking. I backed my tune off considerably, but still had to splash it with 3 gallons of 100 before it would completely stop. Still makes more power than GMS1. I'd estimate that it's somewhere near 290-300whp.

[tommyk]

You're confusing issues. We're talking about ignition timing, not cam timing.

I mentioned before that the car won't go more than a minute or two at almost constant WOT on a typical street tune before it starts knocking. I backed my tune off considerably, but still had to splash it with 3 gallons of 100 before it would completely stop. Still makes more power than GMS1. I'd estimate that it's somewhere near 290-300whp.

So are you saying you make 290-300whp on stock psi / modified stock tune?