I have a 09 SS TC with the GMS1 hardware, but I copied most of the settings from GMS1 HPT files online. I finally got around to datalogging the car, and noticed the actual boost (subtracting the atmospheric pressure) is limited to 22.4 psi at WOT, and when that happens the fuel pressure is pegged at 2160 psi. I also see the airload at 240% during the same scenario. What I did was find a long stretch uphill and went WOT in 3rd gear. I did the same stretch earlier in 2nd gear trying to do a WOT run to 6k RPM but the front tire just basically went up in smoke whenever I went WOT and the car wanted to go into the shoulder.

Should I limit the torque in 2nd gear? It's set to 100% for all the RPMs in 2nd gear. I didn't seem to have any issues with 3rd gear.

Why is the boost being limited to 22.4 psi? The Desired Airload table was modified. I've checked the other settings and can't seem to recall anything specifically limiting it to 22.4 psi, but it's holding it solid throughout 3rd gear at WOT.

The only thing I saw was the 15 MPa limit for fuel pressure, which is about 2175 psi - close to the 2160 psi I was seeing being pegged when the boost was limited to 22.4 psi. I'm not sure if this is related, and whether I can even increase this fuel pressure limit.

 

I've attached a screen shot. My Maths parameter is Intake Manifold Pressure (SAE) - Barometric Pressure.

I use the same formula for my Taurus SHO with the EcoBoost 3.5L V6 and it is very accurate.

 

Are you trying to blindly tune the ecu? Please go to the hptuners forum and watch the videos on tuning the e69 ecu, you're not logging anywhere near the sensors you need to be.

I'm sure the boost stopping at 22.4 has to do with some not all of ecu parameters being on stock instead of gms1.

 

Also stop going WOT before your engine coolant is to 190

 

It's set to the same settings as the GMS1 tunes. I've been driving it for 3 years without any DTCs. The other forum mentione I need to use Boost Lo Res, so it means I'm running 25.x psi, but I don't understand why it hits almost a limit. I've been using most of the settings described by BYT and other LNF guides. This is the first time really datalogging the car.

 

It is odd, does the LoRes hit a wall also?

Do you have a file linked in the hptuners thread? I haven't gone there to check

 

You have to log the low res because the ecu doesn't see over 255kpa on the map sensor, the lo res is in the lower charge pipe and can read up to 512kpa.

 

So that happens even with both 3 Bar MAPs installed? Boost Lo Res is about 3 psi higher than Intake Manifold Pressure, so it hits the same wall as the other PID. Fuel pressure also maxes out at 2170 psi or so.

I've used the GMS1 files for Delta and Kappa cars as starting points, so all of the MAP and Boost offsets/linear settings are the same. I read some posts about extending the decimal places, but right clicking on the numbers doesn't show that option with VCM 3.0

I haven't received any error codes/DTC's with these settings. But it just seems odd it would hit 25.x psi and not go above it. Normally I'd expect something of a curve.

 

Yes, the ECU has a hard coded limit on the manifold MAP of 255kpa (22.5psi), even with the GMS1 3 bar sensors in there. No matter what value the ECU gets at the manifold MAP, it will only register 255kpa. You must use boost lo res. On my car which was GMS1 when I got it and have now been self tuning with with HPT, the manifold map and lo res sensor read very close to each other in the 200-255 range (typically within 3 kpa or so).

There is no wall with boost lo res. It should register whatever boost you can hit including 30+psi. If you are not getting higher readings I can only think that you are not actually boosting higher than 25psi, or your logging parameters are not set to show higher than that. Not sure why you would want to boost over 25psi though, as there is not a lot to be gained and quite of bit of additional risk (IMHO).

You DAL's are pretty high (straight out of BYT's early guide, I think before the wastegate duty cycle table was unlocked). You can hit any boost you want with just 255 in the high load cell). Your % load being where it is tells me you are probably hitting about 25psi like you think. Your Pressure/rpm factor is limiting your boost at 5000rpm and above. That table keeps boost down in the upper rpm as a limiter. I have mine set to 3.00 to make sure it does not limit boost until 29psi. You have probably seen boost drop off quickly as you approach 6000 rpm because of this. Will hold much better in the upper rpm after you adjust it.

Your duty cycle is high enough. But I don't see your Duty cycle Max which if still GMS1 stock at 95 could be used to get more boost. Be cautious though! I found that as I increased the duty cycle max above 95, it seem to not only allow values over 95 to be effective in the duty cycle table, but even values below 95 created more boost. ie: 90 in the table with 100% duty cycle max value produced more boost than 90 in the table with 95% duty cycle max.

If you decide to just change duty cycle max to 100% for example, I would lower all my high load table values by maybe 15%, then inch them back up to create the boost you want. I did not do that the first time I put duty cycle max higher than 95 and easily hit boost cut at 29psi in the mid range rpm's.

 

And your suggestion to limit torque by gear is not bad. I do not, as I prefer to try with my right foot given there can be vastly different traction under differing road conditions.

But certainly can be used in 1st, and even 2nd gear as you suggest.

I set my boost curve in 3rd gear. So 2nd gear comes in close (maybe 1/2 psi less across the board).

But 4th and 5 gear were arriving at 1 and sometimes 2 psi more than 3rd gear, so I use that table to make sure I stay near my preferred 23psi target, or even a little less since time through those gears is longer. So I have 100% torque by rpm for 1-2-3 gears. And it took low to mid 70's % in 4-5 gears to get it to hold the same boost as 3rd. (all this can be vastly different if your MALT/DAL/Duty cycle tables are different than mine of course).

 

I tried my best to work the throttle in 2nd gear to control traction but it was IMHO almost undriveable trying to accelerate onto the freeway. The torque steer was immense, as it was pushing me into the right shoulder, and I have the factory equipped Quaife torque sensing LSD. I'm going to reduce 1st gear some more and use some limiters for 2nd gear. 3rd gear was fine as that was the only gear I could use to pull some usable data. Other than that, there wasn't any knock retard for the high load / high RPM cells and the engine/turbo sounded good. I also have the K&N SRI that I tuned for about 3 years ago.

 

You should have a smooth and progressive torque limiter. If it is choppy, it often causes Kr.

 

This, all your tables need to transition smoothly or the ecu will show KR

 

Also, for drivability's sake. I have seen some ****, especially in limiting tables, where the jump was so much the car would buck over it lol.

 

For everyones info he has a second thread on hptuners that has some good comments from a few of the senior tuners over there 2009 Cobalt SS TC (LNF) - Boost limited to 22.4 psi??

 

I learned that really quick with the timing and airload tables used to have a light switch let off the throttle and boom -3* snap forward, now it transitions nicely down to -3* I'm sure my clutch likes it a lot better

 

Running a slightly modified version of GMS1, I was able to do some more testing and tuning at the dragstrip. Best today was 14.2 @ 108 mph with a best reaction time of 0.091 seconds (600' ASL, 55F ambient temps). I'm still running the OEM factory Conti's and the traction is terrible. Launch control makes it consistent at least, but its basically a 5000 RPM clutch dump and once it hooks - it just bogs.

The GMS1 seems to push out about 20 psi initially, but tapers off towards 15 psi at 6500 RPM. The combination of the DAL and Pressure RPM tables had the most impact on the actual boost.

 

108 is a nice trap speed. I am guessing your 60' was pretty high to get you a 14.2 time at that trap though.

Not sure how much you changed on the GMS1 but torque limiting tables in it will reduce 1st gear to something in the 60-70% torque range, so that might be why you bog. You can increase those and probably get rid of the bogging. I can roll into it in first gently from low rpm (clutch out already) and it will destroy the tires, so bogging in 1st gear should not be something that happens in these cars. That bogging is likely killing your 60' and therefore your 1/4 times.

Boost drop off to 15psi is extreme and just sounds like the factory tune that is using the Pressure/rpm table to kill boost up high on purpose. It is a limiting table, so you can raise it to maybe just use it as a "safety" table like most do. Set it to 3.00 for example and you can hold boost up top better (at least hold the boost that your DAL/MAL/WG DC are trying to achieve). I am completely stock and can hold 20-20.5psi at 6500rpm (using max of 97% wastegate DC, if you went to 100% it could probably be a bit more boost than I get).

 

Yeah my 60' was pitiful, but even with launch control the tires would spin and then grab at a very low RPM like just under 2k. I did reduce the torque for 1st gear from the original ~58%. Do you run a higher torque (less limiting) in 1st gear? I also reduced 2nd gear to try to reduce wheelspin, but it seems if GM kept 2nd gear at 100% I should have done the same.

I also noticed that the stock DAL had the original 203.xx setting for the high load/high RPM cell (the last cell for 100% torque) whereas the other values all increased by about 15. If we take the DAL values as absolute kPA and account for atmosphere, then that last cell was just under 15 psi at 6350 RPM. I saw the boost drop from 19 psi to 15 psi from about 5000 RPM to 6500 RPM. The Pressure RPM tables allowed more boost as-is.

I experimented with different DAL and Pressure RPM settings and was able to hold about 20 psi through the powerband, but a boost spike in-between shifts set off the overboost at one point and I saw more knock retard as well. I was also flowing more air (about 33 lb/min). During the breaks, I was looking at the data and opted to stay with GMS1 and maybe work on it more for the next track session.

 

Yeah my 60' was pitiful, but even with launch control the tires would spin and then grab at a very low RPM like just under 2k. I did reduce the torque for 1st gear from the original ~58%. Do you run a higher torque (less limiting) in 1st gear? I also reduced 2nd gear to try to reduce wheelspin, but it seems if GM kept 2nd gear at 100% I should have done the same.

I also noticed that the stock DAL had the original 203.xx setting for the high load/high RPM cell (the last cell for 100% torque) whereas the other values all increased by about 15. If we take the DAL values as absolute kPA and account for atmosphere, then that last cell was just under 15 psi at 6350 RPM. I saw the boost drop from 19 psi to 15 psi from about 5000 RPM to 6500 RPM. The Pressure RPM tables allowed more boost as-is.

I experimented with different DAL and Pressure RPM settings and was able to hold about 20 psi through the powerband, but a boost spike in-between shifts set off the overboost at one point and I saw more knock retard as well. I was also flowing more air (about 33 lb/min). During the breaks, I was looking at the data and opted to stay with GMS1 (17-19 psi max) and maybe work on it more for the next track session.

 

Slip the clutch off the line at 3k and try to keep the rpms up. Launch control bogs it to much if it dead hooks.