2009 Cobalt SS TC (LNF) - Boost limited to 22.4 psi??

[metroplex]

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.

[metroplex]

I've attached a screenshot. I used the Maths parameter: Intake Manifold Pressure (SAE) - Barometric Pressure. I also use this on the Taurus SHO with its EcoBoost 3.5L V6 and it is quite accurate for that vehicle (that stock tune is torque limited big time, at "WOT" the throttle blade is only about 50% open)

[cobaltssoverbooster]

no one can help without a tune file.

[cobaltssoverbooster]

according to boost lo res in your screen shot you are 25.35 psi fyi

[MikeM173]

KPA is so much easier to deal with in my opinion. Here it goes though. 1. Are you upgraded to the 3bar map sensors? 2. Have you adjusted your MAP sensor settings for the 3bar sensors if you have upgraded? 3. Have you looked at the max pressure table (I forget the name of the table but I can look it up if need be)? 4. What are your DAL's and Wastegate settings in the max column between 4500-6000 rpm?

[MikeM173]

D*mn it! I missed that reading in that pic. Sorry, I'm on my phone. Atmospheric pressure is usually around 14 if I remember off the top of my head correctly. Which means that CSSOB is correct, you are at around 26psi.

[metroplex]

Where is the Boost Pressure (Lo Res) PID taking the data from? Is this the MAP sensor that is closest to the throttle body? I made a new Maths Parameter and now I'm seeing a max of 26.63 psi as a spike, but it maintains 25.3-25.6 psi.

[cobaltssoverbooster]

the boos lo res is the map sensor located in the cold side charge pipe. it is the sensor used to calculate and control boost by the ecu.
the pid setup you want is ("boost lo res" kpa - 101kpa)

[metroplex]

KPA is so much easier to deal with in my opinion. Here it goes though. 1. Are you upgraded to the 3bar map sensors? 2. Have you adjusted your MAP sensor settings for the 3bar sensors if you have upgraded? 3. Have you looked at the max pressure table (I forget the name of the table but I can look it up if need be)? 4. What are your DAL's and Wastegate settings in the max column between 4500-6000 rpm?

I use PSI because I tend to think of boost in PSI. Worse is that when I'm tuning Ford's EcoBoost engines, they use inHg so I guess that's another conversion! 1 atm = 14.69 psi = 101 kPa, but i use the SAE Barometric Pressure PID and subtract that from the Intake Manifold Pressure PID (or the Boost Sensor Lo Res PID).

Yes, I have the 3 bar MAP sensors and CED harnesses. I actually bought and installed them 3 years ago. I did not get the GMS1 flash done at the dealership though. I just used the GMS1 tunes I found for all of the LNF Kappa and Delta cars.

Here's a screenshot of the DAL and Wastegate settings, and the only thing I could think of being a max pressure table?

[metroplex]

the boos lo res is the map sensor located in the cold side charge pipe. it is the sensor used to calculate and control boost by the ecu.
the pid setup you want is ("boost lo res" kpa - 101kpa)

Cool! That works. I guess it's like Ford's Throttle Inlet Pressure (TIP) MAP sensor at the throttle body (cold side of the charge pipe post-intercooler). Is it ok if I use the Barometric Pressure PID instead of a static 101 kPa? I figure if the actual barometer readings change with the weather, it would affect boost calculations.

[cobaltssoverbooster]

boost lo re (psi) - 14.64 (psi) same pid
baro pid has been known to wander

what are your sensor values...this is why we ask for the file so we can just sift through it

[metroplex]

I believe these are it. I just copied them straight from the GMS1 files I've found in the past.

[MikeM173]

Check your Pressure RPM Factor Table settings.

I still think you are boosting more then you think. From the picture I saw, my guess is, right around 26psi, not 22.4 like you think.

[metroplex]

The calculations look fine (about 2.5 * 14.7 psi) more than enough ceiling for boost?
I'm curious why the boost hits a ceiling at around 25 psi, but the fuel pressure is maxed out at the same point (flat line for boost and fuel pressure).

[MikeM173]

I'm not sure what you have going on in your log honestly. This is why I prefer KPA but again that is just a personal preference.

Find a spot where you are not in boost, so idle.

Should read 94-96 KPA.

Take that number and multiply it by your Pressure RPM Table.


1KPA = .145PSI

96 * 2.550 = 244.8

244.8 - 96 = 148.8

148.8 * .145 = 21.576 PSI

I don't like relying on any calculations that I mix and match in the logger. This is why I leave things specific. The only thing that I involve math with, is my custom PID for LTFT + STFT. Nothing else. I always do the math myself and I always double check it. Maybe I'm wrong though.

[MikeM173]

For the record, it can be higher then 94-96. I usually see right around there though.

[metroplex]

Thanks, I use the barometric pressure pid (14.6 psi during the logging). So the calculations come out to about 22.63 psi which kind of matches what I was seeing. I will sift through the log to see if the boost sensor at idle matches the baro.

But what do I use to measure actual boost, the Lo Res PID which was telling me 25.x psi, or the Intake Manifold Pressure PID which was reporting 22.4 psi? This seems small, but is a big difference regarding what to do next.

What's a safe boost limit for the stock K04 and stock trans?

[MikeM173]

The intake manifold sensor maxes out. Stick with the Lo Res sensor honestly. I'm not 100% sure you have everything set up in your logger correctly, but it's hard to tell without a log to view. As for safe limits, I would stick with 23psi personally. It's not a matter of power, but rather the stock turbo produces a ton of heat that is bad for the motor.

[metroplex]

I looked at the Pressure RPM table and I should be able to max out at about 28 psi at 2800 RPM, but I hit the 22.4/25 psi ceiling at 2800 RPM

[MikeM173]

1. What turbo are you running that you think you can hit 28psi at 2800rpm?
2. If you are looking at the intake manifold sensor, it maxes out and you won't see anything higher.
3. I am 99% sure you are logging something incorrectly.
4. It doesn't look like you are logging much of what you should be logging (this is separate of boost).
5. (Previous post you had) fuel pressure has nothing to do with PSI from the turbo.