Cobalt SS SC Low Boost Pressure

[Rush]

Over the winter I installed a GM Stage2 kit along with a 2.8" pulley; however no matter how hard I try the boost pressure never goes over 15PSI.
I recently had it dyno tested and had my datalogger hooked up and it showed boost just barely hitting 15PSI and only for about a second. Consequently the performance on the dyno was barely better than stock, only 4HP better. Any ideas what may be the problem?

[dont_blink]

Your motor is toast. Do a compression test. Also, with my 2.8" pulley I barely see 15psi at all with the headwork and header I have on there. Read my words, follow them, live by them, understand them:

MORE BOOST DOES NOT MEAN MORE POWER.

Boost is pressure entering the motor because the air isn't making it's way through quick enough. So a car running a 2.8" pulley making 14psi is probably significantly more powerful than the same car running a 2.8" pulley and making 16psi. All things being equal of course.

Also, where are you reading this boost from? The stock boost gauge is not accurate, get a real manifold line driven gauge.



Also, other supporting mods and your tune/log files would help. I assume you have the tune/log files that you pulled with your HP Tuners software if you're posting in this forum?

[Rush]

I created a PID as described in the help file, which is MAP converted to PSI and air pressure at sea level subtracted from it, I also corrected for altitude which at 4000ft is about 2PSI less air pressure or 2PSI more boost. My boost gauge and this PID seem to be very close to each other.
The only mods are a Stage2 kit with a 2.8" pulley and a K&N Cold Air Intake.
I have a log file from the dyno test, that I'll upload later since I don't have access to it from here.

[Rush]

What kind of compression should I get from an Ecotec engine?

[Baldturbofreak.com]

A leakdown test would be better.
But if compression is all you have then just make sure they are all within 5% of one another.

[Rush]

Attached is the log file from my dyno pull. This was a pull for my mod to GM's Stage2 tune, it never reached peak power at redline it was still producing power; it hit 209 at redline. The GM tune peaked right before redline at 207HP. I'm having trouble uploading the tune files, I'll have to try again later.

[DWK5150]

209 is it? You did have your dealer flash your PCM right??

[dont_blink]

Your idc should be nowhere near 100% on 42lb injectors, even with 2.8 pulley. Post up your tune also. You also should not be knocking at only 9 degrees advanced. Did you have a wideband for your log? Your timing flatlines at 16 degrees, should be closer to 19 or so without methanol. You're losing a decent amount of power right there. As far as only running about 13psig (190kpa), I'd look at the blower or the rings. By 2200rpm you should be making an easy 10psi. Are you sure they even changed the pulley and put in bigger injectors? Lol. That looks like a pretty stock scan to me, aside from the ridiculous knock. Are you sure they didn't do Stage 1?

[Rush]

DWK5150: Yes the dealership flashed it and I downloaded the PCM before and after to verify it. However whether GM gave them the correct file to upload, who knows.

[Rush]

don't blink: What's "idc" I don't have access to my software at the moment to see what that is? As far as Stage2 and the pulley, the parts I did myself so I know they were changed; I had the dealership do the flashing to Stage2 and I even asked the tech if it was both Stage1 and 2 and he said it was; however I think whatever GM gave him is what I got, it might just be Stage1 and not 2 or vice versa. The place I had it dyno's at put a wideband in the tailpipe and I think around 3800RPM it hit 11.2:1 and stayed there, I'd have to look at the printout they gave me to verify this, but I think it's about right.

[DWK5150]

Need to see the tune and your configure file to make sure you have hpt set up right. Idc is injector duty cycle. Do a compare of your original tune and your existing one to see what us different if anything between the two.

[Rush]

I did that back when the dealership did the supposed Stage2 upload and there was/is a difference. Attached is that upload. This is not the one from the dyno test, the only difference between this one the the dyno test config is that I increased fuel by 8% in the MAP Freq/RPM (I think) and under PE I changed the curve at the peak from 12.5:1 to 12.0:1. I don't have access to it at the moment or I would attach it as well.

[dont_blink]

11.2 is spot on for a GM Stage 2 tune. If it was a Stage 1 you wouldn't have got new injectors to install. What size does the pulley say it is?

[Rush]

The kit was a full Stage 1 and 2 kit, but I'm not sure what file GM had the dealership install, stage 1, stage2, or both? The pulley came from cobalt-addiction.com and says 77.9mm on it which is what the GM Stage2 pulley says, however it is smaller than the GM pulley, because I compared them before putting it on.

[PSYKOSTEVO]

11.2 is spot on for a GM Stage 2 tune. If it was a Stage 1 you wouldn't have got new injectors to install. What size does the pulley say it is?

Other way around. Stage 1 is injectors only. The stage 2 is pulley and those injectors. The tune is 100% the same.

[SJSchafer]

Your cat is toast.

[dont_blink]

Boost would be higher if his cat was toast........

[SJSchafer]

If it was clogged it would go up. Just trying to think of what would cause that kind of a drop. At his elevation with a 2.8 he should be running about 17 psi of boost. He's loosing about 2 psi. That's about what you would lose from a catless DP. Now consider his injectors are static and look at his cat temps spike at WOT. Just guessing really. Not a CAT expert really. Fuel is my gig.

[SJSchafer]

Yea, by looking at your log again, your MAF and VE isn't far off for 4000 ft. As for the loss of power, its your pulley and your tune. You're running pig rich untill PE then your spiking lean causing knock. Typical stage 2 injectors and tune with small pulley. Get bigger injectors or a bigger pulley. Then go get a WB and go from there.

[Rush]

Based on a suggestion from another forum, yesterday I pulled my supercharger out and checked to see if the bypass valve was sticking open, it was not. By default it is in the normally closed position. The bypass control valve (not part of the SC) was relatively inexpensive so I went ahead and replaced it. The two attached files are with the vacuum hose attached and unhooked, with the hose unhooked the valve should remain closed all the time. However I'm still getting less boost than when I first installed the stage2 kit.
The only things I can think of are (1) my SC is toast, (2) the bypass control valve actuator is unable to hold the valve shut under load and letting air pass it (a $220 part), or three as someone suggested earlier in this thread, my engine if toast.
Question what is the max values the TPS should hit, my maxes out at 88%?