255 limit NOT present on 2009 Cobalt SS?

[GTPprix]

Ok Guys here is the situation:

I threw a catless downpipe on my Cobalt SS about 20 minutes ago and went out to do some testing (forgot the laptop; doh!). Anyhow my car normally would spike 21-22psi and settle at 20psi very quickly, AFTER the catless DP I'm seeing 24.5PSI spikes on my RPD (Which reads its data RIGHT off the bus). I was under the impression that if pressure went OVER 255 it wouldnt register on the RPD since the ECM supposedly wasnt capable of measuring this.

Am I on crack here? I need to dial the boost back LOL

[GTPprix]

Ok a little update, I just re confirmed my previous findings:

The RPD is DEAD on with the HPT boost measurements until it goes over 22.5 or so. The RPD continues to read but HPT sees that 255 KPA ceiling. I've attached a BRIEF log, not sure what the KR is about as I normally dont see any and this was the first quick pull after a flash. On the log where you see 255KPA I was seeing 24.5-25.1 PSI on the RPD, I guess I might need to sniff it to see what data the RPD is looking at :\

Any thoughts on this or how to reduce the spike to 24? Also didnt someone say anything over 255KPA throws a code or makes it go into reduced power? My car doenst do that... Is there something in this 2009 OS?

[shabby]

I'd lower the airload in the 2500 and 3000rpm cells and see if that fixes the spikes.
This isn't the first time that someone mentioned that they're seeing over 23psi, even the dic shows that for some people.

[fr0stb1t3]

I'd lower the airload in the 2500 and 3000rpm cells and see if that fixes the spikes.
This isn't the first time that someone mentioned that they're seeing over 23psi, even the dic shows that for some people.

Does anyone have any clue why? I often see 25psi on the DIC.

[GTPprix]

I'd lower the airload in the 2500 and 3000rpm cells and see if that fixes the spikes.
This isn't the first time that someone mentioned that they're seeing over 23psi, even the dic shows that for some people.

I'm going to work on that tomorrow, I was thinking the same thing as it seems like turbo surge :\ I gotta wonder how high this thing is really going, I thought it was supposed to throw a code and such when you hit over 255? I've been pegging it LOL

[PSYKOSTEVO]

Yeah, control the boost with the Max Airload Torque table.

[GTPprix]

Thats what I've been doing, I just spent too much time screwing around trying to find out how this thing was on the bus seeing ~25PSI :\ Veeerrrry strange LOL

[Baldturbofreak.com]

If you can boost above 255kpa for more than 5 sec continuous then Im really curious too...

[GTPprix]

Is 5 seconds how long it takes to trip the code? If so I guess I could crank up my DAL and see if I can get it to hold it longer than the brief spike. The wierd thing like I said is where is the gauge getting the data, the RPD reads right off the bus, so there is a PID somewhere for boost that doesnt top out at 22.48; wierd eh?

[Baldturbofreak.com]

Im almost 100% sure the Tmap in the CBSS's are 3 bar due to the fancy pillar guage and what not.

[Programmer]

If you can boost above 255kpa for more than 5 sec continuous then Im really curious too...

Relook at the posted log...the whole log was only 8 seconds...boost spike was around a half second. I've attached a log (wmeth) from last spring on a 2008 Sky.
Note boost 255 kpa and airflow on this one.

Then check this one...note lower boost and more airflow. 12.8 second pass.
2007 GXP. This was from 2007 summer...
Old logs...

[Chris@HPTuners]

i need to look at this again, it seems the PID is limited to 255 kPa, but i'm starting to think the internal code limit might have been changed to 512 kPa for these engines. If it is, you guys might be able to have some serious fun after all!

[fr0stb1t3]

i need to look at this again, it seems the PID is limited to 255 kPa, but i'm starting to think the internal code limit might have been changed to 512 kPa for these engines. If it is, you guys might be able to have some serious fun after all!

Hmm... Is this one of those things that is relegated until after dodge, or one of those things you're going to use as a distraction one day

[Chris@HPTuners]

Hmm... Is this one of those things that is relegated until after dodge, or one of those things you're going to use as a distraction one day

we'll see, i've got a long flight to the US next week so maybe i'll get something done.

[GTPprix]

Relook at the posted log...the whole log was only 8 seconds...boost spike was around a half second. I've attached a log (wmeth) from last spring on a 2008 Sky.
Note boost 255 kpa and airflow on this one.

Then check this one...note lower boost and more airflow. 12.8 second pass.
2007 GXP. This was from 2007 summer...
Old logs...

Yeah I didnt really have time that day to screw around with it, I was just suprised to see something registering over ~22.5 that was read from the bus thats all

Im almost 100% sure the Tmap in the CBSS's are 3 bar due to the fancy pillar guage and what not.

That would make sense although that would also mean the ECM can handle at the very least the output (hopefully more? )

i need to look at this again, it seems the PID is limited to 255 kPa, but i'm starting to think the internal code limit might have been changed to 512 kPa for these engines. If it is, you guys might be able to have some serious fun after all!

Yes you do!! Take a break from that Dodge stuff and give throw the angry LNF Mob a bone to keep us occupied till you get the Dodge stuff done. Dont forget us

[oldskool]

Does anyone have any clue why? I often see 25psi on the DIC.

With my first generation tune I was also seeing 24-25PSI spikes on the DIC, it was there and gone in like half a second. I've since tuned it out; I'm not a big fan of spikes. But it is a rather large development if the internal code limit has been changed.

[Baldturbofreak.com]

If the internal code is now 512kpa....IM COMPOUND TURBOING!!! lol

[Chris@HPTuners]

i need to know if it is overboost protection that is causing problems. P0234.

as much detail as possible with as many boost related params in a scanner log would be great. I'm making progress and so far everything looks to be 512kpa max in the code.

it could also be a throttle related test that is causing things to shutdown.

eg. if you hold the wastegate closed what happens?

sorry if you posted this info before, but you need to spoon feed me

[Baldturbofreak.com]

The throttle is the next place the PCM fights the requested airmass deviation (if you have a boost controller)

If the PCM sees overboost 0234 for over 3 seconds continuous or 50 sec cumulative since key on it reduces the throttle to 41% and removes all duty cycle from the boost solenoid.

I can dig up a log for you, I'll look after I make coffee.

Here we go. Goes limp at 5390 in the log

[GTPprix]

After I get my charge pipes and other mods on (hopefully later today) I'll dial up the DAL and see if I can get it to trigger. Also Chris if you get time on your flight I realize this is trivial comparitively but I REALLY need some sort of COT control be it Activation temp or a simple 1/0. This will make tuning ALOT easier for me on the dyno since I've got no cat anyhow and I hate playing with that crazy COT table LOL