LNF: What max PSI are you running with stock turbo?

[lundy4137]

A little background before I get into things. I recently bought HPTuners about a month ago to tune over top my GMPP tune and down the road tune to some upgrades. So I am new to tuning. I watched and followed the how to videos from cobaltssoverbooster to get set up. My plan is to go through and disable torque management, spark advance, boost and MAF calibration in that order. I disabled torque management per the videos and did a base run before I try to add spark advance.

What I found is that I am already registering a fair amount of KR. I already removed some advance to get those numbers down. I also see that when I am in 215% load and 3000 -4000 RPM I boost 27-28 PSI then from 4500 and beyond 22-23 PSI. What I hear from the video and haven't read on here is that I want to be at about 24 PSI. My question (as stated in the title) what does everyone else run on the stock turbo reliably?

[cobaltssoverbooster]

24psi is for drag racing and playing on the street. the turbo compression heat factor makes anything over 24psi a waste of time. also at 24 psi you are overclocking the turbo shaft speed a decent amount. the exhaust housing has a pretty tight ratio and chokes thus you only getting 23 psi after 5000 rpm.

22psi is the normal autocross and track level. compression heat factor is lower, and the shaft speed is stable. this setup usually nets a more stable boost curve and can allow for slightly longer boost after 5000 rpm.

i have seen factory turbochargers run 28psi but the intercooler was always sprayed using a c02 kit prior to and during the runs. drag strip setting only!

[lundy4137]

Ah I was just looking a reason to the rhyme. So what I hear is that the turbo is the limiting factor because of heat and shaft speed. That actually answers my next question about bigger turbo's(not the engine being the limiting factor). I will be using the DAL tables then to bring boost back down to stable levels. Its a shame too because the car really pulled hard the way it was. Who knew my first steps would be dialing things back a bit.

Thanks for the input

[Knightwolf]

23 psi is pretty smooth and quite powerful; 24psi pulls damn good.. if it hits 24.5, it'll spin the tires pretty much all the way through 2nd gear.. been working on my settings for quite some time.. My log today (1st new Maf cal log) had me between 23 and 24.5 from 3100-4900 and tapering off to about 20psi at 5800 or thereabouts.. had them pretty good up until I did new cam timing tables.. Now I gotta redo my Maf calibration and hope things continue as they were, only better. Crossing my fingers....

[T-Man]

My question (as stated in the title) what does everyone else run on the stock turbo reliably?

I have my cal setup for a progressive ramp to 21psi and carry 20-21psi till about 5500-5800 where it drops off to 19psi. I shift around 6300-6500 and still carry about 17.5-18psi.

[cobaltssoverbooster]

larger turbos that produce higher flow at lower shaft speeds have been used up to 50+ psi but at which point rods were discharged through the side of the lower block assembly.

safe full factory boost level with a larger turbo i would say 28-30 max depending on how long you want it to last and of course how much brass your balls are made of comes into play as well.

most people can land over 400whp on cobalt/hhr at only 24 psi boost. Most common turbos are as follows in order:
ZFR/EFR
S256et
pt6667 (im pretty sure thats the right number but not 100%)
GT3076r
GT2876r
and hahn s20g

[lundy4137]

Good info on the turbo's.

I was thinking earlier this morning about the different ways i can bring the boost down to normal levels and was wondering if using the WG duty cycle would be a better approach. So I added the Desired Boost and Boost desired DC PIDS and did one more last run. Sure enough the Boost Desired DC was reading 100% in those last cells so the trubo was giving everything I has. So I feel my time is better spent in the WG Duty Cycle table to get boost to where I want.

The interesting thing is that Desired Boost went to 37 psi. I am just wondering how this value is calculated. My thoughts are that this value comes from the Desired Air load table which would give me another way to adjust boost.

[cobaltssoverbooster]

i personally never looked at boost desired so i cant tell you. but on a factory turbo most cars get real snappy when dals go over 255. one min you will be making smooth power then all the sudden wham! high boost. try setting your wot dals to 255 and using the wgdc to correct actual boost level using boost sensor lo res - baro sensor. 3rd gear run corrections are the best as you will end up tuning out boost irregularities using trq management by gear later.


When i get officially released from duty sometime before the end of this year i will be driving back to california from florida. I will have plenty of road to play with im sure so as part of my trip i will be increasing boost levels above 24 psi and making power runs to record and map the effects of a factory turbo during "choke" conditions. I plan on bumping it to a boost line as flat as possible netting a 28-30psi level. I will be sure to show my results here on the hpt forum so anyone may review the effects of pushing a factory turbo past 24 psi.

[lundy4137]

Well I turned the DAL tables to 250 for WOT through out the RPM range. The Desired Boost all went to 37 psi or 254 kpa. So it seems the DAL table commands Desired boost. What I do not know is the relationship from Desired Boost to Actual Boost.

In other news I was making a 4th gear pull today and as my boost was climbing , it spiked to 29 psi and fell flat on its face. After that I could only boost to 8 psi. It looks like I might have blew open a coupling. Does anyone know where the most common place for this is so I can attempt to reduce my time troubleshooting?

[lundy4137]

ah on a 2nd review of the data the Boost Sensor LoRes went to 300 kPa. This is the pressure limit I have set in the torque management tab. Did I just go into Limp mode because I hit this value?

But that happened on my 3rd gear pull before i made my 4th gear pull where I was the issue. I will just add the data trace for anyone who wants to look at it. BTW I also set an underboost code

[cobaltssoverbooster]

dal is not responsible for boost control directly. as the name says it is desired air load. so by raising it the ecu thinks hey im supposed to have more air her and my throttle plate is open so the only option left is to raise boost. you need to raise it a point that gets in a general area then use wgdc to control the boost as intended. rpm by gear will get rid of boost creep