i have a 2.8 and have zzp midlength header downpipe and magnaflow exhaust all 2.5in the max boost i hit is 16.2 what is most people boosting with the same set up and i think i might have slight belt slip

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I've got GMS2 w/ a 2.9", cai, and full exhaust and on some of the colder nights here I've seen about 16psi. When it's warmer/more humid out it's closer to 14-15psi.

 

Remember guys, boost is not power. Boost is just a restriction of air flow. Essentially the less boost you have the better. I am on a 2.8 pulley and full 3 inch exhaust. I only see 15, TOPS 16 psi. I used to see 18psi before I upgraded my exhaust again. If you plan on pushing serious boost, I really recommend getting a full 3 inch exhaust.

 

i know boost is only a measure of restriction but vince told me that he thinks he saw some belt slip at the top of second and i am only boost 16.2 and i thought it should be more like 17 with a 2.5 exhaust and a 2.8

and can i use an oversized tensioner pulley and still use the stage 2 belt

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if your going off the stock gauge it completely inaccurate, log it with hpt otherwise all these numbers everyone is saying they hit are completely irrelevant.

in hpt you should be seeing 15ish the stock boost gauge lies in your favor. i have noticed its anywhere from 1 to 1.5 psi above the actual boost psi.

 

Honestly so much plays a roll in boost. Weather, mods, tune, etc.

I have 42's, 2.9, full 3" exhaust, hpt by vince, and a few other mods. I saw 17psi with my 2.85 then tuned it and my boost went to 14psi. Well found out the desired map in the tune got changed from 256kpa to 200kpa, so im maxxing out and bleeding boost cuz i cant make anymore cuz the tune.

Realistcly a 3.0 should see 14psi, 2.9/2.8 should see 16-17psi then factor in the mods and tune and weather.

 

im at 15 psi on a 2.79. the stock boost gauge is more like an idea.

 

Yah i watch my boost gauge and inteceptor see if they match on WOT. Colder nights u boost quicker and higher, but in my case i cant since my tune is maxxed out at 14psi in the desired map.

My 2.85 hit 16.67psi on the dyno when it was 87* out and bad ic pump.

 

15 at first then 17.5 at high rpms on a 2.8

 

this is with logging with trifecta software so i know the numbers are right

 

Dude 16.2psi on a 2.8 isnt bad. Vince tuned my car and we maxxed 16.7psi with my 2.8 and i have 2.5" axle bend at the time.

Do u have stage 2 belt? IIRC u can run stage 2 belt on oversized tensioner but not saying itll fix the boost level.

 

i have a stage 2 belt but he said he thinks his saw some belt slip

 

yah it looks like ur not slipping that bad tho. Have u replaced the belt yet?

 

no i haven't but it has only been on for like 6k miles i dont think it is stretch or anything

 

Hmm yah i had my first stage 2 belt on for like 20k then my new one for like 5-10k now.

Do u have access to hpt or anthing to check on ur map?

 

You're boost is low because of your exhaust. Remember boost is a measure of restriction. When you got the midlength header and downpipe combination it freed up airflow. Thus resulting in less boost. Don't get all bent out of shape because one car is boosting 18 psi and you're boosting less with a smaller pulley.

I was only at 15 on the 2.9 pulley.

Now with the TVS and 3.1 I see ~20psi.

 

i dont care a about how much i am boost it is that i think my belt is slipping because that is what vince said when he look at my logs if anyone can read hes logs i can send them to you

 

I have HPT. Send the log to me...I'm not at home right now but when I get home I can check them out.

I don't think you have a boost leak. What is the car doing up top? Does the car feel like it hits a wall or something after a certain rpm?

A friend of mine had his boost tables messed up from a tune and the car would drop boost to 5psi after 6k rpm. Could be a similar issue just not as extreme as his.

 

Yah it could be ur tune just like mine. The map can be set to low so u wont see the boost ur pulley should putting out

 

If Vince from Trifecta touched his tune that is the problem. I've seen more issues from Trifecta than I can shake a stick at.

 

Yah vince lives by me and only HPT close thats why i use him. First tune couldnt do much since my IC pump went dead and IATS were to high, 2nd time we road tuned it was alright, then 3rd time we checked tune adjusted then he somehow changed my desired map to 200 not 256 so thats why my boost stops at 14psi.

So im deciding where to get tuned again here.

 

Don't forget to add 14.696 psi to any reading , atmospheric pressure @ sea level

 

i have a 2.7, my digital gauge reads 19.7

you know i have an oversized idle pulley that would eliminate that slip... its in my f/s thread

 

Depends on what bar MAF u have. I think stock redline is 2 bar cuz at 100kpa my boost is 0, so 200 should be 14.2 or something. Cuz driving the MAF is around 1 and WOT is goes to around 2.

So depending on the MAF and elevation, etc. Cobalts might have 1 bar then i dunno what yall MAFs are.

 

g85 ss how can i send you my logs what is your email