Alrighty i got the 2.8 Pulley a couple weeks ago and for the first day or so i was runnin about 18.5Lbs of boost, Then i found out the belt was messed up so i put it on the right way and was only hitting 15 pounds of boost because the belt now slipped because it became loose, I ordered the oversized Tensioner pulley put that on the belt is tight as hell and im still only running 15lbs of boost, My buddy with a black cobalt has the same mods and hes runnin 18.5 too, Any Ideas

I also have the high flow injectors

Thanks

 

that's right where mine is, 15#. I have Stage II, ex honed/ceramic coated exhaust manifold, Borla 2 1/4" cat-back, K&N factory filter with opened up factory airbox for more flow and cold air, 2.8" pulley. My boost gauge with key on eng off is dead on 0. Read my comments on the boost numbers thread. I have not done the boost bypass mod. Without knowing if/and if, how much detonation is happening, or if a lean condition exists, I don't want to put too much excessive boost into my engine. I do not have access to unleaded race fuel, but I do use octane boost. Even with a brand new knock sensor, and only at about 17/18# (factory calibrated boost for the Typhoon I believe was 14#) , I over boosted my Typhoon enough once to literally melt the brand new spark plugs. That was in a cast iron head. That much potential heat would not be good in an aluminum head. A person should really have a high quality knock sensor gauge, and a good boost gauge to be safe when raising the boost to 17/18# IMHO.

Doc

 

did you reset the pcm...gotta unplug the negative battery....

 

it's normal for the 2.8 to boost to 15 only. 2.7 will put you at 18. All I'm running is a 2.8, 60lb injecotrs, HP Tuners and NGK plugs...the rest of the car is all factory and I'm hitting 15 dead on, no codes. Everyone else I've seen with 2.8's are hitting 15psi.

 

i'm getting 18psi with my 2.8 and gm stg 2... Idk what some of you are saying..i was hitting 15psi with the 3" that came with gm stg 2. check all your lines make sure you dont have a boost leak.

 

15 psi dosnt sound normal for me, im hitting close to 18 with my 2.85 zzp.

 

Hmmm, interesting....Maybe it could be I'm running the factory belt thus far. I got a stage 2 belt now, so perhaps I'll be jumping up to 18 as well? Any thoughts? I know I get belt slip, so I think that may be the reason.

 

well i have stage 2, and when i had the pulley stage 2 came with i was hitting 15 psi, maybe you are slipping, id check everything to make sure cuz soemthign aint right ill tell u that much.

 

yeah, I checked, no leaks...I'm thinking the belt slip is what's holding me back...My buddy has a 2.7 and he's on the factory belt to, hittin only 18, so we're switching them out this week, so I'll definately keep things posted for this.

 

It might be A BOOST leak thats the only thing i can think of because that belts the gm stage 2 belt and shes tighter than hell, Ill have to check all the lines for the boost leak.

 

this is interesting now...Definately looking into this

 

I was seeing 16 with just stage 2 and I have seen 17 with the 2.8, but that wasn't at redline so i am sure there is a little more there.

The slipping belt may be part of the only seeing 15 lbs problem, but remember if you are still on the stock tube you have 500-750 less rpm to build boost than those of us with HPtuners (assuming they upped the limiter) or stage 2, so i wouldn't be overly worried. I don't remember seeing much over 15 till at least 5500-6000 rpm any way with the 2.8.

 

ya if you ahve ths stage 2 belt on as we speak there should not be any slipping issues.

 

Everything I've read says that. Ordered my 2.8 tonight.

 

Also, What elevation you at? Up here at 6800 ft I only got 10 stock and 12.5 with stage 2 (those numbers on stock gauge that was a little off. Now I get only 11 with stage 2 pulley on my interceptor gauge, Is something wrong or is that just the damn elevation?)

Also, were are common places to have a boost leak? Were should I check and how?

Thanx, and sorry for the thread stealing, good luck on finding the problem.

 

I have stage 2 and K&N drop in and I see around 14.5 - 15 boost. Your elevation does have alot to do with it though. I am at around 500ft elevation. I saw a calculation that said that you lose 3% per 1000' of elevation. With that in mind, at 6500' you will boost 18% less then I do which would be around 11.5 - 12 lbs boost.

Most boost leak would probably come from between the SC and the intake manifold. If you want to check for leaks feel around that area for air.

 

but I think it was a mistake to reset it.

I am under the impression that the Stage II PCM flash limits boost to 15#. I am also at 4100' altitude.

My boost gauge does not drop after 6000 RPM either-it stays right at 15# all the way to 7000 RPM or the rev limiter which ever I hit first, with the 2.8".

One other aside, I have seeen many folks reference 12.5 # boost with the stock 85 MM 3.346" pulley. This is incorrect. According to the Cobalt SS S/C factory shop manual, under engine controls, 2.0L, 6-1395, "Max engine boost is 83 kpa/12 psi."

But then the 2006 Cobalt owners manual, page 5-108 recommends gapping the spark plugs at .042. The shop manual recommends .045 spark plug gap in one section and .040 in another. Multiple choice, I guess. For anyone interested, I spoke with an NGK tech, today about the best plugs for my application, given my mods, and he strongly recommended Iridium BKR7EIX, on step colder than the NGK Iridium recommended for stock LSJ, BKR6EIX. He strongly did not recommend the plug I see many using, BKR7E(S)-11, the next step colder than the NGK standard recommended BKR6ES for stock LSJ, saying that they would not hold up anywhere near as well as the BKR7EIX Iridium plug, and that it took a lot more energy to spark the BKR7E(S)-11. He said the BKR7E(S)-11 had a soft nickle alloy tip and it had a lazy growth kernel. The BKR7EIX fires easier, lasts longer, and has a much higher/faster/larger flame/growth kernel under high boost. So be your own judge. Sorry to hijack the thread, but thought this information was worth sharing, and relative to the boost issues. He also recommended gapping the BKR7EIX at .040/.042, no need to close the gap further. Should come gapped about right from the factory, but check anyway. I checked the gap on a set of NGK factory plugs I got from the dealer, like the ones that come in the LSJ, PFR6T-10G. they were supposed to be gapped at .040 and they were all .036.

Doc

 

I only ever saw 15 with a 2.8. I see about 19 with a 2.5. As stated before, a great deal of it has to do with your elevation and the accuracy of the stock gauge.

 

Um, something wrong here. Running lower levels of boost could be of advantage for you. But everyone is reading differently, dosent make sense.

For the record im running 15.5

BLAME AUTOMETER!!

 

I also talked to an NGK tech named Chris when I purchased my NGK Iridium BKR7EIX plugs. He recommended that I gap my plugs at .035 with my mods. The car is running good at this gap and at this time I see no reason to change it. I have not taken it out to the track but what I have seen it do on the street is 102 MPH at 17.5 PSI of boost at the top of 3rd gear.

 

if your NGK Iridium BKR7EIX plugs are working ok w/.035 gap, no need to change. Might want to pull a couple of plugs after some miles on them and check their color etc. just to see how they are burning.

I drive my car on the street as a daily driver, so I am concerned with detonation issues.
However, I have never felt my 2006 SS S/C pull the timing back like I could with my 1987 Grand National, 1993 Typhoon or 1991 Syclone, so hopefully the octane boost I am using is doing it's job.

Doc

 

Let's not forget temperature will have A LOT to do with it. You can see as much as 3psi difference between a hot, humid 95 degree day and a cool, dry 45 degree night. Altitude is huge too.

I have my BKR7EIX gapped at .040 with my 2.8".

 

I think it has alot to do with Temperature because when i left for Car Craft at 6:30 Yesterday mornin it was cold out (I also just got my stage 2 belt no reflash but just the belt) and i was hittin around 17lbs with the 2.8 so i just coulda been a really cold day and i was hitting 18

 

I`v been having the same problem with my 2.8 inch from intense. I put it on expecting to have 17-18 psi but my gauge doesnt read past 15. but when i was at the track the first time i got it i was hitting at least 16 as i can recall. but not today in my 110 degree hometown. but it was hitting good at the track the other night ? maybe temp is are the problem???

 

is running a 2.8" pulley on the stock tune really safe? Dosen't seem like it would be.