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 Post subject: low boost
PostPosted: Tue Aug 07, 2012 2:28 am 
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Location: burlington, mass
Year and Trim: 2001 Bonneville SSEi
1992 Bonneville SSEi (Sold)
Hi all
So I noticed recently that I'm not getting full boost anymore. The gauge use to be pinned at full throttle and now it will not go past 7 psi. What could cause this

Thanks, Keith

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2001 SSEi Bumbles
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1992 Bonneville SSEi (Sold)
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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 9:30 am 
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Location: Central Illinois
Year and Trim: 1992 SSE
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7 psi sounds like the normal level.

Have you made any changes recently?

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WHITE WHINE - IT'S INTOXICATING. 1992 SSE Supercharged 236.26 ci (.040 Over)
15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Easy Performance Gen 3 Air/Fuel Calibrator, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers and 10" Subs, 1300 watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, McCoy Motorsports Ceramic Coated Ported Exhaust Manifolds, Fan Override, PowerSlot Slotted Rotors.
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim Trailblazer mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 12:48 pm 
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Joined: Thu May 22, 2008 11:34 am
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Location: burlington, mass
Year and Trim: 2001 Bonneville SSEi
1992 Bonneville SSEi (Sold)
I did a new set of belts. But how come before it would be pegged at 10?

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2001 SSEi Bumbles
Angel Eyes ~ Cleared Corners ~ Tinted Tails ~ Intense FWI ~ 20% Tint ~ 180 Drilled T-Stat ~ GXP Brake & Suspension Upgrade ~ Alternator Rewire ~ Intense Shift Kit ~ Headers ~ Tr 6's

1992 Bonneville SSEi (Sold)
Fan over ride~NGK Tr 55's~180 Drilled t-stat~Clear Corners~Angel Eyes~Tinted Tails~Magnaflow Cat


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 1:08 pm 
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Yeah 7ish is stock. Mine never ever pegged.

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00Beast wrote:
Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 1:18 pm 
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Joined: Thu May 22, 2008 11:34 am
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Location: burlington, mass
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That's so strange. My was always up around 10. Now it's only at 7 with all my mods

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2001 SSEi Bumbles
Angel Eyes ~ Cleared Corners ~ Tinted Tails ~ Intense FWI ~ 20% Tint ~ 180 Drilled T-Stat ~ GXP Brake & Suspension Upgrade ~ Alternator Rewire ~ Intense Shift Kit ~ Headers ~ Tr 6's

1992 Bonneville SSEi (Sold)
Fan over ride~NGK Tr 55's~180 Drilled t-stat~Clear Corners~Angel Eyes~Tinted Tails~Magnaflow Cat


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 2:34 pm 
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Joined: Mon May 19, 2008 7:01 pm
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Location: Central Illinois
Year and Trim: 1992 SSE
2009 G8 GT
Higher-than-stock boost can be caused by exhaust restrictions, like a plugged cat or smushed pipe. A drop in indicated boost can be caused by mods that free up the airflow, like headers, higher ratio rockers, or hi-flow/no cat.

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WHITE WHINE - IT'S INTOXICATING. 1992 SSE Supercharged 236.26 ci (.040 Over)
15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Easy Performance Gen 3 Air/Fuel Calibrator, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers and 10" Subs, 1300 watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, McCoy Motorsports Ceramic Coated Ported Exhaust Manifolds, Fan Override, PowerSlot Slotted Rotors.
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim Trailblazer mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 3:04 pm 
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What John is describing is called boost stacking.

Here is a good description of it from http://www.gpona.com/forums/boost-stack ... t8975.html

Quote:
One way to look at it is, you motor is a big pump. It can only put out as much as it takes in. Therego, the more efficient that the air can get into the engine, the better. Only if you can have the same efficiency coming out of the engine. If you put a CAI, ported throttle body and blower on your car with a 3.5" pulley and you have little to no exhaust mods, that is bad. Sure, you let a whole bunch of air in, but it has no where to go. That's where headers come in. They are much less restrictive than stock exhaust manifolds. Ultimately your goal is to match the output to the input.

Boost stacking is when you have too much air trying to get into the engine and it has no where go. This actually causes the blower to heat up which also heats up the air coming in. This is bad. You want the coldest air possible coming in, this makes for better combustion. Now the Gen V blowers are a little bit more free flowing than the Gen 3's, I believe that is why you guys don't have to drop pulley sizes as low as the Gen 3 guys to get the same results. Also, the 97-03 guys have to worry about the bend in the stock DP which causes a lot of exhaust restriction. The 04+ guys don't have to worry about that fortunately.

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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 3:10 pm 
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Joined: Thu May 22, 2008 11:34 am
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So pretty much I'm gonna need to do rockers? Cause I already have fwi and headers with cat.delete.

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2001 SSEi Bumbles
Angel Eyes ~ Cleared Corners ~ Tinted Tails ~ Intense FWI ~ 20% Tint ~ 180 Drilled T-Stat ~ GXP Brake & Suspension Upgrade ~ Alternator Rewire ~ Intense Shift Kit ~ Headers ~ Tr 6's

1992 Bonneville SSEi (Sold)
Fan over ride~NGK Tr 55's~180 Drilled t-stat~Clear Corners~Angel Eyes~Tinted Tails~Magnaflow Cat


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 3:19 pm 
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Not necessarily. The 7 psi you see is actually better than the 10 you previously saw if boost stacking is the issue. It means that your engine is moving more air, and not stacking excess pressure, and heat.

I don't understand why the belt change brought it down though. I would think that if you had a belt that was slipping, and you replaced it with a new one, your pressure readings would be reversed from what you stated.

And 7 psi is what a stock m90 is supposed to output. If your sig has all of your current mods, then 7 psi is where you should be if everything is working as it should.

Do the 01s still use a map sensor for the boost gauge reading? Is that maybe gunked up, or on its way out?

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92 Olds 98. L67, Gen 3 M62, 2.55 pulley, FWI, PLIM, 1.8 YTs.

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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 3:22 pm 
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So all you did was change the belt and now it only shows 7psi?

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Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.


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 Post subject: Re: low boost
PostPosted: Tue Aug 07, 2012 9:26 pm 
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Temperature has a real effect on boost levels as well. I've seen as high as 21psi on a 3.4" pulley on a -35*F day. If its warmer now than last time you noticed, that could be the explanation.

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 Post subject: Re: low boost
PostPosted: Wed Aug 08, 2012 11:18 am 
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It has been very hot and humid as hell here. I'm not sure when it actually started to read the 7 psi but I didn't notice it until week or 2 after my new belts. It could have been doing it for a while I don't really watch the boost gauge all the time.

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2001 SSEi Bumbles
Angel Eyes ~ Cleared Corners ~ Tinted Tails ~ Intense FWI ~ 20% Tint ~ 180 Drilled T-Stat ~ GXP Brake & Suspension Upgrade ~ Alternator Rewire ~ Intense Shift Kit ~ Headers ~ Tr 6's

1992 Bonneville SSEi (Sold)
Fan over ride~NGK Tr 55's~180 Drilled t-stat~Clear Corners~Angel Eyes~Tinted Tails~Magnaflow Cat


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 Post subject: Re: low boost
PostPosted: Wed Aug 08, 2012 1:33 pm 
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irish91983 wrote:
It has been very hot and humid as hell here. I'm not sure when it actually started to read the 7 psi but I didn't notice it until week or 2 after my new belts. It could have been doing it for a while I don't really watch the boost gauge all the time.



Ok. I wouldnt really worry about it then. Does it seem any slower?

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Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.


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