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'05 CTS-V (sold)
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Discussion Starter #1
Is it possible that I lost boost from the S/C from the addition of headers? Maybe a loss of backpressure? If so, I'd think it would be pretty safe to go to a 2.6" pulley on ol' Maggie.
 

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04 Cadillac CTS-V
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Boost and backpressure have nothing to do with each other. Something else is going on, like a hose isn't plugged in to the right place.
 

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04 CTS-V, 05 STS, 07 SRX- All sold :(
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Actually, most people report boost loss with the addition of headers. I think you're fine.

I know it's been discussed here- try doing a search for "boost + headers".
 

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Discussion Starter #4
The only reason I ask is b/c of the [email protected] time I ran last Wednesday. Last spring I ran [email protected] and the only difference in mods was the addition of the headers and a stiffer suspension setup. I've been itching for a 2.6" pulley anyways and I guess I'm just looking for an excuse to get one.
 

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09 White Diamond Slade, 05 Black CTS-V, 94 White Diamond STS
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Actually, less backpressure will lower boost levels with a supercharged engine, however even with the lower manifold pressure you should still produce more power than previously. That's exactly the scenario I experienced a few years back on my Grand Prix GTP, and yes, I was able to safely run a smaller pulley at that point to get the boost back up.
 

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See you in the funny papers
04 CTS-V, 05 STS, 07 SRX- All sold :(
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Long tubes change the flow characteristics of the engine dramatically. Your AFRs are probably really rich if you haven't been tuned since the headers.

Rick at StealthV supposedly has an awesome tune for Maggied cars with headers. I'm not maggied, but his NA tune I'm running is fantastic. If you haven't been dyno tuned since the LTs, I'd recommend sending him an email.
 

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05 maggied CTS-V, 2017 NSX Whoo Hoo!
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I have never read anything that equates an increase of backpressure to an increase in HP.

Hogwash.

The better it breathes, the more power you can make. :thumbsup:

I lost power when I put the cats and the resonator back on.

The only thing I gained was confidence that I wasn't getting stopped or ticketed for the noise (it was loud and BITCHIN and stunk!).

Show me any go fast car that crams stuff in the tailpipe or restricts the headers to increase backpressure to get more power.

Doesn't do you any good to have high boost pressure and lousy flow.
 

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05 Redline CTS-V
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common misnomer.... boost is best when numbers are high...

boost is a measure of how much air is backed up in the intake manifold before the cylinders, if you let the cylinders breath better you'll have less backed up air, hence less boost

so yes, headers will result in a drop in boost, as they free up the "exhale" process.
 

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common misnomer.... boost is best when numbers are high...

boost is a measure of how much air is backed up in the intake manifold before the cylinders, if you let the cylinders breath better you'll have less backed up air, hence less boost

so yes, headers will result in a drop in boost, as they free up the "exhale" process.
Exactly. This is well documented in the Scooby world.(Subaru)
 

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Discussion Starter #10
Long tubes change the flow characteristics of the engine dramatically. Your AFRs are probably really rich if you haven't been tuned since the headers.

Rick at StealthV supposedly has an awesome tune for Maggied cars with headers. I'm not maggied, but his NA tune I'm running is fantastic. If you haven't been dyno tuned since the LTs, I'd recommend sending him an email.

I'm running Rick's tune :bouncy: . The man knows his stuff!
 

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common misnomer.... boost is best when numbers are high...

boost is a measure of how much air is backed up in the intake manifold before the cylinders, if you let the cylinders breath better you'll have less backed up air, hence less boost

so yes, headers will result in a drop in boost, as they free up the "exhale" process.
Actually, let me rethink this. Would this apply to superchargers? Exhaust would be dependent on engine THROUGHPUT(capitalized because I like the word). So would boost drop happen? On a turbo, it depends on exhaust gases to run so it's all intertwined. Increased efficiency anywhere in the system would cause a drop in pressure to create the same power.

Guess I should've taken automotive instead of electronics in Vocational School...:bighead:
 

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If the scavenging effect of the header is good, then boost should drop.

At valve overlap this will cause a bigger drop in pressure so more charge (better flow) happens, and boost pressure drops.IMHO

If these were two strokes everyone would be looking for a "tuned pipe". :rolleyes:
 

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OK - I'm going to ignore the responses and report only cold, hard, personal experience.

Maggie with 3" pulley = 4.5# boost
Maggie with 2.8" pulley = ~7 psi boost
Maggie with 2.6" pulley = 9.5 psi boost (consistent 9's with data logged 9.5's, even a 10 psi once...whoops)

Reference above is stock exhaust with RT cats and gutted mufflers.


Change that to BB 3" exhaust (cat back) and BB original headers (cats blown out)..

Maggie 3" = :wtf: why would I try that again?
Maggie 2.8" = 6.1 psi (highest peak ever)
Maggie 2.6" = 8 psi



So, in reality, measured boost, as with a gauge or data logging device, will be lower.






However - the question you meant to ask is whether CYLINDER PRESSURE remains constant :thepan:

WW
 

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OK - I'm going to ignore the responses and report only cold, hard, personal experience.

Maggie with 3" pulley = 4.5# boost
Maggie with 2.8" pulley = ~7 psi boost
Maggie with 2.6" pulley = 9.5 psi boost (consistent 9's with data logged 9.5's, even a 10 psi once...whoops)

Reference above is stock exhaust with RT cats and gutted mufflers.


Change that to BB 3" exhaust (cat back) and BB original headers (cats blown out)..

Maggie 3" = :wtf: why would I try that again?
Maggie 2.8" = 6.1 psi (highest peak ever)
Maggie 2.6" = 8 psi



So, in reality, measured boost, as with a gauge or data logging device, will be lower.






However - the question you meant to ask is whether CYLINDER PRESSURE remains constant :thepan:

WW
You are so frickin' brilliant!:highfive:
 

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However - the question you meant to ask is whether CYLINDER PRESSURE remains constant :thepan:

WW
Once again, WW rules... :worship:

Boost isn't nearly as important as cylinder pressure. Cylinder pressure is what generates power, as well as corresponding risk. :)

My guess is that it goes up a little, even though boost is down.
 
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