12psi with 2.77 and o/r pipe?

[Corner-Carver]

Just wondering how much boost you guys are getting now? I'm running a 2.77 with an idler, CAI, MAC o/r h and MAC catback. Bypass unplugged.

On a cool night (low 70's), I saw the guage blink 13psi in 3rd. I'm running the Nordskog digital guages btw. Just wondering what you guys are seeing boost wise. I know the o/r will lower boost versus a catted system albeit very slightly.

 

[Shanezam203]

i havent installed my pulley yet or boost gauge, so I cant comment. I just wanted to ask if I could see a pic of your digital boost gauge. Thanks, Shane

 

[Miamifan1354]

No really all that slightly.. i got almost two full ounds of boost back when I put my cats on. i got the 2.76 and I'm seeing right around 13 to 14 lbs on hot days, and more on them cool 70 nights that you're talking about.

 

[MTI LS1]

I have a 2.75 and usually hit close to 15, with a catted X.

 

[Miamifan1354]

Yeah, the diff in 2.77, 2.76 and 2.75 are so slight, that all three of us should see the same amount of boost. I think you need to add cats. LIke i said I'm getting 14 on hot days and def 15 on cooler nights, this guy says 15. You need cats..

 

[Corner-Carver]

Originally posted by Shanezam203
i havent installed my pulley yet or boost gauge, so I cant comment. I just wanted to ask if I could see a pic of your digital boost gauge. Thanks, Shane

http://community.webshots.com/user/cornercarver99

It's in the '03 folder. Not really a good picture since you can't read BOOST PSI, OIL PSI, and WATER TEMP that's under the numbers on each guage.

 

[03cobra76]

I have the 2.75 and bassani o/r x-pipe. On the street I see 13-14 psi but on the dyno I saw 15 psi all the way up to about 6000 rpms.

 

[Tranzlucent]

You don't need the cats. Get to a dyno and see what kind of #'s you are putting down. I'll bet you make more power with less boost than the guys with cats. It's just like adding headers. You loose boost but gain more power. Efficiency is the key.

 

[CobraBob]

Originally posted by Tranzlucent
You don't need the cats. Get to a dyno and see what kind of #'s you are putting down. I'll bet you make more power with less boost than the guys with cats. It's just like adding headers. You loose boost but gain more power. Efficiency is the key.

You are so correct! More power with less boost is always a good thing. Some get hung up on higher boost numbers when in reality it is the relationship of power to boost that is more important. Some mods, like porting the blower or adding headers, will slightly lower the boost while increasing power like you stated. And that's a good thing! It is better to make 475rwhp on 14 lbs. of boost than 477rwhp on 16 lbs.

 

[paluka21]

Originally posted by Miamifan1354
No really all that slightly.. i got almost two full ounds of boost back when I put my cats on. i got the 2.76 and I'm seeing right around 13 to 14 lbs on hot days, and more on them cool 70 nights that you're talking about.

exactly as the others have said, boost is just a measure of backpressure. If you lost 2psi when going with a more free flowing exhaust, chances are you gained power/tq by doing this. By going back to a more restricive exhaust system and "gaining" those 2psi back, you are really gaining nothing but backpressure, and maybe losing power. ( more than likely )
only way to show you is on a dyno.

IE: You have a stock motored car that is pusing 13psi through a stock intake manifold and unported heads. The car made 500rwhp in this state.
You remove the heads and intake, match port their runners to whatever size gasket you are using, and open up the exhaust runners in the heads.
In this state the same car makes a total of 10psi but makes 525rwhp since the airflow is more free flowing. To the best of my knowledge this also lowers static compression by having the forced air flowing less strictively throughout the motor, and lowering the boost pressure inside the cylinders. Add the non ported parts back, and there is more pressure..or more static compression in the cylinders....I think I'm right on this one

Dan

 

[Spanishfly]

Originally posted by paluka21
IE: You have a stock motored car that is pusing 13psi through a stock intake manifold and unported heads. The car made 500rwhp in this state.
You remove the heads and intake, match port their runners to whatever size gasket you are using, and open up the exhaust runners in the heads.
In this state the same car makes a total of 10psi but makes 525rwhp since the airflow is more free flowing. To the best of my knowledge this also lowers static compression by having the forced air flowing less strictively throughout the motor, and lowering the boost pressure inside the cylinders. Add the non ported parts back, and there is more pressure..or more static compression in the cylinders....I think I'm right on this one

Dan

:idea: good example.