Boost Psi & Compression

Grabbin' Asphalt

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#1

• Dec 30, 2013

• #1

If i were to consider adding some psi boost in a SC form down the road, what is my psi limitation with my "P" heads milled .030, is my compression in the range of 9.7:1 - 10:1?? ...would that work with only 5-6 psi or could i do 8psi with a intercooler and still be safe with a good tune?

 

Last edited: Dec 30, 2013

KamiKaziDK

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#2

• Dec 30, 2013

• #2

You should be able to do 8psi with an intercooler, but it also depends on the blower you're using.

 

Grabbin' Asphalt

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#3

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• #3

I'm eyeballing the Vortech V3 Si trim.

 

93TRANSAM

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#4

• Dec 30, 2013

• #4

The V3 Si is the perfect blower, the compression isnt that much of a problem with 8-10lbs of pressure aka stock pulleys if the tune is good intercooled or not. If it is something you are concerned about you can just use a thicker head gasket but I wouldnt sweat it. I would just use the factory Vortech upper and lower pulley combo and have the tuner creep up on timing especially under peak rpms since most guys tune for WOT and dont play with 1/2-3/4 throttle bursts or acceleration areas and thats usually were a street guy will run into issues unless they ride the rev limiter too much first. If you decide to go Vortech let me know I get pretty good hookup with them either way good luck and have fun!

 

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Grabbin' Asphalt

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#5

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• #5

93TRANSAM said:

The V3 Si is the perfect blower, the compression isnt that much of a problem with 8-10lbs of pressure aka stock pulleys if the tune is good intercooled or not. If it me a is something you are concerned about you can just use a thicker head gasket but I wouldnt sweat it. I would just use the factory Vortech upper and lower pulley combo and have the tuner creep up on timing especially under peak rpms since most guys tune for WOT and dont play with 1/2-3/4 throttle bursts or acceleration areas and thats usually were a street guy will run into issues unless they ride the rev limiter too much first. If you decide to go Vortech let me know I get pretty good hookup with them either way good luck and have fun!

Click to expand...

I've heard a few youtube vids on the Sci and Si and the Si with 8psi sounds way quieter and I like that one a lot. I really don't like the look of the I/C though, would like something other than that set up.

 

Grabbin' Asphalt

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#6

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• #6

I also feel like even though my static compression may seem on the higher side for boost, would not my Ecam help my dynamic compression and bring me into the safe zone with it's 110 LSA and 220/220 duration??

 

madspeed

Colonel Mustard

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#7

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• #7

my 333 is at 9.6:1 and runs 10psi on an e cam

 

Grabbin' Asphalt

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#8

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madspeed said:

my 333 is at 9.6:1 and runs 10psi on an e cam

Click to expand...

Don't you have a thread with a blown headgasket at around 1500-ish miles after install?

 

madspeed

Colonel Mustard

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#9

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yes, but i chalk it up to a fauly gasket or install. There is a piece of the gasket blown out at a stud location but not at any cooling passage, so different issue

 

Grabbin' Asphalt

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#10

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All this makes me nervous

 

TOOLOW91

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#11

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If it makes you feel better I am throwing head gaskets , arp head bolts and an s trim on a stock motor with 10/12 lbs going through it in a few mos will be all together

 

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Grabbin' Asphalt

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#12

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I do have arp head bolts installed.

 

TOOLOW91

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#13

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Grabbin' Asphalt said:

I do have arp head bolts installed.

Click to expand...

well as far as that goes that would just help with the head lifting

 

RangerJoe

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#14

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His heads are iron too. I still think you will be okay with mild boost, but the aluminum heads will tolerate a little more compression and boost than irons.

Joe

 

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Grabbin' Asphalt

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#15

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RangerJoe said:

His heads are iron too. I still think you will be okay with mild boost, but the aluminum heads will tolerate a little more compression and boost than irons.

Joe

Click to expand...

5-6 Psi or 8ish?? ....an intercooler will drop it some too right??

 

mikestang63

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#16

• Jan 1, 2014

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The V3 is an entry level kit, that is installed properly on a well maintained and functioning engine will provide you with a safe, reliable increase in HP. The problem I see guys run into is the "it's never enough" syndrome. They start swapping out pulleys for more boost and then at 12lbs wonder why their head gasket lifted. At 10:1 you are a little high on the compression, as stock is more like 9:1. You can get around that with either a tune and/or a meth system.

 

Grabbin' Asphalt

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#17

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So i've been looking at CR and Psi air ratios and it seems like 12.5:1 is tops before Non-pump gas.

 

84Ttop

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#18

• Jan 2, 2014

• #18

I would say tops of 11.8 for your a/f ratio's

(for the record 9.5:1 compression and 35 psi of boost, we broke the cylinder head before we had a gasket failure.... just saying) It's all in the tune up my friend.

 

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