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JZA70 448 rwhp everyday
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Discussion Starter · #1 ·
hello eveyone, living in Ca sux, we can only get 91 out here, sometimes 92. Anyways, im curious whats the max psi i can run on pump gas. I have a good intercooler, and tune my wideband to 11.5:1, mostly stock timing. I want to know so i can calcualte my pressure ratio for my single.

~scott
 

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Different people will give you different answers as to what they consider "safe" I know here we have 93 and i wont run more than 1 bar. That may be too conservative for some tastes, but i am not melting pistons either :1poke:
 

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JZA70 448 rwhp everyday
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Discussion Starter · #3 ·
yea, thats insane...i mean it all depends on ur intercooling setup, and how much heat ur turbo makes, timing also plays a role. They sell stock cars that run more than 1 bar, STi and EVO being two of them. I was thinking 18 is a good conservative #

~scott
 

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STi runs 13.5 psi from the factory. EVO maybe 15.5. I would never run 18 on 91 octane, but hey, its your engine :) Of course with a good tune anything is possible :sadance:
 

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JZA70 448 rwhp everyday
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Discussion Starter · #6 ·
the tune is an important area, i dont have a standalone yet, and timing is gonna be left to stock. Ill have to keep an eye on my egt gauge.

~scott
 

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Espresso Connoisseur
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I keep it around 15-16psi on pump 91. On cold nights when I want to have fun, I know I'm going to overboost to 19psi anyway so I run the 100 octane.
 

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It is not how much boost you run, it is

A. How efficient is the turbo/intercooler at that boost
B. How efficient is the head/engine
C. How efficient are the cams
D. Do you want the car to make more power(torque) and feel better, or jsut run more boost?

There are far too many variables to answer your question.

Justin
 

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Former Moderator
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You have time to post on the forums but not calling me back!?!? Shame on you Justin!!!

:lol:

But honestly though, gimme a call back please early this week. :)

Sorry for highjack.

-Olivier
 

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Olivier Caza said:
You have time to post on the forums but not calling me back!?!? Shame on you Justin!!!

:lol:

But honestly though, gimme a call back please early this week. :)

Sorry for highjack.

-Olivier
hahha, sorry I missed your call today.

It looks like I have to go to Saudi Arabia after all on the 19th-3rd, so maybe we can plan for the 6th -8th or 9th?

Justin
 

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RoastBeefCurtain Commando
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LIke I said before Scotty, It depends on the turbo size and how much power, not the PSI.
18PSI on a CT26 is a hell of alot diff from 18PSI on a To4R
 

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justinn5 said:
hahha, sorry I missed your call today.

It looks like I have to go to Saudi Arabia after all on the 19th-3rd, so maybe we can plan for the 6th -8th or 9th?

Justin
It should work for us. Call me tomorrow early afternoon 819 575 6025. I will give you the final OK and start booking hotel and plane tickets.

You're gonna get roasted in Saudi Arabia!! :ugh2: :D

Sorry for the highjack again.

-Olivier
 

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PM-Performance said:
LIke I said before Scotty, It depends on the turbo size and how much power, not the PSI.
18PSI on a CT26 is a hell of alot diff from 18PSI on a To4R

Exactly! Backpressure plays a huge part in the equation. Basically you have to look at all of the factors that cause detonation, as that is what you are trying to avoid on pump gas.

Top ten things that determine detonation point:

1) timing
2) A:F ratio
3) spark plugs
4) compression/fuel
5) incoming air temp
6) hot spots or sharp edges
7) Combustion chamber shape
8) BackPressure
9) Piston Dwell time at TDC
10) Piston bore size vs flame travel
 

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MissSupra said:
STi runs 13.5 psi from the factory. EVO maybe 15.5. I would never run 18 on 91 octane, but hey, its your engine :) Of course with a good tune anything is possible :sadance:
evo actually runs 19 from the factory... my evo is running 22psi on pump gas with no fuel enrichment (like a bpu supra running 16 psi)

but an evo turbo will flow no where near the amount of air that a supra single will flow

bottom line becomes asking your tuner... when you get the car on the dyno, knock readings will tell you how much you can safely run

i personally run .9 bar on my single and it still blows the balls of stock twins
 

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RoastBeefCurtain Commando
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ive run 1.5bar on my 61mm with pump and it runs fine and not a single note of detonation.

Again it depends on many many many things. Dont generalize.
 

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PM-Performance said:
ive run 1.5bar on my 61mm with pump and it runs fine and not a single note of detonation.

Again it depends on many many many things. Dont generalize.
Agreed. Many factors.

Another, how fast do you plan on going when your doing pulls? If your going 150+ you may want some race gas at 19psi. If your staying at 130 or less you would probably be fine running 20psi. Alot of different factors, and alot of different opinions.

Evo owners run 22psi on the same compression motor we do. Compression and boost play a big role together. I think some supra owners worry to much about boost, while some worry to little.

-Corey
 

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I run 1.0 Bar (14.5psi) with pump 92 octane.

-sp74 .81 ar
-4 row intercooler
-272 cams
-aem 14-16 deg timing
-th400 unlocked

This car pulls harder from a roll or a stop than my old 6 speed bpu++ at 21psi with 104octane race fuel.
 

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justinn5 said:
It is not how much boost you run, it is

A. How efficient is the turbo/intercooler at that boost
B. How efficient is the head/engine
C. How efficient are the cams
D. Do you want the car to make more power(torque) and feel better, or jsut run more boost?

There are far too many variables to answer your question.

Justin
There's the intelligent post here :)

Don't listen to others quote numbers, get the car tuned right and safely for the street.

A T100 with huge cams, head work, dump pipe, etc. isn't going to make backpressure (and therefore "boost") that is at all comperable to a 60mm turbo. Listen to Justin and Larry here...
 

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I run 18psi on pump gas with no problems. On a 67 with a big wheel, it works fine. I normally drive it at 1 bar though, which is 440whp. I've ran it as high as 20 on pump gas. It's tuned for all these boost though on pump gas.
 
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