on 9.1:1, what is safe boost?

Shane818 · 03-23-2004, 05:08 PM

I am getting wiseco 9.1:1 compression and am wondering what i can run to be safe. I want to run 13 lbs all day. should that be ok? Its gonna be a daily driver and i am going to try to tune it right with the s-afc.

ITSME4G63 · 03-23-2004, 05:17 PM

I'm no expert , but I've heard that anythin over 8:5 is suicide.

Groomz · 03-23-2004, 05:50 PM

Quote:

Originally posted by ITSME4G63
I'm no expert , but I've heard that anythin over 8:5 is suicide.

Suicide, eh?

Maybe not that extreme. 9:1 is fine. A little high for me, but its not dangerous at all. Many people I know run that compression. Happy tuning,

-Groomz

Stanford · 03-23-2004, 06:33 PM

The stock Evolution 8 has 8.8:1 compression, 9.1:1 is not that high. You will be fine, and could run well over 13lbs. You will even have better spool times.

talon1979 · 03-23-2004, 07:20 PM

The only problem you may encounter w/ 9 to 1 is that it will want to run leaner which you can just tune out.

dsmturboawd · 03-23-2004, 07:23 PM

set boost acording to knock.

"what psi" is the worst question ever.

crankbender · 03-23-2004, 07:48 PM

Seriously this will be dependent on the individual engine, gas, timing, etc.

For the short answer: assuming everything is in good shape you can run over 13psi on a 9:1 engine.

SOURCE1064 · 03-23-2004, 07:49 PM

It has alot to do with your turbo too. I have 9:0.1 and will be able to run a max of 22psi on my FP Red(60-1) on pump gas.

kpt4321 · 03-23-2004, 07:50 PM

Quote:

Originally posted by talon1979
The only problem you may encounter w/ 9 to 1 is that it will want to run leaner which you can just tune out.

Ummm... the motor does not "want" to run leaner with a different compression ratio.

talon1979 · 03-23-2004, 08:25 PM

Ok, so then does the car just want a higher octane fuel since it doesn't "want" more fuel? Please explain what you mean.

How else would you compensate for higher compression pistons? I suppose you could retard the timing a little.

jmc94gsx · 03-24-2004, 08:33 AM

there are 3 ways of reducing knock, retard the ignition timing, air intake temperature and the use higher octane fuel.

Higher octane fuel offers the benefit of a more controllable burn and is not likely to burn prematurely. Lower octane fuels and the combination of a higher comprssion ratio motor may result in detonation due to an early combustion of the fuel before the flame front, ugly.

Higher octane fuel is more controllable and predicatable, allowing for more aggressive ignition timing tuning to be entered back into the game.

The way higher octane fuel burns is the benefit, not more fuel.

IPT · 03-24-2004, 08:41 AM

Quote:

Originally posted by ITSME4G63
I'm no expert , but I've heard that anythin over 8:5 is suicide.

Damn then my 9.5:1 must be a mass murder...

Ran 20 lbs on pump gas on a 60trim.

Enigma_Man · 03-24-2004, 09:14 AM

Quote:

Originally posted by talon1979
The only problem you may encounter w/ 9 to 1 is that it will want to run leaner which you can just tune out.

Umm... incorrect. Why would you think that?

The engine will run hotter, more pressurized, and therefore with more propensity to knock, but it won't run leaner... Lean means you're getting too much air or not enough fuel... Changing CR affects neither (directly). You need higher octane, or more fuel to compensate for the higher pressures and temperatures the combustion chamber will see, yes, but that's not "lean".

Also... run whatever pressure you can without knocking, that's how to do it.

-Jesse <- 8.5:1 16g, I have trouble running 14 psi without knocking off the chart.

talon1979 · 03-24-2004, 11:57 AM

Quote:

Originally posted by Enigma_Man
Umm... incorrect. Why would you think that?

Because I figured the easiest way to cool things down would be w/ fuel. After hearing it doesn't make a difference I did a bunch of research to understand all of it better. I quickly learned I was dead wrong.

boosten gs-t · 03-24-2004, 12:06 PM

To break it down, if you have low compression (gs-t/x) you have alot of room for boost. If you have high compression (gsr/type-r) you have little room left for boost. Which ever way you go, remember TUNING is the key!

myblack98gst · 03-24-2004, 01:26 PM

hondas are 11:1 or more stock and can see 14-16 psi with very good tuning.

pro drag imports are running around 13-15:1 compression with sometimes 40+ psi of boost.. all about the tuning

Enigma_Man · 03-24-2004, 01:44 PM

Quote:

Originally posted by talon1979
Because I figured the easiest way to cool things down would be w/ fuel. After hearing it doesn't make a difference I did a bunch of research to understand all of it better. I quickly learned I was dead wrong.

Well, that is true, more fuel = cooler, but that doesn't mean more compression = lean. But if you know now, awesome

-Jesse

98talonAWD · 03-24-2004, 05:00 PM

Tune the engine according to knock, timing, and EGT temps or get something even better... WIDEBAND!

9.0:1 compression with 27psi and a 75 shot. its been done and put down over 600whp. boost is not an issue till you make it an issue by being stupid with tuning. and with the higher compression you can run less boost and be hella faster than someone that has 8.5:1 on 25psi. you could run 20psi and be just as fast if not faster and be a lot safer than the other guy doing it. anything from 8.0:1- 9.0:1 is really really safe.

i just finishe dmy fully built motor with 9.0:1 wisecos, Eagle H beam rods, major head work and basically everything you can do to the 4G63 engine... i'd be happy running 26+psi.. and be fairly safe and reliable to boot.

92awddsm · 03-24-2004, 06:25 PM

Quote:

Originally posted by myblack98gst
hondas are 11:1 or more stock and can see 14-16 psi with very good tuning.

pro drag imports are running around 13-15:1 compression with sometimes 40+ psi of boost.. all about the tuning

A stock honda has puny rods and floating cylinders and you can barely get over 8 psi without breaking parts. Without stand alone or zdyne gold ecu, you will never get over 6psi safely or reliably. Take this from someone who has had a turbochaged honda in the past.

crankbender · 03-24-2004, 11:03 PM

Quote:

Originally posted by myblack98gst
hondas are 11:1 or more stock and can see 14-16 psi with very good tuning.

pro drag imports are running around 13-15:1 compression with sometimes 40+ psi of boost.. all about the tuning

No offense man but do you have any links to those 13-15:1 cars.

Heck even the ol turbo celica (circa 2002) that they changed the rules to outlas was running 7.8:1.

14.5 drift · 03-25-2004, 01:56 AM

most of the pro turbo cars I have noticed seem to use 9.0 cr. Not to say others aren't use it, but it works fine for some. I believe ex vi termini uses 9.0 cr in there 1300ps skyline on 30 klgs of boost. Definatly working for some people.

awdtsi601 · 03-25-2004, 02:00 PM

Quote:

Originally posted by 98talonAWD
Tune the engine according to knock, timing, and EGT temps or get something even better... WIDEBAND!

9.0:1 compression with 27psi and a 75 shot. its been done and put down over 600whp. boost is not an issue till you make it an issue by being stupid with tuning. and with the higher compression you can run less boost and be hella faster than someone that has 8.5:1 on 25psi. you could run 20psi and be just as fast if not faster and be a lot safer than the other guy doing it. anything from 8.0:1- 9.0:1 is really really safe.

i just finishe dmy fully built motor with 9.0:1 wisecos, Eagle H beam rods, major head work and basically everything you can do to the 4G63 engine... i'd be happy running 26+psi.. and be fairly safe and reliable to boot.

il prove u wrong right there i drove around for a year on a bone stock gsr motor running a 57 trim 14psi everyday with a vafc and the car ran like a dream still dirives to this day same set up

dsmturboawd · 03-25-2004, 02:57 PM

57trim at 14psi, thats really sweet.