9:1 or 8.5:1

01-14-2005

Would you recommend 9:1 OR 8.5:1?If you had the choice which would you go. I am pretty set on the 9:1.

Current mods are:
Intake
1g Manifold
Greddy IC pipes and Intercooler
Blow off valve type-S
Exhaust
EVO exhaust manifold
EVO O2 sensor housing
3inch DP
3 inch Cat-back
Turbo
Garrett TO4b
Ignition
MSD DIS 2
Magnecore
NGK's
Fuel
Walbro
B&M regulator
Drivetrain
Team Rip Engineering Race tranmission
Fidanza Flywheel
Clutch Master's Stage 3

**Shane@DBPerformance** · 01-14-2005

8.5:1 to 9:1 isn't a huge difference. 8.5:1 will be easier tune and have more potential on pump gas though.

**1ViciousGSX** · 01-14-2005

Quote:

Originally Posted by ecoli

8.5:1 to 9:1 isn't a huge difference. 8.5:1 will be easier tune and have more potential on pump gas though.

Agreed.

awd-drifter · 01-15-2005

what's the c/r on the 4g63s? I have heard of it being 8.8:1? Unsure, but I always had something like that in mind, like, how do you lower the 4g63's c/r? Hahaha, I'm a newbie at engine stuff like, so thanks for the help!

Super Bleeder!! · 01-15-2005

on 1gs its 7.8:1, on 2gs its 8.5:1

01-15-2005

NOTED Thankz

01-15-2005

I think I would go with the 8.5:1

**Kracka** · 01-17-2005

8.5:1

Tsi · 01-17-2005

What CR to run is going to be entirely up to you. A higher CR will produce more power at a given level of boost. It will also spool a turbo faster. Every good thing has its price though...with a higher CR you're going to have to do a better job tuning to avoid knock and detonation. You're going to have to run lower boost with a higher CR, than say with a lower CR. 8:5:1 seems to be the way to go for the 4G63T's

santa · 01-21-2005

I thought taht 8.8:1 was ideal for boosted cars? I would also have to say I would look into getting some type of tuning device(unless you have one and didn't list it). Are you going to be going with the 2.0, 2.14, 2.3, or 2.4 engine?

Kevin

**Shane@DBPerformance** · 01-21-2005

There is no such thing as an ideal compression ratio. It all depends on what gas you want to run, how close to the edge you want to tune the car, how hard you want the car to be able to tune, how much responsiveness you need. Lower is going to let you run more boost on pump gas, but the car will be a bit more doggy out of boost and you gas mileage will not be as good. There are some guys out there running built motors with pretty low compression. Lancerman runs 7.7:1 compression in his AWD 4G64 Lancer that runs 10s on pump gas. There are some other guys out there too that run low compression so they can run insane boost levels on race gas. Extreme's 8 second AWD Talon was running 7.5:1 compression pistons last I read.

Raptor · 01-21-2005

Depends a lot on what the application is. If you are going to build a car more for street and DD and care less about maximum power, go with the 9:1 so you have better spool up and it is more tollerable off boost. Otherwise, there are arguments to be made for going with less compression as Shane mentioned. You can compensate for the lower compression with more boost and end up with more air in the combustion chamber (more volume), combined with long rods causing more dwell time at TDC to build pressure, which will create a lot of power. There are a number of other factors to consider as well, but there is enough info in this thread to get the decision made.

santa · 01-21-2005

I see what your saying about tuning as far as c/r.

**Goat Blower** · 01-22-2005

9:1. Don't be a pansy.

01-23-2005

Well after talking to the owner, and listening to him i realized how much abuse this car has in its future. I see the lower compression being a better way to go as far as reliability issue are concern.Not sayin that the CR will directly affect reliability but the fact of the hand holding the bosst controller, once it is no longer in my possesion.That is how it got in to my hands in the first place.

santa · 01-23-2005

What the heck did you just say at the end? That makes no sense....and niether can the guy next to me...

Pimpin Dsmstyle · 01-24-2005

dude was messing the the boost controller ( turning it up im sure) and obviously went higher than the engine could handle. This guy is not the owner. I believe someone is coming to him for help.

awd-drifter · 01-28-2005

If you got a low c/r of say...8.5:1, is it good for the 4g63T motor to go straight to NOS, because there is more air to suck in? well, I thought about it, but wouldn't NOS work to much on the stock turbo? Man, I have alot to learn about these kinda things before I get my DSM, just asking through curiousity though. Thanks!

**Shane@DBPerformance** · 01-28-2005

More air to suck in? What do you mean?

Super Bleeder!! · 01-28-2005

he probably thinks that if the piston has a lower compression then there must be more volume in the cylinder and hence more room for air. i don't even know how to being to explain this one...gahh