LOWER COMPRESSION WANTED ON TURBO 4g63 REBUILD

[garputo2]

I posted another thread nobody responded. I need to know when getting wiseco or ross whatever high end pisons you go with they change the compression ratio. This being said I have 8:5:1 wiseco sell the 8:3:1 or the 9:0:1 I think you want the lower numbers when running turbo

 

[spooled_u_1st]

Lower compression is for using pump gas. If you want to run 9:0:1 pistons, you would want to run meth injection or e85.

That is if you want to run high boost.

 

[garputo2]

so if I am using pump gas then the best would be staying at oem 8:5:1 or less rather than anything higher?

 

[Nati0nalxCrisis]

8.5:1 Would be like a DD, 9:1 would be good for a quicker car, gets a little more outta everything, your turbo would spool a little faster too with 9:1

 

[Colt4G63 also]

I use CP 9:1 pistons, and 93 octane pump gas. I was able to tune it to 17psi with about 17 degrees max timing. DSMlink estimates I make about 375 HP on an EvoIII 16g. I would like to get meth injection and try to squeeze more out of it, but the car is hella fun to drive, and meth is defineitly not required.

 

[Nati0nalxCrisis]

Yeah thats what I was thinking, I know if you go higher then 9:1 It'll just be ridiculous and you'll end up blowing the head off, or something catastrophic like that, keep in mind only muscle cars use really high compression cause theres no forced induction going on. 9:1 would be a perfect (performance) compression. If your not looking to keep upgrading then just stick with the 8.3:1 or the 8.5:1, There'd be no point in getting 9:1 if your not looking to go over 350 WHP.

 

[garputo2]

I am hoping to get to figures around 350-400 400 being my long term goal on the car. If I use the 9:1 throw it all together will I have big running problems using stock timing before getting dsm link and tuned. I wanna be able to put it back together and run it.

 

[Nati0nalxCrisis]

I can't see why your timing would be off using 9:1 compression. Keep in mind, most people dont change their timing at all when upgrading a car.

 

[garputo2]

Okay well that is good to know I guess I was confused fron previous reply of 17 max timing. So going with the 9:1 with stock specs on crank and bore and stock head will be fine and the way to go I am seeing. But if I stick to 8:5 it will be slower boost response. But with the 9:1 it will be easier to handle over 350 psi in the lower end using the stock 93 octane.

 

[Colt4G63 also]

For timing you should be safe since you have a 2g. 1gs have a way more agressive stock timing map that would hit upwards of 24 degrees max timing at WOT. IIRC 2g timing maps won't exeed around 17 max at WOT, so you should be fine. If you have really big HP goals, you may find it easier to tune with the 8.5:1 pistons, because you will be able to push the boost higher before you run into difficulty preventing knock.

But with the 9:1 it will be easier to handle over 350 psi in the lower end using the stock 93 octane.

This statment is probably off. 9:1 pistons are harder to tune with, because the higher cylinder pressures will cause pump gas to detonate more easily. They may give more power on two otherwise equal setups, but they will become un-tuneable at a lower boost pressure than their 8.5:1 counterparts.

In other words: I might be able to tune to 375 HP at 17psi with my 9:1s, and your 8.5:1s might only make 325 HP at 17psi, but you may be able to turn your boost up to 25psi and make 420 HP safely, while I have hit my limit at 17psi. Understand?

 

[99gst_racer]

Lots of misinformation in this thread.

9:1 is hardly too high and is pump gas friendly. A higher CR will offer a bit more off-boost response - which is great for a street driven car.

I am hoping to get to figures around 350-400 400 being my long term goal on the car. If I use the 9:1 throw it all together will I have big running problems using stock timing before getting dsm link and tuned. I wanna be able to put it back together and run it.

As long as you're not running crazy-high boost pressures, you'll be just fine running on 9:1 pistons on a factory timing map.

Keep in mind, most people dont change their timing at all when upgrading a car.

Of course they do - it's part of tuning.

 

[garputo2]

So I think I got my answer. if I use good high quaility parts 8:5:1 compression I can use more boost and it will be more friendly to tuning.

 

[dsmfa9nutter]

Use the 8.5's and you'll get where you want to go.

 

[Nati0nalxCrisis]

My bad your right, I wasn't thinking, I was just about to get out of class, had to log off etc.

My thought that I was trying to get at was, most people don't change the timing degree wise a whole lot, change it too much and you'll throw off the balance of everything.

I didn't mean to make it say that noone changes it, but you can get along just fine without changing it.