8.5:1 compression people, whats your compression?

[anomalyinva]

Well, I ####ed up the Galants motor. BCS broke so every time I floored it I hit 20+psi, o2s went as low as .6 on pump if not lower, the motor has 670 miles on it. This went on for probably 100 miles until I could check it out, not realizing how low the o2 was going as I didn't have a data logger or boost gauge hooked up. 8.5:1 .20 over ross pistons, compression is 150 150 150 160 =/ I guess I learned a very expensive lesson =/

 

[2gGSX]

For stock 2g turbo (8.5), the standard compression is 178 psi with service limit at 133 psi. Personally I'm at 165 psi across the board, with 132k miles, mostly stock for about a week more

 

[Mirage2LTurbo]

Typically if you put 8.5:1 compression pistons in a motor, the compression will be 8.5:1. Other factors like milling the head, head gasket thickness, etc, also come into play.

Did you run that test on a hot or cold motor?

 

[kalla]

In my rebuild I did the same pistons and overbore and dialed up 170 psi across after breakin.

 

[anomalyinva]

In my rebuild I did the same pistons and overbore and dialed up 170 psi across after breakin.

Thats basically what I thought. It REALLY sucks to have spent a year and a few grand building this motor, only to have the BCS #### up and hurt it. At least I didn't blow it, but I know she won't ever be as strong as she could have been.

 

[anomalyinva]

Typically if you put 8.5:1 compression pistons in a motor, the compression will be 8.5:1. Other factors like milling the head, head gasket thickness, etc, also come into play.

Did you run that test on a hot or cold motor?

Hot, it has a Mitus 4 layer HG and the head was slightly milled, basically they offset each other. Due to the damage it's basically like I went with a stock rebuild. =/

 

[diambo4life]

Hot, it has a Mitus 4 layer HG and the head was slightly milled, basically they offset each other. Due to the damage it's basically like I went with a stock rebuild. =/

It doesn't sound TOO bad. My buddy had about the same compression as you with a milled head and thicker Cometic HG but he was running the Wiseco 8.3:1 pistons.

 

[anomalyinva]

It doesn't sound TOO bad. My buddy had about the same compression as you with a milled head and thicker Cometic HG but he was running the Wiseco 8.3:1 pistons.

I've got no one to blame but myself. I made the decision not to install the boost gauge thinking I wouldn't need it as I was running off the BCS. I was gonna wait until I could install the EGT and datalog it before I did anything. Oh well, eff it.

 

[Turbo Talon DL]

Its ok man...I WAS running 9:1 comp with Arias pistons. I dont know if i want to get another set after they started slapping really bad . I had 190psi accross. I dont know what im gonna get now after i get the pistons and bottom end squared away. I hope i can still find some 9:1 cast pistons so i dont need as much boost.

 

[1fast97gsx]

Well, I ####ed up the Galants motor. BCS broke so every time I floored it I hit 20+psi, o2s went as low as .6 on pump if not lower, the motor has 670 miles on it. This went on for probably 100 miles until I could check it out, not realizing how low the o2 was going as I didn't have a data logger or boost gauge hooked up. 8.5:1 .20 over ross pistons, compression is 150 150 150 160 =/ I guess I learned a very expensive lesson =/

at least the numbers are within 10% right . Actually I did the same thing on my first motor. ( also ross pistons ) Sucks.

 

[Awdboost]

at least the numbers are within 10% right . Actually I did the same thing on my first motor. ( also ross pistons ) Sucks.

Why do you think Ross Piston Suck??? I've heard people say that but no one back it up. I'm not using them but I'm just curious. I'm running 8:3.1 in Wisco.

 

[peregrine]

elevation makes a difference in compression tests so keep that in mind.

 

[98TsiAWD]

Why do you think Ross Piston Suck??? I've heard people say that but no one back it up. I'm not using them but I'm just curious. I'm running 8:3.1 in Wisco.

He never said ross pistons suck, he said the situation sucks.

 

[Awdboost]

He never said ross pistons suck, he said the situation sucks.

Oh, My bad. Sorry? But I have heard that before.