280 psi in each cylinder = what compression?

[khai_tuan_nguyen]

Hi guys I did a compression check and got 280 in each cylinder, about what compression ration would that yield? If you don't know can you tell me about what compression ratios you have with what pistions.


ie JE 12:1 = 240 compression

etc.

Thanks
Khai

 

[dohch22a4]

My JDM GS-R egine with 10.6:1 compression yields 240 across the board. It's not always linear. It also depends on the condition of your piston rings.

 

[khai_tuan_nguyen]

Anyone else?

 

[hcivic.com]

i would guess in the 12.2-12.7 range

 

[phunky.buddha]

There's no way to really tell. Your compression test numbers depend on many more factors than just your static compression ratio. Cams, rings, valves etc... they all make a huge difference.

 

[posol]

yup.

in all reality, a high compression motor (12+) could easily be in the mid 100's with a compression tester, and a turbo motor with 9:1 could be in the upper 100's/low 200's.

280 is really really high... i'd almost question the gauge

 

[khai_tuan_nguyen]

A high compression is what i wanted to hear. This is the story. I went to go get it dynotuned with hondata and p28. My setup is B16 head, ctr camshafts, stock valvesprings, AEBS intake manifold, type r header, str 68 mm tb, str cam gears, injen intake. Unknown race pistons.

Anyhow they started to dyno it and they could not get the damn thing to stop pinging off idle. The fuel was adequte and they even tried with the timing set at 0 degrees, still pinged. We threw some 440 cc injectos and still pinged. They compression checked it and decided it was because the pistons had like 13 or 13.5 compression and i had to etiher swap the pistons out or run race gas.

So the pistons are coming out. Anyone want some all race pistons.

KHai

 

[Bl6CRX]

post some picks of those domes when you get em out of there, It would definitly have to be higher than 13:1 becuase my friends 12:8:1 setup with less ignition does not ping on 91 all the way to redline

 

[B16]

my motor measures ~270psi across the board on a compression test.. i have 12.3:1 CR toda pistons with stock type R head. i'm running on 91 octane myself with no issues at all.

 

[khai_tuan_nguyen]

So does what the shop say sound abour right.

My compression somewhere in the 13-13.5:1, because it was untunable with 440 injectors on a mustang dyno at even 0 degrees it pinged. Or could it be something else?

KHai

 

[hybrid89]

so a lower compression piston should yeild a lower compression test compared to a high compression piston? (in theory)

 

[NoJokE]

Originally posted by hybrid89@Aug 31 2004, 06:19 PM
so a lower compression piston should yeild a lower compression test compared to a high compression piston? (in theory)

[post=384426]Quoted post[/post]​

Everything else being equal, yes it should. But as they stated in the first few posts, it also depends on your rings and other seals for total compression.

But if all of that is the same then yes, a lower compression piston will yield less compression then a high compression piston.

 

[hybrid89]

I just tested my buddies GSR the other day
81mm
JE 9:1 pistons
400 miles on car so far
165 164 159 164

is that right?

 

[NoJokE]

Seems a little low, but since they are within 10 psi of each other, its good.

 

[hybrid89]

could it be because the motor is still breaking in?

 

[NoJokE]

I PM'ed you as to not threadjack this poor boy.

Start another thread if you want to keep it going or something.

 

[khai_tuan_nguyen]

Bad piston rings = loer compression?????

So what if I had 280 compression on each cylinder, does that sound untunable on 92 octane, hondata and 440cc injectors?

Or could it be something else?
Khai

 

[phunky.buddha]

Originally posted by khai_tuan_nguyen@Aug 31 2004, 11:00 PM
So what if I had 280 compression on each cylinder, does that sound untunable on 92 octane, hondata and 440cc injectors?

Or could it be something else?
Khai

[post=384554]Quoted post[/post]​

It's probably something else. My engine pegs the compression tester at something well above 300psi, and it's tuned to run with Hondata on 310cc injectors without raising the fuel pressure at all.

 

[khai_tuan_nguyen]

Originally posted by Calesta+Sep 1 2004, 07:12 AM-->

khai_tuan_nguyen

@Aug 31 2004, 11:00 PM
So what if I had 280 compression on each cylinder, does that sound untunable on 92 octane, hondata and 440cc injectors?

Or could it be something else?
Khai

[post=384554]Quoted post[/post]​

It's probably something else. My engine pegs the compression tester at something well above 300psi, and it's tuned to run with Hondata on 310cc injectors without raising the fuel pressure at all.

[post=384651]Quoted post[/post]​

Any ideas what it might be. What would still cause pinging in the system even at at next to nothing timing and with plenty of fuel at 92 octane. BTW I put some race fuel of 112 octane mixed 50/50 with 92 octane and its not pinging any more.

Any ideas before i tear my motor apart and lose tons of money?

Khai

 

[phunky.buddha]

Ignition timing maps? There's a lot more to timing than the base measurement.