JDM vs Other CA18DE compression ratio

[exacyzm]

I have read that the JDM CA18DE has a compression ratio of 9.5:1, and on the AUS spec (and some other) CA18DE it's 10:1.

Is this correct? I have never seen a JDM engine have lower compression than it's counterparts.

All the stock power figures I have seen are exactly the same for the different versions but I would have thought if the JDM version was 9.5:1 it would have to make less power than the 10:1 versions. It doesn't seem to make sense.

If this is in fact true, what is responsible for the 0.5 less in the JDM version, different pistons, thicker headgasket, a combination or something else?

[Nicksemianiw]

its a 1:2:3:4:5 compression hah

[Fleemer]

actually read otherwise.

JDM/AUS 10.1:1 (or 10:1 w/e)

USDM 9.5:1

canada however got 10:1 too :/ (someone put ca18de pistons from a canadian pulsar, thinking it was 9.5.. turns out it was 10:1 in a ca18det. lol

[exacyzm]

That's interesting. If you or anyone else can find some supporting documentation for the JDM engines having a 10:1 comp ratio that would be great I'd like know for certain.

The engine I'm after the info on is the S13 CA18DE (RWD intake manifold like the DET) if that makes any difference, not the CA18 from the EXA or Pulsar with the FWD inlet manifold.

[boost_boy]

That's interesting. If you or anyone else can find some supporting documentation for the JDM engines having a 10:1 comp ratio that would be great I'd like know for certain.

The engine I'm after the info on is the S13 CA18DE (RWD intake manifold like the DET) if that makes any difference, not the CA18 from the EXA or Pulsar with the FWD inlet manifold.

U.S. CA18's were 10:1 aas well as the Aussie units. The JDM bunch was 9.5:1, but who really cares, they are all convertible or can kick butt in their present trims.

Dee

[exacyzm]

boost_boy do you know what is responsible for the 0.5 less in the JDM engines? Thicker head gasket, different pistons etc?

[float_6969]

If I had to guess, it was pistons.

I'm pretty sure the USDM pulsar's got 10:1. That was how I unded up with the compression that I have. Unless the piston I was sent was from a JDM CA18DE and I was unaware of it.

Regardless, my compression ratio is a little over 10:1 and I used a forged copy of what I thought was a USDM pulsar piston.

[Nicksemianiw]

hmmm I have a jdm silvia, whats a good way to check the compression ratio I can maybe have it done to suit every one haha.

[boost_boy]

boost_boy do you know what is responsible for the 0.5 less in the JDM engines? Thicker head gasket, different pistons etc?

Like the floater says, it's a piston thing man.

Dee

[float_6969]

There isn't really any "easy" way to check it. You'd basically have to take the head off, measure the combustion chamber volume, measure the piston dome volume, know how far above or below the deck the piston sits at TDC, and the compressed thickness of your headgasket.

[Nicksemianiw]

There isn't really any "easy" way to check it. You'd basically have to take the head off, measure the combustion chamber volume, measure the piston dome volume, know how far above or below the deck the piston sits at TDC, and the compressed thickness of your headgasket.

Thats more then i want to do lol, Just thought I would be useful with my JDMness and all

[exacyzm]

That sure would be a lot of trouble to go to to answer a question! If you do let me know.......j/k

Well looking through the spark plug hole the pistons look the same between the 10:1 and 9.5:1 (aus and JDM respectively) engines. Even if the JDM piston is less domed, I just wont see the difference looking at them from the top.

I still find it odd that although the JDM spec engine is 9.5:1, it has the same power and torque figures as the 10:1 engines.

[float_6969]

I think it's all BS. Having seen the dome on this piston, I think they're all 10:1

[Fleemer]

i would have to agree on this one.

I don't know who got the 9:5 info from : /

[boost_boy]

i would have to agree on this one.

I don't know who got the 9:5 info from : /

For final confirmation, why don't someone check the piston grade of a JDM CA18DE and or better yet a US spec CA18DE because the JDM pistons I have says 51Eon all 4 pistons.

Dee