hi, i was looking on the forum but couldnt find anything on the differences in the jap-spec CA18 and the non jap spec. is there a difference in power. i know the intake manifold is different. i have both engines. my car originally came with the non jap spec. so would it be alright to change it without big moding or any moding if that, but obviously depending on the power output ill use the one which comes out with more.
thanks
Jap-spec and non Jap-spec
AFAIK they are practically the same.
The Jap spec doesnt come with that excuse for a oil cooler first of all. Then the intake is slightly diffrent, it has 8 ports instead of 4, and in 4 of the ports are butteflies(?) but you dont connect those up anyways so they stay open all the time.
Most people tend to belive when your going for BIG power the jap spec produces a little less. Although im yet to see conclusive evidence of this, and even if its true its not enough of a loss to make me care much anyway.
Hope this helps abit, im sure some spammer 😛 will expand/improve/correct on what iv said
thanks, i think ill use whichever head that is in better nic. thats all i needed to know cause if everyone has there say then ill be in two minds about both and ill say that i should have used the other.
The 4 port flows much better then the 8 port.
The Nico guys have done tests with a flow bench.
I will look for the link
Hi guys,
I recently bought a Jap-spec CA that I am currently rebuilding for my S13.
The eight port CA has two intake ports per cylider and on one of the two ports there is a butterfly controlled both by an actuator and the ECCS.
These ports (with butterflies) are closed below 3800 rpm to aid in low end torque and above 3800 rpm the valves open to increase top end performance... These butterflied ports are also 1mm wider than the ones without butterflies.
One thing im trying to find out is if this system will work with our ECCS systems here in SA??
hope this helps 😉
You will find out the explanation and how to connect it up on here:
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