whats the difference between the 2?
 

A guy I know just got an FC and was telling me that it had the jspec motor in it and everything. What was different from the US spec T2 motor and the Jspec one? What can I look for on the motor itself to tell if its jspec or US spec? Sorry, I don't know too much on the history or anything about the FC's. It's a '90 but I don't know what year the motor is. Not sure if it matters or not, and it is a 5 speed. I also tried searching and couldn't find anything that was helpful or answered my questions for those who will tell me to use search, lol :p:. Anyways, thanks in advance for any input.

All jspecs after 85 were turbo, so I assume we're talking about a turbo II here.

One thing that gives it away, the intercooler on an aspec car has the fins painted black, while the jspecs are metal. The aspec IC says "13b intercooled TURBO II" and the jspec says "Rotary turbo with intercooler".

Also, the jspec will have a large metal nipple on the passengers side intake manifold, for the brake booster vacuum supply, the aspec does not have this (it is located on the throttlebody).

As for the engines themselves, they're identical to each other aside from small emissions differences and those listed above (comparing equivalent years). The small power difference between JDM cars and aspec cars was supposedly in exhaust and ecu programming changes.

thanks man.

I've seen plenty pics on this forum of unpainted US-spec IC's.
The Japanese cars actually have slightly lower official power ratings. They're listed as 133kW (178hp) for S4 and 146kW (196hp) for S5, as opposed to 180hp and 200hp respectively for US versions. Perhaps Mazda USA just rounded up. ;)

also from what i have read on hear ( correct me if i am wrong) but dont jspecs not list as a turbo therefore getting a lower insurance rate?

NZ, every source I have read listed s4 jspec 7's at 200hp and s5's at 210-215.

This just all feeds the jspec craze, IMO. First they sit there and tell you that most all jspec cars/engines have higher power ratings than their equivalent US spec mates, because japanese emissions requirements are not as tough.

Then, they turn right around and tell you that jspec import engines have 30k miles, and that they are junked because of japan's stringent emissions/inspection laws.

Because of all the BS that gets fed, I bet a man could take apart a bunch of jspec cores and sell the drained oil as jspec racing oil on ebay, and probably get bids. It is ludicrous.

Jeez, I wish. ;) Other than the 215hp Infini (which had more power than a standerd S5 remember), there's no significant difference in official power outputs between Japanese and American FC's. Those figures I quoted are from the Aussie car mags, and to the best of my knowledge the cars sold in Japan were exactly the same.

You're right about the whole "JDM" thing though, although there are more powerful Japanese versions of lots of engines. Just not ours. ;)