2020-01-10 - Miata JDM Swaps
I wanted to confirm that a JDM Mazda Miata engine (99-00) is allowed under the swap rules. It was brought to my attention that it may not be and I wanted an official ruling.
The JDM engine is rated at 143hp vs. 140-142hp for USDM. It includes a BP5A cam vs BP4W, the BP5A is advanced 2 degrees but the same lift and duration as the USDM cam. Exhaust cam, pistons, rods, head, block, and everything else in the long block is identical to USDM. It also includes a square-top intake manifold, and 4-2-1 header, although the engine usually only comes with a 4-2 portion.
We've freshened the engine and we had the following Dyno results:
Dynoed at: 151HP with Pulley and SD exhaust (Before Road America)
Dynoed at 132HP w/o pulley and bad self-tune (After Sebring)
Dynoed at 145HP with custom exhaust and good tune (Before Road Atlanta)
Dynoed at 133HP with exhaust cam retarded a tooth and valve spring issues (Before VIR)
Dyno TBD - Added Port and Polish - 21" Intake (The goal is to hit high 150's)
We've confirmed that teams with NA8 (1997) engines dyno'ed in the 145s and we expect the USDM 99-00 motor to hit 150-160 since it has a much better head design.
We do not see our JDM engine performing better than the USDM motor.
There are a lot of these on eBay and they are easier to source than the USDM motors, which is why we got it to start.
If you can let me know ASAP it would be greatly appreciated as we are in the final stretch before Road America.
We're investing a lot in these races and I want to be sure we are 100% legal.
***NOTE: The JDM 90-00 motor includes a VICS Manifold NOT SQUARE TOP, and we've been running the VICS not Square top, but we improperly identified it as a square-top previously.
You must have a full JDM engine swap (and claim it), plus proof of purchase of a complete engine and number match to use the JDM square top intake, JDM cam, and JDM 421 header. If not you need to claim points on the intake, cam, and header.
As well I have websites talking no hp gain, 3 hp, and 9 hp. Make the best effort to validate the claim of horsepower increase at or under the 3% max.
RESPONSE: I found Mazdas official power rating from Japan:
It's 145ps which is 143hp when converted. Tech will print and add this to our binder.