So that SBY Miata I mentioned on the weekend has surfaced again on CL. This time there is a little more information in the ad and it mentions that it's an automatic converted to manual. A quick Google suggests that the engines fitted to slushbox cars were detuned and have somewhat different electronics, does anybody (Keith?) how that affects the conversion and potentially the ability to drop in an 1.8 and/or boost the thing?
Main exercise with this is to get a cheapish track car again and I don't really want to convert the Mini Cooper to yet another track car. It'll do in a pinch, but I suspect I'd end up throwing too much money at a car that will then be unpleasant to drive on the street, so I'm trying to keep the mods on the R53 and the ND in the realm of pleasant street driving.
I'd find out if they swapped ECU's as well. The Automatic ECU is a bit different due to the auto shifting and I know the throttle bodies were different as well.
Boost that 1.6L. The automatic trans 1.6L was about .5 less compression wise, which should allow a few lbs. extra boost.
Ah, I forgot - doesn’t the 1.6 auto have a real TPS and not the on/off switch like the regular 1.6?
In the NA, the difference between the auto and manual motors was the cams. Get a set of cams from a 1.6L manual, you’re good to go.
If you want to go turbo, Megasquirt is your next step. Buy it, install it, learn to tune. It’s really not bad to learn. I made a MS2 work just fine, but if I had to do it again I’d plunk down the cash for MS3. The variable TPS in the auto motor will make it easier to dial in acceleration enrichments.
Next, injectors. Flowforce 640’s are reasonably priced, idle great, and can handle as much power as you want to make.
Lots of options for turbo kits, but I’m running the MKTurbo kit and you absolutely cannot beat the performance for the price. I’ve got 5 track days on mine now with a pretty conservative tune, not a single issue.
I thought it was more than the cams (fornetti14 also mentioned the .5 lower compression). Cams should be reasonably easy to do when changing a timing belt though...
Re the turbo kit I don't really have the time to mess about building my own, so I'd probably be looking at the appropriate FM kit.
If you're doing a 1.8 swap and an aftermarket ECU, it's now the same as a manual car. And yes, the 1.6 autos did have a real TPS so your new ECU will be a happy puppy.
Cams are different, compression ratio is 9.0 instead of 9.4. If you want to REALLY boost it, then that's good.
Thanks Keith!
If for some reason I wanted to keep the 1.6, would there be any performance advantage of boosting the lower compression auto motor (potentially with the manual cams) over the regular one?
Of course just dropping in a 1.8 would be tempting.
You can ram more boost in there before you hit the detonation threshold, but you'll pay for it in off-boost response. It's the peak power/laggy option. Of course, 9.0 isn't terrible for a compression ratio. Nothing like the 8.2 or whatever the GTX used.
