Building a B6T for 200rwkw

[sabretooth]

B6T comes with better designed flywheel which enables a larger diameter clutch plate. It looks a lot heavier, but it is actually exactly the same in both static weight and rotating inertia. I have measured and compared this myself. I still cannot believe they are the same, they look so totally different.

B6T also has alloy sump with proper baffles, ordinary B6 uses open steel sump with no baffles. B6T has oil squirters under the pistons, and a water to oil heat exchanger mounted underneath the oil filter.

Not relevant in this usage of the motor though. And I'm reasonably sure that the B6 has the oil squirters too. My BP does, anyway.

B6T has much thicker conrods and larger diameter conrod bolts. These beautiful conrods are an upgrade for a BP turbo motor. Very strong rods.

I can attest to the size - I bought some.

Sure you can put all the good bits into an MX5, except for the oil squirters. That would be a hell of a difficult and expensive job to do.

All things considered a genuine B6T is absolutely the very best way to build a really strong turbo bottom end, because everything is already there.

And you can always sell the funny unusable Laser cylinder head and manifolds to the Laser guys. But the bottom half of the B6T is pure gold.

Welllll, I'm kinda inclined to disagree just a little. Unless minimum cost is a driving factor personally I'd start with the MX-5 equivalent of the motor so you don't have to go messing around with ignition systems and sumps from the engine you're replacing. New B6s can be had for cheap, and B6T rods pop up from time to time on eBay. I wouldn't personally be too comfortable putting in an engine I didn't know the history of in an application designed for power - I'd be wanting to give that thing a full rebuild first to give myself confidence in it.

[Sean]

Now with a BPT engine am I looking at the same constraints?

A stock BPT (from an NA model MX5) has slightly lower compression than a B6, which means you can safely run a little more boost and timing, other than that the heating and other issues will remain teh same or similar, a GT2871R will be a perfect turbo for 200rwkw on a 1.8...

Sean: from what I remember reading the US guys seem to say around 350rwhp is the limit of the gearbox. So I would have thought the diff and flywheel/clutch from the 1.8 would be the only required mods for 200rwkw.

350hp is about 244kw, I suspect there is a fair bit lost in the difference between our dyno's and the US ones, thioer power figures often seem a bit happier than ours...

I know I've broken one 1.8 diff, and know of at least 2 other aussie cars that have done the same.

As for gearboxes, I guess it's upto how you drive them, I'm sure Guglur used to spit boxes fairly often with about 170kw, I've spat them out as have a number of other turbo MX5s with around (and less than) 200rwkw.
I guess it comes down to teh stree you place on teh box, mine see a fair bit of abuse due to my driving style and the fact the car has competed in a few ANDRA rounds and track days...

More brocken boxes here: http://www.aus-cartalk.com/viewtopic.ph ... 257#253257