Bridgeport info.

[RotaryProphet]

Originally Posted by RICE RACING

spooling and when and how they make power are two different things, i have done lots of these things and even a bridge port with a small turbo like a GT35R or larger T04Z sill have poor mid range power, its due to the flat torque curve these engines make.

A stock port has massive mid range tq as does not so large street ports, they have a much fuller power band as a result. If you want to improve the response and take into account all the stuff I mentioned in the first post then smaller ports are always better, if your fixed with the block you have then turbine size is your only other option. There is other stuff you can do like shorter exhaust manifolds and smaller intercooler pipe lengths and intercooler volumes that will greatly increase response too.

Excessive Porting of the engine is one of the worst things, and anything you do to it in that race only category makes it much more sensitive to exhaust system pressure and we all know how rotaries hate that. Anyway don't want to come across as a know it all, but i have done lots of these cars with heaps of different set ups and power levels, street to full on drag animals running 160mph in 400m. Me and my friends who do the same talk about this stuff allot and all the old boys say pretty much the same, porting when you are talking turbocharged is one of the last things you should look at and the more you do of it the more sensitive and less usable the engine will become especially for anything driven on the street. The headaches are not worth the crap................. sorry brap hahahaha

I'll throw in my $.02.

I had a very nice stock port 12a with a set of IDA style EFI throttle bodies, custom manifold, and a 3" straight back exhaust. It made 238 RWHP @ 13.5 psi, and it felt -fast-. It also didn't spool until 4400 RPM, thanks to the rather large 70mm turbo on it. As a result of the huge turbo, the pre-spool torque numbers were very high for a little 12a, and of course once it spooled, it was gone.

Then the clutch went out, and as an experiment, we dropped in a bridgeport motor. We had run it NA, and it's balanced and clearanced and setup with carbon apex seals to rev to 12,000 RPM. On Weber carbs, it was reasonably streetable; below 3500 RPM or so at steady throttle it would demonstrate the bucking that N.RotaryTech mentioned. The power became reasonable by 4000 RPM, and at 8000 RPM the power band really started. It also felt very fast, even with stock 12a gears behind it.

Now, putting this bridgeport on, we decided to use the same intake and exhaust setup as the stock port turbo 12a, just bolted to the bridgeport. A rather oversized turbo and a bridgeport... should be really fast, right?

It felt dog slow. It cranked out just shy of 400 horsepower at the flywheel on the engine dyno... but average power across the band was lower than either the NA bridgeport or the turbo stock port. It spooled 1400 RPM faster, but that's thanks to the pressurized air-fuel mix venting straight out of the exhaust via the massive port overlap. I've never felt a car at 14 psi going nowhere fast before. Plus, it was louder, it overheated easier, it idled higher, it still acted like a bridgeport at cruise, which made it unpleasant at best to drive it on the road.

I messed with it for about a 1000 miles, and decided a stock port 13B-RE would be a better home for my turbo and nice intake setup.