What Crankshaft to Run in High HP Turbo Slant Six
Look up slantracer's posts,he's the one w/the green lancer that match raced and beat the green hellcat at MoKan. He talked about the crank twisting .030+ over the run of a season,switched to billet I thought callies, but may have been Crower.
Others in that power range have actually welded the cranks up for rigidity,so either way,
you'll probably have to have a plan of action above & beyond stock shot peened
or not. Good luck,Me likey your goal,keep us posted!!:burnout:
That is an interersting question, but, I think a stock 4 1/8"-stroke, early forged crank in this application should last a long time. The reason I say that is this: Turbocharged slant sixes that run exceedingly well, like the two engines I patterened mine after (Tom Wolfe's and Ryan Peterson's,) do not run well at rpms over 5,500, making tons (500+) of horsepower without spinning lots of RPM's. That green Lancer that ran off and left the Hellcat relies heavily on lots of rpm to make its (CONSIDERABLE) naturally-aspirated power, but with a long stroke, probably generates a lot of stress on the bottom-end at those elevated revs... I don't know, but I would not count out the possibility that the stratospheric RPM that car turns five times (it has a 5-speed transmission,) on every trip down the drag strip,
might contribute to crankshaft problems, but that's just a guess on my part. Add to that scenario, the high rpm launches it sees every trip, and you have SIX times that high piston-speed phenomenon occurs. Addditionally, if you factor in the "NO LOAD" aspect of the pre-launch rpm, it sounds like that engine lives a tough life...
The hot setup for the turbo cars of messers Wolfe and Peterson involve final drive ratios of 2.76:1. They both found that, after testing higher numerical ring and pinion sets, they both ran quicker and faster with the highway/touring ratios. The turbo's seem to respond well to being "held back," like a nitro motor... go figure!
This makes it possible, if you are going to street-drive your turbo car, to use a cheaper 8.25" rear end since you will have a "one-size-fits-all" ratio all the time, with no need for swapping ring and pinion ratios; one for for the hiway and one for the drag strip.
As i remember, the cast iron crank is somewhat lighter than the forged one, but the bearings are smaller on the cast crank, so the jury is still out as to whether this might be a good choice for a forced-induction application. It should be faster.... once.:prayer:
To the original poster, please keep us updated on your progress in this build. There aren't nearly enough of these car being built, in my warped opinion, given their ten-second quarter-mile potemtial.. Here's mine...