Straight Cut Crownwheel & Pinion
Turbo Mini Forums

Any body had any experience with SC final drives. Im thinking additional noise, but more importantly power losses / gain.

Im currently reviewing my power to weight ratio. My 499kg target is looking quite possible, but still have loads of work to do. I've Realised 10kg loss is equivalent to approx 2.5bhp power. So therefore every 1bhp gained back is equivalent to 4kg saving. Cost per KG at the stage is proving quite expensive. So looking at more cost effective way to improve bhp/tonne.

That in mind, I'm looking at drag from the mechanical fan, water pump and helical crownwheel and pinion, obviously I already have SC Box and drops.

Ive read extensively about the mechanical fan zapping 2bhp on high reving race engines. The electric water pump was never concluded, but may be 1-2bhp. If a SC box gains you 4-5bhp over the helical box, surely the final drive must be another 1bhp. The med one as a wider teech profile and is probibly heavier though.

I have a 3.9FD, but I'm thinking of fitting a 4.2FD for Santapod so I'm at 7500rpm at 100mph terminal speed over the 1/4 mile. Rev limit will be 8250rpm. Problem being that I'll have to swap FD's for combe the follower month, as I was doing 117bhp down the straight in the turbo.

Edited by alaskanow0 on 16th Jan, 2015.

Class C 3rd Place Avon 2011 14.18 @101mph

I have semi helical fd. The extra noise is nice imo, it is dominant over the box and drops but not overwhelming. I honestly dont know whether there was any gain in hp since I rebuilt the engine with different cam and fitted a Salisbury at the same time

I seriously doubt it!