A question of carb sizes verses torque, verses power.

[Gary71]

Twin turbos. Sounds good. I do prefer symmetry!

Relative to some of the ideas you been throwing around a turbo conversion is surely towards the cheap and simple end?

Even if you ditch the carbs and go EFi at the same time.


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[fetuhoe]

Graham,

The 4speed transaxle is $6000 which is not so bad when you factor in the $3000 you could get for the 915 which must be quite limiting.

[911hillclimber]

The one box that would fit would be the Hewland FT 200.
This car once had 500 bhp (Ford Group B 200 engine) and an FT.
Oddly it survived as it is limited to around 200 lbft.
When I first saw the car it had a Cossie turbo 2 litre and a fresh FT fitted.
Could not afford that drivetrain, but in hind sight...
A real FT is about 5k but first gear has to be broadened so removing reverse.
Any box must have reverse.
Elite make a cheaper version, but might be frail.

In all these real race boxes, dog changers the lot there will be costs for the adapted ring, clutch and input shaft, add another 2 k min.

[Sam]

I think the Elites are sorted now. There's a 500bhp YB Turbo Westfield that's been running one for a few years.

[smallspeed]

If it's running out of puff above 6000 what is the limiting factor - cams? assume not fuel if you are questioning carbs being too big.. Are you running out of ignition timing at higher revs?
Definitely worth calculating total inlet tract length and see if you would benefit from more or less length/ diameter.. Possibly more useable rev range would save you a change in/out of 2nd?

[911hillclimber]

Interesting about the Elite boxes, thanks.
The cams stop the engine I think, but the self imposed 6400 limit is due to the rotor arm I have.
The Porsche limit is about 6300 iirc if the tachometer.
Doubt the engine will run more than 6500 before tempting fate.

It's gone bang once before at 6300 ish, massive damage to the engine, 4K damage to my wallet and poor machining by a specialist etc.

[smallspeed]

Makes sense.. In that case I guess see what you can do for torque.. Would be interesting to play with velocity stack length and see if you can bolster thr torque rather than chase a BHP number.. I believe emerald sell those adjustable stacks in the article I linked - they didn't used to be too expensive

[911hillclimber]

That is an interesting article from Dave Walker, just read it through.
The PMO stacks are quite short to fit into the air filter. There are theories to where the filter top plate is above the trumpet top too...
Food for thought.