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View Full Version : Crazy engine idea.


wumpus
05-27-2009, 07:14 PM
LSx, but without the transmission. Just take the LSx and bolt the clutch to the differential (either rear mounted or mid-engine, take your pick).

Pros:
Massive V8 power.
Much less weight than nearly any other V8. Total weight (V8+differential vs. I4+transaxle) should be remarkably competitive.
Power should be more controllable. Back of envelope calculations put the force where the rubber meets the road similar to a K20A in second gear*
Difference is, once Mr. K20a changes gear, the horsepower just keeps building in a LSx. If this is believed to be too much power, a different differential can take care of that, and likely add a bit more top speed.
One less major part to install (this assumes a kit built to take such a set up, without one this becomes lost in the undertaking above).

Cons:
Engine mounts longitudinally . While this is normally a plus, cramming it in a standard exo is a stretch.
I really don't expect the clutch to "just bolt" to the differential. That part will also be painful.
Reverse is lost with the transmission. I suspect that kludging some sort of truck starter motor (possibly even to just one front wheel) is the answer, but would have to look up what a goldwing does.
Gears are there for a reason. Launching just won't happen, and don't expect to go more than 135mph (this may be a plus in many exos).

** this appears to be a bit of an exaggeration. I calculated a 02-05 si transmission to have twice the gearing as a 3.73 differential. Assuming a perfectly flat torque curve (for both) this puts the 400hp V8 equal to a 200hp I4 (at 67, in 2nd gear, with the same redline, oops...). Even so, it should be still comparable. Differential selection could be maddening (acceleration vs. top speed, top speed vs. acceleration...) if you are crazy enough to want to go faster (a 2.73 should match a Deronda's top gear, a 2.56 will see if you have the aerodynamics for 200).

Personally I think this works better on paper than it has any excuse to. I suspect that it isn't worth all the custom parts needed to fit the beast into any available exo, but still makes an interesting thought experiment. I suspect that the most feasible car to do this in is RCR's SLC, but between the cost and the weight, you are going to want a transmission on that car.

Ken_Kim
05-27-2009, 09:16 PM
With a lock-up torque converter instead of a clutch, that might be fun. Seamless power delivery. Still no reverse.

Crazyhippy
05-27-2009, 09:31 PM
Could go w/ a sprint car style rear-end in a "normal" car too. Normally it's an in and out lever, no clutch, but a clutch could be adapted.

Just need to have a big TQ curve. Peaky motors need not apply.:run:

cheapracer
05-28-2009, 12:47 AM
Much less weight than nearly any other V8. Total weight (V8+differential vs. I4+transaxle) should be remarkably competitive.
.

LSX = 570 lbs + at least a TQ

K20 + trans = 450 lbs.

wumpus
05-31-2009, 06:27 PM
After further review, this doesn't seem as good as I thought it. While a LS2 does indeed have a "big torque curve (300lbft at 1000rpm), this isn't quite enough. Assuming an 1800lb exo (possibly too hopeful), the single-speed exo can't compare with a stock manual 05 vette in power/weight until after 60mph. Until 30mph it might have half as much. After about 100, of course, it has well over 50% more, and more than most exos (about 4.5 lbs/hp)

As people have mentioned, it might work with a slushbox, but that really doesn't seem like the right direction for an exo. It would probably need a cam for power at/below 1000rpm, and that is a range mostly ignored by the aftermarket (it looks like any "towing cams" are assuming an automatic).

cheapracer
06-02-2009, 10:17 AM
Its a shame about the thinking of an auto as I cant think of a situation where a 500hp+ per ton lightweight car would be slower.

But it wouldn't sell and your Mates wouldn't take you seriously because of preconceptions and biases.