123quattro

There are 2 advantages of using a flat plane crank.

1. The crank is about 10 pounds lighter than an equivalent 90* crank. That will give you about 50 more whp in first gear due to not consuming engine power by extra inertia.

2. The firing order allows better exhaust scavenging because cylinders can be paired that are 180* out of phase.

Sound is a function of displacement, tube size/length, rpm, cam timing, and compression ratio.

ptuomov

The only reason to do something like this is because you can. There's no logical reason.

One can create a close to the same high rpm sound with headers and exhaust.

One can make more power with the 928 engine in so many different ways that are way more cost effective.

If you were in a five liter otherwise unrestricted racing class, the maybe. But even then, the first $500k could be spent with a higher return.

But that's besides the point. There no need for anything we do to be logical. Because I can is perfectly sufficient reason.

123quattro

Ford and GM have been playing with this in the last few years. It's only to improve 0-60 times. It will get you ~.2 sec. Ford is the only one to think .2 sec is worth all the terrible NVH that goes along with it.

James Bailey

[QUOTE=123quattro;12115827]......
1. The crank is about 10 pounds lighter than an equivalent 90* crank. That will give you about 50 more whp in first gear due to not consuming engine power by extra inertia.

I think you are way over on the HP "savings" due to the relatively small diameter of a crankshaft ..... I know light weight crankshafts are popular and some are gun drilled too to hollow out the centers which is the least efficient way to reduce the inertia as it is the centerline of the mass...

ptuomov

Bryant started gun drilling racing crankshafts partly because that got them just under the UPS maximum shipping weight...

[QUOTE=James Bailey;12116246]

123quattro

James, I wasn't guessing those numbers.. I used to work in GM Powertrain. I have friends that work in Ford and Roush powertrain.

James Bailey

So you calculated it ??

James Bailey

so a typical 350 chevy crank at about 54 lbs would require something like 250 hp just to accelerate the crank ??? let alone the rest of the rotating mass ? flywheel ,drive shaft clutch......forget about moving the car since most 350 chevy engines do not make 250 HP
Yes taking it to the absurd is but one way to test a theory...

James Bailey

Those with an interest should read about the olds Indy V-8 used in 1999 at the Indianapolis 500 venue 4 liter V-8; problem was it sounded like NASCAR......rule changes for 2000 included a flat crank and a reduction in size to 3.5 liters to improve the SOUND make it "more exotic"... no mention of any improvements in power output .... just fixing the sound

mark kibort

first, what theory are you testing?

I think we need to go over the inertial mass vs HP discussion.

if you remove weight from the crank, pistons, flywheel, driveline, etc, the HP effect changes in what gear you are in.
4lbs off the flywheel (if the weight is distributed 9" evenly) is like 26hp in 1st gear, 15hp in 2nd, 5hp in 3rd, 1.5hp in 4th and less than 1hp in 5th. (for example)

Now, we are making an assumption of a 10:1 power to weight ratio. 3000lbs / 300hp for example... however i can equate the hp savings to a weight savings, and then you can calcuate it from there.
so that 4lbs is like removing 260lbs out of the car n 1st gear
150lbs in 2nd, 50lbs in 3rd, 15lbs in 4th and less than 10lbs in 5th.

Yep, good approximation for all the right reasons!

James Bailey

If it were only so simple