bpaspi

This "mean" or average piston speed is only a rough indicator. Better look at the maximum piston speeds (I use the metric system) :

F20C:
max. Engine Speed: 9,000rpm
max. Piston Speed at 77° crank angle: 41 m/sec
average Piston Speed: 25.2 m/sec
max. Piston acceleration at 0° crank (TDC): 18,741 m/sec2

F22C:
max. Engine Speed: 8,200rpm
max. Piston Speed at 75° crank angle: 40.6 m/sec
average Piston Speed: 24.8 m/sec
max. Piston acceleration at 0° crank (TDC): 16,806 m/sec2

F24C (K24 crank, H22 rods):
max. Engine Speed: 8,000rpm
max. Piston Speed at 73° crank angle: 43.7 m/sec
average Piston Speed: 26.4 m/sec
max. Piston acceleration at 0° crank (TDC): 17,473 m/sec2

based on the max. Piston speed (lube criteria) the equal engine speeds would be:

F22C: 8,280 rpm

F24C: 7,510 rpm

based on max. Piston acceleration (strenght criteria) the equal engine speeds would be:

F22C: 8,660 rpm

F24C: 8,285 rpm

s2konroids

Interesting thread guys, what implications would raising the rev limit have when running a low boost supercharger?

bpaspi

Just make a quick calculation how many air this s/c must pump at max. engine speed.
And this air must be accelerated to flow fast enough within milliseconds into the cylinders. By passing the valves.....

s2konroids

I have no idea where i could find such info, its comptech SC @6.5 psi

bpaspi

The F20C needs 1000ccm (1 litre) air every revolution (two cylinders filled with air).

At 8,000rpm the engine breathes more than 132 litres per second (280 cfm).
At 10,000 rpm the engine need more than 166 litres per second (352 cfm).

I have no datasheet of the comptech s/c, but there must be a diagram indicating at which pressure how many air can be pumped...

Gernby

My guess would be that an FI application would increase the amount of overshoot past the rev limit, but that's just a guess.

The rev limiter doesn't close the throttle, so the air flowing through the engine (and S/C or T/C) would not change when you hit the rev limitter. It just quits providing fuel when it thinks the engine is above the rev limit. Once it starts providing fuel again, the power is 100% back on instantly. There wouldn't be any need to calculate accelleration of the air, since it continued flowing all along.

Kermdaddy

No posts have been made. It will be in a race only S2K. I don't want to lead on too much. He has trouble keeping traction as is w/ 295 R comps. He does have FI. The motor doesn't have to last a terriably long time inbetween rebuilds with regards to autocross level.

H22toF20

This thread has grew nicely

Finally a thread with some actually knowledge behind it.

wadzii

For some reason I thought the OP was asking about an f22c...

I reved my f20c to 9600 rpms for about 15k miles, all the bearings looked good except the one that spun.. it spun due to oil starvation not the revs.

And the car was quite a bit faster shifting at 9600 than shifting at the stock 8900 limiter.

dan_uk

thats good info what caused the oil starvation was it the 00/01 oil bolt thing?