detrimental? I'm thinking with stock pistons and also with a forged.

 

That is a big ugly bitch of a question.

Here's the easy answer.

You want as much piston speed as you can get without breaking your parts.

The long answer involves a lot of work and calculations.

 

Isn't 80 fps the general rule?

 

Depends on a whole lot of things. Quality of your parts, jerk, you name it.

I may be off, but if I remember correctly you can get a LS1 to 120fps pretty easy.

 

hmm....120fps seems a little low. here is what I've got based on a calculator I found:

RPM Av Piston Speed (fpm) Max Piston Acceleration (ft/sec2)
1000 600.92 2136.5
1500 901.38 4807.13
2000 1201.84 8546.01
2500 1502.3 13353.15
3000 1802.76 19228.53
3500 2103.22 26172.17
4000 2403.68 34184.06
4500 2704.14 43264.2
5000 3004.6 53412.59
5500 3305.06 64629.23
6000 3605.52 76914.13
6500 3905.98 90267.28
7000 4206.44 104688.68
7500 4506.9 120178.33
8000 4807.36 136736.23
8500 5107.82 154362.39
9000 5408.28 173056.79
9500 5708.74 192819.45
10000 6009.2 213650.36

 

Look at your chart again.

Divide FPM by 60 and you'll see a peak FPS of 100 @ 10000RPM according to your calculator. I have a calculator I know is accurate at home. I'll see what I can run through it.

 

****...i just was staring it down and realized that its in ftpm not ftps....my bad.

ok..I'm only really concerned to around 8k..and there its only 80.4 or something, so I'm good.

Thanks

 

I think 120 is high. THE BMW f1 engine was rumored to be running at 131fps in 2003. The M3 and s2000 are the only 2 (affordable) production cars that I can think of that break 80 fps.

 

Rule is a mile per minute. Anything above that and harmonics that are detrimental to the engine set in.

Chris

 

At 8000rpm, the max piston velocity of a stock bore, displacement, rod length ls1/ls6 is 131.93fps.

At 6500rpm, it is 107.19fps.

 

5280/60 = 88 ft/sec

 

what calc are you using?

 

this is what I got for a 4.00 stroke

 

A 4" stroke, 6.125" rod, 4.030" bore 408 is 119.4fps @ 6500rpm

 

Proprietary, unfortunately. A buddy of mine physicist who used to do design work for NHRA top fuel teams. Some Nascar as well.