ra12r
Zone Head
Posts: 919
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posted March 11, 2002 03:43 PM
Maximum Piston Speed
What is the maximum pistion speed at which the "air pump" still works?!?! What is the formula for calculating piston speed?!
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mo
Expert Class
Posts: 128
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posted March 11, 2002 04:12 PM
I was wondering how a stroker motor would have the same redline if its determined by piston speed?
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KW
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ROCKET J
Zone Head
Goes to water over a dummy!!!
Posts: 602
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posted March 11, 2002 04:50 PM
Stroke me, stroke me....
Redline is determined by safe engine speed. You would have less of a "cushion" with a stroker, but you still may not be in the area of imminent damage. Most stroker kit makers that I have spoken to say that their engines will go to factory redline with no problem. The engine may or may not be making power at that rpm though.
Rocket
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ra12r
Zone Head
Posts: 919
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posted March 11, 2002 09:59 PM
RocketJ, why would they say anything different?! Anyway my question still stands.......
MO, get out of my head!!! hahaha
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mo
Expert Class
Posts: 128
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posted March 12, 2002 05:27 AM
so a stock stroke motor has several hundred more safe rpm avalible?
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KW
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EastBayDave
Needs a job
Posts: 2245
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posted March 12, 2002 06:25 AM
our tachs are optimistic by ~400 rpm so I would GUESS yes...
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Enjoy the ride!
02' ZRX1200
00' ZX12R sold
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ra12r
Zone Head
Posts: 919
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posted March 12, 2002 02:08 PM
Tech guys,,,,,,,Koz, Y2k, Doug, etc... Please help or a direction to the information would be fine.
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kcadby
Pro
Posts: 1733
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posted March 12, 2002 02:38 PM
Looking for the URL to the software I have (that's expired now) for calculating piston speed...can't find it yet 
In general...the stroker WILL have a lower "safe" RPM becaues the piston travels MORE distance in the same amount of time...I.E. faster piston speed...
The tachs DO read high...and Strokers make more power at lower RPMs which means they "shouldn't??? NEED" to be reved as high anyway...
Where's that dang URL!?!?!?
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted March 12, 2002 03:35 PM
Piston speed is pretty easy to compute:
Piston speed (in feet per minute) =
stroke (in inches) x rpm,
divided by 6
How fast is too fast, you ask? Well 4300 to 4800 is not uncommon in a modern high performance engine.
5000 to 6000 is sometimes seen in drag racing (very short run time and life)
Doug
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kcadby
Pro
Posts: 1733
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posted March 12, 2002 03:41 PM
DOH!!!
Thank's DOUG
NO...I didn't remember that SIMPLE formula
I only remember the stuff I NEED TO KNOW for whatever I'm doing at the time...and NOT things that are "written down"...or the things..."I can't change"...LOL... 
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ra12r
Zone Head
Posts: 919
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posted March 12, 2002 05:32 PM
So this is the formula then?!
Piston Speed ft/min = [Stroke inches(rpm)]/6
And maximum piston speed for a motor to hold together should be <5000ft/min. With 5000ft/min being where the factory rev limiters are set?!
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kcadby
Pro
Posts: 1733
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posted March 12, 2002 10:52 PM
No...it's...
55.4mm (ZX12s stroke) X .03937 = 2.181098 inches
2.181098 (ZX12s stroke in inches) X 11,870rpm (stock ECUs "usable engine speed" according to manual) = 25889.63326
25889.63326 divided by 6 = 4,314.9388.....ft per min piston speed...
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ra12r
Zone Head
Posts: 919
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posted March 13, 2002 07:06 PM
Thanks Kevin! I have made my calculations, now what is the piston speed before the "air pump" efficiency no longer works......?!?!
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Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
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posted March 15, 2002 04:11 PM
Well, my 2 cents...
what heppins in most modern engines is the inability of the rings to seal. Extra rod strength is always factored in from the start by the factory for reasons I cant go into here in a pay per hour computer in Mexico.
But trust me its at least 30% extra.
the zx12r is in a position to make more HP than most bikes because of the BS ratio.
the piston speed is lower on the zx12r than the rest of the class at a given speed. This is good for us.
if you guys want to go over 5000 fpm mps then its possable... its just gonna cost ya. drilling or having your pistons drilled is not big deal.
just have it done right.
si?
This Mexican keyboard is killing me.
time for another Dr Funk... chow
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Y2KZX12R
CompetitionCNC.com
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