Y2KZX12R
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posted November 10, 2006 07:06 PM
 Edited By: Y2KZX12R on 10 Nov 2006 19:42
Safe RPM limits for the zx12r...
Well with all the talk lately about raising the rpm limits of the zx12r engine I thought I would post some numbers that may or may not scare you.
Max piston velocity....
should not exceed 4500 feet per minute or 51.1 mph for sustained rpm racing and drag engines can live with higher piston speeds with gas ported pistons. Ring seal is the issue here. The highest piston speed is at 50% cylinder volume and thats at 83 degrees ATDC on the stock zx12r and 82.7 degrees with a 60mm stroke.
55.4mm stroke 11,600 rpm 4026.6 fpm
60mm stroke 11,600 rpm 4360.4 fpm
55.4mm stroke 13,000 rpm 4512.6 fpm
60mm stroke 12,000 rpm 4511.0 fpm
Max piston acceleration...
should not exceed 150,000 feet per second or 4658.4 times G.
At 150,000 fps a 1 pound piston and a 2 pound rod would load the rod bolts at valve overlap TDC with 13,975.2 pounds of tension. Max piston acceleration is at TDC and BDC.
55.4mm stroke 11,600 rpm 128,505.2 fps
60mm stroke 11,600 rpm 134,068.2 fps
55.4mm stroke 12,500 rpm 149,219.2 fps
60mm stroke 12,250 rpm 149,514.0 fps
So..... stock stroke and stock length rods, when above 13,000 rpms will most likely need gas ported pistons. And to rev above 12,500 rpms you should have carillos.
And a 60mm stroke and stock length rods will most likely need gas ported pistons above 12,000 rpms. And to rev a 60mm stroke 12r above 12,250 rpms you should have carillos.
Also, this is all subject to how long you want the engine to last. Running an engine on a continuous basis at these extremes wears the engine out a lot quicker as you would expect.
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osti33
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posted November 10, 2006 08:37 PM
Great post Jim. Thanks. 
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entropy
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posted November 10, 2006 09:36 PM
yeah!!! I agree.
GREAT stuff, Jim!!!
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chrisdhall
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posted November 11, 2006 07:24 AM
Just a couple of minor points. Units of acceleration are in feet per second per second.
Max acceleration is at TDC. BDC is about 50% of the TDC value. See here: http://www.epi-eng.com/ET-PistnVelAccel.htm
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Y2KZX12R
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posted November 12, 2006 03:35 AM
quote:
Just a couple of minor points. Units of acceleration are in feet per second per second.
Max acceleration is at TDC. BDC is about 50% of the TDC value. See here: http://www.epi-eng.com/ET-PistnVelAccel.htm
Good points Chris.
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flite leader
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posted November 14, 2006 03:23 PM
Edited By: flite leader on 14 Nov 2006 15:27
for many years.......more than a decade
roadrace engines have exceeded the holy grail of 4500 ft per sec
2 strokes & 4 strokes
engines have been turned regularly 17k......
many motoGP marques
with an over rev usually of 1000..... 1200 sometimes 1500rpm
most europeans tune in an over rev to their engines
have for decades
several years ago doug meyer said a 12r could rev
safely to 13....14k
it does seem that 7000....7500G's
is very significant......gravity NEVER goes to sleep
yet making parts lighter works.....
many swear by Carrillos
most europeans......DO NOT !!!!
then again "sprints'........or drag racing is Not really that big in europe
no less a Drag engine that operates in a very.....thats right
a VERY Narrow range of RPM
while punching the shift button
& usually passing thru the peak torque maybe once a pass
should fare better than a roadrace engine
especially somewhere like the IOM
true while a roadracing engine
built different.....under a different tune
is up & down the rev range
Total time at redline & above red line(the over rev)
easily exceeds drag engines
bulit properly most dont find the elevated rev ranges a problem
many american(AMA) teams remark tha WSB engines have more
HP & rev range than their factory counterparts
here in the states
mat mladin having stated that recently
5000 ft per sec was exceeded decades ago
some teams now to date are regularly exceeding 6000ft per sec
as i think you will see in the up coming motoGP season with the 800's
the 1000's werent blowing up like popcorn
while some teams...... maybe even many will have problems this year
Honda had a v 125 that revved to 22k .......Forty(40) years ago
a six that rev to 18k........40 years ago
totally NOT as a result of unobtainum !!!!!!!!
or huge $$$$
7 todays technology was in its infancy
same engine today with current tech
& advance probably make 30% more power.......at least
all of this is old news
no less there have been F1 engines
that if they adhered to 4500.....4800 or below 5k ft/sec
they would simply park em ...!!!!!!!!!!!!!!!!!!!!!!!
it is extremely safe to stay in the 4's
without a doubt
& if you are advancing HP in tthat range
why not
others have moved on......& Higher
hell they have nascar engines that turn 10rpm & stay together
practice....race & the obligatory burnout
& blocks that get REUSED>>>>>>>>>>>>>>>>>>>>>>>>>>>!!!!!!!
as was in Hondas engine program
youd be surprised how little wear a properly set up race engine incurs
2-3 engines blow during the race at Indy.......not many
1 or 2 a race..... & not every race at Nascar
sure some go soft during practice............to the rear of the field
an engine blowing F1 car .....or motoGP
during a race is rare indeed
somewhere between your 4500ft/sec
& your max piston speed & some rave engines out to 7500g's
is a Workable solution
many have ben residing in for quite some time
in fact a comment was made just this month why
the R1 wasnt upgrade to similar specs as the R6
simply not in the same neighborhood
yet if they were to race it as they have.....the "7"
or as they Will with the new 800's
they will pop that cheery
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Y2KZX12R
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posted November 14, 2006 06:27 PM
Yes, you can exceed all those numbers and race engines do on a regular basis. But durability and safety are a major factor on a street motorcycle.
Also F1 engines are in a totally different league. You have to compare apples to apples.
Custom stepped ceramic ground rings and composite cast pistons arnt in the price range for the average zx12r builder.
And thats what this post is about. Its about whats an acceptable balance between risk and RPM with stock components or carillo rods. Nothing more, nothing less.
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flite leader
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posted November 16, 2006 02:57 PM
air valves......electric vavlves
traction control?????
with manufacturers like honda.........
much trickles down to road going & other performance vehicles
ducati & ferrari collaborating for motoGP
race & performance engines benefit Greatly from All forms of racing !!!!!
my point is if you are going to take realistic
advantage of currrent technology
why stick to an archaic standard
Long surpassed.......safely
was set when almost ALL motorcycle engines were
Air Cooled.................synthetic in its infancy
metallurrgy riding the wave of cad cam
advances ..... Advances !..... ADVANCES !!!!
Nikasil cylinders & a dozen proprietary cousins
4.... 5 valves per cylinder......yamaha experimented with up to
nine(9)..... thats right 9 valves per cylinder
you mention cylinder rings
even n race four(4) strokes
3......then 2 & even down to one(1)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
ring per cylinder
the new frontier
direct injection........probably on a big cruiser [& i hope soon]
simply because theres more meat in the head
rooom for valves.....sparkplug & injector (altho im thinkin these 2 could be combined)
all to be placed in the optimum locations
with engines now running at 30-40 % inefficiency
(they used to run at a +50%)
great inroads can still be made in both areas
power & MPG
what we see in production will no doubt lag behind
cutting edge performance....... shame
yet we are seeing 6....7 speed & CVT transmissions in cars
i remember when a v8...4 barrel & a 4speed was the ticket
bikes used to lead car technology decades ago
simply NOT the case anymore
car guys used to wonder where & how so much HP
could be wrung from so little
well they got rid of their slide rules
started using computers
& they havnt looked back
4500ft/sec
passe
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Y2KZX12R
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posted November 16, 2006 06:13 PM
So, how high do you rev your zx12r?
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