supra5677
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posted April 03, 2006 08:07 AM
at what point does the stroke limit potential horsepower?
Iv'e been crunching some bore and stroke numbers for my 2007 project. I cam up with 86 by 57.4, (2mm stroke and 3 mm bore) it came to 1334 cc. I don't want to go too big on the stroke because I want to take advantate of the engines high rpm capability with my extended ecu. I was going to run the intake cam on the exhaust side also. The ZX11 was unique in that it had a 58mm stroke but the red line was still 11,500 rpm.s My buddies ZX11 with just a muzzy and jet kit made peak power right at the rev limiter and there was more in it.
I thought I read somwhere that the ZX11 had .362 cams on the intake and exhaust side. Is this correct. If it is these cams are both more aggressive than the 12r. Anybody have any ideas? Y2K? Doug? Entropy? or anybody?
supra
   
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Y2KZX12R
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posted April 03, 2006 09:29 AM
 Edited By: Y2KZX12R on 3 Apr 2006 10:52
Why not just go with the 86mm bore and 60mm stroke? The stroke isnt going to limit HP. The head and cams will limit the power.
HP is a function of how much air and fuel are burned in a given amount of time. The 12r makes more HP than a Busa because it revs higher. Not because the stroke is shorter.
If you rev the 86x60 to the rpm that is equal in displacement over the same amount of time as the 86x57.4 the power should be similar becuase both engines displaced the same total volume in the given amount otf time. So RPM is a way of increasing engine displacement over time. Thats how the 1199cc 12r makes more power than the 1299cc busa.
Typically revving an engine to increase its displacement over time is more expensive than increasing the static displacement becuase you need expensive valvetrain components. Also the higher reving engine wears out faster because it uses up its total alotted cycles faster.
The bottom line, "theres no replacement for displacement". Pick an rpm that you want to rev the engine to and then that will tell you the nedded components.
Basically the 12r needs to rev 834 rpm higher to equal the busa displacement.
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Y2KZX12R
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posted April 03, 2006 10:08 AM
Edited By: Y2KZX12R on 3 Apr 2006 11:10
This may make it easyier to see...
1375cc @ 10,000 rpm = 419,375 cc of displacement per min.
1334cc @ 10,307 rpm = 419,375 cc of displacement per min.
1299cc @ 10,585 rpm = 419,375 cc of displacement per min.
1199cc @ 11,467 rpm = 419,375 cc of displacement per min.
So if all other things were equal then this is the rpms you would need to rev to make the same power as the 1375cc engine.
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supra5677
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posted April 03, 2006 11:16 AM
I thought a short stroke allowed you to rev the motor higher. I thought that was the whole point. A busa doesn't do anything as far horsepower past 9,800rpm's I thought this was because its larger 63mm stroke doesn't allow it to. The 12R does have superior cams, compression, and rpm compared to a busa. The 12r proved you can give up 100cc of displacement and still make more power.
To me " there is no substitute for displacement" is only true up to a certain distance.
Your above chart I think is:
1375 85.5 by 60 muzzy
1334 is 86 by 57.4 myself
1299 must be the weak busa 81 by 63
1199 is the 12r 83 by 55.4 stock 12r
Id'e agree with you if you could answer this.. How can you get the 1375 to make peak power at 11,625 instead of 10,000 without blowing up? To me a 1334 can overcome the 1375 because it can safely rev higher.. Please tell me what else I am missing.
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swft
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posted April 03, 2006 11:48 AM
Need Doug to comment on 'piston speed'
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supra5677
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posted April 03, 2006 12:15 PM
"rpm is a way of increasing engine displacement over time"
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TRNorBRN6001
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posted April 03, 2006 12:18 PM
Always depends on what your going to use it for? And how deep
your pockets are?
There are quite a few big bores running extended ecu's and peak or
flatten at limiter. The breathing characteristics you build into the bike
will also move the HP to the right or left (cams, porting, height of velocity
stack, ect.) There are also quite a number of big cc bikes that rev to 15,000
especially with Power Commanders relatively new rev extenders.
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TRNorBRN6001
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posted April 03, 2006 12:48 PM
If it's for the street I think a 1290 drop in would work just as well
as a 1334. There is at least a $750-$800 expense for just
getting the crank stroked.
If it's for the track then ya better have deep pockets
cause it'll need to get freshened up offten.
Mr. Turbo has a nice kit that'll run ya around the same as
a stroker and probably give you a little more on the top end.
Or ya might just be a canidate for one of them ZX-14s
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Y2KZX12R
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posted April 04, 2006 04:06 AM
Edited By: Y2KZX12R on 4 Apr 2006 05:07
quote:
I thought a short stroke allowed you to rev the motor higher.
Yes. Shorter stroke engines can rev higher and keep the mean piston speeds at a lower rate. Mean piston speed is what really limits the sealing ability of the rings. If you run ported pistons and shorten the flow path to the back of the ring you can go higher on the mean piston speeds.
quote:
The 12R does have superior cams, compression, and rpm compared to a busa.
Define superior. If superior is more midrange, then no they arnt. If superior is more topend power then yes. The cams have more lift and duration than a set of busa cams becuase kawi wanted the engine to make more power up top and less in the midrange. You have to make a choice. The static compression is higher because the cams are bigger. The intake valves close later yielding less dynamic compression. So by raising the static compression it brings the dynamic compression back up to the desired number.
quote:
How can you get the 1375 to make peak power at 11,625 instead of 10,000 without blowing up? To me a 1334 can overcome the 1375 because it can safely rev higher.. Please tell me what else I am missing.
You need to use cams that will make peak power at 11,625 RPM. This will make the engine run weaker in the midrange. "blowing up"? Thats a matter of using strong enough parts to handle the task at hand. $$$
I dont see why there would be a durability issue to rev a 1375 to 11,625 rpm. With stock cams it would be pointless becuase the factory cams would peak out at aprox. 10,400 down from aprox. 10,600 on the 1199cc stock engine.
Yes the 1334cc with stock cams, would make its peak power higher than the 1375 with stock cams. Not because of stroke but becasue of the overall displacement difference.
The larger the displacement of the engine the smaller it thinks the cams are. This lowers the peak at which the peak power is at reguardless of the bore stroke combination.
Theres also things like swept volume increas rate etc. but we are generalizing here so...
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ninja12
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posted April 04, 2006 07:04 AM
quote:
I dont see why there would be a durability issue to rev a 1375 to 11,625 rpm. With stock cams it would be pointless becuase the factory cams would peak out at aprox. 10,400 down from aprox. 10,600 on the 1199cc stock engine.
What rpm would you shift for drag racing? stock and 1375.
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supra5677
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posted April 04, 2006 08:45 AM
Ok Jim I follow you to a point.. As far as where the stock cams make peak power that primarily depends on ignition and cam timing. I think Doug M with his 1270 with 5 degrees of advance, and more advanced cam timing got 192horsepower at 10,400 rpm. When he changed his cam timing to 105/100 and 2.5 degrees of advance he made 202 horsepower std at 11,400 rpm. My stock displacement 12r peaked out at 10,900 rpm and this is before I changed my cam timing to 105/103 so it peaks out even higher now. 105/103 seems slightly peakier than 105/100. Stock cams can peak out past 10,600 rpms.
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Y2KZX12R
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posted April 04, 2006 10:33 AM
I think the drag guys will best know what recovery rpm is best for thier setups. I havent raced the 12r at the track so....
supra, cam timing will move the peaks around. But in the above statements I was assuming the cam timing was the same in both engines.
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supra5677
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posted April 04, 2006 11:14 AM
agreed....
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