13.3:1 Compression on a stock gasoline engine?

McRat

McRat

Diesel Hotrodder
Aug 2, 2006
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So is the claim by Kawasaki for their ZX-6R 600cc sportbike.

I wonder where the breakthru came? I was stunned when they hit 10:1 on pump gas. Shocked at 11:1. Dumbfounded at 12:1. Over 13???
 
02freighttrain

02freighttrain

Team Salad Bartender
Aug 13, 2006
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sootville, Fl
Must be carefully applied ingnition timing, with all kinds of knock sensors.

Makes no sense, how they could pull this off with pump gas, especially at high rpm's.?
I see some very cold range plugs and pistons with some special metalurgy on the top, before the first ring land........ Fuel injection does offer some relief to pre-ignition, but damn.............
 
whitetrash21

whitetrash21

put on da damn helmet day
Apr 29, 2008
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i had 13.7 on a 427ci in my car...... had to run 112 or 114 in it ALL the time or the knock was horrible. how they're doin 13.3 on a pump gas is beyond me... i'd like to see that.....
 
M

Mike

hmmm....
Feb 17, 2007
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San Angelo, TX
Ya works great now that direct injected gassers are out. Man O Man that compression ratio may just only be the start of higher ratios to come.
 
Stingpuller

Stingpuller

The Pusher Man
Jan 11, 2007
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With a very GOOD combustion chamber 4 valve head direct injection and the right camshaft profile. At higher RPM you need more compression because you have trouble filling the cyl. Thats why nascar drop compression, at wide open they were fine but on pit stops(any time they had to go from low rpm to high) they would hurt a piston. Thats still hard to believe they are up that high now. Jeff
 
Lonnie

Lonnie

Horsepower Addict
Oct 18, 2007
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The small piston diameter reduces the required time for the flame front to travel across the chamber & therefore less time to cause detonation. This combined with very high rpm & you can run some incredible compresion numbers. My R1 Yamaha only needs 89 octane with 11.8:1 & actually runs better on 89 octane than higher octane fuels. Mine also has 5 valves per cylinder, which I thought was pretty cool.
 
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Stingpuller

Stingpuller

The Pusher Man
Jan 11, 2007
2,019
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central Ohio
Yep, a lot of people forget about the smal bore. On a pump gass race motor you want a small bore, short rod and a good head(chamber).
 
coldLBZ

coldLBZ

New member
Apr 22, 2007
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I was looking through an old Hot Rod magazine Sept. 2005. The fastest car at the Pump Gas Drags ran 8.72 @ 154.19 mph. It was in a 34 Ford coupe with a 500 ci BBC running 93 octane. I thought that was pretty cool.
 
SBCNX20

SBCNX20

Junior Member
Aug 7, 2006
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Lonnie said:
The small piston diameter reduces the required time for the flame front to travel across the chamber & therefore less time to cause detonation. This combined with very high rpm & you can run some incredible compresion numbers. My R1 Yamaha only needs 89 octane with 11.8:1 & actually runs better on 89 octane than higher octane fuels. Mine also has 5 valves per cylinder, which I thought was pretty cool.
Click to expand...

Yep it's all about the perfect combustion chamber and small bore.
 
Trippin

Trippin

SoCal Diesel
Aug 10, 2006
663
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Atomization is much improved with direct injection and high injection pressures. Thus creating a more homogenous mixture.

Alot of the same theory that helped the Duramax become a clean burning power monster. :D
 
R

ROGUE GTS

Member
Apr 30, 2008
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Bikes act A LOT differently than cars do as well. The high rpm combined with relatively light load and a killer breathing cylinder head does wonders.

I've been running a 13.5:1 JE piston that is 97mm dia in my single cylinder dirtbike for years on pump fuel with no issues what so ever, with the rev limiter set at 12k rpm. Those DOHC and 5 valve heads get it done, along with being all aluminum and cooling very very well.

It's pretty much mandatory by the AMA to run unleaded pump fuel, no rocket fuel allowed, so we make it work, putting down over 50hp to the wheel on that bike. Doesn't sound like much, but on a dirtbike it hauls the mail.
 
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