Thank you for the replies everyone! Speaking of CDI's, my Big Gun CDI that will be recieving will increase bottom to top end power also right? will it be quite noticable besides the increased rev limit? thanks again!![img]i/expressions/face-icon-small-smile.gif[/img][img]i/expressions/face-icon-small-wink.gif[/img]

 

A cylinder has to run at XXX temperature to get the most out of it. Wheather you get that temperature with a piston, or advanceing the timeing, or forceing more fuel and air into the motor. It does not matter, it just needs a certain amount of temp to be effecient.

With the less compression ratio of a piston, the more advance is needed in timeing to gain bottom end.
With Scooby, he is running A LOT of advance on the low range of RPM's, giving him more low end.

Then, with a TURBO added, the timeing will then be retarded at higher RPM's, so that the heat is not from advanceing the timeing, but from more fuel and air.

It is all a trick to keep the cylinder temp at optimum temp at any RPM. There are many ways to do that. Weather it is NOS, Turbo, OR high compression pistons.

Also, you have to figure out fuels and what temps they burn at...........

Everything is so easy[img]i/expressions/face-icon-small-happy.gif[/img]........

I was told by a wise man once "if it was easy, everyone would do it"

Outside temps, humidity, fuels, moisture, lean, rich, fuel type, timeing.........so many things to figure out

DuneDevil

 

Thanks DuneDevil you've almost cleared it up for me, just one more thing. If "xxx" is best combustion temp then what is an "8.xxx piston" ? Is it an 8:1 compression ratio piston running at optimal temp as I suppose from your excellent explanation?

 

Some crotch rockets run well over 12:1 on pump gas... But with different timing... Could that be done on a DS?

 

scoddee,

I knew from a while back that Scooby had put a low compression piston in his bike. And if memory is correct, it was around 8:1. He had some pistons made up special just for him.

So, to answer the question, yes, Scooby has dialed in his timeing and piston ratio real good to achieve the good low end.

DuneDevil

 

I was wondering the same thing because my cousin's yzf440 motor is running 12.5:1 and he can run REGULAR unleaded without a problem... Iasked how that is possible and he said because of timing..... SO, in a situation like this is ADVANCED timing helping this be possible?

 

There are more things to consider then just piston ratio and timeing. There is timeing on the cams and overlap on the cams.............

To keep it simple, The more compression you have, the less timeing you need to have optimum temps in the cylinder.

More Compression + Less timeing = pump gas.

More compression + More timeing = higher octane gas to keep from detonation

DuneDevil

 

Boy I have a lot to explain, but I don't feel like writing a book. So very short--- heat in the cyl. forget it. Very simple More Power always means more heat. If your over heating then worry about it. A piston only will increase power & torque though the rev range [minimaly] . Most power from any 4-stroke engine comes from the cyl. head. Breathing is what it is all about. Any improvement on the intake also needs improvement on the exhaust. And there is a little more to a cam than just lift--duration-over lap-ramp angle etc. . The biggest power gain from the eng. block would be if you put in longer rods [expensive procedure $$]. and to stroke it [crank].

 

Thanks guys for the interesting info!! I did forget to say before but when I do put the RWR 11.5:1 piston in I will have the head ported. I just wanted to know what the piston itself would do for power gains. I will have the head ported at the same time I do the piston but I will wait to do the cams after that but that will help quite a bit too..... Little at a time[img]i/expressions/face-icon-small-smile.gif[/img]

 

Pushing-- don't forget the exaust, what goes in must come out. And don't forget to rejet.