Pocketbike Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
79 Posts
Discussion Starter · #1 ·
What is the difference performance wise with water cooled engines vs air cooled engine,
Ex a 6.2hp polini 911
Be it a/c or w/c your still getting 6.2hp
Does the w/c rev higher ? Another example
A/c c1 does 35mph and w/c version is faster? Why?
 

·
Registered
Joined
·
610 Posts
Normally a watercooled engine can go a higher compression. You can also use higher porttimings when the cylinder is better cooled.
 

·
Super Moderator
Joined
·
3,391 Posts
Because you can run a lot tighter tolerances with liquid cooling...
 

·
Registered
Joined
·
610 Posts
No, has nothing to do with modification. It's the production tolerance are smaller. I can only compare the small two stroke engine that I know.
The squish Band on a AC engine is always bigger as on the same layout on a wc cylinder.
 

·
Registered
Joined
·
610 Posts
When you compare the same 50cc bzm engine one with ac and one with wc there will be about 3-4hp different. The wc engine can run 0,5mm squish we're for the ac cylinder I would recommend 0,9mm. Also the piston to barrel clearance is at the wc about 0,02-0,03mm and at a AC 0,03-0,05mm.
Also the with the better cooling of a wc cylinder you can run a much higher porttime and more blowoff area as on an ac engine.
AC cylinders runs also most a richer carb setting for better internal cooling.
 

·
Super Moderator
Joined
·
3,391 Posts
Yes you can run a mutch smaller ring gap when you know your engine won't go over 90c bearing clearance can be mutch tighter as well Les slop = more RPM and a much more refined engine.
 

·
Registered
Joined
·
79 Posts
Discussion Starter · #8 ·
When you compare the same 50cc bzm engine one with ac and one with wc there will be about 3-4hp different. The wc engine can run 0,5mm squish we're for the ac cylinder I would recommend 0,9mm. Also the piston to barrel clearance is at the wc about 0,02-0,03mm and at a AC 0,03-0,05mm.
Also the with the better cooling of a wc cylinder you can run a much higher porttime and more blowoff area as on an ac engine.
AC cylinders runs also most a richer carb setting for better internal cooling.
Okay so does this mean a if the a/c 911 6.2 is 6.2 hp than the w/c 911 6.2 would actually be more like 9-10 hp?
 

·
Registered
Joined
·
610 Posts
No but it has more potential to tune it.
The 6.2 engine is a restricted and calibrated engine. When you put on a bigger carb and a better exhaust you can get 8hp.
 

·
Registered
Joined
·
79 Posts
Discussion Starter · #10 ·
No but it has more potential to tune it.
The 6.2 engine is a restricted and calibrated engine. When you put on a bigger carb and a better exhaust you can get 8hp.
Okay im basically asking all this because i own a polini 4.2 and i want to make it have mad wheelie power and i want to get the most power i can out of it and for some reason i think the only way to do that is to make it water cooled… im still kinda confused tbh
 

·
Registered
Joined
·
79 Posts
Discussion Starter · #11 ·
AC cylinders runs also most a richer carb setting for better internal cooling.
And again the W/c always have bigger carbs and jetted higher than the a/c i wanted to get a nice 17mm polini carb for my 4.2 series 1 but i was told id never be able to start the bike
 

·
Registered
Joined
·
610 Posts
A bigger carb is only one step, you need also a bigger inlet.
There is no different between the ac and the wc 3 port Polini cylinder. You can put on your bottom end a 5 port cylinder that will make nearly the double power than the 3 port. There is also a upgrade for the 4.2 crankhous available to make the intake bigger. But it will be easyer and cheaper to buy a faster engine.
 

·
Registered
What's your poison? Mine is 40:1
Joined
·
1,182 Posts
The faster and more air/fuel you get in and out of the motor makes more power. Yes you can go too far but thats where the cylinder Chrisi mentioned comes in and will continue the process.
Find out from Chrisi how much a carb, intake, 5 port head is compared to the complete engine, and find your budget.
Sounds loke that bike will be fun.
 
1 - 13 of 13 Posts
Top