piston weight vs rpms

[Rick Pirrone]

Just asking another question

Does a pistons weight have an effect on the rpms of the engine????

eg heaver piston =lower revs and lighter=higher revs

I have heard buy skirting the piston you will gain 500 rpms

Look forward to hearing from all

cheers rick

 

[Chris Wood]

removing more piston in theory will make more rpm.. again theory.. there are so many factors that play into this.. i feel more important than piston weight is crank weight.. but that is me.

plus one that back end of the boat blows out of the water then all this goes by the way side.

but yes i am sure it makes a difference.. but i think more so in the PACKAGE you have in the motor.

 

[steve wood]

for the most part,todays pistons are about as light as you can go without winding up with a grenade.on some engines you can skirt the piston a little more,some not.there are many more things to do to an engine,boat,setup,props,props,props,pipe, than fooling with pistons

 

[Adam Piotrowski]

On many Nitro engines you also need to be careful when Skirting the piston. Some engines have the bottom edge of the piston and Exhaust Port extremely Close @TDC. If you cut the skirt your opening the Crankcase up to the Exhaust Port at TDC creating a Big Problem.

 

[steve wood]

don't know of anyone that skirts the exhaust side of the piston

 

[Rick Pirrone]

Just asking another question

Does a pistons weight have an effect on the rpms of the engine????

eg heaver piston =lower revs and lighter=higher revs

I have heard buy skirting the piston you will gain 500 rpms

Look forward to hearing from all

cheers rick

removing more piston in theory will make more rpm.. again theory.. there are so many factors that play into this.. i feel more important than piston weight is crank weight.. but that is me.

plus one that back end of the boat blows out of the water then all this goes by the way side.

but yes i am sure it makes a difference.. but i think more so in the PACKAGE you have in the motor.

for the most part,todays pistons are about as light as you can go without winding up with a grenade.on some engines you can skirt the piston a little more,some not.there are many more things to do to an engine,boat,setup,props,props,props,pipe, than fooling with pistons

the reason i ask is

i have a vac 45 in a rigger with home made piston in it made by a local engineer

i run my pipe @9.75 and are getting speeds of 69 mph

the engine doesnt seem to be hard reving like some of the others i hear

so i shortned the pipe to 9.25 and used slighty smaller prop thinking ill get more revs but not the case

if this piston was a bit heaiver then the stock cmb one would this have an effect on the rpms

thanks guys

cheers rick

 

[steve wood]

i think i would have to be really heavy to slow it down 20 to 30 mph

 

[Rick Pirrone]

i think i would have to be really heavy to slow it down 20 to 30 mph

Re check your timings the piston might have changed the Timings

If you want i can do it for you

im thinking i might check the weight of the piston to the cmb stock one

i did check the stock one the other night for memory it was 0.2 oz (could be wrong )ill have to double check

greg i might ask you to do that for me just to make sure they are ok not sure if they were checked when it was made

also not sure if aaron did this when he checked the button

thanks guys

cheers rick

 

[dwilfong]

I have custom billet pistons in my 1.01 and thy are heaver than the stock ones. The Eng will still rev the same.

like Greg stated if the compression distance is different it will change the timings.

I had mine made .020 taller so I could adjust the timing by cutting the top of the piston and not have to change the ex or intake ports by cutting or jacking the sleeve around.

David