piston weight

[Diodedog]

It will have no noticeable effect on balance or power.

[Mark O'Neal]

Go over to, "Yellowbullet", and ask Mark O'Neal, the guy with the fat orange and white cat as his avatar.

Mark should/will know!

He owned Probe Pistons.

pdq67

My cat

is not fat


Burma Shave

[Mark O'Neal]

messed this up

[Mark O'Neal]

Furthermore he is my Quality Control engineer.

In this photo, he is doing a Cat Scan.....

[Mark O'Neal]

this too

[Mark O'Neal]

to be followed by a "lab report"...as soon as the neighbors dog gets here.

[engineguyBill]

I think the OP was asking how much centrifical force will add to the theoretical weight of the piston at TDC . . . . . . But I could be wrong, we will wait for Mark's cat scan for final answer.

[GRTfast]

FWIW, the most power our shifterkart engines ever made was with the heaviest pistons. The extra meat in the head of the piston allowed us to run a more radical ignition curve and combustion chamber shape without detonation. The lesson we learned was that piston mass isn’t the only consideration when choosing a piston to make the most power. Not sure how applicable this is to large 4 stroke engines, but physics is physics.

[MadBill]

Go over to, "Yellowbullet", and ask Mark O'Neal, the guy with the fat orange and white cat as his avatar.

Mark should/will know!

He owned Probe Pistons.

pdq67

My cat

is not fat


Burma Shave

So, not excessively mouse-powered?

[pdq67]

Mark,

I am trying to PM you so please check your inbox.

Thanks,

pdq67

[RDY4WAR]

FWIW, the most power our shifterkart engines ever made was with the heaviest pistons. The extra meat in the head of the piston allowed us to run a more radical ignition curve and combustion chamber shape without detonation. The lesson we learned was that piston mass isn’t the only consideration when choosing a piston to make the most power. Not sure how applicable this is to large 4 stroke engines, but physics is physics.

This reminds me of the old 347 vs 351w SBF debate.

It also makes me wonder how this applies from a fuel economy perspective. Say if you're building an engine for a strictly street car or tow rig and want to get the best mpg out of it. Would a 100 gram, or even 200 gram, difference in piston weight make any difference on an engine built to cruise down the highway at 2500 rpm?

[4vpc]

how much is 14 grams worth in a 7000 rpm motor new piston weight a little more thanks

$15 at today's rates.

[steve316]

Piston weight in a street build is not as important as in a race only build. A 4" stroke engine hits over 10,000 fpm by 73 degree ATC @ 8900 rpm. Doesn't everyone try run the lightest piston without sacrificing the integrity of it; I know I do.

[piston guy]

As mentioned by several , "weight" alone has NO affect on HP unless it is missing from an area that could allow distortion enough to hurt ring seal or cracking. Removing 14 grams directly under the wrist pin or out of ONE valve pocket are a couple of obvious examples that would lead to failure in most cases. When I did Nascar stuff ( before the engine parts weight rules) the engine builders were obsessed with weight reduction. When the new minimum weight rules came down , The heavier pistons actually made MORE power with strategically added weight to reduce flex. Same for light weight pins. Pin flex absorbs power and causes pistons to crack.
I'm not Mark but I do have a similar model cat scanner at home.

INERTIA is a totally different matter . Heavier piston and pin weights will make engine bearings "unhappy" MUCH more quickly at elevated RPM. Inertia weight changes radically every 1,000 that the RPM is increased. The longer the stroke , the bigger the problem. Rod length is also a contributor.

[Stan Weiss]

Bore_=_4.6___Stroke_=_4.75___Rod_Length_=_6.7___RPM_=_8500
Piston_Weight_=_555.0___Rod_Weight_=_650.0
Small_End_Rod_Weight_=_216.6666___Big_End_Rod_Weight_=_433.3333
Rod_CG_/_Distance_from_Small_End_=_4.466667______GAS_PRESSURE_=_0
Crankpin_/_Rod_Big_End_Acceleration_=_156811.3
Crankpin_/_Rod_Big_End_Rotational_Force_=_4656.161

____________Reciprocating____Total_____Piston_Side___Piston
Crank_Angle____Force_________Force________Force__Inertia_Force
__Degree_______Pounds________Pounds_______Pounds______Pounds
___.000_____11230.718_____15886.880_________.000____8077.385

======================

Bore_=_4.6___Stroke_=_4.75___Rod_Length_=_6.7___RPM_=_8500
Piston_Weight_=_541.0___Rod_Weight_=_650.0
Small_End_Rod_Weight_=_216.6666___Big_End_Rod_Weight_=_433.3333
Rod_CG_/_Distance_from_Small_End_=_4.466667______GAS_PRESSURE_=_0
Crankpin_/_Rod_Big_End_Acceleration_=_156811.3
Crankpin_/_Rod_Big_End_Rotational_Force_=_4656.161

____________Reciprocating____Total_____Piston_Side___Piston
Crank_Angle____Force_________Force________Force__Inertia_Force
__Degree_______Pounds________Pounds_______Pounds______Pounds
___.000_____11026.964_____15683.126_________.000____7873.631

Stan