Thread: 92 mm crank in stock bore?

1. how much more? quantify this statement with scientific evidence plz. at least a formula you used to come up with that statement
2. shouldn't (have to)? i can agree with that.
3. NOT TRUE. even if you stick with the oem rods, the aftermarket pistons that are needed are lighter than oem. on top of that, most ppl would use aftermarket rods anyway, and they are also lighter than the oem rods.

Hes quite correct in everything he says.

Apply simple physics such as force = mass times acceleration.

1. Mean piston speed will be higher at the same rpm in 92 mm stroke. The higher piston speed (M=mv) - the more load (impulse) to the rods and bearings. To hold such load you need better (thiner) rods. The thiner means heavier. The more stroke is the the less R/S -> the more load to the cylinder walls.

So you see. My english is bad, but we are better in phisics and math.

all else being equal your statements are correct.
mean piston speed higher? yes.
more load? yes.
BUT, like i said earlier,
we use LIGHTWEIGHT aftermarket parts to REDUCE the reciprocating MASS which, in turn, REDUCES the kinetic LOADS to an acceptable level.
Kinetic= KE= 1/2 MV^2 m= mass, v= velocity
reducing either m or v reduces kinetic energy. obviously we reduce m
i'm more concerned with piston ring longevity.

physics, math? how about (un) common sense

hey now lets tone down the smart guy talk so i can understand.. hehehe

you're partially right

Kinetic= KE= 1/2 MV^2 m= mass, v= velocity
let KE20=1/2 MV^2 will be the stock kinetic energy
m1- mass of aftermarket forged piston. M - stock mass. let it be 0.9 of the M. So we substitute m1=M*0.8
v92 - 92mm crank piston "velocity"
v92^2=1.14 v^2

KE(92) = 1/2 M1V92^2 = 1.14*0.9 * (1/2 v^2 * M) = 1.026 KE20

I conclude : Yes. You will have the equal load on the 2.4 forged and 2.0 stock engine. But as we know, the stock engine safely rews to 8k. But we cant but mention the alternating load. Due to it - we have to use stronger rods as we increse the torque, because the kinetic energy is not the only force, that it suffers.
I don't try to say that 9k is impossible on the 92mm crank. I only try to say that it is not a budget. The bearings and the crank will damage faster. it will require thinner oil, oil cooler, good oil pressure, extra oil clearance in the bearings.

Peace!

i didn't mean to assert that 9k was safe daily limit. nowhere did i state that. but 8k should be a safe limit on the hypothetical 92mm stroker with the lightened aftermarket parts (rods/pistons). indeed, (for my build at least) max power will be targeted closer to 7.5k with the proper i/m, cams and header.
over the next few months we'll see how it all turns out

Crank now for sale here:
http://www.sr20-forum.com/naturally-aspirated/37843-mazworx-sr-92mm-knife-edged-stroker-crank.html