Before people say use the search I just want to say I have and I just want 100% clarification. I am having a motor built for my s5 and my engine guy wants to use s4 rotors to take advantage of the lower compression for safety at high boost. He wants to use the s5 counter weights though with the s4 rotors. From everything I've read this should not be done but he said he does it all the time, even on his daily driver. Will this be a accident waiting to happen or will it not be a big deal cause he says as long as front and rear weights are both s5 its not an issue.

 

it may work but it causes an imbalance in the rotating weight so there will be noticable vibrations and the bearings will wear more rapidly. it is also a very bad idea with the heavy S4 rotors if you push the engine past 7k RPMs, as you probably will with excessive boost(or is it still a high compression 9.4:1 engine?).

if he doesn't understand how counterweights work he probably shouldn't be building engines, because he is a retard.

just because the conditions aren't as noticable doesn't mean it should be done. a light flywheel chops off way more than the balancers do anyways, so why the hell wouldn't he use the correct ones and simply reduce the weight there instead...


why do you think mazda made 6 different counterweight sets after each revision to the rotors? it wasn't for the fun of it. ever seen an e-shaft flex at the center? the result usually isn't what you want to see unless you like seeing rotor tips drag across irons and stuffed seals.

 

I was thinking it was a bad idea. And what the deal is he is building me a new block I have a act prolite flywheel with s5 counter weight for the build and he just started if I want to use the s5 weights I still can just as long as the weights match. I will just get the s4 its not worth the $100 risk on my side

 

Also I can just use the automatic s4 counterweight right???

 

all light flywheels use auto counterweights. so yes.

 

That's what I thought thanks for the info