so im in middle of rebuilding my motor and had a rotor that needed a new bering. so in the parkinglot at the machine shop i drop the ****** on the cement. killed it. man what a dork... anyway that is for a turbo motor but i was going to rebuild an na motor before i went the turbo route so i have these nice na rotors with nice berings all ready to go. what do i have to do to use them and how safe will my motor be with na rotors and boost vs the turbo rotors. i didnt plan on going past 10 psi on the turbo rotors so i can live with less on the na ones.

 

u will get people for and against it.. useless making this thread ull walk away even more confused than u are now. some are absolutly against it and will call you a dumbass (not in so many words) others are completly for it and will incourage you. i have n/a rotors but have no other mods for it to suport the diffrence. i really dont boost anyway all too much right now gas is expensize and i have no job lol

 

i say **** em its ur car if your not going to boost a whole i wouldnt worry about it hell im supercharging my car and will be boosting right around 10psi when im done and when the engine pops i might get turbo rotors not sure though

 

put the na rotors in. if your going to kep the stock psi of the turbo, youll have a faster car. it will spool he turbo faster and will make for better off turbo acceleration. but youll have to compensate for fuel. higher compression doesnt mean youll blow your engine, it just means you need to tune it a tad bit better.

 

Just curious. Which NA rotors do you have? The S5 ones have higher compression. I think they are 9.7 and the S4 ones are 9.0 Im not 100% on that but Ive heard of this being done. Tune correctly and you wont blow your motor.

 

i thought S4's were 9.4:1 ratio??

but as sircygnus said - if you do use the n/a rotors, you have to tune it better. also make sure that the rotors have the right counterweight and the weight code is correct

 

S4 Na: 9.4:1
S5 Na: 9.7:1

S4 T2: 8.5:1
S5 T2/fd: 9.0:1



If you have even a MILD doubt in your tuning/tuners ability, I wouldn't go with NA rotors. S5 T2/FD rotors are just THAT much safer, give you TONS of room to expand, and .4 compression isn't going to make or break your acceleration, but it may make or break your engine without a proper tune. It really isn't all that much..


Edit: And note, tuners like Steve Kan generally refuse to tune high compression turbo cars over somelike like 6-10psi :-D So..coming from a tuner, that should say something!

 

im not planning on anything above 8-10 psi. just stock for me. they are the same weight and i have the na counter balance. so i guess they will work. only one way to find out.

 

10 psi with high comp rotors is probably about 14 psi on a lower compression rotor (guesstimate) it takes less boost to make power with higher compression rotors, so you'll be sittin' pretty

 

Higher compression will give you better off boost performance, faster spoolup, and more power for a given amount of boost. It's also more prone to detonation, less tolerant of a shotty tune and you can't boost as high on a given grade of gas vs low compression. For that low boost I'd do it.

 

ok sweet. that sounds better than what i was planning anyway so damn the cement i say! 91 oct with premix is what im going to be using for fuel but i dont know about the tune. its all going to be ran from the stock ecu which i guess is just fine tuning the cas and tps and so on? ill take it to a shop to iron everything out when i get it back together. how exciting.