Im still tring to complete my rebuild. turns out when my rear plate cracked it also overheated the rotor. now my apex seals don't fit in the slots freely. therefore what would be the best rotors to put back in the engine. heres the build.
-Full Bridgeport
-planning on running big turbo (hx50, gt40-42, hx52)
-haltech
-s5 housing
-s5 rear plate
-atkins rebuild kit (RA seals)
so what would be the best used rotors to go with. S4, S5, FD, NAs or T2

 

i am assuming since you made no mention of the front half of the engine, then it was salvaged. if that's the case, then why wouldn't you just get one to match whatever rotor you have?

 

Idk exactly what the front rotor is . The guy I bought the car from built it. Bc and so far hes been sketchy. So I have been restoring car. If theres a way to tell what rotors I have . That would be awesome.. he said supposely tgey are tII s5 rotors but idk.

 

Personally I'd use s4.

S4 rotor dish is cast and thus has a rough surface,
S5 rotor dish is machined and is smooth with very small machine lines running parallely to the side-seal edge

 

These are the s4 rotors that were used in my build.

 

Cool mine are not machined.. they are rough.. so that makes sense consodering my car is a s4. Why would you go with s4 t2 rotors. Anything special. Im tring to make over 500hp.

 

They're stronger, and since they're heavier its better for your bearings, and being lower compression its easier to run high amounts of boost.

S4 rotors are more durable due to the additional material that wasn't shaved off. S5 rotors are better for engine response.

Which means less chance for the rotor to get dented during detonation, on the other hand you need to run more boost to get power since they're lower compression and the more boost you run the higher the chances are for detonation.

 

lower compression, is better with a turbo

 

Lately ive been seeing fds running na s5 rotors.. supposed to make better power down low but not good for higher roms.

 

Really?

 

More weight smooths out the rotation.

 

I hear s4 na rotors (9.4:1) and E85 are the way to go. You can make great power at moderate boost levels. I run s4 na rotors in my turbo motor at 8-9 psi and i love it. I dont use E85 but plan to in the future for more reliability and power.

 

Does anyone know how to tell the difference in a na and turbo s4 rotor?

 

Turbo rotors will have a gash engraved into one of the combustion areas. It looks like a "I". You will have to clean it up alittle too see it.

 

turbo rotor has a deeper dish, which is easy if you have em side by side but hard if you don't. i think there is a T or an N, in the oil drain sort of by the bearing

 

when there is an offset, like on a crank shaft, less weight is better.

 

It appears nobody has mentioned the weight codes yet. The rotors will have a, b, c, d, of e stamped on the side of them. A is the heaviest, e is the lightest. It is best to have matching weights, but you can be one off and be ok.

Make sure to take this into account when buying your replacement rotor.

 

Better for the bearings or in general?

As for the weight codes I always thought a was lightest and e heaviest, guess I had that backwards.

 

I used an entire matched Fd rotating assembly , cant say i have heard that much praise for s4 rotors before like i have in this thread

 

Well the easiest cheaoest way was to just replace the one rotor vs a entire rotating assembly. So I just found one. Should be here next week..

 

Does the weight match your other one?
Factor in a "big" turbo and its the details that count to make reliable power

 

It doesn't have to be the same weight it can be one letter off up or down but I wouldn't go any more than that.

Example - rotor 1 letter D. Rotor 2 can use C,D, or E

The weight difference between each letter is roughly half a pound per letter up is less , per letter down is more.

 

I got the same weight rotor.. and yes I want to run crazy boost.. so I guess the lower compression and a full bridgy + big turbo.. should make nice numbers

 

Half a pound?

 

Each letter higher is half a pound less, each letter lower is half a pound heavier.

Example - the difference between rotor letter a and c is one pound , the letter a being heavier.

The difference between a and e is roughly 2 pounds a being heavier, e being lighter