ok i have a streetported s4 tII, i want to throw my s5 n/a rotors in it in the begining the new year. im going to have 1600sec 720pri inj's, 3rd gen fuel pump, evoII front mount, t04b, and a lt-8. i was reading about beveled rotors.

do you guys think i should bevel them?

or keep them stock rotors because of the high compression?

looking for some opinions only, so please dont start flaming thanx

 

well its a bit off topic but id say go with a slightly larger turbo the TO4B is a bit small for any real fun.
as for the rotors untell i see a dyno im not doing anything.

 

putting in the higher compression rotors makes it more hazardous to run higher boost levels and get a higher "peak" hosrepower. it will have slightly quicker spool and more bottom end but at the sacrifice of top end.

if i were buuilding the engine for alot of power, i would probably use the stock rotors that are in there for most of a buffer against detonation.

as far as beveling, i may get disagreed upon about this but as stated it has been done ofr along time by race teams to get a little extra edge. I personally would do it, but i would also have the setup sent off to be dynamically balanced afterwords...

- chris

 

can you go into any more detail about losing peak horsepower. does that mean i loose top end but gain low end? wouldnt beveling the rotor make it less hazardous?

 

What are people thoughts on 90-92 HC lightweight rotors?

 

I dont know if I would bevel my own rotors, the possibility of them being out of balance is too great.

 

i dont think im asking the right question. would beveling my rotors bring the hazardous levels down while keeping high compression? or should i just keep it with just the s5 n/a rotors plain?

im looking on opinions about pros vs cons on beveling with the high comp. not just beveling them

 

beveling your rotors will not change the compression ratio of them

beveling is like porting - increases the duration that the port flows...either early or late

as far as them being off balance afterwards...if I can balance a lawn mower blade with a bench grinder and a screwdriver then a rotating assembly shouldn't be that hard.....what do you think they do with extremely modded boingers? lighten and balance the rotating assembly

Sureshot did his setup all by eye and hand and it runs


edit: I wouldn't use n/a rotors in a boosted motor - there IS a reason why mazda made N/A rotors (higher compression) and turbo rotors (lower compression)

running a high compression rotor and boosting ON TOP of the already high compression makes for easy detonation

 

I mean that you cannot run as high of boost pressure safely, therefore causing high end (top end) power loss on pump gas. the lower compression rotors are safer for higher boost levels and more power, not to mention that S4 rotors are stronger than S5 rotors if i remember right.

Beveling will do nothing to lower compression unless it goes extreme as CLR's rotors, then it may lower compression. Beveling is used for the extra little bit of flow you get when the side seal passes and the rotor is no longer in the way.

- chris

 

i didnt mean that it would lower comp. but drop in detination level because of more flow

and the s5 n/a rotors are lighter and higher comp thats why i was interested in them.

being properly tuned what would you guys suggest in highest boost i should be expecting with this set up?

 

Just go with 9.4's, they are everywhere and the gain from 9.4-9.7 isn't worth the risk.

 

the highest to EXPECT is whatever the turbo you are using is capable of...

the highest you could probably RUN - total guess - on pump gas and still be able to rev it right out would probably be 4-5psi

why not just put on a bigger turbo and add more fuel...or put in a hugely ported n/a if you want more rounded power...there are far more tested and proven methods of making power than mis-matching a bunch of internal components and trying to dremel your way out of the mess

 

i just dont want to boost the hell out of it. i want to get some good low-end torque as well.

4-5 psi tops is that with the stock ecu?

i would like to know how much boost i can run with my set up listed above (with a proper tune)

 

look man...we can talk about this until we are all blue in the face

bottom line is that you can't boost high compression rotors that much with out a major catastrophie.......I don't know how much you can boost them because no one I know of has really tried it, if you are dead set on finding out - BUILD IT AND TELL US

If you want good low end torque - go buy a mustang. It just doesn't happen in these cars...go to the timeslip/dyno form and look at the power curve on a +500hp rotary...there is JACK **** at the bottom end...

if you want a driveable car with a BIT of grunt on the low build a really high dollar really well ported/balanced/tuned N/A

 

I would beg to differ.

But the point remains that it seems like a big waste of time to pull apart a perfectly good engine just to install different rotors.

 

ahhhhhh yes - I completley forgot about your 6 port build Aaron

 

Or any really.

Saying a high compression can't boost as high is pretty useless. The simple fact is it doesn't need to, it can make just as much power running lower boost than a low compression running more, the only trade off exists when the heat rise from the engines compression ratio is less efficient than that of the turbo. (If you'll take a peak at most modern turbo charged cars, you'll notice the compression ratio keeps getting higher)