Well my rotors will be here in a bit.

I'm gonna swap out my stock 9.0:1 for the NA S5.

I'll be boosting stock 10psi with everythign stock except

ic/dp/mp/cb/intake/(stock but highly polished ports) and some other bs

main reason is i'm non-seq and want faster spool/ better throttle response (off boost)/gas milage/ and the bump in hp doesn't hurt.

I'm running a blitz smic and will be running 89 octane.

I'll use RA seals

If I ping so be it, but just wonder on others experience with high comp rotors in turbo applications.


btw i have a set of good FD rotors for sale

 

Well wouldnt 93 octane help instead of 89?!

 

I'm not worried about pinging....... yeah 93 would help but that's not practical. Most of the time that's not a choice in Iowa. Some stations have it, others don't.

I just wanted to see what other though of the high comp rotors when they ran them. Wonder how many actually have

 

If people still get knock with 93 octane and 10psi stock boost then 89 octane and high compression is not going to help the situation at all. Maybe go to a sunco or something to buy some high octane by the barrel or something and mix it with your gas. Dont know what to say.

 

Good for you. I come from a bit of a Honda background and I helped a friend of mine build a 2.2liter Honda motor for Turbo. We were actually running 11.2:1 compression in it, hopes of making 300+HP and have a broad usable powerband. The results are still being ironed out, the engine hasn't even been run beyond the turboless break in because we can't find a tuner in WA that we trust.

Anyway I'm ranting. Point is I've got this dream of building an FD with S5 NA rotors(possibly S4 I'm still a little new) making something in the high 300 low 400 range at the wheels, and having an extremely broad, usable powerband. The quicker spool that higher comp. ratios allows would theoretically do that. So I'll be really interested to hear how it goes for you.

 

I dont' see how a normal running FD can get knock with 93 on stock boost.

if so- i'll just play with fire then.

i'm always look'n for an excuse to rebuild

if ppl are so worried about knock why don't they use the 8.5 CR?. Sure you have to swap over more parts but some ppl would like that safety and FC parts are cheap.

lower performance higher saftey.

I'm going higher performance lower saftey. Just like turning up the boost.

effective compression is different and i do under stand that and how to calc it.

If my FD works out i'm changing my S4 8.5's out too.

ppl have been boosting on 9.7:1. I'm not a pioneer i'm just wonder'n waht ppl experience in a FD not a FC.

 

Im not knocking you at all, the idea sounds great. And good for 10psi. I hope you the best, and get back with any info you get. It is good to have the responsiveness when your off the boost.

 

yeah my low comp street ported TII is a painful off boost and is a big reason for this.

so as a daily driver my FD will have to please me and alot of the driving is off boost. It will even have A/C!

 

Cool , hey thought about maybe lightweigth drive train before going to that extreme? Like flywheel, driveshaft, maybe lighten the rotors? Or maybe you want to do all these things along with your idea =P

 

i've though about the flywheel/rotors

lighten'n the rotor's isnt' cheap and must be balance again with the counters. The only rotor modification i'll will be doing is polishing them.

as for the flywheel i wanted to keep the inertia. I don't want to give up low end torque for response, but have been debating. The money thing pretty much killed it though.

 

Come on, it's not that hard to find 91+ octane in IA. What kind of backwoods area are you living in?

FWIW, I ran 89 octane on my old engine @12psi with no detonation problems....of course it wasalso only running about 70psi of compression.

 

I think its 1000$ to shave 1 pound off the rotors. Those f*ckers are so dam heavy. Racing Beat does it I think. The fly wheel is nice though, its cool to tap the throttle and see the revs jump.

 

monticello-

pop 3,000

 

Why not try RX-8 rotors? 10:1 CR and lighter weight...

 

using the rx-8 is ugly-

it's due to the seals/weights. Takes alot of money to get them to work. Paul Yaw did them i think.

only getting .3 CR for thousands of dollars is not very cost effective in my book. The s5 NA are drop in replacement.

 

ok well i guess i'll ask another question.......

the FD have "race bearings"

these basically have larger clearance for more oil. Don't know the specs off the top of my head but more than the FC.

would the smaller clearances with higher oil pressure cause insufficient oil flow?

I have new bearing for FC's but no extra FD's.

i do not for see a problem running less clearance but look'n for a some input.

 

Going from 9.0:1 to 9.7:1 will probably net you about a 2-3% gain in horsepower off boost. On the other hand, it will reduce the amount of boost you can safely run, especially on lower octane fuel. But hell, if you like rebuilding engines, knock yourself out.

 

 

well i'm gonna get flamed on this one but........

i know there are many variables and this isn't 100 percent accurate.........

((boost psi / 14.7) + 1) x motor compression = effective compression

i ran it with 10 psi at 9.7 and got 16.298

then with 12 psi on stock 9.0 and got 16.347

yeah 89 is low but ideally i'll go for 91 when i can (which is most of the time)

If i keep intake temps down and feed it enough fuel i don't see a huge problem.

I'm just look'n for feed back. It's not too late -i can turn back You might be right jim but i won't know until i blow one. If i do it's back to 9.0. Right now i'm willing to run that risk.

 

With the right fuel and tune you can run 9.7, people that say you can't don't no or haven't tried, two people on this forum doing it succesfully are crispeed and Xcessive. Both run high boost, when I tear down my motor this winter I will be doing the same. You will need high octane and a good tune by someone who has tuned with high comp rotors.

 

There was someone running AFRs in the 10s and still getting detonation, with 89 octane.

 

stock ecu with higher compression rotors, a free flowing exhaust, upgraded intercooler and low octane will be a bad mixture.

the ve of the engine is gonna be way up so your gonna be leaning out. I dont think you quite understand the importance of octane and how much of a difference it makes. Hell i would be cautious to run 94 octane on the setup your talking about, or do you have the magic buttplugs?

Why waste money rebuilding engines? buy an ecu and use high octane and you will be gravy IMO

 

We're not saying can't. We're saying shouldn't. There's a difference.

But really, what's the point? Picking up a few horsepower off boost? Sure you can tune and run high boost with high octane fuel, but why? You could run higher boost levels without having to resort to race fuel if you left the damn thing alone.

 

I'm with Jim and Jeff on this one. These motors are very susceptible to the "**** happens" motif even when set up properly and conservatively. You're asking for trouble running anything less than 93 octane in my opinion......

 

yeah my low comp street ported TII is a painful off boost and is a big reason for this.

Why do you have "off boost" condition? What is your set-up? Turbo big enough for over 400RWHP? My ported low comp TII starts to boost ~1,500rpm and should be good for over 350RWHP- obviously the engine compression is just one small part of boost response that can be worked around easily.

With the right fuel and tune you can run 9.7, people that say you can't don't no or haven't tried, two people on this forum doing it succesfully are crispeed and Xcessive.

Chrispeed runs Methanol and Xsessive runs race gas, ceramic seals and is a VERY good tuner. Both have bumped the compression up since their turbos just run out of flow at the 30-40psi boost they are running.

Very different from a guy having his car tuned by "some one" in Iowa and running 89 octane and having his exhaust heat trapped in the motor by the terrible stock twins- though I admit, 10psi boost is very low boost.

I am sure 9.7 can be done on a street turbo and will run VERY well- right up to when it doesn't run anymore.

I know, you should ask Ralph (Xsessive) if he thinks it is a good set-up for your goals (~300RWHP driver on 89 oct, etc)

His shop and # are in his sig
Ground Zero Motorsports
Portland OR 503-256-3278
FD3S 32psi 700hp
94 Supra 1170 RWHP