This isn't a n00b "I wanna rev to 10,000 rpm" thread. I just want to figure out where to put my rev limiter for my new setup based on the limitations of the s4 rotors and rotating assembly. The power fell off around 7200rpm on my previous setup with a T04S (60-1) turbo, .96 A/R undivided hotside on HKS log manifold. I had my rev limiter set to 8300 and would usually shift around 8000, at least in 1st and 2nd because they went by so fast.

My new setup has the same turbo but with a 1.00 A/R divided hotside and a stainless divided manifold. Ports are a large streetport on the intake, and I just got the stage 3/EP3 porting template for my exhaust ports from Pineapple Racing, which is the largest template they sell for non-bridge engines. I'm hoping my car will keep increasing power up through maybe 7500-7800 rpm... the compressor wheel and housing should be efficient enough and I've never had boost fall off even at 21psi with race fuel. Would it be safe for a stock s4 rotating assembly to set the rev limiter to 8700 and shift around 8500? It would help when I do go to the race course (Virginia International Raceway isn't too far from me). When I talked to the guy at Pineapple Racing he said he has customers using s4 rotors in FD engines and they rev to 8500.

 

When I was using S4 rotors I tried 8,000 and 8,500rpm on different motors. No engine failures from over revving.

Did 9,000rpm limit with the S5 rotors without incident.

Auto-X, hillclimb and daily driving.

Did see around 10,000rpm once due to a redline 2nd back to 1st miss shift w/ the S4 rotors- no problems.

The area that will contact first is the sides of the rotor tips, so if you are worried you should machine those down a bit as Racing Beat suggests.

I should also note that I run maxed OMP and 50:1 premix @ 10.5:1 AFR w/ leaded fuel when racing, so even if there is momentary rotor to side housing contact they probably won't weld themselves together.

Oil system mods to keep the bearings happy too.

 

I don't claim to know too much on this subject, but aren't the S4 stationary gears the rpm limiting factors more so than the rotors? I thought the S5 stat gears were hardened, therefor able to take higher revs or something to that effect. I am one for raising boost, not compression. I have no desire to ever switch from S4 TII rotors. I like the added strength (some call it weight) of S4 rotors. They seem less likely to be dented by a detonation. Maybe someone more seasoned can chime in on this.

BTW, you are actually wondering if you can achieve 25,500 rpm's. Your question was the rev limit of the rotors, not the engine. Just being an ***

 

The power falls off because of the fuel cut I believe?

 

There is no way in hell he is still running the stock ecu.

 

EMS is Power FC which has an adjustable rev limiter.

The only oil system upgrades I have are an FD oil pressure regulator. When I pulled the engine apart there didn't appear to be any problems with the stationary gears or bearings.

 

Which mods have you done to help?

Tear drop the eshaft?
Casting flash removal(from front iron mostly...)?
Other?
All of the above?

 

back to the top.

engine has nearly 1000 miles on it now after I rebuilt it, stock s4 rotors and stationary gears. rev limiter is currently at about 8000. I usually shift at 7500-7700. I haven't dyno'd it yet but it feels like it still pulling up into the high 7000s at least. it's hard to stay off the limiter in 1st and 2nd.

should I raise it? Will it reduce reliability to tach it up to 8k on a regular basis? I was thinking of raising the limiter to about 8200 or 8300. I know a guy running my same turbo on his FD and he takes it up to about 8500. But those are lighter rotors with better stationary gears.

 

couple of data points....

1. my black gsl-se would regularly get borrowed to go drifting, they would always tell me they just revved it up to the rev limiter in second. the 1st gen of course has no rev limiter. (i'd shift around 7500) i had a ride in the car, and with the tach pegged, you could hear it rev up. engine went about 150k, before it lost compression.

2. we used to run an FC in nasa's PS1 class. after the engine you've seen on ted website let go http://www.fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html we had some consultations, and Rick Weldon mentioned they had a guy back in the day who kept scattering engines. i'll skip the BS and just say once the rev limiter came out, failures stopped. our next motor was a junkyard engine, it went to 9400, for i think 2 seasons? we threw out the car, but that engine is in my garage, its TIRED, but everything except the bearings and seals looks fine.

i have seen stat gear failures, but it was a 4-3 upshift or something like that, engine ran, but it sounded like a honda

that all being said, 8500 is probably good, you wont have any troubles, over that you're kinda on your own

 

Well I highly doubt it will make power much over 8000. It has big exhaust ports but only a 1.00 turbine housing. All the bearings were replaced less than 10,000 miles ago. The needle buries at 8000 on T2's but the stock tach reads slightly low compared to what I'm getting on the Power FC, maybe 150-250rpm off.

more anecdotes would be nice

 

yeah the stock tach is off up top.

more? we have an 87 GXL that's stock except the old race car's suspension and wheels/tires, and its done 4 years of track days, 200,000miles on everything but the oil and water seals. engine is tired (my 72,000 mile 87 GXL feels like its got about 20 more hp) but it hasn't required ANYTHING except normal service (oil and spark plugs) since 2004 when it was bought/built. it also can't break traction in any direction, which is kinda funny

we once did have a stat gear come out, s5 rotor though, that kinda sucked, ruined the rotor and the center housing. and then the next motor is the one on ted site, we're blaming the rev limiter,as it would be on the limiter from the start finish stand to almost turn 3, which is like 30 seconds a lap!

if you're willing to talk about 12A's ive beat those too. since those have the 3mm iron seals, taking em over 8500 is bad, the seals can't take that load, 13B is different.

the other 12A is my PP. i had it balanced, and Glen says i can take it to 11k. hopefully he's saying that from experience! needless to say, i dont wanna be there when the clutch explodes....

 

anyone have more informed opinions or experiences to share?

 

The stat gears are the same, the S5 rotors are lighter then the S4 rotors and that's why they rev higher.

OP

I am running 9.4 rotors in my N/A turbo block and set the rev limiter to 8200 I think. My power falls off a bit over 7000 as well.

No problems, but I don't have many miles on it. Everyone that I know of has revved S4 rotors out to 8500 with no problems.

 

Rev it to like one Million

 

I thought the rotors spin at 1/3 the speed of the eccentric shaft? not 3 times it.

 

i have a pfc on my 88 tii and i did some test a while back because i was wondering the same thing. I dynoed and tuned and saw a little of power at 8000, but not really anything after that. you can rev higher than that, but in my opinion there is no point going past 8200. i don't even really go past 7800

 

why not 2?

 

The rotors do spin 1/3 of the eccentric shaft, so you are correct.