Raising the rev limiter on a stock S54

[Obioban]

A local shop to me, RRT, once mentioned that the stock harmonic balancer is a primary consideration to raising redline and that it cannot exceed 8,400rpm

RRT knows their stuff-- sounds like 8400 is as high as you should go.

... especially if you have a light weight flywheel, making the harmonic balancers life harder...

[bigjae46]

I’d be ok with 8400.


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[eacmen]

I’d be ok with 8400.


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might be worth reaching out to ATI to see what RPM their camper can handle.

https://store.vacmotorsports.com/vac-motorsports-harmonic-damper-by-ati-bmw-s54-p3010.aspx

[Mattn1192]

Hassan tuned my car. Raised the rev to 8250. I have headers & exhaust. He’s been very informative and did a great job with my car. Mentioned when racing to basically redline. Not sure if it’s the same with a fully stock s54. Btw, if anyone’s looking to get tuned, he’s the guy. Looks like many others in this community also agree.

[jbfrancis3]

Stumbled across another data point for the stock harmonic balancer: see mention of spinning it to 8,700 “without any problems.”

https://store.langracing.com/lang-racing-dry-sump-kit-bmw-e46-m3-z3m-z4m-s54-engine/

[SliM3]

8500 will definitely put your stock fuel injector duty cycles @ >90%. I suggest throwing in one size bigger if you go that high.

[Rudbari]

Why not go with 3.85 from e92 m3 manual

If I can get a few more revs I can use shorter gearing without an upshift. I’m on 3.73, want to go up to 3.91.

I know there is an argument that taller gears are better but data from my experiment tells a different story. If I compare data to someone with a 4.10, they have a distance time delta and speed gain advantage when the car straightens and under full throttle. 4-5mph at some points. RPMs are slightly higher, more accurate and precise throttle steerIng.

Real world, I only really catch him through turns. Most cars I run down in turns. I’ve driven E46s with 3.91s, it’s faster. Can be more of a handful but I’m OK with that.


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[bigjae46]

I've considered a 3.85. Its shorter but the 3.91 is more optimal by my calculations. I could very well be wrong. I am willing to take the risk. I've rebuilt 3 diffs so far so I'm getting building skills down. Not a big deal if I have to swap in a different gear ratio.

[Anri]

I've considered a 3.85. Its shorter but the 3.91 is more optimal by my calculations. I could very well be wrong. I am willing to take the risk. I've rebuilt 3 diffs so far so I'm getting building skills down. Not a big deal if I have to swap in a different gear ratio.

Bigjae46,

I have a question, you mentioned that your car not street legal.
If its not how do you go the track ? via trailering the car ?

Regards,
Anri

[bigjae46]

Bigjae46,

I have a question, you mentioned that your car not street legal.
If its not how do you go the track ? via trailering the car ?

Regards,
Anri

Trailer. Its fun to drive on the track...not so fun on the street.

[Anri]

Trailer. Its fun to drive on the track...not so fun on the street.

Hi,

Okay.

What is your home track/s top speed you are reaching out ?

Give me the top speed of the track which has the longest
straight you ever get. The lower tracks with lower top speed are
not important for what I have in mind.

Regards,
Anri

[bigjae46]

Hi,

Okay.

What is your home track/s top speed you are reaching out ?

Give me the top speed of the track which has the longest
straight you ever get. The lower tracks with lower top speed are
not important for what I have in mind.

Regards,
Anri

Right now, top speed on my home track is 125mph which was set in the Jun when it was 90+ degrees outside, on NT01s, and some room for improvement. I figure I will be around 129-130 with some improvement, cooler weather and stickier tires. I want to stay in 4th gear to save a shift.

Fastest track I will drive at is COTA - at 139 mph lifting at the end since I had a plywood splitter causing the front end to porpoise. Probably going to be around 142-143mph if I don't have to lift. I don't see that getting much higher. With a 3.91, I should be fine at any track in the US.

[repoman89]

8400rpm would be a really nice set point if it’s actually mostly safe. That’s an even 5% increase which would mostly compensate for the 8% speed decrease in each gear with a 3.91 while still providing the 8% torque to the wheels boost. Plus it sounds like with the full set of bolt ons the car can make peak power up there.

As noted already though, would definitely have to be more careful about the limiter since it can be a couple hundred RPM off.

[Anri]

Right now, top speed on my home track is 125mph which was set in the Jun when it was 90+ degrees outside, on NT01s, and some room for improvement. I figure I will be around 129-130 with some improvement, cooler weather and stickier tires. I want to stay in 4th gear to save a shift.

Fastest track I will drive at is COTA - at 139 mph lifting at the end since I had a plywood splitter causing the front end to porpoise. Probably going to be around 142-143mph if I don't have to lift. I don't see that getting much higher. With a 3.91, I should be fine at any track in the US.

Hi,

Okay and one more question, you mentioned NT01. I assume
you are running 275 35 18 ? as no less tires is used in the
E46M3 world.

Anri

[bigjae46]

Hi,

Okay and one more question, you mentioned NT01. I assume
you are running 275 35 18 ? as no less tires is used in the
E46M3 world.

Anri

275/40R17 which is the same diameter as a 275/35R18


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