Raising the rev limiter on a stock S54

[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/

[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.

[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

[bigjae46]

I’d be ok with 8400.


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[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...

[jbfrancis3]

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

[Apex_80]

Mine is set at 8400, have cams/airbox/2.5" exhaust so peak power is right at redline.

[eacmen]

Seems like 8700rpm is around where the stock valve train starts to not keep up. The issues will be that...
-s54 rev limiter isn't great at retaining RPM, so you might rev over the set redline and have issues
-stock, you're losing power after 7900rpm-- so may make you slower than shifting. Idk what your power mod situation is
-rod bearings will become much more routine maintenance.

Wow 8700?!? Do you know how that was determined?

Along with rod bearings might be a good idea to make sure the bottom end is balanced and your harmonic damper is in good condition.

[jet_dogg]

I’ll report back after mine’s done.

[Obioban]

Seems like 8700rpm is around where the stock valve train starts to not keep up. The issues will be that...
-s54 rev limiter isn't great at retaining RPM, so you might rev over the set redline and have issues
-stock, you're losing power after 7900rpm-- so may make you slower than shifting. Idk what your power mod situation is
-rod bearings will become much more routine maintenance.

[bigjae46]

Change your gearing?

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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[Tbonem3]

Change your gearing?

[bigjae46]

Really don’t need a power increase, just more room to rev.


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[Tbonem3]

Ya, you probably need a holistic approach like you would with modding the car in general. Useless without a csl airbox, cams, port & polish, 2.5" exh...

What's there to be gained after about 7900 on a stock motor? Look at the dyno thread, particularly the baselines.

Even with mine @ 8200, with stepped headers and airbox, I still shift at 8k.

Valve float will be at like 9k I think. It's more a question of "why?" Imo. You're just wasting time you could be shifting and getting back in the meat of the torque no?

[Jimbo's M]

IIRC, I read many years ago that the stock valve train was good to 9K, maybe even a little higher, but the stock head is outta breath past the low 8's.