Raising the rev limiter on a stock S54

[bigjae46]

I know most tunes raise the rev limiter to about 8200 rpms. Has anyone raised the limiter to 8500 rpms on a stock motor? Long term results?

My car is not street legal and will only see the track. I don't mind doing extra maintenance like more frequent valve adjustments and rod bearing replacements.

[Lukem3]

If you want to go higher rev and be safe, upgrade your valve train. Get higher rev springs, maybe even different cams and valves if you have the money

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[heinzboehmer]

I think Hassan runs his with an 8500 rpm limiter. You could try reaching out to him

[Lukem3]

Valve float is what you need to be careful of. When the valve opens and isnt able to close fast enough and kind of hangs open, which can cause valves to hit. If it was as easy as just a tune everyone would do it

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[erickhoyos]

I’ve done it once and never hit 8500 again out of fear, went back to 8k. Plus isn’t there oil deprivation when you go to higher rpm range?

[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.

[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?

[bigjae46]

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


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[Tbonem3]

Change your gearing?

[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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[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.

[jet_dogg]

I’ll report back after mine’s done.

[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.

[Apex_80]

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

[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