Safely increase the redline

[thexav]

Most power is produced at the upper end of the rev range so is it possible to safely increase the redline of a car engine?

What mods would you need to do? How much leeway is there in the average cars setup?

I was just thinking some Hondas rev all the way to 9000rpm other cars seem to be limited to 6000rpm and diesels rarely manage over 5000 before a limiter cuts in.

 

[SLEEPER]

Not really 100% correct -
Yes more bhp is produced at the top of the rev range, But that is not so with torque which is the driveable amount of power you have

It is the engine design itself that determines the bhp and power band . The rev limit is usually just a physical one based of what is practical and the redline is an indication of the safe limit so it isnt a good idea to just rev most engines higher.

You wont get any gains without some engine modifications anyway besides by then sensibly tuned engines are in the epower bank for the next gear by then.

 

[obi_waynne]

As Sleeper says your power band should be wide and start around 2000rpm or so, top end gives little extra.

Higher rpm can give a little more top end power but you'll need to make sure your engine is fully balanced and blueprinted, the gearbox and driveshafts should also be balanced. The pressures higher RPM yields also puts the engine under stress so head gaskets, forged components and the like are all recommended.

There is a lot that can be done at normal RPM to tune an engine so you don't have to worry about stretching the rev limit.

 

[HDi fun]

As mentioned above there are many factors that determine an engine's torque output. You won't gain anything at all by simply raising the upper rev limit. The red line indicates the end of the usable rev range. The rev limiter is there to prevent over-revving and possible damage to the engine. Of course if you manage to shift to a lower gear and over rev there's nothing the limiter can do to help.

Many people think that using the whole of the rev range will shorten the life of the engine. I disagree. So long as maintenance is timely you can safely use the whole rev range. Don't do this with a cold engine though.

Additionally, under - revving, labouring the car in too high a gear is very damaging to the whole drivetrain, not just the engine.

 

[RobBentley]

You'll find more revs doesn't always make more power, hugely depending on the engine. Quite often the turbo for example is so far off its peak efficiency that the torque is dropping quicker than adding revs will create more horsepower. I've seen so many cars on the dyno that the power starts tailing off quite heavily from say 6k/rpm so even revving out to the factory rev-limiter of say 7k doesn't keep power climbing. As mentioned, it really depends on the engine though.

 

[PDDesign]

There's two things there: the maximum revs that the engine can safely sustain, and the rev range where maximum BHP can be developed.

It's entirely possible to create an engine that develops its max power at 9000rpm, but for that engine to throw a rod at 8000rpm, so you could never safely use it. The most effective way to raisemax power rpm is through increasing the duration of the cam.

Engines with steel bottom ends tend to withstand higher rev's - and balancing can also help. A cheap way to increase the maximum rpm is through ARP bolts or similar, but you've still got to ensure that the rest of the engine can keep up