How high can we really rev?
 

I've seen some in-car videos of some peoply on this forum on the track revving way past the 8,000 RPM redline....what can a healthy engine handle? My car's 7,500 buzzer no longer works and I'm a little hesitant to pass the 8,000 mark...Am I babying it a little too much?

This is a tricky question.

1) The stock rev limiter kicks in around 8,000 (or something like that), so unless you've modded that, you will be stuck at 8k.

2) The loads on parts like the stationary gears, bearings, etc, go up quite a bit from 8k to just 9k according to some old mazda documents that I have. The FDs are better able to deal with this from the factory compared to the FC/FB, but that doesn't mean that 9k is "safe".

3) Assuming your rev limiter is gone, and your internals are solid.... what's your fuel injector duty% going to be at... say... 8500? Keep in mind that as the RPM goes up, the time in which to squirt in gasoline goes down. Don't run out of fuel injection capacity...

4) What is your ECU programmed for? if you plan to make excursions to 8500 or even more, I hope that your maps in your ECU have mapping points for it.... otherwise, it will likely just use the 8000 RPM numbers no matter how high you rev.

5) What is your dyno like? Holding out to 8500 or more doesn't make much sense if your power curve doesn't fit. For example, on my particular car, the old Excel spreadsheet says that with my dyno, I should shift at something like 8400 in first->second, 8100 second->third, 8000 third->fourth, and 7500 fourth->fifth. (These are rough estimates off the top of my head). The point is that in first, I get no traction anyhow... so I probably am hitting 8000+ due to wheelspin anyhow... and after getting into second, there is really little value in exceeding the redline. What does your dyno look like?

Soooo the short answer... is that unless you're really really sure that's what you want to do and you plan for it... the stock redline is where you should shift. 99.9% of the FDs on this forum don't "need" to go over that in my opinion.

i think it all depends on how ghetto your car is.

The intake manifold on my t2 limits my peak power to around 7000-7500rpm and it just dies off from there.

Does the FDs intake manifold come into design as a powerband limiter?

and if you drive even moderately modded cars, it depends on the setup of the engine. most setups just do not produce any more horsepower beyond 7500RPMs so no reason to start stressing components for a loss in power.

my TII is setup for slightly higher RPM power but i still cut off and shift at 8k, just slightly past my powerband but that is at the strip, not the track.

I've keep reading on here about how you get power-lose from revving past 7500, you can rev higher than that... but you would go faster by shifting up

That depends if you're on stock twins or not. A big single will still be getting power after 7500

I baby my car, i dont think i ever revved past 7500.

Normally when i got WOT, i shift at 7k lastest.

The highest I've ever gone up to is 9400 rpms here and there. However, my powerband seems to slightly fall off after 8000-8500. It just seems to "hold" right after the 8000 mark. No gain really, after the 8000-8500 mark

8k all day

I run to 8k+ all the time as well. My friend christians 1st gen we dropped a monster streetport motor in built by kilo racing, holly carbed, direct ignition *4x msd 6al boxes* etc revs 10k daily, of course scatter shields are needed just incase at that point incase your flywheel/clutch assembly decides to grenade lol.

you can run past the peak power but i bet most of you guys are peaking before 8k, unless you have a high A/R turbine

Dont lamans and indy cars rev to 14k ish?

^^ I don't think he was asking how high can ANY car rev... he asked how high a production model FD can rev.

/blush





i feel sheepish now.

I notice nice power from 8k-8.5k in my bridgeported single.

And F1 cars are limited to 19k rpms per regulations. In other words its likely that they could go higher if they were allowed to.


19k rpms is ridiculous for any engine, let alone a piston engine with reciprocating valves...


BC

i hit 13000 in third gear before it blew up. let just say it was worth it.

More like, the engineers would find a way to make an engine survive higher RPM for a little while, after first finding a way to make power up that high. At such high speeds, airflow/cam timing is a problem but a bigger one is simply getting the fuel to burn in time, kind of like the smoke limit in a Diesel engine.

Most touring-car series have 8000rpm limits, or similar.

The new S2000 (that's Super 2000, not some Honda junk) stage rally class has an 8200rpm limit.

They still make about the same power than the existing WRC (turbo) cars, but then, the inlet restrictor means they make their peak power at around 5200-5500rpm...

WAY off topic:

Just in case anyone wanted a shiver listening to how awesome an F1 engine sounds http://www.youtube.com/watch?v=o_QyUD6V5_I


BC

I don't follow F1 too much, but I understand that many teams have cut max RPM by a few thousand, now that engines have to be used in *two* races...

Even at the top level, RPM = Ruins Peoples' Motors.

When you watch that video they show the computers tach for a few seconds and you notice that it tops out just shy of 18k rpms before shifts. I cant say for certain, but based on all the shifting I think that the throttle is being controlled off of a telemetry (sp?) map from a previous race. If thats the case it would add some more credibility to what you are saying.

BC