edhohoho

What is the purpose of increasing the rev limit? Is it safe for the engine to do so? Is there any point to do this on an IS250? Thanks.

MDHLexus

iTrader: (5)

There are various different reasons to do it. Usually it is so you carry out more power through higher RPMs which requires you to shift less in your first gears. So if you can raise the rev limit high enough you could get to 60 in 2nd gear which saves you the time of the shift to 3rd gear. The problem is most cars stop making power at very high RPMs (google a dyno sheet and watch it dip). The other reason to raise it, is to have your car be closer to the power band after the shift. If I shift at 6,500 then say it drops down to 3,000 RPM, I need to go another 1000 RPM before the car really starts working. If your car can shift with a higher rev limit at let's say 7,200... then once you shift your car will be ~~~very approximate~~~ 3,700 RPM which is much closer to your power band.

It is safe on most cars to raise it, obviously there is some math and engineering involved to see how high it can go. If they set it too high, lets say 8,000 RPM on our car, you can get valve float and all sorts of other internal damage. Make sure you run premium synthetic oil if you have your rev limit increased though. I had the limit raised to 7,200 on my IS250 and I loved it.

edhohoho

Thanks for the great explanations. When I emailed TTFS about the high rev option, they recommended leaving it stock as I would be unlikely to shift at that high an rpm in regular street driving. Did you find the benefit in every day driving too or mainly at the track? Do they use synthetic oil at the dealership? Believe it or not I still get oil changes there. I think I do it because I like driving the loaner cars though they mostly give out CT hybrids. Boo.

Gville350

iTrader: (10)

LOL! I redline my IS350 EVERYDAY to and from work!

edhohoho

Hilarious. Do you rev to 7200 every day?! Looking at the dyno graph posted on TTFS it seemed that horsepower drops off by 6000 and pretty precipitously at 6500. Not that I know what I'm looking at but I figured revving any higher wouldn't do much except put the engine at risk. Hope I'm not missing out on much because my order has shipped.

Jeff Lange

iTrader: (1)

The torque has a continuous downward slope after about 5800rpm, however the power stays relatively constant/increases until above 7000rpm. I don't often go above 7000rpm in mine, but at the track there were a few places I would have had to shift to the next gear and no longer had to, that was very nice.

Jeff

Gville350

iTrader: (10)

No, I'm not running a tuned ecu; however, I strictly only take back roads to and from work and it gives me ample opportunity to stretch its legs.

edhohoho

For the rev limit, do you recommend increasing it for all gears or just 2-6 since the limit in first gear is reached quite quickly. Thanks.

Gville350

iTrader: (10)

The engine doesn't care if it's in first or third gear reving out to redline. The only thing to consider is if you've got the right tire/suspension to keep the tire to the ground while reving it out. Plus, increasing the rev range allows the next gear to appear further up into the meat of the powerband.