socalJD

DOH ! I thought this way another synthetic oil thread . . .

StockIS350

don' sweet it, that's why there is a rev limiter, plenty people hit it due to the slight delay in shift, also the car reaches the limit so quickly

vlkcheng

An F1 car can accelerate fast is because of high power to weight ratio. An F1 engine can produce lots of bhp because it can rev up to 20,000rpm. The torque of the engine is only slightly better than your normal everyday car engine. If the book say your max power is at 6400rpm. Then try to change gear at around 6000rpm since it takes a few milliseconds to make a gear change. If you change when you see the needle is pointing 6400rpm, chances are the car probably change gear at higher revs eg 6800rpm. The power curve on most cars usually drop significant after it reaches max power. So it you do that, your acceleration time actually would be slower.

lobuxracer

iTrader: (2)

Didn't I say someone would say I'm wrong?

You missed the whole point about the F1 cars. In the late 80's when they had turbos, they made twice the torque they do now. Then, as now, the cars have no trouble accelerating hard. The weights have not changed significantly, but the rules have. The engineers solved the problem with rpm and gearing. They accelerated hard then and they accelerate hard now with half the torque they had when they had turbos.

Sure the power drops after the peak, but what if it only drops 20hp and shifting to the next gear from peak drops you 40hp? The point is, it's smarter to sit down with your dyno chart and your gearbox spreadsheet and analyse where you should be shifting, not blindly shifting at peak power. It's really rare that shifting at peak will net best acceleration. In the case of the IS, it is hard to imagine why shifting at or below peak power would be worthwhile since the engine holds steady hp over the last 1500 rpm before redline.

I'd personally rather shift at 306hp at redline to have the rpm drop and put me back at another point with the same 306hp instead of shifting as soon as I get to 306hp and drop down to 250hp. It won't feel as fast, but it will definitely be faster if you measure it with a watch.

isdsms

Man sorry to hear about that. That sucks!! Same thing happened to a friend of mine before his engine was broken in. We both have identical IS350 sport models with about 7500 miles on each of them now. Unfortunately for him, his car can't stay with mine. Right off the line, straight on up to 100+mph, he tails me. We have been racing for months now and he never wins. I hope speed is not important for you.
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Just mess'n with you! You'll be fine. Enjoy the car!!

suprafrank

Don't worry. As others said once a while is ok. Later on it should be fine to do that more often. My IS 350 is more than 5K miles now and I pushed it to 6.5K rev most of the time. I set the limit light at 6000 or so. It's fun to feel it going fast.

Gernby

iTrader: (1)

I probably spent an hour total time bouncing the rev limiter in my S2000, and it never showed any negative effects.

I also believe that shifting at the rev limiter will generate the best performance on just about any car, especially in the lower gears. Even if power drops off 60 HP, the gearing advantage of 1st over 2nd is way more significant. When I plotted out my HP to the pavement (dyno plot combined with gearing ratios) through all 6 gears in my S2000, there was a clear advantage to shifting at fuel cut all the way.

lobuxracer

iTrader: (2)

With an 83mm stroke, we're not anywhere close to violating mean piston speed limits at 6500 rpm. The only possible issue would be valve train problems, but again, at only 6500 rpm, it's very unlikely even with the rocker arms they used. Honda used excatly the same kind of set up (rocker arms and hydraulic adjusters) in the Nighthawk 750 way back in the mid 80's, and they were easily good to 10k rpm.

I bet you could over-rev the 2GR to 7500 without being worried in the slightest. I'd also bet the 2GR that Team Lexus is using redlines around 8700 rpm. With the right port work and cams, I can easily see another 150 hp out of this engine with that redline.

For the technogeeks:

Mean piston speed at 7230 rpm = 20m/sec
Mean piston speed at 8680 rpm = 24.01m/sec

This engine isn't stressed hard at 6500 rpm AT ALL.

Gernby

iTrader: (1)

What's wrong with our rocker arms?

lobuxracer

iTrader: (2)

Rocker arms limit valve actuation speed. Toyco/Yamaha used them to make the head more compact, but direct valve actuation (a la 2JZ, 2AZ, 1ZZ, etc, etc) would not be limited the same as a rocker arm. They behave like springs at very high speeds and they add mass to the process. The 2AZ uses buckets without shims (variable thickness on the buckets) and they weigh about 15g total.

Given the choice to use either, I would always opt for the buckets.

Gernby

iTrader: (1)

I'd be interested in learning more about these. Every car I've owned had rockers (some with rollers). Sorry to keep bringing up S2000's, but they have adjustable roller rockers.

x986

A race engine builder, (and very good driver) I used to use had a saying. "Horsepower sells engines, but torque wins races."

Gernby

iTrader: (1)

That sounds kind of like "there's no replacement for displacement", but that ain't true anymore either.

lobuxracer

iTrader: (2)

That's a very short way of saying, build the engine for best torque in the rpm range you plan to use. John Lingenfelter said that years ago in one of his books on building small block Chevys and it's still true today.

Yeah the peak number gets a lot of undue attention. The real meat is area under the curve - specifically where you plan to operate. If you compromise the peak number to get more area under the curve (because you need it), then sure, torque wins races.

But anyone who's been doing this for a minute knows if your powerband only needs to be 3k rpm wide, then build for best torque in that 3k rpm, and don't even bother with the rest of it. Who cares if a race engine idles at 1500 rpm?

Street duty is a completely different animal. Nobody wants to idle at 1500 rpm. Nobody wants an engine they have to rev to 3k rpm to pull away from a stoplight. So, you have to build differently. Torque needs to peak early and be as flat as possible. So everything is different - cams, ports, exhaust, tune - it's all got to match intended purpose.

If you want a really interesting study in torque, look at generator sets. Those engines operate in an extremely narrow rpm range, and everything is optimised to make lots of torque in a range of about 10 rpm. The Miller cycle was originally developed for just this purpose. Ship engines are very similar because they trim for best speed/unit of fuel used. Outside that range, they're worthless.

4TehNguyen

iTrader: (1)

shouldve said torque at high rpms wins races (which is horsepower)