Drok149

With the recent availability of tuning capabilities I'm very interested to see how the increased rev limiter effects times. Previously it was well documented that kissing the rev limiter yielded the best times. I was always curious why this was the case and now I'm even more curious if kissing the rev limiter at 7200 will yield the quickest times again.

tas02

iTrader: (2)

Interested as well. I specified the 7200 limit for my ecu reflash, as I intend to run it at the drag strip & autocrosses.
Our tracks here don't open up until mid March, so thery'll be plenty of time to get the unit to "learn".

minator

It probably will. From the TTFS dynos it looks like the ISF is still making ~275 wtq at 7200 rpm. Inputting this into a quick excel sheet I made, holding gears 1-4 to 7200 rpm will put maximum average power down.
rpm.........gear 1....gear 2.....gear 3....gear 4....gear 5....gear 6
4000.......4454......2640.......1806.......1419......1193......969
4250.......4589......2720.......1860.......1462......1229......999
4500.......4657......2760.......1888.......1483......1247......1013
4750.......4630......2744.......1877.......1475......1240......1007
5000.......4589......2720.......1860.......1462......1229......999
5250.......4616......2736.......1871.......1471......1236......1004
5500.......4589......2720.......1860.......1462......1229......999
5750.......4522......2680.......1833.......1440......1211......984
6000.......4454......2640.......1806.......1419......1193......969
6250.......4387......2600.......1778.......1397......1175......955
6500.......4320......2560.......1751.......1376......1157......940
6750.......4185......2480.......1696.......1333......1121......910
7000.......3942......2336.......1598.......1256......1056......858
7250.......3712......2200.......1505.......1182......994........808

numbers are multiplied by ISF gear ratio/final drive

lobuxracer

iTrader: (2)

Average is unimportant. Area under the curve is what counts. Graph it and measure it, then you can be sure. I doubt it will be better.

Drok149

Any idea why hitting the rev limiter yields the best times on 1/4 mile runs?

Gymkata

It's just a guess, but I imagine kissing the rev limiter generally gets you the fastest times because when you shift to the next gear you are at a better part of the power band to continue strong acceleration.

lobuxracer

iTrader: (2)

Ideally, you want to be as near to peak power on both sides of the shift, so shifting after peak power to drop back to the same power level gives maximum area under the power curve. Area under the power curve is king for acceleration despite what many confused persons will try to tell you about torque being all important.

If torque does not peak and remains flat all the way to redline (a la Hellcat) there is no advantage to shifting anywhere but at redline. With our cars, the power drops pretty quickly as you approach redline, but not enough to make shifting under redline a better trade off.

There's a mathematical analysis you can do to determine shift points. As the number of gears in your transmission increases, this analysis becomes less valuable because the overlap between gears means you can stay closer to peak power with less concern about the useful rpm range of a given gear ratio.

SubOrbital

I was always taught that the theoretically best place to shift is peak torque.

lobuxracer

iTrader: (2)

You were taught by someone who does not understand power. Torque is a single component of power and engine torque is fully adjustable through gearing and tuning. The peak torque shifting "theory" does not survive mathematical scrutiny and never has just as shifting at peak horsepower does not survive mathematical scrutiny and never has.

ISF4life

iTrader: (30)

Lolz ahahahhhaha i can understand astrophysics but after reading thru all these pages lolz my head is spinning lolz

MR2QIK

Graphs & maths aside, I believe it highly likely the increased limiter will yield a small improvement in 1/4 mile. It's not ideal, but it's better than losing time shifting & or halting acceleration completely by banging against the limiter. If you're running a 12 flat & holding shift @ the end, it may be that small difference needed to barely break into the 11's. On the street or track, I wouldn't see the need to go above 7000rpm. I personally will get the limiter increased slightly to give it a better chance of hooking up in 1st when spinning & avoid kissing the limiter @ 6800rpm when I'm a bit too slow to react.

I know Novel apparently busted a motor by over revving, but there's a big difference between 7000rpm (200 more than stock) & experimenting with 8000rpm.

I'm eager to see how a well engineer cam upgrade will help. It'll potentially change the game & enable the 2UR make useful HP up till 7000rpm.

eddyisf

Ill be seeing some "raise the Rev limiter they said , it'll be fun they said " soon if my motor was built to hold that abuse after stock Rev limit I would do it... but it wasn't so I just left mine stock I asked rafi and Simon what they recommend before they flashed mine and they said to leave it stock you make no extra power after 6800 so my take it up there ur just playing with fire after that ...

tas02

iTrader: (2)

6800 rpm in 4th gear = 119 mph* with a stock size tire. That's why I decided to go with the 7200 option on my tune. A few extra rpm will get me through the traps before having to shift into 5th.

And hopefully, she stays together. If she lets go, I'll be the first here with the RCF swap (7400 redline from the factory).


*Caymandiver's trap speed on his 11.87 run. He crossed the line in 5th, as he was running a shorter 245/40 x 18 drag radial.

One2beH8ed

Like it was said above. Guys spend millions engineering engines. If they wanted to it rev that high stock they would have done it. Due to not being able to build these motors I wouldnt push it and most likely you are going to lose power. Just rpms get higher doesnt mean its always putting down more power.

I agree that you want to kiss the rev limiter. That way once you shift your higher in rpms in the next gear. We have all spun through first went shifted to second and car bogs down due to low rpm and you have seconds your losing to get car back up to power band and get moving.

for the extra 200rpms and the chance to blow a 10k motor. I would say NOT WORTH IT.

MileHIFcar

Do you guys really think raising it to a 7200 rpm redline/limiter will put the 2UR-GSE at risk of catastrophic failure?

Look I'm not for it at this point or against it, I'm still waiting on some feedback/dyno's/1/4 mile runs etc....... but I'm having a hard time wrapping my head around that fact that spinning the engine another 400 rpm on certain occasions will put the motor at risk of early failure or something along those lines

I'm guessing the Lexus/Yamaha engineers engineered the motor with some safety margins in the motor to prolong the life of the 2UR-GSE, but as we have witnessed with the motor now being able to be tuned that they left power on the table to be extracted.

What do you guys think?