There was a very interesting article published on AutoSpeed (http://www.autospeed.com/cms/A_2133/article.html) earlier this month about measuring acceleration. What makes it cool is that they used a KL Verada GTVi :cool:

To cut a long story short they found that the best acceleration is obtained by winding the engine out to the limiter in each gear..



In the case of the GTVi it is worth taking the engine to the rev limiter in each gear. This is because acceleration prior to the rev limiter remains greater than at any rpm in the next higher gear. This is especially the case when shifting up from first gear where - even when taken to the rev limiter - there’s still a big step down to the acceleration in second gear.


Since the gear ratios in the 5spd tiptronic auto are identical to those in the manual I wonder if the same applies - it would be an interesting experiment :think:

It's all about the torque curve, not so much taking it out to the rev limiter. Thing is, isn't the rev limiter around 7k on our engines? I'd have thought that's way past an optimum shift point.

I read somewhere that you meant to shift slightly after peak torque as power curve typically
peaks after the torque. Can't remember the argument though.

Yeah I know that one too Vlad, I can't remember where I read it..but i have a feeling it was on another forum we're both on. Might've been MOGWA.

This article was all about measuring acceleration.. what those results are saying (and I'm reading from the graph which was included in the article) is that at 6400rpm in 1st gear you are accellerating at 0.38g where as the fastest you are ever accelerating in 2nd gear is 0.31g, meaning that no matter when you perform the up-shift to 2nd gear as soon as you hit 2nd gear you will be accelerating more slowly than you were in 1st gear.

They also made the observation that..



As you can see, acceleration drops away steeply at high rpm. Note that the shape of these acceleration curves is indicative of the Verada’s GTVi’s tractive effort at different rpm. (Tractive effort is the force being applied at the tyres and is commonly measured in Newton Metres.)


so even looking at the problem as a function of torque (or in this case tractive effort at the wheels) the fact of the matter is that at no point in 2nd gear are you exerting the same tractive effort at the wheels as you are in 1st gear - so you may as well hold 1st gear till it stops.

Makes sense. As per my .xls:

1.Gear Ratio 2.842
Diff Ratio 3.744
RPM 7000
Speed km/h 79.73

2.Gear Ratio 1.495
Diff Ratio 3.744
RPM 3700
Speed km/h 80.12

So, dropping from whooping 7G to 3700 - the power curve is only halfway up at 3700.
How to avoid this? To get a quicker diff. And that would cost...... :shock:

It's all about the torque curve, not so much taking it out to the rev limiter. Thing is, isn't the rev limiter around 7k on our engines? I'd have thought that's way past an optimum shift point.

I thought the Rev limit is set at around 6400-6500rpm (well it was in my auto)??? and redline being 6200rpm???

I thought the Rev limit is set at around 6400-6500rpm (well it was in my auto)??? and redline being 6200rpm???
Yours a 3.0 ltr 4 spd auto, the GTVi is a 3.5 ltr with 5spd tippy auto so can't expect to have
the same rev limiter setting.

For the point of argument, AutoSpeed stopped measuring at about 6400rpm so consider that the rev-limiter.

Yours a 3.0 ltr 4 spd auto, the GTVi is a 3.5 ltr with 5spd tippy auto so can't expect to have
the same rev limiter setting.

Being a 3.5 might change the limit, but so what if it has 5 or even 6 gears, the transmission has nothing to do with how hard an engine can rev before damage starts to occure lol

My dads old auto TH reved to 6400 too, so there you go, but I have read in the past on this site people claiming to have reved close to 7,000rpm so I dunno :confused:

why are they so different ? don't they all limit at 6500? but sometimes it can go up to 7000 and it will bounce of it?

Why?
Heh, good question....
I once (accidentally when showing off to a mate :redface: ) revved 3L Auto locked on first gear to 7G and it sounded/pulled sweet. No rev-limiter cutting off there! Strange.


why are they so different ? don't they all limit at 6500? but sometimes it can go up to 7000 and it will bounce of it?

mine was rev limited at 7200 RPM - approx 109km/h in 2nd gear ;) 5spd manual TH

now - the best shift points for me was just bove 5500RPM - due to the torque of the engine and the way the cams were - so yeah - i had no need to rev past redline!!

It was acutally nearly 2 years after owning my car that i found the rev limiter

Manual

Note that the comment about going to the rev limit, if you look at the graph, only applies to first gear. Second gear acceleration overlaps with third gear acceleration at about 6000 rpm, so that should be the change point. For that car/ gear ratios anyway. May not apply to other models.

When they say that a VR-X/ Sports manual is 0-100 in 7.1sec and the 5 sp auto is 7.5 ( i think ) do they measure the auto in "D" or do they use tiptronic? Is the manual gate mode faster than the "d" mode or is it the same? I usually change my gear at 5200 with my TJ sports in S/A mode, runs out of puff after that so dont bother going on ( stock as a rock ). Dont see any upside to upshifting any higher than 5700 in first.

I read somewhere that you meant to shift slightly after peak torque as power curve typically
peaks after the torque. Can't remember the argument though.

the best accelleration point may be at peak torque but if you change gears at peak torque u still lose about 2000rpm (cos of the gear change) and suddenly drop well below peak torque... so ya probly only wanna rev to the point that when u change gears u end up on peak torque and ur ready to go again..

the best accelleration point may be at peak torque but if you change gears at peak torque u still lose about 2000rpm (cos of the gear change) and suddenly drop well below peak torque... so ya probly only wanna rev to the point that when u change gears u end up on peak torque and ur ready to go again..

True, torque wins races, hp sells cars.

the best accelleration point may be at peak torque but if you change gears at peak torque u still lose about 2000rpm (cos of the gear change) and suddenly drop well below peak torque... so ya probly only wanna rev to the point that when u change gears u end up on peak torque and ur ready to go again..

Umm... you talking peak torque or peak power? They're not at the same point. Torque is the measure of pulling and power is the measure of work or torque x rpm or for cars. That's why most people would shift around peak power and when you shift you're closer to peak torque. If you shift at peak torque you will drop a fair bit away from peak torque.

With mine, I find revving 1st right out to redline then shifting to 2nd keeps the engine in the power/torque zone.

By shifting earlier the revs would drop too much in 2nd?

So you sacrifice a little speed in 1st to get a good shove in 2nd! :D

PS if someone already mentioned this my apologies and im talking about 4sp auto :confused:

With mine, I find revving 1st right out to redline then shifting to 2nd keeps the engine in the power/torque zone.

By shifting earlier the revs would drop too much in 2nd?

So you sacrifice a little speed in 1st to get a good shove in 2nd! :D

PS if someone already mentioned this my apologies and im talking about 4sp auto :confused:

A agree, I found this out when timing my car 0-100, if I left it in 'D' it'd drop down into 2nd at around 5500 rpm, the RPM which it first hit in second was below peak torque so it took a bit to really get going again. I found by revving 1st out to about 6500-7000 it drops down into 2nd right into about the peak torque zone, hence it pulled harder right after the change compared to leaving it in 'D' and cut a bit over a second off my 0-100 time :D . I did this timing when it was stock.

well set out ratio gearboxes aim to get changes happening between regions of peak power before u shift and dropping into region of peak torque in the next gear. as some ppl above have sort of pointed, its usually better to rev past peak power up close to redline so that the gearchange drops the engine into good torque with the next gear, changing too soon will create more waiting for the torque to arrive and lost time with these cars especially if they r modded and power curve is shifted up the rev range.

i found the way to trick the rev limiter on my 4 sp auto is that going "manually" from 1 2 3 D instead of just left in D, that way it will go to 7'000 instead of 6'400 and is fine, pulls hard right to 7'000 but it is modded not stock so pwer curve is moved up.

My TE, 3.0 5spd, will rev to 6,750 before it bounces off the limiter.

If im givin it a bit, i tend to change gears usually bang on 6000, i've found, that anywhere below about 4,500 significantly reduces the g's in any gear.

Go the Magna :bowrofl:

I was having a read of my owners manual last night, and as I was flicking through the transmission section there was a part stating the maximum speed you should not exceed in all gears. In 3 litre auto, they say you should not exceed 60 km/h, lol , I've almost got mine upto 80 before in first, and they also said to always be sure to keep the tacho out of the red zone, lol , the red zone starting on mine at 6000 rpm :shock:, where as I've had it at 7000 rpm before :shock: . Im guessing its just mitsu being cautious, I hope so anyway .

I was having a read of my owners manual last night, and as I was flicking through the transmission section there was a part stating the maximum speed you should not exceed in all gears. In 3 litre auto, they say you should not exceed 60 km/h, lol , I've almost got mine upto 80 before in first, and they also said to always be sure to keep the tacho out of the red zone, lol , the red zone starting on mine at 6000 rpm :shock:, where as I've had it at 7000 rpm before :shock: . Im guessing its just mitsu being cautious, I hope so anyway .
Redlines arnt limits..... They are targets :badgrin: