Transmission Setup for Mid Range Power

[Woodski_427]

A question for gearbox gurus:

What is the best way to set a transmission for a narrow mid range torque/power peak?

Specifically I am referring to the likes of the '90s Daihatsus (Move, Mira) and the VW 1200 (Beetle/Bus) that get the big mid range spike in torque and power when you install the mid RPM turbo. Obviously these would be setup for twisty tracks or rally where the punch of torque gives you the acceleration at the cost of top end speed.

I normally don't bother with much in the way of tranny tuning, but there must be a good way to make the most of this power band. I guess there is a taller final drive with close gears, or wide 'box with lower geared final; either way short shifting is necessary.

I haven't been able to get my head round this, and have struggled to find any info on this type of setup, and tunes seem to favour high RPM tuning. Help or links much appreciated 👍

 

[MrPainCake]

it really depends on the track and what rev range your spending more time in, for something like nurburgring, i always take a mid rpm turbo over the other 2. were as somewhere like high speed ring, cape ring or le mans i take a high rpm turbo because i spend most time around the redline keeping the car in and around the powerband, utilise the tools given to you by the read outs in the tuning sheets for were the shift points are, and where the power band is

for transmission, take the longest straight, and make sure car pulls evenly through all gears, and that the top gear has enough room for drafting,
hope this helps

 

[trackripper123]

Make the shifts happen at a lower rpm I guess, fiddle around with the gear ratios and watch the graph change, you want the bottom of the lines towards the middle of the axis representing rpm, not the top as you would normally do.

 

[claudiorz]

Make the shifts happen at a lower rpm I guess, fiddle around with the gear ratios and watch the graph change, you want the bottom of the lines towards the middle of the axis representing rpm, not the top as you would normally do.

You don't really need to do this. Just set a long final gear (because you will want to achieve the top speed several rpm before reaching the maximum rpm of the engine) and be sure to stay in the peak of the powerband by shifting earlier than the red line (how early depends on the car).

 

[GTV0819]

In Dirt & Snow, sometimes I use mid-to-high range Turbos since I use several cars for off-roading. The advantage of the mid-range turbo for the car is that it has higher peak torque that is even achieved at a lower rpm than a high-range turbo, which can help the car in the start but in the long run, the high-rpm prevails, due to higher peak HP achieved at a higher RPM, though this is not the case in my old Samba bus Van '62. Don't know about the others, though.

 

[Woodski_427]

Thanks for the replies.

The reason for doing this is because on the cars I mentioned the torque and HP is (much) higher with mid rpm than when using the high rpm turbo, and it's a bit of fun!

The use is fairly limited as pointed out because most of the time on any reasonably fast track you will be in higher revs and missing the very narrow power band, especially as these are low power cars.

I will go back and try suggestions 👍

 

[trackripper123]

Thanks for the replies.

The reason for doing this is because on the cars I mentioned the torque and HP is (much) higher with mid rpm than when using the high rpm turbo, and it's a bit of fun!

It's not the Merc SL600/65 AMG is it?

 

[Woodski_427]

It's not the Merc SL600/65 AMG is it?

No, the kind of cars are in the OP, like the Daihatsu Mira/Cuore, VW 1200: they get very narrow peak torque and power around 5k, the curve is pretty much a steep straight line up and down, like the corner of a triangle. The peak torque is quite a lot higher than with high turbo - I'm trying to get gearing to make use of the torque for good acceleration.

There are other cars of course and I've seen one that has more torque and HP with a low rpm turbo.

I did some quick testing on the Route X test with a Mira, and acceleration times can be greatly improved over the high rpm by getting the shift at around 6k and dropping just below 5k. This is at the expense of top speed of course as you drop out of the power band at around 115 mph and the high rpm will beat you to the finish line.

 

[trackripper123]

No, the kind of cars are in the OP, like the Daihatsu Mira/Cuore, VW 1200: they get very narrow peak torque and power around 5k, the curve is pretty much a steep straight line up and down, like the corner of a triangle. The peak torque is quite a lot higher than with high turbo - I'm trying to get gearing to make use of the torque for good acceleration.

Oops, didn't read, stupid me. If you use MT you can get a lot more control out of shifts to stay in that narrow power band, but lazy auto drivers like me have to compensate somewhat by widening the gearing a little bit.

 

[MrPainCake]

My CR-X @ 375pp is a perfect example of finding shift points.
When you go to tune a car, in the box in the right corner you get a Max.power/torque curve graph and a current performance listing:

using the current performance tab look at the Max. power and Max.torque read-outs, thats 2 shift points, lucky for me and my CR-X there both at roughly the same spot.
but say for my Daihatsu OFC-1 ive got max torque at 3000 rpm, and max power at 6000 rpm. but because shifting at 3000 rpm would be absurd id shift at 6000 rpm. hopefully this shed some light on what to do. you dont really notice how much of a difference shift points make in higher powered cars until you go to a lower 350-400pp car

 

[Woodski_427]

So, if anyone is interested I think I've gotten to the bottom of it - there is really only one way to achieve this in GT5: wide gears and longish diff'.

Before looking at the transmission in depth, I wondered if there was a clever way to do it - I suppose in my head I was thinking maybe a narrow 'box to keep revs in the power band and where the red line of the engine wasn't especially relevant, and then set the final drive accordingly. I now realise this is not possible - before I didn't realise how the gear ratios (lines on the graph) were anchored to the engine redline and changed with the final drive.

Using a Mira/Cuore as a test mule, I've been able to make good improvements on 0-100mph test times with better gears and shifting. It's a bit harder to make the most of it on the track of course as you must keep eye on your shift points.

I did make a 'Ring version with longer FD which gives a top speed reading of 190mph in the tranny setup, and this keeps rpm in the zone when flat out in top gear. But really the improvements in time for this type of driving over high rpm turbo are negligible.

Thanks to those who responded 👍

 

[trackripper123]

Yep, wide gears is how it's done, shifting so that the new gear starts in the required rpm zone.

 

[xghosthunterx]

it really depends on the track and what rev range your spending more time in, for something like nurburgring, i always take a mid rpm turbo over the other 2. were as somewhere like high speed ring, cape ring or le mans i take a high rpm turbo because i spend most time around the redline keeping the car in and around the powerband, utilise the tools given to you by the read outs in the tuning sheets for were the shift points are, and where the power band is

for transmission, take the longest straight, and make sure car pulls evenly through all gears, and that the top gear has enough room for drafting,
hope this helps

Thanx for the tip on turbo 2 only on nurb,I spend a lot of time on this track and is not the easiest to tune for,would u suggest a middle type of tranny tune,meaning gearbox is not tight or not wide,just in the middle range??