Lets talk Manual gear ratios

[bradc]

As owners of manual VR-4's will know, the gearing is very short highway cruising sees you at 3000rpm in 5th, a small movement of your little toe will see you hitting boost, and I very much doubt this can be good for fuel economy!

Fortunately there are options out there. The gears in our gearboxes can be swapped with EVO 5 speed's from EVO 4 up to 9. Of interest are the 5 speeds in the EVO 7 and 8 which have a longer 5th gear, 0.720 compared to our 0.761. This will see you go from 112.6kmh at 3000rpm to 119kmh at 3000rpm. Or 2930rpm at 110kmh versus 2770rpm at 110kmh.

To be honest this isn't much of a difference. However if you do get a full EVO gearset you get the advantage of having a longer 1st and 2nd gear as well. The stock VR-4 1st and 2nd are too short as well, 2nd doesn't get to 100kmh! Because this is getting rather wordy, I give you a few charts:

Note that all evo 4-9 manual 5 speed's will have the longer 1st and 2nd, will have either the same 3rd and 4th as us, or a very slightly shortened 1.444 and 1.096 ratio (that don't really matter in real life) and they can have 4 different 5th gear ratios, 0.857, 0.825, 0.761, 0.720. Again note that the only ones with the longer 5th gear are the 5 speed EVO 7 and 8.

One of the NZ members Kenneth has the EVO A gearset in his car which I managed to procure from Ralliart NZ. It works perfectly fine and he didn't find the longer 1st and 2nd to be a problem with getting the car moving, even with his twin plate clutch. He also didn't notice much of a difference with the longer 5th gear unfortunately. And being perfectly honest, there isn't much of a difference anyway!

I went for a few passenger laps with an EVO 7 on the weekend, it had the longer 5th gear and the 1.03125 4th gear and the extra drop off from 4th to 5th was actually noticable when accelerating on the back straight compared to my car with the 0.761 5th gear. You wouldn't want to increase the 5th gear any more than 0.720 because the drop off in rev's would be too great. In saying that, how often do you accelerate hard in 4th up to 6000rpm (166kmh) where the acceleration in 5th gear would actually matter?

So the next option is increasing the final drive. Our stock ratio is 4.111 and EVO's are 4.529 which is going the wrong way. Unfortunately out of all of the cars worldwide which used our W5M51 gearbox, none had a final drive lower than ours.

However TeamRIP in the USA make a 3.73 ratio final drive for the EVO 5 speed, which will bolt straight into our cars. They talk about it here at the bottom of the page. http://www.teamrip.com/NEW_EVO_STAGE_3_TRANSMISSION.html

I was going to buy one of those but unfortunately the BMW came along and I don't have much spare money at the moment. This would change the gears significantly:

5th gear at 110kmh is now 2650rpm, a big drop from the stock 2930rpm. A further option for those looking to go to 300kmh or doing long journeys across the Nullabor is getting the 3.73 final and the 0.720 5th gear. This looks something like:

110kmh is now at 2510rpm.

Note that 1st and 2nd gear are now getting quite long. You can install the 0.720 5th gear onto the stock gears if you want, to give yourself the shorter 1st and 2nd with the long 5th. This will give you:

That is my personal preferred arrangement. Tracking down the 0.720 gears is next to impossible and the 3.73 final drive is very expensive, and you have to pull apart most of the engine bay to actually remove the gearbox and change things....but imho it is worth it! You can order the 0.720 from Mitsi, in NZ it was going to cost around $350 for the two gears.

 

[kiwibstokes]

Very intresting dude, i myself find that the gears are way too short as well, and sometimes find myself wanting a 6th gear or a lower rpm in 5th

 

[bradc]

Unfortunately the evo 6 speed is next to impossible to fit into the car

 

[SiliconAngel]

Which is pretty crap - why is it so difficult to get six speed manual gearboxes?? (and I don't mean for our cars, I mean why are so few made by manufacturers of all types?)

Great info there Brad! So you're saying just the 0.720 Evo 5th gear will set you back around $350? Just looked on the Teamrip site and they have the 3.73 final drive listed as USD$1100?

 

[Fred]

a sixth gear would be the best i recon, dunno why mitsi didn't have a 6 spd in a car with the engine it has got ...

 

[bradc]

the 0.720 will cost $350, the 3.73 is US$1100

 

[Guest]

Great read Brad! Cheers for that one mate!

Silly question: Will changing 5th gear ratio throw the speedo acuracy out?

 

[SupremeMoFo]

Silly question: Will changing 5th gear ratio throw the speedo acuracy out?

Nope, the speedo goes off driveshaft rotations basically. Changing the circumference of the tyres messes with the speedo though.

 

[bradc]

Exactly. You can change to whatever final drive and gear ratio you want and it won't matter.

Even if it did there are $40 kits from Jaycar over here that let you adjust the speedo by -+50%

 

[SiliconAngel]

there are $40 kits from Jaycar over here that let you adjust the speedo by -+50%

That's interesting, Brad - do you know what the model is? We have Jaycar in Australia too Once I get new shoes I intend to recalibrate using GPS, so a simple off-the-shelf adjustment device would be brilliant!

 

[SupremeMoFo]

It's probably this one Trevor - http://www.jaycar.com.au/productVie...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

 

[bradc]

yep, even the part number is the same!

 

[SiliconAngel]

Cool thanks guys - my lazy ass appreciates the effort today!

 

[bradc]

now lets get back on topic. Trev, are you interested in longer gear ratio's at all, or haven't you driven the car enough yet? (that isn't intended to be a cheap shot, but I can't figure out how to re-word it to make it sound polite!)

 

[Guest]

Very interesting, I went on a longer trip during Easter and I defeinately thought that I was just pouring money away.

Sitting right on boost may be good for overtaking but yeah I'd definately want a higher 5th or better still 6th if ever possible if country driving was to be more common.

 

[SiliconAngel]

now lets get back on topic. Trev, are you interested in longer gear ratio's at all, or haven't you driven the car enough yet? (that isn't intended to be a cheap shot, but I can't figure out how to re-word it to make it sound polite!)

Haha don't worry Brad, I wouldn't have taken it personally even without the disclaimer

Even though I was only in the car for three days total, I do quite a lot of driving in the course of a day, and yes a longer final drive and 0.720 fifth is definitely something I'm interested in - I actually convinced the g/f it'd be a good idea a couple of months ago (didn't take much convincing considering the cost of fuel these days). I like the low ratio for everything below 80, but once you're cruising at 100 on the freeway you definitely start wishing for an extra gear.

Having said that, I won't be in a position to do anything about it for a few months now, sadly

Hmm I wonder if it would be possible to get a machine shop to copy those gears...

 

[bradc]

I don't know about making ones up ourselves. I've been in touch with a guy in the states and it sounds like he is keen to swap his 3.73 with my 4.111 so we will see how that goes. He needs about 2 months though because he is currently waiting for a spare gearbox to be built up. I guess we might be waiting until then at the earliest

 

[Sydo]

Just thought I'd chime in and say - none of this is relevant to the drivers of tiptronics. *yawn*

See attached.

 

[SupremeMoFo]

Nice. But dude, clean your dashboard, haha!

 

[trounced]

if all we are worried about is sitting on boost is it possible to install a boost controller that also alows you to drop the boost off on one of the settings ?