Gear ratios

[MarkMc]

Got a new gear box fitted and just wanted to know how the ratios compared to a close ratio(dakar box) because they now seem a hell of a lot closer together(3,4,5). Which is heap better for 3rd and 4th gear response on road, just wondering how it will go over the QTR.

OLD
3rd gear sit on 162kmh at 8000rpm
4th gear sits on 213kph at 8000rpm
5th gear sits on 250kph at 8000 rpm.(not sure this one)


NEW
3rd gear sit on 137 kmh at 8000rpm
4th gear sits on 172 kph at 8000rpm
5th gear sits on 228 kph at 8000 rpm.

Before I used to hold 4 th across the QTR at 178 kph, 12.6. Now I will need 5th. any one used ratios like this for the QTR. :?:

 

[skiddusmarkus]

Looks like your new ratios are very similar to a Dakar box,albeit with 500rpm more to play with.Fastguy has run his on the 1/4 and got a flat 13secs at just over 100mph so I presume he was getting to the top of 4th.

 

[Fast Guy]

My 4th seems to run out somewhere over 80. I was doing 6000rpm in 5th when I go over the line

 

[MarkMc]

I think I may have got the 3rd and 4th may be a little wrong it seems to be more like

3rd gear 130 kph at 8000rpm
4th gear 180 kph at 8000rpm

I was crossing the line in 4 th before at 178 kph. So I m hoping the car will get to 180 kph alot faster then before. It sure feels like it will.

My 4th will pull to about 112 mph

My 3rd will pull to about 80 mph

Did you mean your 3rd will go to 80 mph.

 

[skiddusmarkus]

What box is it and did you specify your own ratios?

 

[MarkMc]

Modena box. I didn’t specify ratios, but I asked them about changing 3rd and 4th , because I thought they were a bit high for the QTR. They said the R had good ratios so probably not worth it.

Then they put custom ratios in the Modena box(to suit engine power) for optimum QTR times. The new lower gears feel good and it now screams from 80 to 120 kph in 3rd. I’m happy with the new box. The car feels a lot faster now. Just I haven’t heard of anyone changing the ratios like this.

The new ratios are a fair bit different from standard and just wondering if anyone has changed there ratios like this and what was the result like over the QTR :?: . I was thinking with all the people with Rs surely someone has changed the ratios round especially when you consider the number that go for up rated boxes and rebuilds .

 

[skiddusmarkus]

I've got custom ratios in mine but didn't really get chance to test them properly before my engine died.3rd=90mph(145kmh),4th-115mph(185kmh) and 5th-145mph(233kmh) all at 7500rpm but I'm having the limit raised to 8000rpm now so will see about 7% more in each gear than before.

 

[Fast Guy]

The new lower gears feel good and it now screams from 80 to 120 kph in 3rd. .

I timed mine from 50-70mph (80-112kph) in 3rd once, it came up at 1.7secs :shock: on my stopwatch. (not 100% accurate but a fair guide)

 

[cmng]

modena box ?

how we know it is modena box ?

 

[MarkMc]

I don’t know what time it takes to do 80 to 120, probably more than 1.7s for me , but it feels a lot faster then before. But the tuners will turn up the boost when its done another 500km(run in) so should be faster soon .
Some gear box people I have talked to have suggested wider ratios are the go, but they were talking about much more powerful cars and suggested lower ratios will cut quick ET’s but have lower terminal speeds.
I think the receipt says modena from the tuner so that’s what they put in I think. I looked at another box and they suggested the Modena was pretty reliable and strong so that’s what was put in. The box has the internal factory parts replaced with stronger billet parts.(they said).
I thought it was one of the other types PPG :? (phitzem, something like that but it isn’t). Goes good too bit clunky, but very direct in action and response.
I guess I will find out in 500km if lower ratios will improve QTR times. The car sure feel faster between 100 and 180kph only time will tell if the extra gears change to fifth is worth it.

 

[antilag]

i wudent like to hit 5th on the qtr mile to be honest another gear change+a little lag added wen not necessary?didnt that phil cavanagh have the nismo box and was hitting 5th rite near the line costing him alot of wasted time on the strip id rather scream across at 130mph in 4th personally

 

[MarkMc]

I've got custom ratios in mine but didn't really get chance to test them properly before my engine died.3rd=90mph(145kmh),4th-115mph(185kmh) and 5th-145mph(233kmh) all at 7500rpm but I'm having the limit raised to 8000rpm now so will see about 7% more in each gear than before.

How did you come up with your ratios. Did you use some sort of formulae. Or is it more guess work. I know I have said this before but 3rd and 4th feel a bit to tall but this just a guess(seat of my pants feel of the car). Hows your engine now is it rebuilt or in the process?

Anti lag
I’m hopping for another 20 to 30 kw at the wheels when the motors running in, which should push the terminal speed a fair bit over 180 kph(now 178) and make use of that fifth gear. The new fifth gear is not a lot taller then fourth and it changes from fourth to fifth pretty quick.(I hope)

 

[antilag]

sounds good mate put its still a gear change and they never gain u time do they

 

[skiddusmarkus]

How did you come up with your ratios. Did you use some sort of formulae. Or is it more guess work. I know I have said this before but 3rd and 4th feel a bit to tall but this just a guess(seat of my pants feel of the car). Hows your engine now is it rebuilt or in the process?

I went for ratios in between the standard and Dakar box for a nice compromise.It works out about 10% less than standard in 3rd,4th&5th so I figured this would give me around 10% more power at the wheels.
When I chose them I wasn't planning on rebuilding the engine,so chose ones that would suit the standard engine better.I also pi**ed about on GT2(lost my copy of GT) with gear ratios on the closest car I could find to the R(WRX),sounds daft but it's quite an accurate simulator.
If I'd known the engine was going to go,I'd have maybe gone slightly longer with the ratios,hence me wanting to up the limiter by 500rpm to compensate.
My engine is almost done,being held up valve shims for new cams.I don't mind too much though as the delay has woorked out ok as I have managed to get hold of a front and centre Nismo LSD to go in the box which will help a lot with launching and handling.

 

[MarkMc]

Very scientific GT2. I like it :lol: . i wonder if this is how they figured mine out. I can see the mechanics now sitting around the play station. its my turn. No its mine.
Nisom LSD sounds good , bet that will improve the front end grip heaps.
Thats some thing I should have asked about when they did the box :? . oh well next time . I think they said me diff is straight cut now. It howls a bit.