Gear Ration Spreadsheet

Started by LukeC, October 16, 2014, 06:38:30 PM

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LukeC

Someone else will have to chime in. t depends on your application.

I have niether done it myself or driven one. Vin Sharp at pace will be more than glad to talk to you about it.
Luke Clayton

qvae.com.au

John A Pucak

The gear ratios in my group s race car are
1.  2.875
2.  1.72
3.  1.25
4.  1.04
5.   .88
Good for 206 kph.


Paul Newby

PTP, I started out with a standard Twin Spark box. With the 4.1 final drive and the 0.79 fifth gear I would only get into fifth gear after the start finish line at Phillip Island! It was pretty much useless.

My box has 1st and 2nd ratio from the Twin Spark box, 3rd and 4th from an early Alfetta box I had lying around and 5th gear is actually the Twin Spark 4th gear, which Vin machined on. The 4.3 diff came out an early South African Alfetta 1.6 but I'm pretty sure that 1.8 Giuliettas and I think late 2.0 GTVs had the 4.3 diff as standard. Now 5th gear is a lot more usable.

This is probably the ultimate affordable solution. I understand you can source Colotti straight cut close ratio gearsets from Italy but they are mega expensive.
1974 2000 GT Veloce (Le Mans Blue) - Restoration project
1975 Alfetta GT (Periwinkle Blue Metallic) - Group S racer - Sold!
2009 147 Monza 3Dr (Kyalami Black) - Don't ask!
2010 VW Passat R36 Wagon (Biscay Blue) - Daily Driver
2015 VW Golf GTI Performance (Night Blue) - Wife's Runabout

PTP

Yeah, mine has 4.3s, which mean around 6000-6500rpm in 5th at the end of the straight at PI (I think, I was busy looking through the apex, not at the tacho), which is pretty good. A slightly shorter 5th with the rest the same ratios would be ok, but taller first and second, and shorter 5th would be best. But worth $6K plus? Doubt it.

PTP

Quote from: John A Pucak on March 13, 2016, 09:52:20 PM
The gear ratios in my group s race car are
1.  2.875
2.  1.72
3.  1.25
4.  1.04
5.   .88
Good for 206 kph.

I can find the origins of 1-3, but are 4 & 5 custom gears?

carlo rossi

are all isostatic ratios the same or did this change as well
current cars
red 83 gtv 2.0


previous cars
Red 76 1.2/1.5 alfasud ti
white 79 alfetta 2000
alfetta 74 1.8
escort Lotus twin cam
bikes
ducati 900 ss 1979
moto morini 3 1/2 sport 1975/6
Moto morini 3 1/2 valentini speciale 77 oh and a deltek rockhopper

John A Pucak

Gear set
3rd late series Alfetta
4th early series Alfetta
5th .88 Billett

PTP

That's a cool idea. Would be better still if it was also welded.

Duk

Quote from: PTP on April 07, 2016, 11:30:47 AM
That's a cool idea. Would be better still if it was also welded.

You'd want to seriously know what you're doing to weld heat treated/heat treatable alloy steel and expect it to continue doing a job like this.
Assuming that the welding process didn't cause distortion in the part, which it would, a welded area has to be considered as a cast area. So any forging process that has gone into the parent metal is ultimately undone. Shot peening after welding would be a good idea, but can't replicate the effects of proper forging.
The Daily: Jumped Up Taxi (BF F6 Typhoon). Oh the torque! ;)
The Slightly More Imediate Project: Supercharged Toyota MR2.
The Long Standing Conundrum: 1990 75 V6 (Potenziata)............. What to do, what to do???

PTP

To be honest, the 3rd to 4th gear ratio spread isn't really the issue with these cars. It's the 1st and 2nd ratios, and for racing probably the 5th gear too.

Bjurman

Quote from: PTP on April 07, 2016, 04:10:47 PM
To be honest, the 3rd to 4th gear ratio spread isn't really the issue with these cars. It's the 1st and 2nd ratios, and for racing probably the 5th gear too.


Hi  Here in Sweden we race some with the 116 gearbox..

The problem we got is that the 5th gear is to long..
so I do use to take the
3 gear from the early  Alfetta 1:35  and the
4th gear from  Bacci Romano 1:15
the stock 4th  in 5th       0:94 or the Alfetta 4th 1:02

Weldin is not any problem ..
/ Hans