Gearing Calculations

[neal1980]

Im after a bit of help as Im getting some crazy numbers with my gearing.

I am building an LS Turbo engine to produce 700-750bhp, I am looking at gearbox options and have 2 options at present. I will be running 18" tyres.

I have a selection of diffs to pick from but want to try and crack sixty in first maybe. My first option was to use a 2.88.

T56 ratios 2.66, 1.78, 1.30, 1.00, 0.74, 0.50
TKO600 ratios 2.87, 1.89, 1.28, 1.00, 0.64

Can anyone work out my speeds please its driving me nuts..Anyone have experience of the TKO600 v's T56?? car will weight approx 1200kg absolute max.

Many Thanks

Neal

[TheEnd]

http://www.endtuning.com/gearratios.html

It's set up for BMWs, but you can change anything.

Start with the tyre size, try a gear box ratio set, and you can alter the diff ratio and work out the speeds in each gear.

[neal1980]

I can do 300mph + what the hell am I doing wrong here lol

[TheEnd]

you might need to select the gear, that's probably a 5th or 6th gear speed with a low diff.

What are your tyre sizes?

[stevieturbo]

There are literally dozens of gear ratio and other calculators online. It really isnt difficult.

http://www.gearboxman.co.uk/inforatios.html

[Brummmie]

mine does just over 60 in first, tko600 with 3.08 diff, 6th in the t56 is just a cruise gear, i am at around 7200-7300rpm, with 202vmax on 265/35-18 tyres.
You probably wont be able to hit those revs with the turbo's? well not making decent power, i would say 2.9ish will be good for you.
2.9 would be my ultimate for top speed and my power, around 218mph.

[stevieturbo]

Brummmie said:

mine does just over 60 in first, tko600 with 3.08 diff, 6th in the t56 is just a cruise gear, i am at around 7200-7300rpm, with 202vmax on 265/35-18 tyres.
You probably wont be able to hit those revs with the turbo's? well not making decent power, i would say 2.9ish will be good for you.
2.9 would be my ultimate for top speed and my power, around 218mph.

Turbos will have no negative impact on rpm's. If anything, they will help.

[GavinPearson]

We really need to know the tyre size and the rpm at which peak power will be developed.

I would use the TR6060 transmission of the two - it's got a reputation for surviving very hard use in some of the most powerful road cars available.

[stevieturbo]

GavinPearson said:

I would use the TR6060 transmission of the two - it's got a reputation for surviving very hard use in some of the most powerful road cars available.

As have the T56 and TKO600.

But depending on application, the TKO being only a 5 speed is physically smaller, so much better suited to cars where space is an issue.
I think there are two sets of ratio's available on the 600 too ?

The TR6060 is relatively new, so it's reputation is also new too, but it is deemed to be a stronger box than the T56.
But the T56 has been used in Vipers making 1700bhp with success, so it is clearly very very strong.
Any reliability problems people have had ( which oddly seem more common on the Aussie Monaro platform ) are not down to a lack of ability to hold power.
And same with the T56, the 6060 comes in various fitments and ratios. So who knows if they will all be stronger than the T56

It all depends which can physically fit the easiest. All options are very good and strong with similar ratios available.

[Brummmie]

Neal, DO NOT get the high ratio 5th TKO, i started with that and it was awful.

[NormanD]

neal1980 said:

Im after a bit of help as Im getting some crazy numbers with my gearing.

I am building an LS Turbo engine to produce 700-750bhp, I am looking at gearbox options and have 2 options at present. I will be running 18" tyres.

I have a selection of diffs to pick from but want to try and crack sixty in first maybe. My first option was to use a 2.88.

T56 ratios 2.66, 1.78, 1.30, 1.00, 0.74, 0.50
TKO600 ratios 2.87, 1.89, 1.28, 1.00, 0.64

Can anyone work out my speeds please its driving me nuts..Anyone have experience of the TKO600 v's T56?? car will weight approx 1200kg absolute max.

Many Thanks

Neal

Neal

I've been playing arround with gearboxes and ratios for getting a manual gearbox in my Jaguar XKR

Like yu it has 18" wheels but with a 3.06 diff

I'm usuing a Tremec T56 but there new Magnum, that is classes as taking 750+ Horses

I am now an official Importer for the Tremec gearboxes and can also get the gear ratios changed before importing

Maybe give me a call

[scarble]

neal1980 said:

I can do 300mph + what the hell am I doing wrong here lol

Just because you're geared for it doesn't mean you'll reach it. Where is your rev limiter? It's a simple sum from there.

[Stan Weiss]

Calculating 300 MPH from gear ratio, tire diameter, engine RPM is fun.

Where it gets interesting is calculating the aerodynamic HP loss at a given MPH. Let use 300 MPH, a Coefficient of Drag (CD) of 0.32, a frontal area of 17 sq. ft. (1.57935 Sq. M), and standard air density. It will only take around 1000 RWHP just to push the vehicle through the air.

Stan

[GavinPearson]

Before you go choosing a gearbox I suggest you try to get a good idea of the torque curve that the engine will produce and generate a net wheel torque curve with the gearing options that come from a gearbox with a suitable torque capacity and a suitable selection of final drive ratios.

This should help avoid having gears that are too low, or too high.

[Stan Weiss]

What is your max torque @ RPM and max Hp @ RPM also what rear gear ratio will you run and what is your rear tire diameter? What is your Coefficient of Drag (CD) and frontal area?

I can generate a torque / HP curve and produce one of those for each of the trans.

Stan