gearing

[V8OWNER]

Just out of interest, a friends just emailed me this and I wondered how it compares to the
porsche box when mated to a chevy?
I guess i mean primarily the box ultima supply.. (seeing as my kits ordered now) but whatever you guys are using would be interesting!
cheers...

Bugatti Veryon:

1st gear - 100km/h (62.5)
2nd gear - 150km/h (93.7)
3rd gear - 200km/h (125)
4th gear - 250km/h (156)
5th gear - 310km/h (193)
6th gear - 360km/h (225)
7th gear - 406km/h (253)

[steve_d]

The speeds mean nothing without the revs.
Without the revs we cannot calc. back to the gear ratios.
There is a thread in FAQ sticky on gear ratios and some links to gear calculators.

Steve

Edited by steve_d on Tuesday 5th September 17:27

[V8OWNER]

oh ok cool i didnt see it.. ill take alook..
just interested cos' my rush has a completely pointless 1st gear....

[andygtt]

Veyron makes peek power at 6000rpm so I doubt it goes beyond 6500rpm.... peek torque is at 5500.

[steve_d]

As a rough guide the 0-100-0 only uses 1st and 2nd.

Steve

[lvjost]

Use the following formula for calculating the wished/optimal gear ratios.
speed (km/h) = [rpm*2.02]/(16.67*x*y)

2.02 is metres, approx. circumference of the supplied goodyear eagle F1s
x is the ratio of a gear, f.e. 31/41 = 0,756 = 5th gear of a G50 of the 911 turbo
y is the final drive ratio, f.e. 31/9 = 3,4444, the standard G50 (1988) final drive ratio

The 1988 G50 01 f.e. has
1st = 3,15
2nd = 2,509
3rd = 1,409
4th = 1,125
5th = 0,889

That means at max rpm f.e. 6500, you´ll reach 257,25 km/h max.....

Hope that helps..

[cmoody32]

steve_d said:

As a rough guide the 0-100-0 only uses 1st and 2nd.

Steve

If you are reffering to the Ultima world record, this is achieved starting in 2nd and using only 2nd and 3rd gears. Richard verified this to me on the phone.

[steve_d]

Sorry, thought it was 1 and 2.
I stand corrected.

Steve

[shithotfast]

if it helps it used to be 29 mph per 1,000 rpm in 5th of a g50.
So, 6,000 rpm gets you 174 mph, 7,000 203 mph. Does that sound right?

[GTWayne]

It always amazes me that folk will sell their granny to have a hoped up motor but are rarely prepared to spend money and optimise a gearbox. Building a motor that will turn 7K rpm + is awesome but will cost 8/12K minimum. Half of that spent on a sensible set of gear ratios + LSD and a more tame motor will get the same result with less stress on the motor. It is also worth bearing in mind that Elite are very close to releasing a box that is a direct replacement for the venerable G50 and you will be able to choose the gear ratios that you want.

[gtr-tt]

GTWayne said:

It always amazes me that folk will sell their granny to have a hoped up motor but are rarely prepared to spend money and optimise a gearbox. Building a motor that will turn 7K rpm + is awesome but will cost 8/12K minimum. Half of that spent on a sensible set of gear ratios + LSD and a more tame motor will get the same result with less stress on the motor. It is also worth bearing in mind that Elite are very close to releasing a box that is a direct replacement for the venerable G50 and you will be able to choose the gear ratios that you want.

I can tell you why... You end up with a 140mph top speed...

[GTWayne]

gtr-tt said:

GTWayne said:

It always amazes me that folk will sell their granny to have a hoped up motor but are rarely prepared to spend money and optimise a gearbox. Building a motor that will turn 7K rpm + is awesome but will cost 8/12K minimum. Half of that spent on a sensible set of gear ratios + LSD and a more tame motor will get the same result with less stress on the motor. It is also worth bearing in mind that Elite are very close to releasing a box that is a direct replacement for the venerable G50 and you will be able to choose the gear ratios that you want.

I can tell you why... You end up with a 140mph top speed...

Explain yourself, I don't understand what you mean?

[p15ton]

Gearing will get you more out of one of these cars than a ton of horsepower will (and I can't sell you a gearbox!)

[gtr-tt]

GTWayne said:

Explain yourself, I don't understand what you mean?

If you shall use gearing that makes the car perform it's best with a "low" power engine you will need tight gearing. This will result in two alternatives. Either gear it for high speed and you end up with a very tall first and close 2-5 or you gear the car for perfect acceleration and then you will end up with hitting the rpm limit at around 140-160 mph.

To compensate both of the above (nice 1st gear and comfortable rpm at hight speed) you need more power in a broader rpm range.

I only have four gears bit since my turbos help so much in the low end and I rev so high I have a great "area under curve" hp-figure and this makes it work even whith my rugged old transaxle.

This said, a perfectly matched gearbox would ofcourse make it even faster.

[peterpsg]

GTWayne said:

It always amazes me that folk will sell their granny to have a hoped up motor but are rarely prepared to spend money and optimise a gearbox.

I couldn't agree more... it's just of like hooking up a huge car stereo without upgrading the electrics to cope..

GTWayne said:

It is also worth bearing in mind that Elite are very close to releasing a box that is a direct replacement for the venerable G50 and you will be able to choose the gear ratios that you want.

But for what price?

Most builders like the G50 as it only costs ~1.5k, if you want to spend 5-7 you can get a 993/996 box... etc etc

Unless it's around the 3-4 mark, most people will stick with the G50...

[GTWayne]

peterpsg said:

But for what price?

Most builders like the G50 as it only costs ~1.5k, if you want to spend 5-7 you can get a 993/996 box... etc etc

Unless it's around the 3-4 mark, most people will stick with the G50...

I know everything has a price, but myself, I will go without until funds permit so as to get the job done the way I want. I am not suggesting that money may be saved to achieve your gearbox goal, just saying that it is an often overlooked tuning medium with some other possible alternatives.

[therighthand]

Hi guys,

I am slowly looking into my Ultima project and had actually been wondering why noone has used any of Xtrac's street boxes.... They make many setups and you choose gear ratios. Any enlightenment would be helpfull.