Please explain the differences in the G50 box

[V8Dom]

UltimaCH said:

V8Dom said:

Glad it helped...

To me that is what the forum is all about, helping others and getting to know fellow ultima people..

I found it interesting the changes tyre diameter make ... 8mm new tread against 2mm worn tyres was a 1/2 inch difference and 5mph at the top end...5mph is 5 mph.. Id like to know if tyre growth happens at that speed as well or tyre squat (bulg in the tyre) but only as a matter of interest rather than being dull...

1mph factor??? you did well ... you know as the tyre measurement will make the difference, there could be your 1mph.

Dom

Centrifugal force being what it is, I imagine that at high wheel rotation, the tyre will expand outwards making a bigger overall circumference. Look what happens when a dragster spins the wheels to get some heat in the tyre. It expands like crazy, but then the side walls are also taller than our sports and low profile tyres.

and the sidewalls on a dragster are very soft...They are not supposed to arround corners!!!!!!!...

but yes you are correct there must be some growth in the centre as Ive found in the past close mudguards or race bikes get worn as speed increases...

Dom

[GTRCLIVE]

Running 28.5" Enzo rears on my car, and Bridgestone made them lighter just for Ferrari.... Nice of them to spend all that money to develop a tire for my car....

[V8Dom]

GTRCLIVE said:

Running 28.5" Enzo rears on my car, and Bridgestone made them lighter just for Ferrari.... Nice of them to spend all that money to develop a tire for my car....

Will that make it slower as well Clive?

Dom

[andygtt]

GTRCLIVE said:

Running 28.5" Enzo rears on my car, and Bridgestone made them lighter just for Ferrari.... Nice of them to spend all that money to develop a tire for my car....

you just copied me lol

[andygtt]

V8Dom said:

UltimaCH said:

V8Dom said:

Glad it helped...

To me that is what the forum is all about, helping others and getting to know fellow ultima people..

I found it interesting the changes tyre diameter make ... 8mm new tread against 2mm worn tyres was a 1/2 inch difference and 5mph at the top end...5mph is 5 mph.. Id like to know if tyre growth happens at that speed as well or tyre squat (bulg in the tyre) but only as a matter of interest rather than being dull...

1mph factor??? you did well ... you know as the tyre measurement will make the difference, there could be your 1mph.

Dom

Centrifugal force being what it is, I imagine that at high wheel rotation, the tyre will expand outwards making a bigger overall circumference. Look what happens when a dragster spins the wheels to get some heat in the tyre. It expands like crazy, but then the side walls are also taller than our sports and low profile tyres.

and the sidewalls on a dragster are very soft...They are not supposed to arround corners!!!!!!!...

but yes you are correct there must be some growth in the centre as Ive found in the past close mudguards or race bikes get worn as speed increases...

Dom

car gets heavier at speed due to downforce, so i suspect only expansion will be in the non contact areas of the tyre thus have no effect on rotation distance.

[RXHeven]

Tire slippage is also a factor reducing all your calculated numbers by roughly 1%-4%.

[V8Dom]

RXHeven said:

Tire slippage is also a factor reducing all your calculated numbers by roughly 1%-4%.

IMO Tyre slippage will only come into play in the first 3 gears under max acceleration and that wont effect gearing!! You gear a car so you can pull cleanly through the gears in the most efficient way... (example hold it at 6500 rpm in 2nd gear and there wont be any tyre slippage as you are not accerating)

4th and 5th wont have tyre slippage at high speed due to downforce and high gearing unless you are pulling 1000-1200 hp plus and at that horsepower does really matter what gear you are in your going to leave black lines anyway.

The choice of gearing on the ultima isnt based on wheelspin but being able to drive the car.. Wheel spin in a fun factor..

So for that reason I would even consider wheel spin when calculating gear box ratios.

Dom

Edited by V8Dom on Thursday 4th March 18:59

[spatz]

not sure if you are right..... there is a slippage as the wind resistance is so big at high velocities and the tyres are pulling hard against these forces, been told that this is also the reason why the tyres are suffering a lot at high speeds.

[RXHeven]

There is always variable amounts of tire slippage at all speeds under all loads, generally in the ballpark of the figures I posted above when not experiencing excessive tire spin. The better gear ratio calculators will allow you to accomodate for this by setting the tire slippage variable and even make it dependant upon torque multiplication under various throttle applications given the engines dyno graph.

The above reply is also correct regarding slippage and aero load.

[V8Dom]

RXHeven said:

There is always variable amounts of tire slippage at all speeds under all loads, generally in the ballpark of the figures I posted above when not experiencing excessive tire spin. The better gear ratio calculators will allow you to accomodate for this by setting the tire slippage variable and even make it dependant upon torque multiplication under various throttle applications given the engines dyno graph.

The above reply is also correct regarding slippage and aero load.

well i did not know that and always have an open mind, as you learn something new everyday...Thanks for info..

Dom

[Jp ultima]

[quote=spatz]ok we have now two very nice XLS sheets thanks to Dominique and Paul,
I figure I need my LS7 rev up to 6800 and then I am flying the 200mph, so if I cannot reach the revs, I know I am not there.......

i have decided on an ls7 for my build,and though i will probably never get there, i still want a gearbox that allows it to do 200mph but with 6 gears and preferably LSD. any suggestions?

[spatz]

why do you want 6 gears if 4 are already enough ? Installing a longer 5th gear in the porsche G50 is a matter of 1 hour if you have right tools. I have been watching the mechanic when he changed my 5th gear to 0,756. I would not recommend any longer because the drop from 4th to 5th would be too big and you would need to change the 4th gear as well.

Edited by spatz on Tuesday 23 November 07:56

[GTRCLIVE]

I have raise my 1st gear and the CWP ratio so that all the gearing has gone up. Get a over 200 5th and 230ish 6th. But it isn't cheap......CWP is $3000 before fitting...

[GarethGTR]

spatz said:

why do you want 6 gears if 4 are already enough ? Installing a longer 5th gear in the porsche G50 is a matter of 1 hour if you have right tools. I have been watching the mechanic when he changed my 5th gear to 0,756. I would not recommend any longer because the drop from 4th to 5th would be too big and you would need to change the 4th gear as well.

Edited by spatz on Tuesday 23 November 07:56

Hi

Surely the reason that you would want more than four gears is precisely that you can get the tall gearing without 'dropping' too many rpm?

Gareth

[738 driver]

So much and such a wide spread of torque..particularly if you select a good LS motor, that those extra gears are not required.

Why have more weight/dumbell effect, hanging out the rear ?
A short, stubby and tough box is all that's really required

[GarethGTR]

Hi

Okay...

I am using an LS7 and have a 993 Turbo box (6 speed G50/21)

Gareth

[Gulf LS3]

GarethGTR said:

spatz said:

why do you want 6 gears if 4 are already enough ? Installing a longer 5th gear in the porsche G50 is a matter of 1 hour if you have right tools. I have been watching the mechanic when he changed my 5th gear to 0,756. I would not recommend any longer because the drop from 4th to 5th would be too big and you would need to change the 4th gear as well.

Edited by spatz on Tuesday 23 November 07:56

Hi

Surely the reason that you would want more than four gears is precisely that you can get the tall gearing without 'dropping' too many rpm?

Gareth

Sbc's and LS engines have so much torque one gear would do!! You are just slowing down and wastig time changing gears,

90 mph first gear
250mph top gear

then fill in the gaps with 2 or 3 cogs

[spatz]

GarethGTR said:

spatz said:

why do you want 6 gears if 4 are already enough ? Installing a longer 5th gear in the porsche G50 is a matter of 1 hour if you have right tools. I have been watching the mechanic when he changed my 5th gear to 0,756. I would not recommend any longer because the drop from 4th to 5th would be too big and you would need to change the 4th gear as well.

Edited by spatz on Tuesday 23 November 07:56

Hi

Surely the reason that you would want more than four gears is precisely that you can get the tall gearing without 'dropping' too many rpm?

Gareth

If you rethink you will agree that the number of gears has nothing to do with the drop when changing them

[GarethGTR]

spatz said:

GarethGTR said:

spatz said:

why do you want 6 gears if 4 are already enough ? Installing a longer 5th gear in the porsche G50 is a matter of 1 hour if you have right tools. I have been watching the mechanic when he changed my 5th gear to 0,756. I would not recommend any longer because the drop from 4th to 5th would be too big and you would need to change the 4th gear as well.

Edited by spatz on Tuesday 23 November 07:56

Hi

Surely the reason that you would want more than four gears is precisely that you can get the tall gearing without 'dropping' too many rpm?

Gareth

If you rethink you will agree that the number of gears has nothing to do with the drop when changing them

Hi

The closer the ratio's the less of a drop, the more gears the closer the ratio's

I understand that you are saying that you could get away with four gears, but the more the gears the better, all depends on driving style, end use and ratio's. More gears gives you more choice.
If you want you can have a box setup so that you can motorway way cruise at very low RPM and yet still have a selection of ratio's available for more spirited driving.

F1 cars have 7 gears, All modern high power/performance cars have 6 or more gears.

[738 driver]

F1 engines have very short strokes (long levers/long strokes produce torque).....they are high power, high revving units but comparatively very low torque in a very narrow power band, hence the many gears, similar to a motorcycle engine/box . These V8's in light cars do not need the same multiples of gears.
The easy way is to stick with 5 and upgrade 5th...however if you have the coin a custom built box with a fairly tall 1st and close through the rest would be the way to go. 1st gear in most V8-porsche combos is only used for parking...its pretty useless when giving these cars the beans.....So theres one you can do without for starters !!!