Sonic Boom

iTrader: (11)

I'm still on a standard T5 and i'm amazed it's held together this long as since i've bought my 3 Door in 2003 all i've done to it is change the clutch a few times and changed the fluid twice.

But now with 550bhp and 531 ft/lb of torqure i'm sure it's just a matter of time before it poo's itself.

I'm doing the Midland Hillclimb Championship next year so along with a Supra Diff conversion I want do upgrade the gearbox too.

I've been looking at the Gearboxman T5 gearsets which are made by Quaife pretty sure i'm going to get one beginning of next year, but do I go normal ratio or close ratio?

Doing Hillclimbing close ratio would surely be the best?
I've put the figure into a gear speed calculator and even with my 3.9 diff would still give me a top speed of 164mph which is plenty.
I before any top speed boys tell me 164mph is probably not obtainable i'd be happy with 150mph as i'd never need to cross the line at over 130mph anyways.

It's not mega close ratio 4th is still 1:1 just seems to bring 1st to 3rd abit closer which would be ideal.

Opinions welcomed.
Cheers Rich

Sonic Boom

iTrader: (11)

Anyone?
Rich

Paul_RS

iTrader: (4)

Close ratio probably makes sense - If you can actually put the power down with it?

black_jack

I think you need to look at the power/ torque characteristicts of the engine and the use/ speeds the car will be used for, close ratio boxes often have a high 1st, so may be slower off the line, an engine with a very wide torque/ power curve may be quicker with the std ratio box (once the time lost changing gears/ lag etc is factored in)

ideally you want to make charts with the speed/ revs in each gear/ on upshift etc to see the difference

Having said that, on balance you are probably better off with the close ratio box for hilcliming as a road box probably has poorly chosen ratios for hilclimb use

if the car is to be used purely for hilclimb use it sounds like you could lower the final drive a bit more so its flat out in top or 4th etc on the longest straight

have you any data from any runs?

Sonic Boom

iTrader: (11)

This was my first year in competition and I have no data logging facility.

Here are my results from Prescott with a break down of times and speeds in certain sections:
http://www.resultsman.co.uk/?Q=2&Name=Richard+Brant
My best result was the last of the season on new 888's thou the track was alittle damp even on the last run

But next year i'll also be running at Shesley Walsh and Loton Park

Here's my Power vs Torque graph too:


Here's also a copy of the gear speed calculator with the close ratio gears.
Although I will more than likely be running 255/40/17 888 rears next year:


The car is in a road legal class so I do drive it to events and at the weekend, but it's all how it performs on the track than the road.

Rich

Paul500+

iTrader: (1)

just out of intrest whats your engine and turbo spec
im in the middle of a 500+ engine build

Sonic Boom

iTrader: (11)

CGI 200 Block
10 Long Studs
Nikasil Wet Liners
Cosworth Racing Short Skirt Pistons
Cosworth WRC Long Rods
Mountune/Cosworth Crank
Oil Spray Jets
Wide Wing Sump with a Blue Sprint Sump Baffle
Big Port Head 27mm Inlet 27mm Exhaust
Danny's own Inlet cam (More lift than a BD16+)
Standard Exhaust Cam
Hart Inlet
Tubular Manifold
GTX3076r with Tial .82 SS V-Band Exhaust Housing
100mm Airtec Intercooler
L8 ECU with Wasted Spark and WRC Cam Trigger
Ryan @ Car Looms UK full rubber coated engine loom



Rich

Madgit

Maybe ask Chip Rich, he's good at these calculations. Problem I think you've got is the variation on hills. The finish line at Shelsley for example is good for some high speed. There's probably other occassions where you might need a tall second gear rather than first.

Sonic Boom

iTrader: (11)

I crossed the line at Curbourgh at 102mph I think Shelsley finish straight is margainly longer so I think 110mph maybe 115mph over the line there so i'd be in 4th with either a close ratio or normal ratio.
Rich

Madgit

Wish I had the answer mate, I'm just firing over things for you to consider. Suppose it might be better to think about it after next season. Then you can weigh up the situation better when you know over more hills if you're gearing was off and where. A lottery win would be ideal, then you could have a set for each hill!

Sonic Boom

iTrader: (11)

I really need to change the box before the season starts or I risk it shitting itself at a meeting.
Rich

Madgit

Oh

markk

iTrader: (2)

Your sprinting is like our stage rallying, the answer is yes, you would not lok back, as long as the box you buy is a good one. But ratio wise, do it.

black_jack

Looking at the power graph, the power drops off above about 7200, if this is accurate (is it?) the shift point should be set (on the gear chart and in "real life" at 7200rpm), this will change the top speed to about 150mph in 5th, the close ratio 'box looks good, with nicely spaced ratios,(apart from 2nd being a bit high), so if i were you i would opt for the close ratio 'box, the power band on your engine is much narrower than i expected, it has a lot of power and torque over a relatively narrow band, even with the close ratio box, i recon it could drop out of the power changing from 1st to 2nd, a more progressive power curve with the power coming in below 5,800 might make it more drivable and potentially quicker on the track, especially in the wet

if the change points, are changed from 7600rpm to 7200, then, 50 will be in 1st, 80 in 2nd,100 in 3rd,130 in 4th ,150 in 5th, if 2nd was lowered untill it did about 75 at 7200rpm, it would be less liable to drop out of the power from 1st to 2nd, and will not drop out of the power 2nd to 3rd, in fact right at about the peak torque (so overall the car will accelerate quicker)

the final drive would be set much lower to get a really quick time, you could set it to be redlined ("redline" = 7200) in top (or 4th, and only use 5th for the road) (with a couple of hundred rpm to spare) on the longest straight of the fastest track you are liable to be competing on, (i recon this would be a good overall compromise) this would make the gearing much lower, and the ratios closer the tractive effort would be further increased, and the acceleraion, but also the torque from the torque multiplier would also be increased, i mean gearbox

you can use a video camera with a view of all the gauges as a basic "data logger"

ive never been involved with hillclimbs but i would imagine roadholding/ handling (and traction) plays a big part - have you done your corner weights?

i remember seeing a video of a kart on a "demonstration run" (not officialy in any class ) - its time would have beaten every car apart from the winning 1000+Hp 600kgs modified old F1 car in an open class, the kart had less than 80Hp!

What a beast of a machine - DR jeckle below 4.8k and Mr Hyde above!

DAN-Saff

I think dingy had gear change issues with his close ratio box.

JonnyBravo

Definitely go close ratio, like going to the 3.9 its a huge improvement, sadly though I probably wouldn't use a Quaife box, certainly not at that power, maybe a sequential but your into another league of money then.

Rsmat

iTrader: (2)

I stayed standard ratio with my gear kit... But maybe for hill climbing closet might be better for you mate .