Gearing

[Guest Daz]

I was thinking about gearing ratios the other day while I was out driving the diesel family car. The Hood sits at 70 at around 3000 revs, give or take a little bit, while all diesels I have ever driven normally cruise at 70 at around 2300 rpm. With same size tyres there must be a difference in the gearing of the gearbox or diff. I am assuming, therefore, that Sierra diesels have similar drive ratios, but where are the differences to the petrol variants? Anyone got the figures for different gearboxes and diffs for the Sierra range?

 

As I was driving around I was just thinking how easy the Hood revs up to 6000 rpm and was wondering: if the diesel car sits at 70 at only 2300 rpm, how fast would it actually get go if the engine revved up to 6000 rpm. OK, the 0-60 may suffer, but with a high torque towing cam (Kent FR30) fitted it would hardly be noticeable and the top end would be better. At the moment, despite any modifications done to reduce the 0-60 time, the gearing is still as per the standard 2.0GL and tops out at about 115mph (or so I am led to believe )

 

Would it be worthwhile swapping out the offending article and fitting a higher geared item instead? Has anyone done it?

 

Daz

[Bob Tucker]

Hi Daz,

the diesel has far more torque at lower revs than any

Sierra petrol engine, & a Sierra is much more aerodynamic

than our bricks. Also dont forget that raising the overall

ratio increases the effective gaps between gears, which

will muck up your acceleration even more.

Unless you plan to tour on the autobahns, think about

raising the ratio to 3.92.

Mine now sits at 3500 at 70 in 5th (still pretty comfortable),

but accelerates much better than with a 3.62,

feels like a close ratio box,

and still tops out at 120, (in Germany!) pulling 6000 in 5th.

If you're at Detling, look me up for a demo.

 

PS Re diesels can I heartily recommend SUPERCHIPS.

I've just re-chipped my C5 2.2 turbo diesel. Its taken the hp

from 133 to 168 (rolling road tested before & after) & increased torque

by 35% from 2000 to 5000 rpm. It's now a real sleeper!

Cheers, Bob.

[Guest DaveB]

Hi Bob

 

Can you let me have more info on chipping the C5 please

 

Dave

[Guest Angel Boy]

Dave,

Have a look here as a start:

 

Superchips

 

Have been contemplating it myself on my Ibiza diesel. 130 to 150 sounds a good increase for 300 notes.

 

Andy

[Bob Tucker]

Hi Dave,

I got it fitted at SANSPEED in Bexleyheath, but there

are quite a few fitting centres all over the UK

 

http://www.sanspeed.co.uk/Default.asp

 

Superchip seem to have a standard price across most ranges.

I paid £499...much cheaper per HP than tuning the Hood, & they

threw in the rolling road session.

They were as interested to see the results as I was!

 

The change is amazing, the engine is smoother, pulls from lower in the rev range

and amazingly gives better MPG.

Cheers, Bob

[Guest DaveB]

Thanks for info Bob sounds pretty good to I may give it a go.

 

Cheers

 

Dave

[Guest Mr Pid]

Hi Daz,

 

Good thinking with ref the diesel gearbox change, im no expert on gearboxes but a couple of years ago had a few tasty RS Turbos one of which had a diesel gearbox.

 

It never gave me any problems it pulled like an ox and went off the line like s**t off a shovel- no other RST could touch it. OK it wasnt as quick top end but who wants long boring motorway races?

 

Good luck