LSD or not?

[SLR No.77]

Quoting Paul Richards: 

Quoting Jason Fletcher: 

Quoting Paul Richards: 

I am looking at this as a way to shorten the gap between second and first."

 

Changing diff ratio won't change that.

 

 

I think it will.

 

here

 

J

 

Jason

Not sure how you think it will change the gap.

Changing the diff will simply lower the overall gearing in every gear. The ratios for 1st and 2nd will not be changed. The maximum speed in each gear will reduce and therefore in MPH terms there will be less gap.

However, when reducing the gap between gears you are looking to drop into the power band when changing up and this will not change as engine revs will remain the same.

Hope this explains. 😬 Back to the issue about final drive ratio and gear spacing ...... running a bigger ration diff WILL reduce the gap between 1st and 2nd.

 

In simplistic terms, consider the following - a diff ratio is fitted that gives a 6th (or top) gear speed of 120mph at 6000rpm. Now swap the diff for one that brings the top gear speed down to 60mph at 6000rpm, reducing the effective speed of each gear accordingly. The result is that there are now 6 gears from 0 to 60mph, previously there were 3 (approx) ... therefore it is effectively a close ratio version of the original scenario. Jason is correct.

 

Stu.

 

Edited by - sforshaw on 6 Jun 2013 14:13:46

[Bob_r]

So in Jasons scenario, you are still using the same range of engine speeds (revs), between gear changes to obtain a lower road speed. For What benefit?

Very strange definition of a close ratio box!

 

[charlie_pank]

Quoting jingars: 

...dropping my final drive from 3.92 to 3.62...[because it] is a bit buzzy on the motorway...

 

Just to be clear about this:

You're going to decrease your acceleration for the sake of motorway driving... in a 7?

[Bob_r]

Decrease your acceleration.......omg, must be about the same as replacing worn tyres with new ones

[charlie_pank]

Quoting Bob_r: 

Decrease your acceleration.......omg, must be about the same as replacing worn tyres with new ones

 

Have you ever driven the same 7 with different diff ratios? To reduce the buziness at motorway speeds, he's going to reduce the engine speed at a given road-speed in every gear. The amount buziness is reduced by will directly correlate with the reduction in engine speed for a fixed road speed and thus a reduction in responsiveness. I simply do not understand taking a Caterham and then making adjustments to it to improve comfort levels on long motorway drives at the expense of performance... why not buy an M3 instead?

[charlie_pank]

When I finished my R1 build with a 1:3.something diff it was sluggish off the line and I could drive at 80 in 1st gear. I swapped it out for a 3.62 which transformed the performance when moving off and accelerating and changed my 1st to 2nd upshift point to 60mph.

 

If you don't think the diff ratio makes a difference, then why are there different ones available!?

[jingars]

Easy now, boys.

 

Just to be clear about this:

I am not planning to decrease my acceleration for the sake of motorway driving.

 

The car was originally a 1.4 K. Prior to me acquiring it, it was converted to 1.8K.

 

The suggestion from Phil at R&R is that the extra torque of the 1.8 would better suit a 3.62 final drive.

 

The car currently tops out at 119 mph. It has grunt to spare, but runs out of revs in 6th. The suggestion is that additional performance can be unlocked by revising the gearing. I am prepared to take Phil's advice and run with it. If it doesn't pan out and acceleration suffers markedly, then I still have my current diff and can have Phil swap the 3.92 over to the LSD.

[SLR No.77]

If your car was a 1.4 and is fitted with a 3.92 diff, it will also have been originally fitted with a 5 speed gearbox (unless the diff has been swapped from a 3.62). When the 6 speed option was specified a 3.62 diff was used.

 

Stu.

[A_redstone]

Hi

 

Whilst I cant join the debate about 3.92 or 3.62......I will take it from my original question that having a LSD is worth it and a whole lot of fun !

 

Hope to see the difference in 2 weeks time when I collect from Dartford

 

Thanks

 

A

[Fishy Dave]

Hi Andrew,

 

Thanks for your e-mail, thought I'd reply to this thread instead .

Another vote for an LSD being worth every penny in my opinion. So much depends on how and where you drive your car of course. For me the increased traction on track and easier way of getting a controlled drift out of junctions enhances the rear wheel drive pleasure that Sevens bring.

Do you know what type of LSD Caterham fit? For drifting purposes I'm not sure I would go for an ATB torque biasing type, but others may have views on this.

 

Cheers, Dave

[A_redstone]

Quoting Fishy Dave: 

Hi Andrew,

 

Thanks for your e-mail, thought I'd reply to this thread instead .

Another vote for an LSD being worth every penny in my opinion. So much depends on how and where you drive your car of course. For me the increased traction on track and easier way of getting a controlled drift out of junctions enhances the rear wheel drive pleasure that Sevens bring.

Do you know what type of LSD Caterham fit? For drifting purposes I'm not sure I would go for an ATB torque biasing type, but others may have views on this.

 

Cheers, Dave

 

Thanks Dave, I asked and they said its the one that goes on all new production cars !...helpful eh ?

 

Hoping to have more fun out of junctions and roundabouts in Bath soon.......

 

[Bob_r]

The Caterham fitted LSD works fine for drifting on the CDX cars, and is great on track as well.

Just a pity that K series are no longer available.......lol

 

As with all LSD though, when new to it be careful in the wet! 🙅🏻‍♂️

 

Edited by - Bob_r on 7 Jun 2013 17:10:32

[DJ.]

I have to say, I was a little concerned after fitting my LSD, about driving in the wet after reading posts on several forums.

 

I have now driven in some appalling conditions (bad enough to get aquaplaning at low speed), and I must say I find the car to be more predictable and actually better to drive in the wet than with an open diff.

 

It is quite possible to lose the back end on a Seven style car in the wet without having an LSD fitted, and judicious use of the accelerator will always be necessary.

 

Duncan

[Ged]

Quoting sforshaw: 

If your car was a 1.4 and is fitted with a 3.92 diff, it will also have been originally fitted with a 5 speed gearbox (unless the diff has been swapped from a 3.62). When the 6 speed option was specified a 3.62 diff was used.

 

Stu.

 

I don't think that is quite correct. I had a 1.4 Ltd Edition, came with a 6 speed box as standard, that came with a 3.92 diff. The original owner may have specc'd it, but I had the original order form with the extra's boxes ticked and a couple of hand written notes regarding additional features, but no mention of a non standard diff.

My current R300D has a 3.38 diff, which I find ideal for touring with the torque of the duratec engine. But the original builder had specc'd it to allow a higher top speed on faster circuits. He is vastly experienced with Caterhams and found the standard 3.62 ratio had the car hitting the rev limiter in 6th on the longer straights.

[The Pikey]

.

 

Edited by - Jason Fletcher on 7 Jun 2013 20:13:26

[Bob_r]