Close Ratio Gearboxes...
Close Ratio Gearboxes...
Author
Discussion

BCA

Original Poster:

8,651 posts

286 months

Wednesday 3rd August 2005
quotequote all
...the TVR ones that is. I keep reading about them on the Sagaris, and other S6 powered cars that have them retrofitted. It interests me that they will do 60+ in first and 100 in second, meaning a more "wide torque band friedly" set up.

Anyway, my question is this: Surely this gearbox would fit the characteristics of a 4.5 (mapped would be better still) more than those of the S6??? Does anyone know what the costs are for one?+ fitting if poss??? Surely that would be quite beneficial to a 4.5 Cerb??

RR Cerbera

125 posts

313 months

Wednesday 3rd August 2005
quotequote all
I'm not sure what the costs to retrofit one of these gearboxes are but I can wholeheartedly recommend them! The overtaking ability is simply stunning in second gear but I'm seldom brave enough to knock it down to first to overtake 30-40mph traffic for fear of falling off of the road.

The only downside is that you have to give it a few revs for a fast getaway from standstill otherwise it will bog down.

I'm not sure if it's the CR box or the Red Rose specification that makes this car seem so much faster than my last 4.5.

Richard

carl_w

10,731 posts

287 months

Wednesday 3rd August 2005
quotequote all
BCA said:
...the TVR ones that is. I keep reading about them on the Sagaris, and other S6 powered cars that have them retrofitted. It interests me that they will do 60+ in first and 100 in second, meaning a more "wide torque band friedly" set up.
I'm not getting this -- what you described sounds like a wide ratio gearbox to me.

BCA

Original Poster:

8,651 posts

286 months

Wednesday 3rd August 2005
quotequote all
carl_w said:

BCA said:
...the TVR ones that is. I keep reading about them on the Sagaris, and other S6 powered cars that have them retrofitted. It interests me that they will do 60+ in first and 100 in second, meaning a more "wide torque band friedly" set up.

I'm not getting this -- what you described sounds like a wide ratio gearbox to me.


Thats why I said "The TVR ones that is" because it seems wrong to my mind too, surely a close ratio box are ones where the ratios are closer and therefore the possible speeds in each gear are lower?? better for accel if theres low torque... so yeah, TVR stylee box is what im on about.

RR Cerbera

125 posts

313 months

Wednesday 3rd August 2005
quotequote all
First and second gears are higher than standard which means that second and third gears are "close ratios". I think that third, fourth and fifth are the same as the standard gearbox but I maybe wrong.

shpub

8,507 posts

301 months

Thursday 4th August 2005
quotequote all
Typically CR gearboxes have higher first and lower fifth or some combination so that first gear is more like second and then subsequent gearchanges only reduce the revs by a little to keep the engine well into the power band. I had a custom one made with straight cut gears for the 520 and I drop only around 1750 to 2000 revs in gear changes. Each gear change means the engine is pretty well on peak torque after the change and this makes for some exciting acceleration.

Getting off the line is like driving off in a normal second. Lots of revs needed.

daftlad

3,324 posts

270 months

Thursday 4th August 2005
quotequote all
The CR box fitted to the S6 engines has higher first second and third gear ratios. 4th and 5th are standard.
Standard ratios are
2.95:1
1.95:1
1.34:1
1.00:1
0.80:1
CR is
2.43:1
1.56:1
1.24:1
1.00:1
0.80:1