Diff Ratio Change
Discussion
Quick question,
has anyone gone up from a standard diff ratio to say 3:71 or 3:91 as with past experience in the TVR world this is the best £/ gain improvement to a straight six engine combo. Past experience = cleaner crisper rev out faster acceleration and almost motorcycle rev climb.
Answers not on a postcard, but here please.
has anyone gone up from a standard diff ratio to say 3:71 or 3:91 as with past experience in the TVR world this is the best £/ gain improvement to a straight six engine combo. Past experience = cleaner crisper rev out faster acceleration and almost motorcycle rev climb.
Answers not on a postcard, but here please.
Why would you want to do this...? more revs, more noise, more fuel used.. for very little gain.. perhaps if you were drag racing and the ratios worked out best to get max rpm as you go over the line..this would have a benefit.. but for road use..M car ratio spacing is pretty good as it is.. 
It has been done, speak to simpson motorsport - www.simpsonmotorsport.com
Seems to make some sense to me, the car is geared to 206mph or something silly that it'll never get to anyway, bring it down and get better acceleration, seems like a good deal. Dunno if you'd need to consider diff coolers etc but simpsons would know.
Seems to make some sense to me, the car is geared to 206mph or something silly that it'll never get to anyway, bring it down and get better acceleration, seems like a good deal. Dunno if you'd need to consider diff coolers etc but simpsons would know.
Well Nathan, thanks for that. I will give them a bell. As for fuel consumption that is not an issue. You can always change up a gear sooner when driving on the road, and whos interested in fuel consumption on a track day anyway.
My thoughts are that this will be a mod that would really benefit this car. I am not interested in trying to do 175 on one occasion in Germany but having a harder accelerating car that is better geared in 3rd and 4th. Most of my track days will rarely involve top two gears.
My thoughts are that this will be a mod that would really benefit this car. I am not interested in trying to do 175 on one occasion in Germany but having a harder accelerating car that is better geared in 3rd and 4th. Most of my track days will rarely involve top two gears.
For track days.. i can see the logic..
but this will suit some circuits much better than others, Silverstone GP for example, the straights are well suited to 4th gear.. and i just get max rpm down hanger straight, nearly max on the back and pit straight.. this would introduce 6 extra shifts, up and down.
On balance would it actualy gain you any lap time..? i doubt.. sure the pick up would be a little better.. but you would loose it all in axtra shift times..
On a shorter club circuit is may be beneficial.. if you feel its worth the cost of course..!
but this will suit some circuits much better than others, Silverstone GP for example, the straights are well suited to 4th gear.. and i just get max rpm down hanger straight, nearly max on the back and pit straight.. this would introduce 6 extra shifts, up and down.
On balance would it actualy gain you any lap time..? i doubt.. sure the pick up would be a little better.. but you would loose it all in axtra shift times..
On a shorter club circuit is may be beneficial.. if you feel its worth the cost of course..!
RatBoy M3CS said:
For track days.. i can see the logic..
but this will suit some circuits much better than others, Silverstone GP for example, the straights are well suited to 4th gear.. and i just get max rpm down hanger straight, nearly max on the back and pit straight.. this would introduce 6 extra shifts, up and down.
On balance would it actualy gain you any lap time..? i doubt.. sure the pick up would be a little better.. but you would loose it all in axtra shift times..
On a shorter club circuit is may be beneficial.. if you feel its worth the cost of course..!
The cost for the TVR was about £900.00 fitted with a 3:73 C/W and pinion. The difference from standard was immense. Standard being 3:45. Just wanted to know how far people would go on the ratio. eg some track/ sprint Sagaris cars ran 3:91, but its a bit low for everyday use. Nice compromise is whats required. Standard diff is too tall and its cheaper than messing with the gear ratios. from past experience it will bring down the lap times as there are not many circuits in the world where you would be flat in 5th or 6th with standard set up.but this will suit some circuits much better than others, Silverstone GP for example, the straights are well suited to 4th gear.. and i just get max rpm down hanger straight, nearly max on the back and pit straight.. this would introduce 6 extra shifts, up and down.
On balance would it actualy gain you any lap time..? i doubt.. sure the pick up would be a little better.. but you would loose it all in axtra shift times..
On a shorter club circuit is may be beneficial.. if you feel its worth the cost of course..!
You are right .. the gearing is really tall,.. which is fine sat on a motorway.. but it does compromise the get up and go for sure..!
I would like to see if it adds up to much of a lap time improvement tho'.. on the GP.. its all 3rd and 4th.. 4th is spot on there... but of course some tracks suit some ratios better than others... with another tooth on the crown wheel, it could work out better, but you may only need half of 5th... depends how much your chasing lap times .. for racing purposes only you would go down this road for sure..
Current gearing keeps it off cam for road work at non license loosing speeds...!
I would like to see if it adds up to much of a lap time improvement tho'.. on the GP.. its all 3rd and 4th.. 4th is spot on there... but of course some tracks suit some ratios better than others... with another tooth on the crown wheel, it could work out better, but you may only need half of 5th... depends how much your chasing lap times .. for racing purposes only you would go down this road for sure..
Current gearing keeps it off cam for road work at non license loosing speeds...!
My experience with 3.46 to 3.91 diffs are as follows:
In a Sagaris 3.46 diff without CR/Box (Postman Pat...)
In a Tuscan S 3.73 diff with CR/Box (Jenson Button with facial hair...)
In a Sagaris 3.91 diff with CR/Box (Neil Armstrong in a Saturn 5 Rocket...)
Higher the diff more savage accelaration but top end diminishes
In a Sagaris 3.46 diff without CR/Box (Postman Pat...)
In a Tuscan S 3.73 diff with CR/Box (Jenson Button with facial hair...)
In a Sagaris 3.91 diff with CR/Box (Neil Armstrong in a Saturn 5 Rocket...)
Higher the diff more savage accelaration but top end diminishes
There are few circuits where you are using full revs in 6th in the CSL.. so to that extent I think this would be a great mod. In fact I think I'll give it a go.
In my E36M3 race car we run a shorter diff and the five-speed box from the 3.0M3 to good effect and it really does make a difference to the cars.
In my E36M3 race car we run a shorter diff and the five-speed box from the 3.0M3 to good effect and it really does make a difference to the cars.
houlbt said:
There are few circuits where you are using full revs in 6th in the CSL.. so to that extent I think this would be a great mod. In fact I think I'll give it a go.
In my E36M3 race car we run a shorter diff and the five-speed box from the 3.0M3 to good effect and it really does make a difference to the cars.
Let us know how it goes please.In my E36M3 race car we run a shorter diff and the five-speed box from the 3.0M3 to good effect and it really does make a difference to the cars.
Do you think you'll need a diff cooler or any additional cooling elsewhere?
More info.
A crown wheel and pinion is about £550.00 plus fitting. The best yet seems to be the fitting of a proper job Quaiffe LSD with a ratio to suit. Probably 3.91:1 so as soon as I have decided which way to go and fitted it I will let you all know,
but should be fast as. Absolutely unbeleivable that people pay big bucks for decats, cams or superchargers and no ones done this mod yet! I thought CSL owners were a really knowledgable crowd too. Maybe this one has been overlooked for rose tinted glasses reasons.
I think personally with the right ratio that a standard csl to 125mph will be as quick as a supercharged car on standard diff. Not meant as an insult to csl crew, but I seriously think that this will be the best mod to date.
A crown wheel and pinion is about £550.00 plus fitting. The best yet seems to be the fitting of a proper job Quaiffe LSD with a ratio to suit. Probably 3.91:1 so as soon as I have decided which way to go and fitted it I will let you all know,
but should be fast as. Absolutely unbeleivable that people pay big bucks for decats, cams or superchargers and no ones done this mod yet! I thought CSL owners were a really knowledgable crowd too. Maybe this one has been overlooked for rose tinted glasses reasons.
I think personally with the right ratio that a standard csl to 125mph will be as quick as a supercharged car on standard diff. Not meant as an insult to csl crew, but I seriously think that this will be the best mod to date.
It has been done before and using proper Drexxler plated diffs rather than the quaiffe 
There was some debate on MTorque CSL forum about what, if anything, would need doing to the SMG programing for things like working out if you are allowed to change down.
Not sure what the answer was as the person I'm thinking of who did it also put a Drenth sequential box so got rid of SMG and a Motec M800 ecu for the engine.
Has also been done the world over on M3s,Turner Motorsport sell 3.91 or 4.1 diff rebuilds or just the ring and pinion kit (for £375 + import duty & vat, might end up cheaper than £550?).
Turner claim an 8% increase in torque at the wheels for the lower ratio diff, supercharger will give you a lot more than that I'd have thought...
It is something I've thought about before but IMO making it quicker in a straight line is pointless until you've sorted out suspension and brakes.
PS. http://www.turnermotorsport.com/html/show_category...
There was some debate on MTorque CSL forum about what, if anything, would need doing to the SMG programing for things like working out if you are allowed to change down.
Not sure what the answer was as the person I'm thinking of who did it also put a Drenth sequential box so got rid of SMG and a Motec M800 ecu for the engine.
Has also been done the world over on M3s,Turner Motorsport sell 3.91 or 4.1 diff rebuilds or just the ring and pinion kit (for £375 + import duty & vat, might end up cheaper than £550?).
Turner claim an 8% increase in torque at the wheels for the lower ratio diff, supercharger will give you a lot more than that I'd have thought...
It is something I've thought about before but IMO making it quicker in a straight line is pointless until you've sorted out suspension and brakes.
PS. http://www.turnermotorsport.com/html/show_category...
Edited by m12_nathan on Sunday 17th August 12:31
m12_nathan said:
It has been done before and using proper Drexxler plated diffs rather than the quaiffe
There was some debate on MTorque CSL forum about what, if anything, would need doing to the SMG programing for things like working out if you are allowed to change down.
Not sure what the answer was as the person I'm thinking of who did it also put a Drenth sequential box so got rid of SMG and a Motec M800 ecu for the engine.
Has also been done the world over on M3s, http://www.turnermotorsport.com/html/index.asp sell 3.91 or 4.1 diff rebuilds or just the ring and pinion kit (for £375 + import duty & vat, might end up cheaper than £550?).
Turner claim an 8% increase in torque at the wheels for the lower ratio diff, supercharger will give you a lot more than that I'd have thought...
It is something I've thought about before but IMO making it quicker in a straight line is pointless until you've sorted out suspension and brakes.
I totally agree with your comments, but the brakes have been done and the suspension is on the list. Thankyou for the input and constructive comment though.There was some debate on MTorque CSL forum about what, if anything, would need doing to the SMG programing for things like working out if you are allowed to change down.
Not sure what the answer was as the person I'm thinking of who did it also put a Drenth sequential box so got rid of SMG and a Motec M800 ecu for the engine.
Has also been done the world over on M3s, http://www.turnermotorsport.com/html/index.asp sell 3.91 or 4.1 diff rebuilds or just the ring and pinion kit (for £375 + import duty & vat, might end up cheaper than £550?).
Turner claim an 8% increase in torque at the wheels for the lower ratio diff, supercharger will give you a lot more than that I'd have thought...
It is something I've thought about before but IMO making it quicker in a straight line is pointless until you've sorted out suspension and brakes.
I had my spare diff rebuilt with a greater amount of slip allowed by it.
Left the ratio alone, as the car will only really get used at the 'ring, and spa, so I don't find the gearing a problem.
I did add a cooler though, as the reason I had two diffs, is they tended to overheat, and eat themselves (hence why I had a spare).
Left the ratio alone, as the car will only really get used at the 'ring, and spa, so I don't find the gearing a problem.
I did add a cooler though, as the reason I had two diffs, is they tended to overheat, and eat themselves (hence why I had a spare).
Ref: diff oil coolers.. how hot does the diff get..? are they generally robust enough for track day work.. ie 4 or 5 quick laps and then a cooling down lap..?
Or is it just 30-40 minutes balls our racing where they overheat and let go..?
Are there any tell tale signs that its overheating and about to let go..? apart from whining and a bang...!
Or is it just 30-40 minutes balls our racing where they overheat and let go..?
Are there any tell tale signs that its overheating and about to let go..? apart from whining and a bang...!
Edited by RatBoy M3CS on Saturday 24th January 12:49
1) It is grating on the motorway as soon as you get passed 100. On the bright side you get to the 100 much quicker.
2) It is like making each gear 40% shorter. 2nd gear is like 1.5 of old, 3rd is 2.5 etc. 3rd gear is simply stunning, like a 430 at full chat. Acceleration is simply stunning and you fly through the gears.
3) With the sport button on or off - in the wet, with cups, you better have quick reactions. The car will snap in fourth gear let alone anything below.
4) Fuel economy is worse but not terrible. I drove from London to Sheffield today and back which at about 350 miles is the longest drive I have done with the new diff. Went through 1.5 tanks.
5) The car is noisier and twitchier at speed. Becasue you are at such high rpm, even at 120 (cool down lap
) any bump in the road will make you bunny hop. You have to concentrate 100% of the time and keep both hands and penis on the wheel.
6) On track this should mean much better results? I have only done Silverstone so far and as that track has expensive memories for me I cant really say if it is faster - but it bloody well should be!
Overall I love it. Ther are + and - but the car is faster without doubt, but this has helped extend my time with the car.
2) It is like making each gear 40% shorter. 2nd gear is like 1.5 of old, 3rd is 2.5 etc. 3rd gear is simply stunning, like a 430 at full chat. Acceleration is simply stunning and you fly through the gears.
3) With the sport button on or off - in the wet, with cups, you better have quick reactions. The car will snap in fourth gear let alone anything below.
4) Fuel economy is worse but not terrible. I drove from London to Sheffield today and back which at about 350 miles is the longest drive I have done with the new diff. Went through 1.5 tanks.
5) The car is noisier and twitchier at speed. Becasue you are at such high rpm, even at 120 (cool down lap
) any bump in the road will make you bunny hop. You have to concentrate 100% of the time and keep both hands and penis on the wheel.6) On track this should mean much better results? I have only done Silverstone so far and as that track has expensive memories for me I cant really say if it is faster - but it bloody well should be!
Overall I love it. Ther are + and - but the car is faster without doubt, but this has helped extend my time with the car.
Gassing Station | CSL | Top of Page | What's New | My Stuff