Any way to put in a higher sixth gear so the motor spins slower at speed?
It was pretty easy to do in my VW.
Thanks.

 

but it's not so simple in a dual output shaft transmission. Also, since there are a lot less Minis out there, the cost per mod is a lot higher, and third, I think all the gear kits are for increased performance, not increase mileage.

So I'd say no luck on this one....

Matt

 

Thanks.

As I said, it was pretty easy on the VW.
Somebody found a 5th gear set from a European diesel trans that fit.
5th gear could be easily changed out without removing the engine.

Is the trans shared with any other BMW or other make, I wonder...

 

Audi TT, Ford Focus....

But still, it's a dual output shaft design. Gears in it are shared for two gears by haveing output shafts that have different final drive ratios. do some reading on the tranny... It's a rather compact complicated piece...

Matt

 

Thanks Matt.
I'll do some reading.
My mind glazes over when I try to visualize transmission action.

 

Admit it, you just wanna be able to go 160mph

 

Well, I came to this thread thinking that. Well, doing 160 and getting better gas mileage at the same time, cause at 140+, I measure gas mileage in gallons per mile, not mpg.

 

I don't think that changing the sixth gear would net any significant results as far as top speed goes. Sixth gear in the Mini is already a .82, and i think going any lower could actually hurt top speed. Maybe a more powerful engine and better aerodynamics would warrant a change in gearing. I've topped mine out on the autobahn at 146 mph and about 6000 rpm, and it really seemed to me that drag was the biggest thing holding the car back.

 

on paper, I think the S max speed is done in 5th, but I don't remember. Your numbers would indicate that the paper calc isn't the best.....

Matt

 

A .68 or .62 would be amazing especially with mods like programming and exhaust and more importantly some light forged wheels. 6th gear is for economy not top speed on the Mini. Use 5th gear for high mph performance. Either of those ratios would net another 5+ mpg.

Shawn

 

I think a .68 or a .62 would hurt performance more than anything. Even with mods the car just doesnt make enough power for either of those ratios.

On paper, (not taking power or drag into account) an R56 with 195/55/16 tires would hit 162 at the 6700 rpm limiter with the stock gear ratios.

 

There's a few online calculators for top speed that take drag and horspower into account.

Using one of them I came up with this:

With a drag coefficient of .36, a weight of 2650 lbs, and a frontal area of about 25 sqft the Mini would need roughly 270 hp to reach 162 mph

Remember, aerodynamic drag varies with the square of speed, so anything over 150 is going to start taking alot of power

 

as it has nothing to do with drag.

Matt

 

I know weight has nothing to do with drag.

In the real world there would be hundred's of variables as to what affects the car's top speed. Wind, tires, road temp, air temp, horsepower, weight, altitude, humidity etc. etc.

I think that the calculator was just using one more variable (weight) to make an estimation

 

if the caluculator is using weight for anything in the drag calc, it's a bad calculator. It really is that simple.

Now, if it's calculating how long it takes to get to speed, or the traction of the tires, or how fast the car goes before it lifts off the ground, that's different. But weight has NOTHING to do with drag.

Matt

 

Wow -- actual math.

We soooooooo just jumped the shark.

 

Once again, I know weight has nothing to do with drag. Im pretty sure I stated that once already.

I was just speculating as to why a calculator might use it. It's not a drag calculator, its a horsepower calculator. I used top speed calculator to find the top speed in sixth gear of the mini (162).

Then I used a different one to find out how much power it would take. You punch in drag, frontal area, weight, and estimated top speed (I used 162), and it tells you how much horsepower it would take to reach it.

Weight would definately affect how much power it takes to get up to top speed

 

the formula for drag based on Cd isn't a secret, you can read it and see what it's dependant on!

Fd = Cd 1/2 ρ v2 A

Matt

 

I was actually excited to see this thread b/c I thought it was meant for higher speeds of cruising, not top speed... lol

I drive an hour to work everyday, avg speed is 85 to 90 mph. I believe the rev's sit at 4-4.5k. It there was some way to lower 6th gear, that would be awesome for me! I was thinking 3-3.5k for 6th gear only....

 

6th gear is for economy and .68 is completely feasible with computer upgrade, performance intake, down-pipe and exhaust. S's are amazingly peppy at 65+ MPH in 6th. I would prefer 80 at 2750ish, considering peak torque is available under 2000 RPM. 20 years ago I have a 3400 lb Ford Turbo Coupe T-Bird which had a 2.3L SOHC 8V and it had a .68 5th gear and I never had cruising or accelerarting issues with it. As I've been saying 6th gear is for cruising on the hwy and after 65 MPH the RPM slow down would be much appreciated. I suspect it would yield close to 40 MPG in HWy driving only (no traffic of course).

Shawn

 

Why would you use 6th gear for performance? Its for economy only, 6th gear would not achieve top speed over 5th gear without major performance improvements. I'm a long way from the Autobahn in NY and I have no practical way to even get close to it.

LOL
Shawn

 

Once again...... I know exactly what its dependent on.

I must not be getting through to you. Im talking about a formula for top speed based on HORSEPOWER given certain criteria, NOT a formula for drag. I think we can drop this discussion.

As far as cruising goes, having lower revs does not mean that you will have better gas mileage, going to a lower gear could in fact increase engine load from 3-3.5k. However, if your just looking for a slower engine speed while cruising, im sure a .62 would be great

 

um like we are forgetting the easyest why to change final drive ratio is to change the tire size. if you are running 17 goto 18 the larger dia will efect your final roll out to achieve what u are looking for. dont beleave me ask any jeep guy what the put in to there pumkin when they went from a stock 30 inch tire to a 33 or a 35. stock gear is 3.55 or 3.75 in a tj to roll on a 33 or a 35 you are looking at a 4.11 or 4.88 respectively. if you dont change the gear in the pumken and run a 35 on a 3.55 rear end you make 5 gear useless because the motor cant turn it not eve the torque monster 6 they had

 

LOL it should be pretty commonsense that weight cannot affect top speed but only the time it takes to get there. Otherwise better power to weight would equal higher top speed, and mean a 30hp scooter should be just as fast as a 1000hp Veyron just because the Veyron weighs 33 times as much...

Physics works in the real world, while bad math works only on the internet.

 

I think wellzy is right. Changing tire diameter would probably be the most cost effective solution to lower revs at cruising.

Honestly, somebody with a computer upgrade, performance intake, down-pipe and exhaust wont be looking for economy in their mini. If they are, I think it would be a waste of money to change their gearbox. The cost alone of everything required would overshadow any MPG improvements