I did this to my subaru WRX in 2000. I LOVED the extra acceleration. It was like an easy 15 to 20 percent improvement on the WRX.
I HATED it in traffic. When i had to bump along in a traffic jam, you couldn't just lift your foot a little, you had to stab the accelerator to give it some momentum to stop the engine from stalling.

On the mini, it didn't even rate a mention in traffic, I saw no difference in heavy traffic performance. The mini engines are just too torquey above idle. I used one of Mad Matt's flywheels last time.

Mick

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Don't really notice the drop in revs-but in idle's at 1500.
1st gear runs upto 6500 very quick!
It is a pig to drive in heavy traffic But that doesn't happen very often...

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I like the look of that back plate

The more you can lighten the outside the better.

I beleave doc did a post some tme ago on his lightened flywheel

Here ya go-
std `one piece' late Mini, std HEAVY Morris 1100S, DrMini lightened one, 6.1kg. It used to look like the middle one....

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Nice work doc.

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May the fork be with you.

OK, now we're trading pics I'll get the camera out tonight

does the cooper s have a different flywheel? or are all 1275 flywheels compatible for a cooper s engine ?

the reason i ask is that i have a cooper s short motor but i don't have the flywheel. any suggestions ?

*ahem*
Gentlemen, introducing....the lightened A series flywheel:




From memory, about 4.85kg.

Drilling like that on cast iron flywheels is OK, don't be tempted to slot them out like the light steel ones though..
Cast iron has bloody weak tensile strength.... so more likely to go BANG!!

Another thing- NEVER ever weld the ring gear to a cast iron flywheel- it's a recipe for cracking.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Stu the one on the right looks like a frisbe maybe we could take down to himatangi beach and try it out

what I know so far is

lightened flywheels make your idle poorer as theres not as much mass evening each combustion stroke of the engine out

also supposedly reduce your ability to drive the car uphill, as the increased inertia keeps the engine spinning.

lightened flywheels assist acceleration and deceleration of the engine and effectively make your car lighter through the gears except in top gear.

you cant safely lighten a mini flywheel very much

the morris 1100 (1275cc) flywheel is super heavy to help fix dodgyness from the clutch i think?

How to Modify Your mini. Has an explaination of the effect lightening of the flywheel makes with a formula for calculating the benefit of lightening the flywheel has in terms of kgs of the car. Can't be botheredx to check but it's something like 1kg off flywheel=9.81 kg off the car, or something like that, get the book and check!

As for 'designer', I am pretty sure the 'S' has a lighter flywheel standard. But how much lighter I'm not sure, it's lsited in How To modify Your Mini by David Vizard as well. If you don't have it....get it!

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

What I know so far...people who say a light flywheel detracts from drivability, gives poor idle, or (noticably) decreases power on hills...usually don't have a lightened flywheel

i own one and will replace it ASAP. its nice to drive on open roads, idle is normal but its a pain in stop and go traffic as I rearly have to rev high (minimum 2000RPM) to move from traffic light to traffic light

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Rover 214 atm ....