550i-sport

In talking with a Dinan rep, he said that my 550 would walk away from an E39 M5 with these mods. Has anyone installed them and done a performance comparison - i.e. 0-60, top-end, hp@wheels, mpg?

miguex

Is your 550i is manual or SMG, yes you can change the flywheel.

Which Differential mod? LSD?

Quaife LSD is the best. I highly recommend: http://www.hpashop.com/product.sc?productI...;categoryId=114

with LSD installed on your 550i you will feel true M.

550i-sport

Manual transmission, stock differential. The mod I'm referring to is the 3.45 option - link attached. Thanks.

http://www.dinancars.com/store/product.php...=706&page=1

AlexFW

No, don't do it: 3.45 would give too short gears!!
(check my sig, I have a little experience of this)

mhs525

Changing the gears will have a hell of an effect on the torque multiplication and it will launch like a rocket. You would definitely need an LSD with those gears or you would smoke the right rear tire every time you tried to launch the car aggressively.

I changed my M3 gears from 3.64 to 3.91 and loved it but I drove a car with 4:10's that I didn't like. You couldn't go 5 feet in that car in 1st gear without bumping up against the rev limiter and it was very buzzy on the highway due to increased engine speeds at 70-80mph.

Not sure what the 550 transmission ratios are but to make an informed decision drive on the highway at your normal cruising speed or a little above, note the RPM, ask the Dinan rep what your RPM would be at that speed with the new gears, then get back in the highway and cruise at that projected RPM by choosing a lower transmission gear (5th vs 6th???). That will tell you what the trade off in highway engine speed would be for the increased down low acceleration you would get with 3:45's.

Gears are a great mod (sometimes referred to as a poor mans supercharger) however an LSD is required to have any hope of putting down that much power effectively.

It would be a damn fast car but you might want to not want to change the ratios that much.

EuroCarFan

I've been debating on getting the Dinan diff for my car as well but have heard mixed reviews about it on M5Board. I think most notable was where a couple of members from Dallas did some runs to compare an M5 with the Dinan diff to a stock (I think) M5 and the stock M5 won. It could have been a fluke and that the stock M5 was one of those strong cars from the factory.

jm545i

It would probably be wise to get the Quaife unit with altered gear ratios rather than the Dinan rear-end, which as far as I know merely swaps in a shorter gearset but is still open. (More expensive I know).

The one piece that people are overlooking so far is the lightened flywheel. I am told it results in a transformed machine, and would have a very real impact on slow-speed starts where flywheel momentum plays a particularly significant role. The stock unit is ungodly heavy (at least I understand that to be the case in the v-8 cars), letting them run a super-low idle speed.

With the cost of these particular upgrades, would be nice to drive a modified vehicle before laying down the cash!

NoName545i

Thanks
how a lightweight flywheel works

mhs525

Be careful with lightweight fly wheels, the OEM ones are heavy for a reason, they control gearbox noise.

I had a lightweight flywheel in my M3... for about a week. Cost me a grand to have it put back to stock. The gear rattle in neutral was horrendous, made a $60k car sound like a POS track rat. Don't recommend this mod for street cars and definitely not an E60.

mhs525

M5's (all M cars) come with an LSD, putting in a Dinan LSD is not going to make much difference. If you change the gears in one car but both cars have LSD's the shorter geared car will win a drag race every time.

The bang for the buck is taking a high horsepower non M car, like a 545/550, changing the gears and installing the LSD will dramatically change the car. The result is M car acceleration and driving dynamics without the super stiff suspension. Sort of like the Alpina approach to high performance road cars