550i-sport

Has anyone upgraded to Dinan flywheel on their 550i 6-speed? Dinan rep said it+differential upgrade would virtually eliminate driveline hp losses. Any thoughts?

sirch

Adding a lightened flywheel will allow the car to accelerate faster, but will make the car work harder to mantain a constant speed. It's seems that no performance upgrades come without a con.

How much do they lighten the flywheel??

An alternative method maybe for you to get a used flywheel and have it locally lathed down and then cyroed to make the metal stronger. I've found used flywheels in the past for under $20 and paid a local machine shop to do the work for $100, I'm not sure how much a used e60 flywheel is however.

Best of luck.

AlB

Me thinks he is a better salesman than technician. You will be able to feel better response with a lightened flywheel (less rotating mass) and a much greater torque multiplication (circa 18%) with the 3.45 gears, there is no way it will gain 60 hp which is approximate parasitic loss for the 550i. They are, IMO, the best mods that can be done for the manual in terms of performance increases, but they do come at a price.

good luck

pennetta

A lightened flywheel will only allow the engine to rev faster, it does not increase HP. The reason for a flywheel is so the engine idles more smoothly and so its harder to stall it when taking off in first gear. You can also remove weight from the crankshaft, install hollow cams, install lighter pistons etc. which remove recipricating mass, but again it will at the cost of civility.

Roleez

I don't have either the Dinan flywheel or 3.45 diff installed in my 550i, but I have taken a thorough test drive of Dinan's 645Ci SMG with all the Dinan mods, including the flywheel + 3.45 diff. Compared to my car (which also has the same gear ratios), the 645Ci FLIES like there's a pair of mini rocket boosters strapped to the rear end. Acceleration in my 550 with throttle body + exhaust + K&N filter does give you that stuck to the seat feeling when redlining the gears. But the thrust sensation heightens as the revs build up after each gear change. In the 645Ci, the thrust is neverending/constant with each gear change, like you're only accelerating in one gear. It's not really the SMG, it's truly the 3.45 gears being able to put the power to the ground vs. the stock 2.93 gears. Keep in mind that mileage will suffer since the 3.45 adds 300 rpms to your cruising revs. Steve Dinan himself did admit to me when taking my car for a test run that the 550 does have difficulty in putting all that power to the rear wheels, primarily because of the conservative 2.93 rear end. But add a 3.45, and Dinan says that any 550/650 manual/SMG will be able to have the equivalent performance of an E39 M5. I have considered getting those mods done to my car, but at the moment, I'm still truly satisfied with my car's power output. It's performance as-is is perfect and I wouldn't have it any other way ... unless they decide to release their CAI! As much as I'd love to have faster acceleration, I'm not too keen on the $4000+ price tag for the parts/labor.

pennetta

Installing a 3.45 diff will give you more power to the ground simply because you are getting a better mechanical advantage with the changed gearing. Like riding a ten speed bike and accelerating from a stop with the chain on the largest rear sprocket instead of the smallest rear sprocket.