I know we're talking a straight 6 here, but it is FI. When I did long tubes on my 2v 4.6 in my Mustang GT it definitely gained low end torque. Not sure about HP in that area, but torque for sure. I cut ~.4 sec (can't remember exact, was a long time ago) in the 1/4 mile after install with an accompanying Diablo tune.

Yep, I feel it!

I had to learn to drive the thing again when the 8lb flywheel was installed. Looks like the same thing again with the headers. The torque changes were very noticeable. I bet the ethanol has a role in it as well.

It’s been cold, so I haven’t used the meth kit yet. That’s probably going to change the characteristics at the top end as well.

A lighter flywheel reduces torque which is very important when trying to get an X5 moving. The engine will rev faster but that doesn't help performance except maybe at close to redline. Even going quicker are high RPMs won't offset loss at low end.

A lighter flywheel reduces torque? Pray tell how that works.

It doesn't.

https://www.motortrend.com/how-to/im...aily%20driving).

Right, it doesn't. Always a good idea to review before posting. Oopsie.

What a lighter flywheel does do is decrease inertia so more torque is necessary to correct the loss of inertia to achieve better times over a a short distance. A lighter flywheel, especially on a heavy vehicle like an X5 will likely increase the amount of time to get from 0-60 feet. However, somewhere less than a quarter mile the vehicle should be faster but not always. The key to improving times over shorter distances using a light flywheel is also adding back torque to offset the lost inertia.

What you said is only true in the moment that you are dumping a clutch. Otherwise a lighter flywheel, having less mass and therefore less linear and rotational inertia, will always contribute to faster acceleration.

Yes, that is what I said. It will be faster but the vehicle will travel some measure of distance before it is faster than it was with the stock flywheel.

There are so many variables that go into realizing the benefits of a lighter flywheel it is just not a slam dunk they will be beneficial for all applications. There are also downsides that can contribute to other failures, especially if used on a daily driver. Considering all the options to go faster, and how much contribution a perfect application of a lighter flywheel can make, a lighter flywheel is way way down my list of a cost/benefit value ranking.

Ok let’s put the small talk aside for a bit.

Today is an amazing weather day in Houston! 72 degree ambient temperature, I had the E53 completely warmed up, but not heat soaked.

I activated the meth injection.

I was at a cruising speed of about 46 mph, when I rev matched a downshift into 3rd gear, from 4th. From about 4400, to 6100 rpm, which put me at speed of about 88 mph, it only took 4 1/2 car lengths in total.

2 lengths past the 2 Stangs that were riling me a bit (I was about a 1/2 a car length behind), while they were cruising at about 48-49 mph.

It took 3 1/2 to 4 seconds to top out at nearly 90 mph. That will be the last time I try that.

2 ton takes a noble responsibility to handle. I don’t want to be the idiot, that crashes the 2nd fastest manual E53 (the only one with power to all 4 wheels) in the world.

Take it with a gain of salt. My take will be, “take it easy”.

Just my two cents..

What do you mean by only one with power to all four wheels?