What determines the mid engine adder?

[quadzjr]

I was recently thinking about the 50lb mid engine adder. I agree 100% that having the center of mass of the engine and drive train closer to the center of the chassis will enable the car to have a lower polar moment of inertia, thusly allow it to rotate easier, and change direction easier, yadda.. yadda.. yadda. IT is all physics we can't escape that.

Then I started thinking further about the MR2. The center of mass of the entire engine and drivetrain is probably a few inches in front of the rear wheels, mush like a FWD car is infront of the front wheels. Now if we look at RWD cars for the most part the center of mass of the drivetrain is probably significantly further towards the middle of the car than my "mid-engine" MR2.

Then I thought of the miata, It's entire drive train is between the axle centerlines. So by definition why is this not considered a mid engine car? and it's drive train center of mass is well within the axle centerlines.

So if we look from a pure physic's world, and the definition of mid engine. (engine center of mass between wheel centerlines). how does the MR2 and X1/9 differ from a miata?

Just thinking..

[ekim952522000]

I have never heard anything about a mid-engine adder?

[Greg Amy]

Steve, it's been my presumption that the adder was more for balance than for "polar moment of inertia" (PMOA is not significant at our level of technology and driving).

As such, you have a valid point, one that I've (unsuccessfully) argued in the past (as I recall, within a discussion regarding the currently-classified weight of the Mk1 MR-2 in ITB...) - GA

[quadzjr]

Steve, it's been my presumption that the adder was more for balance than for "polar moment of inertia"

It can't be for balance, since the miata runs a perfect 50/50 weight distribution and has an arguebaly better balance.

Not meaning to pick on the miata guys, but you have to admit it is a great chassis, just wondering why the MR2 got the adder and a car like the miata didn't.

I am glad that it is getting re-calculated. Now I won't have to melt two buckets full of lead... just one

[Ed Funk]

[quote=quadzjr;289207]It can't be for balance, since the miata runs a perfect 50/50 weight distribution and has an arguebaly better balance.

Not meaning to pick on the miata guys, but you have to admit it is a great chassis, just wondering why the MR2 got the adder and a car like the miata didn't.

Yeah, me too!!

[Andy Bettencourt]

It's a mid-rear engined adder.

[CRallo]

It's a mid-rear engined adder.

you would say that



on a more serious note, why only mid-rear?

[GKR_17]

Are you sure the MR2 got that adder? It was stated the 914 got it when it was moved from ITA to ITB, but that's the only one I know of for sure. I do know the ITR Boxter did not get that adder.I've said this before -- I'd like to see it noted when cars get special penalties or breaks, since all too often it seems they're not applied uniformly.Grafton

[Andy Bettencourt]

The MR2 did, I do not believe the Boxster did. At the time, it was determined that chassis and brakes in ITR were advanced enough - and at those high weights - that any 50lb adders for DW or MI was negligable.

PS: The MR2 weight is getting corrected from a calculation mistake. Read: lighter

[Knestis]

...PS: The MR2 weight is getting corrected from a calculation mistake. Read: lighter

Bag ---> Cat



K

[quadzjr]

haha Now that's funny right there!