Handling like Boxster S?

[mPlasticDesign]

Well I spent at least 3hrs staring at my engine to determine if it was fully behind the front axles and I concluded that maybe 58% of the engine is behind the front axles. So yes there is such thing as a FMR layout but by the strictest of definitions the Z4 is NOT one. Sorry guys.
"when the engine is in front of the driver, but fully behind the front axle line, the layout is sometimes called Front Mid engine Rear FMR layout instead of the less-specific term front-engine."

Originally Posted by car62

That's one thing I do like about the internet. Just when you've been trashed by morons, the cavalry comes to the rescue.

not quite recued.....

Originally Posted by drummerbrent

Not that everything on Wikipedia is correct, but this is:
http://en.wikipedia.org/wiki/FMR_layout

I was an automotive engineer for 20 years. There is such a (common) thing as a "front mid-engine" car.

20 years and you can't even read your own source....

Originally Posted by RichardTS

I do not call my car mid-engine even though it is by the strict definition. This is not to 'make me happy' - it is what it is.
Dammit, it may be difficult but there certainly is nothing wrong with learning something new.

Food for thought: Is all Kleenex tissue or is all tissue Kleenex?

[RichardTS]

Originally Posted by ///Metak

Well I spent at least 3hrs staring at my engine to determine if it was fully behind the front axles and I concluded that maybe 58% of the engine is behind the front axles. So yes there is such thing as a FMR layout but by the strictest of definitions the Z4 is NOT one. Sorry guys.
"when the engine is in front of the driver, but fully behind the front axle line, the layout is sometimes called Front Mid engine Rear FMR layout instead of the less-specific term front-engine."
not quite recued.....

20 years and you can't even read your own source....

After looking at the car again, I agree with your surmising that Z4's do not meet the rule of engine fully behind the front axle. Wheels are too far back from the front bumper.

[ersin]

Why the pi$$ing contest over the definition of mid-engine? That's not the real point.

What is important is overall weight and it's distribution. Distribution is not just front-back 50-50. It includes how far out the weight is from the CG, i.e. the moments of inertia. If all the weight is out in the front and back then the car has a higher polar moment of inertia (inertia about the vertical axis). What you want is smaller polar moment of inertia so that the car turns easier. This is done by putting as much weight as close to the center of gravity as possible. You also want the CG to be lower to the ground to help keep the body from rolling in turns.

Traditionally, you could get smaller polar moments of inertia by sticking the engine right behind the driver but ahead of the rear axle. That is what is most people think of when they think mid-engine. Whether this is technically correct or not doesn't matter. It's weight distribution that matters, not where the engine is located.

Having said that, I don't know what the moments of inertia are for either the Z4 or Boxter/Cayman. My guess is that they are close with the P cars maybe a little better. I don't know where to get these numbers.

If you are doing mods, then when you add weight try to add it close to the CG. If you're taking weight off it is better to take it off of the ends of the car, mostly front and back. I wish it were simpler but unfortunately, there's not too many things you can do to noticeably affect weight distribution.

Generally I think the best first performance mod -- for both handling and acceleration -- is to change the wheels and tires. Make them lighter (that rotating mass thing again) with stickier tires. After that I'd work on brakes. You don't have to replace them altogether, though some of the after-market BBKs have some rotational weight savings. But a pad and fluid change would make them better for hard use. A strut brace is cheap so I might consider that too.

But the best investment as mentioned above is in the driver. BMW CCA has events where you can get time behind the wheel with an instructor. Just getting out on the track for one day can improve your skill. Not only that but it's fun.

First time, casual experiences with these cars makes it seem like the Porsche's are better. But looking deeper, when an experienced driver takes these cars out it's the BMW that gets the nod.

[CalRick]

Originally Posted by RichardTS

After looking at the car again, I agree with your surmising that Z4's do not meet the rule of engine fully behind the front axle. Wheels are too far back from the front bumper.

It's difficult to make a genuine (such as it is) front mid engine car with a long engine like an I6 or V12, at least not with anything approaching current day style sensibilities. A V6 or V8 makes it possible, even if it means stuffing some of it under the windshield. The Corvette probably fits the definition, or is close, and as was mentioned sometime earlier, some of the Mazda RX's with their shorty engine did as well.

[RichardTS]

Originally Posted by CalRick

It's difficult to make a genuine (such as it is) front mid engine car with a long engine like an I6 or V12, at least not with anything approaching current day style sensibilities. A V6 or V8 makes it possible, even if it means stuffing some of it under the windshield. The Corvette probably fits the definition, or is close, and as was mentioned sometime earlier, some of the Mazda RX's with their shorty engine did as well.

The long engines are the problem. I also have an MGB and the engine is fully behind the front axle - but the four cyl. in an MGB is very short. When they made an MGB V8 a long time ago the engine was still fully behind the axle. Next time you see an MGB on the road notice how close the front wheels are to the front of the car and how long the hood is for a four cyl. car.

[Dammmittt]

Originally Posted by ersin

Why the pi$$ing contest over the definition of mid-engine? That's not the real point.

What is important is overall weight and it's distribution. Distribution is not just front-back 50-50. It includes how far out the weight is from the CG, i.e. the moments of inertia. If all the weight is out in the front and back then the car has a higher polar moment of inertia (inertia about the vertical axis). What you want is smaller polar moment of inertia so that the car turns easier. This is done by putting as much weight as close to the center of gravity as possible. You also want the CG to be lower to the ground to help keep the body from rolling in turns.

Traditionally, you could get smaller polar moments of inertia by sticking the engine right behind the driver but ahead of the rear axle. That is what is most people think of when they think mid-engine. Whether this is technically correct or not doesn't matter. It's weight distribution that matters, not where the engine is located.

Having said that, I don't know what the moments of inertia are for either the Z4 or Boxter/Cayman. My guess is that they are close with the P cars maybe a little better. I don't know where to get these numbers.

If you are doing mods, then when you add weight try to add it close to the CG. If you're taking weight off it is better to take it off of the ends of the car, mostly front and back. I wish it were simpler but unfortunately, there's not too many things you can do to noticeably affect weight distribution.

Generally I think the best first performance mod -- for both handling and acceleration -- is to change the wheels and tires. Make them lighter (that rotating mass thing again) with stickier tires. After that I'd work on brakes. You don't have to replace them altogether, though some of the after-market BBKs have some rotational weight savings. But a pad and fluid change would make them better for hard use. A strut brace is cheap so I might consider that too.

But the best investment as mentioned above is in the driver. BMW CCA has events where you can get time behind the wheel with an instructor. Just getting out on the track for one day can improve your skill. Not only that but it's fun.

First time, casual experiences with these cars makes it seem like the Porsche's are better. But looking deeper, when an experienced driver takes these cars out it's the BMW that gets the nod.

I think it has more to do with the radius of gyration, but then again I didn't read your whole post

[ersin]

Originally Posted by Dammmittt

I think it has more to do with the radius of gyration, but then again I didn't read your whole post

I guess that's useful for stiffness. But the idea is if moment of inertia is lower then less turning force (torque) is needed. If more of the mass is closer to the CG then it's easier to turn than if the mass is farther from the CG. Nothing complicated. But I believe that is one of the main reasons for using a mid-engine design.