4cpu

I have a question and it is a question so please no insults or hot tempers.

I remember reading that Porsche engineers wanted to stop producing 911's 20+ years ago. The reason was the rear, not midengine, design. The accountants did not, because the car sells. I understand why they use a rear engine design. Actually a mid engine design seems to be also a poor choice with large engines (>2 L). The sound and heat insulation takes up too much space and weight. The front engine rear drive car is a superior design as seen in the S2000, Corvette, etc cars with nearly perfect weight distribution and balanced handling. Even after reading about the NSX, I wonder if the car should even be resurrected again

Not really having to do with my question, but an issue that I have noticed in many expensive and otherwise fine cars--Cross drilled or vented rotors (the need for that disappeared in the 70's when gas formation from pads was no longer a problem. The slotting/drilling weakens the rotor making it prone to breaks--who wants that? I see SUV's with narrow rim tires--it can't help with handling (the center of gravity is too high, and sooner or much sooner the rim will dent and you will have an unbaleanceable tire/wheel.

So the question is, is there any significant advantage to rear or midengine designs or is this a relic from the past which still sells because the typical buyer does not know the difference? Am I missing something?

waltk88

It wasn't the accountants per se that kept the 911 alive - it was the market.

Advantages of the 911's rear engine configuration:
Great traction. Weight of engine over the rear wheels benefits drive traction.
Braking. Due to the rearward weight distribution braking loads are distributed more evenly between front and rear.

4cpu

The accountants were looking at the sales, yes. All you have described is straight acceleration/dec. Is that it for what you give up? How about midengine? By the way, I think the Boxster is their best designed car and there are rumors of resurecting the 928 even the name (No.).

PedalFaster

[QUOTE=4cpu,Nov 18 2006, 01:27 PM]So the question is, is there any significant advantage to rear or midengine designs or is this a relic from the past which still sells because the typical buyer does not know the difference?

fx991

reasons for a mid-engine rear drive design are as follows:
1) Packaging, it keeps the gearbox, engine and drive wheels close together, eliminating a long drive shaft and more potential losses and an engine that is more throttle sensitive (doesn't have to turn the big heavy drive shaft)

2) Moment of Inertia, with all the mass centralized, the moment of inertia is alot lower, resulting in faster changes in directions that require less overall force on the car.

Daniel L

I added the S2000 to the front/mid engine list of cars.

Chris S

The S2000 and Corvette certainly don't out-handle the Elise, Cayman S, or a Formula 1 car. Mid-engine design is still the best route to optimize handling when you can sacrifice other practical considerations.

Axel6

A mid-engine design affords a very low polar moment of inertia, since weight is concentrated toward the center of the car rather than at the far ends. Many of the greatest race cars and sports cars have had this configuration for decades.

I recall calculating suspension parameters when my SAE team was designing our car in my senior year, 1995 (shit, I'm old). The advantages on weight transfer with a ME design far outweighed any other configuration that we looked at.

rockville

The "front-mid" classification is really more a marketing ploy than anything else. Basically the front-mid design is similar to a traditional front engine design. While it is often a good design practice to get the engine mounted further back in the engine bay/push the wheels further forward, it's not substantially different than a non-front-mid car. Also, some cars could be classed as front-mid depending on engine choice. Both the Jeep Wrangler and older BMW 3 series were offered with I4 and I6 motors. The shorter I4 motors were behind the front axle line. The longer I6 motors were not. So technically they were both mid-fronts when equipped with the base motor.
The reason why I mention this is because a layout where the engine is in front of the passenger compartment is largely similar regardless of whether or not the motor is 1" in front or behind the front axle. The engineers don't make a big fuss about the classification, the marketing people do. Also, historically many/most of the really old "front engined" cars were actually front-mid by the definition above. In all these cases we are basically talking about longitudinally mounted engines.
On the other hand, there can be significant differences when looking at the rear vs mid-rear configurations. When we are looking at a transverse drive the difference may not be much. The difference between the location of the engine crank and axle centerline might be just a few mm (75mm for the Ford MTX-75 used in that V8 Atom on pdcars.net). However, when we look at longitudinal drive lines such as Porsche's it makes a big difference. One puts the engine in front of the gearbox, the other puts it well behind the gear box. That is why people started talking about the difference between rear and front engined cars. BTW, in most racecars they just refer to it as rear engine even though almost all "rear" engined race cars were "mid" engined based on these definitions.

Keep in mind, while the design philosophies behind each of these layouts is real the devil is always in the details and saying one is better than the other because it's A or B just doesn't mean much.

waltk88

It's not just straightline. Follow a well driven 911 around a track and notice how well it puts down power out of corners.