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Originally Posted by mindgam3
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Originally Posted by lakatu
Are rear engine designs fundamentally flawed
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The answer to that question is yes they are. An ideal sports car has perfect weight distribution and minimum overhang fornt and rear. Overhang being the part of the car in front of the front wheels and behind the rear wheels. Porsche does not have this as the engine is situated on the rear axle which should upset the balance of the car.
Its not just the rear engined cars though, in exactly the same way front engined cars are flawed as they have most of their weight over the front axle. However front engined cars can minimize this by having the gearbox placed at the rear.
The reason porsches are so well balanced are.... well thats porsches secret and the reason why you don't see many other rear engined cars.
What does help the rear engined porshce though is the fact that they use flat configurated engines. This means that the pistons are placed horizontally. The two big advantages of this are that 1. it reduces the centre of gravity - the lower the centre of gravity of a car, the better it will corner. And 2. flat configurated engines produce next to no vibrations which means that it will not affect any other components around the rear, for example suspension which also helps the handling.
Rear engined cars also have good traction as they accelerate. This is because as cars accelerate, most of the weight is transferred to the rear. The more weight you have their in the first place, the more grip you're going to get when accelrating.
This has the opposite effect when braking - the front has most of the weight transferred to it and the back will go light. As most of the weights at the back, the car becomes naturally unstable.
With cornering, as the weight distribution is not perfect, as the fron wants to go around the corner, the back end will want to go sideways.
These are the physics of a rear engined car and you cannot change the,. What porsche have done is minimise the disadvantages of a rear engined car and maximised the advantages. This is why porshces handle so good and not many people attempt to make rear engined cars.[/img] |
Excellent post 8) . I really appreciate your thoughts and feedback. I have been patiently awaiting some discussion about the post and appreciate your contribution. I was kind of hoping that others would posts their thoughts about the subject in a similar manner as you’ve done. It is obvious that you are knowledgeable about the handling characteristics of cars. Especially as it applies to weight distribution.
BTW, I notice that you are relatively new to JW and I wanted to extend a welcome. It is great to have members that provide intelligent contributions 8) to our discussion here at “Porsche Central”.
You make some good points. Several of which I was planning on covering in later posts. Specifically, the points about lower center of gravity with the boxer engine design and the higher polar moment of inertia of having mass located farther from the center of gravity in a rear engine verses a mid engine design. To be honest I have never considered the smoothness of the boxer design and any effects this would have on stabilizing handling verses a more vibrating design.
My point of the posts is that the design isn’t fundamentally flawed :roll: . To be honest I have some basic concepts in mind and I have been doing research to pursue these thoughts. At this point I don’t know if I can make the case that the rear engine design is the preferred design. Maybe somebody else can help me make that point
. At this point, I think that if the rear engine design was the best solution that it would be utilized more in racing designs which are almost exclusively mid engine as far as I know. Another point that seems to indicate that the rear engine design may not be the preferred design is that even Porsche’s own two latest designs, the CGT and Boxster, have been mid engine designs.
My point is that the rear engine design works well and provides advantages to its drivers. With most things in life there are tradeoffs and the rear engine design does have them but I believe that racing experience has shown that they can be utilized to more than offset its disadvantages.
BTW, another way front engine cars shift weight towards the rear, other than a transaxle, is to locate the engine behind the front axle. This is used on the Corvette and M3. Another benefit to locating the engine behind the front axle is it also lowers the center of gravity as it doesn’t have to clear front suspension structures.
To anyone else who is thinking of contributing, please feel free to add your comments 8) . I’m not worried that some of the discussion will get ahead of points that I was planning to make in later posts. As I’ve stated before, I am interested in the subject and am trying to work through the issues, so additional points of view would be helpful
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