Re: Your M3 will never do this - The BMW M3 (E30 M3) Forum

I must say it has 10 years since I have replied to posting other than thanking someone for their help... but this one entertains me intensely.

The fact that an WRX fan would log on to a BMW forum to post a video seems to say that you may be trying to establish the position that the WRX is a superior machine to the E30 M3.

The humor here is you are comparing a WRX to a BMW that is 20 years old... seems like comparing apples to oranges... but then again, a 20 year old M3 probably still deserves the comparison.

So, let's see... where to start. From a theoretical automotive engineering perspective the E30 still remains closer to the ideal design than the WRX... but even further, did Subaru build cars 20 years ago? If they did, what was the performance?

Let’s explore for a moment…

The first design flaw of the WRX is (and the vast majority of cars on the road) is poor balance. Fore and aft balance is critical to the driving dynamics of a car. With a front engine car 50-50 is ideal. Why? Basically an increase of 1lb of on a tire does not result in a 1lb increase of corning force. Putting 1lb on a wheel will result in slightly less corning grip. Let’s say… 98% (or 2% loss). If you work the math the best theoretical grip is when all 4 wheels have 25% of the weight. As with every BMW that ratio is within 2% of ideal balance and the E30 was extremely close to 50-50, where the WRX is front heavy. 58% on the front wheels. A sharp stab to the brakes rotates an additional 15-20% more weight forward, breaking the perfect balance, but with the WRX, which is already 8% from theoretical braking, now you are approaching 70% on the front tires. And as we assumed before you lose 2% grip for every 1lb transferred. A WRX is about 3300 lbs, now with a total weight transfer of around 30% (or 990 lbs) out of balance. Adjusted for the 2% of 990 lbs there is 20 lbs of LESS braking force. In comparison the BMW will transfer 20% and weighs 2700 lbs or about 540lbs to the front wheels. Losing 2% to theoretical grip is about 11lbs of LESS braking force. So, assuming the same brake bias and tire size vs weight (providing the same coefficient of friction) the BMW will always stop shorter. Applying the same analysis shows less grip in corning situations for the WRX as well. As a point of interest, this is why Porsches are known for their brakes. They have >60% of their weight on the rear and when the weight transfers the car is close to the theoretical 50%-50%. Of course in the long run the Porsche is a poor corning design because at corner apex and little to no throttle the rear has too much weight. This is why they are also know for over steer (or the rear end coming out).

Second, ah... all wheel drive... the eternal misconception. In the top of motor sports, how many are all wheel drive? That is right... none. Only in rare cases does all wheel drive provide an advantage. Driving in traction limited situations... and in the world of motorsports (or daily driving for that matter) this occurs less that 10% (higher if you life in Seattle or a lot of snow…) of the time (unless you are a bad driver and can't stay on the road and of course rally racing). In a typical race once they leave the starting line most cars aren't able to spin their wheels unless cornering sharply. And at that moment the additional rotation of end of the car becomes an advantage over an all wheel drive. To top all of this off as we all know the biggest enemy to performance cars is weight. The typical all wheel drive components weigh an additional 200-300 pounds. Turning, accelerating, and stopping an additional 200-300 pounds will lead to slower times and more tire wear. So... from a drive train perspective an all wheel drive system is an advantage at the starting line and only if it rains or on dirt. So, for the other 95% of the time it is an inferior design. If you don’t believe me tune into Cart, Indy, F1, Nascar, Sports car racing, Lemans… watch for an AWD listing. It will be a long trek. Said simply, if two otherwise identical cars are raced on a dry day and one is a 2 wheel drive and one is an AWD the 2 wheel will win… hands down.

Third, polar moment of inertia… I’ll keep this one short… spin in a chair – put your legs out. The rotation will slow (same for ice skater). This is because the further the weight is from the point of rotation the more energy it take to rotate it. Or in car terms, the more grip from the tires will be needed to turn the car. This is why the fastest cars (F1, Indy Cars) cars have engines mounted in the middle of the car. In an F1 car the driver and engine are as close to the rotation point in the car as possible. Of course this does not fit the real world all that well if you need more than 2 seats. But in relation to this discussion, all wheel drive (poorly distributed weight) and the poor balance of the WRX necessitate more grip when turning.

Point 1 and 2 also explains why ALL front wheel drive designs are inferior… Poor balance and a heavy front end (along with the front wheels doing the accelerating, turing, and stopping) will never compete directly with an identical car that is a rear wheel design.

Fourth – BMWs middle name – Motor. The purest of all automotive designs is the engine… and just go to Google and type “BMW engine design award”. Go here for a sample http://www.leftlanenews.com/bmw-straight-six-v10-sweep-engine-awards.html
Let me explain this in as few of words as possible. The one measure true measure of an engine design is simply HP per Liter. Designing an engine with 100hp / liter of displacement is a engineering feat. Meaning a 5 liter engine making 500hp is remarkable. The 3.2 liter M3 engine making 333hp is outstanding. Start looking at car specs and see how many reach this level, and still warranty the engine. Now, you might be saying the WRX puts out 300hp for only 2.5 liters. Wow… that is 120hp per liter. Well… here is the thing… any car company can put a turbo charger on an engine and make HP per liter. This is cheap HP. A good way to summarize the engine design differences is the BMW is engineering HP, the Subaru is something a typical mechanic can bolt on in a day. To take this to a bigger discussion, look at the latest Ford GT and Chevrolet Corvette engines. The only way they are able to get the output to compete with better designed engines are superchargers. Not to take away from their effectiveness, but given the same displacement BMW as the new corvette and they would make the same output (640hp) with a normally aspirated engine. It is like buying a lawn mower engine with a turbo. Heavy components, low rotational speed, low compression, poor intake and exhaust efficiency, etc. But bolt a turbo on it and wow.. it performs.

Specifically to this post when the E30 M3 was originally sold to the public it was the highest HP per liter car sold on the planet. At 87hp per liter it still outperforms the vast majority of engines sold. I have spent a few weekends, and few thousand dollars and I am producing about 280 HP from about 2.4 liters. That is about 117 HP per liter. About the same as the specific output of the turboed WRX. How BMW does this is no secret… a little research will open your eyes.

Interestingly I was watching a motorsport history documentary and they stated that as soon as the Germans were defeated in WWII one of the first orders of the English government was to get a BMW inline 6 and reverse engineer it… enough said.

You’re probably getting by now that a cars performance numbers aren’t all there is to respecting a car. So even with a car as poorly designed as the WRX, to use your words, “anything is possible with the right amount of $$$”.

In closing I will pull a quote from Wikipedia “Having won more road races than any other model in history, the E30 M3 is considered by many to be the world's most successful road-race car.”

Signed… know your facts before you cast the first stone…

Richard