Changing the final drive ratio...

550 GTO is soon the new sheriff in town....

 

Little update on speed/revs....

I have just now driven from Nice to Oslo with a 2010 Mercedes E200CDI estate loaded with stuff and the dog. This car weighs in at two tonns now, has much more aerodynamic drag, has a 2,2 liter diesel four cylinder with 150 hp. Not exactly a rocket ship, but it is a solid one owner car with 581.200 kms. Original and never tuned or rebuild. (My dad never exceed 3.000 rpm.....)

This car can cruise at a contnious 200 kph. @ 3.600 rpm. And it is quite comfortable too. I can’t see any reason why my 5,5 liter 485 hp. V12 shouldn’t be able to do the same! The little 2,2 liter diesel with much more drag can do it with exactly 1.000 rom. less than my Ferrari....... go figure!
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6,5 is not representative for that speed... I average less than 200 kph. of course. I can cruise at that speed but it is too much traffic and lots of road work on the A7. It all depends on how much traffic it is and the weather conditions of course. People drive to work at 200 kph. in all kinds of cars. Technology have moved a lot forward the last 10-20 years. Even VW Golf, small Peugeots and simple Skoda cars cruise economically at these speeds now. The Germans have excellent driving style. Not one single car pass on the right side. Very important so that the left land is always free if possible. The traffic flows fast, and people are focused on the driving because of this, while in many countries and especially Norway, the traffic goes so slow that people almost fall asleep and use their phones for texting etc.... To go legally at these speeds in a controlled manner is quite an experience. Who know when it will no longer be legal?

I don’t know about the amount of torque on the 200 CDI, but as max output is 150 bhp, I assume I take out about 120 hp. to get 200 kph. It tops out at 210 actually. But 150 hp on a 2,2 liter engine is not much and Mercedes take out much more in their more powerful variants of the same block, so I feel it is quite safe to let it work like that.

The this is that with the low revs at say 130-180 kph. on the cruise control, it is like you can run forever without being tired or having to refuel. It burns 7 liters/100 kms. at 160 / 100 mph. Quite impressive and diesel fuel is 10-20 % lower cost too. So at best, it cost 1/2 of a 550 when the 550 runs only in the 110 kph. speed and all other cars will overtake you, which is not fun or safe. Fuel is not expencive in the US, but if I say I save over 1.000 dollar on a round trip like this, my imagination goes into what I could do with these money of course...

Of course the V12 will fly effortlessly at much higher rpm., but the stress factor inside the car is higher. I am 100% sure a new ratio on the differential will be excellent, because the longer ratio will be much more noticable in the higher gears. The 550 is very low geared in 1st. It’s like you can just release the clutch without any throttle. It puls like a train even on idle. Let’s say 20% longer ratio at start in stop and go traffic will hardly be noticable. The car can be put in movement from standstill in 2nd and even 3rd if you have to. But the longer ratio will be more and more noticable the higher gear you choose.... Which is quite ideal as the rpms. will be the same as before everytime you change into a higher gear. It is just that the car moves a longer distance per 1000 revolutions. If a new final drive gear gives 19% less revs., the new 5th will have exactly the same total ratio as todays 6th. I have been thinking of it the whole trip. Even if the torque peak is at 5.000 rpm., it should have plenty of torque for the 130-240 kph. speed range. Arrest me if I am wrong.

 

Hi guys!
I have again been in contact with the supplier in Modena who can make a new ratio that will make the 550 and 575 + 612 too more relaxing while going fast. The amount of sets made is very important for the price per unit of course. I am always looking for the 7th gear when going on the freeway. Especially with louder sports exhaust it makes no sense to be cruising at high revs if it is not not neccesary.
WHO WOULD BE INTERESTED IN MAKING THEIR CAR MORE LONG TRIP FRIENDLY?? We can get whatever ratio we want. 11% longer radtio in the differential will make 5th the same as 6th today. So this will give the exact same performance for top speed. 6th will be the «overdrive gear» for fast cruising. With new headers and more power, maybe an increase to 12-13% also would be favourable.

Erik

 

Hi Nick. You are king of performance. And your 575 is a beast. However, my car is more used for higher speeds than you can do in America. I have driven there myself for about 30.000 miles from Cali to Key West and up to Boston. The traffic goes quite well at 85-90 mph. most places. In Europe we drove about the same speeds or a little bit faster. In Germany the traffic goes quite alot faster of course. When you get used to 130 mph. in the Maranello, you can drive like that for houres. It is just that you want less noise and longer range between every fill up. The 550s are quite a bit more noisy than the 456M and 575M because they have no rubber in the upper end of the shocks. I also feel that after I got some more sound in the exhaust, the «comfortable» cruising speed have goen down a bit. Modern cars today are more comfortable and have a lot less rpms. Even Ferraris and Porsches of more recent years have a longer ratio and less rpm. This improve the ability to drive long distances very fast quite alot. This is what I want to do for my car. I just need many more to do the same...