Do any of you tech's know anything about changing the r&p in the xfires? I want to get the 1st gear of my 6 speed to run a bit longer prior to shifting, also giving a higher top end. I did this to my '73 Jaguar and the performance is great. I am thinking the change in combination with the manual transmission will also help every gear performance. Any previous experiences or opinions would be GREATLY appreciated. Thanks again. :roll: :lol: :lol:

 

I'm lost. It's a manual, right? You want it to "run a bit longer prior to shifting", wouldn't you just wait longer before pushing the clutch and throwing the shifter from '1' to '2'???

 

No, when the ring and pinion is replaced with a lower ratio the engine at the same rpm will cause the car to go faster. Its an easy way to solve the quick 1st to 2nd shift that normally takes place. I would have thought Xfire would have thought of this. Did you follow me? Thanks. :wink:

 

You would probably want to swap out the rear end for that. I am not aware of any aftermarket options for the SLK / Mercedes. I'll do some digging today. The SLK doesn't have many performance upgrade options. If you wanted performance, you got the AMG.

Not saying it can't, or hasn't been done, but I haven't found anything yet. Anyone else?

 

As always, thanks for your input. I hope everyone appreciates how valuable this forum is. Thanks again.

 

By installing a numerically lower gear ratio (a higher gear) you would be able to stay in 1st gear longer, but what sense would that make? Performance wise that would be a bad idea. Yes the car would be faster in the sense that it would have a higher top speed, assuming wind resistance or lack of vehicle stability didn't take over at 160mph, but you are going to lose alot of power/acceleration.

If you're doing this merely so that you don't have to shift from 1st to 2nd so quickly, why not just start in 2nd?

 

You would not be starting in 2nd. To explain it easier, it would be changing your shift points, and allowing you to reach a higher speed before each shift. After I get it done I'll let you know, maybe we'll run sometime. :idea:

 

The ECU governs the car to no faster than 155. We can already hit that.

I agree with Heb80.... I wouldn't want to lose that "out of the hole" punch we have now. The only advantage that I could see with going with a taller gear would be that you might get a little better hwy fuel mileage because of the lower cruising rpm.

 

Please don't tell me you think it is going to accelerate faster with a numerically lower gear ratio. :lol:

Like Wes said, your only advantage MIGHT be better fuel mileage, but even that is not guaranteed. You will have a lower RPM, but in turn you will have more strain on the engine. Your gas mileage could potentially decrease since a lower RPM does not always mean the engine is running more efficiently.

 

Depending on how drastic the change is, your speedo and odo will not be correct. Correcting that may require getting into the electronics...argghh, I think that would be a technical nightmare.

A taller rear end...would it be easier to put higher profile tires in the rear? That would change the ratio too...right? The car would look funny though.

 

Taller tires in the rear would have the same affect, but I doubt you would fit anything taller back there, not to mention how funny that would look.

Unless you have a buddy that knows how to set gears and is willing to do it for a case of beer, you're looking at probably around $500 just for labor and another couple hundred for the parts (if you could even find them). Installing gears is not something the average Joe can do... it takes alot of time, patients, knowledge, and special tools.

As for the speedo/odometer, on my other car when I changed the gears it was just a matter of replacing a little plastic gear, but of course the crossfire is probably computer controlled.