StephenK

From a Car & Drive Magazine

"The leap in engine output is credited to a redesigned intake airbox and reprogrammed engine and transmission computers. Stronger axle shafts have been installed to handle the extra load, and new mufflers provide an improved exhaust note. RENNtech also lowered the car and bolted on larger-diameter brake rotors front and rear and bigger calipers to grip them. The rubber is Michelin Pilot Sport PS2s all around on larger 19-inch forged aluminum wheels. The performance upgrades came to a hefty $33,536. Total cost of the car came to a staggering $174,001."

Could the increased TORQUE be to much for the current SL600 axle shafts. I think that must be the case, or why else would they have installed them?

Overclocked412

Oh no, Not by a long shot. Its just a gimmick more than anything else. more money in their pockets..

sillydriver

I also think it’s unnecessary. The stress on the half shafts (axel) is limited by the adhesion of the tires. I think that even an unmodified 600 can break the tires loose in first gear, which the stock half shafts can handle easily. Beyond the torque needed to break loose the tires, any excess just serves to spin the wheels, jump up the engine’s RPM, and is not transmitted to the road. Also, if the stock half shafts were overstressed, they would break whenever other members of this board put drag radials on their cars and race them on a strip. The adhesion of those tires is higher, so the stress on the axel is greater. So I doubt whether you could break the axel on a modified car that uses street tires.

LovinMercedes

I know many people swear by the upgrade and I really wanted one on my last two SL's and each time my dealer talked me out of it.

Personally, since I have never experienced it I don't know. Others swear by it but it is by no means a slam dunk deal. There are many that question whether it is good for the car.

I am not qualified to make a judgement.

Dernick

I know this is kinda random, but oh well. I'm a 21 year old college student, and I'm basically talking on my parent's behalf here when it comes to theri cars. My mom has an '03 SL500 with RENNtech's supercharger kit on it, and my dad has an '05 SL65. Before he bought the SL65, the SL500 was his car. Right before he bought it, I was talking to my dad's RENNtech mechanic here in town (Houston) about upgrades that they offered, and he was telling me about how RENNtech was dynoing a modified SL65 that was able to 'unofficially' put down 890 rwhp and 1040 rwtq right before the half shafts snapped. He told me that they could install stronger halfshafts but that it'd be extremely expensive for the parts.

vraa

Dernick: As weird as this sounds, got any pics? I love pictures

StephenK

So this is an actual possiblity to have happen with their upgrade. Interesting....

vraa

The RENNtech upgrade for the SL600 R230 will move it to 745lb-ft torque. Still 295lb-ft torque away from that snapping point.

StephenK

Maybe, but remember the SL65 is upgraded as a base car from the SL600 anyways. Seems crazy that Renntech would sell an upgrade that would do that to the SL65.

Bob at Renntech said you would have to be an idiot to damage your car or if you took it to the track all the time. He would never be specific about what could be damaged and why it would happen.

Dernick

The 'upgrade' that snapped the halfshafts isn't available for the public. If I understood the mechanic correctly, it was just them trying to get as much as they could out of the car.

Dernick

Very true.

Dernick

I odn't really have that many pictures of the SL65 but a ton of the SL500. Here's a few...

























The pictures of under the hood of the SL500 (the first two) show how the only think that's 'not stock looking' under the hood is the small pulley that runs the blower. It also has RENNtech 20" wheels on it.

vraa

RENNtech doesn't sell the upgrade to 1040lb-ft torque. The upgrade for the SL65 that they sell (ECU wise) raises torque to 840lb-ft. That's still 200lb-ft torque to go.

Dernick: Those are some really nice pictures. I love black R230's!

sillydriver

I think that the rear wheels had to be strapped down hard against the dyno rollers just to measure that much HP and torque. In other words, traction was artificially increased way beyond what is possible on the street, where a stock SL65 can easily spin the wheels. Hence my comment that the half shafts will be protected by the lack of traction under normal circumstances still applies.