AWDman

anyone know?

this will have a (prob big) impact on drag and circuit racing times.

any info will be appreciated.

thanks.

Vomit

I know this sounds strange, but I think that a shorter rear end actually might hurt your 1/4 mile times. The reason being that the launch is very difficult with the stock C32. With a shorter diff, 1st gear will be even more useless. Also, stock the car shifts to 4th just before the end of the 1/4 (at about 103 MPH). If you put a shorter diff in, you will just be doing that much more of the 1/4 in 4th gear, which is not a good thing. Not to mention that, IMO, the car already over-revs at reasonable freeway cruising speeds (high 70s, low 80s)

I actually would like about a 10% taller rear gear.

AWDman

found a 3.27 at MKB.

Vomit i think you are wrong.....i will try to dig up the car and driver test of the slk55. it was faster than a c6 vette with 400 hp and lighter weight simply due to the mechanical advantage of lower gearing.

Fifth Ring

Was the SLK a seven-speed? That has more to do with the engine remaining in it's best rev range and less to do with lower gearing. Personally, I think the huge gap from 2nd to 3rd gear is the real weakness.

AWDman

Hey Greg. max power for 5.5 na motor is 5750, redline is 6700 which is almost 1000 rpm past peak- power is tapering off rapidly.

i don't think there's a significant gap -I took a look at ratios for the 7 speed vs the 5 speed and calculated the overall gearing and rpm at entry in next higher gear.
7 speed- to redline in 1st, then upshift into 2nd at 4375 rpm -to redline, upshift into 3rd at 4494, into 4th 4782 rpm, into 5th 4893 rpm, 6th 5495, 7th 5950. (last two are overdrives).
5 speed- to redline in 1st then upshift into 2nd 4088 rpm into 2nd, 4310 into 3rd, 4756 into 4th, 5539 into 5th.

granted the slk55 is lighter than the c55 (but c55 has a Cd of 0.27) still the 1/4 goes by a good bit faster (almost 1 sec?) so that's gearing.....(?)

does anyone know the 5.5 na power output past 5700 rpm?

edit- the mkb diff includes a lsd

PunisherZX12

I think a higher RPM Stall converter would help the launch a ton. Something that is computer controlled and would let us select what RPM to launch at.

I may be just dreaming.

Zeppelin

Why spend all that money on shorter gears if it is just for drag racing. Just get some 15 inch rims and mount some low profile drag radials. That will give you lower overall gearing. While your at it spray a 150 shot of nitrous

Vomit

You may be right. My opinion was based only on my observations from 30 or so 1/4 mile runs with the car. My biggest problem was the launch. . . way too slippery off the line. . . and the finish. . . don't like to end the 1/4 in the bottom of a gear.

I am sure that it depends on track conditions. With a sticky track, lower gears would help. With a slick track (like Carlsbad, where I always ran) the prob was getting out of the hole.

AWDman

yep. was thinking the same thing. discount tire has a few 15" rims that would work. don't know about drag racing but hoosier makes a road race tire that would lower the overall gearing ~10%. would have to go to dyno mode to drive tho.

.......also re gearing....the 7 speed auto c350 is as fast as the 6 speed manual despite the more lossy auto tranny.

N.M.M.

Just a little info so someone doesn't go out and purchase a pair of rims only to get pissed off and yell at there dog later that night. The smallest diameter rim to fit the C32 is a 16".

Vomit: Carlsbad was a slick track but I always had a lot of fun there! Too bad they shut it down....

N.M.M.

Just a little info so someone doesn't go out and purchase a pair of rims only to get pissed off and yell at there dog later that night. The smallest diameter rim to fit the C32 is a 16".

Vomit: Carlsbad was a slick track but I always had a lot of fun there! Too bad they shut it down....

AWDman

can't fit 15 inch rear? No good?
NMM are you saying there are 16" that can work in front?

N.M.M.

Im sorry let me be more clear. 16" will not fit the front of the 32. The smallest you can go is a 17". Also a 15" will not fit the rear of a C32. The smallest you can place on the rear for some drag rubber is a 16"