jangy

Looks like I will be playing with gearing and Serge has me talked into a separate setup just for drags, since I really don't want an AMG that max's out at 120 (hint JIM).

Is making any change going to be huge? I was on the quest for top end, since I keep getting left by Blue Monster's E55 at the top, but gearing is another thought. Right now, my car is a monster in the dig. I still haven't seen many cars I can't get a half to full length on just at the jump, but it is a complete different story when Ed's E55 stretches the legs (at about 4 paces). I've gotten closer and I hope cooling will top it off, but it has been a long run. That car was killing mine when I had the RennTech stage 1. Now, he still pulls on me pretty solid, but I hope cooling will help.

If I do gearing for 1/4 mile ets will I lose any hope of having a 150mph blast? I love top end too much for that.

bobgodd

Any "benefits" from gearing will be felt at all speeds, and in all gears, which may or may not be a benefit to some folk. Way back when I had my Z28 I changed the rearend gearing from 2.73 to 3.42 and the difference was awesome, the car had a lot more pickup and acceleration at any speed and in any gear. This may be a problem with the E though, as it could make getting traction in 1st gear REALLY challenging, as if it wasn't bad enough already.

As far as top end goes, the shorter gearing (numerically higher) will help your car pull harder higher up into the RPM band, but it will top out quicker as well, though not as much as you might think... I'm guessing you'd loose no more than 10mph of top speed. My old Z06 was drag limited somewhere around 175mph for a top speed, but I understand that the E with speed limiter removed, should be able to reach higher than that? If that is the case then you should still have no problem getting to 150mph.

blackbenzz

I've looked into this. In order to get faster acceleration you need to go to shorter gears (higher number). This also means even worse traction in lower gears and more shifting. If you can get it to stick and not break it will be quicker in the 1/4 but you will lose top speed. There are calculators for this. I already have traction problems and its good to know that theoretically the cars gearing is good for 200mph

Max.H

tighter final drive will do the trick. it should be a very straight forward install in the diff. I have thought about this myself. because the gearing for most of these types of cars is for the autobahn. ideally you want tight gearing for a good blast to 150mph and your set. I know of 2 companys that build custom final drives. If we can get a group buy together It should be very affordable.

Jakpro1

Although the change was small. Going from 2.65 to 2.82 in mine did not hinder traction much at all from normal.

I would be curious how much the half shafts will take when you get above 3.06's which the SLR runs.

I just think half shafts will start snapping (snapping meaning twist out of the diff like we have seen already in stockers) when we start launching with gears shorter than 3.23 range. Just a guess though. Maybe she'll work like a charm.

Only one way to find out eh??

Let it rip Jangy!!

Thericker

I went from 3.15 to 3.90 in my old C6 Vette, the new torque multiplication was awesome in 1-2nd gears but deff noticeable drop in acceleration @ 90+ mph, though I still took her to 160+mph on a few occasions. Taller gearing doesn't only LIMIT your top speed it also decreases your perf on the top end as well..

The new lacking top end perf is because when you punch it @ say 70mph your not downshifting to 2nd gear anymore you'll be in 3rd for a second if that, then wham into 4th, you get the picture....Don't get me wrong after a serious gear swap ie 3.40+ range each gear will be quicker than before but like I said once you hit about 90mph you'll see what I mean, you'll wish you had 2.65 - 2.82 again..

Stout gearing will make your car a 1/4 mile bomber if you obtain traction, but 65-75mph freeway roll-ons will leave you disapointed, unless you start from 25-35mph.

CLK Masters

honestly, personally i would want gears 1-4 to get me to about 140ish, and make 5th a really tall gear. i'm really how often to do race people above 140?
this way you can still smoke prettymuch anyone that has the ***** to race to 140 -99.999% of all people- and once in 5th you're getting mid to high 20's for MPG.

bobgodd

I think I get what you're saying: It may hurt racing because it might put you in a different power band during a roll on race... But that is easily fixed, just start from a different MPH. The torque multiplication in the rear differential is completely independent from the engine or transmission; it doesn't matter what speed or rpm you are at, the new torque multiplication will still be there.

bobgodd

That would be the best way to do it, but would require changing the actual gears in the tranny, which probably isn't possible at this point. Would be nice though

Thericker

Yes you can do that, but I can't count how many times I got caught @ say 75-80mph and stabbed the go pedal, it was pathetic compared to stock NO downshift at all.

Jakpro1

Interesting this conversation and then some action today.

Just GORGEOUS weather "somewhere in Mexico today" so down south of the border, up from behind me comes an ISF Lex ready to play.

Walked him but still it really wasn't devastating and I bet he walked away feeling pretty good. We were able to do it on a deserted piece of highway and it really shows how our cars slowly lose their luster above 110-120 range. Especially when hot. We took it up quite higher than I usually do and it's wild to watch our cars start to die up top.

Not really sure of the outcome if I was using 3.23's or 3.56's.

AMGfan

Yeah...they are fast. What elevations are you at though? Considering the IS-F is normally aspirated...the elevation handicaps our supercharged engines, not to mention the weight difference between our cars...