Vetluver

This is a question for the physics whizs out there. I know that the new M5 has 507 bhp and 384 lb.-ft. of torque and the E55 has ~495 bhp and 515 lb.-ft but how do two vehicles that weigh the same have similar performance.

I would think the flatter torque curve of the E55 would be advantageous. Does it have to do with the extra 1000 RPM and less shifting or gear ratios?

Mardeth

Because the shorter gears compensate for the loss of torque.

M&M

Hey great topic! I think 1stly on has to understand that its torque/weight ratio & not outright torque that matters.

2ndly having a lot of torque on your engine sitting on a bench doesn't help anyone. Its what gets to the wheels that matter. So a more efficient drivetrain will get more torque to the wheels. Torque convertors rob you of more power than a manual tranny.

Also, having loads of torque meane much beefier drivetrain components are needed. After all, most parts are rated for a certain torque rating. You need beefier gearbox, diff, etc to handle 500lb/ft vs 250 lb/ft. That in turn leads to more drivetrain loss.

But the biggest factor in torque to the wheels is gear ratios. After all a gear ratio is a torque multiplier. If you have 300lb/ft & a gear ratio combo that works out to 1.5 you will be getting 450lb/ft to the wheels. A car with only 220lb/ft but a gear ratio of 2.0 will get 440lb/ft to the wheels (Very crude mathematics but its just to illustrate).

Latly, one must take in to account torque to the wheels in the rev range where racng takes place, typcially the last 2000rpm of you rev counter. If your car revs to 6500 then after 1st gear you will generally never see anything below 5000rpm unless your gearing is VERY long.

A car that revs to 8000 will hardly ever be below 6500rpm. So one must compare torque to the wheels of car A from 5000-6500 vs car B's 6500-8000rpm. If you have a big capacity V8, root type S/C or a car with small turbos, you will generally have a power drop-off at high rpm. The NA car might not be able to compete int he mid-range but generally it will hold its torque to redline better than a FI car.

To illustrate all the above concepts check out the NA Ferrari vs CL65 in the rolling runs where generally torque tends to rule:

M&M

To understand the torque concept look at the "ELaztisitat" section.

It means elasticity in gears 4/5/6 starting from 80 km/h (50mph):

Check out all the runs but let's look at the longest one.

Put both cars side by side in 4th gear at 50mph. Apply full throttle to both cars until you reach 180km/h (112.5mph). So 50-112mph is quite a long drag & starting in 4th gear means low revs. The more powerful car HAS to work its way to the front on such a long drag.

But check out all the other rolling runs to get an appreciation for what factors matter on the road.

Improviz

If your theory was correct, it should hold true at all speeds, not just rolling-start. I suspect that there is another possible explanation for the elasticity figures there:

The 612 is not an automatic; the CL65 is. I can promise you (from experience) that if I manually shift my car into fourth gear at 50mph and stomp it, the car will ignore me and downshift into second gear, go to redline, shift to third, go to redline, shift into fourth, go to redline, hit the rev limiter, and stay there.

So unless the CL65 has a dramatically different shift program in its ECU, I would expect it to exhibit the same behavior, meaning that it would not be possible to perform this test under true full-throttle conditions. I would think that this would also hold true in the CL.

Perhaps a CL65 owner could comment to this, but in my AMG, one could not perform this test at full throttle.

The 612 would not have such a limitation.

Imo this would explain why the CL65 kills the 612 in a proper acceleration run, but loses in this one. If the 612 could beat it so handily in gear under full throttle conditions, it would beat it from a dead start as well.

M&M

Well the CL65 has more HP than the FErrari & that's why it beats the Ferrari. After 100mph its extra hp starts to pull a big gap. Lots of people are crediting torque for the victory but actually its the hp. It's always HP that wins at high speeds.

On the rolling runs I can guarantee its the gearing. When the CL65 is at 50mph in 4th, whatever revs its at I can bet the Ferrari is at least 1000-1500rpm higher.

Improviz

Based upon my experience, I doubt that the CL65's computer will allow the car to hold fourth gear at full throttle from 50 mph. I will post on the CL55/65 forum to see if anyone with a 65 will try this, but I don't think it will work.

Mardeth

Based on those numbers the new M5 actually beats the CL65 for 0 to 60 and their equal to 124mph.
Pic:
http://www.m5board.com/vbulletin/att...achmentid=2862

Improviz

....as can be seen by the following article, the CLS55 pulled the M5 in a rolling-start autobahn race, so the CL65 will run away from it without difficulty. From the last page in the article:

Full Autocar article: CLS55 vs. E60 M5:

The CL65 has over 100 more horsepower than the CLS55.

Bones

You need to read the article again, the gap was 200m when they started so the CLS didnt make 200m on the M5 just maintained it.

M&M

Didn't the self-same Autocar say the M5 pulled 15 carlengths on an E55? They must have down-shifted that time

Improviz

...but even with this, it still means the CL65 should be considerably faster, given its 111 (rated) horsepower advantage, if the CLS55 can tie it!

If you have any doubts, read this:

Improviz

Here's a video featuring a head to head comparison of the CLS55 and the M5. Same 0-100km/h time for both (4.7 sec), the M5 gets to 200km/h 0.7 sec faster, same 60-0 distance of 39 meters.

Mardeth

In my opinion Sport Auto is alot more credible than Autocar. CL65 will obviously beat the M5 to oblivion above 125mph. But under that and until that speed the M5 will be the winner.

reggid

In that article i was wondering how they new the gap was 200m to start with and how they new it hadn't increased or decreased.
Wouldn't it have been better to line them up next to each other, suppose they are only journalists :p and didn't think of that, they'd rather leave a bit of speculation.

back to the original question!

Thrust comes from the RWTQ/wheel radius
RWTQ comes from RWHP/wheel speed.
or RWTQ comes from Torque x overall gearing x mechanical efficiency.

So gear the M5 so that it makes its 500hp while the other car travelling at the same speed and of similar weight,drag tyre size etc is making less than 500hp and you get more RWTQ in the M5 and hence will accelerate quicker.

reggid

i think the beating will start well before 125mph.

reggid

Do you think that it would downshift to 2nd or 3rd if the pedal was floored?
If so wouldn't that mean it would have an advantage?
Or are you saying that it wouldn't have been using full throttle?

The 612 has 6 speeds so its not completely "fair" and that may account for the advantage.

If someone can get hold of torque curves and gear ratios for the cars the answer may be better understood. We are only given data for the peak torque and hp which while important aren't telling us the whole story.

The CL is also ~200kg heavier than the 612 which is almost 10% and that doesn't even include rotational masses/inertia.

Improviz

The latter, *if* the transmission works as mine does. If it has a manual override function which prevents its downshifting, such a test would be possible, but I couldn't do this one in my car (tried it again last night to be certain); I manually shifted it into in fourth at 60 mph on the highway, stomped it, and it promptly ignored me and downshifted to second gear.

Perhaps the CLs have a system which doesn't do this, but I'm still trying to determine whether it does or not.

Improviz

The CL65 has 111 more horsepower than the M5, and our very own treynor owns a CL65. He ran an 11.7 @ 126, bone stock. Nobody is claiming times remotely close to this for the new M5's, more like mid to high 12's.

BoBcanada

I dunno why you still talking about it, M5 is pure performance, and E55 is pure comfort + KICKASS TORQUE UNDER YOUR ***.... If you want a sports car just buy yourself a porsche or Lotus elise... lol

I had my E55 for 2 days drove 300kms and wouldn't change it for anything... It has best design inside and out, I was acctually standing on my parking lot and looking at it for like 5 minutes lol... Even now i feel like go and drive it....

M5 yeah it's fast it's kinda sporty i doubt it will have such amount of torqe as E55, I can overtake any car any time and not even going further then 3500rpms ( and i dont have to press buttons and switches to make it more powerfull) it just jumps ahead... And I had no traction problems at all, even on wet roads... M5 is gonna be fun on a track i agree, Handling wise, Today i took exits with speed from 80-100 km/h and it was just fine...I'm pretty happy with the handling of E55!! It has nice 16l/100km consumtion... And m5 will have more like 22l/100... I think both cars are great in its own ways... Also design plays a big role... Many people dont like the design of that m5, I kinda like the outside, but i just cant stand the inside of that car the lines of dashboard is just plain ugly, for me at least.... I think this comparisons should not even be discussed here... because there's always somthing faster then you... Even if M5 IS gonna be faster I still would love my car and enjoy it as much as i do now!

:v E55 ALL the way!

reggid

People are interested in the different philopsophies used by Auto manufacturers to get performance. Its just a speculative thread on the performance potential of the different philosphies used by BMW, MB and others.

I can't recall anyone making claims that one is better than the other and there hasn't been any slagging off the other in this thread, so its all harmless, and yes there have been enough of those threads.