Improviz

..as part of their test suite; that way, if something shows up 20-30% higher than rated, it's a bit of egg on the face of the manufacturers!

I just wish they'd tune the *stock* ones like that!! Shoot, that 5.5L would be good for an easy, reliable 400HP without breaking a sweat! Oh, well...it's still a kickass motor!

rogers

IMO I think the clk 55 shouldn't be in this test. IMO they should have tested the CLK500. The other two cars are pure luxury coupes.

moa4r

i'd take the masarati over the benz or the bm any day

Stiggs

So are you guys saying the CLK55 they tested isn't a bone stock car? Does my CLK55 go 0-60 in 5.0 sec or 4.5 sec??

After reading the article, I feel like they rated my car faster than it really is.

sajecw

That is what I am saying. I am just basing this on real world experience. Bring it to the track and test it.

Ebrigham

Me too, but I guess that much is obvious...

where the he(( is my C&D???

rev

I'm a little surprised that they were able to get that 0-60 time for the 209 with the stock rubber, especially with the 3.06 rear axle and the 3.60 1st gear ratio?

Anyone know what the corresponding 5-60, 30-50, and 50-70 mph times for the "stock" 208 CLK55 are? Any links?

shoes

Car & Driver also got the SL600 to 60 in less than 4 seconds. Maybe these guys are burning something hotter than gasoline?

moa4r

i believe it was 3.6 seconds i agree their reports and comparisons are thats y i don't bother buying it anymore

AMG///Merc

Out of curiosity, if MB did indeed provide Car & Driver with a ringer, what do you think would they have done to improve the performance of the car? I know that it used to be that manufacturers would just take an off the line and balance and blue-print the engine, but being that AMG does that from the factory and that each motor is checked on the dyno to ensure that it is producing its full output. So in order for there to be a "ringer", it stands to reason that they must have changed actual mechanical parts such as the cams, which I think is unlikely. What I think, is that they ran a fully broken-in CLK, under ideal, or at least near ideal conditions. I don't think that it's entirely impossible for there to be a half-second or so variation in time due to track variables. I think the days of the "ringers" are gone, and that it's just too tricky and far too costly for the manufacturers if they were ever caught using a "ringer". If it's well known that the kompressor motors are under-rated, is it impossible that the NA 55's are as well? Also, while I can't remember where the article is, nor do I remember it well enough to explain exactly how this was, but I did read an article written by a BMW engineer that explained how the M3 was faster than what the dyno numbers would suggest, and I suspect that the same thing might apply to the CLK55...



Best regards,
Matt

Improviz

....as I pointed out: GM gave a GTO to the press in the late 60's with a full race motor bolted in, and there were numerous other instances of cars from that era being massaged before being given to the press.

How to improve it? Shoot, this motor would be very easy to tune! It's only at about 63 hp/liter, and wouldn't take much in the way of intake (heads, whatever)/exhaust mods to net another 40-50 horsepower.

The point is that if you take that equation provided by Road & Track and run it on the other two cars in the comparo, they're about ten horsepower above rated; the Benz comes in at 34 above rated. And the CLK500 Road & Track recently tested came in at almost 50 above rated! The previous CLK500 they tested came in right at rated horsepower.

It sounds weird, but the equation works. Here are some examples:


Let's try it on a few other cars Road and Track has tested:

2002 Z06:
As-tested weight: 3295
1/4: 12.5@116
Rated hp: 405
Calculated hp: 401

2004 Porsche GT-3:
As-tested weight: 3340
1/4: 12.4@114
Rated hp: 380
Calculated hp: 386

2004 Cadillac CTS-V:
As-tested weight: 4070
1/4: 13.4@109
Rated hp: 400
Calculated hp: 411

2004 Pontiac GTO:
As-tested weight: 3950
1/4: 13.8@103.8
Rated hp: 350
Calculated hp: 344.7

BMW M5:
As-tested weight: 4040
1/4: 13.3@108.5
Rated hp: 394
Calculated hp: 403

Mercedes SL500:
As-tested weight: 4190
1/4: 14.5@98.4
Rated hp: 302
Calculated hp: 311

Here's a link to a horsepower which uses this equation. . Try it using the "calculate using speed" for crank horsepower, or the "calculate using ET" for wheel horsepower. Weird, but it works pretty well, except for these mysterious new Benzes.

Now with the E55k and the other supercharged/turbocharged motors, I accept that they're underrating them substantially, having seen dyno numbers and dragstrip results which substantiate the mag tests. But I haven't seen this with the CLK500 or 55 yet, and until I do, I'll remain in the skeptical field. Hey, if they are underrating even the NA motors, great! I'm just cynical, that's all!

Stiggs

OK...here's what confuses me. If you turn to page 145 of this car and driver issue, you will see the list of cars they have tested in the past. Its called the "road test digest".
Listed is a CLK55 :

month tested = 11/03
price as tested = $82,025
0-60 = 4.7sec
1/4 mile = 13.2 sec
top speed = 156
braking, 70-0 mph = 173 feet
road-holding = 0.80 g
EPA city = 15 mpg




Now these numbers don't all jive with the most recent test. So what gives? Damn it, who knows how fast this car goes!!

Thai

Different driver, different surface, different road, different elevation, different temperature, etc.. That is why you should not compare numbers from two different tests. The ONLY reliable way to compare is in a multi-car comparo where 1-2 drivers test the same group of cars on the same test.

FrankW

the only thing I have to say about that is even for the same test, the magazine guys does not run both car at the same time. it doesn't guarantee the same condition as well. They can have multiple tries till they get the number they think it's the fastest.

every magazine should do what the TopGear is doing on their test which they line them up and race'em head to head to see who's the man.

Improviz

...the reason is a little thing they teach in statistics: variances.

This means that in every process, including the production of engines, transmissions, gears, tires, etc., there are variances in the results of the process. For a given motor, for example, the horsepower rating is an average, meaning that of a given sample of engines tested, if you average the horsepower of all of them, this is the number they'll hit. Some will be higher, some will be lower, but very few, if any, of them will be *exactly* at the rated horsepower.

They have pretty tight tolerances, but a variation of even 5% is pretty significant when you're talking about engines in the vicinity of 340 horsepower; 5% of 340 is 17 horsepower. So, for example, you might have one car running its rated, while another runs a certain amount above its rated, a third runs below its rated, etc...

And this is only engines. Transmissions will vary in their efficiency; some will drain more power, others will drain less. Some tires will give better traction than others, etc...

So, even if you lined up three M3's on the same day at the same track and had the same driver test them, the chances that they'd all hit exactly the same times are just about nil.

These tests are just a snapshot of one car on one day with one driver; the thing to keep in mind is that not only are weather and track conditions variables in the performance equation, but also the *car itself*. All one needs to do to verify this is to examine several road tests for a given car, *although* as Road & Track recently admitted, they will sometimes use data from a prior test rather than retesting the car...if the numbers are identical, this is what they've done. No two cars are identical...

Also keep in mind that different mags test different ways; Road & Track uses the averages of several acceleration runs, while others may be using the best times. But even with a pro at the wheel, there *will* be significant variances from run to run; this is why averaging is useful, as it "smooths out" the runs...this should hopefully be the midpoint for what a good driver will get, with some variation in either direction...

Particularly with manual transmissions, the variances are larger, because humans are generally not as consistent as machines are...so, if you take a manual-trannied car to the strip and do some runs, unless you are an absolutely fabulous driver, you'll see variations of 0.5 seconds or more from your slowest to fastest runs, and very likely more than that.

Auto mag tests are good for general benchmarking, but they certainly don't provide a "golden" figure, only *a* figure to measure its performance capabilities...especially with these new high-horsepower cars that are pretty tricky to launch, and with the manuals, time the shifts when the redline is *very* rapidly approaching!!

MidniteBluBenz

Will someone scan the Road & Track article from this month, where they compared a CLK500 and a 645i.

R&T managed 0 - 60 in 5.2 and 13.7@10X.XXmph in a CLK500.

These times were equal to or greater than the times for the 645i.

4.5 seconds sounds about right for a 209 55. There are many plausible explanations for the 0 - 60 and q/m times of recent Benz's. Their V-8's have a lot of torque or Benz maybe underrating their engines. For those who don't believe in the effects of torque, a E320 CDi with 201 hp is almost a full second quicker to 60 than a gasoline E320.

I don't think that MB is sending these mag's 'ringers'. If you've ever looked at Car and Driver long term tests of Benz's, the 0 - 60 times drop almost a half second on average after the engine's been broken in. (A '97 E320 did 0 - 60 in 6.7 at the end of a longterm test)

Improviz

...but the CLK500 produces far *less* torque than a CLK55, and yet now we're supposed to believe that it can run the same 0-60 and only 0.1 off the W208 CLK55's 1/4 mile time, despite weighing 100 pounds more, having almost 50 fewer horsepower and lb-ft of torque, and the same final drive ratio and gearing?? I don't buy it.

There are four published tests I've seen for the CLK500; EVO magazine in Europe, Car and Driver, and two by Road and Track. Results:

Car & Driver:
0-60: 5.7 1/4: 14.2@

Road & Track:
April '04: 0-60: 5.20 1/4: 13.70@
Dec. '02: 0-60: 5.80 1/4: 14.3@101.6

EVO magazine, 0-60: 6.0 seconds.

As you can see, the lone standout is the latest Road & Track test.

Also, MotorWeek tested a 209 CLK55 at a 13.7@104, whereas they got a 13.4@107 in the 208 CLK55 they tested.

Also, as I pointed out (see previous post in this thread for link to it), there is a horsepower calculator available which is extremely accurate if you use the vehicle's as-tested weight with driver and its trap speed in the 1/4. I also gave examples of several other cars where it was almost perfect, yet the new CLK500 in that Road & Track test and the CLK55 in the new Car & Driver are calculating out at 50 and 34 horsepower above rated, which is also suspicious.

Torque-wise, the 209 CLK55 engine's rating hasn't changed from the 208's. Horsepower is up by 20, but the car's weight is up by 200 pounds, which nulls it out: weight/hp ratio is the same. Gearing has changed slightly, but gearing won't increase your trap speed; only a decrease in the weight/horsepower ratio can do this.

So yes, given the above, I'm suspicious...those horsepower/weight calculations have been used for years in drag racing circles, and are pretty reliable. Try it yourself; the link is on previous page. Just remember to use the as-tested weight (if available; if not, add 180 pounds for driver/equipment) and the weight w/ET calculator.

MidniteBluBenz

Improviz,

You're point about the CLK500 vs. 208 55 makes sense, but the times for the 645 were about the same in Car and Driver and Road & Track. Only plausible explanation is that the CLK may have been broken in well and some other situational conditions were conducive to achieving 0 - 60 in 5.2.

Part of why the 209 55 may be so much faster is that the car is redlined at 6700 vs. 6000 for the 208. Although the 208 and 209 have the same final drive, Speedshift, or whatever the AMG box is called, may also play a part in the 209 being so much quicker.

Thai

Now, that makes a big difference!! Improv, there's your answer. So, MB did not just increase the HP, they also stretch out the power band...more power in each gear!

Improviz

And the only way that'll happen is if the torque curve is phattened out so that the higher rpms can produce more horsepower.

But if you look at the following power vs. torque curve MB provides for the C55, (same engine as CLK55), you'll see that horsepower peaks just shy of 6,000 RPM, so added revs obviously didn't give it a horsepower gain. Torque curve falls off too rapidly...

This is a hard and fast rule of drag racing: if you wanna increase your trap speed, you haveta increase your horsepower. Gearing and higher redlines can help ET, but they won't increase the speed.

Having said that, it's pretty well known and accepted that MB *is* dramatically underrating the horsepower of the 5.5L Kompressor and 6.0L turbo motors, but the difference there is that *all* of these publications that have tested them have gotten trap speeds indicative of elevated horsepower levels, *and* owners have duplicated, and beaten, these results in stock cars. If I start seeing a bunch of timeslips from 209 CLK55 owners showing 109 mph trap speeds, I'll certainly be changing my mind, but so far I haven't.

The one 209 whose results I've seen so far is Amil's; in seven runs, he ran a best of 14.12 at LACR (which due to its altitude has an ET correction factor of 0.9679 to get sea level times)

So, his best run altitude-corrects to 13.67. His three best runs averaged out to 14.17 for an altitude-corrected average of 13.72. I don't know his trap speed, but I'm betting it corrects in the 104-106 range with that ET, which indicates that it is producing its rated hp, not 10% above it.

So, dangit, some more of you 209 guys need to get out to the strip and get some timeslips before it gets too hot outside!!! Let's see how those babies can do!

Thai

Yeah, i would "assume" that if they raise the redline, then they would also flattened out the torque curve and hp would continue to rise. Oopps, nevermind. I guess that it's still a mystery.

Yeah, i think that CLK AMG owners are not very aggressive people when it comes to tracking their cars (i am not either)...and W209 is still new on the market.

Back to the drawing board....

CRB

I finally got my Car and Driver yesterday and that was the most lukewarm "review" of a winning car that I can remember. First place in name (and speed).

AMG///Merc

I just figured that I would confirm that...


Best regards,
Matt

Thai

I am confused! Why did AMG increase redline if the HP peaks at 5750???!!! That is a waste of rpms! Wouldn't that actually make for slower acceleration because you are actually losing power past 5750??

Improviz

...it really wouldn't make much sense to have the redline that high above the power peak...

But it might not be so crazy after all: I did a quick run using the numbers from that MB chart, and converted the torque in nm to ft-lb; they don't have the hp above about 6,300 rpm, but they list torque out to around 6,500 rpm, where it is 375 nm, which translates to 276.6 lb-ft.

Horsepower = torque*rpm/5252, so at that rpm, the engine is producing 342 horsepower according to the torque...not bad! It won't increase the trap speed, but it would might make the car a bit faster from a roll. I'm not certain of this, though: because of the torque is so much lower, it might be better to go to the next gear, where rpm would be lower and torque would be higher. I'd have to do some digging, and I'm too busy today.

Has anyone with a 209 verified that the car actually *does* shift at 6,750 rpm??? That's a pretty substantial jump in RPM, and I know that the new E55 shifts at 6,500.