Luke_M

I've seen this black Challenger SRT-8 before on the highway home but never got a chance to run for fear of cops and also the fact that he was going 10-20 over the speed limit to start. I guess he enjoys his big cruiser which I can appreciate although I tend to drive like an old man lol

Well I saw him again the other night and was feeling froggy so I caught up and we played around a bit. Had one go from a roll and thankfully he slowed down first, just safer that way. Pulled a bit but I didn't exactly run away although it was only for a few seconds so what do you expect. It was a 6 speed manual which surprised me when I heard it because I thought they only came in automatics. Good move by dodge to offer a manual option.

Next we both got caught at a red light. Nothing but clear road ahead, no intersections etc. Perfect. Aside from the mustangs that are a dime a dozen around here, a new SRT-8 is my next best pick for a friendly run.

I have nearly bald general UHP tires and it was about 35degrees out so it wasn't exactly optimal for either of us but I eased off the line and as soon as I heard the bass from him going WOT I followed suit and it was all over. I can't say exactly how much I pulled him because I didn't look back but when I let off it took a few seconds for him to catch up. I don't think I got him by a shocking amount though. Need more power and better rubber for that. Hopefully next time I see him I'll have a little more in store for him

I was watching this video and a gt500 on paper is about equal with a stock E55 so I bet it looked something like that. I'm hoping after I get my headers and pulley going it'll look more like what that camaro did I might need a TB for that though. I think the 550 means at the wheels.

http://www.youtube.com/watch?v=Lwl2AQ7kwqc

Anyway they are nice looking cars for sure. Best of the SRT-8 series in my opinon. I'm not sure if he was taken by surprise or what. Kinda wants makes me want to debadge this car lol

jturkel

yah you should destroy any Challenger SRT8.......they are slow because they are SOO heavy....and handle worse than a boat.

i've pulled on one quite hard in my C32.

nice kill. and be safe out there!

GT500 definitely quicker than the SRT8.....i would say it would be a pretty good run with stock....i think the E55 might be just a tid bit faster.....but add a supercharger pulley and tune, those things are trapping well into the low to mid 120s.

Deuuuce

Agreed about a stocker.

A 400rwhp tuned automatic will hang decently but still lose from a roll. Figure roughly 3+mph trap speed differential on any given day.

Don't know about tuned 6speeds though, gearing is different and it would have to be driven expertly to lose that well.

Just not in the same league as the AMG and the GT500.

Jons95c36amg

Its because the Srt-8 motors have only 16 valves. So even with a 6.2L with boltons the Challenger,300c Srt-8s will loose steam in the topend against the stock 32 valve 6.3 AMG.

jturkel

yah...and dont get me wrong...i think they look badass....i just wish they would go on a diet or something. lol.

Luke_M

They weigh about the same as the E55, maybe a tad more when you compare published curb weights so it was fair in that regard. But yes, that means they're heavy

The few MPH difference in trap speed isn't as dramatic as one might think on the street. Maybe he had an intake or something but I doubt it. Just saying I didn't blow his doors off like some might expect. I definitely pulled though. A nice long run and it would have been bad.

ProjectC55

Wrong you are.

The problem with the SRT8's is weight,weight ,weight,and it's brick like aero-dynamics.! Put this engine(modded) in a car that weighed as much as my C43 or your CLK55,and it will run circles around many cars. Look at the C5 Z06 ,less hp(425hp) than an SRT8 ,16 valves and runs the 1/4 mile in high 11's to mid 12's. I wonder why?

http://en.wikipedia.org/wiki/Chevrolet_Corvette_C5_Z06

That motor Pseudo Hemi(6.1L) which I call it as well as some old school Dodge/Chrystler/AMC/ Plymouth guys, has plenty of torque and power to run upstairs. Trust me if you know about engines and hp to weight you would not make that comment. You 're obssessed with comparing cars to your C63.

Deuuuce

The hp peak is at 6200rpm or so which is essentially redline so I wouldn't say the run out of steam. The Challengers's cd is around .36 or higher with a large frontal area but I can speak about the Charger/automatics.

The Charger tops out at 172mph which is the top of 4th gear so aero isn't as bad as one would think. Third gear ends at 123mph so it's a long climb in 4th. 150mph in about 30 seconds stock is on par with other low 13sec cars.

The automatic definitely has deadspots for roll racing and again, I need to see the 6speed overall gearing to comment on that.

Agreed the Challenger is too heavy, but quite roomy. It was a compromise - shorten the wheelbase of the LX platform to save development costs. The reinforcing of the chassis for the 2door design put weight back on.

But nowadays, look at higher performance sedans and coupes and unfortunately they sit at 3900lbs+ anyway.

joe_yoh

Thanks for posting this. Nice share of the story.

Jons95c36amg

Then how come a bolton, tuned 300c Srt-8 traps 115 in the 1/4 beats me by a few cars against my Clk55 from a roll to topend? Unlike the E63 which competely rapes my Clk55 I mean just bus lengths. E63s and 300c Srt-8s are about the same 4300lbs. The 32 valve 6.3 AMG motor loves to breathe.

ProjectC55

He beats you by a couple , and Will and I almost run neck and neck upstairs with me pulling past him way uptop. #1 Our cars are lighter and I guarantee both have a better hp to weight ratio than Will's car. His car will smash us in the 1/4 mile but as the speeds climb he starts losing that advantage DUE TO WEIGHT and I believe aero-dynamics with the brick like frontend.!!!!!! Yet a C5 zo6 with less hp and weight will murder it in the 1/4 mile. I wonder why?

Again Jon you have alot to learn.

How much hp does the E63 have vs the SRT300C?(425hp vs. 507hp) About an 80+hp difference,you do the math.

What is the hp to weight ratio of both cars as well?

I figured my Corvette ZO6 C5 illustration would have explained all of this clearly to you. Has less hp than a SRT8,less weight than an SRT8,has an 16valve V8 and yet will murder an SRT8 in the 1/4 mile and topend because it weighs almost 800 to 1k lbs less than a SRT8.

Final ex ,why does a CLK55 run away from a W210E55 1/4 mile and top end?
Why does it also rape a S55 N/A since the advertised hp for the CLK55 is less?


WEIGHTTTTTT! E63 weighs 4035lbs, SRT8 300C weighs, 4097lbs Now what does your CLK55 weigh compared to Will's car? About 600lbs less not including your fly weight vs Will's which I'm sure he has an even 100lbs. over you.

Improviz

Actually, mass doesn't affect acceleration any more at higher speeds than at lower speeds. Sir Issac's law is stated thusly:

f = ma, or force = mass * acceleration. So acceleration = force / mass.

Mass doesn't change with speed, but force does: the force in that equation is the *net* force acting on the vehicle; at low speeds, it's pretty much purely the engine force, less driveline losses and rollling resistance, but as speeds increase another force starts getting more and more prominent: the drag force, which increases with the square of velocity (i.e. at 100 mph, it's not 10x higher than it is at 10 mph, it is 100x higher, and at 150 mph it's 2.25 times higher than at 100 mph). The drag force is, I believe, 1/2*A*Cd*C*V^2, where C is a constant, A is the frontal area of the car, Cd is the drag coefficient, and V^2 is the velocity squared. This gets subtracted from the force pushing the car forward, lowering the net force.

So as speeds increase, the *net* force on the vehicle is dramatically affected, as the large negative component caused by the drag force starts taking bigger and bigger chunks out of the total.

This is why an E46 M3 will pull a Lotus Elise above 100 mph, even though below that they're quite tight: the two vehicles' hp/weight is roughly the same, but the M3 still makes roughly 50% more force, and once the drag starts eating away at the total force, the higher initial force means that it has more left over up high than the poor Lotus.

According to Car & Driver, the 300C SRT8 has a frontal area of about 26 sq. ft, and a Cd of 0.35. So you can see that it will be a lot more adversely affected by drag at higher speeds than an E63 with a drag coefficient of 0.29 and a frontal area in the range of 18-20 sq. ft. (guesstimation on the latter, but I'll bet it's pretty close ) Doesn't seem like a lot, but by way of example (I'm too lazy to convert the units, but this is illustrative), take the Cd*A of each one times 10,000 (100 squared, as in the V^2 when V is 100 mph) and you can see that it does make a huge difference:

0.35*26*10000 = 91000

0.29*20*10000 = 58000

Big difference, and it'll get bigger as speeds go up.

ProjectC55

So then the poor aero-dynamics of the 300C vs the E63 has a great effect as well as the hp.
This may be a crazee question however, if you have two E63s,one with just the driver and the other with four people in it,would'nt the weight difference come into to play somewhere if the two cars are accelerating from a roll ?

Improviz

Of course, and I said as much:
So definitely mass will have an effect, at all speeds. It's a = f/m, so if m gets bigger for a given f with all other factors being equal, a will get smaller.

But again, this is true at all speeds, i.e. the effect of mass isn't different at higher speeds than at lower speeds. The higher mass will hurt acceleration just as much at low speeds as at high speeds, because the mass isn't changing with speed, the net force is changing with speed due to the rapidly increasing drag force.

(*)One exception: if you manage to get your car to accelerate to the speed of light or thereabouts, the mass *will* change, relatively speaking, per Einstein's Relativity Theory, but we ain't talking about those speeds here.

Deuuuce

113/114mph is considered the peak for tuned SRT-8s unless someone ran better on a -1000ft day at Atco?

Most likely more important than aerodynamics in this case, you guys are forgetting about gearing. An SRT-8 at 70mph is a dead spot for 3rd gear from a roll and after 123mph, it's in 4th, a 1:1 gear with a 3.06 final drive.

The E63 gearing per C&D, shows it's in 4th with overall gearing of 3.699 up to nearly 141mph and hits 150mph in 23.3 seconds. That's a lifetime vs. a stock SRT-8 at just over 30 seconds.

I would be curious to see if the gap shrinks at all up to the SRT-8 173mph top end while the E63 is in 5th, a 1:1 ratio and 2.7 final drive.

Improviz

True, the E63's seven speed definitely enjoys a gearing advantage over both the CLK55 and SRT8, both of which have the same tranny/gear ratios (though I think the final drive is different), which will help to keep the net force higher, which coupled with its significantly lower drag force and substantially higher horsepower will give it a huge advantage in the 100 mph+ range.

Deuuuce

Actually a more recent test shows the E63 final drive to also be 3:06 and a 7200rpm redline which means at about 129mph it is also in a 1:1 ratio and with gearing being identical at that speed as the SRT-8, the hp differential will continue to show.

I'm showing an estimated drag area of the E63 at 7.166 sq ft (using a frontal area of 24.71 from 85% of height x weight) and using the same formula for the 300C, 9.1 sq ft of drag area. C&D lists the actual drag area of 9.3 sq ft.

Improviz

Yup, although don't know if you're looking at the right gearing numbers; R&T tested the 211 E63 wagon, and gave gearing as:
Transmission: 7-speed automatic
Gear Ratio Overall ratio (Rpm) Mph
1st 4.38:1 11.61:1 (7200) 40
2nd 2.86:1 7.58:1 (7400) 63
3rd 1.92:1 5.09:1 (7400) 94
4th 1.37:1 3.63:1 (7400) 131
5th 1.00:1 2.65:1 est (6350) 155*
6th 0.82:1 2.17:1 est (5200) 155*
7th 0.73:1 1.93:1 est (4650) 155*
Final drive ratio 2.65:1

Sedan seems to have same gearing:
http://www.lescinemasdusud.org/e63amg.html

Edit: double checked, Car & Driver gives same gearing for sedan as well:
http://buyersguide.caranddriver.com/...mg-sedan/specs

For the SRT8 Road & Track gave:
Transmission: 5-speed automatic
Gear Ratio Overall ratio (Rpm) Mph
1st 3.59:1 10.99:1 (6400) 44
2nd 2.19:1 6.70:1 (6400) 72
3rd 1.41:1 4.31:1 (6400) 112
4th 1.00:1 3.06:1 (6400) 158
5th 0.83:1 2.54:1 est (5550) 165*
Final drive ratio 3.06:1

Sounds about right for the E...I dug a bit, found this 211 E500 test, they gave it as 23.8 (couldn't find one for a 211 E63), which with a Cd of 0.29 puts it at 6.91 sq ft, close enough. Anyway, it's definitely much closer than my earlier guesstimate, so even using your figure gives a 23% reduction in drag force at any given speed...I'll run 100 and 130 mph for SnG:

100 mph is 44.7 m/s, 130 mph is 58.12 m/s

Equation for drag force is Fdrag = 0.5CApv^2.

C is drag coefficient

A = frontal area of the car

p = air density, which is about 1.2 kg/m^3 at sea level at normal temps.

So for the E63, we have Fdrag = 0.5*0.29*2.21*1.2*v^2 = 0.384v^2 This gives Fdrag = 767N at 100 mph, and 1297N at 130 mph.

For the SRT8, Fdrag = 0.5*0.35*2.40*1.2*v^2 = 0.504v^2 This gives Fdrag = 1007N at 100 mph, and 1702N at 130 mph.

So ballparking as I'm way too tired to calculate them out, I'd bet that the SRT8 is producing an accelerative force at 130 of 7500N or so, and the E63 comes in closer to 10,000N. So net force would be in the ballpark of 8700 N for the E63 and 5800 N for the SRT8, less rolling resistance which would probably cost each vehicle another 500 N or so. So the extra drag costs it around 10% at that speed (compared to what it'd have if it had the same drag as the E63), assuming my guesstimate of accelerative force is close, and I'm pretty sure it's in the ballpark, give or take....

ProjectC55

Gotcha! Basically with mass being the obvious constant the force/speed(variables )will be the thing that will always be affected at ALL speeds. I understand perfectly maestro!

ProjectC55

Everybody runs good #'s at Atco. My car would prob run high 12s at 111 or 112mph there. It's one of the fastest tracks here on the East coast.



The SRT8 is using the same exact tranny and has the same exact gearing as my car from tranny to diff. That goes for the W208 Clk 55 as well but the diff in the CLK55 has a 2.82 final gear ratio.

Deuuuce

This is interesting, there are some discrepancies in the published data.

Here is a recent test of the E63 showing the 3.06 final drive.

And yet this older test shows a 7000rpm redline and 2.7 final drive. However the "Performance Chart" link doesn't always work.

This is actually incorrect data, perhaps because it was an early test, or early production. Not sure why. I can personally attest the mph numbers are actually higher. per this link from C&D I wish they were that aggressive, actually.

All true, and it's been a while, but 114mph was the best for tuned SRT-8s in good air. If in fact 115mph has been achieved, my suspicion is that the 114mph times were on pump gas tunes of 400-407 rwhp and that 115mph was on a race gas tune, which in my case is 413rwhp during the same tuning session.

If not, then weight reduction, pulling a belt, etc would be the other way.

Improviz

Ah I see what's happening now: one possibility here is that I'm using the data for the 211 E63 (this is the one Jon ran afaik), and the test you're citing is for the 2010 version, the W212. Question is, did they change the rear end out on the new one? Gotta check...pretty certain about the old one, but I think they may have put a shorter rear end in there on the new version.

Fair enough.

I actually got tired of screwing around with these acceleration equations by hand every time and did a spreadsheet that'll give me the net force and resultant acceleration (in m/s^2) for a given speed, provided I know the tq of the engine (it's a lossless model i.e. no driveline losses, but that's easily changed).

I'll play around with it later and see how all of this stuff looks, if I can ever figure out which gear ratios to use.

Deuuuce

That would be a more desirable E63 in my mind with the 3.06. Need a E63 buff to chime in since time is short right now. The E63 wagon test I found showed a 2.65 FD.

Either way the SRT-8 is screwed and the magazines are only telling half the story.

OT but I would now love to see some test data from the new C63 with the hp upgrade.

Jons95c36amg

Yeah Atco is a fast track indeed. A bonestock E63 ran a 11.9@118+ in Dragtimes.com. Hmm I'm walking E63s so I'm very curious what mine does

Jons95c36amg

A tuned Srt-8 sedan traps around 114+ vs a stock E63 115+ not a real big difference. But from a low speed roll to 120 the Srt-8 will get a good beating.