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Discussion Starter #1
Since the August C&D had a quarter mile time on the new Charger RT, I thought I'd try to figure out what the SRT8 is capable of. Interestingly, Desktop Drag has the A580 in its stock transmission file - I didn't have to change gear ratios or anything. It was listed as a Mercedes trans.

Anyway, I WAG'd a 1600 stall converter with a 1.8 stall torque ratio. I don't have a power curve for the hemi, so I had to use just the peak numbers. What I came up with is 0-60 in 5.9 and 14.28 @ 101 mph. C&D had 0-60 in 5.6 and 14.2 @ 101 mph, so I figure I'm pretty close.

DD had the charger's 60 ft time at 2.6, which is horrible. So, I swapped in a 3000 stall converter with a 2.0 STR. WITH NO OTHER CHANGES, the 60 ft time dropped to 2.0, 0-60 dropped to 5.0 and ET dropped to 13.52 @ 102. Going to my current conveter, a 3500 stall converter with a 2.5 STR, dropped the 0-60 to 4.8 and the quarter in 13.33 @ 102. No engine changes, no intake mods, no exhaust mods. Just a converter.

So now that I have the software reasonably close to reality, I put the SRT8 in. With the same stock converter, the numbers were 0-60 in 5.1, 60 ft in 2.4, and the quarter in 13.3 @ 108 mph. We've already had word that a stock 300c SRT8 has done a 12.9 at Cecil, so again, the software seems fairly close to reality. The 60 ft again is really, really bad - ideally it should be somewhere around 1.7 or 1.8. So on goes the 3000 stall converter: 0-60 in 4.5 and the quarter in 12.9 @ 108.

The 3500 stall converter with 2.5 STR gives 0-60 in 4.2, 60 ft in 1.8, and the quarter in 12.5 @ 108 mph. Incidently, with this converter the car crosses the finish line in 3rd gear at 6495 rpm, so the stock gears are exactly perfect. Changing the gears to a 4.25 rear to hit redline in 4th across the finish line netted me less than a tenth, so rear gear swaps are probably not worth much in this car (although they may be worth more with a milder converter).

Parameters were:
car weight: 4300 (with driver)
RT rear gear: 2.83
SRT8 rear gear: 3.06
RT redline: 5750
SRT8 redline: 6500
Typical track conditions
coverter was set at 96% efficiency.

Disclaimer: This was just a thought exercise, but I've been using this program now for several years, so I feel confident that the real numbers, when they come out, will be within a couple-three tenths of these predictions. I'd be able to get even closer if I knew for sure what the real torque converter's specs were.
 

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What does it say the V6 should run?

Is there anything else you can change other than the torque converter that would correct the 60 ft time without really effecting the 1/4 time and trap speed? Can you just figure in more traction or something? What do you figure is right for an R/T, 2.0?
 

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Discussion Starter #3 (Edited)
Dutch said:
What does it say the V6 should run?

Is there anything else you can change other than the torque converter that would correct the 60 ft time without really effecting the 1/4 time and trap speed? Can you just figure in more traction or something? What do you figure is right for an R/T, 2.0?
Best guess for the V6 is 0-60 in 7.4 and the quarter mile in 15.5 @ 89 mph.

I made sure the car had plenty of traction in the simulation. It's just that the stock converter is geared toward fuel economy and emissions, not maximum performance. The software says you could get almost the same effect as the torque converter by swapping in 4.11 gears, now that I'm playing with them on a stock converter. But the gears have absolutely zero advantage over the converter - you have to program the computer to account for the ratio change, and the gears are working all the time while the converter is locked up on the highway.

Another disadvantage of the gears is that you have to worry about the driveshaft overspinning. The charger is speed-limited to 145 mph. The impala was limited to a similar speed, 154 mph, because the driveshaft would start a resonant vibration at 156 mph. The driveshaft on the charger is probably similar in length to the impala's, so I wouldn't be suprised if that was the reason for the speed limiter. This can be easily solved with an aftermarket driveshaft, but it's an added expense of the gears.
 

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Thanks for running those numbers. BTW I didn't mention it before, but I think your estimation of 1600 stall is really low for a Charger. A V6 Mustang stalls at about 2200, and that seems lowish for new cars (due to the 3.8L being a mostly bottom-end engine). I think most new cars stall even higher. My '66 Chrysler stalls at 1600.
 

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Since theres no mention of the SRT driveshaft being different, I lean towards tires as being the reason for the limiter on the Daytonas/ perf package cars. I have had a response from the guy I know who works in Kokomo, he does NOT work in the 580 area, but knows guys who do. He's sniffing around now:) He did say that if theres any difference besisides programming, it's most likely the converter, but he has no facts yet.
 

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Discussion Starter #6
Dutch said:
Thanks for running those numbers. BTW I didn't mention it before, but I think your estimation of 1600 stall is really low for a Charger. A V6 Mustang stalls at about 2200, and that seems lowish for new cars (due to the 3.8L being a mostly bottom-end engine). I think most new cars stall even higher. My '66 Chrysler stalls at 1600.
I just fooled with the stats until I came up with a reasonable performance number. I know that the impala came stock with a 1400 stall converter, and I know that most stock converters have a stall torque ratio in the range of 1.6-1.8. From there it was guesswork until the performance numbers came out right. I think the V8 converter is pretty close, plus or minus a couple hundred rpm.

You're right that the V6 may have a higher stall converter, since it has a smaller engine. If it does stall at 2000-2200 or so (seems reasonable), that might be a good stopgap performance mod until the aftermarket catches up. If we could find out what the Intrepid used as its converter stall speed, WAG says the SE's converter will stall at about the same rpm. Dropping a 2200 stall converter in the RT lowers your predicted 0-60 to 5.4 and your quarter mile to 13.8.
 

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Discussion Starter #7
GLHS837 said:
Since theres no mention of the SRT driveshaft being different, I lean towards tires as being the reason for the limiter on the Daytonas/ perf package cars. I have had a response from the guy I know who works in Kokomo, he does NOT work in the 580 area, but knows guys who do. He's sniffing around now:) He did say that if theres any difference besisides programming, it's most likely the converter, but he has no facts yet.
What's the speed limiter set at on the SRT8?
 

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Allegedly 165, but as with the SRT-4, it could just be vaporware, with aerodynamics being the real limit.
 

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Discussion Starter #9
GLHS837 said:
Allegedly 165, but as with the SRT-4, it could just be vaporware, with aerodynamics being the real limit.
Here's something you can play with: http://www.bgsoflex.com/aero.html

charger frontal area: 25.9
Cd: .35

I sure hope we can foster a good relationship with the Dodge engineering department. They can really be helpful in situations like this. Maybe they can help us source a real performance converter.
 

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Input Parameters Are the Following:
Coefficient of drag = 0.3
Frontal Area = 25.90 sq feet
Test Temperature = 70.00 degrees F
Test Barometer = 30.00 inches Hg
Vehiche MPH = 170
Computation Results:
Air Density Computed is 0.00233
Aerodynamic "Drag Factor" is 0.02273

Rolling "Drag Factor" is 66.11639


Computed Aerodynamic Horsepower Required is 298
Computed Rolling Horsepower Required is 129
Computed Frontal Lift Force is 144 Lbs.

Hmmmmmmm......
 

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Input Parameters Are the Following:
Coefficient of drag = 0.3
Frontal Area = 25.90 sq feet
Test Temperature = 70.00 degrees F
Test Barometer = 30.00 inches Hg
Vehiche MPH = 165
Computation Results:
Air Density Computed is 0.00233
Aerodynamic "Drag Factor" is 0.02273

Rolling "Drag Factor" is 62.08651


Computed Aerodynamic Horsepower Required is 272
Computed Rolling Horsepower Required is 117
Computed Frontal Lift Force is 135 Lbs.

Now if I drop it to 165, we see that we are more in line with SRT-8 real world whp.
 

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Let's just put a s/c on the srt-8 and be done with it!! 500+ rwhp=high 11's in ET's !! :) I WANT MY CHARGER SRT-8!!!!!!!!!!!
 

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I'm curious what tires you plan on usung to get all this power to the ground...the diameter would have to match the front's to keep ESP from having kittens and you could have problems finding tires that sticky in 17" and up low profile sizes. As far as gears go, the 3.06 may be the deepest set avalible for the that center section...I'm nosing around the dealer trying to find out. I'm assuming a high stall converter would have to be cu$tom built. Having a Mercedes drivetrain from the converter back makes things a lot more expensive than when dealing with domestic dinosaurs but, if you want to drive like a sport, you've got to pay llike a sport :wink:
 

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I'm thinking jketron (the owner of the GS Motorsports initial install car) is heading for the track this weekend, wtched by the world of course. He's already stated that he is aware of the risks and has no problem building a new motor if required.

I'm sure we'll find the weak links pretty quick.
 

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Just give me my Charger SRT-8-----I'll figure out the rest when I get it!!! Of course,that's just after the fact from wiping the drool off my face,knowing that I actually got the car!!! :happy:
 
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