2009 Dodge Challenger R/T: We Strapped It To The Dyno

I love me a smooth graph! And a nearly horizontal torque curve. Yum yum. :)

Interesting. I notice their is no comment on the difference between Dodge's hp claim and what you guys came up with. Other than Dodge stretching the truth, what could the difference be attributed too?

Also, did you take any pictures of the engine with the plastic cover off. I don't get why they put that on? Doesn't anyone enjoy looking at an engine anymore, and trying to figure out how it works (or make it work better)? Or do they just want us to forget about the engine and believe big plastic boxes move our cars around?

Anybody know what kind of car that is on the lift behind the challenger in the first picture?

and that's a nice curve they have, to bad its overwhelmed by weight.

Actually looks like the Challenger might be a bit underrated on the power side. The torque at the wheels is about 15% off flywheel ratings, which is as expected. But the power is only 10% off. It would seem that perhaps the Challenger is a little healthier than advertised - to the tune of 15-20 hp.

Lotus Exige

"Interesting. I notice their is no comment on the difference between Dodge's hp claim and what you guys came up with. Other than Dodge stretching the truth, what could the difference be attributed too?"

Dodge isn't telling a lie. There is engine horsepower (horsepower at the flywheel) and there is horsepower at the rear wheels. Dodge tells us what the horsepower is at the flywheel: 375. The Dyno tells us how much of that horsepower reaches the rear wheels: 335. The difference is attributed to frictional losses in the drivetrain.

I agree with church123, Dodge probably underestimated the horsepower at the flywheel.

"The 5.7 HEMI is a pretty darn good engine - gas mileage aside."

Are you serious? Edmunds is averaging something like 18.5 mpg in this 375 hp 4000 lb car. I think the gas mileage is pretty good, especially when you consider that these guys are probably driving with a heavy foot.

Nice motor, but hood prop rods are so lame and cheap.

You typically lose 20% from the flywheel to the rear wheels in a dyno run. I'm sure if this was an import brand, Edmunds would be gushing over the real world horsepower in the Challenger.

This car is rated spot on, not under or overrated.

For those who think it's underrated by 15-20 HP, 2 questions:

1. Point me to any modern (i.e. built within the last decade) RWD car with over 250 HP that loses 17-20% of it's power in parasitic losses.

2. Dynos vary, but MD automotive's is pretty consistently in the meat of the curve being neither conservative nor aggressive. Nonetheless, it's still a dyno and will read differently on different days. You have to assume a 3% buffer either way.

Modern cars lose far less to their wheels, as they become much more efficient in transmitting the power. Further, it's not a linear proposition. As your torque goes up, your parasitic losses as a percentage of your overall output goes down.

Nice dyno run.

Joe

Good points on the horse power. I guess you learn something every day.

Getting about 18mpg on a car isn't bad. To me that's a step up, considering I drive a 99 Explorer V6.

Maybe they use the hood prop rods as a retro back to the 70's. Similar to the handbrake. UG!

My real concern is with the steering. I keep reading that its a tough car in the "twisties" or corners. Is that just when compared to a sports car, or true in everyday driving as well?

I saw a white with blue striped (special edition?) Challenger R/T last night. It looked amazing. I think the Challenger is best in lighter colors - the black looks neat at first, but doesn't truely show the car off.

PS nice torque curve. I'd love that in my car :P

"By joefrompa on April 16, 2009 4:19 AM
This car is rated spot on, not under or overrated.

For those who think it's underrated by 15-20 HP, 2 questions:

1. Point me to any modern (i.e. built within the last decade) RWD car with over 250 HP that loses 17-20% of it's power in parasitic losses."

Yeah, but it's still more loss than 11%, which is what the Challenger's loss would have been if it's exactly at it's rated power. Most modern cars seem to be at about 15% drivetrain loss to the wheels, and that's what most dyno shops use to estimate flywheel HP. Which puts this Hemi's flywheel hp around 394, not 376.

What we don't know is if this dyno chart was SAE corrected (for atmospheric conditions), or SAE actual (uncorrected for atmospheric conditions). There can be big differences in these two numbers depending on the air temperature, barometric pressure, and humidity, when the dyno was run.

Edmunds' car is a torque converter 5AT. That right there is worth additional losses. The current M3 puts down about 350 or so on Dynojets. That's a loss of about 15%. Yet, the M3 is rated nearly 40 hp higher than the Challenger and uses a clutch type transmission.

For another comparison, look at the current G37s from Infiniti. Averaging about 285 on a dynojet which is a 13% loss. Again, with a manual transmission.

Don't forget, the wheel/tire package and rubber to roller interface are responsible for about half the losses on a roller dyno. To say that the driveline should only account for a couple % more isn't realistic - especially with an AT

Church -

So you are saying that a RWD car with a torque converter transmission is expected to lose about 15%, and maybe 12-14% with a manual transmission? Of course, these are all averages.

One Anecdote on this: My personal experience only, but Subarus tend to lose less in parasitic loss than, say, a Quattro Audi. The drivetrain has less "systems" to go through to transfer the power to the ground.

Joe

15% is a good figure for an automatic car with a torque converter. 12-15% for a manual. Occasionally a car will do better than that. Supposedly a manual transmission C5 Corvette can be down around 11% loss.

church123

edmunds Challanger isn't an automatic, it's a proper 6 speed manual.

firstwagon beat me to it...

Sorry, their introduction specs said 5AT. Must have been a typo.

For specific information on losses, the definitive source is an SAE paper published a few years back by the Southwest Research Institute (SwRI). You can find it in the papers section of the SAE website by searching for "Dyno, voice of consumer". You'll have to pay for it to read it though.

Their testing involved measuring actual transmission losses on a transmission dyno (they characterized a variety of transmissions), rotational inertia losses, differential losses, and rolling drag losses. They then compared flywheel hp, the measured losses and the results of testing on a Superflow inertia dyno, a Dynojet dyno and a Mustang inertia dyno (not the newer loading units which can read very differently depending on setup). They found that the rollers read about 15% less than flywheel on a manual transmission car (14, 15 and 16% lower) and 18% lower on an automatic. These results were within 1% of the expected results as determined by subtracting the measured drivetrain losses vs. flywheel horsepower.

Also keep in mind that on an _inertia_ dyno (does not apply to loading dynos necessarily), losses should increase as power increases in a pretty consistent manner. This is because as power increases for a given driveline configuration (same car, same gear, etc.) the acceleration rate will increase. This increases inertia losses in direct proportion to the power increase. Frictional losses in the diff and transmission won't increase as fast, but in a manual car, they only account for a couple % of the losses.

I've seen this car on the Interstate. Astonishing, beautiful car. I don't like much of the flamboyant colors, I would prefer black, silver, white or even red.

Has anyone else noticed that there's a C6 Corvette sawed in half and hanging from the ceiling in the first picture?

No, but I noticed the lotus

At a 15% drivetrain loss

335whp = 394 rated hp

350wtq - 411 rated tq

So yes, it's underated by nearly 20 horsepower.
Seems like Dodge wanted to put some space between the power ratings of the R/T and the SRT-8. I've read that the hemi used in the new ram truck and the R/T are slightly different but if that isn't the case, the R/T is using the same 390hp rated engine.

Please disregard my numbers for fact. I didn't read everyone's responses and there are a few here who'd school my knowledge about dyno's it seems. :D

Uhhh, what is that yellow thing in the background?

G8 GT's dyno's around 300. Closer to 20% loss.

Auto plus no 1:1 gear. Doesn't seem to slow it down much.

The original Challengers didn't use prop rods to hold up the hood. ALL SPRINGS, BABY!

"Nice motor, but hood prop rods are so lame and cheap. "

GT-R has one too.

Gen3 Hemis are great engines, idle quiet, use no oil, never seem to run out of breath. My '05 Magnum R/T has about 120,000 km now and the engine has been flawless. LXs might be a little on the heavy side but as stable high speed cruisers they're second to none.

yah cause they are based on E class's