Parasitic Loss?

[johnk]

Anyone engine dyno'd a Viper motor then dyno'd the car (as is) on a Dynojet or Mustang dyno? How much parasitic loss is common on a Viper?

Thank you

John

 

[REDSLED]

12%-15% seems to be the general consensous.

 

[johnk]

I agree we see 12-16% (or more) discussed, 12% seems very low to me. Was wondering if anyone has actually dyno'd both ways in order to validate the numbers. Thanks

 

[ViperRichRT10]

12% of stock or does the 12% continue up the scale with power adders? Seems to me the power train loss should be constant with stock and not grow.

 

[GTS Bruce]

No practical experience here.However from searching posts for dyno results done both ways I came up with 13% a while back. GTS Bruce

 

[Greg 99ACR Red and Silver]

If it was 15% loss then a 450 HP Bone Stock GTS would dyno at 382 RWHP.

Many GTS cars dyno about 400 RWHP stock and that would indicate a 12% loss. So 12-13% makes perfect sense.

 

[johnk]

But, there have been a number of threads where the Gen3 cars rated at 505 fwhp put out ~425 ish at the tires, indicating >15%. Was just hopeful that someone dyno'd the motor on a stand, then eventually chassis dyno'd it so we could see some real numbers.

Thanks

 

[RobZ]

I read awhile back that the GenII's were under rated at 450 crank HP by the factory and the average number is closer to 500 crank HP. Any truth to this? This would put the guys dynoing at 415-430 RWHP at a 15% loss.

 

[GR8_ASP]

The average Gen III is around 445 RWHP on a Dynojet. Average Gen II was around 405 RWHP.

 

[622r109]

mine was 442 rwhp on a 05 viper that equals 520 to the crank when divided by 8.85

 

[622r109]

oops thats divided by 0.85

 

[Torquemonster]

13-14% is correct on several tests I have seen - I just can't put my fingers on them right now.

the most accurate formula for a Viper I have seen that comes close to reality is:

rwhp + 10hp divided by 0.88 = crank hp

crank hp - 10hp times 0.88 = rwhp

That should work out for stock or any mods. However, the results will be affected by changing the rotating mass eg. lighter flywheel, wheel/tire weight changes etc.

Dodge V10 crank hp is often higher than rated ;-)

Using the above: An average 445rwhp SRT10 is making around 517hp at the crank, and the average 405rwhp Gen 2 is making 471hp at the crank.

FYI - the big heavy wheels and tires on an SRT10 Ram probably cost 15-20hp.

 

[zorroespanol]

I read on a magazine that it takes 175 hp to spin the GENIII motor at 6,000 rpm.

that's one of the issues addressed by the new motor.

 

[Marv S]

I read on a magazine that it takes 175 hp to spin the GENIII motor at 6,000 rpm.

that's one of the issues addressed by the new motor.

What's the magazine?

We got to observe first hand the new 2008 motor on the dynos at DC a few weeks ago. They measure everything. The computer screen has so many measurements going you don't know where to look at first. At the end of the test running the motor at full power the program shuts the motor down and the dyno spins the motor at 6,000 rpm and they measure the power it takes to maintain that speed. a pretty steady 175 hp. for the gen IV motor

Since they check these things out so well I asked about the loss of the Viper motor. Answer was a range with 12% being the max.

http://www4.forum.viperclub.org/showflat.php?Cat=0&Board=UBB21&Number=781129

 

[FE 065]

Saw an ad for Mustang Dynos in a magazine. They were touting how their dyno loads the car for vehicle weight and aerodynamics allowing a more real-world test..(fwiw)

The 175hp is an interesting number. I'd like to see the number with the 10 spark plugs out of it though..