Andrew M

Some of you may be interested in this since it seems people are constantly claiming gen 4 vipers make more power than zr1's on a dyno.

So Cal viper club had a dyno day yesterday and one viper owners also owns a zr1 which he brought to dyno.

There were several stock gen 4 vipers there and they all made very similar power (within several hp and torque variation).

Average viper dyno 508rwhp and 519rwtq, Zr1 was 519rwhp and 499 rwtq. Same day, same dyno, within minutes of each other. There was also a gt500 super snake(725hp) package that made some pulls 567rwhp and 518 rwtq. The dyno is very conservative no elevated numbers here.

Heber Guy

Thanks. Nice apples to apples comparison.

Fast Freddy

was it a dynojet dyno?

URBAN LEGEND

I would say by the low numbers it was a Mustang dyno.

redknight

It's amazing you try to tell someone comparing numbers from different days is pointless and they look at you like you're the idiot.

Were all the vipers regular ones or acrs or a mix? I would think the acr would dyno noticeably higher because of the lightweight wheel/tire combo.

URBAN LEGEND

Thats because they haven't been in the game long.

Andrew M

Dyno was a dyno jet, but a properly calibrated dynojet shows just like a mustang. I have had a car on this dyno and then on a mustang the day after and the power was within 5hp.

The vipers were ACR's and and normal gen 4's power output is identical. Some other interesting tidbits a gen 4 viper with headers/exhaust/air filter/tune 564rwhp and 540rwtq. A gen 3 viper stock 430rwhp 450rwtq, with ported stock heads/cam/intake porting/tune 580rwhp 545rwtq.

FLATOUT

Wow that Gen III Viper with heads and cam made nice numbers.

Thats what I plan on doing with mine. Thanks for the thread buddy cool to see both cars there on the same day, can't argue with that.

Andy Wheeler

11sec_C5Z51

What are Gen 2 Viper with ported stock heads/cam/intake porting/tune dynoing?

bgreen83

i bet if you threw a cam and ported heads and intake on that 4th Gen you'd get some higher numbers.

racerns

I am not sure how you properly calibrate a Dynojet unless this is not one of their inertial dynos. An inertial dyno is just a big spinning drum, there is no load cell to calibrate like a mustang dyno. All the rest is just a counting the drum rotations and plugging it into a math formula and then application of correction factors. They do sell some eddy current versions now though. Just wonder is they were uncorrected numbers, which is fine for comparison, as they seem low for a dynojet.

Andrew M

All numbers were corrected, anything else is pointless. Calibration is done through the software if everything else is in proper working order.

A gen 2 with those mods will do roughly 500-550rwhp, with striker heads you can go much higher just depends on how big of a cam you go with 600rwhp with a mild cam.

Gen 4's wont have a cam available for a while if ever, remember its very elaborate from the factory. Fully variable valve timing with intake and exhaust being completely separate and individually adjustable. It will be a while before someone even manages to to control the valve timing. The system is very complicated something like 5 separate computers handle the car.

redknight

I don't understand how the exact same car with much lighter wheels/tires could dyno exactly the same as the car with heavier wheels and runflats.

Also, I would be interested to see the results without the correction factor because one engine is na and one is sc. Shouldn't the correction factor be inaccurate for the ls9 because forced induction engines create their own atmosphere?

Racer X

The lighter tires and wheels will cause lower drivetrain loss so greater wheel horsepower. However, the 0-2% variance between stock engines could cover the inprovement up. One would have to measure the whp of the same car in essentially back to back run with the same engine tempertures to measure the gain.

Interesting question on the NA versus Supercharged, no different correction factor. However, maybe there should be depending on the boost control, if any on the car. Why you ask? Well it would depend on if the boost control was relative boost (7.5 pounds over atmospheric pressure) or absolute pressure (total pressure of 1.5 bar) theoretically with boost control based on relative pressure you would produce more power if the test atmospheric pressure was higher than standard than one based on absolute pressures. So when corrected it would measure lower than measured as it should, but the absolute pressure engine would be corrected lower as well, when in fact it would produce the same hp at the lower standard pressure.

Normally this would only result in only very minor variations. Where it becomes important is producing hp at altitude. Each system of control has its own issues and complications. I do not know which the LS9 has. Does anybody have any insight?

waltershu

here ya go.
http://forums.viperclub.org/srt10-sr...-wrap-up.html;)

Andrew M

I screwed the pooch on some of the torque numbers for the zr1 and the gt500 SS corrected them in the original post.

JBHunter

I noted with interest your Dyno Day numbers for the Viper, ZR1, and Shelby Supersnake...

I quickly calculated the rear wheel number from advertized horsepower and the calculated the per centage loss for each...

I have a question for those here that are in the know...Jason from Ktech, or Randy from DRM or other well informed persons...

The Viper"lost" only 92 horsepower from 600 engine hp for a 15.3% loss
The ZR1 "lost" 119 hp from 638 engine hp for a 18.6% loss
The Shelby "lost" 158 hp from 725 engine hp for a 21.7% loss

All on the SAME Dyno within minutes of each other...

How can there be such a difference in "drive line loss" for these 3 cars?

The simple evidence shows the Viper 'more efficient' in terms of rwhp...

Can it be the Viper is under-rated and Shelby is over-rated?

Please offer some decent ideas as to the % lost to get dyno rwhp.

Thank you guys.

Fast Freddy

a viper has about 15% drivetrain loss and a C5/C6 Vette with a manual trans has about 12.5% drivetrain loss and a Ford GT only has about 10% drivetrain loss. note the 4th gear in a Ford GT is not a 1:1 ratio though......

the Ford GT has the least amount of loss due to its transaxle primarily though.

the Ford GT was only rated at 550 hp from the factory. most dyno ~ 525 rwhp on dynojets so obviously they are underrated

Katech_Zach

The drivetrain loss is probably pretty similar for all three cars. The ZR1 and the Supersnake are supercharged so they get heat soaked on the dyno, resulting in a less dense air charge, more knock retard, and Catalyst Over Temp Protection. Chassis dynos are not good for comparing horsepower. It needs to be done in the controlled conditions of an engine dyno room. Nobody is under or over rated. The Viper is not more efficient, and chassis dynos are not good evidence for anything.

gm4life

Off topic question for you. Is it true that GM has the only environmentally controlled test cell in the world? Someone mention this at a GTG and I couldn't find info on it.