Dyno Results - Drivetrain Loss 18% for GEN1 ???

Much · Jun 20, 2014

Got my Car on the Dyno 2 Years ago, but the more i look on the Results the more i suspect them.

The Results where 523 PS and 829 Nm Drehmoment
Thats about 512 HP and 611 lbf ft

with the following mods:
VEC2 , 1,7" Harland Sharp Roller Rockes , 3" Belanger Headers , 3" RoeRacing Cats+Mufflers , GEN2 Throttle Bodys ,Smooth-Tubes+K&N Filter , GEN2 Injectors

I got about 420 RWHP thats a 18% Drivetrain Loss - is that possible ?????? I read somewhere that 9 - 10 % are normal for GEN1 cars ????

The second thing i cant believe is the 611 lbf ft for a GEN1 whith these mods ????

Is there something wrong with my car or was there something wrong with the Dyno ?? (I dont no what dyno it was)

What do you guys think ??

http://forums.viperclub.org/attachment.php?attachmentid=21178&d=1340869603

Red Snake · Jun 20, 2014

I have always been told ~11% drive train loss for these cars with the manual trans.

Alot of people have stretched the number over the years. Probably so they can boast more flywheel hp than they really have.

denniskgb · Jun 20, 2014

you got punked :dunno:

MoparMap · Jun 20, 2014

I've always heard the rule of thumb was 15% for a manaul and 20% for an auto. Usually gives a pretty good ballpark number. Every engine is different though. I think I got a bit of a ringer with my car since I made 480/530 hp/tq at the tires on my car with just an intake, cat back, and tune when the normal the club sees at dyno day for stuff like that on a gen 3 is maybe 450-460 hp. I even have 68k miles on it now, so maybe the extra miles makes it work even better, lol.

Indy · Jun 20, 2014

Since it was dynoed in Austria, the high power output can be explained by the Arnold-effect

420 rwhp sounds plausible...18% drivetrain loss is too high, more like 15%.

ViperRed · Jun 22, 2014

I have been telling people this many times. DO NOT take dyno results as indication as to the power output of your car. You will get different results from different dyno machines in different conditions, operators and correction factors.

Dyno machines should only be used to identify power output fluctuation. Differences between before and after mods. Or when your car has an issue and needs to be tuned or corrected.

Never take dyno results seriously when it comes to power output of your car at the wheels. I would rather use track times as indication.

My BMW in stock form dynoed 389whp on a dynojet.
After all the mods were installed it dynoed 438whp
After the ECU was tuned 475whp

Same dyno. Same operator. Same conditions.

Factory claim 501 engine output. So you can imagine the drivetrain loss on a 7 speed semi.

Bryan Savage · Jun 22, 2014

I don't know anything specific about this case, but I would just say that you can't just add up what each mod is "supposed" to give and expect to see that on a dyno. Nor can you set your watch to any "approximate" drivetrain loss numbers. You could easily have a bearing or gear that's worn and chewing up your efficiency. The loss percentages are all "rules of thumb" that seem to be consistent across what everyone sees, but may not apply to you.

Much, I would say that unless you pulled the motor and put it on an engine dyno, then you're at the mercy of a lot of rotating things that can skew the final readings, just like Persian Delight says. I bet that if you ran the car, took it off the dyno, put it back on and measured it again, you'd get different numbers.

In my experience, we all look for faulty equipment when things disappoint us. The remedy is usually to spend more money.

mjorgensen Woodhouse · Jun 23, 2014

There are many ways to cheat dyno results for dirveline loss, the most obvious is tire pressure, one or two roller dynos, and how tight you tie it down to the rollers. As stated you should really only use it to track modifications. If you do a ton of the same stock cars on one dyno then maybe you can narrow down the actual loss "that dyno" shows, but random sampled cars you are just guessing.

ViperJohn · Jun 23, 2014

Years ago and VOI 8 I spent some time talking to an Arrow Racomg engineer. He told me that most of the Vipers they tested with rolling dyno and engine dyno indicated the drive line loss was 15%.

Mark also made some valid points in the post above.

Dyno Results - Drivetrain Loss 18% for GEN1 ???

Much

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Red Snake

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denniskgb

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MoparMap

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Indy

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ViperRed

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Bryan Savage

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