Hi all,

I had my car dynoed yesterday. Best of three pulls was 343 hp & 301 tq to the wheels. What is the normal % of loss? What were numbers for some of you that have tested your stock V6s models?

Thanks!

 

Seems like you're a tad on the high side. But not unusual numbers.

 

Chances are, they did it on an inertial dyno like the Mustang. Those always seem to read high. To Dan's question, the drivetrain loss is around 15% on an RWD, so divide the dyno results by 0.85.

 

I don't understand. Why would I have to divide the results if those are the numbers at the wheels? What am I missing? Or, are you telling me this is how I measure crank numbers?

 

lol Duh... Sorry. Brain fart, I guess... Dividing the 343 by .85 gives me 403 hp. Are these inertial dynos that far off?

 

Absolutely. No two dynos will measure the same, and a dyno will measure different on different days due to conditions.

 

Can be. No easy way to calibrate them, and having to only overcome roller inertia rather than having an actual load applied will generally yield slightly higher numbers.

 

Oh, I see. What kind of dyno should I look for?

 

Mustang dyno = dream maker

Dynojet = heart breaker

 

So, should I still be happy?? Lol This was a dynojet.

 

dynojets also tend to read optimistic. You are probably thinking dyno dynamics. Dynos are just a tool. Great for before and after comparisons, but not a lot more than a fun gimmick if for one time use. They can give you a ballpark, but 20% variation dyno to dyno depending on brand and calibration isn't crazy.

 

The Dynojet will also read high unless they have the optional Eddy Current Load Control installed. You'll have to ask the dyno shop. I always look for a Dynapack machine.

 

I think you missed the point. The 15% is drive line losses, turning the trans, rear gears etc. So your engine is putting out a theoretical 403 hp but you only seeing 343 at the wheels. It's all funny numbers and pretty meaningless except for back to back tests on the same machines after a modifications.

It's also worth noting that the ECU may be pulling power out or adding power as it doesn't see the engine loading like it normally does on the street. That was discussed in past threads about getting repeatable numbers and how some graphs look 'unusual'. Without knowing exactly what the processor is trying to do the value of the dyno run is suspect.

A timed run up a grade will give similar data.

 

thanks for the info, I understood what you were explaining about the 403 hp and that being at the crank. I've been around cars, mods and dynos most of my adult life, just never with a Jag. That's why I was asking about the percentage of drive train loss. Well, I assume that the only thing I should do at this point is make sure and go back to the same dyno after the mods for comparison.

 

I hope there is fan somewhere out of the picture, otherwise you are torturing your car.

 

Haha No doubt! Yes, that pic was before it was all set to go.

 

It was a dynojet, but I noticed your response on the other thread. The tech did all three of my pulls in 4th gear. Is this why the numbers were high?

 

No, the gear shouldn't matter much. 4th gear is the correct gear to dyno the MT. Maybe 5th gear for the AT. That get's you to around 135mph at redline.

 

oh, ok. Mine is an auto, so I thought doing the pulls in 4th may have had something to do with it.