Yesterday, Markski posted the following dyno graph for an unknown Proto car that, according to the graph, made over 900 RWHP:



Markski's post: https://www.6speedonline.com/forums/...2&postcount=46

The horsepower and torque curves do not intersect until 6400 rpms. I am far from a dyno expert but, from what little I know, horsepower and torque curves always intersect at 5252 rpms. This is a function of how horsepower is calculated: horsepower = torque * rpm/5252 (http://auto.howstuffworks.com/horsepower1.htm , http://auto.howstuffworks.com/question622.htm). Below 5252 rpms, horsepower is necessarily less than torque. At 5252 rpms, horsepower is necessarily equal to torque. Above 5252 rpms, horsepower is necessarily greater than torque. This is a mathematical certainty given how horsepower is calculated. Therefore, at the moment when torque and horsepower are necessarily equal -- 5252 rpms -- the torque and horsepower curves will necessarily intersect.

Why do the horsepower and torque curves on the above dyno graph not intersect at 5250 rpms? Am I missing something?

Regards,

Craig

 

Craig it looks like its nothing but horsepower being shown. I've never seen a torque curve like that even on a 91.5mm Turbo Supra.

Though you are completely correct. If there was a torque reading it would cross at 5250, unless its a diesel like my buddies here in Houston LOL!

 

They seem to cross around 5200rpms to me. The left and right numbers are labeled different. If you drop the tq graph equiv. to the hp numbers...it seems about 5200rpms.

 

Mark clearly states in that post, that this is a RWHP dyno...

 

Good point. I did not notice the two different scales. That may explain it. Thanks for the clarification.

Craig

 

Craig,
I would never post a BOGUS graph... mine or anyone elses... KPG called me and said that that graph is wrong... I screwed up and sent the wrong one that was actually a comparison between some other dyno pull etc...
I can email you the other one...

 

Marek
I ask you not to put up my dyno sheet
R

 

Oh snap, that is Robs car? Well I guess that should shut the haters and non-believers up.

I wouldn't worry about it being posted, Rob. Are you worried about not suckering people into money races?

 

the first dyno sheet does not use the horsepower = torque * rpm/5252 formula, it uses a dyno (loading dyno) uses an electric brake to keep the rollers from accelerating . but dynos from dyno jet (inertia dyno) (supra's sheet) use the horsepower = torque * rpm/5252 formula that's why on all dyno jet's sheet hp and tq are crossed at 5252 rpm..

also, if the 900 WHP porsche did a dyno run on dyno jet it will get more hp and tq (reading from the dyno) than on a loading dyno (Dyno Dynamics)!!

that't what I know, sorry about my English, it's not my 1st language that's why I can't explain more

for more info about loading dynos click here and click here

 

I actually am very ignorant when it comes to reading and understanding dyno graphs... however, if that's the case why is that that I have that same dyno graph with the TQ crossing HP at 5252 rpms? I honestly do not understand...

 

the scales are different for torque and HP so that is why they don't cross. Like craig mentioned earlier, theoretically, any petrol engine should have HP=TQ at 5252 RPM.

 

And it does... I just didnt show the correct graph.

 

This has nothing to do with an inertia vs an eddy current load dyno, only with how the numbers are displayed on the graph from this particular Dynapack. Most Dynapack graphs seem to automatically scale this way where a default Dynojet plot typically puts both axis on the same scale. The blue line is torque (left axis) and the green line is HP (right axis). At ~5200 rpm the car appears to be making ~680TQ and ~680HP, so they do cross right where they should.

Nice numbers.

 

A Diesel engine will also cross at 5250, if the Diesel can rev that high. If it cannot rev that high (like a tractor) the curves will not cross anywhere on the chart given that they are plotted with the same scale on the x and y axis.

 

thanks for the info, that makes sense