Not all of them. Dyna pacs and other dynos that use fluid resistance measure horse power and derive torque.

 

I've heard a Rototest spews out numbers based on a lottery system.

 

 

How do you measure horsepower and derive torque when horsepower is torque over time? Torque is what spins the rollers. Break it down for me, I'm a complete n00b

Also follow up question to Jim: you're suggesting his hp is spot on but tq is mis-calibrated. What would stop the chart from being the other way around?

also I LOL'd at the 4.27 correction factor

 

Yes Brain I do get it, if you look back I posted earlier that, based on his horsepower curve showing 290hp@5000rpm Dann should be making 304lb/ft of torque, not 498, the 498 is clearly preposterous and mathematically impossible based on the horspower numbers, DUH. Stop thinking I am supporting the 498 number, I am not, nor did I ever suggest it was possible.

The printed chart was put together from plots that were saved to a computer, then combined to show 4 different curves, the hp and tq for the old log and the hp and tq for the new tubular manifold. I am saying the scale on the left hand side of the chart only shows hp ONLY not torque, the torque curves themselves may or may not be accurate but the measurements suggested on the printed chart are clearly not accurate, as above he did not make 498lb/ft of torque.

I am simply offering a possible explanation for the anomaly, I am clearly not suggesting that the 498 lb/ft of torque is correct.

 

mathematical formula, HP=Tq times RPM divided 5252, or Tq= HP times 5252 divided by RPM

As measured on a dyno hp is just a mathematical function of the measured torque.

As far as the horsepower being right, I am only saying that the numbers from both charts match in terms of horsepower and the torque figure is way out to lunch, there's no way a 1.8l engine is making 498 lb/ft of torque on a GT2560, the 324 hp is within the realm of possibility so i am assuming it is correct, and yes, i know what assuming does....

Jim J

 

So basically you're agreeing with Brains statement that this dyno plot is bs?

And I understand the formula, and how it can be reversed.

My question is: if torque is spinning the rollers, it is what is actually measured. Everything else is calculated. So if you can't MEASURE power, but only torque, since that's what spins the rollers, and you didn't measure torque, but derived it from power, then........WAT.

Does it make sense that it makes no sense?


*edit: or are you suggesting that the dyno measured torque, derived hp, then derived torque from the power?

 

On a dyna pac, if I read their literature right, the reverse hubs that bolt on instead of your wheels spin pumps with pump a non-compressible fluid (or close enough like water if the shop is cheap) and they induce a head loss, aka restrict the flow, and they calculate based on that known head loss, the actual flow, and the efficiency of the pumps, the amount of power the pump motor (your car) is outputting.

 

ok good.

this is where you lose me. the 498 number is LINKED TO the 325 number. that are pulling up from the same data file. Even the blue plot from before has bogus TQ numbers. The dyno operator didnt open 4 different files, he opened two.

it doesnt matter whats written on the left, right, top or bottom, or along the entire circumference of my 2" *****.


i appreciate this, but it's wrong.

 

well that makes more sense. (assuming its true) I learned something

 

I just like to spin a concrete wheel and get standardized outputs comparable anywhere in the world to any other setup.

 

Sorry, I misunderstood your question, I am suggesting the dyno measured torque, derived horsepower and displayed horsepower, then the torque curves were improperly overlaid onto the horespower plots. I think it's clear the torque curves where placed incorrectly relative to the units on the left side of the chart (498 lb/ft, not likely) and that the numbers associated with them only apply to the horsepower (like I said earlier the HP numbers seem to be consistent across the printouts).

Of course I agree that there is something fishy about the plots, I thought that was obvious by my first post suggesting the actual torque output at 5k rpm would only be 304 lb/ft and not 498. I am only suggesting one possible reason for why the torque numbers could be wrong. And to be clear, it is only a suggestion, I have no idea what actually happened at the dyno, I wasn't there, I am only offering one potential interpretation of the data.

 

That sounds so boring.
The cool kids are making 500wtq on a gt2560.

Get with the times.

 

Here's the thing: I would believe what you're saying if it didn't specifically state: " 498ft/lb " meaning its not just a screwed up chart that was distorted onto the HP graph, but the dyno "spit out" the tq figures incorrectly in the 1st place.

Therefore there is no method to this madness.

Therefore its about as legitimate as......can't even come up with something witty at the moment


PS: we're all waiting for Dan to chime in and its all speculation at this point (as is his dyno plot). Just in case its unclear.

 

im about to put you on universal ignore. you understand where this suggestion makes less sense than Dan's plots right?


you're suggesting that the dyno guy found two random torque plots that perfectly coresponded with the two HP outputs in some, currently unknown, way and then merged the raw data files together so they were always linked anytime he ever opened them again.

 

maybe we missed the part in the thread where this is a diesel?

 

Once again Brain, READ what I posted, I said 4 curves, 2 horsepower and 2 torque, I did not say there were 4 different files

How do you determine that the 498 number is "linked" to the 325? All that is displayed is 4 curves on a graph with a set of units down the left side and across the bottom, I could use excel and plot 4 different curves that have nothing to do with each other, if the curves were copied and pasted they are no more linked than you and I are.

And I don't really care how you measure your *****, that's between you and your lady friends...

Jim J

 

you're missing the part where it says on the sheet that he made 498

so its not a matter of cut/paste of different plots. at least thats what I think Scott is trying to tell you

 

1. because that's how dyno files work.

2. the plots show peaks numbers on each:

• 498 tq and 325 hp
• 435 tq and 292 hp

3. both plots have the exact same tq discrepancy.



of course one could plot 4 different plots on a chart, but that's not what has happened here. You dont open the dyno software and go "hmmmm, I made a pull the other day, i think this is the tq plot and this is the HP plot. Oh yes here, 500 tq and 325 hp, yes that must be correct."


It's pretty obvious they have some sort of relation to the HP number, but Aussies use a different sort of math than the rest of the world apparently. I could probably figure out the mathematical relation in about 5 minutes if I tried. So PLEASE FOR THE LOVE OF GOD, stop suggesting that the tq plots arent linked. they are, and there's no ******* question about it.

 

I'm getting a raging clue that Brain is trying to say the dyno is bs.

I must get this investigated pronto.

Calling the hardy boys and nancy drew.