Dynoed the car at 20 psi

[Franko]

Heres the deal, 91 octane.. 20 psi.. 65 degree celsius intake temps.. 264 hp and 350 ft lbs torque. Thats as far as 91 octane would take me without detonating. Don't mind the shaky graph, it was getting a little bit of ignition noise so it makes it look weird.



Comments?

[progt91]

looks like you make some nice power

[smoke187]

nice numbers

[atlantamx3]

You should be putting down more power than that... honestly with your setup.

Still though, 350 ft lbs of TQ is NICE!!!! Watch that transmission!

[Franko]

Yeah I dont know why the hp is so much lower but its the torque that really matters anyways. The calculation must be wrong when it converts it to hp or something.

[Tazman2]

Nice numbers with 91 octane! No 93 around you? All we have here is 87, 89 and 93. Then a few gas stations that also have 91 but not many.

[Lex]

That graph is wrong. Hp and torque always cross at 5252 RPM since hp = tqxrpm/5252

Also what is this flywheel tq bs? He is obviously calculating something based on wheel numbers. Did this guy even know how to operate the dyno? One of the numbers is scaled - is it the torque or the hp?

[wht95scort]

Lex is right HP and TRq should always cross. HP seems right but somethings deff up with the Trq on how is being measured.

[Lex]

Torque is the one that is measured and hp is the one that is calculated

[1967cutlass]

Good call on the dyno graph, something is messed up

[Franko]

Well we dynoed my buddys car before mine and the numbers came up normal for what it is. Hes got a ls-vtec integra and he made 315hp and 290 tq. Right around where it should be for the setup. His never crossed at 5252 either.. This is a load type dyno not a regular rolling style. Hmm it does measure torque first and then calculate hp after.. Ill have to look into this further.

[therieldeal]

see at 5000 RPM you made 325 WTQ.... which when entered into the equation would be 309whp, which makes a lot more sense...

[Franko]

Yeah that makes more sense. Well Ive looked it up and apparently dyno manufacturers actually make special software to bring up a graph that people are used to seeing, one where it crosses at 5252 rpm.. Its called derived torque.. whats being shown in my graph is actual roller torque so it dosent cross a 5252 because its not calculated the same way.

So basically.. a 300hp mx3.

[Lex]

Yeah that makes more sense. Well Ive looked it up and apparently dyno manufacturers actually make special software to bring up a graph that people are used to seeing, one where it crosses at 5252 rpm.. Its called derived torque.. whats being shown in my graph is actual roller torque so it dosent cross a 5252 because its not calculated the same way.

So basically.. a 300hp mx3.

Wrong. Torque is measured and hp is calculated. Dyno manufacturers and technicians should follow a standard. The standard is that hp = tq x RPM/5252. You can't just change a standard cuz buddy operator at dyno feels like it. Otherwise I can claim I have 1000hp based on my own rules.

Here's what I think happened. Your car made x amount of torque and then hp was derived from that by the equation I gave you which results in whp. Then dyno operator guy decides he wants to estimate flywheel torque. So he multiplies that measured x amount of torque by some factor and gives you the second curve.

The reasons I believe this are:

1. The scale on the right is labeled as flywheel torque
2. Notice he gave you no decimal point on the torque number.
3. If you were making as much torque as that graph is showing you would be seeing 350+whp. 350 ftlbs of wheel torque is a lot from that motor at that psi.

I am not trying to rain on your parade, I think you made some good power and there maybe is some more room for tuning but I think it's stupid when dyno operators decide to come up with their own way of coming up with numbers instead of following the automotive standards.

You should call them up and ask them for a proper readout.

[Franko]

You could definately be right about the fellas up at the dyno. They only recently got the machine and I can tell that they do not know everything about it. But the nail in the coffin for me is that my friends car made EXACTILY what it should be making.. then I put my car on and suddenly its wrong? I cant see it.


This is off a forum for a tuning school. These guys know their ****.

An Engine Dyno being used in HP/Ftlbs will always cross at 5252 RPM.
If kW/Nm are used the lines will cross at 9543RPM.

As Warpspeed stated, doesn't happen automatically on a Chassis Dyno due to gearing between the Engine and the Roller where the Torque is measured. (Roller Torque x Roller RPM)/5252 = Roller Power.

Now, in the US where most people are used to seeing Dynojet graphs, they always cross at 5252, this is because the Torque on a Dynojet is a calculated figure from Engine Tacho Rpm and Roller Power.

On an Eddy Current Roller Dyno, where the Torque is measured, the Torque at the Roller will be higher than it is at the Crank, due to the overall gearing of the vehicle. EG. 400Ft/lbs at Crank goes thru Gearbox at 1:1 (still 400Ft/lbs), then goes thru diff ratio of say 4:1, we now have 1600Ft/lbs at the axle, then we have a ratio of the Tyre to the Roller, in the case of a 217mm Roller and an average tyre size of 650mm, we have a reduction ratio of 2.995, so our 1600ftlbs axle Torque is now 534ft/lbs of Roller Torque (this example does not attempt to take into account losses, it is just showing the maths).

Due to the "it's always been that way" thinking, Dyno manufacturers add some software that can show "Derived" Torque so the Torque and Power will cross at 5252, providing HP and Ft/lbs are used, this is simply done by back calculating from the Roller Power and an Engine RPM signal, much the same as Dynojet would do. I might add that this is really only necessary for the US market, not so much elswhere.

The good thing about Derived Torque is that it is independant of gear ratio's, so you can compare Torque on 2 cars with different overall gearing, whereas if using Roller Torque, the car with the overall lower gearing will show more Torque, albeit at a lower Road Speed.

Here's 2 Graphs, one shows Derived Torque and HP, the other shows Roller Torque and HP, but they are the same data, just shown differently, notice how one crosses at 5252, the other does not.