# Thread: EFI RWHP and EFI RWTQ

1. ## EFI RWHP and EFI RWTQ

Hey Guys
A LOOOOONG time ago I had enhanced the HP calc pid in this thread
Calculating Instantaneous Net Power

I am on a local musclecar forum ( http://www.musclecar-evolution.com/forums ) and thanks to one of the guys during a heated HP thread the equasion was posted for torque. Having that I figured why not create a calc pid for that also. ( thx skeeveman for the equasion info )

I get so many people asking about a HP number and where it came from, and I only use EFI, no reason to hit a dyno, I have this and a wb02 ( lc1 from greenlight motorsports ) why waste the money to get a number from a dyno when I have everything here.

so on with the new pid.
The formula given was for torque based on hp numbers below
====================
hp=(tq*rpm)/5252
hp*5252=tq*rpm
(hp*5252)/rpm = tq
====================

What I had used for HP in my calc back then:

OLD
*CLC-00-989
hp 0.0 400.0 .0 "(((3554+({GM.FUELREM}*6.350)+185)*{SAE.VSS.mp h})* dx({SAE.VSS.mph},6))/8226.63"

CALC.SSHPTRUE6 F60A CLC-00-989 "kW,hp" Performance "SS TRUE HP 06"

But to make it more accurate name: "(car) EFI RWHP Smoothing Factor 6"
Something that can be added, instead of 3554 ( using the customer vehicle weigh pid ), the 185 is the driver weight
NEW
*CLC-00-989
hp 0.0 400.0 .0 "(((3554+({GM.FUELREM}*6.350)+185)*{SAE.VSS.mp h})* dx({SAE.VSS.mph},6))/8226.63"

CALC.SSEFIRWHP6 F60A CLC-00-989 "kW,hp" Performance "SS EFI RWHP Smoothing Factor 6"

There are the smoothing factors for 2, 6, 12 depending just like a dyno on the change in polling.

Now for Torque: Change the 9XX to your favorite pid #.

*CLC-00-9XX
hp 0.0 400.0 .0 "(CALC.SSEFIRWHP6*5252)/SAE.RPM"

CALC.SSEFIRWTQ6 F60A CLC-00-9XX "kW,hp" Performance "EFI RWTQ Smoothing Factor 6"

In the end you have a nice rolling dyno giving you EFI HP and TQ numbers.

Its the dawn of a new day, forget Dyno RWHP and RWTQ
Go with EFI RWHP and RWTQ

2. Wow! This is really cool.

I did some digging and found something:
http://ohe.cat.com/cda/files/287140/7/LEGT5364.pdf

This PDF put out by CAT has some estimates of rolling resistance and HP required to maintain speed for certain speeds. With the VSS derived PID I think it would be super easy to make the HP calc even more accurate!!

I tried to find you the equation that takes CDA of our cars and translates it into HP lost but couldn't find it for you. Sorry. :( All I know is HP lost would be the square of speed.

3. Where do I copy/paste the data? I did one a while ago but forgot how and where to move the data.

TIA

4. User Configuration\calc_pids.txt

Attached my calc_pids for you, easier then cutting and pasting.

just make sure mine don't stomp on any of yours.

5. could you pleas explain how to do this. im am computer illitertate but im trying. thanks.

6. Check out the calc_pid listed in post #8. It contains the formulas needed for rolling resistance and aero drag. I have not worked on it for a long time, but am willing to continue to de-bug it with others' input.

7. Anyone tried the formula/pids? I tried these today and they seem to be on the low side by possibly 8-9%.

My RwHP using the pids put me @ 400. based on my setup, I am closer to 440 RWHP.

8. Which one did you use?

The one that you speed up over a certain range and coast down over it?
Or the regular one?

I have been meaning to make one that does it all at once with my Cda and rolling resistance plugged in as a function of speed in but keep getting distracted. At least this way you don't have to low down over the same range each time.

Only thing about the A+B method is if the wind and grade are constant during the test it figures those in. Other small changes too!

9. I used the most current one with txt provided by DBaxter.

Formula is working. I added 100 lbs to formula and HP did increase. maybe car weights are to light.

I didn't realize there was a difference or a process to implement to achieve proper results.

10. You stated you were about 40 horses short? How fast were you moving? Aproximately 80 MPH?

I like the equation that DBaxter provided it is easy and simple but depends totally on speed. Wind resistance is left out.

I used info from the Cat link to make up this quadatric regression:
y = ax^3+bx^2+cx+d
where
A = 5.7358e-5*x^3
B = 2.0635e-3*x^2
C = 4.3544e-3*x
D = -5.582e-04

Where X is {SAE.VSS.mph} and Y is HP lost due to rolling resistance and wind resistance.

If you put that into the function then it wouldn't show 0 when you were driving at the same speed all of the time. Also, it would help you realise a number closer to the dyno number of your car.

Of course this is going to vary from car to car due to AERODYNAMICS and fiction from our drivetrains, bearings, and tyres. We should be free from weight.

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