desktop dyno!

[Marteney, Steven J.]

Horsepower isn't just about vehicle weight and speed.  You have to account
for aero-drag (at high speeds) and rolling resistance (tire friction and
tractive resistance, basically bearing drag).  I thought you said you have
the g's for the car from a datalogger?  In any single gear, the acceleration
vs. rpm profile is proportional to the effective torque curve vs. rpm,
they're just on different scales.  So, if you are logging acceleration data
before AND after peak torque then you will see the peak.  If you are only
running the car somehow after peak torque then yeah you can't get the peak.
But running that way isn't the most efficient, in my opinion.  Is the data
you have in a form I could see it?

One quick question is how do know peak torque is just after the car
launches?  Likewise, if you know what the car launches at then you know
close to where the peak torque is given that assumption.  Or, am I missing
something?

Steve

-----Original Message-----
From: Flanagan, Steve [mailto:Steve.Flanagan at VerizonWireless.com]
Sent: Thursday, August 02, 2001 2:39 PM
To: 'gmecm at diy-efi.org'
Subject: RE: desktop dyno!


The problem is that the car does not start from a rolling low rpm state, it
leaves
at a high rpm.  So peak torque is just after the car launches.

My desire is to know where I make peak torque, not just what the torque is
where I launch the car.  I figured if there is a way to calculate HP (maybe
relative to MPH and weight), I could back out torque from the HP curve.
because the HP curve peaks at a higher RPM then the torque curve.  Does this
method seem plausible?

I have a feeling that I can not get a good idea of where the peak is because
its always going to be a function of the launch RPM no matter what that RPM
is.



-----Original Message-----
From: Marteney, Steven J. [mailto:smarteney at xlvision.com]
Sent: Thursday, August 02, 2001 1:52 PM
To: gmecm at diy-efi.org
Subject: RE: desktop dyno!


Torque should be able to be obtained from acceleration rate.  After all,
torque generates a force and force is mass times acceleration.  You know the
acc, you probably know the mass of the vehicle(not weight, mass = weight div
by gravity) .  The torque produced at the rear wheels is force times the
moment arm, which is just the tire radius.  To get equivalent engine torque
divide out all the gear ratios (rear-end and tranny).  HP is then obtained
from this torque by multipying the rpm the acceleration data was obtained
from and dividing by 5252.  Clear as mud?

For purposes of absolute measurement this method assumes NO drivetrain
losses.  Also, this doesn't account for any slippage, tire or clutches.

Steve

-----Original Message-----
From: Flanagan, Steve [mailto:Steve.Flanagan at VerizonWireless.com]
Sent: Thursday, August 02, 2001 12:30 PM
To: 'gmecm at diy-efi.org'
Subject: RE: desktop dyno!


If I have data logged info for my car (G's, RPM, Driveshaft) can I calculate
the HP and Torque curves from this info.
 
The only problem is we launch the car between 5500 and 6700 and obviously
the G's are the highest right at launch, so the G's do no show a true
representation of where max torque occurs.  Maybe the RPM acceleration rate
can be used for HP and then TQ can be backed out from that?

Does anyone know what I can do to determine where I am making max Torque and
max HP and what the curves should be, or is there not enough info (on the
lower RPM scale) to get this info.  RPM range of pass is from 5200 to 8600
+/- 500 RPM.
 
 
thanks
 
steve 
 
 -----Original Message-----
From: russell quenneville [mailto:russellquenneville at msn.com]
Sent: Thursday, August 02, 2001 3:07 AM
To: Gmecm at Diy-Efi. Org
Subject: desktop dyno!



I am writing a message to see if I can find someone with the Desktop Dyno
2000 software, and is willing to share it with me.  I am trying to dial in
my engine and I would like to see where roughly the torque and horse power
is so I can tailor the fuel and ignition curves.
 
Thank-you....
Russ Quenneville.
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