[Diy_efi] RE: Diy_efi digest, Vol 1 #413 - 12

[Shannen at grolen.com]

How would you isolate the friction in the contact patch?  Without a way
to attach a similar mass to the wheels without the friction of the
contact patch...  And additionally, since the tire is normally on the
road, it's not unreasonable to say that rear wheel hp is the net sum
after deducting the loss from the friction of the tire on the road.
Yes, we do coastdown runs also.  I can measure inertial and friction
losses to the front of the trans on a manual, or to the front of the
crank.  With an auto trans things are a little different.  I can only
measure to the last connected point within the trans, in neutral.  Some
auto trans like the THM400 don't overrun on coastdown, so I can measure
losses to the front of th crank with that trans.  Newer trans will
overrun on coasting, so I can measure some of the inertial loss of the
trans versus engine.  How much of the trans I get depends on where in
the geartrain the overrun clutch is located.
Shannen

DI>----- Original Message -----
DI>From: "Shannen Durphey" <shannen at grolen.com>
DI>To: <diy_efi at diy-efi.org>
DI>Sent: Thursday, December 19, 2002 7:52 PM
DI>Subject: Re: [Diy_efi] RE: Diy_efi digest, Vol 1 #413 - 12 msgs


DI>> Didn't you once say you specialize in asking questions?  This is a great
DI>> one.

DI>Why thank you

DI> We generally don't take into account any
DI>> friction made at the contact patch between tires and rollers.

DI>At least here in the UK this part is taken into account by the top dyno guys
DI>who always do a coastdown to measure frictional losses. This also allows a
DI>fairly good estimation of flywheel HP to be calculated.

DI>The rest I need to consider it very carefully. Tying all the threads
DI>together I may finally be seeing some light at the end of the tunnel. Thanks
DI>for taking the time to help out a poor dumb guy on the other side of the
DI>pond.

DI>Bill


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