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

[William Shurvinton]

I must admit in shame that there are a couple of concepts here that I am
still having difficulty getting my head around, despite having followed it
each time it is discussed. Whilst I understand that a truck engine in a
truck has to work harder than the same engine in a hotrod I still have
confusions about 'load'.

I can't help wondering whether is it because I am thinking about it from a
MAP or TPS% perspective (NA). These are used to infer load, but are merely
measures or inferences of the air entering the engine. So if you are
comparing 2 applications on part throttle, for the same throttle opening,
the light vehicle will need less fuel than the heavy one. Normally you
modulate the throttle to match the load so you don't actually see this,
except perhaps the drivability issues with a non-linear throttle reponse due
to having too little 'load'. Or to put it another way TPS% is a measure of
potential power, not actual or required.

The Dyno of course has difficulty replicating this.

It may click after a few more years tuning the car, or am I still
approaching it from the wrong direction?

Bill
----- Original Message -----
From: "Shannen Durphey" <shannen at grolen.com>

<snipped everywhere>

."  Yet again the tune for
> the long, heavy load isn't optimum for the short, light load.
>
> Gear and load corrections can be a good thing.  > Shannen

>
> Dave Dahlgren wrote:
> >
. The better after
> > market stuff has tables and corrections for what gear you are in. You
can and
> > should change timing fueling and boost according what gear you are in as
it
> > compensates for the relative load on the engine.
> > Dave
> >
> > Shannen Durphey wrote:
> >
> > > Using a braking type dyno to tune a car for WOT can produce misleading
> > > results.  A lightweight car with a high power to weight ratio would
> > > typically never see the same load and duration that can be applied
with a
> > > brake type dyno


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