OT max economy, engine stress

[Bruce Plecan]

----- Original Message -----
From: William T Wilson <fluffy at snurgle.org>
To: <diy_efi at efi332.eng.ohio-state.edu>
Sent: Tuesday, May 04, 1999 4:38 AM
Subject: Re: OT max economy, engine stress


"Lugging" an engine till it shutters, ain't good.  The shutter is usually do
to the tune-up being off.  Many tuners don't allow for vey high load/low
rpm, goes back to carb days.  As a test of a calibration I sonsider it right
if at 1,200 rpm or less I can hammer it and it pulls cleanly.  The above is
for a streetable engine, meaning say less than .5" 300d 0 lash.  Some big
cams, in heavy cars can't be grief.
    The "bad" thing about shutttering is the engine stops, and then resumes
for a moment with no oil presssure.
Bruce

> > My question for y'all is whether I ought to be concerned with
> > what I have always been told is very hard on an engine - asking it to
> > do a lot of work at very low RPM.  My car doesn't really "like" to be
> > lugged below about 2000 RPM, depending on load.  It shakes and
> > shudders if I load it down to heavily, although it does continue to
> > pull.
>
> If your engine is shuddering, you should downshift.
>
> Some engines (most diesels, GM Lx1 series V8) will pull like mad more or
> less from idle.  It really takes an effort to lug these engines.
> Fortunately, the Trans Am and, I think, Camaro of recent years have an
> "engine lugging solenoid" which forces you to shift into fourth gear at
> about 20-25 mph. :}
>
> The 3-cylinder engine in my Geo Metro has the world's strangest torque
> curve, and doesn't mind being lugged at all.  For a small engine, this is
> highly unusual, IMO.  Nevertheless, it's ready to go at 1500 RPM.  This
> is, I'm sure, part of why it gets 45-50 MPG.  :}
>
> > Am I beating the bottom end out of the engine?
>
> Well, you aren't doing it any good.  Just don't lug the engine.  It serves
> no purpose and, although most modern engines will put up with it (and a
> variety of other abuses) without too much complaint, you accomplish
> nothing by doing it, so don't.
>
> > Also curious about heating the fuel to improve economy.  Worth
> > half a damn?  Any words of encouragement or caution?
>
> Useless on fuel injected engine, IMO.  May obtain some benefit on setup
> where fuel is vaporized.  Fuel injection system atomizes fuel and hot fuel
> will do nothing except (marginally) increase risk of detonation.
>