Cold engine = More advanced timing curve, richer mixture (at initial startup
then leans out)
Operating Temp = Less advanced timing curve, leaner mixture
IAT sensor - stuck in the intake manifold - reads intake temp but heats up
past normal outside air temp which causes the timing to be retarded even
more...loss of power. 3.9/5.2/5.9L engines are notorious for this and the
4.7L is almost the same. Moving the IAT sensor into the actual intake tube
cures this to a point. Not a whole lot else you can do though as warmer air
is less dense than cold air which in turn carries less oxygen - less power.
This is the whole reason for cold-air intake systems, intake cooling
systems, and why you see people putting ice on the intake manifolds to cool
down the intake charge in between runs at the track.
There's more to it within the PCM programming, but I'm not going to get into
details on that.
- Bernd
-----Original Message-----
From: Dan Kramarsky [mailto:dkramarsky68@yahoo.com]
Sent: Thursday, June 14, 2007 12:24 AM
To: dakota-truck@dakota-truck.net
Subject: DML: Cold engine = way more torque
so,
Is it just me or does every Magnum engine seem to totally rock when the
engine is cold.
Like when the temperature gauge reads exactly "C" or a teeny tiny bit past
"C".
[ Engine block would be between 100F and 150F at this point. It has not
even had the
chance to get to regulated temp of 180F ( i have the 180* t-stat mod
installed ) ]
But after it warms up to operating temp, it seems that a little bit of
torque has been
lost somewhere.
Details:
When I left my work @ 8pm this evening the outdoor air temp was 61F and
humidity was 70%,
I discovered IT WOULD CHIRP ON THE 1-2 SHIFT -AND- THE 2-3 SHIFT.
But after driving around for 5 minutes it wouldn't do it as much. And after
20 minutes
it hardly will do it. By this point the engine temp was right at 180 to
190F. This is
apparently the optimum range according to this website and other Dakota
websites.
And the outdoor temp did change that much. After I drove to my home about
20 minutes
away, it was still about 64F and 74% humidity.
So whats happen here?
Are the pistons and valves doing a better job when the engine is cold?
Is the PCM adjusting spark advance and fuel ratio that much?
I mean it like a have total different truck when its cold. By 'seat of the
pants'
measurements, it feels like about 25 FT/LB of more torque when its cold.
Details on the truck are in my sig. But I do have a home-brew 3" diameter
cool air
intake from right in behind the grill area to the stock airhat which has a
K&N Filter in
it.
No other mods. Engine was 169,000 miles and feels like it brand
spanking new.
thanks
Dan K.
1992 Dakota Club Cab LE with A/C, Cruise, PS, PB, PW, PL, 3.55 rear, 5.2L V8
and a 46RH.
Current Mods: Cool-air intake, 180* T-stat, relocated IAT, DynoMax Super
Turbo exhaust, Autolite Platinum plugs, 8mm wires
http://static.flickr.com/42/84856795_c18903d10f.jpg
Plans: Mopar Performance PCM (ECU), March pullies, upgrade to 3.91 rear
gear, replace viscous fan with electric fan
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