[Diy_efi] RE: Timing and dyno pulls

[Dave Dahlgren]

Hot or cold you pick the 'correct' operating temp at that point the correction
for head or engine temp is 0 at other places when not up to temp you make the
correction.

Sharp edges excepted in the heat deal.. They don't belong in the head so you
really don't correct for them. If they are there you will run less timing than
if they were not.

The gear corrections are fixed. timing vs gear,fuel vs gear, boost vs gear....
You tweak these to get best transient response not peak power. In the lower
gears all the driver and car know is how willing the engine is to change speed
and deliver power quicker. In first gear you might add 2 degrees of timing and
take out 2% fuel. Or limit boost by 10% if the car will not hook up.. There is
no time based factor in the ones I have worked on.
Dave

Shannen at grolen.com wrote:
> 
> DI wasn't trying to say that decreased air density required decreased
> timing.  I was saying that a hotter head requires less timing.
> Since you haven't mentioned it, how does the gear based timing
>  and/or fuel correction work?  I'm curious as to whether it's a fixed.
> universal type of correction or something that can be varied with
> time.
> The point was you have to tune for the end of the straightaway, or for
> the top of the long hill instead of the bottom if you have no way to
> work out a correction for how long it takes to get up the hill.
> If all you work with are engines with well designed chambers and good
> flow characteristics, then there's no reason for you to have to deal
> with the effects caused by poorly designed systems.  Not all the boys in
> this area have the cash to buy the types of engines you're describing.
> No rule about keeping heat out of heads?  Well, take a well designed
> head, add some foolish sharp edge between the intake and exhaust valves,
> and watch for detonation.  It'll happen if the head gets hot enough.
> And if you're on the dyno, and it does happen, what options do you have
> to fix the problem?  Now step down to the level of the guys that are
> likely to show up at the local dyno shop.  They're gonna run what
> they've brung.  Some guys have good heads on the car, some do not.  If
> you're hired to make the car run as good as you can, do you stop tuning
> if you see a set of bad heads?  I make the car run as good as I can. And
> I tell the guy he's got a set of bad heads.  Such is the level of the
> work around here.
> I tune for the top of the hill bu doing as much of the WOT runs as I can
> in high gear.  Sometimes with a light turbo car I'll drop the trans
> gear.  On an inertial dyno a light turbo car will sometimes make more
> boost than it would on the street, and you end up tuning in areas that
> you don't generally see on the street.  It depends on whether the
> owner's likely to be using the car for long runs at high speed or short
> stoplight type blasts.
> Shannen
>


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