[Diy_efi] RE: Timing and dyno pulls

[Shannen at grolen.com]

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
I>I have no clue what the beginning of this was alluding to as I could not fol
DI>it. The part about decreased air density requiring less timing lost me. Are
DI>suggesting if the map sensor reads 20 kpa you would retard the timing from w
DI>it is set at at 40kpa?? Air temperature increases need less timing yes but i
DI>not air density related at all.

DI>If you have never worked with an ecu that has gear compensation then you don
DI>know how it works only how you would do it. Do yourself a favor. Next time y
DI>are on the inertia dyno make a pull in first gear and one in high gear and d
DI>log  the O2 readings for both runs. Show me the part where they are the same
DI>Detonation is so far removed from tuning racing engines that if you get to t
DI>point you have truly lost the rabbit so to speak. Peak power +- 0.5% is quit
DI>ways from detonation. There is also no rule I have ever heard about keeping
DI>out of the cylinder heads. It is a heat engine. more heat more power. If you
DI>keep the heads cool you lose power warming them up. Make a pull at 130 degre
DI>water temp and one at 190... see for yourself. same goes for oil temp.. Keep
DI>the engine cool only makes you more comfortable not the engine. If you are
DI>keeping the heads cool to stay out of detonation then you are running too mu



DI>Dave

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