Re: Tuning Tips questions

["Dominic Sorresso" <surrexi2@home.com>]

----- Original Message -----
From: "Bruce Plecan" <nacelp@bright.net>
To: <gmecm@diy-efi.org>
Sent: Wednesday, August 16, 2000 4:00 PM
Subject: Re: Tuning Tips questions


>
> > Here's a couple of questions on your tuning tips dealing with the light
> > cruise section,
>
> Don't over analyse.   Don't make it more complicated then it is.
> Now with that said
>
> > 1 Once you have determined TPS signal at 40Kpa, you suggest adding
> > timing at that 40Kpa and RPM cell. The re-test at original TPS signal
> > to determine "new" vacuum value. Do I now +/- timing at "new"
> >Kpa/RPM cell or go back to 40Kpa?
> >     What increments of timing would you +/-?
>
> Nope, it's tps vs MPH,
> look to see where you are K/Pa just to know where to make the timing, or
> fuel change.
>   I cut things at 2d, unless there are initially no change or the figure
is
> just
> grossly wrong (that only comes with experience)

So in other words, the change in vacuum +/- is simply telling you whether
the timing should be cut or increased, but at the original cell (ie. 40Kpa x
1800rpm). Increase timing in that cell until there is no further increase in
Kpa. And then go through same iteration for EACH cell representing probable
cruising speeds. This process, then, optimizes each point individually. I am
repeating myself so I make clear to you what I have understood so far.

>
> > 2. When you say "drop off" as little timing between 40-50Kpa up to WOT
> > (100Kpa), what increment per cell are you suggesting. What should
> >total drop off be?
> > For example, At 1800rpm and 40Kpa, value is 24.3. At 100Kpa, value is 6
>
> Depends on car, and driveility.  No way to forcast what your engine is
gonna
> like.


Dropoff then is not just an integer that you deduct from each cell, but what
is indicated by the process
you described on top. Each cell tested and optimized individually. Correct?



>
> > 3. What about cruise range within +/- 200rpm of the initial 40Kpa
> benchmark?
>
> Depends on lots of variables.
> What resolution is the table you working at and what are the break points.
> If the steps are 1200, 1600, 2000, then I'd run the cruise mode testing at
> those steps in addition to what ever your cruise is that your concerned
> with.
>



Yes,the resolution is in 200rpm increments x 10Kpa increments.
Makes you long for using some of the telemetry systems in CART etc.
I understand the re-burns now.


> This is way you get into so many reburns to get it right.  You have to
look
> at the resolution of the table and kinda experiment around where ya want
to
> be so that you can smoothly transistion to those conditions.  Like do you
> baseline testing on flat ground, and try to do it in both direstions, to
> account for cross winds, mild grade changes etc..   Then move toward lite
> grades, and then larger ones.
>
> > I hope these questions make sense. they'll at least start giving me a
> > clearer picture of how to start?
>
> One change atta time, and notes.  That's all you really need.  Document
> Document document  the easier it is for you to see trends developing the
> quicker you'll be done, and ready to do another car.
> Then you'll see the )(#$)@#(    )#($#()#@    mistakes you made on yours,
and
> go back and fix yours.   Then ya help someone else, then again, it's aww
> $hit, and fix yours.   It's a continual learning cycle.  Sometimes just a
> silly like comment from one of the other guys, and it's aw darn, that's
> whats going on.
> Bruce
>
> > thanks,
> > Dominic
>
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