[Diy_efi] Estimation of spark advance

[Bruce]

From: "Carsten Beth" <Carsten.Beth at Informatik.Uni-Oldenburg.DE>
Subject: Re: [Diy_efi] Estimation of spark advance
> > If you really think your as good as or better then the Honda engineer=
s,
> > well, knock yourself out, but I'd accurately map out what they have, =
and
use
> > that.   If you go to a high resolution map then maybe you can improve=
 on
it
> > a little, but I really wouldn't be looking for any huge gains.
>
> I don't want to make a perfect tuning with respect of power or whatever=
,
> what I mainly want, is just to overcome some inaccuracies. The Honda
engineers
> build a system with two cams on the end of the cam shaft. These cams dr=
ive
two
> points, each responsible for one coil resp. two cylinders. This leads t=
o
> inaccuracies because both cams aren't exactly equal and little differen=
ces
leads to
> big differences in the sparc advance. If I adjust the advance for one
> cylinder, I observate an deviation of more than 5=B0 for the other one.
There is also
> no way to justify this fault. In that sense I actually think my system =
is
better than
> the original one.

I can't tell you what was on the Honda engineers minds, but this cams not
being the same maybe some cleverness on their part.  One defining moment =
on
what dictates what the actual compression ratio is going to be is when th=
e
intake valve closes.  So in that reguard there may be something else goin=
g
on.

> > Motorcycle (touring) is going to be conservative, tune wise, an incre=
ase
in timing,
> > might just get you some galled rings in stop and go traffic.

> What do you mean with _conservative_? Do you mean it's better to give
> less advance? Perry Harrington writes in the same thread something abou=
t
2=B0
> less than the point where the engine begins to ping. Would you give les=
s
than
> 2=B0?

Yep.
I can run the cruise timing up to 48d BTDC on my car, and that yeilds
exactly 0 increase in MPG.    All the 48d can possibly due is increase oi=
l
temps, and bearing wear, if there was a serious increase in MPG then the
trade might be worth something, but if not, why bother?.
  The 2d is in a system with a K/S (if he's in a round about way quoting =
my
Tuningtips.txt).   And again that was in high performance WOT tuning.

> And (sorry, my english isn't really good, how you surely noticed) what
> do you mean with galled rings?

Neither's mine.
The AL having been locally overheated so as to pinch the upper ring, so t=
hat
it doesn't seal against the cylinder's bore.
Bruce

> Carsten



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