Showing KR in 3rd at WOT but not 2nd

[SideStep]

I am showing between 1.5 and 2 degrees KR in 3rd at WOT at 4400rpm and 1.0 g/cyl. I am NOT seeing KR in 2nd gear at WOT and the same RPM.

I now there are not separate spark advance tables for each gear. Is there any way I can tune around this?

FYI When I get the KR my timing is 19 degrees for that specific cell.....

???

[jimmyblue]

Because you are lighter-loaded (effectively,
by the trans gear reduction) you run up the
RPM faster and at less g/cyl and this cylinder
pressure "relief" allows you to stand more
spark. I would say to feather back the spark
in the 1.00, 1.10, 1.20 g/cyl rows until it is
just staying out of KR. If you plot RPM vs
dynamic cylinder air (slice it up so 2nd and 3rd
are separate vector pairs and scatter-plot) I
think you'll see the 3rd gear DCA-vs-RPM line
runs higher.

[SideStep]

I understand what you are saying. It just bothers me that I have to run a more conservative timing in my low gears because the high gears cannot bear the same amount of timing...

Any tricks you want to let me in on, or is this just the way it is... :-/

[jimmyblue]

If it's any consolation, MBT point is prior to onset
of detonation so if you have your high gears just
shy of KR, you are probably not giving up much
(if any) engine torque / HP by not having the
lower gears "up against it".

If you see the g/cyl - RPM difference plain enough
between 2nd and 3rd gear pulls as I described,
you may be able to "finesse" it (more advance in
the cells that 3rd never hits but 2nd does). If there
is not that much difference there, then we would
have to look at what other things might be different
between the conditions.

[silverTA2002]

You're seeing over 1.0 gm/cyl???

At WOT, I'm between .60 and .72 always.

Is he weird, or am I?

My mods are FRA, filter, lid, long tubes, exhaust.

[SideStep]

I have an ATI supercharger

You're seeing over 1.0 gm/cyl???

At WOT, I'm between .60 and .72 always.

Is he weird, or am I?

My mods are FRA, filter, lid, long tubes, exhaust.

[silverTA2002]

I have an ATI supercharger

Ahh.....

If I were you, I'd still pull 1 degree of timing in that cell till you get no KR.

From what I understand, KR shows up under engine load. And you'll have more of a load in 3rd than 2nd.

When I log, I log a regular full throttle run (1st through 3rd gears). Then I do a 2nd gear run from like 20mph, and a 3rd gear run from around 40 to make sure there's no KR under load.