Twin plug + CIS - what is your timing set at?

[Craig 930 RS]

Just curious. I have TP, IA fuel head, adjustable WUR, etc - curious what others run their timing at?

Mine is at 5 BTDC at idle & 22 at 4k/up with advance/retard plugged. Changing to 10 BTDC idle & 26 4k/up upon recommendation of original TP builder.

[JoeMag]

dyno and advance timing until torque does not increase...

[beepbeep]

Originally posted by JoeMag
dyno and advance timing until torque does not increase...

...Or knock sets in...

[Craig 930 RS]

Joe has it right on - was curious what others timing has ended up as -

[hobieboy]

Originally posted by beepbeep
...Or knock sets in...

dumb question - how does one tell knock sets in?

thanks.

[Craig 930 RS]

Actually, a good question. Usually can't hear it in our cars.
IMO, setting the timing per JoeMag is the way to do it - this is why setting the timing on an engine dyno or loadable dyno is the best way to tune. I'm fortunate to have the spec form the prior build - derived from the engine dyno in 2004.

[dean]

Originally posted by Craig911
Actually, a good question. Usually can't hear it in our cars.

Really, I can hear it just fine. But that must be my uneducated ear.

[beepbeep]

Originally posted by hobieboy
dumb question - how does one tell knock sets in?

thanks.

You usually hear weird sound from engine compartment that sounds like a bunch of BB's rolling around in a barell. It's pre-ignition in it's mild form. If you hear it, back on ignition timing / enrichen the fuel / lower the boost. Engine will hopefully survive if it catched early. It's audible enough to be detected by ear from inside of the car.

If you are very off-base on turbocharged engine (wastegate ruptured, very lean, fuel depletion etc.) it will sound like somebody took a hammer and started knocking on the engine. It's usually an expensive sound. Compression rings will often crack. Prolonged knocking of this magnitude ("prolonged" can be as short as 5-10 seconds) might end ut with holed piston. 911 pistons will mostly develop holes on it's edges, seldom in middle.

[Craig 930 RS]

I've LONG heard from Steve Weiner and others that most knocking in our engines cannot be heard - subaudible, "you hear it and it is too late"

Not busting your balls on this, but it is directly contradictory to all that I have heard from some very credible people.

[Bruce M.]

I've heard it as a metallic rattle. I call it the death rattle. Haven't heard it since the last rebuild, though.

[GJF]

but it is directly contradictory to all that I have heard from some very credible people.

[Craig 930 RS]

Odd

[sand_man]

I'm on Electromotive XDi, so I read my timing with a multi-meter connected to the ignition ECU. I also have a MAP sensor. At start up, my idle timing is 15 degrees. At cruising (on the interstate, no boost, around 80-90 MPH) it's about 24 degrees. At full boost WOT, the MAP sensor quickly drops my timing to 20 degrees.

[Craig 930 RS]

Does idle timing - which is 'too retarded' - cause a rough idle?

[930turbo]

My past experience with a normally aspirated engine revealed less spark lead was necessary after added the second plug. The dyno proved it. If you think about it, you're starting two flame fronts in the same combustion space - therefore taking less time to develope maximum cylinder pressure. Sand Man stated his results were similar relative to stock. The engine I experimented with had as much as 35 degrees lead in single ignition form. The end result after adding the second plug was 20 degrees total @ WOT. Both CHT & EGT went down with the second ignition installation. Mid-range power was the most noticable change in power.

[Jim2]

930turbo -

EGT went down with the second ignition installation

This is exactly what I noticed too, but I was unsure what specific change attributed to it. Good to confirm this.

Jim

[Craig 930 RS]

Exactly what I also have heard - accounts for my 26 degrees rather than the usual 29.