twin plug igniton curve???

[Jeff Alton]

Twin plug guys, what does your ignition curve look like?? Max advance? Idle?

Thanks

[len911]

I got these numbers from Steve Weiner a number of years ago... If you are using an Electromotive unit, make sure you measure the advance at the terminals instead of using the silkscreened values since they might be off from true advance values. Remember, advance is cummulative...

Static: 3 deg
Idle: 6 deg (9-10 total)
3000: 12 (22-24 total)
8000: 5-7 deg (26-28 total) Check this at 6000 and adjust the 8000 knob to suit. Do not exceed 28 deg!

I have used them on my 3.2l w/11:1 Cosworth pistons, 46IDAs and Electromotive. Seem to work very nice... Lou

[WERK I]

Jeff,
I think we need a bit more information on the engine before values can be given. For instance is it turbocharged, what compression ratio, FI vs. carb, twin plugged?

[sand_man]

Initial: 8
3000: 12 (20 total)
8000: -2 (18 total)
Rev limit: 6,500

I've heard that with twin plug you actually need less timing. I've been told that this really needs to be done on a dyno to steady state things. Stephen Kaspar of Imagine Auto mentiond that in an engine similar to mine (7.3:1 CR, 3.4L, twin plug, SC cams, etc.) he ends with around 18 degrees of total timing.

[sand_man]

http://forums.rennlist.com/rennforums/showthread.php?t=279959

[Jeff Alton]

thanks guys, motor info

3.4
10.5
DC44 cams
1 5/8 headers
48mm Jenvey ITB's
Microtech ECU

Cheers

[kenikh]

Originally posted by len911
I got these numbers from Steve Weiner a number of years ago... If you are using an Electromotive unit, make sure you measure the advance at the terminals instead of using the silkscreened values since they might be off from true advance values. Remember, advance is cummulative...

Static: 3 deg
Idle: 6 deg (9-10 total)
3000: 12 (22-24 total)
8000: 5-7 deg (26-28 total) Check this at 6000 and adjust the 8000 knob to suit. Do not exceed 28 deg!

I have used them on my 3.2l w/11:1 Cosworth pistons, 46IDAs and Electromotive. Seem to work very nice... Lou

Is this on pump gas? WOW, 11:1; cool! What cams?

[len911]

Originally posted by kenikh
Is this on pump gas? WOW, 11:1; cool! What cams?

I'm running an Elgin cam similar to a GE80... The 11:1 info was given to me by PO and confirmed by Cosworth distributor. Eng is putting out about 300HP. Lou

[kenikh]

GE80; that answers the question. All of that overlap softens the dynamic CR at the lower revs. I have a 2.0 w/ a mod-DC44 (102 lobe centers) and a buddy has some 11:1 Cosworths to sell. I was trying to figure out if I could run them at 11:1 or if I will need to cut them down to 10.5. I think my overlap would dictate a lower CR than 11:1.

Thanks for the great info!

[cstreit]

I copied this from a couple posts I made a few years back.


Those settings sound about right. I used a few degrees less than that, but I am running twin plug. My settings are at:

Initial = 8 deg
3000 = 29 total (+21)
8000 = 26 total (-3)

If you are flatter on the mid-range, you might try dialing a little advance out. In general advanced=horespower, retarded=torque. The electromotive curve in the mid-range is MUCH more advanced than stock.

Here is a graph that I used to define it when I dial in my curves for particular tracks...



The green and red are the top and bottom ranges for the factory advance curves on an early SC motor. The blue represents the initial advance curve from electromotive... I've found that while this setting works well in my race car with a close ratio gear box it doesn't work as well on a street car.

I think the higher advance at 3000RPM "steals" torque but gives a better HP curve. THis isn't necessarily proven or even scientifically accurate, but only based on my subjective experience at the track.

[len911]

Chris, just to clarify... The original post was asking for timing specs for twin plug engines. My car IS running twin plugs, just making sure we all in the same page... Lou

[Jeff Alton]

Yep, I am running twin plugs and looking for that info.

Chris, thanks for the chart.

Cheers

[DonE]

I just came from 3 days on an engine dyno with my rebuilt 3.4 turbo, super C2 cams, 8.0:1 CR JE's, and so on.

My initial timing is 22, around 1800 its 34, then tapers off to 15 at 6800. I played with timing for an entire afternoon looking at torque, EGT, AFR and HP. These numbers were the best and are conservative. At 3000 rpm, I have more than 300 lbft of torque.

FYI

[mppickett]

Great work, Don. What kind of horsepower did you see?

[DonE]

Torque was 470 at 5500rpm - avg torque from 3000 to 6200 rpm was 421 (nice and flat).

HP was 530 at 6200rpm, 12.8 AFR, 1533 degrees EGT, one bar, 15 degrees timing, 50 degrees C inlet air temp.

[mppickett]

Wow, what a monster. So you're running 22* at idle, right? At what boost levels do you start dialing back the advance? For example, what advance are you running at 0 bar boost and at 1 bar boost?

Thanks,

[DonE]

Yes, 22 at idle, 36 at 0 boost (100 kpa), then within 500 rpm it drops to 15 degrees at 1 bar.