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jpnovak's Avatar
 
Join Date: Apr 2000
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John,

You do not have a stable timing island to idle. Set all 4 columns up to 1500 rpm to the same timing. On your engine with twin plug I would suggest 6 BTDC.

When you slow down the idle the timing ramps to 10 then it increases and timing drops then the rpm drops. You can not have a dip in timing at low rpm as this will drive your oscillation.

Once the engine is tuned you can add additional bins to catch the idle, usually this means a retarded timing at high MAP values to catch the engine.

Changing one column timing is not enough here until you have a stable idle.
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Old 06-13-2017, 03:55 PM
  Pelican Parts Technical Article Directory    Reply With Quote #61 (permalink)
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Quote:
Originally Posted by JohnJL View Post
Hi again. When you say idle advance, are you referring to the idle advance feature, or manually increasing/decreasing the idle advance angle in the spark table?


Thanks again
Yes, idle advance feature.

You should be able to get it to idle decently, then hold really steady with the feature.
Old 06-13-2017, 04:08 PM
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Quote:
Originally Posted by jpnovak View Post
John,

You do not have a stable timing island to idle. Set all 4 columns up to 1500 rpm to the same timing. On your engine with twin plug I would suggest 6 BTDC.

When you slow down the idle the timing ramps to 10 then it increases and timing drops then the rpm drops. You can not have a dip in timing at low rpm as this will drive your oscillation.

Once the engine is tuned you can add additional bins to catch the idle, usually this means a retarded timing at high MAP values to catch the engine.

Changing one column timing is not enough here until you have a stable idle.
Ditto.

Having 10 then 5 then 8 will cause a swing.

It needs to be 5 or so all around the idle bin you're shooting for.

I think you'll have it after you make a block around the idle bin.
Old 06-13-2017, 04:10 PM
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10 degrees at 800 RPM is nearly, or is, 20 degrees on a single plug!!!!!


That's why it's going crazy!
Old 06-13-2017, 04:12 PM
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Also, have you verified that your timing light and MS ignition timing setting match? This includes rpm latency.

Do this before you do anything further.
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71 911T SWT - Sun and Fun Mobile
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Old 06-13-2017, 05:11 PM
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Quote:
Originally Posted by Tippy View Post
10 degrees at 800 RPM is nearly, or is, 20 degrees on a single plug!!!!!


That's why it's going crazy!
That went over my head.
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Old 06-13-2017, 07:16 PM
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Quote:
Originally Posted by jpnovak View Post
Also, have you verified that your timing light and MS ignition timing setting match? This includes rpm latency.

Do this before you do anything further.
Yes. I have fixed timing and checked it matches my light. Both sets of plugs the same.
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2007 911 Turbo - Not a toy
1985 911 Cab - Wife's toy
1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 06-13-2017, 07:16 PM
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Quote:
Originally Posted by JohnJL View Post
That went over my head.
Since you're twin plug, your timing advance is said to be 8-10 degrees higher than a single plug in equivalency.

So, if you're at 10 degrees on your setup, that's equivalent to 18-20 degrees on a single plug.

20 degrees of timing at only 800 RPM is a LOT of timing.

I'd put 0 degrees in, in the 800 RPM, 1000 RPM, and 1200 RPM columns from say 30 kPa to 60 kPa (whatever your kPa's are setup as exactly) in TS to see if it'll stabilize.

I guarantee it will.
Old 06-13-2017, 09:35 PM
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Stabilizing the idle at 1000 RPM was the goal, in my mind and Jamie hit the nail on the head, having a timing island is the key. Setting a higher advance below your idle will catch a falling idle and bring it back into the idle cells. The 1st cut at it is a little crude, mimicking a mechanical advance and the step below the idle cells may need to be reduced and smoothed...but now you can use some more finesse to catch the idle and maintain it. I've used this method many time and it works well.

Here is a good DIYAutotune article to support that method of idle stabilization.

(scroll down to "Correct Timing")

https://www.diyautotune.com/support/tech/other/idle-tuning-megasquirt/

I believe that it is common for twin plug engines to be timed for 25-28 degrees total timing. (approx 10 degrees lower than single plug total timing)
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Last edited by al lkosmal; 06-14-2017 at 07:27 AM..
Old 06-14-2017, 07:20 AM
  Pelican Parts Technical Article Directory    Reply With Quote #69 (permalink)
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John, we need an update....
Old 06-15-2017, 06:05 AM
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Hi guys,
Thanks so much for your great help here, on email and offline.

I switched in a new o2 sensor and installed one of the MSD noise filter caps that arrived. I am waiting on the second one which should arrive today, I hope to get it installed tonight, calibrate the new o2 sensor, take some of the advice I have received here and try a session tomorrow.

A few have asked here and offline about the injectors...they are from RC and I had then cleaned, tested and matched before installing. I dont suspect issues with them.
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1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 06-15-2017, 07:05 AM
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And you are running resistor wires and sparkplugs? EMI will drive EFI nuts.
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Old 06-16-2017, 10:17 AM
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Quote:
Originally Posted by dap930 View Post
And you are running resistor wires and sparkplugs? EMI will drive EFI nuts.
Ooh, yeah. Good point.

Need to have "R" in the plug part number!
Old 06-16-2017, 10:57 AM
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An update, but no success yet...

The wires are fresh magnacor 8mm wires. I dont recall the plug, BPR7 I think.

I installed one of the "Noise Capacitors" on one of the MSDs. The other one is supposed to come today. I didnt notice any difference in the voltage fluctuations. Maybe a little reduction but maybe not. There is already a 4700 cap on the megasquirt power. Checked the 3 groundstraps on the engine and transmission.

Switched in a spare o2 sensor and calibrated it. The AFRs seem about the same.

I tried creating a 2x2 "island" of bins on the spark and fuel tables of same values with smoothing around them.

I have to use the throttle to get it warmed up as I have the idle valve disconnected. Once the car is warm and I let all the way off the throttle it goes right into its oscillating cycle again until it eventually dies.

Here are shots of my last log showing this, my fuel and spark tables. All idle controls, advance, etc are turned off.

Appreciate if anyone wants to suggest some changes or other diagnostics?







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2007 911 Turbo - Not a toy
1985 911 Cab - Wife's toy
1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 06-16-2017, 11:46 AM
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I am also going out now to try something else Al suggested...
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2007 911 Turbo - Not a toy
1985 911 Cab - Wife's toy
1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 06-16-2017, 11:57 AM
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Still doing it...Al was kind enough to offer some suggestions, fuel map the same but simplified the ignition map.



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2007 911 Turbo - Not a toy
1985 911 Cab - Wife's toy
1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
1971 911 Targa S backroad toy
Old 06-16-2017, 12:23 PM
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Is it just me or isn't 9 degrees kind of much at idle?
On my single plug 3.2 I run around 4, maybe even less.
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Old 06-16-2017, 12:55 PM
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Lots of repeated advice to try zero. Worth a shot.

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Old 06-16-2017, 01:00 PM
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true......idle target is currently 6.5 and 1000 RPM and moving down in incremental steps.
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RGruppe #669,
http://www.x-faktory.com/

Last edited by al lkosmal; 06-16-2017 at 01:22 PM..
Old 06-16-2017, 01:18 PM
  Pelican Parts Technical Article Directory    Reply With Quote #79 (permalink)
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Sometimes you have to go extreme.

I'd put the ENTIRE ignition map at 0 degrees (that's equivalent to ~10 degrees on a single plug) and see how it runs.

I bet there won't be wandering.

8 degrees at 700 RPM is WAY TOO MUCH TIMING.

Next, once warm, use VEAnalyze Live! to adjust fuel map. Use "NORMAL" settings and let it clean up the fuel map for a few minutes.

If it swings too much, it won't work. You'll have to manually tune by watching the ball and wideband.

Slowly adjust cells until it's dead steady idle.

Last edited by Tippy; 06-16-2017 at 02:19 PM..
Old 06-16-2017, 02:15 PM
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