The answer to Mysterious Dodge Timing advance

Anyway I saw a nice v-6 dakota for cheap (1000$) and in good condition. So I really wanted to understand what was going on when you advance the timing on a dodge v-8 (and more specifically if I could find a way to make advance on a v-6). So I asked a man a question and got an answer. In slightly oversimplified terms the answer is that the ignition timing is determined by the computer through a combination engine sensor observations and the position of the crankshaft (ie. crank fired ignition). For the V8 exactly whats happening is the Peg thing. It just skips forward a fires the next cylinder at the higher advance. I still think it could be possible to get the timing advance on a v-6 magnum engine but through other means like a standalone engine controller like megasquirt. Still in conversation with this tech so more to come hopefully.

The long version:

“Hi I saw your reply to someone about re indexing the distributor on a 3.9 liter v-6 magnum engine for a dodge dakota. Here is my situation, I am going to run the same engine on an alternative fuel that runs best when the ignition is advanced up to 50 degrees above stock ignition timing. Is there a way to make this adjustment on the fly without re-indexing the distributor? I want to retain the ability to run stock ignition timing so that I can travel on gasoline should the need arise.
Country: United States
Make: Dodge
Model: Dakota
Year: 1994
Engine: EHC 3.9L V6 SMPI Engine”

Answer:

"Actually, you don’t change spark timing when the distributor is turned on these engines and that’s why you noticed no change with the distributor turned.

Ignition timing is determined by the fixed-position crank sensor, mounted in the upper-right trans bellhousing.

Distributor index is used to get cam and crank signals synchronized. It also locates the distributor rotor to a position that makes it more likely that spark will find the terminal intended, without crossfire. Caps are pretty small on these distributors by modern standards, so crossfire is pretty easy to produce if the distributor is turned a bit from its proper index.

Distributor index can be done on the 94 Dakota engines using a scan tool. It was the first year it was offered; previous years required a manual adjustment.

If a compatible scan tool is available, you would want to set your cam-crank offset to zero degrees. It’s going to dance around a little, but if you achieve an average of zero degrees offset, it’s as good as it gets.

But you’re still stuck with stock ignition timing and (really) no way to advance it.

-Ed"

Hey Eric, tell the man what we’re doing on the 318’s and see what he says. Thanks for the post. It’s still a mystery to me, but it works.

Very interesting Eric! Is this an internet discussion, can you post a link?

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On my 98 S-10 with wasted spark (and diagnostic tool) it will read almost up to 50 advanced when coasting down hills but I believe it is just searching for the ping point when it does that. Under load and cruising it usually settles out around 19 to 21 advanced on woodgas and around 15 to 19 on gasoline. I would recommend the ability to advance at least half a peg or a whole peg to prevent “crossfire”. I prefer the wasted spark setup now as it is so simple and automatic. I can go up to 5000 rpm under load with no issues but rarely push past 4000. ML

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Hmmm. Maybe I can help with understanding this timing “majic”.
On the old mehanical distributor and magneto type systems the firing point was set/adjusted at cylinder compressed piston top dead center or a specified number of degrees of rotation before this. Then depending on the engine, engine use, an RPM centrifugal internal to the distrubutor/magneto spark advance system advanced the sparking event from this preset point.
The crankshaft to camshaft relationships through the gears, chains or belt were always assumed.

With electronics the earlier systems like feed back carburated and throttle body injected worked the same with the mechanical spark advance system by system later being replaced with computor look up calculation tables.
Then enter sequential into each individual Port fuel injected systems. Computor has to be told then the camshaft/crankshaft sequences then to be able to individually activate that specific cylinders fuel injectors at thr right time. Depending of the base engine system this added in now a separete camshaft or crankshaft position sensor. Now they All had to have BOTH. WHY most fo the new vehicles have to be cranked through 2-4 full revolutions to positivly identify the detected cylinder event sequencing.
Later on “smart” self-learning electronics developed, better, more durable and faster capable sensors then allowed sensed active “ping” feedback to became possible. Now anticipated OBDII self-monitoring requirements made it manditiory to check for engine gear, chain, belt slack and wears with monitoring of the mechanical crankshaft to camshaft “synch” and timing events “scatter” with these two sensors.
After a point it just made better sense to set the crankshaft sensor at 45 or other degrees like 60 advanced to the actual #1 piston top dead center and then the electronics would just calculate from that point how much it would then “delay” trigger (actually still advanced from TDC) the spark event. This is how most small single cylinder engines now do this with coil pac internal RPM calculating spark “advance” versus cranking spark.
Yeah. I know. Clear as mud.

One of the very few auto engines to go through this full tech evolution was the 4.2/4.0L AMC/Jeep inline 6 cylinder from mid 60’s mechanical distributor to 2003 distributorless port fuel injection. Read a good service manuals on the ignitions systems for these engines give a good ignitions systems evelution possibilities story with the dates and individual installed systems setting adjusting needs.

Poor Internet Tech Op advisor will be answering based of the specific years and model engine use you give him. ONE year difference acrooss any of the system change over points will lead to a different Correct answer.

Regards
teve Unruh

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Chris:
Here is the link to the discussion:
http://www.justanswer.com/dodge/7yymo-dodge-dakota-hi-saw-reply-someone-re-indexing.html?al=1&utm_source=mar&utm_medium=email&utm_content=viewa_ln&utm_campaign=please_rate_48&r=emm|please_rate_48|35852696
It may or may not work, its a thing where they charge for the service.

Steve: Yeah mainly I was searching around because I got a 1994 v-6 dakota for cheap and wanted to get a straight answer, so I paid a little bit for the knowledge instead of stumbling around searching for hours. Looks like I might be able to advance the timing with a standalone ecu like megasquirt, but thats about the only option for advancing timing on the V-6 dakota. Once the engine wears out it’ll get the v-8 for sure. That said the v-6 dakota still has a decent power to weight ratio for woodgas purposes. Even with the timing unadvanced it will be acceptable to 70mph-ish on the flat. May have to run dual fuel in the hills and mountians. My original plan was to gasify a 2wd toyota truck with the v-6 motor, and would you believe it it weighs more than a dodge dakota by almost 200lbs and puts out 20 less hp.

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The Latest from the chrysler expert:

JACUSTOMER-6x0ved5v- says:
5:10 PM
What about on the 5.2 liter v-8 magnum engine? When you rotate the distributor eventually it gets to a point where it makes significant advance (40-50 degrees or so).

Dodgerench says:
6:19 PM
Nope, same thing. Ignition reference comes from the same fixed-in-place crank sensor back on the bellhousing. The big advance you’re seeing is what happens when spark crossfires to the next cylinder and that would be right around 45 degrees.

Pretty much settles it.

Steve, Since the 5.2 does not have a knock sensor, what does the computer reference for timing changes?

Hello PeterC.
You are correct that as a relitivly older early 90’s design Dodge did not knock sensor convert the 5.2L V-8’s. Actually none of thier early 90’s engines like the 2.0 SOHC/DOHC, 3.3 & 3.8 V-6, cast iron blocked 3.5L V-6 did either. Knock sensors got picked up in the later 2.7 DOHC, aluminum 3.5 &4.0L V-6’s, the new Hemi and all of the later engines.
My statement above was intended to be very generic covering all sold into the USofA/Canada vehicles late 80’s into early 2000’s.

Speed/Density with no air sensor or knock sensor the PRIMARY sensors are the MAP/BARO combo, the AirIntakeTemp, Coolant Temp and the Throttle Position in that order for ignition timing intial calculations. SECONDARY modifing sensor are the Crankshaft and Cam sensors.
Throttle Position is used for timing purposes as a Rate of Demand change requested - accelerator enrichment with some timing knock back. Will also work with the MAP like a distributor mounted vacumn pot for economy advancement.
Crankshaft for RPM. And for indirect ARE THE CYLINDERS actually making the expected power from the detected acceleration events? Average of no excpected crankshaft detected accelerations and then the computor will play with the spark and fuel to get a change.
Direct knock sensing is so much faster and allows GM like intentionally quick over-advance and slow step by step back off versus a slow creep up to an indicated over-advance point. Knock sensors add expense, complexity and more failure prone problems though. This same can be said of Air Flow sensor types also.

My points are even in the same engine and make family there were MANY changes throughout the 90’s and early 2000’s.
Only real way to know what will work is for someone to try it.
Wayne already has on the 3.9 Dodge V-6s tried advancing the distributor COMBO internal cam sensor and cap to the next terminal at a 60 degree jump. This was TOO MUCH for good woodgas power. The electronic distributor Dodge V-8’s at a 45 degree jump respond well.

Regards
Steve Unruh

If it has a distributor it will have to be advanced so it will think it is still in the stock “retard” setting and all will work normal and it won’t try to spark to the wrong cylinder which is out of it’s design parameters anyway. It thinks all is normal. I’ve noticed that Wayne has to turn his ignition off from time to time to tell his computers to f off. God bless the knock sensor !!! It works way faster than my ears and left hand
http://www.intergate.com/~mlarosa/images/woodgas/timing-control.jpg
http://www.intergate.com/~mlarosa/images/woodgas/93-distributor-lever.jpg
… Mike

When Sean was here over the weekend we put the timing light on a couple of the trucks . I was at the controls while Sean read the timing light. The 93 dakota jumps 45 degrees when I advance the time. ( I think after it is driven a mile or so it moderates some) .

The 94 , 318 ram reacts the same as the dakota.

The v-10 ram ( no distributor ) will advance on its own 35 degrees when switched to wood.

I have tested the advance on a 93 v6 dakota . When the distributor reached a certain point it shut the motor off quicker that shutting the switch off.

Sean will be posting some video of us driving the v-10 . I was showing him a slow idle of 150 rpm . At that point it does’t sound like a motor.

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Hey Wayne, I love how slow we can run the motor on woodgas. I usually don’t go below 300 or 400 rpm because it will sometimes fart and run backwards. Timing chain doesn’t like that … pop pop pop whoosh whoosh whoosh … Mike

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