...maybe. Forget the electronics, I'm thinkin' hardware here Sportsfans.

This might NOT be doable, but bear with me for a minute because it MIGHT be doable. Given that some of us would like a mild timing option for towing and MPGs, I was wondering what it would take to move the cam sensor slightly. As I understand it, this sensor is examined at startup to initialize the injection timing and then is used only as a back up speed sensor to the crank sensor.

I think the way the crank sensor works (from reading the service manual) is that it has many teeth, but no TDC detection. The TDC detection comes from the cam sensor at startup. By looking at a diagram of the crank sensor wheel, it looks like it has 60 teeth. These teeth are looked at like an incremental encoder as they go past the Hall Effect sensor. With 60 teeth, that gives us a 6° increment.

The implication is that:

IF the crank sensor performs only as an incremental encoder and,
IF it is in fact counting in 6° increments,

THEN if we can find a way to either move the cam sensor the equivalent of 6° advanced, OR index the magnets on the back of the cam gear by 6° advanced, we might have a slick, code free, way to advance our timing by 6°!

This is likely to invlove some machine work on the rear timing cover. I'm NOT saying this would be easy or even possible, but there are enough sharp cookies out there to noodle on a possible solution.

Whaddya think??

100 Proof

 

huh?

 

Like I said, not sure it will work, but you sure couldn't prove that by what I read in the service manual. BTW, welcome aboard!

100 Proof

 

maybe. try it and let us know

 

hes looking for other people to try it who are smarter then him "or dumber" to ruin there trucks :/

I dont have nothing to do it with and am happy with mpg and towing ... :/

 

I think the idea sounds reasonable...but I would like to hear the "expert" opinions out there!

 

Journier - why are you hating on 100 proof? He never said someone else should try it. Personally I like the thought process and if enough people read this post there will be some creative feedback not from an unsolicited critic.
BTW - you mention he is looking for "someone dumber"???
With sentences like "hes"(he's-it is a contraction), "then"(wrong word form), "there" (wrong word form again), "dont have nothing" (just plain borderline illiterate).
I think he found his man.
BTW - do you have an occupation that allows you to afford an 04.5 3500?


Go for it 100Proof. I wish I had some more time to look into this. I have a mill and a lathe and other tools a plenty along-w-a FSM. Hopefully I will look at it soon. Maybe keeping the crank sensor how it is (it's for starting only?) and putting the cam sensor on a tiny servo ala air mix on EFI throttle body Dakota I had would allow manipulation of it???

 

Actually, if it works the way I think it does, you shouldn't have to touch the crank sensor, only move the cam sensor by 6°. I'm heading out for the 4th, but if I get some time next week, I'll try and R&R the cam sensor to explore the possibilities. This is not something where you can dial in any timing change you want. It would only be in 6° fixed increments.

The way I think this works, the crank sensor is used for engine speed sensing and has no "home" or TDC measurement capacity. The cam sensor has the ability to find "home" or TDC. It has a magnet on the back of the cam gear that must pass past the sensor to generate that signal. This is why the electronic controlled engines seem to crank longer, that magnet MUST pass the sensor at TDC.

I'd really like others to read the pertinent sections of the service manual to see if they agree with my assumptions of how this works or point out where I missed something.

Guys, I'm just exploring options here since the box solutions don't seem to be materializing.

Thanks for the kind words ppsi.

100 Proof

 

100proof,

That's exactly what I was thinking, only I don't have the service manual to check with. If you are right, and the tdc is determined only by the cam sensor, then moving it will yield the results you suggested. I wonder, though, if it is limited to only 6* increments. The question is, is the position of TDC linked to a particular position on the tooth/valley signal picked up by the crank sensor or is it simply set at a relative position.

If the electronics pick point X as TDC and say that point X is here and assign that point relative to the information being received from the crank sensor, the 6* steps would not be fixed.

If on the other hand the electonics pick point X as TDC and then compare the data from the crank sensor to set timing, then the 6* increments would be set.

I think it is possible that on poor mileage trucks the cam position sensor or the trigger magnet, or, on the really bad ones, both, are positioned to further retard timing.

Also, depending on how the signal is read, having a stronger or weaker magnet may influence when the signal is triggered. It's common for magnets to have 5% tolerances, which can mean 10% difference from one end of the scale to the other.

Do we know what attaches the magnet to the cam gear, how it's location is fixed, how the sensor location is fixed and the acceptable error tolerance for both? On most systems (trucks) the errors will average out on both sides and they will fall close to the mean. Stacking all the small percentage errors on one side of the equation (ie: the retarding side) can push performance down significantly. It stands to reason that if you build enough trucks, some of them will end up in that condition.

I guess I need to get myself a service manual because I sure wish I knew more details about these particular motors. As far as I can tell, your resoning is spot on, and 6*, whether fixed or not, is not an unreasonable amount to shift timing. You sure have my attention and I look forward to hearing more about how to practically make these mods. Pictures would be nice!

 

There is a rationality check between the two sensors. If one sensor reads 6 degrees different from the other, you will go into a derate.

 

bigblock2stroke, "There is a rationality check between the two sensors".

That's what I was thinking. I have an early Harley TC with crank and cam hall effect sensors. It sputtered a little once when I got some bad gas, which set error codes for cam and crankshaft out of phase. I was surprised, since it was my understanding that the cam position sensor was only used to determine what cycle the cylenders are on (exhaust as opposed to compression, and so on).

I know the Harley is an anicdotal comparison at best, and 100 Proof deserves credit for thinking outside the box, but I would bet moving/changing the timing of the cam sensor would put the computer into limp mode, at best. Then again, I'm not an expert, or an engineer...

 

If that's the case, maybe you need to move both sensors?

100 Proof

 

when i had read his original post it sounded like with his last sentence, he said he was looking for other people to help him? Im SORRY PPSI my sentence structure matters so much to you, i will make sure its perfect for now on, since it matters.

and i was not posting in reply to 100 proofs post at all, i was posting to the guy that said (HUH?) post.

and when i said dumber i meant not perfect, you can always make mistakes.


Btw my occupation at McDonalds doesnt have anything to do with this !!!! :/

 

Quote "If that's the case, maybe you need to move both sensors?"

Say 6* on the crank and 3* on cam? I think that could work. Perhaps one of our experts could cime in?

 

You describe it as being like a gear. Rather than moving magnets around on it, why not just advance it one tooth to get the 6*? I don't have a service manual, so I'm not sure if a guy could do this, but it would keep everything in the same spot.