Pulley-mounted crank trigger w/stock Magnum EFI - trigger notches?

[cudak888]

Let me set the scene for you:

I have a 1989 roller-cam LA 360 with Magnum heads on it; currently set up with a carb. It is a runner/DD, and I'd like to EFI it on the cheap; hence, stock Magnum EFI.

Obviously, sticking on a beer keg intake (or the P4510016 if I'm ridiculously lucky) won't be a problem. But that's not the issue.

Problem is, as an externally-balanced LA 360 bolted to a 904 transmission, I have no crankshaft position sensor notch in the transmission (not a problem), the external balancing means I'm more or less stuck with my existing B&M 10239 flexplate (problem), and the early TBI LA block does not have a mounting pad for the stock Magnum CPS cast into it ("oh shiyte" problem).

With this in mind, it just seems sensible to follow the rest of the aftermarket and weld on a custom crank trigger on my pulley.

However, everything I've seen to-date in regards to crank pulley triggers have been for use with Megasquirt and other aftermarket EFI systems - 36 tooth, missing-notch trigger wheels. High resolution, but delivering a different type of signal than the simple 5-volt on/off sync designed for the factory EFI.

Now, if I were to design an 8-notch ring (designing and laser cutting it is not an issue) for my pulley, mimicking the Mopar flexplate, and run with a suitable 5V sensor, should I be reasonably right in assuming this would provide the Magnum PCM the same exact signal it would otherwise receive from the pulse ring on the stock Magnum flexplate?

-Kurt

 

[TT5.9mag]

Sure you could. Your machining would have to be top notch (pun intended) and you could even use the stock crank sensor to generate the signal. The window size will have to be the correct size relative to the diameter of the wheel, which will be different from the oem magnum flexplate but with some math you should be able figure it all out. Good luck.

 

[cudak888]

Sure you could. Your machining would have to be top notch (pun intended) and you could even use the stock crank sensor to generate the signal. The window size will have to be the correct size relative to the diameter of the wheel, which will be different from the oem magnum flexplate but with some math you should be able figure it all out. Good luck.

Got it. There's a company I use to laser cut parts now and then; the results have always been within 0.5mm; probably tighter. This was for a stainless-based tool.

Theoretically, the notch size could be calculated by reducing the size of the original flexplate holes at ratio of the original flexplate diameter vs. the crank pulley diameter, correct?

I'd want to stay away from the OEM sensor for both space, neatness, and reliability. There are a few aftermarket, adjustable crank trigger sensor mounts out there that are affordable enough to make it worthwhile just to avoid headaches, and allow for excellent positioning options.

I don't think I'd want to rely on creating an adapter to work with the fairly flimsy factory mount - which isn't really optimized for use around the crank in the first place. It makes sense to splurge in this one area, IMHO.

-Kurt

 

[TT5.9mag]

Got it. There's a company I use to laser cut parts now and then; the results have always been within 0.5mm; probably tighter. This was for a stainless-based tool.

Theoretically, the notch size could be calculated by reducing the size of the original flexplate holes at ratio of the original flexplate diameter vs. the crank pulley diameter, correct?

-Kurt

Correct. The window size (in my little brain at least) should be proportionally shrunk the same percentage as the overall diameter. I can’t remember if they trigger on leading or trialing edge but there are pictures of Oscope graphs floating around on the Dakota forums that may help. I’ll see if I can find one. Maybe @KitCarlson would know.

 

[KitCarlson]

Correct. The window size (in my little brain at least) should be proportionally shrunk the same percentage as the overall diameter. I can’t remember if they trigger on leading or trialing edge but there are pictures of Oscope graphs floating around on the Dakota forums that may help. I’ll see if I can find one. Maybe @KitCarlson would know.

I don't have direct experience with mopar trigger wheels and sensors. I do have experience with the application of Hall sensors with targets. I do ground up ECU designs, including reference sensing, but I make what I want, and code to go with it. In your case the code is likely fixed, so the sensing means needs to replicate original signals in all respects.
The first thing, is capture cam, crank, and ignition primary signals on a logic analyzer along with timing measurement from timing light. That provides all necessary information to replicate, and properly setup.
Next thing is to accurately measure trigger wheel, and see how that compares to sensing signal. Typically widows shrink, because sensor triggers before and after tab, because sensor does not trigger at center point, it has diameter. Sensors vary in size too. Most Hall sensors sink current, go low with tab of target. Target should be anealed low carbon steel, not stainless.

 

[TT5.9mag]

I don't have direct experience with mopar trigger wheels and sensors. I do have experience with the application of Hall sensors with targets. I do ground up ECU designs, including reference sensing, but I make what I want, and code to go with it. In your case the code is likely fixed, so the sensing means needs to replicate original signals in all respects.
The first thing, is capture cam, crank, and ignition primary signals on a logic analyzer along with timing measurement from timing light. That provides all necessary information to replicate, and properly setup.
Next thing is to accurately measure trigger wheel, and see how that compares to sensing signal. Typically widows shrink, because sensor triggers before and after tab, because sensor does not trigger at center point, it has diameter. Sensors vary in size too. Most Hall sensors sink current, go low with tab of target. Target should be anealed low carbon steel, not stainless.

Thanks for chiming In. I knew you’d have good info to share. These don’t trigger off of a tab though. The wheel is solid and a window passes the sensor to trigger it.

Windows (8 of them) can be seen around the outer diameter.

 

[TT5.9mag]

So if the OP was to shrink the diameter to the size of a crank pulley do you think the relationship of the window size to diameter of the wheel will be a constant ratio?

 

[TT5.9mag]

This thread is where I found some good waveforms.
2000 5.9 CAM/CRANK Relationship Waveform and Fuel Sync - DodgeForum.com

 

[cudak888]

I don't have direct experience with mopar trigger wheels and sensors. I do have experience with the application of Hall sensors with targets. I do ground up ECU designs, including reference sensing, but I make what I want, and code to go with it. In your case the code is likely fixed, so the sensing means needs to replicate original signals in all respects.
The first thing, is capture cam, crank, and ignition primary signals on a logic analyzer along with timing measurement from timing light. That provides all necessary information to replicate, and properly setup.
Next thing is to accurately measure trigger wheel, and see how that compares to sensing signal. Typically widows shrink, because sensor triggers before and after tab, because sensor does not trigger at center point, it has diameter. Sensors vary in size too. Most Hall sensors sink current, go low with tab of target. Target should be anealed low carbon steel, not stainless.

Thanks for chiming in, Kit.

If I recall correctly (and this is from a long time ago, so take it with a grain of salt), the OBDII PCMs are flashable, but primarily for the purpose of removing unnecessary sensors, rather than altering the code that reads the Hall output.

I obviously won't have a chance to capture these signals, but I might have the chance to do so off a second-gen Ram - it's dependent on a neighbor's potential trade. While I have a reasonable grasp of what the logic analyzer will do (particularly given the data @TT5.9mag linked to at DodgeForum), I've never captured data with one before - nor do I know what would be an affordable unit.

Any links you might be able to point me to? I did see the SmartScope in that thread, but would like to hear your opinion.

I can get the ring laser cut in annealed 4130. Not a problem.

Found someone running a similar system on a /6 using one of those red generic hall sensors. I take it the choice of sensor will have an effect on the waveform just as much as the ring itself.
1966 Dodge Dart - Turbo slant six-Page 10| Builds and Project Cars forum |

This thread is where I found some good waveforms.
2000 5.9 CAM/CRANK Relationship Waveform and Fuel Sync - DodgeForum.com

So we're aiming for a nice square wave; nothing surprising there.

The back of my mind is wondering whether these printouts would be enough to get a rough idea of where to clock the ring.

-Kurt

 

[cudak888]

Well, this just changed the playing field:

HiPoTek Crank Sensor Adapter Dodge/Jeep 3.9/5.2/5.9 Magnum EFI/MPI

-Kurt

 

[KitCarlson]

Window makes high pulse. My best guess is keep window size same, don't shrink it, shrink metal part between. Shrink of window may lead to loss of pulse. There are 2 pulses per cylinder, roughly 45 degrees apart, less pulse widths. Similar to my system 45 degrees is used as advance reference, actual desired timing derived from that. In my system tab gives me high and low, so that identifies. The CMP is crucial with 2 pulses, it sorts out correct one. The problem with that, CMP updates per revolution. Since wave captures done on a engine not running correctly, we can only guess. Sync out, would be troublesome....

 

[KitCarlson]

Trigger point likely as high goes low, that is driven edge. Going high is by pull-up, slower and less precise. Lookin at windows in relation to crank timing may give clues. In my system one edge is base timing, the other is max advance. So, one window pulse may be base, other max advance. Since CMP is related to rotor phase too, seems crucial setting. I have no idea about setting that. My work has been mostly direct fire.

 

[cudak888]

Trigger point likely as high goes low, that is driven edge. Going high is by pull-up, slower and less precise. Lookin at windows in relation to crank timing may give clues. In my system one edge is base timing, the other is max advance. So, one window pulse may be base, other max advance. Since CMP is related to rotor phase too, seems crucial setting. I have no idea about setting that. My work has been mostly direct fire.

Well, I can't see there being much of a problem cutting out two test triggers - one proportionally sized, and one cut to the original flexplate size, and giving both a go.

However, with the discovery of that factory CPS mount, I'm now wondering if it'd be possible to use a neutrally balanced Magnum 5.2 flexplate with a converter balanced for the roller cam LA360.

-Kurt

 

[TT5.9mag]

That sensor mount that hipotec sells is probably the easy button here. If you’re using a 727/904 you’ll have to notch the bellhousing but that’s easy. And just use a stock magnum flexplate. I believe all of them are neutral balance as the balance was in the converter.
Edited to add:
I had to elongate one hole on the flexplate to match my 904 converter before I used the 46re.

 

[cudak888]

That sensor mount that hipotec sells is probably the easy button here. If you’re using a 727/904 you’ll have to notch the bellhousing but that’s easy. And just use a stock magnum flexplate. I believe all of them are neutral balance as the balance was in the converter.

I've never been one to buck the easy button if it gets me where I need to go with the least amount of fuss - provided it's not outright hackery. I like the simplicity of that bracket, and it doesn't look overly fussy.

Notching the bellhousing is easy, but my car is an ex-318 with its original 904 at the back. As such, my converter is still neutrally balanced; I used a B&M flexplate to get the roller LA360 to play nice. It's going to take another converter or I'll have to weld on some weights to the existing one.

-Kurt

 

[TT5.9mag]

I've never been one to buck the easy button if it gets me where I need to go with the least amount of fuss - provided it's not outright hackery. I like the simplicity of the bracket though.

Notching the bellhousing is easy, but my car is an ex-318 with its original 904 at the back. As such, my converter is still neutrally balanced; I used a B&M flexplate to get the roller LA360 to play nice. It's going to take another converter or I'll have to weld on some weights to the existing one.

-Kurt

Me either. If someone makes a nice,well thought out piece that I was planning on making and it saves a bunch of custom work down the line, to me it only makes sense.

 

[DionR]

I went down this road because of the lack of a flywheel solution (LA balance with a tone ring). Build a set up, ring on the crank pulley and a mount, but haven’t used it yet. Too many other projects.

 

[TT5.9mag]

I went down this road because of the lack of a flywheel solution (LA balance with a tone ring). Build a set up, ring on the crank pulley and a mount, but haven’t used it yet. Too many other projects.

4 speed? 5-6 speed? Can you post a pic of your tone ring?

 

[DionR]

4 speed? 5-6 speed? Can you post a pic of your tone ring?

4 speed.

Will post a picture after I get a chance to snap one.

 

[Crisd]

I know this threat is very old, but I like to revive it because I have the same need. What was the outcome of creating a new trigger wheel mounted on the front of the crankshaft?

 

[DionR]

Wow, after almost 5 years, you would think I would have had the chance to snap a picture. Guess I forgot.

Will get it done tomorrow.

 

[cudak888]

I know this threat is very old, but I like to revive it because I have the same need. What was the outcome of creating a new trigger wheel mounted on the front of the crankshaft?

Wow, after almost 5 years, you would think I would have had the chance to snap a picture. Guess I forgot.

Will get it done tomorrow.

Hey, look at it this way - I never tried any of the flexplate ideas either.

Speaking of which, I'd completely forgotten this thread - and wouldn't you know, I recently grenaded this very A904 and I'm building an A999 to replace it. In other words, I'm in the perfect position to notch the trans, install a Magnum flexplate, and replace the mystery meat converter from the junkyard with one that has the weights welded onto it for the roller LA360.

The only real PITA is getting an intake that will support this that isn't the ugly (and tall) barrel. I'd like to run my original air cleaner (but I also know I shouldn't ask for miracles).

I also notice HiPoTech seems to be out of existence at this point, so if anyone has that bracket or the dimensions for it, I'll either get or fab one up. My mistake, they simply didn't redirect their old website links:

http://[URL]https://hi-potek.com/hipotek-crank-sensor-adapter-dodge-jeep-3-9-5-2-5-9-magnum-efi-mpi/

[/URL]

-Kurt

P.S.: Anyone have a flexplate they can spare?

 

[MadScientistMat]

I'd be very surprised if the Chrysler ECU uses both edges of the notch for triggering. Usually when you see this, the notches are very long or clearly unequal sizes. It probably just uses the falling edge of the signal.

Although if someone has found it is sensitive to notch length, that would be interesting to know.

 

[DionR]

Here is what I came up with years ago:

The idea was that the sensor bracket would bolt under a couple of the water pump bolts. I had a different design that would have allowed for adjustments to fine tune it, but it got overly complex and (I think?) the idea on this one was that the holes were big enough to move it around.

I remember mocking it up on a friends 5.2 he was swapping into a Jeep, but the specifics are fuzzy. So things like if the crank pulley had to go on in a specific orientation escapes me now. Maybe my plan was to put the motor at TDC and bolt the pulley on at that point, checking the slot alignment at the same time.

I also remember using a JY Magnum to figure out where the sensor was oriented in regards to TDC, but I can't seem to find those notes right now. I feel confident that I used that info when we welded the tone ring to the pulley, but can't tell you what it was. Seems like 10 degrees either BTDC or ATDC for the trailing edge, but can't be sure.

This was using a G3 Hemi CPK sensor, but I don't remember which one. I think there are 3 different sensors through the years, and I can't remember why one made more sense to me than another. I know I still have the sensor and plug in a box, so if anyone cared I could dig it out and look up the P/N.

I don't remember if I scaled the notches or not. Sticks in my head that I concluded that the size of the slot wasn't important as long as it wasn't too small, but couldn't say why now.

Of course I never did anything with it. Since then (I think) there is an option for an LA based flywheel with tone wheel notches, but trying to verify proved to be unsatisfactory so I dropped it. There is also the idea of cutting a flywheel down and nesting a flexplate between the flywheel and crank (see Dead Dodge Garage). And then I got on the G3 bandwagon and sold the Magnum swap harness I built (and never tested) and PCM.

I still have the '74 Duster I was going to put it in. I even have a Hughes EFI intake on it with the injector ports plugged and a carb. I could see going down the road of Magnum EFI on that car after the Hemi swapped car is done and running, but I could also see getting rid of it if the Hemi car turns out like I think it will.

 

[DionR]

The only real PITA is getting an intake that will support this that isn't the ugly (and tall) barrel. I'd like to run my original air cleaner (but I also know I shouldn't ask for miracles).

I could have sworn I had pictures of A-Bodies with the BB intake fitting under the hood with a stock air cleaner, but now I can't find any. Maybe they don't, not sure now.