http://www.msextra.com/doc/ms3/trigger-wheel.html It looks like, in your case, with a missing tooth wheel on the crank, it depends on where tooth #1 is in relation to the crank pickup sensor when the crank is at TDC as to where the cam pickup in the distributor needs to be. The example diagram shows the cam signal coming in 40 degrees before tooth #1 is seen by the crank pickup. However tooth #1 is 80 degrees BTDC which puts the cam signal 120 degrees BTDC. If I looked at your pictures correctly, #1 tooth lines up with the pickup when the crank is close to TDC? Since you have some pickup adjustment (in the distributor) with the vacuum advance plate, you should be able to juggle enough stuff to get timing and phasing the way you need it. Are you eventually going distributorless? It would make this a lot easier Paul Just had a second thought If the distributor has a mechanical advance and you remove the stops, can you then rotate the rotor and lock it down anyplace you need?
Mark When using a missing tooth ring on the crank with the MS3, if for some reason you can't get the crank pickup to point at tooth #1 when the crank is at TDC, then you use the #1 tooth offset value to tell the system how far off it is. The trigger angle/offset value (different than the #1 tooth offset value ) is initially set at "0" and is used to fine tune the timing during run time. The cam sync pulse needs to lead the crank trigger pulse by at least 20 degrees for sufficient processing time (let's make it 40 degrees). This puts the cam sync pulse at the #1 tooth offset value + 40 degrees. So let's say you want the rotor phased at 30 degrees BTDC and the crank pickup actually points to tooth #1 at TDC for an offset value of "0", then the reluctor tooth in the distributor needs to point at the cam pickup 10 degrees before the rotor points to the #1 spark plug tower in order to have a 40 degree cam sync lead angle As you can see, as the #1 tooth offset value increases because of crank pickup location, the angle between reluctor tooth and the rotor pointer must also increase in order to maintain cam sync pulse lead angle over the crank trigger pulse and keep the rotor phased at 30 degrees BTDC. Paul
The MSIII showed up today. My missing tooth on the crank trigger is approximately 70* BTDC. Thanks for the link Paul, I have some serious reading to do. I am going to use a "fresh" HEI distributor that doesn't have any mod's to it, so I'll be pinning the mechanical advance in place on the new one, so I can do some "guestimating" on where to pin it after some reading and then pick the right tooth off the reluctor to leave and use the vacuum advance adjustment of the pickup coil to fine tune it. I do want to go distributorless eventually, but I'm not there yet. I have to sort out what coils I want to use (I'm cheap). I have a set of passenger side valve covers on the way (no breather or oil cap holes) so I can see about mounting LS style coils on the top of the valve cover, but then have to see about modifying them so a breather and oil cap can be added.
I got positive feed back from the MegaSquirt programmers that I just need the cam trigger to pop up 20*-40* before TDC, doesn't matter where, possibly even could be before 40*, but that window is is the best. The software is programmed to just recognize once the cam signal is triggered that the next TDC tooth on the crank wheel is going to be starting the intake stroke. Pretty simple and lots of flexibility in setting it up with my pickup coil arraignment. Just point the crank to ~30* before TDC, set the reluctor tooth to point right at the pickup coil tooth and call it good.
Yes, The software is programmed to just recognize once the cam signal is triggered that the next TDC tooth on the crank wheel is going to be starting the intake stroke. But you indicated that your TDC tooth is around 70 degrees BTDC on the crank. The cam signal MUST come before the TDC tooth reaches the pick up, so if you want the cam signal to be 30 degrees before the TDC tooth, which is at 70 degrees BTDC on the crank, then it needs be set at 100 degrees BTDC on the crank. That is exactly what is shown in the MS3 instructions. See half way down the page under: Missing tooth crank wheel and single tooth cam wheel http://www.msextra.com/doc/ms3/trigger-wheel.html After that is set up then the rotor must be set so it points to the #1 cap tower at the time when there is the most cylinder pressure which is around 34 degrees BTDC for naturally aspirated. That means that the distributor reluctor will lead the rotor by 100 - 34 = 66 degrees at the crank or 33 degrees in the distributor. This is where the relationship between the distributor shaft and the reluctor pickup needs to be adjustable. Paul
Right. I don't foresee a problem making that happen properly. There are points on the reluctor every 45*, I have adjustments on the pickup coil of roughly 20*. I'll be making the pickup coil adjustable instead of the reluctor, it's relative. In other words, when the rotor is pointing at #1, I can set the pickup coil such that the reluctor tooth has already passed the pickup coil or such that the reluctor tooth has not yet gotten to the pick up coil rather than moving the reluctor. It doesn't even have to be the tooth closest to the rotor point of course, I can pick a tooth pair 45* or 90* off off of that since there is only going to be 1 tooth, it'll be hard to get confused on the set up. To me the set up is going to be exactly the same as it was when the pickup coil was my ECU tach signal, only difference is 7 teeth are going to be missing and I'll turn the crank back to 100* BTDC, to set the pickup coil proper. Steps: 1) Set engine at ~30*-34* BTDC, turn distributor base so rotor points at #1, tighten base down. 2) Turn engine to 100* BTDC, rotate pickup coil to line up with reluctor tooth. So in effect the ECU is picking up the reluctor tooth right after the #5 fires and the missing tooth on the crank just after #4 fires (4-7swap) and is ready to go when TDC and #1 rolls around. I'm not seeing why the reluctor has to be adjustable when the pick up point is adjustable. If the pickup (sensor) was locked down I'd agree with you. This is the same way I set my trigger angle for the tach input when I ran off the HEI pickup coil. Point the timing mark at 10*, set the pickup coil with the teeth lined up, and the trigger angle was 10*. Set it at TDC, line the points up and the trigger angle would be 0*, likewise for 15*. Never pulling the distributor shaft or changing the rotor/reluctor relationship, but changing how far in advance the ECU got it's signal by moving the sensor pickup. Same principle, the ECU doesn't know if the reluctor tooth moved or the location of the pickup sensor moved.
We,re looking at reluctor timing the same way, I was just going about it a little differently. Your method of reluctor pick up adjustment is easier Looks good! Paul
I'm glad you understand what I'm doing. You make me doubt myself a bit :beer Which is good, makes me think twice as hard!
I appreciate you sharing your projects. I'm hoping you encourage others to go the EFI route. You do know Aaron has a MS3 for the Spider? Paul
Yeah, I was encouraging him to ditch the OE harness all together rather than making a fraken-harness out of the MS3 and OE harness. That OE harness looks like a spaghetti dish of wiring even I'd be leery of. Trouble shooting connections or grounds would be a nightmare, IMO. I keep my EFI harness separate from the stock engine harness in my car for simplicity sake. That Spider is one unholy amalgamation of parts and it is awesome for being so. No problem on the sharing. The fact my stuff runs as reliably as it does, for the large amount of miles I put on it, is testament to anyone can do it. My stuff is rides the fine line between simplicity and cheapness. If my wiring job works, then anyone can do it. (my wiring job makes professionals cry :laugh
Yes I know, the Accel is similar by using the crank offset for ignition timing vs rotor angle but then you just change your injector timing as needed and go from there, even in batch.
If you haven't checked your cam timing yet, assuming the intake and exhaust cam lobes are the same and symmetrical, 232/232, .512/.512, the intake and exhaust valves will be open the same amount (Cylinder #1) when the crank is at 4 degrees BTDC. As you turn the crank clockwise and approach TDC, the exhaust valve will be closing while the intake valve begins to open. The action is pretty quick at that point and you should be able to eyeball or use a short straight edge along the valve retainers to tell when they are even. This will let you know if you are close or way off. Paul
For those wondering what pmuller9 and I are talking about. Imagine all the teeth on the pickup coil and relcutor (distributor shaft) are ground off except the two I marked with a sharpie. The rotor doesn't move but the pickup coil will, hence effect where the cam will get it's signal relative to where the rotor points. So I'll find 100* BTDC (pretend that's the line that's lined up with 0* on the timing tab) Then move the pickup coil so the teeth line up. Piece of cake. I should pin or lock down the pickup coil, but running it with 8 teeth as my primary tach signal for 20,000+ miles, it never moved (no timing drift). Paul, when I was taking these pictures, it turns out the only limitation on the movement of the pickup coil is the wiring. It'll spin 360* if it wasn't plugged in.
It begins.....Again. Quoted from my project thread on the X-body board. ---------- Post added at 02:36 PM ---------- Previous post was at 01:49 PM ---------- I had made the fuel injector harness a separate harness from the sensors. So it was as easy as unplugging the injectors and pulling the harness out. I pulled the HEI pickup coil wire, aka cam sensor wire, with it. I'm going to just wiring in the wires that I need on this end. So just the 8 injector wires and the cam sensor wire for now. I'll leave the 8 spark control and other optional inputs/outputs out for now and will add them as needed. The old harness with the soon to be new harness.
Nice job on the D connector. You need to file the magnet and the reluctor poles until they are even with the base ring and nonexistent. Any change in distance between the magnet and reluctor will cause a change in magnetic flux and can cause a signal. There are 7 poles still acting at the same time and even though you have increased the gap they are still there with a 7 to one advantage over the one true pole. Another problem I see is that the original 8 poles acted all together to create a signal where there will only be 1 set of poles trying to create a signal. I always worked with distributors that had 8 reluctor poles on the shaft but only 1 pole at the pickup coil so it didn't matter if I eliminated all but one of the reluctor poles on the distributor shaft. I hope your setup works. Paul
Thanks. I hope it works too! This was/is my biggest question about it working, will the single point be strong enough to trigger it. o No: I'll find out. I shouldn't have any problem running the system in alternating/batch fire mode with the new set up while I datalog how the cam sensor is/isn't picking up. I filed them flush with the under laying magnet (that's how it got chipped), and the teeth are filed so it creates a slope away from the center. Plus MegaSquirt 3 has an error code log when it looses sync. It'll tell you what it lost track of, even if it was just for a half second. I'm not sure I understand how this would work at recognizing which tooth on the reluctor signified that #1 was coming up, as every pole on the reluctor would have equal influence on the pickup coil. In retro-spec, I probably could of left three or four poles on one side of it to increase signal strength. I have a spare reluctor or two in the basement and pickup coils are cheap from the parts store (and I may have a spare one in the basement). It's only a 30 minute job to swap them out, maybe a tad more if I have to pin the mechanical advance mechanism on the spare reluctors. Going to find out!
Leaving only 1 set of poles is correct because you only want 1 pulse per distributor revolution so what you did is correct. Leaving more than 1 pole set will give you multiple pulses per revolution. I just wanted to be sure there are no other possible pulses occuring at any other time so I suggested removing all the material you can from the other 7 poles. It is great that the MS3 logs errors for you to view. I used MSD distibutors that had 8 large reluctors and one pickup coil originally intended to trigger the ignition. So when I went to crank trigger I simply ground off 7 reluctor poles and used it for the cam sync pulse same as you are doing. Paul
Well I made the change over to sequential this morning. I bumped the fuel pressure up to 60psi to bring the duty cycle number down to try and stay out of the overlap period at cruise. I currently have the injection timing locked across the whole RPM and MAP range such that the end of the injection stops 5 crankshaft degrees before the intake valve closes, so as duty cycle goes up it adds time before then. It's going to be a while before I get a good highway test though, the car is going in for paint shortly.
There is air reversion going back out the port just before the intake valve closes at low rpm. My thinking would have been to lock it in just as the exhaust valve closes and start the injection period from there. At large duty cycles there would be spray after intake valve closes waiting for the intake to open the next cycle which is about the same as spraying early because of a large duty cycle the way it is now. What are your thoughts? Paul
Well Paul you made me re-visit my calculations and it's a good thing I did!! My spread sheet was based on 90* crank throws not 180*! So all my math was off. I may drop my fuel pressure back down to 43psi with the new results, because I only bumped it up to tighten up the DC because my bad math said it would be a good idea. I am also aware of the philosophy that higher pressure is better for atomization, I'm just concerned about the fuel pump's abilities and longevity. Basically I was using the 720* of crank rotation to match up against Duty Cycle which is calculated off 720* of crank rotation. You mentioned some reversion at low rpm before the intake valve closes, so I put a field in there to show what part of the 4-stroke cycle the valves were operating under (when I noticed my error!), and I see what you mean by how long the intake valve is open under the compression stroke. So doing some figuring, if I lock the injection timing to end at when the piston is at BDC then I have up to 24.03% Duty Cycle to work with, which is far over cruising requirements. So datalogging duty cycle (at 43psi fuel pressure) I average 8.5% duty cycle at 2200rpm cruising, so taking that number, it comes out to 61.2 crankshaft degrees (out of 232* the intake valve is open). So I think I'm going to split the difference and set the middle of the 61.2 degrees at around 74* ATDC (peak air flow pull), so lock it at 30.51* before that, or rather end injection at 103* ATDC. Having it locked that way will work well for idle through cruise at minimum. I can change when the injection starts a table, so as I datalog duty cycle exceeding 8.5%, I'll move the end of injection to 180* ATDC (aka BDC) up to 23% duty cycle so it'll only inject during the downward stroke. Then once the duty cycle exceeds 24% I'll take the end of injection to 226*, aka the closing of the intake valve. From about 32% Duty Cycle and upwards the injection will start before the intake valve will open. Here is an example of the injection timing table if you haven't seen it before. The tuning software (TunerStudio) lets me make a scatter plot of datalog points, so I can plot duty cycle as it falls on the VE table and then I hope to back calculate where I'd expect the phasing to be. Of course I've been told repeatedly that at WOT phasing is never what you expect it to be. (off a google search) **I ran the numbers as if the cam were installed straight up, which I'm sure isn't the case. I'll also likely scale the whole table from my "calculated one" to what pulls the most vacuum. At least in the idle to cruise parts of it. Thanks again for making me think :TU:
