Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Is this Right

Off Topic Discussion

Forum Posts



Tech Articles

If it's not really about tuning or wiring. Then it belongs in here.

= Resolved threads


On Mon, 15 Aug at 9:48 AM , Noxqus wrote:

There are so many articles on setting up a crank trigger for EFI which makes it too hard to understand. DIY is probably the worse and my luck is that is the ECU I have. They try and instruct you how to do it but they do it in such a way that by the end you don’t know what they are talking about. They try and fit in the article every car on the planet, well I only have one. So this is what I have. 1973 hatchback Vega with a 383 dart block SBC. I have purchase a Holley dominator intake setup for EFI injection. Being DIY instruction doesn’t make sense, I used Holley instructions, but there are a couple of them. So here is what I did. I put the crank @ 60 BFTDC on the compression stroke. I made a holder for the Hall Effect sensor, also Holley, and positioned it so it is starting on the tooth @ 60 degrees.

So being I want to run sequential and a distributor, I modified a GM distributor with a Hall Effect sensor, also Holley and backed the crank up to 195 degrees BFTDC and adjusted it to just turn off the LED on the sensor at that point.

Attaching Michael's images

Attached Files

Hi Michael, I'm not too sure of your actual question here? It looks like you've got everything about right to me. Every ECU is a little different and most of what I deal with aren't overly fussy about the location of the missing tooth. However in the case of Holley if they're advising 60 deg BTDC (pretty standard) then obviously you want to take that advice. As for the single sync inpput from the dissy, this just needs to be located away from the missing tooth whcih it sounds like you've done. What is the issue from here?

Being I have a distributor and going to run an ECU, I'm guessing I will no longer need the Grid. I have an MSD 6AL-2 I'm guessing the ECU will run it, but I really don't know.

With the ECU this will control the timing so you just want a fixed distributor (no mechanical advance system - or if it has that then it needs to be locked up). The timing is then controlled by the ECU firing the coil.

Well I have been just messed up here with this basic timing set up. I have tried Holleys set up and have used part of Haltechs ideas to get this going have moved forward two steps to the finish line but have encounter a wall that makes no sense but is blocking the line. DIY instructions start with one set of steps that lead to different vehicle leading you away from what you are after. Holley instructions for cam sensor go like this. Using Hall they believe that the hall signal should shut off at 195° BTDC. Scott at Haltech says for rotor phasing and base time you should set rotor to point 20° BTDC line should be set at TDC. TDC is where the Hall sensor is positioned. DIY says for offset count the number of Spaces with the engine set to TDC 0° to tooth #1. So now I have three company instruction on how to set base timing. Problem is this one is for a Ford V-8, 4 cyl and V-6, but they are just numbers, right. So here are the steps I did to setup this V-8 Chevy.

1. Pulled # one plug, rotated engine clockwise until cylinder blew my thumb off. Continued to rotate until 20° BTDC mark arrived at TDC (The Hall is dead center at that location.)

2. Placed distributor cap that I cut a Huge window on side, at #1 location and a hole on top also. Removed mounting bolt lifted distributor and repositioned it with the rotor pointed directly in the middle of #1. Replaced mounting bolt and locked Distributor down.

3. Rotated engine counterclockwise until 195° line on engine landed on TDC 0°. Removed Distributor cap and adjusted Hall to where it just shut off. Locked it down and put on Good cap and installed wires to the firing order (18436572)

4. Here is where I think I may have a problem. Rotated engine to TDC 0° and counted spaces from there to tooth#1, which is the first tooth passed the missing tooth on a 36-1 wheel. (12 Spaces =120°)

5. Turn PC on and connect to Tunerstudio. Click on Ignition setting - Ignition options / wheel decoder. Being I can't seem to get pictures to post I will give you what it says left side slot number from top to bottom.

Left-1 Toothed Wheel ( The right side I will give First 5) Right-1 Fixed timing

left-5 Off Right-1 1st Deriv Prediction

Left-7 1 Right-3 20.0

left-8 Rising edge Right-4 6.0

left-9 going high Right-5 10.0

left-10 single coil

left-11Tacho out

left-12 CMP

left-15 dual wheel with missing tooth

left-16 36

left-17 1

left-18 137.0

left-19 Crank wheel

left-20 Rising edge If this is cam Hall the signal is led off no voltage

6. After making sure the ECU has this information written I start the engine. After about 4 cycle it lights off and revs up I would guess about 2000 rpms I'm guessing because I'm running to the front to shine the timing light on the tooth wheel which I have painted a white line on 20°. The engine within a few seconds starts its descent. The reason for this unorthodox way to do this, there is no radiator in the car. Why you say because the timing marks would not be seen. So run time is short. As expected, the marks did not line up, but the engine started and stayed running with the rpms at (900 rpms) which I put in somewhere. After turning the engine off several times, I managed to get the timing mark within 10°s of being lined up, I try to go below that 10° it shuts off. (so 137° is in Offset) So now the problem, when you start increasing engine speed the timing mark starts walking counterclockwise the more rpms the farther it goes.

So I'm sure everybody is saying what the hell is he doing (Answer) I don't know and I have been doing it for a long time and it has cost me lots of $$$$$$$$$$$$ and have moved 2 steps. I guess I could enter it in a bicycle race.

OK, that seems quite messy, but some questions to clarify.

EXACTLY which kit/conversion are you using, there are many options and without knowing that, everyone is working in the dark.

You say you're using a distributor - have you locked it in position so the advance doesn't work? If you haven't, the ECU and distributor advances will be in conflict.

The missing tooth is usually set so the sensor is triggered by it at least 60 BTDC, with the ECU counting from that for the TDC position - I understand there can be resolution problems it placed close to the TDC point. Regardless, you need to confirm the TDC position the engine is actually at is the same as the TDC the ECU is working from - this is important.

You then need to check you have the correct crank rotation for the firing - which you have or it wouldn't start.

If you could clarify the moving counter-clockwise, depending on what you mean that could be basically correct operation, or the opposite?

What I bought was the DIY ecu and harnesses. Injectors were sourced elsewhere; distributor was bought new gutted then modified with the Holley Hall sensor. Wheel, DIY, Holley Hall, Holley intake, Promaxx heads, EGT ECU Masters controller, Blaze thermocouples, Headmen headers, GM sensors. I made all the harnesses on the engine for injectors and disconnects to remove the engine with the harness on it. Look I'm not a professional anything and never had enough resources to have the best of anything. As for the counterclockwise with the engine running timing light pointed at the tooth wheel 20° line marked and visible. You increase the rpm, and that line moves to the left. The faster it goes the more it moves. Let off the gas it moves to the right but not far enough to reach the Hall sensor. It has to be the ECU moving it as the distributor shaft has two things on it, the rotor and the magnet for the Hall nothing else in the top under the cap. But as you see the ECU is set to Fixed timing. The trigger wheel was originally set so tooth #1 was on TDC but I found out that was wrong, so I turned it clockwise one bolt hole. Chevy has three which now moved #1 to 120° ATDC. Chevy rotates clockwise, Scott at Haltech says setting up on TDC is wrong and need to set at 20° BTDC so you have enough rotor swing either way to cover the timing. Rotor Look at this from Scott this is what I did with the distributor. You will also see that timing light on the video doesn't move at all no matter what the rpms are. This video actually got my engine to start and run. Before it started but was way off and loud pops were going on from not being lined up right.

here is what it looks like.


Ah, that's helpful.

Looking at it like that, there are a couple of things that may be significant - the crank sensor is at an angle, so will not get as clean a signal, and there appears to be quite a big gap between the disc and the sensor, which will also weaken the signal - I'd suggest modifying the mount to get it at 90 degrees, then check it's got the correct air gap.

That would also fit with the timing being retarded as it will affect the count - effectively adding teeth and causing the ECU to trigger the coil later.

Oh, and double check the wiring is the right way round, just in case.

The air gap is 0.040 within 0.002 all the way around. This Hall sensor is small diameter, so the sensor is almost the same size as the tooth.

Was the timing locked in the ecu when you done that video or was the ecu commanding advance?

Assuming you are using the MSD box to drive the coil, is your ecu setup to output a rising spark edge? What ecu do you actually have?

Yes Timing locked at 20° Yes setup for rising but have now changed it to falling as I read use falling with Hall sensor. Just don't know should I also use going low instead of high. This is a AMP/EFI ECU ultimate. I will try this Monday AM to see if that corrected the wonder. I'll post results.

Im not talking about the trigger sensor edge, im talking about the edge that the ignition output pin uses to command a spark. The MSD needs a signal that effectively acts like a set of points - ie low voltage/points closed means "charge", high voltage/points open means spark.

Did you use the tach output and set up as per the manual?

What you have there is how I have this setup. I changed to falling edge and it doesn't start at all so I put it back to rising. Everywhere I see setting up from TDC and the #1 tooth 50° away. I think what is confusing me is this distributor. When I ran a grid i set the timing to 40° advance and set the grid so it knew that and put in what I wanted to start at and what to got to when running down the track. You would think this is the same thing, the ECU just does it. There is only one thing that I know of that can move that timing mark the ECU. The distributor has nothing in it accept a shaft, Rotor, and a magnet on the shaft hall sensor on the plate that's it. Well I can't include the tune file or the data log unless you know of a way.

Tune Data Log Here is the tune and data log, You can download the tunerstudio and the log viewer from Downloads (tunerstudio.com)

To load the tune and see the data log free. To get full version is a cost to register.

Although their manual suggests spark output "going high" for MSD, really the only logic that fits the extreme timing drift in the advance direction with RPM like you are observing is if the ignition system is firing off the wrong side of the dwell period. Just to humour me, can you do a quick test with the spark output setting changed to "going low" and see if you still have a lot of drift. You will likely need to set your base timing again.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?