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Mk1 1.8 Cam Angle Sensor - Does it support sequential injection unmodified?

Old 01-04-2019, 06:27 PM
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Default Mk1 1.8 Cam Angle Sensor - Does it support sequential injection unmodified?

Hi,

Looking for a bit of clarity on whether a stock, unmodified mk1 1.8 cam position sensor can support sequential injection without internal modifications. Can anyone help? I have seen some info that says it needs modding, removing one of the magnetic pick ups, other info saying it doesn't.

For info I am running a MS2V3 ECU in batch fire mode currently. I understand I need to do some internal mods to the ECU, to provide a pin for the second CAS signal, I am happy with what needs to be done there. Looking at the stock wiring diagrams for a 1994 1.8 there are two signal wires from the CAS and each injector has a separate feed into the ECU - so this looks promising for supporting sequential operation.

The reasoning behind it all is that I am looking at building a high comp NA engine with some fairly reasonable cams. I would to do all I can to help idle and emissions for MOT (I am in the UK). Also, I often experience starter kick back on my current engine, which is not high comp. Reading up through the MS manuals I think some of this is to do with only using the low resolution signal from the CAS meaning the cranking timing is not as accurate as it could be. Using the high res part signal too will hopefully help this issue.

Hopefully I am not talking rubbish - this is information I have been picking up from the MS manuals on the 4G63 type CAS.

Help would be appreciated.

Tom
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Old 01-04-2019, 08:15 PM
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I think I saw in one of the recent MS3 release notes that they added additional 4G63 support. Don't know anything about MS2.
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Old 01-04-2019, 09:45 PM
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I think you're talking rubbish. Your MS should already be reading the CKP and CMP (crank and cam) signals.

What the MS2 lacks is additional fuel injector drivers. Those have to be added in - and on the MK1 (NA6's) the ECU wiring needs to be modified - NA6 is also batch fire, so the 4 wires for the injectors are merged into 2. NA8's are sequential and have individual inputs to the ECU.
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Old 01-05-2019, 12:40 AM
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Originally Posted by Tchaps View Post
For info I am running a MS2V3 ECU in batch fire mode currently. I understand I need to do some internal mods to the ECU, to provide a pin for the second CAS signal
All 1990-1997 MX5s used basically the same cam sensor. They all have two outputs. Every Megasquirt I have ever seen installed on a first-gen MX5 read both of these signals, and yes, it required a hardware modification on all of the early Megasquirts, as they were originally designed to read a single sensor (typically the points in a distributor-based engine, or a crank-mounted missing tooth wheel.)

Honestly, I didn't even know that it was possible to make an MX5 engine run with only one of the two sensor signals. I've never tried it, mind you, but modifying the MS to read the second signal is considered to be a standard part of any MS1 or MS2 installation on an MX5.

That having been said, the MS2, like the MS1 on which it was based, was only designed to drive two injector channels. You can modify it to add two additional channels, allowing fully sequential injection. Details here: Sequential Injection Code for MS2
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Old 01-05-2019, 03:16 AM
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Thanks guys. Got a few jobs on the car today so I will check I am seeing both signal wires going to the MS.

Guess I am looking for that second signal wire going into SPR1-4 and then a jumper wire going to JS10 inside the ECU, And doing a log of the tach input would also be my friend here too - just to check everything is set from an inputs point of view.

Yes I have the additional drivers covered. Went with the 4 channel driver board from JBperf, and I have seen what I need to do to the main board to get that to work, and my car having a 1994 loom I already have the wiring in the car to control individual injectors.

Hopefully it will be easier than I first thought. Thanks
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Old 01-05-2019, 10:11 AM
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Your starter kick back is most likely due to your cranking advance settings. Add or subtract a few degrees and one should improve it. Keeping going that direction until it’s gone
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Old 01-05-2019, 12:25 PM
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Taken a look at the wiring this afternoon. The CKP and CMP are joined together to a single wire before connecting to the MS, so I am reading both signals just in one input. So query solved. Just need to add the drivers and we are away.

On the starting timing- I am actually already at -10 crank timing!

I used to have a bit of kick back occasionally on my old engine (which drank oil). When I built the current engine it became a real issue and I had to pull cranking timing back to the minimum allowed. Guess having functioning piston rings and valves that held compression caused the issue to get worse. I thought it could possibly be reading the low res part of the CAS when I was researching sequential injection. It isn't too annoying, it does it about once a week - so maybe 1 in 10 starts (from bone cold). It is more likely to happen on a cold day.

The starter motor is old, so it might just that getting lazy in its old age. I'll make sure I put a new one on when I put the new engine in hopefully early 2020, unless it ***** itself before then.
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Old 01-05-2019, 12:37 PM
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Haven’t put a lot of in depth research into it besides knowing cranking advance helps, but I’m pretty sure it also has to do with your ignition table. Decrease the values in the lowest rpm column around 100kpa and I think that’ll help.
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Old 01-05-2019, 01:59 PM
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Originally Posted by Tchaps View Post
Taken a look at the wiring this afternoon. The CKP and CMP are joined together to a single wire before connecting to the MS, so I am reading both signals just in one input.
Where are you seeing this? There are 2 separate wires for cam and crank signals. They stay separate all the way to the ecu.
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Old 01-05-2019, 02:21 PM
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Thanks Curly I will take a look at that bit of my spark map.

Hi SpartanSV the two CAS signal wires have definitely been soldered together into one wire where my MS splices into the stock loom.

Last edited by Tchaps; 01-05-2019 at 02:23 PM. Reason: can't spell
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Old 01-05-2019, 02:25 PM
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Originally Posted by Tchaps View Post
The CKP and CMP are joined together to a single wire before connecting to the MS, so I am reading both signals just in one input
This is, quite literally, the first time I have ever heard of this being done.

I honestly don't know how your engine is even running.



Originally Posted by Tchaps View Post
On the starting timing- I am actually already at -10 crank timing!
Admittedly, I'm digging back into memories which are over a decade old at this point, but I seem to recall using cranking timing of 0, or even positive numbers, with good results back when I was building iron-age ECUs for stone-age engines.
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Old 01-05-2019, 02:43 PM
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Not really sure what to say... Its been running this setup for 3 years as a daily driver with no problems!

In the MS manuals under the 4G63 section it talks about one of the signal wires going to the normal tach in pin, and building a circuit for the second signal that feeds into JS10.

Does the MS just then essentially merge these two signals into one anyway? Which is why you have to make sure the signal pulses from each signal source are offset - otherwise you would mask the pulse from one with the pulse from the other source and the ECU would loose sync.

By having the wires joined pre ECU I would just be feeding this combined signal into one tach input, the MS then either ignores the JS10 or it adds no signal to my already combined signal and reads it with the 4G63 decoder.

It sounds plausible to me - but I am no expert - but I do know my car works!

On the cranking advance tuner studio recommends 5-10deg advanced.
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Old 01-05-2019, 03:06 PM
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You have more reading to do.

The megasquirt looks at cam and crank signals separately. They don't get merged together anywhere.
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Old 01-05-2019, 03:14 PM
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Yes definitely a lot of reading to do on electronics.

Out of interest, why is it that the joining together of these two signal wires is meant to cause an issue?

Is it a possibility that my MS is only picking the part of the signal it expects to see out of the joined feed and is then ignoring the spurious second signal that is added to it? Is that even a possibility? I would have thought it would just confuse the MS and I would have major running issues - which I don't.

I'll have to do a log to see what the MS is seeing.
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Old 01-05-2019, 03:58 PM
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Disclaimer: After this post I'm going to step back from this thread a tad, as you are either:
  • A far smarter man than I,
  • God, or
  • A fool who has the Grace of God on his side.
Originally Posted by Tchaps View Post
Does the MS just then essentially merge these two signals into one anyway?
No.

CKP gives the ECU information as to where the crankshaft is, which is the primary variable in computing igniting and injector timing. (Think: stuff that matters relative to TDC)

CMP tells the ECU where the camshaft is, which is how it figures out which coil / injectors it will fire at any given time. (Think: stuff that matters relative to whether the cams are "up" or "down" for any given crank cycle.)

The ECU uses CKP to figure out WHEN to fire the spark plugs.

The ECU uses CMP to figure out WHICH spark plugs to fire.



If you seriously have them both wired together, then you are a far more innovative man than myself in terms of making software compensate for broken hardware.
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Old 01-05-2019, 04:32 PM
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maybe wire your injectors and coils to 1 wire too?
just have the MS trigger ALLOFIT
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Old 01-05-2019, 04:52 PM
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I am most likely missing something in all this, and I am not trying to tell people with more experience myself that I have magically created a new way of reading engine positions.

Something is obviously amiss - I need to investigate further.

It wasn't me who installed the MS, it was a tuner who does who knows how many of these installs a year. I'll give him a ring next week and see if I can confuse him too.

I would rather make sure I have all the software / hardware working correctly and I have a full understanding of it before I start adding drivers etc.

I'm also not wanting to peddle misinformation on boards.

On the topic of my original post - can the CAS support sequential injection - I got my answer and thank you very much for the information.
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Old 01-05-2019, 06:25 PM
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Originally Posted by Tchaps View Post
It wasn't me who installed the MS, it was a tuner who does who knows how many of these installs a year.
In that case, I would bet you $1 that the tuner built and installed the MS properly. Which is to say that it is reading CMP and CKP seperately.
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Old 01-05-2019, 06:41 PM
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It would certainly explain why the car actually works. I'm going to take another look tomorrow and continuity test it all.

I'm probably being a tit and looking at the wrong wires or something. Hopefully all will become obvious.
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Old 01-06-2019, 05:09 AM
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Yep I was being a tit.

The two signal wires aren't connected - they run to the normal DB37 pins.

What I thought was solder turned out to be a tiny bit of shielding poking out of the loom wrap.

(Non)mystery solved, godly intervention does not control my timing.
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