Crank sensor offset - getting it right

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
Alex DTA
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Re: Crank sensor offset - getting it right

Post by Alex DTA »

SMR wrote: Alex - perhaps a couple of busg in DTASwin (I'm using v90.22);

1. Sometimes when I went to enter numbers in the deadtime table, the decimal places dissapeared and I was left with a cloumn of single digit numbers. I deleted that map and used a previous map and all was well. this happened a few times?

2. When saving maps, the comments box sometimes appears to lose most of the text info?

I can't reproduce 1. Let me know the steps to reproduce.
2 was fixed in 90.23. 90.26 is now on the website.
SMR
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Re: Crank sensor offset - getting it right

Post by SMR »

Hi Alex,
I'll see if I can get it to do it again - can't repreduce it off-line though. I'll drop you an email with the details if I can get it to do it again.
Thanks
Steve
SMR
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Re: Crank sensor offset - getting it right

Post by SMR »

Well, no luck re-producing the deadtime box issue, despite trying various routes/maps - sorry Alex!

Had a succesful trip to the dyno at Daytuner - despite poor atmospherics (92 degrees humidity, 23 degC air and low pressure) which gave low numbers, we made gains everywhere by leaning things off considerably, and tweaking the timing. Putting in the actual measured injector deadtimes did ov course richen everything up substantially, but the map was aready rich.

I had a couple of oil leaks round the cam cover so engine out job, but it gave me the opportunity to make a new cam trigger wheel; machining down the previous "negative" tooth wheel so it has one single "positive" tooth. This appears at 10 teeth (i.e 100degrees BTDC) according to the crank scope. The "cam pulse received" counts up nicely, the tooth counts shows as 10 but no cam angle number is shown.

Now the weird part - sequential injection works - rev it past the 2000rpm and all is well - it keeps running.
BUT, it won't accept "Coil per plug" - On previous trials, I had always tried both coil-on-plug and sequential injection at the same time, which always made the engine stall once rev'd above the 2000rpm change-over point.
This time I tried only the sequential which worked, and then only the "Coil per plug" which failed to work.

So perhaps my single inverse tooth trigger would have worked, and something else is amiss with the spark side of things?
All injectors and coils are wired up in firing order for the ECU outputs and the correct cylinders, so don't know what's up!
stevieturbo
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Re: Crank sensor offset - getting it right

Post by stevieturbo »

A tooth or a gap should work, it will still create a usable edge.

And in diagnostic display when running, does it not give a value for the cam tooth position ?
Alex DTA
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Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
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Re: Crank sensor offset - getting it right

Post by Alex DTA »

SMR wrote:Well, no luck re-producing the deadtime box issue, despite trying various routes/maps - sorry Alex!

Had a succesful trip to the dyno at Daytuner - despite poor atmospherics (92 degrees humidity, 23 degC air and low pressure) which gave low numbers, we made gains everywhere by leaning things off considerably, and tweaking the timing. Putting in the actual measured injector deadtimes did ov course richen everything up substantially, but the map was aready rich.

I had a couple of oil leaks round the cam cover so engine out job, but it gave me the opportunity to make a new cam trigger wheel; machining down the previous "negative" tooth wheel so it has one single "positive" tooth. This appears at 10 teeth (i.e 100degrees BTDC) according to the crank scope. The "cam pulse received" counts up nicely, the tooth counts shows as 10 but no cam angle number is shown.

Now the weird part - sequential injection works - rev it past the 2000rpm and all is well - it keeps running.
BUT, it won't accept "Coil per plug" - On previous trials, I had always tried both coil-on-plug and sequential injection at the same time, which always made the engine stall once rev'd above the 2000rpm change-over point.
This time I tried only the sequential which worked, and then only the "Coil per plug" which failed to work.

So perhaps my single inverse tooth trigger would have worked, and something else is amiss with the spark side of things?
All injectors and coils are wired up in firing order for the ECU outputs and the correct cylinders, so don't know what's up!
Do you get a big backfire when using coil on plug?

When you get a chance, post a crank scope with the spark plugs removed from cylinders 2, 3 and 4.
SMR
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Re: Crank sensor offset - getting it right

Post by SMR »

StevieT, yep, it showed the cam tooth position on the diagnostics page with both the tooth and the gap trigger, but I had not tried onlyt sequential before so it probably would have worked. Something else amiss I think!

Hi Alex,
It backfired massively when I restarted it after the coil on plug ticked casued it to stall above 2000rpm.

With the engine back in the car again, I can't access the coils/plugs to remove, so can't grab a scope trace for you.
Alex DTA
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Re: Crank sensor offset - getting it right

Post by Alex DTA »

Good new is the cam sensor is working, as it runs with sequential injection.
The cam angle isn't critical for injection, as injection can happen in any part of the engine cycle. The injection points will just be wrong, or show strange values when tuned.
It's more important for the coils to fire on the correct cycle.

It sounds like the cam angle is wrong, causing the coils to fire on the wrong half of the engine cycle.
Tooth 10 isn't 100 degrees BTDC, it's just the 10th tooth after the gap.

Turn on Sequential Injection, turn off Coil per Plug. Open the Diagnostic Display/
Start the engine, and rev past 2000, so the Sequential Injection is activated, and the cam tooth and angle are shown.
The angle calculate by the ECU may be incorrect, as it cannot determine which cycle the engine is on. It simply picks one of the angles to display.
Write down the angle, and enter that in the Cam Sensor Angle. Check the engine runs still, then turn on coil per plug.
If the engine backfires and dies, add (or subtract) 360 to the angle above, and enter that.

The engine will now run.
SMR
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Re: Crank sensor offset - getting it right

Post by SMR »

Alex,
Many thanks for the detailed response - that all makes seense now! I'll give it a go and report back.
SMR
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Re: Crank sensor offset - getting it right

Post by SMR »

Sorted! Many thanks Alex and others for the pointers.

To start with, cam teeth and angle displayed was 7 and -10.5. Once rev'd above the 2k rpm, this appeared to waver between tooth 7 / angle -10.5 and tooth 10 / angle 17.5
Entering 17 didn't work, but -243 gives sequential fuel and coil per plug! All good.
Once I had put in the -243, the diagnostics showed a much more steady and stable 243 / 242 and 10 teeth.

I had a quick fiddle with the injector closing point and -180 closing point appears to give the richest idle. Not conclusive, and in order to fill in the 20x14 table will need another trip to the dyno but all's good!

Cheers!
SMR
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Re: Crank sensor offset - getting it right & adding squentia

Post by SMR »

Hi All,

As said on another thread, I had an excellent test session this morning at Boyndie drome Kart track - dry, cold, windy but the sun was shining and I was driving the car for the first time since Loton last September - 11 months ago!

Getting back to the sequential/COP settings and getting it working better; Well, I trawled the 'net on anything I could find regarding injection timing and it's relation to engine speed and load.
With this very sketchily-gathered info, along with playing with light loads/revs in the garage and monitoring lambda I've compiled a 14x20 injection angle map;
injection angle map.png
On track, it worked great - and doing a back-to-back run with the old batch/wasted-fire setup I couldn't feel any discernable difference. From what I've read, it's likely to only make much difference at low loads/low revs but more to do with economy/efficiency than any power gains.... My injectors are maxing out at only 60% duty so the theory says that I may see an improvement, but doing the maths, by around 5500rpm it shouldn't matter any more.

The proof is in the pudding, and only another trip to the dyno will tell for sure, but its certainly seems to be running very well.


Something else I fiddled with was the "Engine start fuelling" map as I usually had to hold the throtle open for a couple of minutes once started, before it would idle on it's own. I reduced the numbers massively (based on trawling the start maps of all the other DTA maps I could lay my hands on) - and this morning on first start from 10 degrees cold it ran all the way up to temp from start without touching the throttle and without faltering/stuttering so a real win! For info, here's the map I ended up with;
start map.png
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