Can't get an easy cold start #2

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Re: Can't get an easy cold start #2

Postby billjam » Tue Sep 12, 2017 3:54 pm

I will have a play with R52 and R56 on the weekend.

The flywheel is light, but still a standard Porsche item, so not so light that it would be a problem.
Yes, the starter really struggles. Everything in the starter circuit has been either replaced or bypassed at various times with no improvement. I have recently bought a 2kw HiTorque starter in the hope that a bit more grunt might help. I haven't fitted it yet because my gut feeling is that there is an underlying ignition problem and I am nervous about stripping the ring gear with the more powerful starter when the engine kicks back.

I think the missing teeth are around 87* BTDC. That is an ignition setting in the MSQ I think.
Sorry, I thought I posted the MSQ in the first post, but must have forgot. Anyhow, I will attach it here along with the last MSL file I ran.
Attachments
2017-09-03_start+run.msl
(369.77 KiB) Downloaded 9 times
CurrentTune 3-9-17.msq
(195.51 KiB) Downloaded 8 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billr » Tue Sep 12, 2017 9:30 pm

Bear with my rambling. Again, it is getting late for me; that's my excuse and I'm sticking to it!

I'm focused on the "cranking with compression" tooth-logs. DaveEFI, you said recently that looked OK, once you could get it to open. Do you not see that the wheel has become about 40-tooth in that log? I would like to see a similar "with compression" log taken by disabling the ignition, as well as fuel. If that looks better, then repeat with each set of coils on alone.

Speaking of DaveEFI... I'm looking for an expert opinion/advice: With the two FET gates for T & B coils wired directly together, is there any chance one FET turns on slightly before the other, thus charging the coil a bit, then turns off momentarily and fires the coil prematurely as the other coil's FET starts to turn on? I'm wondering if a resistor in series with each of those FET gates would help any?

Back to the OP. Compression is 11:1, but what cranking psi does that result in? That 87* tooth #1 angle may be what it takes, but I think recommended is 50* for a 6-cylinder. With the crank wheel "in the flywheel" and the sensor probably in the bell-housing/block I can appreciate that it isn't practical to change that angle, though. I gotta ask... you have checked spark timing (many times, no doubt) with a simple timing light; not one of those dial-back wonders?
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Re: Can't get an easy cold start #2

Postby DaveEFI » Wed Sep 13, 2017 1:26 am

billr wrote:Bear with my rambling. Again, it is getting late for me; that's my excuse and I'm sticking to it!

I'm focused on the "cranking with compression" tooth-logs. DaveEFI, you said recently that looked OK, once you could get it to open.



Sorry - I meant they now open OK with MLV. They don't look good. If you check the manual you'll see what a good one looks like.

IMHO you want to get that sorted first - before considering anything else.
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Re: Can't get an easy cold start #2

Postby billjam » Wed Sep 13, 2017 6:04 am

Bill, your rambling is excused. Time is something I am always short of, and time zones are something that make a process like this drag on for weeks when we are operating 12 hours out of sync.
You are correct about the sensor location. It is mounted on the back of the engine and is definitely not easy to move, so we'll have to live with it as is. Besides, there are plenty of Porsches running MS3 successfully with the same sensor location, so I am sure the problem lies elsewhere.
I have checked the spark timing with a timing light. I have a short lead that I use between #1 coil and the plug onto which I can clip the timing light sensor. Last time I checked, it was spot on.

I will fiddle with R56 on the weekend and run some of the other checks as well.
Fingers crossed.
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billjam » Thu Sep 14, 2017 5:58 am

Couldn't wait til the weekend so I had a play with R56 tonight hopeful that it might end this saga.
Unfortunately, it hasn't made any difference.
First, I turned it one turn CW, then two, three, five, seven and finally nine (just to beat Dave's record of eight!).
There is a log attached which is the final run at nine turns CW. Keep in mind that is from an unknown starting point, so I might have already been close to or at full CW.
The log looks exactly the same as one I ran previously (2017-09-09_12.31.37 compr.csv).
Attachments
2017-09-14_19.02.03.R56+9.csv
(18.95 KiB) Downloaded 7 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby DaveEFI » Thu Sep 14, 2017 8:41 am

I was assuming you were starting from fully CCW. But turning R56 from one end to the other usually results here in loosing the tach signal completely at some point.

Those pots have a slipping clutch. So if you reach the end you can turn and turn with no difference.
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Re: Can't get an easy cold start #2

Postby billjam » Fri Sep 15, 2017 7:40 am

Looks like another dead end.
If I have reached the max number of turns CW for R56, should I go back to fully CCW and start again? Is there likely to be a position further back in the range that might be better?
Should I look at adjusting R52 as well?

Keep in mind that whatever is going wrong here is only during the starting cycle. Once the engine is running, everything is 100% normal.
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Re: Can't get an easy cold start #2

Postby billr » Fri Sep 15, 2017 11:21 am

Did you ever try running on one set of coils at a time, totally disconnecting the input to one set?

You have VR, correct? I would put both pots full CCW and leave them there, unless you have a scope to prove something else works better.

Speaking of a scope, with all the problems you have had with this beast a scope (cheap or otherwise) seems like a good investment.

Is the mainboard a V3.0? Any chance the pots are located or oriented incorrectly?
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Re: Can't get an easy cold start #2

Postby billjam » Fri Sep 15, 2017 6:39 pm

Bill
Yes, I tried running just one set of coils. Starting was just as difficult with the one set of coils. I did manage to get it started and even drove it around for a bit, but it didn't make any difference to performance or the tooth log.

The sensor is VR. It is the standard Bosch part for this car.
I had a thought last night about the sensor ... I have previously set and checked it's tooth clearance. I might do that again and also check that it isn't dirty.

I bought an oscilloscope a couple of years ago when this issue first raised its head. Unfortunately, I couldn't figure out how to use it.
The main board is 3.0. I bought it assembled from DIY Autotune, so it should be OK.

I will set the pots back to fully CCW and see if that has an effect.
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Re: Can't get an easy cold start #2

Postby billr » Fri Sep 15, 2017 8:18 pm

Alas, when I mentioned the scope I forgot that your crank wheel is the flywheel. Mounting a normal wheel on a spindle with a small electric motor is usually fairly easy, and allows you to play with the scope endlessly and at any speed desired. However, using a scope on the actual engine shouldn't be impossible. At least you have a CMP sensor to making syncing the scope easy. Do you want to pursue learning about how to use the scope? It will probably take a lot of Q & A but I expect we can talk you through it.
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Re: Can't get an easy cold start #2

Postby billjam » Fri Sep 15, 2017 9:23 pm

Thanks for the offer of oscilloscope tuition! It nearly did my head in last time I attempted it. :shock:
I'll hold off on that for now.
If I recall correctly, one of the main problems was figuring out how (where) to connect it and then how to set it up. It looks like the picture attached. Way too many buttons for my liking.
Oscilloscope1a.jpg
Oscilloscope1a.jpg (67.52 KiB) Viewed 222 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby billr » Sat Sep 16, 2017 8:31 am

Okay, your choice about if/when to learn how to use the scope. It being dual-channel will make it even easier to use.
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Re: Can't get an easy cold start #2

Postby Dennis930 » Sat Sep 16, 2017 8:52 am

Bill,

How difficult is it to access the VR sensor? Do you need to partially drop the motor to get access? Maybe the gap needs closed up a little to adjust for the engine speed drop when cranking. You mentioned a high torque starter, do you plan to install it?

As for the o-scope, you could connect it to battery charger and see if you can get to display the voltage. The voltage usually has some ripple on it. I use a cheap USB scope with my laptop which works OK for this type of troubleshooting.
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Re: Can't get an easy cold start #2

Postby billjam » Sat Sep 16, 2017 7:26 pm

It is Sunday morning here, so after I have mowed the lawns, I allowed to play with "that car" again! :roll:
The VR sensor is fairly easy to get at with the car jacked up and the left rear wheel removed, so I pulled it yesterday to check if it had picked up any dirt or metal shavings from the ring gear and pinion. It had a few small bits of metal stuck to it, so I got all excited about that. Cleaned it up and tried a start, but same result. :cry:
I never thought about closing the gap. That is only a few minutes work, so I will give that a try first. Standard gap is 1mm so I will close it up to 0.5mm and see what happens.

I have held off installing the larger (2kw) starter as I am nervous about stripping the ring gear with the brutal kick backs I'm getting, but I am at the stage where I at least need to try this.

Failing a resolution today, it looks like oscilloscope lessons might be in my future.
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Re: Can't get an easy cold start #2

Postby billr » Sat Sep 16, 2017 8:08 pm

Have you thrown a new CKP sensor at it lately? Parts-swapping isn't the most elegant way to trouble-shoot things, but it may be the practical approach in this case. I wouldn't put the new starter on the sacrificial altar until you can get a good-looking CKP tooth log while cranking. If anything, try pulling the cranking advance back to -5 (5 ATDC).
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Re: Can't get an easy cold start #2

Postby billjam » Sat Sep 16, 2017 9:38 pm

When I took the sensor out yesterday, it had a few metal filings on it, so I cleaned it and put it back, and as I mentioned in my earlier post today, it didn't make any difference to starting. It tried to fire, then the spark became random.
I took it out again today to reset the gap a bit closer, it looked like this! ... worse than when I cleaned it yesterday after no more than ten seconds of cranking!
crank sensor dirty2a.jpg
crank sensor dirty2a.jpg (22.73 KiB) Viewed 177 times


Thinking aloud here, but I can imagine this stuff having an effect on the operation of the sensor at low speed, yet once revs are high enough, that fuzz would get blown away and the sensor would work just fine.
I can imagine that the slower the cranking speed (cold days), the worse the impact of the fuzz might be. Once the engine has run and is warmer, and all the fuzz has blown away from the sensor and flywheel teeth, starting is normal.
Unfortunately, there is no easy way to clean out the bell housing without dropping the engine and transmission. :cry:

Just an afterthought, if my theory is correct, closing the sensor gap would only make this worse. Conversely, opening the gap slightly may improve the situation.
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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 17, 2017 3:54 am

I tried a few things today, but didn't actually get anywhere.

I can confirm that the metal shavings and fuzz on the sensor are not the problem.
I managed to blow out the bellhousing and flywheel with compressed air. After a lot of adjusting, cranking and logging, the sensor was still clean. If the dirty sensor was the problem, I should have seen some change (improvement) in the logs.

Normal sensor gap is 1mm. I adjusted it to 0.6mm and the log was exactly the same, so we can assume no problem there.

To check what effect, if any, R56 was having, I adjusted it fully CCW, then CW in two-turn increments up to eight turns. I'll post the first three logs, after that they mostly look the same except for different spacing of the major and minor spikes
I also made a one turn CW adjustment of R52 to see if that had any effect. It didn't, maybe I should have tried a few more turns, but I don't know what this pot does and I haven't been able to find out from the manuals.

All the tooth logs show a main spike as well as a minor spike. The intervals vary as R56 is adjusted CW. I will upload the first three logs, the last ones look the same except that the spacing of the spikes varies as below.
To summarize ...
R56 = 0, main spike every 39, minor spike every 58
R56 = 2, main spike every 39, minor spike every 58
R56 = 4, main spike approx 32, minor spike approx 48
R56 = 6, main spike approx 29, minor spike approx 78
R56 = 8, main spike approx 35, minor spike approx 51
This doesn't make a lot of sense to me, however the first two logs with minor spikes at 58 seem relevant for a 60-2 wheel.
But what causes the main spikes? These seem to be main issue as they overpower the minor spikes at 58. Without them, the tooth logs at R56 = 0 and 2 would be fine. Yes?
Attachments
2017-09-17_13.56.09 R56+0.csv
Base log with R56 fully CCW
(10.02 KiB) Downloaded 6 times
2017-09-17_14.06.28 R56+2.csv
R56 +2 turns CW
(9.33 KiB) Downloaded 4 times
2017-09-17_14.11.57 R56+4.csv
R56 +4 turns CW
(14.84 KiB) Downloaded 5 times
MS3X on a Porsche 3.6L engine with Triumph Daytona ITBs, Toyota COPs (12) and sequential injection.
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Re: Can't get an easy cold start #2

Postby turbo conversion » Sun Sep 17, 2017 5:58 am

Is R52 at full CCW?

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Re: Can't get an easy cold start #2

Postby billjam » Sun Sep 17, 2017 6:33 am

turbo conversion wrote:Is R52 at full CCW?

David

Yes. I turned it one turn to see if there was any effect on the tooth log, but there was no change so I turned it back to full CCW.
Should I give it some more turns? What does it do?
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Re: Can't get an easy cold start #2

Postby whittlebeast » Sun Sep 17, 2017 6:52 am

Can we please do a reset?... What does the wheel on the crankshaft look like? Is there a cam wheel? and what does it look like?

We are talking about what do they look like in a photo?

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