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umop apisdn
 
Join Date: Jun 2014
Location: Brisbane, Australia
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Quote:
Originally Posted by flightlead404 View Post
Can I drive the Porsche tach directly from the tach output on the MS?
the microsquirt has the tach drive circuit built in and matches the one in the megasquirt tach wiring thread

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1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

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Old 12-11-2016, 03:18 PM
  Pelican Parts Technical Article Directory    Reply With Quote #681 (permalink)
umop apisdn
 
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relevant thread for tachometer compatibility over years

Tachometer Compatibility Chart

and

HELP! tach died and I need to know what can replace it!
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Steve
1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

www.FrankenCIS.com
Old 12-11-2016, 03:37 PM
  Pelican Parts Technical Article Directory    Reply With Quote #682 (permalink)
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Quote:
Originally Posted by Reanimotion View Post
the microsquirt has the tach drive circuit built in and matches the one in the megasquirt tach wiring thread

Yes saw several similar diagrams on megaquirt fora. So it sounds like tachometer out WILL drive the Porsche tach directly.

Before I do that I'll just snip the wire at the CDI to disable the tach and see if RPM on the MS comes alive.
Old 12-11-2016, 09:59 PM
  Pelican Parts Technical Article Directory    Reply With Quote #683 (permalink)
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I'm going to have a play at building an oscilloscope out of a raspberry pi I have laying around. If anyone in the Atlanta area has a scope and would be willing to lend a hand let me know.
Old 12-11-2016, 10:03 PM
  Pelican Parts Technical Article Directory    Reply With Quote #684 (permalink)
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RPM Input Frustration

I've reach a state of high frustration trying to get reliable, indeed any,
RPM pickup.

As a reminder, I'm attempting to pick up from the TD output of the 6-pin Bosch CDI unit
(stock).

Car was running beautifully before I began this effort, there's nothing whatsoever wrong with the ignition. If I swap the stock WUR back in it fires straight up and has good idle speed, timing, and idle AFR.

I've tried every combination of OPTO, VR1, and even VR2 with either + or - to the TD output and the other side either floating or grounded......nothing.

Occasionally I've got weird, unreliable, and unrepeatable results, but nothing I can use. The stock tach remains connected and functions correctly throughout.

Anyone got any ideas?

Try some sort of circuit off the coil negative to tame the voltages? Maybe sort of inductive pickup with a 1N25 opto isolator and a pullup resisitor to +12? **** anything!
Old 12-18-2016, 06:11 PM
  Pelican Parts Technical Article Directory    Reply With Quote #685 (permalink)
umop apisdn
 
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email a copy of your current tune file to tech@reanimotion.com, just in case there is something odd in the setup

it might also be worth trying a parallel connection of VR1+ and VR1- to the green wire before the CDI instead of tapping off the TD output, basically driving both the CDI box and the MicroSquirt directly from the distributor output.
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Steve
1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

www.FrankenCIS.com
Old 12-18-2016, 06:24 PM
  Pelican Parts Technical Article Directory    Reply With Quote #686 (permalink)
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I don't know too much about this stuff - except I have had issues trying to drive too much electronics off the TD circuit. I contacted a guy that makes a tach adapt unit - for using a 4cyl tach in a 6 cyl engine etc. Basically his unit takes the 'relatively weak' TD tach signal and converts it to a more solid signal and I think a slightly different shape - but basically more robust. It is possible there is nothing wrong with what you have been doing, except the stock TD signal is not enough to drive what you are trying to utilise. In which case inserting a Tach Adapt into the TD loop may be a solution.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 12-18-2016, 07:21 PM
  Pelican Parts Technical Article Directory    Reply With Quote #687 (permalink)
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Thanks guys. A good nights sleep has given me a few ideas. I exchanged a couple of emails with Mike @ Dkubus who confirms that OPTOIN+ to the TD and OPTOIN- to ground is the right recipe.

I was thinking about grounding and how often that is the cause of all sorts of vehicle electronic weirdness, then I remembered that since I've been using an independent battery for testing, I don't remember seeing the ground strap I've been using to connect the vehicle to the extra battery! I may have knocked it off, which would leave the MS power and ground completely isolated from the vehicle and with nothing to reference the TD output to. That's my first next step.

Second, Alan, I get what you're saying. If grounding isn't the issue I just purchased an oscilloscope (Rigol 1054Z which I hacked with some upgrade codes, nice unit for $399). I'll make sure I understand what the TD output really looks like on a running car, then maybe I can make some circuit up with a 1N25 optoisolator and a pullup to +12v to get a clean 12v signal with minimal loss.

Steve, in his email Mike mentioned using "Basic Trigger" instead of "Fuel Only" in the ignition settings, but I didn't catch that till this am. I've been using "Fuel Only", is that right?
Old 12-19-2016, 06:06 AM
  Pelican Parts Technical Article Directory    Reply With Quote #688 (permalink)
umop apisdn
 
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should be "Basic Trigger"
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Steve
1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

www.FrankenCIS.com
Old 12-19-2016, 06:08 AM
  Pelican Parts Technical Article Directory    Reply With Quote #689 (permalink)
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Flightlead404,
Purchasing an oscilloscope was a brilliant move. It's the best diagnostic tool to have in determining wave shapes, noise, reference voltages and so on.
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Old 12-19-2016, 06:37 AM
  Pelican Parts Technical Article Directory    Reply With Quote #690 (permalink)
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If you find the tach signal is not adequate it would be worth doing a search on the 911 forum for Tach Adapt. There are a few threads. The guy Bob (Pelican member) who makes them is very helpful and can explain. Only costs $100+ from memory. May save you some trouble.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 12-19-2016, 09:23 AM
  Pelican Parts Technical Article Directory    Reply With Quote #691 (permalink)
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Still no RPM, but a little more data

I ran dedicated power from the switched buss on the front fuse panel and a dedicated ground from the battery negative. Power goes to a fuse block in the rear with separate fuses for the MS and each of the injectors. Ground goes to the engine block and the MS grounds and OPTOIN- are grounded at the same location. No RPM on the MS when OPTOIN+ connected to the CDI TD pin with or without the tach connected.

So, broke out the new scope and this is what I found.


Several points to note.

1) The signal from TD is VERY noisy
2) Eyeballing out the noise, the base voltage is not zero, it is about 1.5v+ ref where the MS is grounded
3) Top of the signal is around +7.2v ref where the MS is grounded
4) This was idling at around 1,400 rpm and shows approx 70 Hz. 1,400 rpm is 23.333 r/sec. Plugs fire every alternate revolution, so for a 6 banger that's 3 sparks per rev, roughly 70 ignition events a second at this speed, so the math seems to work out (or am I totally nuts?)

I have the Ignition Input Capture set to Rising Edge (other settings on either Basic Trigger or Fuel Only made no difference so I left at Basic Trigger and Rising Edge).

Why isn't the MS detecting the rising edge? I have logs, there's not even a blip of rpm. Solid zero.

There's only two things I can think of, either the signal is too noisy, or the non-zero base voltage is throwing things off. The solution to both of those is to build a Schmitt Trigger to clean this up to a 0-5v square wave using TPS VREF.

Anyone got any insights?

Last edited by flightlead404; 12-28-2016 at 08:00 PM..
Old 12-28-2016, 07:54 PM
  Pelican Parts Technical Article Directory    Reply With Quote #692 (permalink)
 
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The Tach Adapt does something similar - don't remember exactly what - but a quick search should pull the info up. may be simpler than going round the loop yourself?Tachometer Adapter

Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)

Last edited by Alan L; 12-28-2016 at 08:32 PM..
Old 12-28-2016, 08:28 PM
  Pelican Parts Technical Article Directory    Reply With Quote #693 (permalink)
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Quote:
Originally Posted by Alan L View Post
The Tach Adapt does something similar - don't remember exactly what - but a quick search should pull the info up. may be simpler than going round the loop yourself?Tachometer Adapter

Regards
Alan
Possibly, but I want to understand the problem, not just buy more stuff and have it still not work.
Old 12-28-2016, 08:49 PM
  Pelican Parts Technical Article Directory    Reply With Quote #694 (permalink)
umop apisdn
 
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non-zero voltage will be the issue as the Opto chip turns on at 1.1 volt
basically it would turn on and stay on and therefore never pulse

the floating single wire VR- option should trigger at 2.5v
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1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

www.FrankenCIS.com
Old 12-28-2016, 09:15 PM
  Pelican Parts Technical Article Directory    Reply With Quote #695 (permalink)
umop apisdn
 
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just reviewing the wiring description

OptoIN – (ground) should be at the CDI box in case there is a ground potential difference between the Porsche wiring and the MicroSquirt

if there is any resistance in the ground at the CDI it might be enough to increase the floor voltage over the ground seen by the newer microsquirt harness setup
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Steve
1981 928S 4.7 ROW with KE3-Jetronic and Franken8 (AEM Inifinty) follow at [http://www.frankencis.com/Activity-Feed/userid/2]
Yes! mechanical/hydraulic constant flow injection can be managed by a modern EMS

www.FrankenCIS.com
Old 12-29-2016, 12:16 AM
  Pelican Parts Technical Article Directory    Reply With Quote #696 (permalink)
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Quote:
Originally Posted by Reanimotion View Post
non-zero voltage will be the issue as the Opto chip turns on at 1.1 volt
basically it would turn on and stay on and therefore never pulse

the floating single wire VR- option should trigger at 2.5v
ok. I did clean up all the grounds, but since the CDI doesn't ground at the block there could be some potential difference. I can easily jumper a ground strap between the two for testing. I'm pretty sure I did that, but I'll do it again.

Regarding the voltage, I was reading about the opto input, which made me think that might be the issue. Instead of building a Schmitt Trigger, which is the proper solution, I may just try a quick and dirty solution. I'll put two 1N4001 or some other si-diodes in series between the TD and the OPTOIN+. That will give me a constant current drop of about 1.4v. Add to the 1.1v voltage needed to excite the LED side of the built-in optoisolator, should give me a turn on voltage of 2.5v. That is nicely above all the noise visible on the trace I attached above.

Last edited by flightlead404; 12-29-2016 at 07:11 AM..
Old 12-29-2016, 06:19 AM
  Pelican Parts Technical Article Directory    Reply With Quote #697 (permalink)
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You guys know your stuff - way over my head, but still fascinating.
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Old 12-29-2016, 06:20 AM
  Pelican Parts Technical Article Directory    Reply With Quote #698 (permalink)
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Big Progress

I seem to have RPM licked, but not how I anticipated. I put two 1N4007's in series and it dropped the voltage range by about 1.3 volts which dropped the base voltage below the turn on voltage for the optoisolator in the MS. It still didn't work. Fooled around with grounds and so on, no difference but, in all my playing and testing, I decided to go back and test all possible combinations again and VR1+ to TD and VR1- floating is now working reliably. IDK what happened before, it may have been while I was powering from the WUR connector which scrambled the MS and needed multiple reflashes.

Anyway, the recipe for RPM is VR1+ to TD, VR1- floating. This allows the factory tach to be driven from TD also.

I also appear to have a functioning AFR after some very grudging support from Alan at Spartan who sent me a used device that was DOA and wouldn't accept a return of a used device, and lied to me about when a replacement would ship. Not the best service, but it appears to be outputting correct voltages.

But, the AFR gauge on the TS dashboard is just showing ~128. Attempting to select "14point7" in the TS calibration seems to hang when writing to controller, all other calibrations write correctly. More playing needed there. Tuner Studio really is a crap program though, constantly hanging, resetting my computer, crashing etc.

Last edited by flightlead404; 12-29-2016 at 07:41 PM..
Old 12-29-2016, 07:01 PM
  Pelican Parts Technical Article Directory    Reply With Quote #699 (permalink)
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Anyway, the good stuff. Starts up warm relatively easily (didn't get a cold start as I'd run with the stock WUR in place while fooling with RPM).

But, it starts up with a very low lumpy idle with control pressure high off the scale and eWUR injector duty cycle solid at 90. Possibly some heat soak and needs to bleed off pressure? But the engine was not that hot, oil temp 60-70c.

Suddenly after a few seconds control pressure swings into the middle of the range and idle goes up to around 1,200. But its hunting badly and the hunting is in time with control pressure swinging and eWUR duty cycle swinging from peg to peg. See the video and log below. CP is lower left, CP duty cycle lower right. I provided video for the sound, I'm not touching anything when the idle suddenly changes.

Video
Logs
MSQ
Old 12-29-2016, 07:40 PM
  Pelican Parts Technical Article Directory    Reply With Quote #700 (permalink)
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