Using Oscilliscope to Set Duty Cycle

[tirwin]

Originally Posted by AndrewCologne

Yes, theWideband sensor way is also a very precise option, but If no analyzer is present then he still can easily set the duty cycle to approx. 60% on a warm engine at idle with lambda running, where this corresponds to a basic CO setting of 0.4-0.8%.


Exactly thats what he should try ... cause the approach above with a 60% duty cycle at idle makes the value of the cold start AFR higher.
In my case I even modified my WUR so that after 2.0 bar when starting it reaches the 3.6 bar quite fast which gives of me a perfect mixture at cold start with no jerky driving etc.
Also its possible to lower the cold start idle rpm with a "plug with hole" mod of the AAV where mine just starts with 1.100 rpm – the neighbors love it as no more "comments" regarding pollution and "noise" to the environment are addressed to me. Don't know how this is seen in the US but here in Germany many "cars are evil"-people changed to crazy ones.

Kudos to you on your ECU work. I always fancied the idea of a "drop in" replacement for the K-Jet box with some expanded functionality. I had thoughts of that combined with something like Jonny's CDI+ and a digital WUR.

Haha, yes. I recently upgraded my exhaust and doubt my neighbors are going to care for it too much. There are a couple of other car guys on my street so at least I'm not alone.

I think the move to electric cars is sort of setting people's expectations that cars can/should be quiet, which is why people who don't enjoy cars the way we do are completely perplexed by why some of us think louder is better.

Hearing the space shuttle launch in person was a highlight of my life!

[AndrewCologne]

Originally Posted by tirwin

I had thoughts of that combined with something like Jonny's CDI+ and a digital WUR.

CDI+ is worth every penny in my opinion.
But as the lambda based CIS already comes with a mixture regulating frequency valve, IMHO this makes a digi WUR for this specific environment redundant ... IF you can affect the mixture in a more wide range than the original ECU does. In the state of now the SC Digi ECU – I call it like that – can affect the mixture in the whole rpm range IF a rev reading routine is included and connected to the CDIs TD signal ... which I already tested and its funny when the new ECU detects a deacceleration etc. . The load can be read by an external pressure sensor connected to the manifold vacuum. The combination would give a mapping matrix where every state can be used individually for handling the mixture.

[mysocal911]

Originally Posted by AndrewCologne

CDI+ is worth every penny in my opinion.

Please fully explain.

[AndrewCologne]

Not fully but for me these points are convincing enough :

- https://www.youtube.com/watch?v=K65slwl__dk
- https://www.youtube.com/watch?v=jX0ZNijGjSs

and reports in this forum.

So if my CDI would need to be replaced I would kill several birds with one stone and get a CDI+.

Shure its possible to achieve an individual ignition timing curve with further electronic skills, but most of all the people do not know how and ... here they get a solution in an OEM looking case with newest technology.

And as all inspections etc. Im doing on my 911 by myself (as many of us do), someone could easely invest some of that saved money I into a device like that. In Germany the distributor is CarPoint.

[mysocal911]

Originally Posted by AndrewCologne

Not fully but for me these points are convincing enough :

- https://www.youtube.com/watch?v=K65slwl__dk

The Bosch CDI develops more than 1.5X the required spark energy over the necessary 911 RPM range.
The second spark developed provides little to no benefit, i.e. spark occurs too late with inadequate spark energy & duration.

Originally Posted by AndrewCologne

- https://www.youtube.com/watch?v=jX0ZNijGjSs

The spark timing issue is basically a function of the distributor signal used in both ignitions,
i.e. affects both CDIs, and has little performance effect. It's a non-issue!

Therefore, basically no real cost benefit over the original Bosch CDI.

[porschedude996]

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[Jonny H]

Originally Posted by mysocal911

The Bosch CDI develops more than 1.5X the required spark energy over the necessary 911 RPM range.
The second spark developed provides little to no benefit, i.e. spark occurs too late with inadequate spark energy & duration.



The spark timing issue is basically a function of the distributor signal used in both ignitions,
i.e. affects both CDIs, and has little performance effect. It's a non-issue!

Therefore, basically no real cost benefit over the original Bosch CDI.

It's been 8 years since CDI+ launched and I think you've trolled every single post about it. I still don't understand why but congratulations all the same!

[mysocal911]

Originally Posted by mysocal911

The Bosch CDI develops more than 1.5X the required spark energy over the necessary 911 RPM range.
The second spark developed provides little to no benefit, i.e. spark occurs too late with inadequate spark energy & duration.



The spark timing issue is basically a function of the distributor signal used in both ignitions,
i.e. affects both CDIs, and has little performance effect. It's a non-issue!

Therefore, basically no real cost benefit over the original Bosch CDI.

Read here with regard to multiple spark ignitions (CDI); The MSD Ignition - 'Exposed'
It refutes the view that a single CDI spark is better than present day COP inductive discharge ignitions.

[mysocal911]

Originally Posted by mysocal911

Read here with regard to multiple spark ignitions (CDI); The MSD Ignition - 'Exposed'
It refutes the view that a single CDI spark is better than present day COP inductive discharge ignitions.

Read here too; Twin Spark Firing using single CDI Box

[Damon88]

Originally Posted by Funracer

Great idea. Thanks

Just trying to confirm the right way to set this Oscilloscope up.

Is this correct..

1) engine at operating temp
2) Black goes to Green wire
3) Red goes to 15c ( does that mean I remove wire and ground 15c?) little confused on this one
4) rev engine to 1000 to 1500 rpm
5) set duty somewhere between 45% and 65%

Complete newb to this.. I have spent hours reading every post I can find on pelican and google, but just need confirmation of this process.

Cheers

[Damon88]

Originally Posted by AndrewCologne

Same with the oscilloscope – you see negative values in your oscilloscope output, so you connected it wrong.

To test a correct DMM/oscilloscope connection, just lead the wire of the 15c Switch (right chain housing) to ground and you should read a 65% duty cycle (and not 35%).

Just trying to confirm the right way to set this Oscilloscope up.

Is this correct..

1) engine at operating temp
2) Black goes to Green wire
3) Red goes to 15c ( does that mean I remove wire and ground 15c?) little confused on this one
4) rev engine to 1000 to 1500 rpm
5) set duty somewhere between 45% and 65%

Complete newb to this.. I have spent hours reading every post I can find on pelican and google, but just need confirmation of this process.

double post as I quoted the wrong reply..

[Funracer]

1 and 2 are correct.

3 is red to ground. I used one of the mounting studs for the distributor on top of the big fan,
but have recently started using one of the wings on the rear fuse panel covering wing nuts. Works great and much closer to the green wire easier to get to.

4 sounds right bc you do want the O2 sensor doing its thing. That requires the sensor be hot so above 1000 works well.

5 I always read you are shooting for 45ish with stock CIS or 41ish (a bit richer) if you are using SSI exhaust. I have SSIs and mine set at about 42.

Experts please correct me

[Damon88]

Originally Posted by Funracer

1 and 2 are correct.

3 is red to ground. I used one of the mounting studs for the distributor on top of the big fan,
but have recently started using one of the wings on the rear fuse panel covering wing nuts. Works great and much closer to the green wire easier to get to.

4 sounds right bc you do want the O2 sensor doing its thing. That requires the sensor be hot so above 1000 works well.

5 I always read you are shooting for 45ish with stock CIS or 41ish (a bit richer) if you are using SSI exhaust. I have SSIs and mine set at about 42.

Experts please correct me

thank you for responding and clarifying. I was confused about the 15c in previous posts. I couldn't seem to get the duty cycle lower than 51%. but I was also trying to set this at idle. after setting this yesterday. my car seems to run better, but now on cold start is seems to idle low and rough until warm... I will continue to learn..hah

[AndrewCologne]

Set the duty cycle at idling to approx. 55%, that correspondents to approx. 0,6% CO at idle at 50% duty cycle.

As your system does regulate the mixture via sensor input and duty cycling, a leaner mixture will be avoided anyway, no matter if you set the duty cycle at idling to 42, 55 or even 65%, cause the resulting duty cycle will keep the output after combustion at lambda 1.

The only advantage of a "lower" duty cycle than 55% at idling is that when the duty cycle switches to acceleration state (65%) it will actually result in a higher AFR/lower Lambda as if it would be set to 55% at idling.

[yelcab1]

Why 60% instead of 50%?

[joe912/62]

I seem to be having trouble to the frequency valve. I'm getting power to it but it's not buzzing or vibrating. I assume good valve is important? I'm getting a Ohm reading of 3.9 which I think is too high.

[yelcab1]

The frequency valve is the one that sets the duty cycle.

[joe912/62]

What happens if I run without the frequency valve connected?

[AndrewCologne]

The pressure uf the lower chambers in the fuel distributor will rise wich makes the mixture lean out. Trying to compensate that by simply re adjusting the CO screw will help here, but you will no longer have the needed enrichment at cold start and no enrichment at full acceleration.

[Damon88]

Thank you Funracer and Andrew for all your help. Duty Cycle set. Now it's time to go drive the car and have some fun. love learning more about these cars. Cheers to all !