2µF Suppressor, what type can it be or must be?

[Miguel Silva]

Yes, I see that now, to save the .rfc it has to save individual channels, and I saved both channels at the same time and the only options it gives is .txt, .xls, .doc or images. I didn't know it wouldn't reopen them on the software, I'l do it again the correct way.

 

I have a 20bar/300psi 1000hz transducer I'll wire it up to do the tests you propose.

[Steve]

https://www.picoauto.com/library/training/pressure-school-part-2-a-running-diagnosis

Obviously to make a waveform like this the transducer needs to be able to read vacuum also. But i suppose it would be able to read backpressure anyway if there is any.

If this doesnt work out for you there is always the option to just loosen the bolts in front of the cats to rule them out. 

[Miguel Silva]

Mine is a "Gage Pressure Transducer" not a "Absolute Pressure Transducer" but to test back pressure I think it's ok.

What kind of back pressure should be expected at 250/260 RPMs?

I also have a 4bar/60psi transducer if more low resolution is needed? But it will max out on compression.

[Steve]

You run the engine at idle. Unplug the injector and coil and run it on 5.

Use the big one. Backpressure should be as close to athmospheric as possible. Study the article above. 

That said. Sounds like its going to be easier to just split the exhaust to check this out of the game

[Miguel Silva]

On 11/18/2018 at 5:33 PM, Steve said:

You run the engine at idle. Unplug the injector and coil and run it on 5.

Use the big one. Backpressure should be as close to athmospheric as possible. Study the article above. 

That said. Sounds like its going to be easier to just split the exhaust to check this out of the game

 

Hi Steve,

So I've done the back pressure test and I get a max of 1.98psi/137mbar on both sides with a slight difference on the curve shape (images - "Back pressure test right bank Cyl 3 Chart" and "Back pressure test Left bank Cyl 2 chart") it doesn't look as severe as the 9psi/618mbar from the example you provided. (the hantek software is truly bad, practically useless for reviewing files)
Never the less I took the liberty to inspect the catalytic converters, and to my surprise the one on the left side had already went out of the exhaust completely, and the back pressure test it reported slightly longer duration of 1.98psi/137mbar for the exhaust stroke (image - "20181127_102711 Left"), the one on the right was cracked (image - "20181127_102140 right")and I removed it, so no cats for now it's just hollow tubes.

Tested it again and the same problem, at 1 Bar of boost it starts to misfire from +-5000 RPM to 6700 RPM and then it clears up to the RPM limit, at 1.1 Bar it starts to misfire from +-4600 RPM to the end but more frequently, at 1.2 Bar it starts to misfire from +-4600 RPM and it goes into over boost at 6800 RPM ("Log 2018-11-28 11;48;09 am") even with the LINK trying to manage it.

I've also done a test maxing out the dwell time for each RPM above 6000RPM (6.5 ms@60000 RPM, 5.4 ms@70000 RPM, 4.5 ms@80000 RPM) 40% duty cycle - 1.5 ms spark duration. Conclusion no difference!

I've also did a test advancing the ignition for 1.0 Bar region 3.5º, 1.1 Bar region 4.0º an 1.2 Bar region 3.0º as I knew this area had conservative timing and wold not knock. Conclusion no difference! (slight increase in power) (image - Ignition test difference in power).

I've also did a test with the same ignition advance as above and leaning the mixture from 0.77λ to 0.84λ. Conclusion no difference!

I've also done a compression test with the same transducer (so as to put all on the same slate) but used link software and the fuel pressure input at 100hz (you can use the link software an the fuel pressure input to look at the data). The values aren't the same as I've written before.
I've done Cyl 2 without oil (126 psi/8.7 Bar) and with oil (188 psi/13 Bar).

Compression test:
https://drive.google.com/open?id=11aiwFhxp8-ND_Tmy0QtCuArjS_XiUOqS

Back pressure test:
https://drive.google.com/open?id=1gWvHz00Aqd7EnKjE1sQ3Fpjrw-_Rit8q

Software Dyno tests:
https://drive.google.com/open?id=1ju8OJ6A8NdshonSgN5HQFN_YhEAo4fx6

 

[Steve]

You are right. those captures are horrible. Not sure if its the scope, software or the sensors samplerate thats the issue but its really not very usefull. May i suggest the pico 2204a as a minimum for your next scope should you ever get another one. The pico software is amazing and all their hardware is of good quality. Here is a small comparison between it and a bigger brother.

 https://www.youtube.com/watch?v=n7IGce393FA                                                                  

' You didn't by any chance try capturing backpressure at a higher RPM? Like 3000-3500rpm or something. Those broken cat internals might just be further down the system making a restriction there instead. If no cats or any restrictions are there then you shouldnt read any backpressure at all really. Other than your less than ideal triggersystem your comment about you starting to see this problem with another ECU AND that you had cats on your car made me sway towards a restriction in your exhaust. More so than a problem with the ecu or tune. Cats need certain conditions to work and im not sure your tune was up to keeping it alive. Or your lambda sensor was affected by ground offset and your AFR might not have been what you thought it was which in turn killed the cats eventually. Stuff like that.

I still think you should try disconnecting the cats and run an open exhaust eliminating a clogged exhaust. Just be careful as you would be changing the engines VE doing so. Maybe set up a limiter protecting against lean conditions to be safe.

 

[Miguel Silva]

15 hours ago, Steve said:

Not sure if its the scope, software or the sensors samplerate

I think the sensor sample rate isn't 1000 hz (as advertised, chinese material) but more 500 hz(the steps are 2 ms apart), and nothing compared to the 10000 hz 0.1 ms of the wps500x.
The device is not all that bad but the software is just terrible can't do custom probes no unit on the rulers doesn't read back files, just terrible.
The Hantek was free a friend as lent me.

One more thing about the signal on the back pressure test CH1, it's noisy lots of spikes, the power and ground all come from the ECU as I'm using the fuel pressure sensor wires, is this normal or ok.
The Hantek reading from a 2v square wave generator has a pretty clean signal, however the 2 channels read different voltages.
https://drive.google.com/open?id=1K4EwWv19b8PXJuX9zMh84pELwuddxZ3I

This link is just from CAM and the the transducer connected, ignition on, car not running. CH1(pressure transducer) has 345 mv peak to peak and CH2(CAM sync)  has 314 mv peak to peak, is this acceptable? for the transducer that's +25psi variance peak to peak, even subtracting the mean it gives a +10psi variance.
https://drive.google.com/open?id=12Ocbo5wu19HjXF-1OjwWiQ2bba1EyPbB

15 hours ago, Steve said:

May i suggest the pico 2204a

Yes, I'm ordering one soon, I played around with the software the pas days and there is no comparison.

 

15 hours ago, Steve said:

You didn't by any chance try capturing backpressure at a higher RPM?

No I didn't know if it could do any damage due to the imbalance, but can do it again, just free revving 4000 RPM? no load?

15 hours ago, Steve said:

shouldnt read any backpressure at all really

Even with turbos is it the same? Or can it increase just a little bit on low RPM?

 

15 hours ago, Steve said:

Those broken cat internals might just be further down the system

I don't think so, first taped along the pipes for tinkling sounds and nothing, not satisfied i removed them, inspected visually and banged them on the floor vertically and noting came out.
 

15 hours ago, Steve said:

turn killed the cats eventually. Stuff like that.

I have an idea of what killed the cats, experiment with 2 step and ignition retard on decel to make pop and bangs whenever lift of the throttle. :-) 8-)

15 hours ago, Steve said:

I still think you should try disconnecting the cats and run an open exhaust eliminating a clogged exhaust

I'll have it a go.

[Steve]

Yeah the pico software is awsome. One of my scopes is the 4425 and it is an eyeopener.

No you are good with elevated RPM`s. You probably would be good enough with a few snap throttles to get what you want.

To be honest i totaly forgot about the turbos. That said, i just went out to the garage and did a log on my ecu. It was a cold start with elevated RPM`s and i just did a few seconds worth. BUT my exhaust backpressure sensor read about 0.8 Kpa (at max during this short test) higher than the key on engine off reading. Which is roughly 0.1Psi.... For what its worth. Thats sensor reading from the ECU, not scope with pressuretransducer. Also i have a pretty open exhaust and not stock turbos, which probably makes it a little difference to yours.

Yeah pops and bangs arent that popular amongst cats of any kind 

Lets hear how it goes!

[Miguel Silva]

Hi Steve,

Finally got to test without the mid pies, same problem misfiring at higher boost (the noise is infernal).

Have the new logs with SNAP WOT and IDLE this time with a PICO.

https://drive.google.com/drive/folders/1Oae9_GA7fIYRQIhR_l-fWyz33DEFxxdo?usp=sharing

At 7000 RPMs the 500hz transducer con only give us +-8 samples per 720º cycle but I think its enough to see the trend.
Looking at this numbers (54psi max at exhaust stroke) testing in cylinder back pressure is probably not equivalent to testing just the exhaust back pressure, either that or these number are completely wrong.

This was tested on the nº 3 cylinder and I've also noticed a drift between the cylinder nº 3 timing mark and the pressure curve as RPMs go up, noticeable only from 1400 RPM to the top it's probably just the 10º from the VTC but the lack of frequency resolution of the transducer may be the culprit 7000 RPM - 84º resolution, 3500RPM - 42º resolution and 850 RPM - 10º resolution.

On 12/1/2018 at 3:30 PM, Steve said:

You probably would be good enough with a few snap throttles to get what you want.

Happy Christmas.

[Steve]

Haha, yes that transoducer isnt very helpfull if you want to see details or meassure degrees or anything lke that. That said. Here is a few shots from your 7200rpm open exhaust file.

 

Early in the log before reving it. The line represents 0 psi and you can clearly see the vacuumparts and the little rise on the exhauststroke (that may or may not be normal).

 

In the next picture i cant make anything out really. its at max rpm and either the sensor cant keep up with ANYTHING or there is actually positive pressure all the time Line is still at 0 psi

 

On this two last ones though where the rpms are coming down but not stil at idle (i changed the scale a bit to show it clearer). One line is still at 0 and the other is at max measured vacuum. (-5.6 ish psi).

On the bottom one i moved it to the max pressure in the exhaust stroke. and it shows over 8 psi

 

 

So obvious question now; do you still have the PRE-cats on the car??

Regarding timing it should ot affect it as the cas is on the exhaust and vtc on intake. Max pressure should still be on tdc.

I have personaly measures over 7 degrees fluctuation between cranktrigger and camtrigger on my car. Food for thought.

Yeah happy x-mas bud!

[Miguel Silva]

4 hours ago, Steve said:

So obvious question now; do you still have the PRE-cats on the car??

No I've got one of this.
https://www.z1motorsports.com/z1-products/z1-motorsports/z1-25-bolt-stainless-steel-downpipes-p-2958.html

4 hours ago, Steve said:

Regarding timing it should ot affect it as the cas is on the exhaust and vtc on intake. Max pressure should still be on tdc

Yes this was just stupid of me, writing without reasoning a bit! 

[Miguel Silva]

The transducer is a 0.5 - 4.5v (0-300psi) so all the negative pressure values should be taken with a grain of salt, the MAP sensor reads -13.1psi(-90kp) and the transducer bottoms at -5.6psi.

[Miguel Silva]

The sample from the PicoAuto SNAP WOT goes up to 37psi on the exhaust stroke at 4800 RPM.

[Steve]

Yeah... With those downpipes and an open after them there should be no restrictions to speak of anyways. So i guess we are ruling that out now.

So where does that leave us. In the logs i saw so far i dont think i actually saw the lambda go lean anywhere, which it should do if there really was a missfire (unburnt air passing thorugh the exhaust). Also all the logs showed a picture perfect RPM line which to me and what my experience with the CAS tells me there is heavy filtering involved. I would still love to see an unfiltered logfile that shows HOW bad/or little scatter there really is on your car. Thing is that no matter how much filtering is applied, the craziness is still going on physically between the CAS and the crank. I think im back at my original thought when i saw your post. Severe timing scatter.

[Miguel Silva]

16 hours ago, Steve said:

Severe timing scatter

The RPM needle bounce is perceptible with no filter

New logs no RPM filter (1)
https://drive.google.com/drive/folders/1vhJn_KUE4wvgWkxZwfjvVNPyYr5Da6ZB?usp=sharing

Log wise so 2 logs one at 1Bar and the other at 0.7Bar both with RPM filter of (1), the RPM scatter is more pronounced on the 1Bar.

As I didn't have any other way to convey the misfires or the power dips that I feell, so I decided to calibrate the G sensors on the thunder, and if you look at the logs and find the "longitudinal X acceleration" you can see that the 0.7Bar as a big acceleration rate till max boost 3300 RPM, levels until 5000 RPM, and +- progressive deceleration up to the 7000 RPM, and the 1Bar has a deep that starts at 5000 RPM goes all bouncy until 6700 RPM and it stabilizes after that to red line.

The R8 NGK coils I'm using have 4 wires, one of them is "unused" and I've tried two options with the same results (not grounded and grounded) one third option I used was to connect it to the oscilloscope and see if it generated a confirmation of firing/ignition signal and it doesn't carries any apparent signal. (so what is it for?)

[Steve]

There we go.

Granted the RPM line itself is smoother than what i suspected. Could be because of slow logging rate. What gives it away to me though is looking at the RPM ROC parameter. Thats RPM Rate Of Change. How much the RPM changes over a second. Anything over 0 meens RPM is rising at a certain rate and below 0 means its falling. We bot KNOW you are accelerating so the CRANK is certainly not slowing down, right? However you can see i both my screenshots that the ECU is logging a very erratic RPM ROC. It should ALWAYS be on the positive side when the engine is accelerating. That IS the CAS flapping around. There is also some knock registered in one of the logs. I bet because of unstable timing.

 

 

 

Never mind me saying it looked smoother than expected. I just wasnt looking close enough at it. Its actually one of the worst i have ever seen

 

You sir, are going to install a cranktrigger before it breaks down completely

[Miguel Silva]

I also use the ROC to make some calculation of power.

So where do we go from here?

 I have a AEM disk on a CAS all assembled, is this an option?

[Steve]

It helps with the erratic signals. It really just masks the problem and steady the moving around on your ignitiontable. The only thing that really fixes it is a true crankfitted trigger. Like the one from Ross performance

[Stevieturbo]

On the topic of running compression tests...and sensors etc.

 

Any thoughts on this gear? It's a lot cheaper than Pico, the gear/software is Ukranian based. Their pressure transducer is a fraction of the price of Pico's, although no idea what resolution either offer.

The software shown here looks pretty cool ( I've never used a Pico though so maybe it can do similar ? )

I've used a cheapish Honeywell sensor for a few tests logging on my own car, it claims less than 2ms response, so around 500Hz i guess and logging at 1000Hz it seems pretty decent. Could only find a 500psi absolute sensor though, which wasnt ideal.

 

 

[Steve]

Wow. I have never seen that software before. Looks pretty cool.

The pico software wont do all that automatically. It wont lay it all out in plain "text" for you, rather you will gonna have to interpret the data you collect yourself. So i guess you will have to understand "yourself" what is or should be going on. There are softwares/scripts/addons (or whatever you want to call it) available that helps the process though

Yep its pretty pricey the WPS. I would love to have one or two more but at the pricepoint its at its pretty far down the priority list.

[Stevieturbo]

What sort of resolution does the Pico sensor offer ? A lot of pressure sensors I see claim 1ms, ie 1000Hz...so realistically...will the Pico be any better than that ?

The Autoscope one sells for around 105 Euro or so although they're bloody awkward to buy from taking Western Union. If it wasnt for that, I'd have bought a kit already.

http://autoscope.eu/products/

They list it too as a -14.7 to 500psi sensor, so probably not ideal for petrol engines. I bought a cheap compression tester and added this sensor to it, and it seems ok at cranking and idle. Doubt it'd work that well at high rpm though.

https://uk.rs-online.com/web/p/pressure-sensors/1115919/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E2828282872737C5253295B205D3F293F285C647B337D5B5C2D5C735D3F5C647B332C347D5B705061415D3F29297C283235285C647B387D7C5C647B317D5C2D5C647B377D2929292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3131312D35393139267374613D3131313539313926&searchHistory={"enabled"%3Atrue}

 

 

Really...it would be nice if the aftermarket ecu makers, could start to integrate some of these diagnostic modes into their ecu's, seeing as they already receive a lot of good information. Relative compression tests would be a doddle, crank/cam ( and other sensor ) scope traces etc

[Miguel Silva]

23 hours ago, Steve said:

Its actually one of the worst i have ever seen

So it isn't misfiring! it's fluctuating ignition timing allot giving the sense of misfire?

Part of the AEM trigger wheel can be used for the "Cam Pulse 1x" sync signal correct?!

[Steve]

Yes Miguel, thats my take on it all.

You can use the single "cam tooth" on the disk as camsynk yes. Thats what im doing myself.

Stevie, seems the WPS500 got a responsetime of 100 usec. So quite a step up from 1ms. https://www.picoauto.com/download/documents/datasheets/MM073.en_WPS500X.pdf

Yeah Western Union really does not sit well with me.

To be honest im no so sure high RPM tests are very usefull anyway. Exept of course on a LIVE cylinder. But thats another topic.

Would be awsome if the ECU manufacturers implemented that sort of thing, However they would need to drasticly up their samplerate for it to shine. A bit of sidetrack. Plex-tunings bigger dash can read and log in cylinder pressure transducers. Which is absolutely awsome!. No experience with it myself though. Just drool over it from time to time...

EDIT: Miguel, to expand a little bit. When my own car was at its worst, and i decided there was no way around a cranktrigger, i could also feel it in the car. It was like power- less power - power - less power - power. I didnt loose "all" power, but from the looks of your logs, neither do you. I could actually also see it on my tachoneedle jumping around a little (there is a limit to how fast it can react though).

[Ivaylo Angelov]

Just wanted to clear the VAG coil wiring diagram. These coils have two ground connections when in the OEM installation . One is for the secondary coil - wired to the cyl head. The second is for the coil driver - wired to the chassis/ecu ground.

[Steve]

Just googled this topic to find some pictures to compare before and after and found a post with some pictures made by... well myself

https://www.hpacademy.com/forum/webinar-questions/show/095-choosing-a-trigger-method