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Sorting out a Citrus

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My Citrus tends to stumble and lack power in lean burn when it is under increasing load. When it exits lean burn, there is a gentle burst of acceleration. I hope to uncover why. Items I'll be looking at:
  • EGR valve
  • EGR plate
  • EGR passages
  • Spark plug indexing
  • Spark plug age
  • Spark coil performance
  • LAF sensor
  • Manifold pressure
  • Fuel injectors
  • Fuel pressure
  • Engine deposits
  • Valve lash
  • Valve leakage
  • Valve guides
  • Exhaust system
  • Compression/worn rings
  • ECM control loop issues
Have I missed anything?

I won't look at all of these areas if I find the root cause before I get to them all!!!

I have already looked at several of these areas, but have decided that I need better data. OBD2 is too slow, so I plan to measure a number of sensors in real time, with many samples per cycle of whatever I'm measuring. This includes
  • Manifold air pressure
  • IAC valve position
  • EGR valve position
  • LAF sensor (A/F ratio)
  • Injector pulse width
  • Timing advance
  • Crank sensor
  • Throttle position
  • Camshaft sensor
  • Some OBD2 parameters I can't measure, such as fuel trims
Arriving are some new tools such as an in-car fuel injector cleaner and parts to build the "black box" that will read the values above. I hope to be able to do A/B tests in many cases, such as with different EGR valves, different LAF sensors, and more.

Any ideas for measurements are welcome. This will probably start in earnest between Christmas and New Years.
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Mine does the same thing. LB with any load is really bad. It wasn't the EGR system, TPS, plugs, coils, valve lash, compression, LAF sensor, or ECM. I'm trying cleaned injectors next.
 

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Discussion Starter · #4 ·
First part of this project is to set up a high speed data logger for key engine parameters.

Wish you could buy this from, say, Adafruit: "ECM/MCM Breakout Board. For DIY high rate data logging or full electric conversions."
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@Gasoline Fumes, then hopefully this exercise will help both of us. What specifically happens under load in lean burn?
Bucking or "herky-jerky," as it's been called here in the past. I'll be cruising at maybe 45-50 MPH at 125 MPG, come to a slight hill, give it a little gas to maintain speed, and it'll drop to about 75 MPG and start bucking. Sometimes really badly. Giving it more gas will drop it down to about 50 MPG and it'll run smooth again and begin accelerating. I can't maintain LB on level ground at highway speeds either.

Julian Edgar once wrote that with his aftermarket engine management, he got bucking with too much EGR flow or going too lean. I cleaned the EGR, and even tried completely blocking it with no improvement. So it must be running a bit too lean in LB. I should probably check the fuel pressure, but I haven't yet. I bought an injector cleaner for about the same cost as having all 15 of my Insight injectors cleaned/tested professionally. Haven't done that yet either. Kinda waiting for my new injector seals to arrive. And being lazy!
 

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Discussion Starter · #7 ·
Bucking or "herky-jerky," as it's been called here in the past. I'll be cruising at maybe 45-50 MPH at 125 MPG, come to a slight hill, give it a little gas to maintain speed, and it'll drop to about 75 MPG and start bucking. Sometimes really badly. Giving it more gas will drop it down to about 50 MPG and it'll run smooth again and begin accelerating. I can't maintain LB on level ground at highway speeds either.
Yep. I suspect that this is underdamped response to various inputs. I hope that examining air-fuel ratio, manifold air pressure, EGR position, injector pulse width, and maybe some other stuff (timing?) will tell a story. It might be nice to have a measurement of fuel rail pressure and some other stuff.

More progress soldering:
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hey sean i can tell you what happens when i tune my silverado too lean and put a load on it.. my knock sensor goes full tilt and pulls all the ignition advance out to save it from preignition resulting in Zero Power Mode.. obviously silverado wasn't designed to do lean burn hence why i tried it lol.
 

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Discussion Starter · #9 ·
@trickle Very interesting! It would be interesting if detonation is detected. I should be able to see this. Might actually be able to quantify the benefits of removing carbon and different grades of fuel!

Still making progress.on the wiring. This doesn't get old. Only 90 wires left!
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hey sean i can tell you what happens when i tune my silverado too lean and put a load on it.. my knock sensor goes full tilt and pulls all the ignition advance out to save it from preignition resulting in Zero Power Mode.. obviously silverado wasn't designed to do lean burn hence why i tried it lol.
Maybe Insights do that too. Mine will fire ATDC at low RPM and high load. Makes it feel like it's a 6000 lb Insight. I've thought about connecting a knock sensor to the ECM that's isolated from the engine to see what the timing is without knock. And carefully listen to how much it knocks! I should probably clean some injectors first.
 

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Could you add more to the thread title? A more descriptive title might be helpful in the future if this thread ends up with some good solutions.
 

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Discussion Starter · #14 ·
Umm, why not just use a scan tool?
Great question! I do own an advanced scanner that can read and clear the ECM, IMA, EPS, airbag etc systems. Newer cars use CAN for OBD but the G1 does not. The data rate is 10400 bits/sec or about 1000 bytes/sec but in fact most of that is overhead and one can only get less than 10 messages per sec (IIRC). In data stream modes, if you select all possible data, the sample rate drops to one sample every three or four seconds per item.

This will allow me to log 16 sensors for short periods at over 100 mega than samples/second, but 1000 samples/sec will be more than enough for most sensors. It will let me see what the ECU sees and how it responds, using charts. I'll share these once I have this running.
 

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Discussion Starter · #18 ·
I've thought about connecting a knock sensor to the ECM that's isolated from the engine to see what the timing is without knock. And carefully listen to how much it knocks!
I have a recording somewhere taken by connecting my knock sensor to a computer's mic input. It is just a piezo element tuned to a specific frequency with a piece of metal.

Which reminds me: a few weeks back I bought some small piezo sensors and some small magnets with the idea that I would tape them into various parts of the engine. Not sure if I will be able to do anything with that.

Was also thinking about adding an accelerometer to detect bucking but that also might not be too useful. The human butt is really good at detecting bucking among a bunch of road vibrations. Not so good at seeing it in a waveform.

it'll all be worth it when you turn the key and it works
Yes, because it is supposed to do nothing at all! I am checking connections twice so that I'm not naughty, but nice to my ECM.

Only 42 connections left!!!!!
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(getting more familiar with kicad is definitely increasing in priority...)
 
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