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Sorting out a Citrus

10K views 151 replies 20 participants last post by  kamesama980 
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.
 
for the logging part of this, are you just using your scope?.. just curious if you have intentions to input the data into separate logs and keep it all organized... im familiar with software where you can compare excell charts to frequency graphs like audacity and individual parameter values on a sidebar all at the same time once you have all of the inputs identified and scaled properly.. i have 100's of logs where i added notes and file through to compare mods and tunes 'cause and effect tuning on the road',, how are you going to organize the data? if you don't mind me asking
i know people that do these sorts of reverse engineering have used TunerPro free software.. i know you are technically minded, i just find all of it very fascinating from a distance. not trying to annoy and more trying to better understand, also sorry if you coded it into your previous posts and i didn't catch it
 
nice job sean, one thing to keep in mind is the phasing here, i first looked at your screen cap and almost fainted, than i remembered this is dealing with a 3cylinder engine on a 4stroke cycle.

-ckp is crank position- it is crank sensor pointed at a reluctor wheel, all engines ive dealt with this can be substituted for rpm but definately not familiar with 3 cylinder phasing, have to research what type of trigger wheel logic is being used.
tdc is typically cam position.. might be two of them for vtec?
injectors can be fired anywhere throughout the cycle, they are timing agnostic, but this 'phasing' can be altered to get different effects. determining where the factory phasing throughout the rpm band is going to be interesting from my point of view.
early speculation but i would assume at idle and in lean burn the injectors will be sprayed onto the back of a hot intake valve to increase atomization of small amounts of fuel in a low flow port injected scenario. but that is a total hunch.

super cool stuff
 
im very excited to see where this can lead.
open loop start up..
im sure the ecu has 'start table' which performs different levels of iac and inj pw cross referenced to different coolant temperatures and map values for healthy starts across the entire range of starting conditions.
eg. much more fuel and idle air at colder coolant temps, alternatively it uses less at hot coolant temps, there is probably a specific amount of time that iac tapers into a static state
 
ive yet to see ckp show signs of a 'missing tooth' style of reluctor wheel.. it could be counting teeth for RPM data and NEP could be phasing the ignition timing as the trigger??
really wish i was more intimate with my g1 sensors right now. i'll be staring at my motor until my feet get cold out there.
more data = more better

edit: crank sensor is simple 2 wire sensor counting teeth..
and looking at graphs provided so far, the nep is feeding the ignition coil, i would consider it to be ignition advance at this point in time, this is where a comparison to obd scanner could quickly verify.. hmm
 
im familiar with your past tests with egr. still wrapping my brain around the 3-cylinder cycle.. lol
my thoughts on AFR: at any given rate its really not as simple and/or fast acting as one would think, port injection is a dynamic mess, some fuel hits the port walls and puddles up until the valve opens again, some vapes off the valve, some shoots right in the hole. this all happens at different pumping air velocities because the intake manifold runners are shared, there is some reversion pumping to boot. This car uses VE tables, because it has no mass airflow sensor. Basically, there is different look up tables for the various sensors' vs load

At any given rate.. the egr job is to add inert volumes of gas into the incoming charge, theory behind it is fill the void for a leaner mixture while reducing Nox
the spark can only burn oxygen and gas, the egr reduces oxygen (by adding Inert gases) therefore the ecu can add less fuel for given qualifiers.
If egr is fluttering around all willy nilly like that, it's commanding erroneous injection pulse widths, allowing for erroneous 'actual mix ratios' to enter the cylinder, by the time all that info gets processed by the Laf it's too late.. the bad combustion event happened and continues to happen in a way that the ecu can't correct.
on a well-balanced four cylinder or a v8 it's probably much less pronounced than it is in the G1

The inherent out of balance three-cylinder four stroke cycle 'magnifies' the jerking motioin everyone speaks about

i hope this makes sense and helps paint a picture
 
I don't know what your next move is sean but i would gladly share the steps i would take after sorting out that epileptic egr valve. there could be a multitude of other hinderances effecting one another. I'm sorry for my 'loose' explanation above, I'm capable of being more thorough, but i very much enjoy learning how other people 'fix stuff'
 
12 teeth according to a drawing in the FSM. No missing tooth.
accurate reference Fumes.. 1 tooth = 30* ... 12teeth = 360* of crankshaft, compare that to seans 'mad scope shot above'

finally got my brain thinking 3 cylinder.. took a minute
i counted 24 ckp signals between tdc events, 720* of crank = 360* of cam = 1 four-stroke cycle

from there the ecu needs to keep track of 3 cylinders somehow, reference tdc1 and tdc2, the two cam sensors

firing order is 1,3,2 where;
cyl 1 = tdc1 and tdc 2 signals simultaneously
cyl 3 = tdc1 signal only
cyl 2 = tdc2 signal only
..than repeats

imagine this;
cyl1 fires at 0* ... 720* ...
cyl 3 fires at 240* ... 960* ...
cyl 2 fires at 480* ... 1200* ...
...240* between firing events.. 60* of which has no power stroke applied.. its why the car is gutless at low rpm without ima and contributes to the rocking motion that retires rotten rear motor mounts'

NEP signal switches high/low every 120*
360* / 120* = 3 cylinders
my intuition says input reference to ecu (like a tach signal)
ecu could use this as baseline for top dead center and convert it to different outputs like injection timing, spark advance, tachometer
 
NEP is an ECM tach signal output. I don't know what the letters NEP stand for, but the FSM says it's "engine speed pulse." The signal (A19 on the ECM) is sent to the MCM (C15), gauge cluster (A21), EPS (B14), and test tachometer connector (near brake master cylinder).
back to back excellent references Fumes.. were you a librarian in a former life?
Must be nice to have a FSM for this car beings its such an odd/pioneering car from honda. The EPS must need an on/off switch for autostop conditions?..
 
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