Low ignition timing at idle 25DET NEO

[Dose Pipe Sutututu]

2 hours ago, Slap said:

Base case trimming 15-17
Ecu adds about 10 -13
Depending on fuel used as the ignition will add as much advance as it can at idle going back and forth adding and subtracting timming and fuel in accordance to air fuel ratios and knock voltage.

Maybe I'm wrong ... time to dig.

ECU doesn't add timing based on fuel used, unless you've got a full flex setup and there's ignition compensation strategy applied based on ethanol content.

 

[Slap]

ECU doesn't add timing based on fuel used, unless you've got a full flex setup and there's ignition compensation strategy applied based on ethanol content.   

 

The the narrow band o2 will feed the ecu the parrameters it sees and the ecu will use the maf and knock inputs too. To determine if it needs a fuel trim or timming trim.I know a bit about safc and if what you say is true it wouldn't lower the idle no matter what ...only advance timing on a skyline. But it does as it reduces airflow and it will concurrently raise timming as that is what a skyline ecu does with less airflow. 

The ecu has enough self learn features to fix small errors outside of the load map.

 

Nearly all fuel has ethanol now.

Especially higher octane fuels.

 

 

 

 

 

[Slap]

When I say fuel used I mean what type of fuel.

[Slap]

When I say fuel used I mean what type of fuel.

 

Wich if your car is used of 95 octane

And you run 98. Less knock more advance less injector. Until knock

 

[Slap]

omg I'm over the auto correct from my phone. Please read knowing this. I think I need 20 edits ahaha.

[Slap]

Whoever is reading this thread, please ignore what [mention=150098]Slap[/mention] is saying.
Nothing worse than cracking some ring lands or destroying your motor due to knock.
Do not advance your motor by 15 degrees on top of the base timing. You'll end up poorer and in tears.

[emoji35][emoji2959]

[Ben C34]

Slow down slap.

it's nice to try to help but you are bringing a fair bit of misinformation into this thread.

[GTSBoy]

Slap, it is time for you to stop now.  So many things that you have said are simply not in agreement with reality.

1. The ECU does not pay any attention to anything to do with the fuel when it comes to setting the timing at idle.  The only thing the ECU does is

a) try to operate the engine on IACV control to hit the target idle speed with the timing fixed to 15°BTDC.  Absolute, 15°, BTDC.

b) if it can't hit the idle speed target (if the idle is too high) it will use what is called delta control to use the timing to pull the idle back.  I have personally seen this happen on many RBs when the idle control is all gummed up and won't work.

 

2.  Nissan ECUs really do NOT run a sophisticated closed loop timing control such as you outlined.  There are many more modern ECUs that do exactly that (the Ford EEC-IV was one of the first).  But R32-4 ECUs really don't.  They have a single ignition timing target value for each and every cell in the map and that is what the ECU is programmed to hit.  The only time the ECU pulls timing is when it registers knock.  There are various strategies across the ECUs, from knock maps to simple -3° type deltas, but nothing sophisticated.  If you put better fuel into one of these cars, the ECU does not go winding the timing up looking for knock and then trim it back and then add some more.  The shitty old knock sensors on these things do not lend themselves to such sophistication.

 

3. Don't talk about SAFCs as if they are relevant to this discussion.  SAFCs are to ECUs what shovels are to scalpels.

 

45 minutes ago, Slap said:

But it does as it reduces airflow and it will concurrently raise timming as that is what a skyline ecu does with less airflow. 

I quoted this bit because it is important.  It is simply NOT TRUE that R3x ECUs raise timing with less airflow.  Certainly not true across the whole map.  Have you ever looked at a stock RB2x timing map?  The timing drops to lowest values at peak torque (basically the middle of the map in both speed and load axes) then rises again as you go above and below that part of the map.  More revs = more advance.  Less load that peak torque/efficiency = more advance.  More load than peak torque/efficiency also = more advance.

 

And, for one last time.  The timing values in the maps and as output on the Consult interface for "current ignition timing" are all absolute engine position with respect to TDC.  Not "imaginary 15° base setting + the value you see".  Just "the value you see".  That's it.  Provided the CAS is set correctly.  It is a loooooooong time since it was fashionable to turn up the power by advancing the CAS a few degrees to increase the timing.  That was 20 years ago.

[spudtatoe]

I moved the cas so it was 99% where it was before, where it is in the photo is how it sits as we speak. Tiny bit more to the right (advanced?) than the middle. 

now the IAC idle adjust is set so its about 700rpm.. thats the lowest I can sorta put it without the car not wanting to keep running when started. At some point in my combination of adjusting the idle and cas I had it at say 14 degrees but it was jumping all over the place and would stay still at idle, and then i believe the car wouldn't stay running.

 

How ive got it now seems okay - though now it seems like its a bit higher with about 50degrees timing when driving at certain throttle positions, as in ill be with a constant foot and it will be around that. 

Pretty damn unsure on if I should try adjust it more or just drive the 1400km with it like this.

[Slap]

Why on a timming light at idle are the rb jumpy then.
They move forward and backward with it.
They also monitor knock.
I have witnessed knock voltage resistance to get lower and lower and also raise at idle depending on both fuel type and timming.

Also you understand the idle valve controls airflow so really you just explained how the airflow part of the idle is controlled.

Yes they are set to a designated amount but they also add and subtract at idle.

I have had my 32 on a flex sensor for years using a stock ecu and a safc as an fcd.

The safc has to do with reducing airflow that advances timing.
Just like your idle valve it will impact on the ecu.

In an earlier post i should have corrected
Myself as I ment rb experience not rb25 experience but my phone is great for doin that to me and I cbf.

I would love to see a fact sheet can any one source one.
I'm not going to all of a sudden stop and believe you.

Ecu can advance timming.
Less air flow at specified load advances... this being idle atm. .
15 at the crank.
Knock voltage resistance targets as low as possible. Mine would use steps in .1v (2.4/2.1)
If it detected no knock it lowers the resistance to detect it and takes steps accordingly.

Why do people nistune if they were not sophisticated enough.

[Ben C34]

49 minutes ago, Slap said:

Knock voltage resistance targets as low as possible. Mine would use steps in .1v (2.4/2.1)
If it detected no knock it lowers the resistance to detect it and takes steps accordingly.

Wtf?

[GTSBoy]

41 minutes ago, Slap said:

Less air flow at specified load advances... this being idle atm. .
15 at the crank.
Knock voltage resistance targets as low as possible. Mine would use steps in .1v (2.4/2.1)
If it detected no knock it lowers the resistance to detect it and takes steps accordingly.

Why do people nistune if they were not sophisticated enough.

Let's attack just these bits.

The ECU only adjusts timing to achieve idle speed control if it cannot achieve it with the IACV.  Period.  It does not just add and subtract timing at idle when the AFM signal goes up and down.  It doesn't even bloody look at the AFM signal when it is on the idle maps.

You see all sorts of shitty timing variation on a timing light on an RB because the belt drive to the CAS is a source of dither and because the trigger wire (on the old igniters) is a shitty way to trigger a timing light.  If you put #1 coil on a plug lead and put the trigger on that you get a much better signal, but it is still full of crap from the CAS variation, etc.

The knock sensor is a piezoelectric transducer.  Basically a microphone.  It sends the noise it receives to the ECU when it is analysed by a dedicated part of the ECU (basically an audio notch filter to grab the right frequency range and a counter for knock events, which are basically click-noises).  There is no variable resistance involved in this.  The knock sensor has an impedance of about 500kohm (or somesuch value) and the only reason to know that is to replace it with a resistor if your sensor is f**ked and you need to stop it pulling timing without chucking a code from removing it entirely.

People do use Nistune because the stock ECU is a good thing.  BUT WHAT I AM TELLING YOU IS THAT IT IS AN OLD ECU DESIGN THAT IS NOT SOPHISTICATED ENOUGH TO DO CLOSED LOOP TIMING SEEK.

I use Nistune.  I have tuned mine myself.  I have worked a few times with Matt from Nistune to fix problems in the system.  And Dosepipe tunes many Nistunes.  We know these ECUs.

[Slap]

Look we have high jacked this thread far to much.
I would love to open a discussion thread on the ecu and it's workings.
I understand you guys tell me you tune them and yes you are firm on what you witness. So am I.

I move to open a new thread on the topic ecu capabilities.
And would love not only to read peoples experiences but facts printed and backed up.

ORIGINALY I SHOULD HAVE ONLY POSTED
'just try retarding the cas a lil'

I'm not trying to make you all believe me or get missinformation out there. I'm sharing my experience and was trying to help a skidder out.
You guys want me to believe so let's roll onto the new thread.

[GTSBoy]

1 hour ago, Slap said:

ORIGINALY I SHOULD HAVE ONLY POSTED
'just try retarding the cas a lil'

And you would have been giving poor advice.

[Slap]

Better than being missquoted and misunderstood.
And how would a slight retard of the cas hurt to try. Seeing as it was moved.

[Dose Pipe Sutututu]

3 hours ago, Slap said:

Why on a timming light at idle are the rb jumpy then.
They move forward and backward with it.

For idle stabilisation, unplug your TPS and your timing stops moving On a factory ECU.

[admS15]

Wow, my brain hurts and i just lost 10 mins of my life that I'll never get back.

[dr phil]

There is a reason that the stock ecu runs low ignition timing when it is trying to actively control idle speed, eg 5-10 deg, and jumping around. It runs low idle timing, combined with an elevated IAC opening, because if it needs to quickly increase torque ie idle rpm, it is very fast for it to increase ignition timing, ie it can react fast to a situation where it needs more torque, eg saving from a stall. Andy Whittle has a youtube vid of this strategy.

So yes this low ignition timing is what the stock neo ecu targets at idle, and yes it does jump around. Ignition timing changes make the engine react faster than opening IAC etc.

To adjust timing, you disable this idle control strategy, one way is to unplug TPS. This locks the ecu to command 15 deg, and a fixed IAC level. Then you adjust CAS with a timing light to 15 deg, AND the idle speed screw to 650rpm. Then you plug TPS back in and live happily ever after.

[Slap]

So by reseting the idle timing to 15° as far as the ecu sees...
Does this mean the ecu ads 0 ° advance now?

What is the max advance it can go?

Whats the max it can retard?

Where should it be ~ at idle?

What should i see on the light at the crank marks?

Thanks

[dr phil]

Well, it doesn’t so much add 0, really it is commanding 15 when locked, which should match to your timing light reading.

I would have to turn on my laptop and look at the idle map to give you the range it operates through at idle, i’d guess 3 to about 18 as the ecu sees fit to control the idle speed.