95 replies to this topic

[Fordy]

Retarding the ignition actually did not help. Carrying out the ignition learning sessions had just retarded the ignition so much that it was starting to miss.

I carried out some fuel learning sessions and noticed that when operating in closed loop there was significantly less knock retard.

[Johnboyhgt]

Have you changed the pulley yet ?

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[Fordy]

Yes, I’ve fitted a 3.1” pulley and the LS4 throttle body

[Johnboyhgt]

Then you significantly changed the set up. Fuel learn before doing anything else. Make sure as many of the boxes go green as possible.

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[Fordy]

Fuel learn done concentrating on low rpm and full load cells. Changed those cells by about -7%. However, when looking at the knock retard values during the fuel learn they were significantly lower.

Made the changes permanent and did a logging session after and the knock retard was high again. So it seems that I am sensing knock whilst operating in open loop.

[Johnboyhgt]

Was the learn table full. Ie all rpm and all load boxes green or at the very least grey ?

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[Fordy]

No, as I am only getting the knock retard during full load I was just trying to update those cells for now to see if it helps.

[Johnboyhgt]

You're wasting you're time. Full learn.

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[Fordy]

I also looked back to the very first fuel learning session that I ever did where virtually every cell had over 199 measurements and there was no knock detected during the fuel learning session. Did a logging session afterwards and there were peaks of up to 8 degrees KR

[Johnboyhgt]

Fuel learn, ignition learn. Power run. Then let's take a look at what you have.

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[Johnboyhgt]

What's the injector duty cycle now ?

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[Fordy]

Thanks John, will do.

[FLD]

What fuel are you using?

[Fordy]

What fuel are you using?

 

99RON

 

Was using 95 but when changing to 99 it made no difference to the knock retard

[Exmantaa]

Why the LS4 throttlebody? I don't even use that bore on my Harrop TVS and still pushing ~350 on a good day...

[Exmantaa]

And do you get knock on a steady throttle, or on acceleration/throttle change? As that is a different table in OBD...

[Fordy]

Why the LS4 throttlebody? I don't even use that bore on my Harrop TVS and still pushing ~350 on a good day...

The supercharger kit that I purchased came with no throttle body. I could get the LS4 for the same price as the LSJ. Car is for track use so will spend most of its time at WOT. So better flow control for town driving not required. Why choke the flow?

[Fordy]

And do you get knock on a steady throttle, or on acceleration/throttle change? As that is a different table in OBD...

I get KR on acceleration. When operating in closed loop I get less KR. Seems that the engine prefers to be lean wrt KR. I could try lowering the transient fuelling tables to see if that helps.

If an excess of fuel is causing KR then is the sensor actually sensing knock?

[oakmere]

Mine is the same. Almost no KR when doing a fuel learn so AFR 14.7 but as soon as I put the fuel back 12.4 at 100 kpa the knock is back. Also type of fuel makes little difference. I get big spikes with large throttle inputs.
I am having another go at the ignition table to see if I can improve things.
Also I don’t let the knock learn alter the table as it tends to remove too much ignition advance. 2 degrees of KR may only need 0.5 retard to stop it.
The only thing our engines have in common is a skimmed head. Could it be something to do with this other than the obvious CR increase?
My engine has no physical signs of knock after years of driving like this so not sure if real or not.

[oakmere]

Also Peter has seen my logs and is not convinced it is real Knock.
On a power run it can come and go and move around the Rev range so it is not consistent. 🤔