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Knocking on Deceleration.

EFI Tuning Fundamentals

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Excuse my ignorance if this has been covered.

I am currently tuning my Honda Jazz 1.5L. I have a sprintex supercharger on it with 410CC RDX injectors. Im using KTuner software for reflashing which is restricted to AFM tuning and no speed density.

I have managed to set up a base tune with Ignition tables set up for boost and retarded -4 degrees all round. I have also found roughly a good starting point for my fueling tables.

I have noticed that I am not getting knocking when accelerating but when I lift off the throttle, knocking gets detected. If I decelerate with low throttle, knocking occurs with up to maybe 5 counts.

I dont have a knockbox, I am just relying on the stock knock sensor.

What would be the process of removing this type of detonation?



it's probably not detonating at all, it's just triggering noise. The knock sensor and knock algorithm is basically a microphone that is trained by the OEM tuner. When you start changing around engine hardware the noise profile changes. Also, engines are exponentially more noisy at high rpm, so letting off at a very high engine speed is likely creating noise.

If you have some control over the knock sensor sensitivity I would consider disabling it in that area of engine operation if you have confirmed that changing spark timing or fuel doesn't affect it.

Thanks for the tips.

I will keep that in mind.

do you have a lightweight flywheel, a solid hub clutch or both?

I have noticed a lot of noise with aluminum flywheels and solid hub clutches and a combination of both that is not actual engine knock.

I have not done anything to the flywheel. Only the clutch has been replaced with the Exedy Heavy duty clutch cover.

I wasnt sure if the engine mounts could also cause sounds as they are stiffened up with solid mounts.

It's almost impossible to encounter real detonation under those circumstances since there is no real cylinder pressure when you're completely off the throttle. I would also suspect the system is picking up some kind of mechanical noise and being triggered by that. I would only worry about knock that is being registered during medium to high load operation.

I see, I will investigate the source of the noise when I can. Im assuming it may be the exhaust.


Andre - sorry to hijack the thread, regarding the knock, i have completed the ignition map table on gear 3 till high load areas, but when i do WOT, there tends to be knocking at gear 2nd and 4th. should i be adjusting the timing map due to this knock? and see if there is any changes? i did try to retard the timing around that area, but the knock was not consistent registering a 2-3 knock count sometimes. Even though a completed 3rd gear WOT timing map adjustment were done as there is no knock registered.

And also, would i would see sometimes knock registering upon starting of the WOT ( area where the Close loop went to Open loop areas) -20,-10, 0 and 10kpa would be registering knock, this area i have been reducing the timing a lot maybe around 5-9deg reduced, are those areas i need to be concern? but this knock occurs some times only but at the same area and rpm zone at the low load where vacuum reading starting to go to positive pressures.

looking forward for your reply guys.

You should make a separate thread with more details about the project.

We usually reply within 12hrs (often sooner)

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