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Knock sensor
- Thread starter jonbills
- Start date
In fact, check this out ....
https://www.phormula.com/KnockCalculator.aspx
Get your piston sizes out!
https://www.phormula.com/KnockCalculator.aspx
Get your piston sizes out!
Yes, I think I’d alter the advance one waynor another. When I get the Nodiz ignition management working then I’d change the map.
I’m not really concerned that it has pre-ignition that I can’t hear - it was just something that came up in a conversation and it seemed like fun to have a go.
What I would say is that hearing your car pinking sometimes isn’t proof that you will always hear it when it pinks. (And pinking is indeed the knocking we’re talking about detecting)
With non standard vacuum advance or 3d ignition mappings, I think it quite possible that at high revs you could have dangerous detonation going on that you can’t hear, so it would be nice to have something to confirm it’s running right.
From what I read knock frequencies happen in the 6kHz to 8kHz range so you need a "band pass" filter.
The time honoured 741 op amp will do this job well.
I’ll read and digest, thanks.
Reading more on the topic, it appears that the sensor itself has a resonant frequency with very sharp drop off in voltage either side of that.
So sensor and engine need to be matched. Especially as the frequency band is very much a product of the pistons and block characteristics.
Also shielding is vital - at a max signal level of 0.7v it's going to be very susceptible to ignition and alternator noise (or indeed electric water pump / fan).
Additionally, I understand that the 280zx Turbo had a knock sensor which is the closest any of us will get to one matched to L6 ping / knock frequencies.
Question is, can you still source a working one? Or even a data sheet for it!? [emoji53] May need to surf the FSM to see if any specs are provided.
So sensor and engine need to be matched. Especially as the frequency band is very much a product of the pistons and block characteristics.
Also shielding is vital - at a max signal level of 0.7v it's going to be very susceptible to ignition and alternator noise (or indeed electric water pump / fan).
Additionally, I understand that the 280zx Turbo had a knock sensor which is the closest any of us will get to one matched to L6 ping / knock frequencies.
Question is, can you still source a working one? Or even a data sheet for it!? [emoji53] May need to surf the FSM to see if any specs are provided.
I REALLY love 'tinterweb!
L28ET knock sensor part number: Nissan Part No.: 22060-W1502
And positioning (part shown as 22060):
And the real thing -
Now I just need a spec sheet.
Mr Albrecht are you aware of such a thing in existence?
L28ET knock sensor part number: Nissan Part No.: 22060-W1502
And positioning (part shown as 22060):
And the real thing -
Now I just need a spec sheet.
Mr Albrecht are you aware of such a thing in existence?
Last edited:
johnymd
Club Member
By the time you hear the pinking its too late and the damage, however small, is done. All modern cars and modified ECU equiped car are fitted with knock control. This will not only give you the best possible performance under different driving and atmospheric conditions but also protect your engine if, for example, you get a bad batch of fuel or run very lean with fuel starvation.
That's interesting John - I'm not 'knocking it' (ha ha) but how have we managed for a century without knock sensors? The cars racing this weekend at Donington will not have knock sensors and they will run with a lot of advance. Can pre-ignition be identified on a rolling road with electronic monitoring?
Is pre-ignition a problem for Diesels ?
I know I'm an 'old school' type of car tuner but what I do is play with the ignition and try the car up the road, if it pinks under load I 'knock' it back a bit. Very often what sounds right in the garage and looks right on a timing light does not give the best performance. How do I find the correct and safe timing without a rolling road or knock sensor?
Can you explain what I'm looking at please John and how your car is tuned to eliminate knock.
Of course you are talking modified 1JZ technology whereas most of us have 50 year old L series technology (some on points!).
Interestingly John / Rob, what I was considering was getting a knock sensor working first and then using it to flash an LED and somehow(not thought about it too deaply yet) use a circuit to either cut the spark or work out a way to retard the timing on the 280zx dizzy electronically.
But how do you test it without damaging the engine in the process by causing knock?
Thinking about what you said Rob, are we all worrying too much on 50 year old design NA engines given all those years of successful motoring / racing without it!?
I can see why on forced induction it is crucial.
Like Johnny I'm fascinated by this topic and spark timing but I am also liking the challenge of doing it without an ecu / using the Nissan dizzy.
Diesels also suffer knock if injection timing is too advanced. Typically needs to be less than 15 before TDC. Also in diesels the intake stroke only takes air and the fuel is injected after intake has closed so less chance of pre-ignition / detonation events. (Unless of course you have an older diesel with swirl chambers etc). Modern diesels of course have several injection events (depending on load and throttle position) before, during and post ignition to reduce rattle / emissions and improve efficiency.
But how do you test it without damaging the engine in the process by causing knock?
Thinking about what you said Rob, are we all worrying too much on 50 year old design NA engines given all those years of successful motoring / racing without it!?
I can see why on forced induction it is crucial.
Like Johnny I'm fascinated by this topic and spark timing but I am also liking the challenge of doing it without an ecu / using the Nissan dizzy.
Diesels also suffer knock if injection timing is too advanced. Typically needs to be less than 15 before TDC. Also in diesels the intake stroke only takes air and the fuel is injected after intake has closed so less chance of pre-ignition / detonation events. (Unless of course you have an older diesel with swirl chambers etc). Modern diesels of course have several injection events (depending on load and throttle position) before, during and post ignition to reduce rattle / emissions and improve efficiency.
johnymd
Club Member
I'll try to answer as best I can but I'm not an expert.
Cars running carbs and dizzys can at best be setup safe with allowance for all situations. If setup on a rolling road then the operator will make allowances for different conditions. A carb will automatically adjust to variations in air but an ECU will have to be told what to do with changes in air temp and pressure. If an "old School" car is mapped too close to its limits of ingnition and AFR then failure will occur if things like octain of charge temp change too much and this has been seen with a zed race engine last year. If an ECU had been used and configured correctly then ingnition and fueling would have been modified automatically to suit the conditions.
Knock will be motitored with "cans" at a rolling road session and made to run safe.
It is hard to find the best settings Rob but for most of us we won't even feel the difference.
To explain this screenshot a bit. It is a sellection of perameters I've chosen from a massive list of logged data that lets me see how the knock control is working. The middle trace is for the knock sensor signal for each cylinder. The top trace is the ignition timming changes based on knock levels. It shows a retard value (based on Knock event level) and then ingnition advance being fed back in until it see's another knock event. This all happen per cylinder, per cyle with continuous changes in ignition. Each cylinder will run its own advance value independent of the other cylinders. It will lean and set values per cylinder but will alter around this value continuously.
On the lower section I've added a few traces so I can see with the engine is going at the time of the Knock events. It shows map and wastegate perameters.
Cars running carbs and dizzys can at best be setup safe with allowance for all situations. If setup on a rolling road then the operator will make allowances for different conditions. A carb will automatically adjust to variations in air but an ECU will have to be told what to do with changes in air temp and pressure. If an "old School" car is mapped too close to its limits of ingnition and AFR then failure will occur if things like octain of charge temp change too much and this has been seen with a zed race engine last year. If an ECU had been used and configured correctly then ingnition and fueling would have been modified automatically to suit the conditions.
Knock will be motitored with "cans" at a rolling road session and made to run safe.
It is hard to find the best settings Rob but for most of us we won't even feel the difference.
To explain this screenshot a bit. It is a sellection of perameters I've chosen from a massive list of logged data that lets me see how the knock control is working. The middle trace is for the knock sensor signal for each cylinder. The top trace is the ignition timming changes based on knock levels. It shows a retard value (based on Knock event level) and then ingnition advance being fed back in until it see's another knock event. This all happen per cylinder, per cyle with continuous changes in ignition. Each cylinder will run its own advance value independent of the other cylinders. It will lean and set values per cylinder but will alter around this value continuously.
On the lower section I've added a few traces so I can see with the engine is going at the time of the Knock events. It shows map and wastegate perameters.
Thanks a lot guys, pre-ignition is something I've never taken seriously apart from eliminating pinking.
As you know John my old car would run-on when I switched it off and I had to stall it. My blue car will do the same. Both are on SU type carbs (2" SU/ 1.75" Hitachi). My Samuri stops immediately (Webers). My old car had a compression pressure of 200lbs/in' and I think that combined with the type of carb was the cause. I know it can be a problem and was told that some people fit a solenoid on the balance tube to open the tube to air when the engine is switched off.
As you know John my old car would run-on when I switched it off and I had to stall it. My blue car will do the same. Both are on SU type carbs (2" SU/ 1.75" Hitachi). My Samuri stops immediately (Webers). My old car had a compression pressure of 200lbs/in' and I think that combined with the type of carb was the cause. I know it can be a problem and was told that some people fit a solenoid on the balance tube to open the tube to air when the engine is switched off.