Best Knock Sensor Position ?
Discussion
Hi, I'm playing with a supercharged MX5 with an aftermarket ECU.
The knock sensor was fitted as per the instructions (low down on the block) and wasn't detecting any knock even though I could hear it.
I can't understand why it isn't working in the usual position as it's a very popular and highly regarded kit but I have tried a spare sensor with the same results.
I spoke to a Bentley mechanic and he told me that on Bentleys they are mounted on the intake manifold and the best place for them was the centre of the head.
I moved mine to the centre of the camcover with a bolt that connects into the head.
The problem I have now is that it's detecting too much !
IE it's hearing "noise" rather than knock - it's pulled about 20 degrees more than similar spec cars.
I can adjust the sensitivity but a quick google shows people saying the knock sensors mounted on the head have to be deactivated over approx 4500rpm due to too much noise
Has anyone had experience of this ?
The knock sensor was fitted as per the instructions (low down on the block) and wasn't detecting any knock even though I could hear it.
I can't understand why it isn't working in the usual position as it's a very popular and highly regarded kit but I have tried a spare sensor with the same results.
I spoke to a Bentley mechanic and he told me that on Bentleys they are mounted on the intake manifold and the best place for them was the centre of the head.
I moved mine to the centre of the camcover with a bolt that connects into the head.
The problem I have now is that it's detecting too much !
IE it's hearing "noise" rather than knock - it's pulled about 20 degrees more than similar spec cars.
I can adjust the sensitivity but a quick google shows people saying the knock sensors mounted on the head have to be deactivated over approx 4500rpm due to too much noise
Has anyone had experience of this ?
It's a fairly old ECU the only adjustment is the threshold level.
It was previously set at 20 and I raised it to 35.
Obviously I can raise it further but the instructions were to freely rev the engine and set the level above that noise.
The highest I got was 20.
I suspect if I set it much higher it won't be detecting low levels of knock.
It was previously set at 20 and I raised it to 35.
Obviously I can raise it further but the instructions were to freely rev the engine and set the level above that noise.
The highest I got was 20.
I suspect if I set it much higher it won't be detecting low levels of knock.
dblack1 said:
I don't see what is wrong with the original mounting location (between the IM and the oil filter)....
Mazda engineers put it there for a reason (I don't profess to know what goes on in their heads, but they are way better at designing engines than anybody in this forum). Unless your cool new supercharger setup is interfering with the sensor I wouldn't move it.
I wouldn't disable the sensor while using a supercharger either, that's a recipe for disaster.
Mazda engineers put it there for a reason (I don't profess to know what goes on in their heads, but they are way better at designing engines than anybody in this forum). Unless your cool new supercharger setup is interfering with the sensor I wouldn't move it.
I wouldn't disable the sensor while using a supercharger either, that's a recipe for disaster.
V8RX7 said:
As Std there was no knock sensor
Mine is a Mk1I was really trying to find out why you can't put it on the head or if there is an optimal position.
OEM frequently have their hands tied by manufacturing / cost constraints that the aftermarket don't.
stevieturbo said:
V8RX7 said:
Mine is a Mk1
I was really trying to find out why you can't put it on the head or if there is an optimal position.
OEM frequently have their hands tied by manufacturing / cost constraints that the aftermarket don't.
OEM spend a hell of a lot more money fine tuning their systems than any aftermarket system will ever come close to.I was really trying to find out why you can't put it on the head or if there is an optimal position.
OEM frequently have their hands tied by manufacturing / cost constraints that the aftermarket don't.
They will site the sensor where they deem best, and then they will also spend hundreds if not thousands of hours fine tuning the entire setup so it works.
Aftermarket just give you some parts and let you work away.....as you're trying to do now.
With a cheap ECU I can get more mpg AND more power than OEM
Because I don't have to worry about fuel standards in India or Emissions tests etc
Similarly OEM count every penny - if it's 10p cheaper to mount it on the block instead of the head - it will be mounted on the block.
They DON'T make the car the best they can - they make the best compromise they can within their budget, time and legal constraints.
stevesingo said:
If your system doesn't allow you to select the frequency, you are just listening to noise, not the specific noise you want to hear.
Yes I'm aware that's the issue I have.However I've been running 3 MX5s with this old Link ECU at close to double std output without issue for 5+ yrs so I'm not going to upgrade just yet albeit I'm aware there is much better kit out there.
As engines are available for £100 I'm not to concerned.
Richyvrlimited said:
The frequency that knock occurs as I understand it is a function of the bore size, this is hard coded into the FMLink ECU - they were year specific and in the states only 1989 to 1993 got a 1.6 all other cars were 1.8, all you need to adjust for knock detection is the threshold.
Mark I think your best bet is to try the OEM knock sensor position of the later cars and see where you get. it could be that this particular engine is very noisy.
AH !Mark I think your best bet is to try the OEM knock sensor position of the later cars and see where you get. it could be that this particular engine is very noisy.
You might have just solved my issue.
This was a 1.6 link that was converted to a 1.8 I wonder if there are any knock differences.
The starting point was that in the std FM position it detected virtually nothing (1 maybe 2) I moved it to the cam cover as a quick test really and there it detects up to 20 revving in neutral - which is about what it should get.
Problem I've had is that I'm still playing with my house and since posting about the issue I haven't had a chance to experiment with other positions.
dblack1 said:
V8RX7 said:
They don't.
With a cheap ECU I can get more mpg AND more power than OEM
Because I don't have to worry about fuel standards in India or Emissions tests etc
Similarly OEM count every penny - if it's 10p cheaper to mount it on the block instead of the head - it will be mounted on the block.
They DON'T make the car the best they can - they make the best compromise they can within their budget, time and legal constraints.
You are partially correct. Mazda engineers need to make the car affordable, so in order to reduce the price of the car, they do things like assemble the car on a line rather than hand building everything. The aftermarket provides a way for the end user to trade off affordability for other desired traits; however, your also compromising how well the vehicle was engineered. What I mean by this is, how many different ECUs did you try on your car? Did you take it to a dyno? the track? do any time of endurance stress testing?With a cheap ECU I can get more mpg AND more power than OEM
Because I don't have to worry about fuel standards in India or Emissions tests etc
Similarly OEM count every penny - if it's 10p cheaper to mount it on the block instead of the head - it will be mounted on the block.
They DON'T make the car the best they can - they make the best compromise they can within their budget, time and legal constraints.
Do you think that mazda just did a quick tune on the mx5 and called it good? or do you think they did the absolute best they could do in order to sell more cars? What is more cost effective, spending money to get the mx5 tuned right before manufacturing and selling more cars, or just getting it good enough and selling a lot less units? Many people believe that they can unleash significant power from their car with a quick tune. Aftermarket tunes gain power at the cost of reliability. They usually advance spark and/or adjust KR (both provide more power and MPG at the cost of reliability, and sometimes require higher octane fuel to run properly), another common technique to increase power is to increase boost on forced induction vehicles, which also reduces reliability. When it comes to that cheep ECU producing more "power" and MPG your actually burning cleaner than stock because of your advanced ignition timing, but mazda didn't know that, cause they where too cheap to pay somebody to actually tune the car.
I am not saying mazda engineers can't be out-engineered by the aftermarket, or even an individual, only that it is unlikely. Mazda engineers didn't tune the motor in a day, or even a month and they have way more dyno time with the BP motor than you (or anybody else probly).
This Link ECU has DLL software which allows you to log and perform dyno runs on the road and they have proven to be very effective.
The standard car runs too rich and many compromises are made for the various markets etc.
If you wish to keep telling yourselves that std is best then carry on - I meanwhile will carry on tinkering as I have for 20+ years and enjoying better, faster cars.
(Living in Solihull I know several of the test engineers from JLR so I'm aware what testing goes on and how they get their hands tied)
stevieturbo said:
V8RX7 said:
If you wish to keep telling yourselves that std is best then carry on - I meanwhile will carry on tinkering as I have for 20+ years and enjoying better, faster cars.
You do seem somewhat deluded. With your vast ability to produce such fast, powerful, reliable cars....maybe you should start building them and selling them. They're bound to sell well ! And as you can do it so cheaply, they'll be a bargain.I said new cars were a compromise - OTHERS said they were made the best they could.
I said they were tied by regulation - If I were to make new cars - I would have to adhere to those regs too !
I also said they were bound by price constraints.
Re read the thread then if you have any balls whatsoever you can apologise.
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