I was reading an interesting thread on this in the Main Discussion room and was thinking that some sort of in-car warning light/gauge would be very useful as 20 year old RS Turbo's have so many things that can fail and cause Det (Fuel pump, FP wiring, Metering head, fuel filter, FPR, etc) even fitting a new distributor, cap, or rotor arm and the timing being out slightly!

So is there anything we can hook up to the exisiting Det sensor? Or perhaps a 3rd party sensor located somewhere else as i know the standard ones are sensitive to tapping cams/lifters?

I may make something up myself and experiment after all they are mostly just piezo-electric microphones varying a voltage (although I dont want to make my engine det so not sure how i'm going to test it??)!!

Thought's and idea's are welcome!

Oh BTW this is not for tuning purposes so does not have to be mapable or hugely precise, but just a safe gaurd with plenty of headroom to protect our engines when other components fail.

 

A mate of mine uses one of these

http://www.phormula.co.uk/

Bloody impressive bit of kit although some would argue that 2 pipes and some ear protectors work as well

 

This kit to be exact

http://www.phormula.co.uk/ProTuningSolution.aspx

 

Thats a bit overkill for what I had in mind and expensive, just something to light a warning LED is all i'm thinking about.

For example, if I know at what output voltage the existing knock sensor is detecting det I can then have a simple circuit to light a red LED for a period of time to alert the driver that Det has occurred and that there is potentially a problem.

 

Knock Link then, far cheaper but in my eyes no where near as accurate. My matesin his Subaru would go mad all the time yet I he told me that was "normal" If the last light is blinking then surely thats bad IMO and if its ok then how long can it flash for before its not ok ? The Phormula setup is a lot more accurate and you dont have to buy that full kit, they start at under Ł200 for the actual incar unit and sensor

 

There isnt a voltage at which its detecting det, its not that simple sadly!

 

Still Ł150 for the kit, and I agree your mates info is confusing at best! lol

Surely a specific frequency (Say 5Khz) produces a specific voltage (say 3.0v) within certain tolerances? Enough for what i'm trying to do?
For example a voltage thats >2.5v and <3.5v = Det and so triggers timer circuit?
Or is there more to it, like it has to be within certain voltage parameters and or a certain length of time?
I can only think or those two variables (Time, Voltage) that our knock sensors are capable of changing?
But it's late and i'm tired so forgive me if i'm missing something hugely obvious

 

The problem is its not only knock that gives the "knock frequency", its present all the time in general engine operation to varying extents, with the biggest factor effecting its level being RPM

 

Ok so that does make it difficult to pin point, how does the ECU do it?

 

Which ecu?

Ive not sat there and decompiled them so I am being speculative, so dont take my word as gospel, but I would imagine that most modern ecu's will have a profile of expected background noise and look for variations from it, thats certainly how I would program it if I was writing the ECU software.
This is also what I would look to achieve on something like SM4 where you can map allowed values against rpm (or rpm and boost for that matter) and only turn the light on if those are exceeded

 

RS Turbo MFI ECU I was thinking of (purely because thats what I drive), although yeah I imagine you are right Chip that is how I would do it also.

I didnt realise that the frequency of Det is present throughout the running of the engine normally, thought it would stick out like a sore thumb! Which I supose it does to the human ear but as you say you would need to have a set of reference tables for any given ECU to compare live readings to and make a 'decision' based on that.

Well it was a nice idea whilst it lasted!

 

Engines are very messy noise wise, I dont think there is a frequency between 0 and 20Khz that isnt present in abundance at all times

Dont forget that you have first and second harmonics etc to deal with too.

 

lol
Yeah I think my idea of a frequecncy tuned piezo, timer circuit, and a LED was perhaps oversimplifying things a little!

 

Just a touch

It would still sell to subaru owners though if you gave it a catchy name

 

PMSL!

I'll call it the all new 'Dynamite Control System' and say it keeps your engine on the limit of Power vs Exploding for that real 'edge of your seat' driving experience!!

Only Ł999999999.99p

Orders to Email:

iwillrapeyourwallet@detonation.com

 

It worked with the knock block

 

That is so true