flak monkey
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 posted on 13/12/09 at 05:48 PM |
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Knocksense or Phormula
Debating which knock sensing route to go down. Quite important as I know full well I am going to have a problem at some point and I know I am not
going to be able to hear it!
The Duratec already has a knock sensor but I need some way of getting the signal from it.
Running an MS1 ecu, so could use knocksense which will allow me to automatically retard ignition when knock is detected. That said, I have heard they
can be a pain to set up and give a lot of false triggers. However this could be down to individual set ups.
The other option seems to be a Phormula system, which come highly rated all around, but are expensive (£220) and will not automatically retard the
ignition.
What should I do?
Or are there some more options I havent considered?
Sera
http://www.motosera.com
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sebastiaan
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| posted on 13/12/09 at 06:17 PM |
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The KS4 does have e 0-5V output, so you could use that to hook it up to the MS1. However, I would not like to rely on one of these things, as sensing
high speed knock (which is the sort that really kills engines) is going to be near impossible with these devices due to the high amount of engine
background noise. OEM knock sensing solutions get around this by only monitoring during the combustion period which makes things slightly easier.
If it is only for mapping (try to set the engine at borderline detonation or BLD and then retard the timing 3 degrees), hook a knock sensor up to a
small amplifier driving a pair of headphones. Your brain makes a better knockdetector then one of these boxes anyway....
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flak monkey
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| posted on 13/12/09 at 06:25 PM |
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Thanks for that.
Sadly headphones dont mix with wearing a helmet very well.  I know David Jenkins did just as you say, hooked up a small amplifier to his knock
sensor and did it that way. Though I could try small in ear types and see what that tells me. Not that I know what I am listening for!
I was of the impression that as rpm increases knock is less likely because there is both less time for it to happen and because the velocity of the
gas in the combustion chamber is so high that knock is less of an issue? I was more worried about knock in the cruising rpm range (1500-3000rpm) but
is this not the case?
Just trying to give my engine the best chance of long term survival 
Sera
http://www.motosera.com
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sebastiaan
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| posted on 13/12/09 at 06:42 PM |
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quote:
Originally posted by flak monkey
Thanks for that.
I was of the impression that as rpm increases knock is less likely because there is both less time for it to happen and because the velocity of the
gas in the combustion chamber is so high that knock is less of an issue? I was more worried about knock in the cruising rpm range (1500-3000rpm) but
is this not the case?
Yes, that is true, but if it does knock at high engine speeds, it'll wreck the engine quickly. Up to 3000-sih RPM, the knocksense / phormula
could very well work. If you're interested in engine design, get a copy of the bible:
Link to amazon
This also covers detonation / preignition
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sebastiaan
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| posted on 13/12/09 at 06:57 PM |
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some more info here: http://autospeed.com/cms/article.html?&A=0348
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flak monkey
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| posted on 13/12/09 at 07:32 PM |
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Excellent, thank you very much.
I may try the amp and headphones route first, will try and find some more sound files so I know what I am listening for!
Sera
http://www.motosera.com
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ashg
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| posted on 13/12/09 at 08:17 PM |
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get it setup on 95ron then run it on 97ron to be safe.
when i had my engine tuned/setup the guy tuning it had been doing engines 20-30 years and could hear knock by ear!!
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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flak monkey
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| posted on 13/12/09 at 09:26 PM |
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Following the instructions on the autospeed site looks like a good starting point. Managed to find a suitable amplifier, will have to have a play and
see what I can get out of it.
Sera
http://www.motosera.com
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David Jenkins
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| posted on 13/12/09 at 09:30 PM |
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Don't panic when you do listen to your engine - it will sound like a tin of spanners being shaken, even when it it's running properly!
I have a not-very-good WAV file that gives a clue about the sound that knock makes, but I'm not sure that I can post it here...
Oh - I can!
The knock is the nasty rasp near the end of the recording.
[Edited on 13/12/09 by David Jenkins]
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flak monkey
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| posted on 14/12/09 at 08:11 AM |
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Thanks David Could you point me in the right direction for a microphone transformer as mentioned on your website? Found this on the maplin site:
http://www.maplin.co.uk/Module.aspx?ModuleNo=12151
Is that the right sort of thing?
Will see how I get on once the engine is up and running, and no doubt there will be a load of questions.
Sera
http://www.motosera.com
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flak monkey
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| posted on 16/12/09 at 06:57 PM |
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Got myself the locost solution, cheap ampy thing off ebay to do the thing in the autospeed link above.
Also been speaking to Phormula, and their systems have variable sensitivity over the rpm range. Looks like the KS4 would be useful as a monitoring
system after setting it all up with the locost solution.
Sera
http://www.motosera.com
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