[Diy_efi] Crank sensor for knock detection?

Mike erazmus at iinet.net.au
Wed Mar 12 18:53:56 GMT 2003


Some of the knock sensors I have heard about (pun;)
can be really well hidden in weird locations behind
bits of the engine.

If you are talking n/a - I doubt many standard models
have knock detection. Turbo models is pretty much a
definite for OEM tuned setups, some people just
use a stethoscope or long tube wth rubber cup
when tuning and dont bother with
a sensor then map the onset of knock and back off
a tad when cementing the final map when off the dyno.

I'm curious why you are convinced there must be detection,
for a n/a in factory tune - arent they pretty conservative
so a knock detect isnt necessary ?

What are you referencing to come to your post query ?

rgds

mike
ps: too late for me, back to bed



At 12:38 PM 3/12/03 -0600, you wrote:
>Thanks for the help.  So how do production engines without a knock
>sensor adjust their timing when knock occurs?  Or do they adjust at all?
>I'm convinced there has to be some form of detection going on which
>causes the timing to be retarded, or is the software setup for a simple
>lookup table using variables such as IAT, RPM, MAP, TPS, and calculated
>engine load to determine a timing?
>
>Thanks
>Mike
>
>
>> -----Original Message-----
>> From: diy_efi-bounces at diy-efi.org 
>> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Mike
>> Sent: Wednesday, March 12, 2003 12:15 PM
>> To: List for general do-it-yourself EFI talk
>> Subject: RE: [Diy_efi] Crank sensor for knock detection?
>> 
>> 
>> I take you are talking instantaneous changes in rotational
>> velocity, from what i can recall on this subject from some
>> years back - the classic CAS has too little resolution
>> coupled with mechanical slop (for the dizzy CAS) and DSP
>> computational requirements (cost) precluded use on most common
>> vehicles - maybe for the higher luxury models, but whats
>> wrong with a microphone and FFT, gain selective with
>> respect to engine revs/load, also how would one
>> account for changes to rotational torque to feed into
>> CAS instantaneous changes over the life of the engine,
>> 
>> Honda went to some trouble with their ring gear brushless
>> servo motor to smooth out the instantaneous torque
>> fluctuations and I dont recall any knock detection but,
>> then it wasnt considered a performance model - 'prious'?
>> I think - the battery/hybrid on sale in Australia.
>> 
>> On my Nissan RB30 block there are 3 knock sensor tapped
>> locations between the relevant cylinders, though only
>> one of them is used for my ECU. I'm told the current block
>> is good for 1200hp without major mods as it already comes
>> with a big end cap girdle around all 7 mains.
>> Knock sensors are cheap and
>> three off for an engine like that might well be more
>> reliable than CAS given torque fluctuations will differ
>> from one end of the crank to the other !
>> 
>> rgds
>> 
>> mike
>
>
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