[Diy_efi] Rich detonation?
niche at iinet.net.au
Mon Nov 20 22:02:42 CST 2006
On my car if I run it too rich it will stumble and not fire smoothly,
me thinks that this will cause other items to not run smoothly such
as valve clatter, wider changes in instantanteous acceleration/deacceleration
of the rotational motion of the crank causing maybe timing belt whip,
and who knows what other sympathetic resonances etc etc
Is it not possible that all this extra lumpy motion is wrongly interpreted
by your sensor ?
I took my detonation sensor off altogether and replaced it with a circuit
that fools the ECU to think its never suffering from detonation, I run 10.5psi
with a 3L RB30ET motor and a 'high flow' T3 turbo and set the mixture
slightly richer than stoich by the flakey pot on the AFM, end result is
improved fuel economy. Have been doing this for years, and last time I had
to take the head off (due to corrosion of a water gallery getting to close to
a chamber) I found no evidence of detonation or any damage to piston
crowns or valves. The engine has done 278,000Kms or so and the only
issue I now have is big end noise from worn big end bearings, last time I
changed these it lasted for about a year, looks like it needs it again, thats
what you get when using s/h bearings - but it still runs smoothly with just
a little big end clatter when revd through certain ranges (at no load I might
add), so its unlikely to be detonation. ie. Big end clatter tends to get queiter
the more load you put on it - unless its really bad...
btw: The detonation sensor signal on my ecu is ignored anyway beyond
about 3500 rpms - that says sopmething about these devices being susceptible
to a whole host of other noise sources as well as fact that the detonation
sensors dont have a habit of lasting long.
might I suggest try a brand new sensor and ensure the connections to it are
clean and tight
At 10:38 PM 11/20/06, you wrote:
>The reason for asking about rich detonation is that in my own experience when running AFRs lower than 10, the ECU will sometimes pick up knock - or at least interpret the signal from the knock sensor as knock. This causes the ECU to retard ignition timing and lower boost pressure.
>Sometimes this will happen when tuning at not particularly high boost pressures, but very rich mixtures.
>>At 03:23 PM 11/20/06, you wrote:
>>>The richer the mix the faster the burn. The leaner the mix the slower the burn. It is all about ignition timing, however the source of detonation aside from improper timing is from poor quality fuel or fuel not suited for a specific compression ratio. Poor fuel combined with hot spots in the combustion chamber results in pre-ignition. I'm not really sure what you mean by "rich detonation". The whole engine is a system... all the parts and processes must match.
>>My post arose as a result of responding to this post by Joseph Obernberger
>>who started the topic with the same subject line:-
>>> I've read in various places that it is possible to run an engine so rich that detonation can occur - or at least the knock sensor would pick up what sounded like detonation. Has anyone ever experienced this? Any truth to it?
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