Knock sensor

[jerry wass]

Where is the best location to mount a knock detector on a 4 cyl
Continental---(4each,O-470 jugs--314CID )

[Philippe[_4_]]

le mardi 8 juin 2010 06:32, Jerry Wass s'est penché sur son écritoire numérique et a écrit:

> Where is the best location to mount a knock detector on a 4 cyl
> Continental---(4each,O-470 jugs--314CID )

It's very difficult to known that. An aircoolded engine is more noisy
than liquid one.

try on a stud, I think you may read the piston noise for this barrel.
You need to choose beetwen the 4, the hightest EGT.

--
Pub: http://www.cd1d.com/
Philippe Vessaire Ò¿Ó¬

[Brian Whatcott]

Jerry Wass wrote:
> Where is the best location to mount a knock detector on a 4 cyl
> Continental---(4each,O-470 jugs--314CID )

The knee jerk response would be on the hot cylinder at the back!

Brian W

[[email protected]]

On Jun 8, 5:59*am, brian whatcott > wrote:
> Jerry Wass wrote:
> > Where is the best location to mount a knock detector on a 4 cyl
> > Continental---(4each,O-470 jugs--314CID )
>
> The knee jerk response would be on the hot cylinder at the back!
>
> Brian W

The knock sensor is to detect detonation, which occurs in the upper
combustion chamber. Knock sensors should go on the heads.

But what good are knock sensors unless you're using electronic
ignition with variable timing? Is that what the OP is using?

Dan

[jerry wass]

wrote:
> On Jun 8, 5:59 am, brian whatcott > wrote:
>> Jerry Wass wrote:
>>> Where is the best location to mount a knock detector on a 4 cyl
>>> Continental---(4each,O-470 jugs--314CID )
>> The knee jerk response would be on the hot cylinder at the back!
>>
>> Brian W
>
> The knock sensor is to detect detonation, which occurs in the upper
> combustion chamber. Knock sensors should go on the heads.
>
> But what good are knock sensors unless you're using electronic
> ignition with variable timing? Is that what the OP is using?
>
> Dan

Yes , it will have adjustable timing---, and, due to a fortuitous
acquisition of some mixed parts--(all new) a fairly high comp ration--
hence the need to monitor detonation if it occurs. Jerry

[Tom De Moor]

In article <a1caa092-5fa6-43f0-a5e4-756870757db9
@x27g2000prf.googlegroups.com>, says...
>
>
> The knock sensor is to detect detonation, which occurs in the upper
> combustion chamber. Knock sensors should go on the heads.
>
>
>

Which is not correct: a knock sensor can be placed anywhere on the motor
where detonation can be detected.

Due to the speed of sound in metals and the detection hysteresis on
electronics there is no gain in time if the sensor is placed on the
head. Let for memory that if your presumption where correct a sensor per
combustion chambre would be needed as the combustion chambers are
individual on most aero-engines.

On automotif engines like Peugeot Mi16 and Porsche (flat6 / V8) engines
the sensors are on the crackcase. For reduncency reasons knocks sensors
are mostly placed in pairs.

The main reason why they are on the crankcase is that they (and their
cabling) are better protected from heat and allow easier mechanical
intervention on the head.

As to detonation itself (experience on race-engines, not aero): it is
common practice to tune race-engines so that mild detonation occurs. The
reason is that detonation occurs with high compression ratio-engines or
engines, able to run on different octane-level fuels, when the ignition
is advanced (which yields more power).

Close to all automotif engines with knocksensors work along the same
principle: if no detonation is detected, the ignition is electronically
advanced. Upon detection the ECU retards the ignition.

The fact that detonation is detected, implies that it happened but if
action is performed within 10-20 enginecycles no damage occurs.

Regards,


Tom De Moor

[[email protected]]

On Thu, 10 Jun 2010 19:45:38 -0700 (PDT),
wrote:

>On Jun 8, 5:59Â*am, brian whatcott > wrote:
>> Jerry Wass wrote:
>> > Where is the best location to mount a knock detector on a 4 cyl
>> > Continental---(4each,O-470 jugs--314CID )
>>
>> The knee jerk response would be on the hot cylinder at the back!
>>
>> Brian W
>
> The knock sensor is to detect detonation, which occurs in the upper
>combustion chamber. Knock sensors should go on the heads.
>
> But what good are knock sensors unless you're using electronic
>ignition with variable timing? Is that what the OP is using?
>
>Dan
Knock sensors on automotive engines are virtually NEVER on the heads.
On the crankcase thy catch the knock amplified by the clearance on the
"big end" of the connecting rod and/or the knock through the cyl wall.

[Peter Dohm]

> wrote in message
...
> On Thu, 10 Jun 2010 19:45:38 -0700 (PDT),
> wrote:
>
>>On Jun 8, 5:59 am, brian whatcott > wrote:
>>> Jerry Wass wrote:
>>> > Where is the best location to mount a knock detector on a 4 cyl
>>> > Continental---(4each,O-470 jugs--314CID )
>>>
>>> The knee jerk response would be on the hot cylinder at the back!
>>>
>>> Brian W
>>
>> The knock sensor is to detect detonation, which occurs in the upper
>>combustion chamber. Knock sensors should go on the heads.
>>
>> But what good are knock sensors unless you're using electronic
>>ignition with variable timing? Is that what the OP is using?
>>
>>Dan
> Knock sensors on automotive engines are virtually NEVER on the heads.
> On the crankcase thy catch the knock amplified by the clearance on the
> "big end" of the connecting rod and/or the knock through the cyl wall.

That's really quite interesting, as I really never knew where they were
placed. But it suggests by inference that, at some time past, the
automotive manufacturers outfitted a few similar engines with a number of
knock sensors in various places and then found the locations which gave the
best sensing and the least variation between the cylinders. That should
have been fairly simple in the lab, especially when they intended to
manufacture thousands of identical engines, as they would only have needed
to vary the ignition timing for all cylinders together and vary the mixtures
for the cylinders individually--which should be easy with individual port
ingection.

Peter

[Capt. Geoffrey Thorpe]

"Peter Dohm" > wrote in message
...
> manufacture thousands of identical engines, as they would only have
> needed to vary the ignition timing for all cylinders together and vary
> the mixtures for the cylinders individually--which should be easy with
> individual port ingection.

Individual cylinder mixture would not typically be based on a knock
sensor - that is usually done via exhaust O2 sensors or crankshaft
acceleration (if at all).

--
Geoff
The Sea Hawk at Wow Way d0t Com
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