Today's Message Index:
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1. 07:47 AM - Some ignition timing observations (Lynn Matteson)
2. 11:29 AM - Re: Some ignition timing observations (Naftali Horowitz)
3. 01:29 PM - Re: Some ignition timing observations (Martin Hone)
Message 1
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| Subject: | Some ignition timing observations |
During some recent testing of a MAP sensor in my ignition system, I
observed that the ignition timing (a panel gauge shows the exact
ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor
down via a switch that I had been advised to install should such a
condition occur....this IS experimental, after all.
When I first started to run tests, the sensor was doing its job of
setting the timing according to conditions, then it started to
misbehave and I shut the sensor down, knowing that it was not right.
A couple of days later I decided to see what happened if I switched
the sensor back on. I did, and the panel gauge read 34 degrees BTDC
timing, and the EGT's started to go down dramatically. I kept an eye
on the CHT's and they didn't change much, staying right around the
300 degree mark (my CHT probes are located in a 50-75 degree F hotter
location than the under-the-plugs location) I didn't make any notes
about how times, temps, how temps changed, etc., because the EGT drop
had my attention. This test tells me that if the ignition event is
started earlier...before the standard 25 degrees BTDC...the fuel is
no longer burning when the exhaust valve opens, there is no longer
any fuel burning while the exhaust cycle is taking place, so the
EGT's are reduced. In this instance, I saw the EGT's go from the
1340's to about the 1260's. After that day I removed the sensor and
sent it to the factory for evaluation, so I haven't been able to
repeat the test. It stands to reason that if the ignition event is
started earlier, more heat should take place within the cylinder head
and not in the exhaust pipe, so CHT's should rise. When the unit is
returned to me, I'll repeat the test, taking better notes next time.
Of course the timing won't be stuck at 34 any longer, so I'll have to
fly it to an elevation, and set the throttle such that the timing
WILL be at 34 degrees. After that, I'll try other timing settings,
and be on the lookout for rising CHT readings.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062
Prince prop 64 x 30, P-tip
Electroair direct-fire ignition system
Rotec TBI-40 injection (sleeved to 36mm)
Status: flying with "Ramcharger" intake manifold...1162 hrs (since
3-27-2006)
Message 2
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| Subject: | Some ignition timing observations |
Beware of detonation turning into preignition.
> From: lynnmatt@jps.net
> Subject: JabiruEngine-List: Some ignition timing observations
> Date: Thu=2C 25 Aug 2011 10:43:02 -0400
> To: jabiruengines@yahoogroups.com=3B jabiruengine-list@matronics.com
>
>
> During some recent testing of a MAP sensor in my ignition system=2C I
> observed that the ignition timing (a panel gauge shows the exact
> ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor
> down via a switch that I had been advised to install should such a
> condition occur....this IS experimental=2C after all.
>
> When I first started to run tests=2C the sensor was doing its job of
> setting the timing according to conditions=2C then it started to
> misbehave and I shut the sensor down=2C knowing that it was not right.
> A couple of days later I decided to see what happened if I switched
> the sensor back on. I did=2C and the panel gauge read 34 degrees BTDC
> timing=2C and the EGT's started to go down dramatically. I kept an eye
> on the CHT's and they didn't change much=2C staying right around the
> 300 degree mark (my CHT probes are located in a 50-75 degree F hotter
> location than the under-the-plugs location) I didn't make any notes
> about how times=2C temps=2C how temps changed=2C etc.=2C because the EGT
drop
> had my attention. This test tells me that if the ignition event is
> started earlier...before the standard 25 degrees BTDC...the fuel is
> no longer burning when the exhaust valve opens=2C there is no longer
> any fuel burning while the exhaust cycle is taking place=2C so the
> EGT's are reduced. In this instance=2C I saw the EGT's go from the
> 1340's to about the 1260's. After that day I removed the sensor and
> sent it to the factory for evaluation=2C so I haven't been able to
> repeat the test. It stands to reason that if the ignition event is
> started earlier=2C more heat should take place within the cylinder head
> and not in the exhaust pipe=2C so CHT's should rise. When the unit is
> returned to me=2C I'll repeat the test=2C taking better notes next time.
> Of course the timing won't be stuck at 34 any longer=2C so I'll have to
> fly it to an elevation=2C and set the throttle such that the timing
> WILL be at 34 degrees. After that=2C I'll try other timing settings=2C
> and be on the lookout for rising CHT readings.
>
>
> Lynn Matteson
> Kitfox IV Speedster=2C taildragger
> Jabiru 2200=2C #2062
> Prince prop 64 x 30=2C P-tip
> Electroair direct-fire ignition system
> Rotec TBI-40 injection (sleeved to 36mm)
> Status: flying with "Ramcharger" intake manifold...1162 hrs (since
> 3-27-2006)
>
>
>
>
>
===========
===========
===========
===========
>
>
>
Message 3
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| Subject: | Re: Some ignition timing observations |
I don't see any evidence based on what Lynn has posted of either detonation
or pre-ignition. Although both are detrimental to an engine's longevity,
they are separate conditions. Over advanced timing and poor quality fuel
will assist in detonation, but poor cylinder head design and insufficient
squish is the main reason.
Cheers
Martin
On Fri, Aug 26, 2011 at 4:25 AM, Naftali Horowitz <naftalih@hotmail.com>wrote:
> Beware of detonation turning into preignition.
>
> > From: lynnmatt@jps.net
> > Subject: JabiruEngine-List: Some ignition timing observations
> > Date: Thu, 25 Aug 2011 10:43:02 -0400
> > To: jabiruengines@yahoogroups.com; jabiruengine-list@matronics.com
> >
> >
> >
> > During some recent testing of a MAP sensor in my ignition system, I
> > observed that the ignition timing (a panel gauge shows the exact
> > ignition timing) was stuck on 34 degrees BTDC. I shut the MAP sensor
> > down via a switch that I had been advised to install should such a
> > condition occur....this IS experimental, after all.
> >
> > When I first started to run tests, the sensor was doing its job of
> > setting the timing according to conditions, then it started to
> > misbehave and I shut the sensor down, knowing that it was not right.
> > A couple of days later I decided to see what happened if I switched
> > the sensor back on. I did, and the panel gauge read 34 degrees BTDC
> > timing, and the EGT's started to go down dramatically. I kept an eye
> > on the CHT's and they didn't change much, staying right around the
> > 300 degree mark (my CHT probes are located in a 50-75 degree F hotter
> > location than the under-the-plugs location) I didn't make any notes
> > about how times, temps, how temps changed, etc., because the EGT drop
> > had my attention. This test tells me that if the ignition event is
> > started earlier...before the standard 25 degrees BTDC...the fuel is
> > no longer burning when the exhaust valve opens, there is no longer
> > any fuel burning while the exhaust cycle is taking place, so the
> > EGT's are reduced. In this instance, I saw the EGT's go from the
> > 1340's to about the 1260's. After that day I removed the sensor and
> > sent it to the factory for evaluation, so I haven't been able to
> > repeat the test. It stands to reason that if the ignition event is
> > started earlier, more heat should take place within the cylinder head
> > and not in the exhaust pipe, so CHT's should rise. When the unit is
> > returned to me, I'll repeat the test, taking better notes next time.
> > Of course the timing won't be stuck at 34 any longer, so I'll have to
> > fly it to an elevation, and set the throttle such that the timing
> > WILL be at 34 degrees. After that, I'll try other timing settings,
> > and be on the lookout for rising CHT readings.
> >
> >
> > Lynn Matteson
> > Kitfox IV Speedster, taildragger
> > Jabiru 2200, #2062
> > Prince prop 64 x 30, P-tip
> > Electroair direct-fire ignition system
> > Rotec TBI-40 injection (sleeved to 36mm)
> > Status: flying with "Ramcharger" intake manifold...1162 hrs (since
> > 3-27-2006)
> >
> >
> >
> >
> >==============
> >
> >
> >
>
> *
>
> *
>
>
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