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1. 10:46 AM - Re: Some ignition timing observations (Rob)
2. 11:30 AM - Re: Some ignition timing observations (Lynn Matteson)
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| Subject: | Re: Some ignition timing observations |
On 8/25/2011 11:25 AM, Naftali Horowitz 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
> >
> <lynnmatt@jps.net>
> >
> > 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)
> >
> >
> >
> >
> >==============
> >
> >
> > Lynn, When you read 34 degrees BTDC is that with the power on to
> the ElectroAir and the engine not yet started? The reason I ask is
> that Jeff Rose told me to switch the power to the ElectroAir on and
> read the degrees before starting the engine they should be showing 25,
> or .25 volts with a digital volt meter, which is the normal all the
> time BTDC degrees for the non-impluse Lyc 0320 mag. This a a way to
> verify that the basic setting for that engine is correct. Of course
> once the engine is started then the MAP takes over and advances the
> BTDC degrees accordingly. I am seeing up to 42 BTDC at 7000 MSL with
> about 18 Inches of MP but only show 25 when I turn power on without
> the engine running. I am concerned that I have too much advance but
> then again the Sears digital volt meter may not be that acurate, so I
> plan to try a couple of other digital volt meters and see if they all
> read the same.
Rob
> *
>
>
> *
Message 2
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| Subject: | Re: Some ignition timing observations |
Rob-
That 34 is with the power to the MAP on, and of course the Electroair
is on, also. (I installed a panel meter dedicated to reading the
advance coming from one of the controllers.) When
I turn on just the E'air, I get point-25 like you do. When I start
the engine, it still reads .25, but when I switch on the MAP it (did)
go to .38. This made me a little nervous, taxiing about at 38 degrees
advance at 1000' MSL, but I couldn't see that it did any harm.....low
power and all that. When I would go WOT, the timing would show .25
again, and would stay there until I pulled the throttle back to about
25 inches of MP,(or to some altitude) then it would gain 1 degree of
timing for each inch of MP under 25". This was at first. When the
MAP sensor went belly-up was when I'd get 34 degrees reading (0.34
volts) even when the engine was not running, but the MAP switch was
on. So it was apparently stuck somewhere along the line. My CFI
suggested the sensor had swallowed some fuel, but I removed it and I
couldn't smell anything, and besides, the sensor is higher than
anything else in the system, and I have all the vacuum tubing running
down to the intake manifold. I sent the sensor in for a checkup, and
to have them set the amount of advance to 1 and 1/2 degrees per inch
of MP, instead of 1 degree per inch.
Incidentally, when I showed the MAP sensor to my CFI, he was amazed
at how big it was....larger than those that he has dealt with, so
there's more to that little puppy than meets the eye.
Also, I tried 3 different multi-meters and they all read from .22 to .
26, including the panel meter that I have permanently installed, so
it's a ballpark thing, I guess. Did Jeff suggest that you install a
switch to cut out the MAP sensor? He did with me, but maybe that's
because my Jabiru application is still in the experimental stages.
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)
On Aug 26, 2011, at 1:42 PM, Rob wrote:
>> >
>> > Lynn, When you read 34 degrees BTDC is that with the power on
>> to the ElectroAir and the engine not yet started? The reason I
>> ask is that Jeff Rose told me to switch the power to the
>> ElectroAir on and read the degrees before starting the engine they
>> should be showing 25, or .25 volts with a digital volt meter,
>> which is the normal all the time BTDC degrees for the non-impluse
>> Lyc 0320 mag. This a a way to verify that the basic setting for
>> that engine is correct. Of course once the engine is started then
>> the MAP takes over and advances the BTDC degrees accordingly. I
>> am seeing up to 42 BTDC at 7000 MSL with about 18 Inches of MP but
>> only show 25 when I turn power on without the engine running. I
>> am concerned that I have too much advance but then again the Sears
>> digital volt meter may not be that acurate, so I plan to try a
>> couple of other digital volt meters and see if they all read the
>> same.
>
> Rob
>
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