Thanks Richard,
I know I have the probe bosses in the right place as I've measured them from
factory units along with photographs as proof. I've just been informed the
engine will run hot for the first 25 hours or so because of the Nicasil
coating. 1300 degrees is not to be passed but 1200 is normal at first.
I'm still going to hook up an E.I.S. to see if they read the EGTs any
different.
--
Trevor Page
X-Air Ontario Dealer
tpage@...
From: "Richard Stubbs" <richard@...>
Reply-To: X-Air_Ultralight_Aircraft@...
Date: Tue, 4 Jul 2000 01:51:46 +0200
To: <X-Air_Ultralight_Aircraft@...>
Subject: [X-Air_Ultralight_Aircraft] X-AIR CENTRAL Re: ETG Probes & their
positioning
Hello Trevor
As a general rule of thum, the position of your EGT probes needs to be 100mm
from the piston skirt. Establish the distance using a vernier from the
piston skirt to the end of your exhaust port and then add the difference
along your exhaust manifold to make up the 100mm not forgetting to include
the thickness of your gaskets. I don't know the Hirth motor although it's
success here in South Africa was short lived. I would like to suggest that
you contact the manufacturers of the "Hornet" fixed wing (the one that
resembles a Challenger) as this company has used the Hirth engine as
standard fare for many years and would seem happy with the product.
Best of luck
Richard Stubbs.
-----Original Message-----
From: XAir Main <tpage@...>
To: X-Air_Ultralight_Aircraft@...
<X-Air_Ultralight_Aircraft@...>
Date: Sunday, July 02, 2000 09:56
Subject: [X-Air_Ultralight_Aircraft] X-AIR CENTRAL Our plane has flown!
Smallproblem though...
Hi Guys,
I flew my plane today!
All was well except that I'm getting high EGTs. I'm running a 68" GSC wood
prop with 16 degrees of pitch and a Hirth 2706.
Both plugs are brown and not wet. The needle is a 15K2 and the main jets are
160s. I'm getting 1300 degrees on the EGTs at 6100 RPM and it settles to
about 1200 at cruise (4200 RPM) and 400 on the CHTs either way (I did see
the back cylinder go to 500 once). We've tried 170 main jets hoping to run
it richer to get the EGTs down but it made no difference on a second
circuit. Judging by the plugs we are running just fine. The engine seems to
running very well with no indication of wanting to quit (I know go ahead and
laugh, I know Murphy's Law very well thank you!)
I'm using the Mikuni pump and I also have an electric pump but have not
found that it makes a difference. We are wondering at this point if the
location of the EGT probes is causing a high reading. I welded the bosses
about 80 MM from the head gasket (verified with pictures taken of other
Hirths at Sun N Fun). My assistant tells me that the further away from the
engine the probes are the higher the reading because the fuel is still
burning on exhaust. I've looked at a 503 and 582 and the probes are much
closer (more like 30 mm) to the head.
We are thinking about hooking up an EIS with their probes to see if they are
reading properly. I'm using Westach gauges and probes.
Anyone have any suggestions otherwise?
--
Trevor Page
X-Air Ontario Dealer
tpage@...
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