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ETG Probes & their positioning
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Richard Stubbs
Hello Trevor
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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@... ____________________________ Free Email/SMTP/POP, , Hosting yourname@... ------------------------------------------------------------------------ Explore the popular High-End Room - Go To Where The Smart People Shop-uBid.com ------------------------------------------------------------------------ |
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