Rob,
We recently did a lot of research to prove or disprove the cooling rate/performance on a new engine install in a Taifun 17E2. The engine is a Rotax 914. Replacing a Limbach 2400. Our manometer was in fact an ASI using the pitot side on the high pressure side and the static on the low pressure side.. This works very well. We in fact ended up removing all baffles that had been set up in the conventional style to achieve the cooling required, but for a Limbach it would be very different as the Rotax is water cooled. Our main areas of concern were water temp, importantly oil temp. and barrel temp. We did have a separate FG shroud (Rotax) around the barrels which was supplied air directly from the cowl front by a separate opening. All results were extrapolated to a 38C day to meet the safe operating temps. The result was two oil coolers set up in series. The results have been very pleasing, surpassing the upper temp up to an ambient of 44c. We have an oil thermostat and hence cold temps were no issue. The bottom cowl was enlarged and had a moderate turndown lip with sidewalls. This is most effective. Regards Bob W VH-OFM From: dog@lists.riverland.net.au [mailto:dog@lists.riverland.net.au] On Behalf Of Rob Thompson Sent: Monday, 20 July 2020 10:17 AM To: dog@lists.riverland.net.au Subject: [DOG mailing list] Cooling airflow and Mixture relationship G'day Everyone, As many of you will know I am OCD about sealing every tiny air leak in the Limbach engine bay compartment with silicone, aluminium tape and rubber cowl seals. I have previously rigged up a water manometer in the cockpit with the tubes running to the top and bottom of the engine. It told me I was getting very good pressure difference but I didn't take much notice of the actual measurements. I think it was somewhere around 30cm. As well as the ram air going into the front of the engine the lower cowl is designed to "suck". We fitted a big scoop type bottom cowl which seems to suck pretty well.... particularly with the baffles tightly sealed with silicon. What I am wondering now is..... What is the effect of this extra suction at the back of the engine on the carbs and mixture? Maybe it is not much different to flying at altitude and the SU carbs altitude compensating ability can deal with it. Any fluid dynamics physics experts in this Dog group who can enlighten me? regards Rob Rob Thompson 0429 493 828 <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> Virus-free. <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> www.avg.com -- This email has been checked for viruses by AVG. https://www.avg.com
