eightyknots Posted September 23, 2015 Posted September 23, 2015 I will do it when I have finished modifying the muffler as I want to do the test on the same day only a hour or 2 apart. Just the engine rpm will tell as well. If I can turn the prop 200 or 300 rpm more with the same prop and pitch this has to mean more horsepower. Then you can increase the pitch a bit to drop the rpm back to what mine is set for which is 5250 to 5300 at full power on the ground. This gives me around 5250 on climb at 6o kts. Full power straight and level is 5600 rpm this returns around 95 knots. I dont necessarily want higher cruise speed it would only be another 2 knots or so. I want the extra grunt on takeoff for getting off the ground quick Any more news on the Rotax muffler?
Kyle Communications Posted September 23, 2015 Author Posted September 23, 2015 Hi Hank Yes I have done a fair bit of prep work. I took the original system off and setup the rotax one to get proper measurements. If I shift the 2 front pipes to the inside of the engine I can bring the rear pipes in as well. The bells that go on the engine pipes that go into the muffler will make the angles easy to do. This then allows me only to have to put in a 55mm section of skin for the rotax it was looking like I would have to fit 125mm in the middle as the spacer. The 55mm will be much better and it will all make a better install I think. just waiting to get some header donuts and some correct size stainless pipe to make up new engine pipes. I want to keep the original ICP system so I will have to make up all new pipes for the rotax one but it just means a bit more time and work . been busy with other projects at the moment and going away up to the farm this weekend...will miss the Pacific Haven flyin but will call in there on the way home from the farm on Sunday morning. I have been really enjoying flying the girlfriend with the new dash installed. It is so good now being able to see everything almost at once. I have been doing some testing too now I have a analogue ASI it needs calibrating it is very accurate from about 60kts up but from 60 down it starts going out . at the lower end it is reading about 5kts high which is a bit iffy but I will remark it. Doing some stall tests and it is quite impressive the Sav. I can fly along reducing speed but maintaining height and without flap I stall at 34kts . With first stage of flap it stalls around 28 kts I never use full flap so didnt bother with that. I have been recording this on the HD cameras but will get some better angles and post the video when I get it done. Hoped to go flying last weekend but the weather was crap so didnt bother. Those speeds were taken from my MGL and the Avmap with AHRS that is in the dash as well. I was just seeing how far out the analogue is Mark
eightyknots Posted September 23, 2015 Posted September 23, 2015 Hi HankYes I have done a fair bit of prep work. I took the original system off and setup the rotax one to get proper measurements. If I shift the 2 front pipes to the inside of the engine I can bring the rear pipes in as well. The bells that go on the engine pipes that go into the muffler will make the angles easy to do. This then allows me only to have to put in a 55mm section of skin for the rotax it was looking like I would have to fit 125mm in the middle as the spacer. The 55mm will be much better and it will all make a better install I think. just waiting to get some header donuts and some correct size stainless pipe to make up new engine pipes. I want to keep the original ICP system so I will have to make up all new pipes for the rotax one but it just means a bit more time and work . been busy with other projects at the moment and going away up to the farm this weekend...will miss the Pacific Haven flyin but will call in there on the way home from the farm on Sunday morning. I have been really enjoying flying the girlfriend with the new dash installed. It is so good now being able to see everything almost at once. I have been doing some testing too now I have a analogue ASI it needs calibrating it is very accurate from about 60kts up but from 60 down it starts going out . at the lower end it is reading about 5kts high which is a bit iffy but I will remark it. Doing some stall tests and it is quite impressive the Sav. I can fly along reducing speed but maintaining height and without flap I stall at 34kts . With first stage of flap it stalls around 28 kts I never use full flap so didnt bother with that. I have been recording this on the HD cameras but will get some better angles and post the video when I get it done. Hoped to go flying last weekend but the weather was crap so didnt bother. Those speeds were taken from my MGL and the Avmap with AHRS that is in the dash as well. I was just seeing how far out the analogue is Mark I wonder if the proposed Rotax muffler setup will be lighter than the ICP one? A weight saving is always welcome.
eightyknots Posted September 23, 2015 Posted September 23, 2015 It is interesting that ICP gives the XL's stall speed with full flaps as 26 knots. But you are able get 28 with first stage flaps. Pretty good.
Kyle Communications Posted September 23, 2015 Author Posted September 23, 2015 just handling both systems I think the rotax will be heavier but not by much maybe only a few hundred grams
Geoff13 Posted September 23, 2015 Posted September 23, 2015 I have been thinking about your muffler Mark. The reason for changing if I have it correct was to get more power by getting closer to the Rotax recommended 5 litre capacity. So no instead of the smaller Savannah muffler you are taking a 5 litre Rotax one and making it larger. Be careful that you do not rob yourself of the extra power you are aiming to get. There is an optimum muffler capacity. You could easily end up with to much rather than to little for no actual gain. I would be revisiting trying to make the standard Rotax one fit.
Graham Pukallus Posted September 23, 2015 Posted September 23, 2015 Can recommend a very good avionics Tech who should be able to recalibrate your ASI. He did my altimeter out of my Savannah, while I waited and for a very reasonable rate. Give Fred Clej of Archerfield Avionics a call - 32770845 and give him the make and model to check if it can be re calibrated. Fred has also some second hand, fully serviced instruments with release notes in stock. He is at Hangar 2, Qantas Av, Archerfield Airport.
Kyle Communications Posted September 23, 2015 Author Posted September 23, 2015 Hi Geoff I dont want to change the capacity of the rotax muffler its purely a function of it will not fit if I dont change it. If I did it the easy way I would have had to add 125mm long section in the middle to get the inlets to fit. Its a function of the ring mount and the way its all setup under the Sav bonnet. Doing it the way I am now I only need a 55mm wide section which shouldnt increase the volume too much. I will ring old mate at archerfield Graham and see what he reckons on a price. Its not a critical instrument for me as I have 3 others that will show airspeed but I do like the analogue
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 Hi All Ok back onto the new muffler job seeing my new dash install and changeover was great and I am so happy with it. I had measured up and worked out that I need about 55mm inserted into the muffler to be able to get it to fit in a area where the engine pipes would be a relative easy run to the muffler. Finally got the time at work to get some SS sheet 1.6mm cut at 55mm wide and approx 500 long. We don't have a roller here so went over to a guy I know that has one of those 3 in 1 folder/roller/guillotines and rolled it to roughly where it needed to be with a overlap to allow adjustment and then showed the welder here at work what I needed. Voila here is the finished unit and I am very happy with it so far. This weekend I hope to start on the engine pipes if I can get some doughnuts and some pipe. The weather up here this weekend looks crappy so will be good to get a few things done 3
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 Ok the original size of the rotax muffler is 6.09 litres the now modified one is 6.32 litres so an increase of .85litres
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 Doh I can't subtract 0.23 litres extra volume so in the scheme of things it shouldn't effect it.
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 Yeah well I was looking at the muffler and thought those numbers were wrong. Bloody internet calculators.. Original rotax muffler is 5.465 litres modified muffler is now 6.312 litres added section is 0.847 litres
Geoff13 Posted October 8, 2015 Posted October 8, 2015 Thank you. You finally have it to a believable figure. So an increase of 16%. How many percent smaller than the Rotax muffler is the Savanah one. What I am getting at is if Rotax provide a muffler for optimum performance, and you are changing the Sav muffler to improve performance, you could be easily negating everything you hope to gain. Before you go much further it may pay to consider decreasing the volume some way. Possibly by shaving the bottom off a la Savanah muffler. By the way this post reminded me. I found that doughnut that I thought I had, will bring it up Saturday.
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 The sav muffler is a fair bit smaller than the std rotax muffler. I hope to measure that this weekend. I will have the sav muffler off again and will fill it with water and measure its capacity also will do the same with the modified rotax one. so it will compare apples with apples but there is a big difference as the 2 rear engine pipes on the ICP muffler are basically only about 30mm from a flat wall so there will be a fair restriction or backpressure issue on the 2 rear pots. There is a big difference in plug colour between the front plugs ad the rear plugs
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 If I can gain another 100 or 200 prop rpm on the same pitch setting then I can coarse up the prop a bit more which of course will give better performance. going on Rogers Spirit he sits on 4800 and I have to sit on 5200 to maintain the same speed. The Spirit is much heavier and has heaps more frontal area also Grahams has so much more accelleration off the mark he is running about 1 deg more pitch on his prop and basically we have the same Bolly prop
Kyle Communications Posted October 8, 2015 Author Posted October 8, 2015 That doughnut will be great as I am getting one from Danny so I can start this weekend on getting the engine pipes started. By the look of it I can basically make the same shape as the originals supplied they just need to be a little longer and the bells for the muffler end will need some judisicous fitting thats all
Kyle Communications Posted October 9, 2015 Author Posted October 9, 2015 Ok the results are in. The ICP muffler supplied with the kit when filled with water holds 3.3 litres of water . My modified Rotax muffler holds 6.3 litres of water and if you take off the extension I put in the std muffler is 5.46 litres so comparing the std one at 5.4 to the ICP one at 3.3 thats a huge difference just right there in volume. I have been trial fitting the Rotax this morning to see how long the pipes will be and the angles. I cant do a lot until I get the doughnuts but I got a length of SS 31.75 mm pipe this afternoon so can start getting all this ready 1
Geoff13 Posted October 9, 2015 Posted October 9, 2015 I should have mentioned, I think I have a metre or 2 of pipe left as well. 1
Kyle Communications Posted October 9, 2015 Author Posted October 9, 2015 Hi Geoff I got some pipe today but it maybe the wrong size as I have seen 3 different sizes used on pipe I have here. the pipe I got today was 31.75mm OD but Danny has 29mm the doughnut I got from Danny was 31.5mm and the old pipe with headers I have here is 30.4mm so I will see tomorrow. What time will you be there tomorrow as I have to go to Corroy tomorrow about 10.30 but hope to be cutting pipe when I get back
IBob Posted October 13, 2015 Posted October 13, 2015 Hi, I'm still awaiting my kit, which will be my first build, but this is really interesting, especially if it turns out that the Sav muffler is significantly degrading the Rotax performance. And I'm gazing with envy on your engineering facilities there too. Jumping back to an earlier comment you made re analog ASI: I noticed some folk have their pitot tilted down, on the theory that the reading is not accurate at high angles of attack. However, a friend of mine with a straight pitot on his VG reckons it reads fine at all angles against his GPS reading. What is the refresh/update rate on a GPS ASI reading: is it fast enough to give accurate readings during the landing flare, for instance??? Anyone???
Kyle Communications Posted October 13, 2015 Author Posted October 13, 2015 Hi Ibob I have gone through this ASI issue extensively after getting some honky readings. I have since changed my pitot to a 10mm tube it is straight though. John Gilpin (JG on this forum) has done extensive testing and he has his at a slight downward angle of about 5 deg to get a bit more accurate at higher angles of attack and that makes sense to me. Most pitots look like they hang down if you se the way ICP does it as it is quite long hanging out the front also most have some sort of tube between the wing and the tube so this helps the tube droop anyway. There is GPS lag ...BUT that is not your airspeed you are forgetting about wind. The GPS speed is only your speed across the ground not your actual airspeed over the wings so dont get caught Mark
IBob Posted October 13, 2015 Posted October 13, 2015 Thank you Mark. Airspeed/groundspeed. I will check what he was referring to. I'm interested because, while I know nothing about aircraft instrumentation, I deal with a fair bit of stuff where we have to factor in access or refresh rates. And yes, I've spent a fair bit of time reading JGs writings. I'm enjoying following the technical sides, though looking forward mainly to flying my a** off. Bob
Kyle Communications Posted October 13, 2015 Author Posted October 13, 2015 Well I hope you like flying in lots of wind especially where you are. A tip with the Savannah is dont use flaps at all for landing if the winds are over about 15 knots they tend to waffle about due to the flap arrangement and I never use full flap it is just too agressive just the first stage is all you ever really need unless you have to drop it in on a spot.
IBob Posted October 13, 2015 Posted October 13, 2015 The farming folk here talk of one year when it blew for 3 hundred and something days. But I'm happy to say we mostly get plenty of calm days too. Though, yes, we do need to keep one eye firmly on the weather. I'm fortunate that fallowdeer here will be some 200hrs ahead of me in his VG by the time I'm airborn, so I hope to learn from his experience too. Thanks for the flaps comment: as a late arrival to all this, I intend to be long on discretion, short on valor, and certainly not aiming to set any STOL records.
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