Building the new Bushbaby SAFARI

[Oupa-G]

Today spent some more time with the Whisper BMW and transferred the Bosvarkie map onto the Whispers Eboxi and after the fuel lines and a bad connection with the primary coil and other little devil troublemakers like the oil temp that wouldn't work wrong polarity etc. etc as happens in new aeroplanes . All in all I'm now happy and the temperatures are fine I'm getting the power and the backup system is sweet Derek and his partner Francois did all the changes that I requested on the baffling so now I'm prepared to sign out the paper work for the engine installation to be able to get the proving flight authorization. The Whisper is an impressive machine. With the test flying they will have to give me an idea of the power and revs they will be operating and then I will join them in the air with the laptoppie and do the final tuning so that we can get the economy. All very exciting, going home on Thursday , I did not know one can sleep so much. I have a spare prop and engine for the Bosvarkie and I want to finish the 40 hrs proving flight. I have done 20 so far. I also see the hits have passed 73000 mark. One instrument that I was given for X-mas by Ystervark en Vliegvark was a digital heat reading gun. What a wonderful little machine you just point two red laser dots on the piece of metal or anything and you get an instant temp read-out. I two tics you check all your probes the EGT probes , a cylinder misfiring , so you can change the correct plug, a little tool that is just magnificent. I'm enclosing a photo , being a present I'm not allowed to know what it cost but I know it wasn't cheap. With authority I can now say when a cooldrink is 5.4 degrees C it is just right


Cheers Oupa-G

[Miskiet]

Hi Oupa,

I'm interested to know how you tune for economy - Do you use EGT? Putting electronic control on engines is the only way to get them 100% in my opinion - Now if we can only get a kit for a 503!

Those infra red thermometers are very handy - I use them at work. Just a cautionary note - The reading depends on the emissivity of the surface (dull, black surfaces will read hotter than metallic silver surfaces even if they are at the same temperature). But it sure beats touching something to check if it's hot!

[Oupa-G]

Miskiet

That slight difference is of no importance to me. It sure beats having to take a probe out and put it in boiling water and then adjust the 100 degrees with altitude where you are to calibrate the probe . Now you are in the ballpark immediately. On the four strokes we tune EGT. If you tune Lambda you are at maximum EGT and on full power you are going to run in to trouble. In cruis and at reduced power you can go maximum EGT or even on the lean side of peak and use Lambda, I'm not greatly in favour of this because then the exhaust flame is an oxidising flame. On the rich side of peak it is a reducing flame much less aggressive. The GAMI injector people run on the lean side of peak. The big radials on the DC$'s and sixes and the Constelations ran lean of peak. For our microlights we are not flying trans oceanic and that little bit of fuel I will gladly pay for not having a hole in a piston. The two strokes have different rules.


Cheers Oupa-G

[ystervark7]

To clarify some of Oupa-G's statements and answer Miskiet:
Miskiet is correct that you can only get maximum fuel efficiency with a lambda or similar sensor feedback system. While we might attempt to do this in future I am a bit hesitant to do it at this point because I would like the current system to proof it reliability before introducing more variables. I would also like to get long term fuel consumption data on the BB to make a judgment if it is really worth it.

Regarding the lambda feedback system note that the lambda control is only active once the engine has warmed up and below a certain rev limit. Above the rev limit, the lambda control system is inactive and the unit runs from a fixed map. If you try and run the engine at optimal efficiency using lambda feedback control at high revs you will overheat the engine, therefore it is set to run rich from a map. I am not sure where the cutoff point is but I would guess somewhere around your peak torque which is about 5500 RPM on the BMW. I also think that it would be possible to tune the engine quite close to its optimal at the peak torque without any lambda feedback just using the EGT's. Do keep in mind that in a car the torque varies dramatically due to hills and gear changes while you have close to the same torque for a specific RPM if you have a fixed pitch propeller.

Another complication with lambda sensors are that they are finicky, any contamination such as lead, silicone or antifreeze will ruin them. If you therefore add Afgas or leaded petrol by accident or because you do not have anything else available you will have to replace your sensors.

[Miskiet]

Thanks for the reply guys. I've been trying to educate myself with regard to electroninc engine control as I want to convert one of my old 4x4's to electronic fuel injection. It is diffeerent to using an engine in an aircraft.

Am I right in saying the following?

I thought of using the wideband lambda only as a set-up tool. You'd install your injectors, estimate their ms open time and start adjustments untill you get the Air:fuel ratio you want. Once it is set up you can remove the lambda or just use it for monitoring (Alternatively use EGT's for the smae purpose)

For idle: set up slighly rich so you get good pick-up from low revs (13:1??) for EGT around 750ºC?
For cruise: Set up at stoichiometric for best fuel efficiency (As Oupa said maybe slightly rich so there is no oxygen in your exhaust) (14:1??) EGT around 830ºC? Cruise in an aircraft is at 75% power - will stoichimetric fueling not be too hot as cars normally run at 50% power?
For high power: Rich so you get max power and cooler combustion (10:1) EGT around 700ºC?

Obviously you would scale these values to gradually blend into one another at the different engine rpm's. Thanks for a great article!!!

[KFA]

Hi Oupa, whats cooking? Did you guys replace the prop? Are you going to give the Woodcomp I sent a go? Ons almal wag in spanning

[pprop]

Beste Oom Frans,

Kortliks - die blok hout vir die 74 x 60 is gekies geskaaf en geplak en weeg 18kg. Die CAD tekeninge is gedoen enhet ek die finale ontwerpe goedgekeur vir vervaardiging Die CNC snywerk is klaar gedoen. Daar is n kort video van die snywerk van die einste propeller om te sien. Ek las dit by vir die wat graag wil sien. Die koolveselglas werk is pragtig deur Bets gedoen en die propeller het vandag sy eerste laag (van 4 lae) 2K gekry. Ek skat die propeller sal volgende week die urethane leading edge kry en dan die finale afwerking.

As iemand my to net kan wys hoe de duiwel om fotos en n video van die blok wat gesny word hier op te sit sal ek baie bly wees.... BOET!, Boet? Help n bietjie asseblief ou vrind !

[Oupa-G]

Pprop Baie dankie het vandag 'n nuwe GS enjin voorberei ex Kroonstad en gaan hom more insit RedX permitting. The fact that I'm on RedX duty does limit me a bit Had a hectic week after the holidays and am back will be writing more often in the future when I'm back in the swing of things


Cheers Oupa-G

[Oupa-G]

The South Easter is doing its 30kts stint and definitely no test flying. The new engine is in, have checked that no one previously has tampered with the cylinder assembly, all factory original. Also checked the torque on the camshaft bolts. this whole episode has set me back one month, were not talking about the money. But I suppose that is part of research and development. I must say that I cannot point a finger at the BMW. I can point fingers to the previous person that worked on the engine and to myself for not checking. But before X-mas I was in mechanical mode and not in thinking mode. Luckily when the engine stopped my training mode kicked in and the forced landing was OK. All I can say one must every now and then go through the forced landing routine you never know when you need it and it always is unexpected.


Cheers Oupa-G

[Oupa-G]

The new setup has been test run and I'm developing enough power have to hold her back because at the moment I have the 72X54 prop on it. Pprop is making a 74X60 which will be more a cruise prop. The Bosvarkie is so boyentand hops in the air so quickly that I can apply the power better in cruise. During the weekend I will give a total synopsis of all the happenings. Just finished another complete engine instalation for a customer from Natal it is going into a Explorer Boet is picking it up this weekend. I'm just waiting for the wind to drop the weatherman says Sunday.

Cheers Oupa-G

[KFA]

????????? The silence is killing me

[Trikenut]

Oupa G: This thread has just hit 1000 replies!! I just thought I'd point it out!
The amout of interest is awesome. I'm so glad this project atracted so much attention!!
Regards,
Ross

[RV4ker (RIP)]

While we wait, maybe a trip down memory lane for Oupa G...


I traded this beauty in on the RV6 and saw Oupa G as first reg SA owner in logs

[Oupa-G]

Thanks George that was a lekker aerie. The silence will be broken I flew the Bosvark on Sunday after the wind subsided. There was a long Saga and in case the loyal site hitters have wondered what happened , here is the story. As I said before I will do honest reporting here it follows. Before X-mas I was on my way testing the fuel consumption when just airborne the engine lost power I switch to all the systems switched the fuel pumps on , no power so I elected to do a forced landing. Luckily no scratch on the Bosvark and I trailered it home to the hangar. I pulled the engine and opened her up and found that somebody had worked on one cylinder and had never tightened the camshaft pulley. Needles to say this destroyed the engine valves and everything moving on the one side of the engine I looked at the engine and have decided to scrap this engine. I had the engine that I changed from a RT to a GS1200. My brain went into mechanic mode and in no time I changed the engines not thinking a serious case of tunnel vision. Objective change engine do not think. The engine was swapped and ground run all temp OK luckily the wind was not nice for flying so I opted for some ground running on the apron lifting the tail. Initially I had good power and then suddenly I lost control over the tail and had a prop strike. After the prop strike I had a low compression on one cylinder. Holidays came and went and coming back from vacation I did the compression check , one cylinder low. That was like 5 minutes running time. I lost control because I had lost airflow over the tail. I stripped the engine and it had ingested metal from the aircleaner I had never inspected. The first engine had blown back so much metal and pieces of valve stem that were all stuck between the butterfly and aircleaner. I went into thinking mode and replaced the engine cleaned out everything replaced the air-filters checked everything also checked all critical torque values, fitted the engine as first test ran it and flew the first flight on Sunday. All temps are superb and the fuel consumption test will continue. Then the net went down, but I'm back on line. To crown everything today somebody lost control over their Hi-Lux bakkie and drove through the workshop wall into the workshop. My whole workshop is a total shambles. However the test program stands at 20 hours and continuing.

Cheers Oupa-G

[Cloud Warrior]

Hope the Porsche is OK OG?