Walbro Carburettor.

Summer 2008: During testing I thought that the standard carb looked a little restrictive so again I turned to the internet. There was a Walbro style carb plus mounting kit on ebay for £15. I ordered it immediately and fitted it the day it arrived. Luckily the weather was fine that evening so Sam and I went onto the back field for some testing. We followed the tuning set up religiously but we couldn’t get the power we got from the standard carb. 28kg of thrust is enough for an average weight person to comfortably climb on a decent modern wing but it wasn’t going to be enough to break the bonds of Earth (unless you weighed 10 stone).

I was just about stuck for squeezing any more power out of the this small engine but could I temporarily get a bit extra just for take off? The answer was to add Nitrous Oxide injection. Many people on the net warn you that nitrous would burn out your engine but then others were stating that you are only increasing the amount of oxygen in the cylinder just like super/turbocharging. I thought it was worth a gamble. I ordered a kit off ebay and promptly fitted it to the motor. This particular kit is quite restrictive and so only lets the nitrous out slowly. Sam and I tested it and the revs climbed from the normal 8330rpm (28kg thrust) to 9240rpm (37kg thrust). According to the data sheet the nitrous adds an extra 1.5hp. If you run too much nitrous without additional fuel then the engine will run lean and over heat greatly increasing the risk of it seizing. I think 1.5hp increase is a safe level. I’ve ordered a larger carb jet to give us a smidge more power and to make more efficient use of the nitrous.

Nitrous Oxide Kit

Nitrous Oxide Kit

The 16gm cartridge is good for about 30+ seconds. I guess a typical take off would involve running as fast as possible with the engine at full throttle and only then applying the nitrous.

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