> Sent: Monday, September 21, 2015 at 6:56 PM > From: "Global Solutions via KRnet" <krnet at list.krnet.org> > To: "Kr mail list" <krnet at list.krnet.org> > Cc: "Global Solutions" <smcdonal at kos.net> > Subject: KR> Carb Recommendation > > Good Evening fellow Kr People. > Last week I had the pleasure of going for a ride in a KR2S aircraft at > the Oshawa airport. Upon inspection of the aircraft which was built and > flown by /Chris Gardiner. /His craftsmanship and attention to detail > gave me KR fever. > His aircraft was a solid well build VW powered aircraft. I am now > looking at carburetors for my 110 hp engine which currently is in a car. > From the reading and talking to others it would seem that several carbs > are an option and as such I would ask that anyone who has tested them > give me and the list some feedback as to the experience good or bad with > the following list or any others that have been tested. > > Marvel MA3-SPA > Stromberg NAS-3 > Ellison EFS-3A > Zenith 268 > Rotec #3 > > Regards > Stan
Stan, Most of these carbs are decent, but I would caution you that they need to be properly matched to the engine. MA3-SPA - Covers a whole class of carburetors used for anything from 85 - 165 hp engines, but have different sized venturies, jets, etc. Check the part number tag on the carb to see what engine it is supposed to fit and match that to your engine using this cross reference chart to make an educated guess. (http://www.kellyaerospace.com/fuel_charts/Carburetors/Facet_Marvel_Schebler_Carb.pdf) There are also other carbs of the MA-3 line that don't have the accelerator pump and work fine as well. If the carb isn't properly matched for venturi and main jet, it doesn't perform very well and the mixture control tends to be very touchy, especially if the venturi/jet is too large for your engine. Stromberg NAS-3 - There are also a number of jets and venturi sizes available depending on the model and intended engine, so be careful. No accelerator pump. Mixture (if equipped) is a manifold pressure backsuction to the float bowl and does not function at all like the Marvel carb you are used to using in most aircraft. That's the main reason why most are safetywired to the full rich position. They scare the heck out of the pilots that use them thinking they work like a Marvel Carb. Also, the carb tends to run pretty lean at mid range RPMs so tends to create a very flat throttle response when you add throttle on approach. Ellison EFS-3A - Should be a good unit. Mixes well. Should work well if it's properly matched to your engine. Zenith 268 - I don't have experience with that specific model, but have flown other Zeniths. While some have an adjustable main jet, you end up using a funky twist cable which makes for a bit of a non-standard configuration. Creativity helps here, but not my first choice. The Zenith I had, despite being new tended to drool fuel after about 40 hrs of flight time. Despite it being purchased new, it didn't impress me as aircraft quality. Rotec #3 - kind of a cheap copy of the Ellison, complete with a new set of problems. The Rotec throttle body that has the regulator separate from the throttle body itself has some pressure differential issues. I didn't fly this one myself. This was from a friend that was testing it on his aircraft, but didn't elaborate on the issue or why he didn't like it. The new version Rotec throttle body that was shamelessly copied from Ellison with the integral pressure regulator SHOULD perform like the Ellison, but I have no first (or even second) hand data on it. Aerocarb - Another single point throttle body drooler (think improved Posa). Can be made to work reasonably well, but is that what you want to be doing while test flying your aircraft? If it was me doing the buying, I would either run a Marvel that I know is the correct one for my engine, or an Ellison. I know NVAero is gearing up to provide the Ellisons, but don't known if they are currently available, nor do I know what, if any, improvements are being made to the Ellisons or the effect of those improvements. This isn't anything against Steve at NVAero, but I am not a fan of being an early adopter of an old product when the manufacturing and machining facilities change. As soon as I see that some are flying (and if they are, I hope Steve corrects me on this), my recommendation will be more positive. I know NVAero has acquired a good product in the Ellison throttle bodies. -Jeff Scott Los Alamos, NM
