Mk2 Rotec TBI 👍

I recently fitted a new mk2 TBI to my 0-235 and found it would not flow enough fuel to supply the engine what it needed at full take off power. I played around with it a little. First I fitted the spray bar out of my old mk1 TBI that had no problem supplying the engine with plenty of fuel, still no go. Next I machined the regulator spring seat a bit deeper so I could use shims under the spring to experiment with varied spring pressures. That didn't work. My next move was to replace the regulator fuel flow valve with the old mk1 valve but before I did that I rang Rotec and told them what problem I was having wth the TBI. They told me to send it back to them. I did and within a week I had it back. Ok, I live in Australia but I can usually order and get parts from the USA quicker than I can get parts from interstate here in Aus !!!

Before fitting it I pulled it apart to see if it looked like they had modified anything. The only thing I could see was, they had replaced the regulator fuel flow valve. The valve that came with the TBI had the "O" ring seal glued onto the valve. The replacement valves "O" ring was seated into the valve and this allowed the valve to sear further into it's seat when closed. This results in the valve opening more when the diaphragm push's on it. First take off and climb out with the mk2 refitted resulted in me having to pull the mixture back some as it was supplying too much fuel !!!!

The mk2 TBI is now performing as well as the mk1 TBI. The reason for changing to the mk2 ?? The inbuilt regulator means less fuel line fittings. This makes me feel more comfortable with less things that can go wrong and there is a weight saving as well !!!

My understanding is, Rotec's new stock has the modified fuel metering valve. I bought mine nearly nine months before getting around to fitting it. I would suggest anyone with an " old stock" mk2 TBI, get onto Rotec to send you the later "modified" fuel metering valve.

Bob
RV9a

See my post toward the bottom of the page:

http://www.vansairforce.com/community/showthread.php?t=114648&highlight=rotec&page=12

Neil

MK1 TBI

Has anyone perfected a fool proof way to make the external regulator on the
MK 1 less or not susceptible to vapor lock? And in fact is it a major problem?
The only reason I ask is the fact that they introduced the MK2. Make?s a MK 1 owner worry a little.

Installing a tee fitting at the fuel inlet of the MKI regulator with an orificed fitting works well as a vapor return line. This fitting from vans works well:

http://www.vansaircraft.com/cgi-bin/store.cgi?ident=1525050358-238-12&browse=engines&product=va-128

I did this, along with a blast tube, and it fixed all my vapor lock issues. I?ve switched to the MKII since then and have a vapor return fitting available for that unit. You can PM me for details.