Rotec TBI issues

UH1CW2 · #1 06-29-2014, 01:24 PM

I just installed a new Rotec TBI unit on my aircraft. It was carbureted but I wanted to clean up the lower cowl area and install a 90 degree elbow to mount the ROTEC TBI to. I am talking about a RUTAN LONG EZ. I need this forums help with troubleshooting the issues. The unit seems to be starving the engine of fuel. I checked flow prior to the diaphragm. it was almost 20 GPH. I have checked the finger screen and it is clean. The unit will not allow the plane to idle below 900 RPM I need to have the mixture FULL RICH and the throttle open about 20%. The engine is chugging and stumbling like it is too lean. If I attempt to pull the mixture even a little bit off full rich the engine will die at any RPM. the 0320 runs extremely rough and struggles to maintain any RPM without choking for fuel. I was able to get 2400 static out of it today but I could not move the mixture lever off full rich or it would start popping and chugging for fuel. Even at 2400 WOT the engine was running like it was way too lean. It has a lightspeed electronic on the top and mag to support bottom ignition. I am running 100LL AV gas. When it was carburated it ran like a clock at any RPM, smooth.

UH1CW2@Gmail.com

Does anyone have any experience with the ROTEC TBI on a Lycoming engine. I need your help to resolve this issue. I have plenty of installation pics to review. I have a ROTEC 40-4 unit.

Respectfully,

Phil Camarda

judoka5051 · #2 06-29-2014, 04:00 PM

I had the same trouble with the rotec unit, and it got much worse after the fuel regulator was overheated by a nearby exhaust pipe. (Heat soaked while parked) it ran poorly after that. Is your exhaust near the regulator? Also, I asked for tech help and a price for parts to rebuild the regulator twice now and no response, so I've changed to a Marvel carb, old school but runs great.

Lance

rocketbob · #3 06-29-2014, 04:30 PM

What is your fuel pressure?

UH1CW2 · #4 06-29-2014, 08:04 PM

I am running the standard Lycoming low pressure pump 3-4 PSI and the FACET electric pump 2-3 PSI. I was told by ROTEC that they will operate on .5 to 10 PSI without issue. I just do not understand why the unit is running so lean at every RPM. I mean the mixture is WIDE OPEN or it will not keep running. I was told that these units are a design improvement over ELLISON units?

NYTOM · #5 06-29-2014, 08:36 PM

Email their techs with a description of the problem and they usually get back to you within a day. Big time difference. They have been very quick to answer questions I have had. You can message they from their web site.

UH1CW2 · #6 06-29-2014, 09:56 PM

Seems they do not have customers send back units like mine. instead they tell me to take the entire unit apart and inspect the inside for any lapping/polishing compound they may have left behind. They also said that they know they have this issue with Lycoming units 40-4 & 4/5 due to clogged spray bars and or idle path ways. this is caused by factory assembly of the unit with debris and lapping compound left in them. They also have issues with the wrong spring length in the regulators causing lean condition. To be honest I find this company to be out of the business selling parts at 1000 dollars if they do not work and expect the customer to troubleshoot and fix the issues. Not very happy with ROTEC at this time. Tomorrow will be a take down of the entire installation and a disassembly process of the entire unit. Should be a great day in the 95 degree wet Mississippi heat !

By the way, thank you for your help I do appreciate any comments that I received with this issue. I will post my findings in a day or so.

Respectfully,

Phil Camarda

pitts flyer · #7 06-29-2014, 11:49 PM

I have the Rotec TBI on my Pitts S1C. I had a similar problem when first intalled because it would not idle. Had to send back to the factory (paying the postage both ways), and they fixed the idle circuit. Ran fine for about 10 hours when the diaphram in the regulator had a leak--this you could tell because of fuel in the clear sense tube. After some back and forth--they wanted me to press the rivet more in the diaphram, and I wanted a new diaphram--I got my way and they sent the new diaphram. I have about 20 more hours on it with no problems. With a Pitts, 30 hours a year is pretty frequent flying.

If you can hang in there with their service (which happens but is not spectacular), the units run really good. Rotec is a small company it seems, and they have had their issues with their products (including some with their radial engines). But all that, I am still a fan of their products and I like their TBI.

Another issue (minor IMHO) that I have had, which is also a problem with the Ellison TBIs (now no longer made) is that the idle mixture changes with the seasons. Mine will idle wonderfully at 650 RPM when the engine is warm, but in the winter (such as it is in Sacramento, CA) Until the engine in warm, I have to keep the RPMs up or the engine will die. Once the engine is nice and warm--idles great. This means that in the winter, the startup and taxi to takeoff requires higher RPMs to keep the engine running.

I really like the primer button on the diaphram for starting when cold. Works great. No need for primer circuit like is required for the Ellisons. I use a bicycle cable arrangement to actuate.

If you are not doing acro, and space is not a problem, then yes a carburator is probably less problems, but in my situation, I really like the Rotec TBI, and I don't have a problem dealing with the idle in the winter.

BTW, I am putting a Rotec TBI on my RV-4. FWIW.....

rocketbob · #8 06-30-2014, 05:30 AM

You mentioned you have a 90 degree elbow...it could be that the airflow turbulent enough that the fuel is not being drawn out of the spraybar.

UH1CW2 · #9 06-30-2014, 08:37 PM

I took the unit off the plane this morning and brought it home to the shop. Took everything apart as instructed by ROTEC. Found the following issues:

Diaphragm spring too long. .698 cut to .605
Gray lapping compound in the idle fuel circuit
Gray lapping compound in the main fuel delivery chamber
holes in spray-bar not completely open

Cleaned everything with TBI spray cleaner, Blew all passages with air, opened up spray bar holes with a needle and reassembled. Installed TBI back on aircraft and it is now running as designed. On a positive note: I picked up 190 RPM on static run up. It was 2490 when carbureted now 2680. Need to make some small adjustments to the idle screw. I can not supply any other information until the wings go back on and I can get it in the air (about 2 months).

I want to say thank you to everyone who posted. Any advice and or assistance is always greatly appreciated.

Phil Camarda
www.LongEZPilot.com
www.Selectfirellc.com

Tony Spicer · #10 07-01-2014, 05:05 AM

Phil,

Did you have detailed instructions from Rotec, or "Just take it apart, clean it up and reassemble?"

If detailed instructions, any chance you could post them here?

I have one that will be installed soon, and am thinking that a preemptive cleaning may be a good idea.

FYI, Rotec will be at Oshkosh this year, booth 627 in north display area. 200 feet north of Van's booth.

Tony