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Rotec TBI issues

Rotec TBI going too lean due to high temperatures.

Yesterday I found that after a long taxi out with the carb' heat on (intentionally, I was on very soft wet grass with OAT about 5 deg C, perfect carb' ice conditions) when I came to do power checks at 1700rpm the engine was running rough with a 250rpm drop on each ign' system (dual Pmags). The engine was running seriously lean, so I taxied back to the hanger, de-cowled and had a good look, nothing to see. The carb' temp' (I have a temp' sensor in the fuel gallery in the Rotec TBI) was at 25+DegC. I then ran the engine without cowls and the fault eventually disappeared.
Today I kept the carb' heat off, power checks normal, had a good fly. On return I kept the carb' heat on during taxi and found I could replicate the same fault (very lean mixture) once the carb' temp' reached 25degC+.
It would seem that for a reason yet to be determined the Rotec has a problem with high body temp's. (the pressure regulator is force air cooled so I suspect the reg' temp' was much lower).
This bit of info' may help some of you having issues with mixture.
I will email Rotec and run it by them and report back.
Happy Chrimbo All.
Neil
 
Rotec issues, rich idle mixture

No, I didn't get an explanation.
I now have about 55hrs on the Rotec, the first 40 on Avgas and about 15hrs running on Mogas (autofuel) with 5% Ethanol.
At about 10hrs I needed to lean off the idle mixture as it was too rich, and again at about 20hrs, but this time I had reached the limit of travel of the idle mixture screw, at about 25hrs I had a rich idle mix' that I could not adjust so had to open up the throttle stop so the engine would not foul and stop (idle at 950rpm, too fast.) I contacted Rotec who explained that the seals around the spray bar at the slide end are wearing and allowing unmetered fuel at idle, and that there is a modified slide with a longer seal. I have ordered the kit and a spare Mk1 TBI which I have just fitted, but yet to run/fly it.......any one else suffering this problem please?
No issues with the Mogas, the EGTs are about 10-15DegC lower, no noticeable difference in CHTs.
Looking at the spray bar where the holes are drilled at the WOT end I note that there is about 3/16" travel of the slide where no more holes are being exposed, this surely is the reason we are seeing a richer mixture with the slide partly closed, as opening the slide beyond exposing the last of the spray bar holes only allows more air with the same fuel supply, also the lower manifold pressure is sucking more fuel?
Neil
 
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350 hrs on TBI

Hi guys, I now have 350 hrs on a TBI 40 on a 0-235.

I'm in Australia so I bought my TBI when they were first released, in other words "out of the first batch".

I was still building at the time and I bought it at a huge discount because they wanted to get some "out there". It went back for a couple of up grades (mainly on the slide and seals) before I got my 9a in the air.

I love it, awesome fuel economy with the Rotec TBI and duel PMags. Smooth idle and instant power but I did find I needed a blast tube on the fuel inlet area of the TBI and the regulator.

But then at about 100hrs mine developed the same symptoms that Neil spoke of. Seal seepage. I returned the TBI to Rotec and they replaced the seals along with a new slide and spray bar, At around 200hrs it again developed the same symptoms and as I didn't want to have the 9a out of the air if I sent it back to them, Rotec sent me a new slide and spray bar with the new up-graded seals that Neil spoke of. When I pulled the old slide and spray bar out I noticed Rotec had slightly sanded one edge of the slide?? why??
After fitting the new slide and spray bar to the TBI, with close inspection, I noticed the spray bar was putting a slight pressure on one side of the new seal I had fitted to the TBI body. After a reinspection of the new seal fitment I was happy the seal was seated in nicely so it had to be something with the
new slide and TBI. Then I remembered the old slide being slightly sanded on one side. I then refitted the old slide and spray bar and there was no pressure on one side of the seal as there was with the new slide and bar. A slight sand on one side on a fine sanding block with the new slide and perfecto!!!

The Rotec TBI over the years hasn't been a case of "fit and forget" but with the awesome fuel economy and performance the Rotec gives it has been worth it. Here's hoping with the new seals it will be a case of fit and forget!!!

Bob

PS. Just a little bit of advise on using Mogas. I mainly use mogas but I have found the fine holes in the spray bar can "varnish" up if the aircraft is left sitting for 2-3 months. I have overcome this problem by using a fuel additive.
 
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It's at the hangar

I cannot remember the brand and I'll need to go out to the hangar to check but you can get it at the grass cutting machine shop. It's an additive you put in your grass tractor to stop the fuel in your tractor going off during winter recess.

Bob
 
I am an A&P and there are many SAFETY reasons why a TBI Ellison or Rotec is a bad idea. Support, especially from Rotec is HORRIBLE! They will talk a good story till you buy it then good luck exchanging e-mails on technical issues over days trying to resolve an item 2 minutes over the phone would resolve. From a safety stand point there is no source for notifying everyone with known problems and you ain't gunna get an AD--ever if there is one. They will not tell you or play down known problems nor will they notify you regarding them since it could hurt sales and they are not regulated. Example is the **** in the TBI known problem. Why do they still send out TBI's with this known problem? (AD level problem!) This should ring a bell in you head. The FAA isn't going to do much to help since they are protected behind the "experimental" disclaimer when you left the reservation. Marvel Schibler has 40-50 years of proven performance and there is a reliable history of documented issues and vapor lock is not a problem. Vapor lock, you know, that thing that causes engines to stop. Be smart on this one, if not for yourself for mom and kids. Now I know some of you out there are going to say I never had a problem with one and it runs great and I save a thimble of fuel per hour, but walking across a street blind folded and making it does not make it a smart idea. Lastly, there are two ways to be fooled: 1. Is when someone does it to you and 2. When the facts get in the way of what you want to believe.
 
Bentlr, why don't you tell us how you really feel? *wink*

Seriously, there are many years of usage data from Rotec and Ellison TBIs, and there doesn't seem to be this doom and gloom that you mention in your post.

Can you post some references as to the reliability issues that you mention? Web links, NTSB reports, things of that nature?

Thanks,

-Dj
 
Known issue with crud from the manufacturer left in the units. Still sending them out with known problems. Wonder if the FAA would let Marvel Schibler do that to their customers? Let me think, what's that word I'm looking for? --No. No mention of the fact that you had better install a primer lever to save your bacon when you have an emergency-found that out the hard way. Units prone to leak unless you turn off your fuel lever creating potential for fire and or fire on start should you get a backfire. Engine is expected and its normal to keep running if you pull the mixture lever off at idle. (means fuel is still available so don't move your prop!). They recommend you shut down by cutting off mags. And then there is good ole suseptablilty to vapor lock. All of this is in direct opposition with generally accepted safety practices. All may be acceptable for a race car but not an aircraft. And for what benefits? sustained inverted flight? Is that worth taking some safety risks. Take if from an ex Naval Aviator sustained inverted flight is not a pleasant experience for you or your passengers.
 
Hmmm interesting thoughts.

Let's perhaps do some logical analysis on the statements made by bentlr.

1) Shipping a product with known problems. Hmmm, I think every manufacturer in the business has done that. How about those Continental engines that suffered sudden stoppages as a result of catastrophic premature wear caused by machining swarf not removed at the factory prior to engine assembly? The FAA can't stop it and hasn't stopped it, ever. The FAA doesn't police each and every unit that gets shipped out the door. Similarly, the "known problems" with the Rotec TBI might be something akin to the float issues with M-S carbs. We're on what, the third or fourth variant of float now? How many people did those "sinking" plastic floats kill? Nope, the FAA didn't prevent those deaths.

2) Need a primer... Hmmm, seems to me there has been more than one M-S carb equipped aircraft that limped to the airport with the pilot frantically pumping the primer to keep the engine running. I wonder how they felt when they learned their FAA-certified M-S carb nearly killed them?

3) Units prone to leak. Yup, maybe. But then again, you've not mentioned Stromberg carbs which have leaked like sieves since the day they were manufactured. The Stromberg on my C85 engine requires that I shut off the fuel valve before exiting the aircraft. Nope, the FAA didn't catch that one, either.

4) Shut down the engine using the mags. Hmmm, that's one way. Or, like me with my Stromberg, shut the engine down with the fuel valve. The Stromberg doesn't even have idle cutoff capability, and yet it's been certified by the FAA (CAA back in those days) for three quarters of a century. Not all carbs have an idle cutoff feature, nor are they required to have such a feature. I guess the FAA missed that one. Go figure...

5) Vapor lock. Nope, no M-S carb has ever had fuel boiled in the float bowl. OK, maybe a few. OK, maybe more than few. Vapor lock is a function of installation design. Sure, the Rotec may be more susceptible than the M-S, but there are also ways of mitigating that susceptibility, just as we mitigate the susceptibility of our FAA-approved magnetos to premature heat-induced failure by providing them with blast tube cooling. Hmmm, who would have figured that one should have to use the time-honored tradition of providing cooling air to components that need to be cooled?

6) Sustained inverted flight... That's not why most folks install a Rotec, but if that's what floats your boat, the Rotec will help. For others, as has been stated quite a few times in this discussion thread and others on this forum, the motivation to install a Rotec isn't aerobatic flight but rather the ability to use mogas, E-10 mogas, to achieve leaner engine operations and maybe, just maybe, to move away from the M-S carb and its long litany of safety issues like split venturis and sinking floats.

This ain't the Navy with a fleet of hundreds or thousands of cookie-cutter airplanes produced under a contract and subjected to a conformity inspection at the end of the assembly line. This also ain't the certificated aircraft world where some folks work under the misguided notion that the FAA is there to keep them safe from every possible source of harm. This is experimental aviation where we are expected to educate ourselves to the greatest extent possible such that we may ensure our aircraft benefit from the most current safety enhancements. If you feel you need to live under the false sense of security as a result of being "protected" by some Big Brother outfit like the Navy or the FAA, perhaps experimental aviation isn't for you. For those of us who enjoy the challenge of taking full ownership and accountability for the safety of our aircraft, build on!
 
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Hi Bentlr,
I can't say as I have a lot of experience with the Rotec TBI, but I did install one on my O-320 and have been running with it for about 3 years with no issues.

There wasn't any crud in it that I am aware of, and the engine started and ran great the first time I cranked it after installation.

Their tech support was very helpful for the few questions that I had at installation time.

I have not had any leaks, although I normally turn off the fuel valve as part of the after-shutdown process. I've had a float stick in a carb which allowed fuel to drain all over the ramp, so this is second nature for me now.

The installation and operating instructions that I used clearly described that the engine will run at idle with the mixture pulled all the way out, and offered two options. The first is to shut the engine off with the ignition switches like a car. The second, the method I use, is to set the engine to about 1000 rpm, pull the mixture to idle, then advance the throttle until the engine dies, which ends up acting the same as pulling the mixture out on a carb (the engine dies quickly with not much throttle advance).

The manual also described the installation of a control to press the override button on the fuel regulator in the event of vapor lock (which I've never experienced) and to act as a primer at startup. It works so well that I removed the old plunger style priming system from the engine.

The manual also describes the installation of cooling blast tubes pointed at the TBI and the fuel regulator to reduce even further the chance of vapor lock.

None of this would seem to contradict accepted safety practices. It is perfectly normal to have different operating characteristics when you change to different hardware. We don't use the same operating techniques for a carb versus fuel injection, so why would we expect to use the same operating techniques for a TBI versus the carb, or a fixed pitch prop versus constant speed, or a turbine engine versus piston?
 
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Below is an e-mail received from a proud owner of a rotec TBI. His experiences have been similar to mine. 40 years of flying Marvel Schibers and experienced exactly none of these. You defenders are free to do as you wish. Still a free country. Advice: The wise don't need it an the others don't want it. Curious though, what were the other beneficial reasons for putting your life at unnecessary risk you didn't mention besides inverted flight? Whatever they are I missed them but they must be substancial. For the record my creditials to evaluate this problem from a safety stand point are as follows. Naval Aviation Training, Naval flight instuctor, Safety Officer and head of three aircraft maintenance departments ATP, CFI, Multi-engine, Helicopter, Helicopter Instrument, numerous type ratings and an A&P license. None of that necessary to see the obvious. Leaking fuel, No Idle cut off, admitted suseptability to vapor lock, production defects etc...are all safety issues of significant proportions. See my first post on two ways one can get fooled. Good luck with that!

E-mail from Rotec TBI unit owner.
(Those units are dangerous and they do not always slide when throttle is required. The slides stick. I have landed dead prop 2 times due to over rich condition. I have not been able to do a go around due to the throttle slide sticking. I use Bowden push pull cables and I also had a 5lb assist spring on throttle opening to make sure I could get power when needed.

The diaphragm has failed on me also and flooded out the engine on final approach. I have tried to work with ROTEX but they are arrogant and refuse to help. The price for replacement parts is outrageous and the shipping is always 80 dollars or more no matter how small the part,. They refuse to take the unit back and fix it when it was new unless I paid them 500 dollars plus shipping. I have spoken to the owner about having a US based support center for parts availability. Dealing with him is like dealing with a GERMAN over redesigning the VW. You get no place and end up pissed off and frustrated.

Please tell your friend that the TBI unit may take his life as it is not dependable at all and he will get zero support from the company. I look forward to seeing them at Sun and Fun or Oshkosh so I can speak with the clown/owner face to face.)
 
Ellison is a long established family owned business. Don't confuse the two companies or products. I have no experience with the Rotec product. I can only speak for my personal experiences with the Ellison product. I have no issue, complaints, or concerns.....

I will be happy and worry free flying it in my Bucker, as equipped with the Ellison for the previous 20 years. Fewer problems than any carb or injection system I have dealt with by far.....
 
I feel bad that your friend has had such a bad experience. I can sympathize that his experience sure sounds frustrating.

Things certainly may have changed since I installed mine 3 years ago, but I've had no leaks, engine shutdown works exactly as described, no vapor lock issues when installed properly following the installation instructions, no production defects found, slide works smoothly, and good tech support when I needed it. I know of others that have had the same experience that I have had, so I am not an isolated incident.

I have no connection to Rotec other than being a happy customer.

I converted from the carb to the TBI because the carb is not compatible with E10 autofuel. Carbs also have more moving parts to fail, and have issues with sticking floats, needles not seating properly, susceptible to carb ice, etc.

It sounds like your friend simply got a bad unit, which happens with any product (Lycoming crankshafts come to mind). I am surprised that the company wasn't willing to take the unit back for testing and make good on it. Did he ship it back to them?
 
Engine failure due Mk2 Rotec TBI

Hi Guys/Girls,
Just a "heads-up".
I had an engine failure at 1000' AGL in the climb out due to the fuel pressure regulator failing in my MK2 Rotec TBI. Fortunately I could make the reciprocal runway and no damage done.
However, this is a warning to anyone with a MK2 Rotec. The build of the fuel pressure regulator is suspect and needs to be checked.
The O ring within the regulator has been stuck to the centre pin with some sort of glue (not nice in my opinion) and either due to insufficient tolerance or some other cause the diaphragm and over-ride button will not allow fuel to flow to the spray bar, hence engine failure.
I believe this only affects MK2 Rotec TBIs, however, the internals are very similar to the MK1 fuel pressure regulator.
A possible way to detect if your regulator may be affected is to operate the over-ride button. Check to see if the button will go down another 1mm after fuel flows from the spray bar (with fuel pressure available to the TBI) This may indicate there is sufficient tolerance for the regulator to be reliable.
Neil
 
Neil, thank you for sharing. That is very good information to know. Did you happen to take any pictures when you had the fuel regulator apart?
 
Rotec TBi Fuel pressure regulator CHECK.

This post is from my personal findings after an engine failure shortly after take-off. It is not supported or sanctioned by Rotec. This post is not to undermine or critisise Rotec, their product or support. I do not wish this post to be used for apportioning blame or defamation of any individual or organisation. Ultimately any work or modifications carried out to your TBI should be under the advise of Rotec

23839841409_43b3dc48c0_s.jpg


Fuel Pressure Regulator Mk2, what to look for:
Two problems may occur with the Mk2 Rotec TBI in the fuel pressure regulator, if these problems occur engine run down is possible. (This may affect Mk1s also, I do not have personal experience of a problem, but the internal components are exactly the same apart from the disc T10.2 which is an integral part of the Mk1 separate fuel pressure regulator body.)

1-The fuel pressure regulator is opened by the diaphragm T18/disc T16 pushing on the nipple T11.

The distance the nipple can open is limited by the clearance between the end of the nipple and the deck height of the fuel pressure regulator body (Mk1) or the intermediate plate T10.2 (Mk2).

24125110961_7915862334_s.jpg

This picture shows the distance the nipple protruded above the deck on the failed Mk2 which was 0.4mm. I now have the replacement nipple with a different square section O ring from Rotec. This nipple protrudes 2.95mm above the deck. I therefore assume the distance the nipple can be opened on the correct set-up is about 3mm.

This available distance can be modified if the alloy disc T16 on the diaphragm is dished.
The dishing of the alloy disc on the diaphragm is caused by the peening over of the pin that passes through and retains the diaphragm. The dishing of the disc can be “toggled” either convex or concave.

https://farm2.staticflickr.com/1443/24181612196_2154b3a8ca_s.jpg

https://farm2.staticflickr.com/1470/24207703585_a496e27a38_s.jpg

If the disc is toggled concave it will reduce the amount the fuel pressure regulator nipple can open, and may even limit it to the point of closure leading to engine rundown.

2-Gluing of the O ring to the nipple.

Some people have had issues with the TBI dripping fuel when the engine is shut down, and/or being unable to shut the engine down using the lean cut method and bumping the throttle open. To address this Rotec and some TBI owners have glued the O ring to the nipple.

If the O ring T12 is glued to the nipple T11 and the O ring is not right against the spherical face of the nipple it pushes the nipple further away from the diaphragm and reduces the distance the nipple can be opened. If the distance the nipple can be opened is reduced in this way it may limit fuel flow to the spray bar.

https://farm2.staticflickr.com/1664/24125113141_47f6529219_s.jpg

In this case the use of the over-ride button will not open the nipple as it cannot push the nipple any further than the diaphragm can.

Rotec are now aware of the issues noted above. A modified nipple is available.

It is my view that any Rotec TBIs should be checked for correct dimensions and operation of the fuel pressure regulator.

Some of the early Rotec TBIs may have developed a rich idle mixture that is beyond adjustment via the idle mixture screw. This may be caused by fuel leaking past the spray bar seals. Rotec are aware of this issue and have developed longer seals which are retained not by a star clip but by roll pins, these units can be modified at the factory to the later seal specification.

Neil

Edit: Having posted this I can see the pictures are far too small to see. Please visit this page where full size photos can be found:

https://www.flickr.com/photos/62722241@N00/albums/72157647983156255
 
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The thought occurs to me, that if you want to just check the available distance the fuel valve can operate through it is possible to use the over-ride to do this:
1/Remove the air filter box so you can see the spray bar with the throttle wide open.
2/With fuel pressure available at the TBI use the over-ride button to start fuel flow to the spray bar, then measure the further distance the button will travel up to its limit.

Due to clearances from the inner tip of the over-ride button and the diaphragm this will not necessarily be the total distance that the nipple can move under influence of the diaphragm, but does show a minimum operating range of travel.
 
ALL DONE WITH ROTEC TBI

Well, after 2 engine failures on final, leaking diaphragm, lapping compound in the new TBI, having to replace spray bar seals, having to ad a 5.1 lb assist spring to help open the TBI slide when I needed power, having to drill and open up spray bar holes due to lean fuel and several thousand dollars in hardware and fabrication along with shipping charged from ROTEC I have pulled the TBI OFF the engine. We are back with a MA-4SPA and that is the way it will stay.

Rotec needs to improve their customer service, IT SUCKS! in addition they need to put better quality controls on the product during manufacturing and assembly. Some improvement required; they need to redesign the diaphragm housing bolt circle as it contributes to small rips/leak paths in the diaphragm near the outer bolt hole edges. The seals used on the spray bar and slide need to be X type and the Spray bar needs to be highly polished so the **** thing doesn't stick/bind and leave you with no available POWER! The last thing they need to due is have someone in the USA be a parts supplier as it costs 100 dollars in shipping every time you order a replacement part from Australia. After all I'll bet 90% of there business are US pilots and builders.

Just my humble opinion after dealing with them!:eek:
 
Phil, after all that, I don't blame you.

I'm going on three+ years with my Rotec TBI setup and no issues so far.

If I ever do have issues I'll likely just go to fuel injection.
 
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I saw an add for a Rotec and was about to pull the trigger, but you guys are scaring me. Seems like they're a lot of trouble. I am decent with tools, but certainly not an A/P or builder. I would be frustrated as heck if I had these troubles. Need to reconsider. Don't want to find myself regretting getting rid of my carb that runs perfectly to put on a lot of hassle and frustrations...

Are the Ellisons any better?
 
I saw an add for a Rotec and was about to pull the trigger, but you guys are scaring me. Seems like they're a lot of trouble. I am decent with tools, but certainly not an A/P or builder. I would be frustrated as heck if I had these troubles. Need to reconsider. Don't want to find myself regretting getting rid of my carb that runs perfectly to put on a lot of hassle and frustrations...

Are the Ellisons any better?
I wouldn't worry too much about the Rotec, I have a one on my O-340 and other than a few instances of vapour lock (probably to be expected running Mogas on a 40*C day...), have not had any other problems with it. I like it, it looks great, was dead simple to install, idles smoothly and gives good economy. I recently swapped to a MkII TBI that has the internal regulator and that seems to have helped the vapour lock issues, but I also used exhaust wrap to insulate around the fuel lines & gascolator at the same time so it's hard to say for sure.

The only issue I have had is indicated fuel flow went from 24-25LPH (6.5GPH) to 35-40LPH at cruise when I went from the a MkI 40-4 to the MkII 48-4/5. A broken arm & leg have stopped me verifying that is actually the case by flight test vs simply an indication problem or loose crimp.
 
Solving Rotec TBI issues--long

First I would like to thank specially the folks on this thread and the information provided for the Rotec TBI, but specially RocketBob and Tipsynipper who have provided many of the specifics which really helped me. Secondly I thank Doug for this forum, which contains a wealth of information.

As background, I have a Rotec TBI (first generation with the separate fuel regulator) which I installed on my Pitts S1C about 6 years ago. The engine is an O-320, but has 10:1 pistons, so it probably makes about 170HP at 2700 RPM. The Rotec TBI worked out of the box, but after just a few months, and not many hours (one normally never flies a Pitts for long flights), the TBI was running very rich at idle. Adjusting the idle screw did nothing; in fact the engine would still run with the idle screw closed. The TBI was sent back to Rotec and new throttle plate seals were installed, and then it ran fine again?none of the fiddling that I will later describe was necessary. But after less than a year, I was seeing fuel in the tube that connects the TBI with the regulator. This was due to a leaky diaphragm. After a few emails, where I declined to re-rivet the diaphragm, Rotec sent me a new diaphragm (later design),. I posted this information in 2014 in this thread. All was well for quite a few years. I fly this Pitts about 20-30 hours a year.

However, early last year the TBI started running again very rich at idle. Sensing that the throttle plate seals were again the problem, I sent it back to Rotec to get them replaced, which they did for a very economical price for me (this was the good part). However, this time they apparently also replaced the spray bar along with the seals, and maybe too the spring and diaphragm in the regulator. Received the TBI back, and the engine ran great at idle and up to about mid throttle, then would die at anything more than ? to 2/3 throttle. Emailed Rotec, and they told me to drill out the spray bar from the mid point to full throttle with about a 79 drill.

So I did. No real appreciable change in the function, the engine still would not run at full throttle. Wrote back to Rotec, no response for 4 weeks (though this period was during the holidays), and then they only asked for more background of the problem as well as the history of this TBI (which I had already provide to them before, but ?) This information I sent, and have not received any further response from Rotec, including from a second request sent.

But in the meantime, I remembered reading about other folks on this forum that have had problems with the Rotec TBI, and re-reading those threads I found the information I needed. First job was to further drill out the spray bar (only the part between approximately ? throttle and full throttle) and second was to adjust the spring tension on the regulator valve. While in hindsight I probably should have checked the regulator spring first, I drilled out the holes in the spray bar with a #77 drill, not all in the 4 row section at WOT, which had some, but marginal help (the engine could be made to run at full throttle if you advanced the throttle very slowly, but it still seemed to run a bit rough). Then I checked the regulator spring, which had exactly the problem noted in prior posts?it was too long and provided too much tension against the valve, which would cause excessive leaning at high throttle settings. Adjusting that by cutting it down to the size recommended (between .59? and .67?) solved the problem and the engine now runs as it used to.

I don?t know why my TBI ran for so many years without trouble, then started to run lean because of the regulator setting and spray bar. But I suspect both were changed during the overhaul, causing the problems I had. I do understand why people don?t like the Rotec TBI, and having to do adjustments such as can be required with these TBIs without guidance from the manufacturer is bad. But when they work, they do work well.

Again thanks to all for the information and help!
 
Thank you for keeping us updated. I have a newer rotec TBI and have many of the same issues. It runs fine except at full power I have engine stumbles from not enough fuel flow from the spray bar. I've enlarged a few holes and it seems to help. reading through this thread has helped alot.

It seems like a well made device, but it sure would be nice if it just worked out of the box. It seems like the TBI needs to be "tuned" to each individual engine.



I recommend a phone call using the Toll free US number if you need help, Paul is helpful on the phone. They are just very bad at answering emails for some reason. If you need technical help you really need to talk to them on the phone anyway, email is a very slow way to resolve technical issues.


They also highly recommend an oxygen sensor in the exhaust to help tune the TBI and ensure you are running the proper fuel mixture. Its somewhat invasive because you have to drill a hole in the exhaust and route a wires to the cockpit, just like you would installing any other instrument. The problem is these only last a short time if you are burning Avgas.
 
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Buy an Ellison!

Further to all my posts on the problems with Rotec and their TBIs, I fitted an Ellison, and have forgotten it......since I set it up the engine mixture at idle and WOT has been consistent and reliable.
Anyone flying with a Rotec TBI are playing Russian Roulette...it's a loaded gun. The last time I flew behind a Rotec (the 3rd unit they had provided, a Mk2) I had an engine failure at !000' AGL in the climb out. I can assure you that engine failures are not good fun. I was fortunate in that I made the 'strip and walked away with no damage or injuries.
The Ellison may be expensive in comparison to the Rotec, but what price your neck, or indeed the pride and joy you are flying?
Ellison know what they have fitted to the TBI, when it was fitted, and by whom, Rotec have not got a clue what they sold you. You can email Ellison with a information request with your serial number, and they will give you the whole history of the unit from their side.
I have no grudge against Rotec, other than the fact that they sold me a dangerous piece of equipment, and then tried to screw me over when I sent it back.
Just my personal experience.
 
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