Rotec TBI issues

[UH1CW2]

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!

[deej]

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.

[1flyingyogi]

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?

[KRviator]

Originally Posted by 1flyingyogi

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.

[pitts flyer]

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!

[Robin8er]

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.

[TIPSYNIPPER]

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.