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ROTEC TBI

RV-4

Well Known Member
Hello Gents

A friend asked me what I thought of the Rotec TBI (Throthle Body ) because I have a TBI ( Ellison ) in my RV-4 but as I don't have any first hand experience with then, I thought I will check the knowledge of the folks here who may have feedbacks on them..

His will be installed on a Continental C-85 (Small engine )

Thank you for your imputs

Bruno
[email protected]
 
I too am most likely going to get a Rotec throttle body and would love to here some experiences. I like that the regulator is now built into the throttle body, just don't know why they don't have a cable bracket for the purge valve.
 
Rotec

I don't have experience with the smaller units but I have a 48-4/5 MK1 on my O-360 powered 7. My only issue is that it runs a little lean at WO throttle. I have just received a new spray bar which Paul told me is a "richer" unit with larger holes which should solve the problem. Haven't had a chance to test it yet. Cold starts are great. Hot starts took a little bit of trial and error to figure out but not a big deal. They now tell you to install a return line back to the tank to eliminate this issue. I just turn off the boost pump and fuel valve 10 secs prior to shutdown. Fuel valve and pump back on for hot start with throttle cracked and running after a couple blades. I installed mine in line with the crank. They now say it is better to install 90 degrees to the crank. Except for the lean issue it seems to be working fine for the 100 hrs I have on it. Install an isolator between the TBI and the sump to reduce heat transfer. I used 1/4" thick phenolic. Some people use a flow straightener at the inlet. I did not, but I did put a flat piece of .032 aluminum about 5" long in front of the air filter at the inlet to duct the air to the outside of the air box in order to minimize ram effect from the Vans cowl. The engine runs very smooth and idles down to below 500 rpm.
I am at SunNFun and spoke to Paul about my lean issue. He explained about the spray bar and said they don't have much experience with the larger engines but they have lots with the smaller ones.
I have always received replies to my emails from Paul although not always very timely...sometimes a week or more for a reply with not as much detail as I would like.
All in all I am happy with the unit so far and would have no issue putting one on another engine.

One thing I forgot to mention...due to the shorter height of the TBI vs the Marvel carb, I made a plenum style adapter about 6" diameter and 1.5"thick to keep the same height so mods weren't required to the FAB. This is probably another reason why I don't require a flow straightener.
Al
 
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Thank you AL for the nice write up.

I will forward the info to my friend (also at Sun & Fun ) and I'm sure he will appreciate it.

Cheers

Bruno
 
I have a Mk II Rotec TBI 48-4/5 on my OX-340, having replaced the MK I TBI-40/4.

The only thing I found was the separate regulator (Mk I version) was somewhat prone to vapour lock during a hot Australian summer, and the integral regulator of the Mk II version seems somewhat more tolerant of the heat.

Starting cold is dead simple with the primer button, lighting off in less than a half-dozen blades with the PMags, and you wouldn't even get past one blade when the engine is warm. It will not lean-cut at idle, so I switch off the ignition to shutdown.

As RV7 To Go has already mentioned, it is shorter in height than a standard carb, so your snout won't line up with the FAB. I bodged up a new glass FAB to make up some of the difference and its' worked for 100 hours so far.

The only other 'issue' which isn't really a problem, is the mixture arm is perpendicular to the centerline of the aircraft, so you need to fashion a bellcrank of some description for your mixture cable attachment.
 
KRviator

Thank you for the info, I will pass it on to him..

His is to be installed in a Cessna 140 (Owner Maintenance) which is like a Homebuild in Canada.

Bruno
 
Vapor return line

If installing a Rotec TBI you should consider installing a vapor return line. Feel free to pm me for more details.
 
I would not recommend the Rotec TBI. All I had was grief with poorly machined, poorly assembled units, having been the first to get one onto the LAA UK fleet. My experience with these units finished with an engine failure at 1000' in the climb out on the second flight with a Mk2 unit. The fuel pressure regulator had been assembled badly.
The support I had from Rotec was shocking. At no time was I rude or impatient with them, I was very supportive, and was trying to get the TBI accepted by the LAA (I am a LAA engineer). Eventually they said to send both my Mk1 & 2 units for a full refund, and upon receiving them offered me 50%.
The Rotec is a poor copy of the Ellison (which is back in production, more expensive, but a long reliable history, "fit and forget") but uses different materials for the soft components. The spray bar seals will wear prematurely and leak unmetered fuel at idle, so eventually you won't be able to lean off the idle mixture enough.
They may look lovely, but that IMHO is where the good bit ends. Trawl the forums to see who else has had issues with Rotec.
I purchased a second had Ellison, before I did so I gave Ellison the TBI serial #, they checked their records and told me all about the unit, date of build, mod' state, last overhaul......you won't get that with Rotec, they don't keep records of any of their units. After setting up the Ellison I have not had one issue with it....every flight with the Rotec gave me a headache.
See: http://www.vansairforce.com/community/showthread.php?t=114648&highlight=rotec&page=13

We take for granted the engine will operate at all times, I was very fortunate that I could land back on the airfield when my engine stopped....I can assure you it knocked my confidence in light aircraft. Is it worth saving a few $$s on a product which is so unreliable? Your decision.

Neil
 
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