Rotec Engineering TBI ?
 

Whilst Looking at alternatives to carburettors and FI on Lycoming 320 engines I came across the Rotec TBI.
Has anyone used the TBI 40-4?
It appears to be the only one which is approved for mogas (which has great appeal to me). Not to mention that it looks beautifully engineered.

For those who have gone before the pros and cons of TBI operations and installation would be useful. Thanks.

I'm interested in this as well, i'd be considering it for an RV-6 though... Also an O-320. E2D, if it matters.

Try searching on "Rotec TBI". At least one RV builder was installing it when they first made this announcement last year.

Not much has been said about it since.

I have one....
 

I have been flying too much to take the time to install it. Probably next annual.

RocketBob has one for his -6 and is further along on the install. Maybe he will chime in.

FWIW
a pal put one on his O-320 powered Swick Taylorcraft. We took my RV-4 FAB and copied it for the install. He LOVES the thing. Gets way better fuel economy than the pressure carb that came off the airplane. Idles better, and runs better.
Really neat design. Uses nylon gaskets for the slide, and the fuel metering is done with a really unique and incredibly simple design. I'm going to put one on the four as soon as the marvel dribbler needs a rebuild...

Rotec TBI
 

Dennis, thanks for the input, it does sound promising!
You have answered one of the questions I've posted to Rotec regarding the use of the Vans FAB. No rush, but if there is any chance of a photo of the FAB modification/installation it would be a useful reference.
More importantly having seen one do you think there will be any major issues fitting it in/under the -4 standard 0-320 cowls?

Yep, it's unique. Ben Ellison has been building them for over 25 years. Patent ran out. The Rotec is a copy.

http://www.ellison-fluid-systems.com/

Tony

Same principle, but different design (like a V6 vs a straight 6). Rotec TBI is a sliding carb with a totally separate fuel pressure regulator that when used together makes up a complete single point fuel injection or TBI. It is a simpler design than the Ellison.

Besides, at less than half the price, and can run on mogas and manufactured by an active team using modern manufacturing methods (unlike the stale Ellison), there really is no comparison.

To date, there have been no O-320 PIREPS posted on VAF. So how can you say there's no comparison? Google can't find any either.

Tony

Tony,
My understanding is that it is a lot like Ellisons design, but improves a few key areas with some materials that didn't exist when Ellison designed his. I'm relying on my pals explanation here, be cause he has owned both, but I've only seen the Rotec.

D

I'll see what I can come up with as far as pictures.
When I measured it, I figured I would only need a one half inch spacer between the oil pan and the rotec, and everything would hook right up...
Thats the guess anyway... <BG>

DM

I'd be curious to know how this is a simpler design - the Ellison is already very simple. The basic principle looks to be identical in both, down to the pattern of holes in metering tube. The Ellison is one piece, which seems simpler than having to mount the diaphram assembly separately. However, the Rotec clearly wins on price (perhaps reflecting lower development costs) and on being able to handle mogas.

Something that hasn't been mentioned yet is that the Ellison is known for being sensitive to inlet geometry. Presumably the Rotec will have similar issues, since it apparently works the same way?

Got the cable brackets and spacer made, but have hesitated to put it on since I could not get adequate test time this winter before making a few long trips in the RV. I just got back from SNF so I've got no more excuses...:) Its hard sometimes to start modifying a perfectly good flying RV that runs like a watch. The other side of it is I want to make a few more 'before' test flights to validate the data I've already captured in order to properly validate my testing with the Rotec. Stay tuned.

Install Pics
 

planning to use one in my RV-4
 

I'm planning to use the Rotec TBI on a O-360 in an RV-4. Will order engine and TBI later this year. I've been in short contact with Paul Chernikeeff from Rotec. He told me that they primarely developped the TBI on their on, because they needed them for their radial engines and that Ellison had to struggle for supply and was rather expensive.
For instance it seems that it will fullfill my needs: aerobatic, mogas, simple ...altough I've never seen one installed on an O-360.

Rotec "injector"
 

Looks to me to be the same technology that Ellison uses. Pressure diaphragm housing is integral to the casting on the Ellison, and separate on the Rotec. I hesitate to refer to it as "fuel injection" Rotating the metering tube into the venturi airstream meters the fuel. It's a slide carb. Looks like it could be a winner though, and I would love to see someone try to install one on a forward facing sump.
Regards,
Chris

Looking closer, the main functional difference seems to be that the the Rotec uses the pressure drop at spray bar to meter fuel:

http://www.rotecradialengines.com/TB...owTBIworks.pdf

In contrast the Ellison uses a separate pressure monitoring tube in the inlet throat. Not sure what difference this makes in how much fuel is metered. The geometry of the inlet, spray bar, and slide appear to be identical.

I have to agree, they are very similar. It is not a slide carb. The pressure regulator, or rather the modulated constant flowrate device makes all the difference. The same principle is used in ordinary fuel injections, but the mixture is very different. These TBIs use the metering bar to adjust the mixture as well as the main fuel flow by connecting it with the constant flowrate device, very elegant.

It is just different ways of obtaining the differential pressure between "static" and total. It is not really static since the main point is to vary this by adjusting mixture. The Ellison patent can be found here:
http://www.freepatentsonline.com/4524034.pdf

Look at fig. 14 and the following for different layouts.

The Rotec TBI sort of assumes that the total pressure is whatever pressure is inside the cowl (like fig 14 in Ellison patent). This is probably good enough in most cases, but I wonder what happens when flying without a cowl ?

Thanks, Figure 14 does help a lot. The Rotec design does appear to be slightly simpler than the Ellison in that it doesn't use a separate pressure sensing tube in the inlet throat (not sure if this is better or not). It also seems clear that both variants were fully described in the Ellison patent (now expired).

As noted by Rotec, the basic principle is a lot like a diaphram-type diving regulator? (except for mixture adjustment).

With a separate (from the cowl) ram air to the engine, and adjustable cowl flaps, I doubt the Rotec TBI will function properly. I think in those cases you would need a separate sensing tube installed directly upstream the TBI like the Ellison. The ellison is not perfect either, one single tube is not good enough. According to common engineering practice, 4 tubes shall be installed separated 90 degree and leading to a plenum, to nullify as much as possible skewed inlet profiles. Common in most fuel injections. Maybe it doesn't matter, maybe the meetering bar needs a good velocity profile in any case?

Airflow Performance FI is also approved for mogas.

I asked why the metering tube is not there when I bought the two I have and they told me they tried it and found it made no difference in operation.

It's really a carburetor with no float
 

Technically, the Rotec and the Ellison are not injectors. This is because the fuel is discharged into the air stream at a pressure below the ambient static pressure. The fuel in the discharge tube is slightly below the static pressure entering the throttle body. The fuel pressure regulator is what we call a negative head flow demand regulator. That is it controls the down stream pressure and sets the fuel pressure to the discharge tube slightly below ambient pressure. As air flows over the metering tube the air is sped up lowering the pressure at the discharge holes, ?sucking? the fuel out. As the discharge tube holes are rotated toward the incoming air stream the air pressure at the discharge holes on the tube approaches static pressure so the fuel will not flow out. Since the metering head across the discharge tubes is so low the fuel metering is sensitive to inlet conditions like ram scoops and turbulence. In theory this ?carburetor? operates like a chain saw carb. No float, operates in any position, except it uses a flat slide with a discharge tube with holes at are exposed as the slide opens instead of a tapered metering that changes the area of the discharge nozzle as the slide opens. And of course the fuel distribution is at the mercy of the intake manifold design. There is no way to adjust for rich or lean cylinders because of uneven fuel distribution. Also because there is fuel being discharge in the vicinity of the slide and evaporating, there is a possibility of carburetor icing.

If this device were truly an injector, the fuel would be discharged with a fuel pressure higher than ambient pressure and discharged behind the throttle, more like a PS-5 pressure carburetor.


Don

Maybe the pressure in the venturi is so low compared to any variations in total pressure that is doesn't really matter.

That's a good question, but it may not matter... There are many Rotec radials running without cowls.

This is the clearest explanation I've heard yet for why the Ellison-type carbs are sensitive to inlet conditions, thanks. The appeal of these units, at least to me, is simplicity of installation - no high pressure fuel system, no injector lines, no return lines, etc. On the other hand I wouldn't expect it to perform the same as a true injection system.

Throttle and Mixture cable position?
 

Thank you all for your views and info.

Rocketbob, have you installed both of yours yet? Pictures would be useful when you have time (certainly no rush).
Thinking about Mixture and Throttle cable routings are these both on the same side of the TBI as delivered in the standard configuration, if not, could they be re-positioned?

TBI or not TBI, that is the question...
 

Andy,

Three years ago I helped my late friend Arvil complete my Dad's RV-6H (hybrid) with an Ellison TBI equipped 0-320. My only performance comparison was with my RV-4, flown for nearly 13 years with a Carb-equipped 0-320. The Carb-RV4 had very few worries including 10 years and 1000 hours running Mo-Gas prior to installing a newer 0-320.
I purchased the Ellison TBI off the classifieds on this site five years ago, removed running from an RV4 and included the Van's FAB. Initial testing showed the little RV-6H to be a lightweight prize fighter with very smooth running and much more leaning capability than the MS Carb. The only difficulty was setting the low idle. I finally called ETBI INC. and talked with them and they patiently went over the procedure
with me. Once set, the ETBI starts very easily hot or cold, even without a primer or accelerator pump. Throttle response is quick, so I installed a vernier throttle control which helped. So far, I have 25 hours on the -6 and like it, light, responsive and smooth in aerobatics with the MT FP prop and ETBI. In hammerheads my RV4 would sputter and quit, not so with the ETBI, excellent in aerobatics.

If the Rotec works anywhere near as well, it would be a home run setup on any RV, especially for the price.

Smokey
HR2

Rotec TBI
 

Smokey,
As always thanks for the input. I do think the overall package of 0-320, dual Pmag's and Rotec TBI would be a good all round package. If only MT would support their Fixed Pitch propellers with engines equipped with dual EI we would all be home free!

I believe Jim Ayres is looking into the problem with Bart at AeroSport power so a solution may be on the horizon.

Huh?
 

Andy,
What does this mean?

"If only MT would support their Fixed Pitch propellers with engines equipped with dual EI we would all be home free!

I believe Jim Ayres is looking into the problem with Bart at AeroSport power so a solution may be on the horizon."

I just reviewed all of the paperwork that came with my wood/composite MT fixed pitch and the only operating limitation I see is overspeed. Please clarify.

MT Fixed Pitch Propellers and Dual EI?
 

Hi Brian,
Whilst getting my plans for engine and Propeller packages sorted out for my -4 I was informed by MT that they would no longer sell their FP propellers to users of dual ignition, apparently due to warranty issues!
I spoke to Jim Ayres who kindly took up the problem as an interface with MT.

These are the two responses from MT :-

" in general we sold for the standard engine our 2 bladed wooden fixed pitch prop with diameter of 170cm, type: MT 170 R 185-3E.
As you have dual electonic ignition we will not use the fixed pitch prop as we had some trouble with a customer in the past.
If you like to go with electric constant speed propeller we would be able to offer you a prop, our MTV-18-C/180-57.

Sorry for the negative answer and we hope on your understanding.
Any further question please let us know."




"we sold so far only to the standard engines without dual electronic
ignition, at least that is what we got as information.
We had one customer who clear told us that he has such installation and we
tried the prop. Result was that we returned money and he bought Sensenich
prop. We tried it but it has not worked out.

If it was a problem only with his installation I can't say but we simply do
not want to upset you or others and therefore engineering decided not to
sell to dual electronic ignition.

I will copy engineeering again and we will see if they have different idea
but for now I must clear say not possible.

The electric constant speed prop will give you best performance from take
off till cruise and in case you do some acrobatics you could switch control
unit to manual mode and have a kind of fixed pitch with certain pitch.

Keep you informed


MT-Propeller Entwicklung GmbH
Eric Greindl"

With the advances in recent years of EI I cannot believe that I would be the only 0-320 user looking to use Dual EI (Pmag) AND an MT natural composite FP propeller. For me it would be the ideal partnership!

I hope this throws some light on question.Perhaps Jim will chime in with an update.

resuscitating an old thread...

Outta curiosity, anyone successfully operating one of them Rotec TBI on say a Lyco 360, experiences?

I have done it successfully. They will reward you with excellent fuel distribution and lower fuel burn but it took quite an effort in engineering and experimentation to get it to work.

I also have one on a O-360, I also had to make some changes with thanks to rocketbob for the help. My previous threads:

https://vansairforce.net/community/s...d.php?t=153150

https://vansairforce.net/community/s...d.php?t=163055

Once I had it set up it has run great. Smooth, can lean till the engine stops without ever being significantly rough. Also works just fine upside down, which is what I got it for.

TBI
 

I have both an Ellison and a Rotec TBI. I may sell the Ellison or trade some parts. I haven’t attempted the install yet but have installed one on a smaller continental engine. Not terribly difficult but if you need Paul C. For anything, expect delays.
I believe both are excellent units.

Are these units a fairly straight drop-in replacement for a carb or would airbox and cowl modifications typically be required?

bifft & rocketbob thanks for the short feedback and above all the links!
Plentiful info in those, thanks for all the experimenting you did Bob :cool:

Had been wondering for sometime as to why those TBI were not more popular. Some good answers found in the threads...

PS
My initial use of the search engine was not good enough...

ELLISON TBI
 

To Flyboyedwards

''I have both an Ellison''

Which model do you have or will it fit an 0-320 Lycoming 160hp.

If you decide to sell it or parts of it, I will be interested as a spare....

Thanks

Bruno
rv4@videotron.ca

Still wondering in this. I may need to change carbs and for the price the rotec is an attractive option.