Rotec MKII TBI
Posted: Wed May 13, 2015 5:30 am
by NARROBB
Hello,
I got the MKII coming on the way, been getting ready to install it on a Jabiru 3300A replacing Bing 64, my understanding its direct replacement but some head scratching needs to be done for the throttle/prime/mixture cabling/routing.
Anyone installed Rotec MKII TBI on a Jab 3300? Any info and photos would help a lot.
Regarding the Prime on the Rotec TBI, i read somewhere someone used a solenoid to press the prime rather than cable and associated design, any tips or pointers on that subject will be great.
Cheers
NAR
Re: Rotec MKII TBI
Posted: Wed May 13, 2015 6:58 am
by Brett
Sounds like a good idea re the elec solenoid idea. I have a mark 1 on my aerovee and installed a cable however. The only thing I guess to consider is the fact that if you do have an issue, and the regulator fails, it will probably fail with no fuel flowing and the primer is there also to get you home by over riding it as a fail safe. If an electric solenoid was used I suggest you get one that can stay energised for a long period not just a short on off type. I have often thought I need to change my cable to one that will stay out like a mixture cable. The one I have is just a normal pull cable with no hold feature. The thought of having to hold the cable out for the whole trip home if there was a problem leaves me a little nervous. Probably unlikely but I guess could happen. Just thinking about this now as I type, I wonder if the diaphragm has a life span or change out period in hours or years as part of a service schedule.
Re: Rotec MKII TBI
Posted: Wed May 13, 2015 5:11 pm
by NARROBB
Thank you Brett. Can’t you use the Choke type pull where you can rotate it to lock (pulled) in place without strain when you need to? Like this one http://1drv.ms/1Jeta5L
Post some photos of your cable setup for the primer if you don’t mind. If i can’t find a solenoid, going to have to use the cable!
Re: Rotec MKII TBI
Posted: Thu May 14, 2015 8:23 am
by Brett
I possibly could use that type of cable. Worth a look into 
Next time I have the cowls off the plane, I will take a photo and post it up , no worries.
Re: Rotec MKII TBI
Posted: Thu May 14, 2015 10:48 am
by SonexN76ET
I am wondering if there has ever been a case where the regulator on a Rotec TBI failed and someone had to keep the primer depressed to keep the engine going? Will the engine run OK with the primer depressed for an extended period? In the Rotec literature they mention pressing the primer button a few times to clear out vapor lock if it were to occur. From what I understand, when you press the primer button it really let’s the fuel pour out. Can the engine run with that much fuel being released? I just fabricated my primer lever and A920 throttle cable attachment for my Rotec MkII TBI and am trying to decide on a cable setup for the primer. I am also going to put a spring on the primer level to pull the lever off the primer button when not purposely depressed.
Jake
Re: Rotec MKII TBI
Posted: Thu May 14, 2015 3:34 pm
by WaiexN143NM
Hi jake,
First just want to say that we are extremely pleased with our rotec tbi mk 1 on our jab 3300 . Just a reminder when u prime make sure throttle is opened up full to expose the spray bar with all the holes, otherwise priming does nothing. Install instructions from rotec require a carb heat install, although many have done without like the aerocarb/aero injector. Can u get carb ice in a throttle body? That is a whole nother thread and discussion. We ordered the carb heat box and flow grid from aircraft spruce for the Ellison throttle body. The heat box was way too big to fit between the motor mount tubes so we made a smaller version of it and sent back to spruce. We did incorporate the flow grid piece, about $100 . Never tried without it , but hope it’s doing its job. Heat muffs that work and are small in size to fit the jab3300 exhaust you can get from wicks or spruce is the ‘cessna’ style. I believe u have the aerovee so u have more room on the exhaust pipes for bigger muffs. We have 2 , one for carb heat, one for cabin heat. We have never tried pulling the primer when in flight, need to try that , see how it affects the engine. Again the more open the throttle is the more of the spray bar is exposed, when priming.
Thanks for the input on the fuel tank fittings. It’s been a hot topic. One of the good topics amongst the builders/pilots on the flight line at Rio Linda fly in. When following the instruction via the sonex oops fittings , and after the drilling is done, how much plastic build up inside is still left? Any body else please feel free to chime in with thoughts, experiences, suggestions for the tank fittings
Cheers!!
WaiexN143NM
Michael Radtke
Re: Rotec MKII TBI
Posted: Thu May 14, 2015 3:58 pm
by Waiex 49
Hi Mike,
It was good to see you at Rio Linda.
Regarding the amount of plastic that surrounds the fittings and remains after the drilling, in my case it was substantial. All of it had to be removed so that the o-rings had a flat surface to form a seal.
If you want to get an idea of how much plastic surrounds the tank fittings, remove your fuel cap and reach in with your fingers and feel around the backside of the fuel vent fitting. The fittings extend beyond the thickness of the tank wall and a considerable amount of plastic forms around the fitting.
The Sonex instructions call this a “ridge” but it is more like a little mountain of plastic. It all has to be removed to provide a smooth surface for the o-rings. I found this to be one of the more challenging aspects of installing the “oops” fittings.
Re: Rotec MKII TBI
Posted: Mon May 25, 2015 1:53 am
by nwyooper
I have a MKII Rotec TBI on my AeroVee. If anyone wants to see my mechanical primer, send me an email and I will send pics.
Loren
nwyooper@yahoo.com
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 1:45 pm
by 142YX
Anyone have any photos of their Rotec TBI control cable setups?
I received a new MKII in the mail yesterday.. and it appears as if one must use a heavy duty push-pull cable similar to these:
https://www.aircraftspruce.com/catalog/ … ckkey=8714
for the throttle control. Was curious what other people have ended up using
Thanks!
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 6:39 pm
by fastj22
142YX wrote:Anyone have any photos of their Rotec TBI control cable setups?
I received a new MKII in the mail yesterday.. and it appears as if one must use a heavy duty push-pull cable similar to these:
https://www.aircraftspruce.com/catalog/ … ckkey=8714
for the throttle control. Was curious what other people have ended up using
Thanks!
I think I’m getting mine next week too. I was thinking the same thing and attaching it to the top hole on the AeroConversions throttle quadrant.
Also thinking of using a longer coupling hose to move the carb away from the engine hoping for better atomization. My #6 always runs leaner. Any thoughts on that? Maybe a 45 or 90 degree bend using a silicon hose like this…
http://www.summitracing.com/parts/vpe-2740b/overview/
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 9:23 pm
by SonexN76ET
I have posted a few pictures below to help those who may be installing a Rotec TBI Mk2. I CAN NOT YET ENDORSE this product because I have not done enough testing of it yet. Rotec’s directions are not as good as those of the AeroInjector. The AeroInjector technical support from Sonex is far superior.
Here is a picture from the front looking to the back of my Rotec TBI MK II. It shows both the mixture and the throttle cables. This picture shows the throttle with a cable from Aircraft Spruce which was not strong enough. I have replaced it with one from Steinjager that has a tough plastic outerwall over the metal cable sleeve. The throttle on the Rotec TBI MkII is extremely stiff. Rotec claims it will improve (get less stiff) with time.
And here is from the front looking at the mixture cable:
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 9:31 pm
by SonexN76ET
Here is a view from the side. The fuel line has an AN4 fuel/vapor return line on a T fitting along with the 6AN fuel line. I have a Facet fuel pump. The Rotec TBI will run without the pump on but you have to have at least two gallons in the tank to create sufficient fuel pressure without the pump on.
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 9:35 pm
by SonexN76ET
Here is a picture of the primer lever and the mount for the push pull cable for the throttle.
Jake
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 11:07 pm
by fastj22
Jake,
No air filter?
Re: Rotec MKII TBI
Posted: Sun Sep 06, 2015 11:12 pm
by SonexN76ET
I have not included pictures of the air filter in these series of photos. I can take some photos with my air straightener, air filter, carb heat, and induction plenum installed later in the week.
Re: Rotec MKII TBI
Posted: Fri Sep 11, 2015 6:49 pm
by SonexN76ET
Here is a picture of my Rotec installation with the air cleaner and the intake plenum. Carb heat comes in on the other side of the plenum. There is a flap that cuts out the ram air when you apply carb heat. The filter is a larger size K&N. It is E-3221.
I still have not completed my testing.
Some initial observations:The AeroInjector has better instructions. The tech support from Sonex is far superior in my experience. I also believe that Rotec made the tolerances too tight on the MKII TBI which make the throttle extremely stiff.
The keys to tuning the Rotec TBI are to have smooth incoming airflow, setting the idle mixture screw, setting a mechanical throttle stop at the appropriate setting, and setting full rich stops on the cockpit mixture control (mine will not run at the full rich setting at full throttle and required installing a stop.
Jake
Re: Rotec MKII TBI
Posted: Fri Sep 11, 2015 8:57 pm
by lpaaruule
Hi Jake,
A friend of mine with a Zodiac 601 couldn’t get his Jabiru 3300 with Rotec TBI to run at full throttle, and initially put in a throttle stop. We ended up enlarging many of the holes in the spray bar from 0.3mm to 0.35mm (IIRC) with a small drill in a pin vice. Now his engine runs great at full throttle. We determined he was running way to lean at full throttle because his fuel flow was only 6.5 gal/hour according to his flow meter. Now it’s about 10 gal/hour at full rich. This was a last resort after adjusting the idle mixture screw to no avail.
I have a first gen Rotec TBI that was included with a Jabiru 3300 I bought from another builder. I remembered you commenting that you put an oops fitting on your tank in case you wanted to install a vapor return line. I’m very interested in doing the same thing, but hopefully I won’t need to used an oops fitting. I’m also considering removing the mechanical fuel pump from the engine (per Sonex instructions) and using an electric fuel pump. I’ve heard of the mechanical fuel pump actually heating the fuel because it’s mounted right on the engine. Besides, the plumbing could be simpler that way, and there would be less unpressurized fuel than by opting to used the mechanical fuel pump.
My thought is that I’d mount the fuel pump fuel pump on the firewall right before the gascolator. That way the fuel in the gascolator would be pressurized. I’m also thinking about putting a flow meter between the regulator and the TBI and either insulating it or using a blast tube to cool it. The fuel line upstream of the regulator would have a T-fitting that would have a vapor return line connected to it.
So I sort of have a plan, but I have to figure out which holes on the fuel tank I’m going to need to use, and for what. I’m thinking the top sight glass fitting would be good for the vapor return.
Any suggestions are appreciated.
Paul
BTW, my friend with the Zodiac also had a lot of frustration getting good tech support from Rotec. He politely confronted them about it at Oshkosh this year. He ended up sending all email questions to both tech support, and tech support’s wife. He has received more “timely” responses.
Re: Rotec TBI for sale
Posted: Sat Sep 12, 2015 9:44 am
by wolfpack3
I have a Rotec carb for sale. I’m asking $600.S/H included in the US. It is not a MKII. Excellent condition only used 10 hours. pictures upon request I have decided to go with a float bowl carb instead.
Please PM me if interested.
Re: Rotec MKII TBI
Posted: Sat Sep 12, 2015 1:26 pm
by SonexN76ET
Paul,
If you search this site with the keyword Rotec you will see that most of the people using Rotecs on a Sonex have a Jabiru. Most of the Jabiru users have positive comments about the Rotec TBI. There were very few photos of Rotecs on non turbo Aerovee engines for me to use in my planning.
Tony Spicer is currently building a Panther with a Rotec Mk I TBI on a Jabiru. He has some excellent photos on line of his very professional looking setup. I copied his air straightener which is thin honeycomb aluminum sandwiched between an aluminum frame that mounts on the intake mouth of the TBI.
As far as the fuel pump goes, I mounted mine in the cockpit on the firewall to protect it from heat and to be able to keep an eye on it. I could not figure a way to mount it on the firewall on the engine side. With the Facet fuel pump you are also required to have a fuel filter before the pump. I am still trying to figure out the best way to squeeze one in.
I looked at your builders log, you have a good looking aircraft under construction.
Jake
Re: Rotec MKII TBI
Posted: Mon Sep 14, 2015 6:18 pm
by SonexN76ET
Here is a picture of an air straightener similar to the one I made for my Rotec TBI.
The grid itself is 1/2 inch thick.
A word of caution: One of the other builders has reported that they talked to Rotec about using ram air with a TBI at Oshkosh. He said that Rotec now recommends against using ram air. The Rotec website still references the use of ram air. So, what the Rotec technical support is saying is in conflict with the information on their website.
Ellison Fluid Systems (which the Rotec TBI copied) says that ram air can be used but you have to have a good induction system design for it to work. So please be careful.
Re: Rotec MKII TBI
Posted: Tue Dec 01, 2015 4:37 pm
by 142YX
Finally got the new Rotec TBI MKII installed into 142YX and attempted to fly with no luck. In fact.. the engine quit on me on the takeoff roll approximately 5 MPH before liftoff (thank goodness). I had done a series of engine runs with the following results leading up to the flight attempt:
- Idles strong with no indication of quitting at ~850 RPM
- Able to achieve 2850-2900 RPM static on the ground (prince prop)
- Engine quits at full power when the mixture is pulled out, continues to run with mixture full out when at idle (expected response)
- No hesitation from idle to WOT with moderately fast throttle advance
- Some hesitation when slammed from idle to WOT (however this is documented and expected as there is no accelerator in the TBI)
- Ridiculously rich. Stupidly rich. Insanely rich. At WOT, I was pulling ~18 gph (with trends that look like it was still increasing at the point where i had to pull back for CHT’s), with equally absurd values at mid throttle settings. Idiotically rich fuel burn rates validated through back smokey exhaust, and an independent fuel flow calibration test where i validated the fuel flow transmitter to be within at least 10% of reality.
- ~2-3 GPH burn rate at idle
- Never once quit on me or made me think it was going to quit (unless i was purposely trying to make it quit)
With hindsight being 20/20 - I should have never attempted the flight with fuel flow being that high - that does not make sense. I feel dumb, but hey - I am sharing this so that maybe someone else can learn from it and not repeat the same mistake. The attempted flight went like this: 3-5 second advance to full power, expected response, I noted seeing ~2900 RPM or so with all engine parameters in the green, and then it spontaneously quit somewhere north of 40 MPH IAS.
When I pulled the mixture knob out at WOT, burn rate would diminish slightly.. but it was still much to high (13 GPH) or so before it would become very rough and quit. My thinking in attempting the flight, which was tempered by the frustration of not being able to do anything more than a 10-15 second WOT ground run before reaching CHT limits, was that “so what” if it was running way to rich.. it was running and seemed smooth. Getting to altitude would both keep the engine cool and be more representative of the actual operational condition - and i could feel out the mixture setting there. Didn’t work out that way.
After the attempted flight, my initial thought was that I was over-carburated for my engine. There are notes on Rotec’s website about setting the throttle stop something short of WOT being a normal thing some people have to do. In another engine run done after the fact, I was able to achieve 2900 RPM at 3/4 throttle, opening the throttle even more REDUCED the RPM by ~50-100 or so. So then i re-adjusted my hard stop to that 3/4 position.. but the fuel flow was still 17~18 GPH! Subsequently, I have asked some other people and they have confirmed that they do not reduce the throttle stop at all for their installations on a 3300. I should note that I am running a TBI-40-S (40 mm throat, the recommended model per Rotec for the 3300). Is anyone running the smaller (34" mm) TBI on a 3300?
I would be very curious in hearing from anyone with a TBI on a 3300 the following data points which might help me diagnose if there is something wrong with my TBI or not:
- What size throat are you running?
- What static RPM do you get / with what prop?
- What is your fuel burn rate at WOT and at cruise?
- Do you restrict the throttle to something less than full capability?
- What range of the mixture adjustment do you use?
Any other advice or insights would be welcome!
Right now i have an email out to Rotec.. no response yet but it has only been 2 days. Right now my thought is that there is something wrong with my unit. In the troubleshooting section of the website it states that regulator spring length / size and leaky teflon seals are worth checking for overly rich conditions.. i have yet to do those steps but they are probably next on my list.
Below is a bunch of photos from my setup, as well as an excerpt of the data from the ground run series that i did. The chart here is the response when i was limiting myself to 3/4 throttle.
Thanks!
Re: Rotec MKII TBI
Posted: Tue Dec 01, 2015 8:20 pm
by fastj22
I’ve got about 10 hours on my Rotec TBI now.
I think your idle mix is way too rich. Its unrelated to the mixture adjustment of the spray bar. Its probably dumping extra fuel in.
Mine came a bit too lean and I couldn’t keep it idling. ½ turn rich on the idle adjustment fixed that. Perhaps a bit too rich as I have to lean aggressively on takeoff.
Prince P-tip.
I set mixture about ½ way for takeoff. Anything richer and it runs like crap.
I see 2800 static at runup.
10 GPH on climb out at WOT with EGTs in the 1200s (much more than I saw with the Aerocarb)
I see 5 and 6 going a bit lean at WOT and pulling back throttle a bit brings them even with the others. (over carbing?)
In cruise, I’m seeing around 6GPH with EGTs in the 1300s and RPM at 2800. (about the same as the Aerocarb)
WOT at cruise I will see 3100 RPM (never saw that with the Aerocarb).
I had intended to install a boost fuel pump, but decided to try with just the gravity feed. Its working fine with gravity only.
I did use an air straightner that Tony used. It won’t effect your high fuel use, but will make your EGTs much more even.
https://picasaweb.google.com/tonyboytoo … 7823613170
Overall, I’m pleased with it. EGTs are very even. Throttle and mixture are silky smooth. And I’ve seemed to have gained 200 RPM on climb.
Re: Rotec MKII TBI
Posted: Tue Dec 01, 2015 10:02 pm
by SonexN76ET
The Rotec TBI documentation needs to be more thorough in my opinion.
Here are three things that are not clearly spelled out by Rotec that could be affecting your installation:
-
your engine quitting may be due to you advancing the throttle rapidly on takeoff. It takes a second or two for the fuel to run past the fuel pressure regulator to the spray bar after a quick application of power leaving you without fuel in the spray bar for an instant or two, but sometimes long enough for the engine to quit. This can be prevented by moving the location of where your throttle arm connects with the throttle cable causing you to have to make a longer throttle throw, thus slowing down the speed the throttle opens on the Rotec. Think in terms of gears. I am using a Vans Aircraft RV8 throttle and had to move where my throttle cable connects to a point closer than stock to the pivot point on the throttle arm. Another option is to tell yourself to throttle slowly but what if you forget or you loan your plane to another pilot?
-
you have to put hard stops on your mixture lever that limit the normal range of operation. These are NOT the same as the stops on the body of the Rotec at the mixture arm. My engine will hardly run at full throttle if I go to full rich according to the body stops on the Rotec. My hard stop for full rich is about 1/2 to 2/3rds of full rich. All the Rotec doucumentation says is “your full rich will certainly be less than the full rich position”. This took a lot of trial and error to find the correct range.
-
like John suggested, you need to check your idle mixture separately. It seems as if you are too rich there. Also, look into an air straightener.
Two other things, if your solenoid deploys by accident depressing the primer when you are at full throttle your engine will quit then too. Second, I am concerned about your throttle cable being at an angle to the throttle slide arm on the TBI. Please consider it being in perfect line with the movement of the throttle slide. Sometimes the Rotec throttle gets very stiff and I distorted my cable and it became worthless and had to get a new cable. Also, make sure the cable can not come out of its keeper on the mount you fabricated on the TBI. On the previous page you can see an example of my mount.
On a closing note, it could also be that you just have a defective unit and need to get it replaced.
Please be careful with the Rotec until you get it all figured out.
Jake
Re: Rotec MKII TBI
Posted: Tue Dec 01, 2015 11:32 pm
by WaiexN143NM
Hi Nick,
Sorry to hear you are having some issues with your Rotec TBI . I know u are anxious to get flying again. I was one that highly recommended the Rotec TBI. We love ours. Thanks to John ( I highly encouraged john to get one) and to Jake for input and spot on suggestions. Good eye Jake, I went and looked back at Nick’s pics. First nick u have the right Tbi. The 40-S (spigot mount) . We have a jab 3300 w prince prop. We get 3000 static WOT on the ground . The flows are just like john’s. A couple of things about the pics. First , as jake said , straighten the throttle cable with a longer bracket or rubber adell clamp. Also we drilled 2 holes and safetied wired so the throttle arm cannot come out of the slot. Also the nylon nut holding the clamp u used a longer bolt when u mounted on a/c right? . We have the mark one version , but on the regulator primer we installed a mechanical arm with a cable to the cockpit. Any chance the solenoid u installed is activating and causing extra rich mixture? I suggested to john to try gravity feed only as we have ours. We have never run the tank below approx 5 gal. Below that is there enough head pressure? Don’t know. I posted once to Jake , he was worried about head pressure, also vapor lock. We fly ours in Tucson heat , never had a problem. I believe he also ran a return line to the tank with a electric pump(facet?) hang in there don’t get discouraged. You’ll get it solved. Also not nitpicking anything. I know u work at Scaled and your plane is impeccable. You could teach us all a thing or two. Looking forward to seeing u on the flight line and flying your ‘green’ machine.
WaiexN143NM
Michael Radtke
Re: Rotec MKII TBI
Posted: Tue Dec 01, 2015 11:49 pm
by WaiexN143NM
Also , one more thing Nick, I ordered from aircraft spruce a stainless flow grid, about $100, is for the Ellison TBI , but is sized the same for the Rotec. The carb heat box they also sell for the Ellison was way to big, but used it as a guide to build a smaller one, and sent it back. Carb heat box on a tbi is a whole nother thread. The flow grid keeps the cht/ egt’s even.
WaiexN143NM
Michael Radtke
