Rotec TBI MK2 Advice for Aerovee

[DBrown]

I bought a Rotec TBI @ OSH a couple weeks ago and I am looking for some input from those of you that have installed one on an aerovee

Did you install carb heat?

Have you gotten carb ice with it?

did you install a Fuel pump? or was gravity enough?

What did you do for the intake flange adapter & air filter?

What kind of primer setup?

I was under the impression (told by Rotec) that this would be a relatively simple swap by changing the throttle cable & installing a primer lever.
but if I have to build a Intake adapter, add carb heat, a fuel pump, return line, a primer control, swap control cables & throttle quadrant, I may just stick with the little red slider for now.

I've scoured the forums and the Google for a couple days and haven't come up with much conclusive data, or many examples of MK2 TBI Aerovee installs.

And advice and pictures would be appreciated, I'm trying to get more input & ideas before I start making parts.

Thanks in advance

[Arjay]

Fred installed the Rotec on our legacy Sonex, with aerovee, last year. No carb heat. Never had icing. If you have ice, you can shake/scrape it off using the throttle back and forth. (look at how the throttle works in the tbi. It's like a scraper). No air cleaner. (a little dust never hurt anyone, and we don't get a lot here in the southland). No fuel pump. Gravity is enough. We had to custom make new throttle and primer linkages. That was a big job. We did run a small gas vapor return line back to a tee on top of the fuel filler and rerouted the fuel vent line down to outlet out the bottom. This replaced the stock fuel vent that was sticking up facing forward from the top. Since then we have had no "burp" issues. Although we have not yet tried serious aerobatics, we have tried high g turns and it seems to run just fine throughout.

One problem that stumped us for a while was that we couldn't get it to run consistently when first installed. Turns out the diaphragm in the pressure regulator did not have a proper vent hole in it for ambient air. This was a bugger to find. Had to tear it all apart and figure that one out. Apparently, it was due to an assembly error (the wrong diaphragm installed). We fixed it by drilling the correct hole in the diaphragm. I suggest you check yours before installing it. So much easier that way.

I don't know how to post pictures, so none here.

Ron, legacy Sonex td with aerovee, here in North GA

[DBrown]

Thanks for the input Arjay, I appreciate it

I didn't know anything about a regulator vent hole? This is the first I've heard of it. I don't see anything in the instruction manual.

I spoke to Rotec over the weekend and they confirmed that you pretty much have to build an intake adapter He also sent pics of one he builds out of fiberglass & he said most people do a scat hose adapter to a remote filter. Seems easy enough but the instruction manual says (uses standard 4 bolt aviation flange for easy installation) They must be talking about the other carb's with flanges on both sides because I have looked everywhere! Automotive, aviation, diesel, go carts, McMaster Carr & nothing off the shelf fits this flange. The fact that they make their own from fiberglass confirms to me that they are not a standard size.

Why they don't offer any way to attach a standard air filter or a scat hose or anything to this TBI is just mind boggling to me! (or throttle & primer brackets) They obviously have the CNC mills, I built an adapter cad/cam file in Fusion 360 in 10 minutes....why would they not do this? Why is the manufacturer making these out of fiberglass? makes zero logical sense to me.
(sorry rant over)

As a hobby machinist; making the Flange, & brackets for throttle & primer should be a non issue, It's just more time and hassle than I was expecting. I was hoping for a quick install but I guess it's going on the shelf until December when I start the condition inspection. There's too much flying left this summer to tear it apart now.

[Arjay]

The regulator vent hole was supposed to be in the diaphragm of the regulator that is attached to the TBi body to begin with, but it was not there. We had to drill it. There is nothing in the instructions about it because the absence of the hole was a manufacturing defect in assembling the TBI, not a normal condition. (I assume the diaphragm model without the hole was used on prior regulator models, possibly used in the older regulator model that was separate from the TBI. I assume during assembly of our TBI in the Rotec factory the assembler installed the wrong diaphragm for that model TBI. They are the same except for the hole).

As I recall we had to acquire an adaptor flange from somewhere other than Rotec to get the TBI to mate up to the intake manifold.

Yes, it was all more of a hassle than we expected also. Hopefully, it will all be worth it in time.

Ron

[BRS]

This talk of the MK2 is peaking my interest.
How much different does the Aerovee run with the MK2?
Is the MK2 much taller (wider?) than the AeroInjector?

[Arjay]

Brock:
Our engine runs smoother and gets maybe 100 more static rpm (3250 at wot for takeoff). Also, where the aerocarb would not allow aerobatics on our bird, the Rotec will (supposedly-we haven’t tried it fully, yet). A major difference is that the mixture control will not cut off the engine at idle. Another major difference is that the Rotec has a primer, which is a great safety factor, as it can help keep the engine running if something else goes bad in the tbi.

I think the Rotec is a little larger than the aerocarb, but still easily fit our engine.

Good luck with it. Please let us know how it works out.

Ron

[Bryan Cotton]

For what it's worth, I'm one of the several/many people doing aerobatics with the Aerocarb. No issues but I do need to lean it before pulling significant Gs. If I don't, it bogs down but recovers afterwards.

That static RPM sounds great!

[DBrown]

The only reason I am eventually going to the Rotec is for aerobatics, I'm not knocking the Aeroinjector, once I got it set up and tuned properly it does fine, 3150 static, runs smooth at idle (once warm) and no burping (after installing a burp tube) but while doing aerobatic testing it's made me pucker more than a few times and turned off in spins twice. I agree with Bryan that leaning it out helps, but for me it still coughs quite a bit under minimal G loads.

If I wasn't doing Acro, I would just keep the Aeroinjector.

I have built a bracket that incorporates the throttle and primer in one piece, I'm going to have the flange I made in Fusion 360 cut by a local CNC shop to fit a standard 3" SCAT hose for a remote K&N filter. and install it all in November when doing the condition inspection

I appreciate all the input!

[Bryan Cotton]

Interesting. It did take me a while to figure out how to keep the Aerocarb happy when doing acro:
1) don't go to idle in spins
2) before a loop, lean aggressively - pull back until it stumbles and go just a little richer

But otherwise I am happy with its acro performance.

[BRS]

Here is another MK2 question.

I'm trying to even out my CHT's, the right two (cyls 3&4) always run warmer. It's common for me to see 80 deg difference between #1 & #4. Though I still manage to keep #4 at around 380 deg. Since the CHT's corespond to higher EGT's it's looking like uneven fuel distribution on the R2300 & AeroInjector.

Q. Has anyone noticed more even fuel distribution (even EGT's) after going to the MK2?