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IO-390 Tbolt & Airflow Performance FM-200

jeffw@sc47

Well Known Member
I have had to do modifications to the air intake snorkel to fit to the Airflow Perf throttle body, took a good bit of time but not too difficult.

When I got around to fitting the bottom cowling, that's when things got really difficult. The bottom part of the snorkel at the left side of the bottom cowling's center bulge, under the prop spinner, was contacting the cowling. I made a number of modifications to get the snorkel and cowling to clear so that the cowling could come up to where it properly fit behind the spinner backplate.

As a result, the snorkel ended up getting chocked down too much, and contorted a bit, so that the airflow through it became turbulent to the point where it was pulsating; to the point that it will not work properly and the engine would not run well.

HAS ANYONE! installed the Lycoming IO-390 Tbolt with the Airflow Performance FM-200 fuel injection system on their RV14 and gotten as far as fitting the snorkel to the engine and the cowlings through Page 45-06 instructions?

If no issues and everything went fine - I need to talk to you - PLEASE. I am stumped as to why I am having some big no-fit problems.
 
Works on my -7

That?s the set up I have on my -7.

The fit is close and I carved out the honeycomb and reinforced the glass to gain some additional clearance.

For the snorkel, I cut it in two and fit each end independently... then rejoined the sections in place. Doing this gave the most flexiblity in getting the best clearance from the cowling.

I also cut off the flange of the snorkel at the throttle body and glassed a clean recess to closely slip fit the throttle body keeping the snorkel close to minimize interference.
 
I wish I had a solution...

I'll be at that point before too long. I received a FN-150 versus the 200. Wondering if there is a difference in the dimensions.
 
Recommend you hold off with mods to snorkel right now

I recommend that you hold off a bit with any modification of the snorkel and cowling until I get this partially or wholly figured out; your call. You may not have the same issues I am having as I think that the FM-150 is a throttle body model that is a clone or very similar to the Precision Air (Bendix style) unit.

I am communicating with Van's to see what assistance they can provide. I have checked with another 14A builder who has been flying theirs for around 100 hours - they used the Avstar fuel injection (Bendix style) throttle body and did not need to shorten the snorkel, and it cleared the cowling with some minor sanding on the bottom of the snorkel as well as building up a small area at the filter box area. This need to shorten the snorkel is perplexing as is the need to adjust for clearance to the bottom cowl.

I have checked with Lycoming and they confirm that the oil sump, warn air induction, is identical on the stock 390 and the 390-Tbolt.

The newest possibility suggested is that in the past year or so the vendor supplier of the snorkel may have changed and/or the design of the snorkel that altered the fit and clearances.

I have ordered another snorkel to see if that helps me figure this out.

Stay tuned.
 
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I have the AvStar on mine and I certainly thought I would have to modify it in order to install . I kept playing around with it and pushing (very small amount) it up against the mount bolts and it was a very tight fit around the starter but there was air visible between all parts.
 
9/27/17 Update

In Van's RV-14 kit documentation Section 2-02 it states that the firewall forward kits have been vetted for the Lycoming IO-390-A3B6.

SELECTING AN ENGINE FOR THE RV-14/14A
The RV-14/14A was designed and vetted using the following engines:

Lycoming IO-390-A3B6 Lycoming IO-360-A1D6.

The IO-390 engine is comparatively new and is found almost exclusively in the experimental market. It has not had the need or time to mutate into the bewildering variety of versions that older Lycoming designs have achieved. The version Van's Aircraft sells – the IO-390A3B6 – is configured with a standard Lycoming sump, Bendix-style injection, Slick magnetos and a forward mounted propeller governor.

The RV-14 Powerplant Kit will work well with aircraft engines which are:

- Four-cylinder - Horizontally opposed - Horizontally inducted - Fuel injected - Angle valve - Normally aspirated
- Equipped with a forward mounted propeller governor. See Figure 1.
- Equipped with a standard Lycoming style oil sump.
- Rated between 200-220 horsepower.

Some IO-360s have been removed from aerobatic airplanes and are equipped with different sumps and induction systems.

Van's Aircraft has not investigated the installation of any such engine. It is recommend that builders contemplating installing one of these engines in an RV-14/14A perform serious research before purchasing.

There are several companies building Lycoming “clones” – engines similar to, but not identical to, the Lycoming. These engines can come in almost any configuration the buyer wishes. Van’s Aircraft has not investigated which, if any, of the many available versions might work in the RV-14/14A.
The only engine that Van’s Aircraft currently sells that meets the RV-14 engine criteria is the IO-390-A3B6.


I had not made a particular note of these disclaimers. I based my decision to go with the Tbolt and the option for the AFP FM-200 fuel injection on Van's and Lycoming's 2016 SnF published flyers that I believed included these selections. It was not completely apparent to me in reviewing the sales flyers that these issues might occur.

In Vans' defense, they do a super job in the R&D, design, manufacturing, and customer support of some very sophisticated aircraft kits. Their achilles heel, as the kits get more and more user friendly, is that us customer builders come to expect that all of the pieces will go together perfectly and with no problems. The lesson here is that if you deviate in the slightest way from the provided parts and the instructions - you are experimenting. It is an EXPERIMENTAL airplane, and you tend to forget that because the kit, especially the 14, is so incredibly advanced.

So, at this point here is what I believe has caused my issues and what else I know now.

Lycoming has told me that the Thunderbolt is precisely the same engine that are the standard engines that Van's supports; it is tweeked on the inside via a bit more attention to assembly, fit and balance, and offered in a few more exterior paint schemes. The exterior dimensions and arrangements are the same. Engine is not the cause of problems.

I think now, before I can confirm this after I get a new snorkel and refit it to an AvStar throttle body, that I did not fit it first using a AvStar unit to observe and record the position of the snorkel relative to the engine and particularly - the starter. I may have let the snorkel drop down a bit too far below the starter and too close to the cowling. This has become apparent as a few responses by VAF members and folks at Van's report that the clearance to the starter is very close.

I should have the replacement snorkel by early next week and be able to make this test fit.
 
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Update

Just remounted the lower cowling after fitting a new snorkel to the filter box and the Bendix throttle body that I acquired (same as the Precision Air or the AFP FM-150). The Bendix unit is 5 1/2" long; so without a body unit a block of wood or hard foam block could be a substitute.

All appears to fit nicely. Viewed the lower cowling to snorkel clearances with a snake video inspection camera and the clearances are about 1/2? at the nearest points.

The key to fitting these is now a lot clearer. By attaching the Bendix throttle body and then fitting the snorkel to it and making the first fits to the filter frame and clecoing that together; and getting the clearance between the top of the snorkel and the starter as close as possible (about 3/32? - 1/8?).

There is a small area on the back side of the snorkel near the filter frame where it slightly touches the intake manifold pipe to cylinder #2 that will be a minor adjustment, probably cut a small divot out of the snorkel and a re-glass to fit to clear.

Next then - to cut off the snorkel flange that attaches to the Bendix throttle body and glass in the 3 1/2? diameter x 1.25? long fiberglas pipe that will align and connect to the Airflow Performance FM-200.

The FM-200 is 6? long, plus you have to install an adapter piece that is 3/4? thick (plus two gaskets each side) between the FM-200 and the oil sump induction inlet. So you?re dealing with the throttle body that is 1 1/4?+ longer overall.

Now that I have the snorkel-to-filter frame attachment well set (temporarily with clecos) and some good documented dimensions and pics of the snorkel fitting to the throttle body, the fitting to the FM-200 should end up with good clearances to the cowling. This what I lacked having when I did the initial snorkel modifications and fitting.
 
Picture record

I am taking notes and pics as I go through this again.

When I finish up and everything goes good I will post the updated process and pics.
 
Finished modifying new snorkel

I finally finished modifying the new snorkel.

As mentioned in the earlier post, the most important step in starting to modify the snorkel for the FM-200 throttle body is first mounting the snorkel to a Bendix style throttle body and taking note of the clearances to the starter, a few pics, and diagrams.

The next steps depend mostly on your artistic/technical savy and fiberglas modelling skills. In all the modifying, adjusting, trimming, mounting, and redoing all steps over again over a period of about a week finally resulted in finishing up. The modifying/adjusting/reglassing the snorkel had to be done in lots of small steps. I tried a bit of modelling with blue foam (Styrofoam) and also with soft filler material covered with spackling paste - these did not work that good for me. The thing that worked best for me was to build up the reglassing first with 0.90" stainless rods and narrow strips of fiberglass trimmings, and then laying patches of fiberglas cloth over the ribbing in 'patches' of area. The 'patching' allowed me to get to the interior surfaces of the patches to smooth and form. It also let me position the snorkel so that the wetted glas patches hung to form the patches in gentle curves (gravity assist) between the ribbing. If you are much more experienced with forming glas using foam molds that may be the way to go to do the glas work in fewer steps.

The resource available for me was being 16 miles from Airflow Performance at KSPA. I was able to take the snorkel and throttle body to Don Rivera and mount it on their air flow test equipment and measure all the operational specs. Everything was well within specs according to Don and his 30 minutes of explaining it all. I understood some of it, but parts of the explanation went a bit over my head.

The things that Don advised as I got more into the modifying was to avoid any air dams in the snorkel, especially at the >90 degree turn into the throttle body, and keeping the tunnel as smooth as possible.

My own vision of how the air was flowing at the bottom knuckel at the last turn seems to suggest that the air needs the extra bit of space to get around that greater than 90 degree turn. So I let the 'bulb' space be as large as I could let it be using the original snorkel form; you have to keep refitting it to the plane to make sure that everything stays compact an within the cowing space. That tight corner bend on the small radius needs a ramp and smooth bend around it into the throttle body.

In the next few days I will post a few of the pics that I took at the earlier stages.

Don Rivera says that there are more than a few aircraft out there using the FM-200 on 360 and 390 size engines and likely enough RV's that have modified the snorkel to fit. His installation manual has a few photos of RV snorkels using the FM-200. In my experience with it, it was accomplished and it does work properly and fits in the cowling and around the engine parts - took some time and a bit of effort.
 
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Don Rivera says that there are more than a few aircraft out there using the FM-200 on 360 and 390 size engines and likely enough RV's that have modified the snorkel to fit. His installation manual has a few photos of RV snorkels using the FM-200. In my experience with it, it was accomplished and it does work properly and fits in the cowling and around the engine parts - took some time and a bit of effort.

I'm one of these people Don is talking about. I installed a FM200A on my Titan IOX-370. With only 1/2" clearance between the bottom lip of the injector intake and the cowl, the snorkel wasn't going to fit. I had two choice, put a blister in the cowl or put a forward facing scoop on the cowl and route the intake air directly into the injector. I ended up doing the latter and am happy with it, although it took a lot of time. I had to route all of the control cables in a custom way and fabricate my own brackets. A real PITA although I am happy with the end result.
 
Snorkel mod to FM-200 progress pics with notes

Here are some pics from starting the snorkel modifications through to lots (and lots) of glasing steps:

1. The AFP FM-200) throttle body. Front of FM-200 is about 1 3/8" further forward than the FM-150 and 9/16" greater inside throat radius (Bendix type):
o3V.jpg


2. The Bendix style (AFP FM-150) throttle body:
o3S.jpg


3. Snorkel in place after trimming off the snorkel Bendix flange and positioned in front of the FM-200; marked centerline of the FM-200. Note how the lower lip if the FM-200 is below the snorkel edge:
o3g.jpg


4. Preliminary positioned glased ring into snorkel, approximated after snorkel in position on the engine (lots of incremental steps positioning to get to this point); glased ring is interior and exterior diameter of the FM-200 throat and 1 3/4"+/1 long. Note the blue mark on snorkel > the approx line on the forward rim of the FM-200 - the edge of the ring will end up being about 1/8" clear of the forward rim of FM-200:
o3h.jpg


5. Will be cutting the bottom of the snorkel out to the largest cut-out line (and then some as I progressed):
o3O.jpg


Next post with 5 more pics>>
 
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6. Positioned snorkel with fingers cut into bottom of snorkel. I had to abandon the 'fingers' mod because these fingers flattened out and eliminated the nice bottom buldge of the snorkel (taking out a lot of the volume of the snorkel). Had cut out the whole bottom to build in length-wise ribs of SS rod, tacked with super glue, repositioned many times to get proper alignment to FM-200.
o33.jpg


7. Snorkel with fingers cut into top of snorkel. These were bent down to the top of the glas ring, and tacked with super glue, repositioned many times to get proper alignment to FM-200. Eventually glased to the ring; as they were bent down, their ends came forward to the forward edge of the glas ring.
o34.jpg


8. Bottom of snorkel completely cut out and ribs tacked onfor shapoe of buldge.
o3Q.jpg


9. Early positioning alignment - note how the glas ring is not well aligned with FM-200 throat. Had to pop off rib ends and re-super glue a number of times to get the alignment right on.
o3T.jpg


10. Middle portion of snorkel has been cut out and has a few glas longitudinal ribs tacked on. I order to take out a twist in the snorkel body between the two ends I had to eventually do this. You may find no twist or a better way to do this. I first tried cutting some lateral cuts to make the snorkel 'accordian' to take the twist out but that did not work like I thought it would.
o3a.jpg


From here on, the process is many attachments to engine, un-tack stuff, re-tack stuff, twist and tug, then many small glasing patches of the openings in steps that allowed me to get to the inside of the snorkel as much as possible and to let the patches of glas to hang via gravity to form as much as possible rounded patch forms rather than faceted patches.

This is the orientation of the throttle body on the engine; it has to be this way because there is a sensing port on the stem (small hole just to the left of the center cone) that has something to do with regulating the fuel flow (from my memory of an explanation by Don Rivera). If that port is on the opposite side close to the sharp bend of air around the last turn of the snorkel into the throttle body, the fuel flow goes way down.
o3E.jpg


Here is the snorkel hanging on the engine.
o3b.jpg


The snorkel is attached to the throttle body with a 1 1/4" long x 3 1/2" I.D. piece of silicon reinforced hose (race car type used in the super charger zone). Bought a short piece on line from K&N (kandn.com); Cut it to short pieces on a metal cutting band saw. Stainless hose clamps (No. 60, 4" Dia) on throttle body and snorkel ends.
o3t.jpg
 
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