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Red Cube Install - A new look at an old challenge

CJ in EP

Active Member
There seems to be a lot of information on how to mount these, no two are alike, and each method is a unique combination of benefit vs. compromise. Here's my take.

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It starts with a new bracket made from a 12" x 12" sheet of 4130 purchased from McMaster. A hacksaw, files, and the dirt-cheap break from Harbor Freight was all it took to make this. The tapered shape and bends were made to exactly match the existing Lycoming bracket which mounts the fuel divider, and the bracket uses the same 1/4-20 bolt as its primary point of attachment. Opposite this bolt there are two tabs which, with the use of Adel clamps, provide additional support to the bracket by attaching to the push rod tubes. This is admittedly the compromise in this design, but great pains (and three different attempts) were taken to build this so there isn?t any load in tension or compression on the tubes.

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Two new fuel lines were necessary, made by the very capable hands of Tom Swearengen of TS Flightlines; one a stainless steel hard line running from a bulkhead fitting at the rear baffle to the transducer input, and one flexible/firesleeved line with 45? fittings running from the transducer output to the divider. On a side note, it?s been said many times and I?ll add to the chorus, Tom was a great guy to work with, his knowledge is unsurpassed, and he demonstrated a great amount of patience in dealing with a rooky like me.

The next two photos show the clearances of the new plumbing with the existing injector line plumbing. I?ll finish the install with an Adel clamp to secure the flex line to the divider bracket.


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Not what I would recommend. Adding a bunch of hose length above the engine will result in heating a bunch more fuel while parked. Engine starts after a quick turnaround could be more challenging.
 
In addition to Scott's comment you now have a loop at the highest point for vapor to accumulate.

Not going to work well.

Old pic but this custom fitting is the best approach IMO.

MGRhz69FKYB6zAh4zXmxVHW2D9tobe3LmHH-0NIiQuxfQJWtmJDZTQMB_o3zc3FdFOvgq2a0YmZgZFlyJbv-IUGIxHhfDnUrnwupCefR4cBrFyZVLkL6vj9--StDijdlJMV7H50MNw3TaF3tS7_zJX-ih4prYJXl6I8_tFPUbasqSjydEhQ5_nKCKAJqFekJyzXnW0vj1s_FbPAxkfrINFfbF4cwEAo87I2kDgEY-EGRO4TvRmMEiidqYgmzozLa9FZFUyi08bQ5uNW6WZpmThxWvbloIGes1c6vOHvmAGi0guS-k8excvdCwIUfYeYNq8_FKZ8C9DNNYSx0B-y5BjGBfQ23Rj92AMI0pTlZQRp5g6fb4Yvi-JUI1T5M6Zj0-MGGx1mTxthLs3u7nRNI-xqLesR2DuHDp2_WGWL9S62FT0eUGuQZl4ETw-HbQw8gsExhPiUJWGvMKGk5uqrV8eX80hUI5ncNet4AMiPh_Ex1P7XUvdRLFZOxZnJ39IEGzYDO92Ku190jbiBVmy1DpIJERHZApR0paOvig8T9s-wmdoezPTFS5wsbHC5TOls2foOXk6L9Q46cweD2PGxFHimWdTw7Mo61udlFg1_JMrNguVBVDsuX2p8JJP3R8kBBKC27lwnEcvR0LTYq0BJRAr9KLtuZqSB1=w400
 
Why is fuel inlet from rear of engine?, all the ones I?ve seen divider is clocked so inlet is in front which makes install easier with less plumbing
 
Compliments on nice workmanship.
Just wanted to pass on another concern about penetrating the baffle with a hard line at that location. Unless well braced, that spot can be the source of significant vibration, especially if an oil cooler is hanging off the baffles. Mine is rock solid now, but I learned the hard way after cracking the oil cooler flange on the onboard side.
 
Looks beautiful. But.....you know Red Cubes are notorious for being susceptible to vibration and heat......but it wont cause any fuel issues if it fails, so give it a try!

I'd also agree with the hesitation on a hard line thru the baffles however....
 
Red Cube mounting

Where you did a nice job of mounting your cube, you have done a few things not recommended in your install.

General Placement Recommendations for Fuel Flow Transducer

1. Do not install the fuel flow transducer, hoses and fittings near exhaust system or turbocharger. Excessive heat can damage fuel system components.

2. Do not install 90 degree fittings (elbows) on the input or output of the fuel flow transducer. Doing so will cause turbulence in the fuel flow which causes inaccurate fuel flow data.

3. Install the fuel flow transducer with the three wires pointed UP.

4. Install a fuel filter UPSTREAM of the fuel flow transducer to screen out debris.

5. For best measuring performance, the fuel should travel uphill by one to two inches (25-50 mm) after leaving the fuel flow transducer.

6. Placement of the fuel flow transducer relative to other items in the fuel system like fuel pumps is left to the builder. It is common to place the sensor downstream of any auxiliary electric boost pumps but upstream of the engine driven fuel pump.

BIG NOTE: Due to vibration issues, never connect the fuel flow transducer directly to the engine.

ANOTHER BIG NOTE: When sealing the fittings on the fuel flow transducer, do not use Teflon tape! Instead, use a sealant such as ?United EZ-Turn Fuel Resistant Lubricant? or ?Permatex Thread Sealant?.

I would reconsider where you mounted your cube, unless you want it to fail prematurely.

Brian
 
Moving goal posts

Where you did a nice job of mounting your cube, you have done a few things not recommended in your install.

General Placement Recommendations for Fuel Flow Transducer

1. Do not install the fuel flow transducer, hoses and fittings near exhaust system or turbocharger. Excessive heat can damage fuel system components.

2. Do not install 90 degree fittings (elbows) on the input or output of the fuel flow transducer. Doing so will cause turbulence in the fuel flow which causes inaccurate fuel flow data.

3. Install the fuel flow transducer with the three wires pointed UP.

4. Install a fuel filter UPSTREAM of the fuel flow transducer to screen out debris.

5. For best measuring performance, the fuel should travel uphill by one to two inches (25-50 mm) after leaving the fuel flow transducer.

6. Placement of the fuel flow transducer relative to other items in the fuel system like fuel pumps is left to the builder. It is common to place the sensor downstream of any auxiliary electric boost pumps but upstream of the engine driven fuel pump.

BIG NOTE: Due to vibration issues, never connect the fuel flow transducer directly to the engine.

ANOTHER BIG NOTE: When sealing the fittings on the fuel flow transducer, do not use Teflon tape! Instead, use a sealant such as ?United EZ-Turn Fuel Resistant Lubricant? or ?Permatex Thread Sealant?.

I would reconsider where you mounted your cube, unless you want it to fail prematurely.

Brian

Hey Brian

I believe EI have moved the goal posts on this one. Current guidance linked here
https://buy-ei.com/wp-content/uploads/FT-60-Info-Rev-F.pdf

If one reads all the guidance ever written on mounting this thing then the only place for it is in close formation with the aeroplane along with the antennae and magnetometer!

Note main differences from what you posted:

Removed advice not to mount near exhaust, heat source or directly to engine.

Removed advice to not use 90 degree fittings.

Added insistence that the unit MUST be downstream of the last fuel pump (their capitalization)

personally I am mounting mine like this:http://www.vansairforce.com/community/showthread.php?t=134975

Just spent an hour mocking up and checking hose lengths and I believe it will work well.
 
In defense----Chris had the 'unusual' plumbing of routing the servo hose to the aft baffle. At the same time, with all the flame wars about where and how to mount it, not mount it, plumb it, etc he had the unusual install of the flow divider being installed with the inlet port facing AFT.

YES we discussed the possibility of heat related issues after shutdown, and he was going to test things, and change if necessary. As everyone on VAF and others have seen, there is NO one one to do this. Everyone has an opinion, and all are right, no one is wrong. We tried for 8 years to get EI to tell us HOW THEY wanted the transducers mounted ( so we could develop a kit for that install), but their answer has been, "Its experimental, the builder can do whatever they want."

Also in defense, we've plumbed alot of these transducers, in alot of different places for ALOT of you. Some similar, some different. Yep, for some individual reasons, some were changed around. The fact of the matter is there is no recommended install location or plumbing. The RV14 IO390 FWF package as designed by VANS, has it between the mechanical pump and the servo mounted with an adel clamp on the #4 intake tube. I know of several OE install on certified planes where its mounted on top of the engine, with 2 hoses, so if its good enough for a certifed install, why not an experimental?

Chris did his homework and alot of research, and in his case came up with a plan. Yes he will try this out, and has accepted the fact that he maybe changing it around, IF it doesnt perform as it needs to. As for the transducer, yes the wires are UP---until he flies inverted--significant straight in/out of the cube---kinda per EI's recommdation. NO this install isnt in the finished stages, but getting there.

Tom
 
BTW---there seems to be some 'crossover' in the install instructions for the FT-60 and the FloScan. The Flo Scan was definitely susceptable to all the things that have been stated here---needing 2 inches of straight inlet/exit before an angled hose or rigid tube, definitely no hard mount and wires up up.

"The overall accuracy and linearity of the Red Cube FT-60 is superior to most other flow transducers. The Red Cube FT-60?s design vacates bubbles and is not nearly as susceptible to debris as other units on the market. " "The Red Cube FT-60 should NOT be installed with the wires pointing DOWN (the best situation is with wires pointing UP). Also, the fuel line on the outlet port should not drop down after exiting the transducer. Both of these configurations can trap bubbles in the transducer causing jumpy readings. The inlet port, outlet port and flow direction are marked on the top of the Red Cube FT-60." That is a quote from EIs install guide. Wires not DOWN, transducer exit not down. So in most of the installs, even those near the servo, the wires are either UP or on the side, NOT DOWN, and the exit is either horizontal or vertical, not DOWN. Even in our flow divider location, we adhere to those guidelines.
Dave Arata of Ei, back in 2016 stated this:
"The main reason to not mount the transducer between the boost pump and engine driven pump is the because the boost pump can create a hammering affect against the engine driven pump when turned on. This causes the impeller in the transducer to be pulsed forward and backward quickly which is counted by the instrument as increased fuel flow.
An additional concern, while we have never seen it, is the possibility of vapor lock. The transducer was not designed for fuel to be sucked through it. It was designed for fuel to be pushed through it.
It is best if installed with the wires pointing up, as that is where the transducers were tested. However, ease of installation should take precedence. Flexible like should ALWAYS be used to provide vibration protection and the output port should not be pointing down. Installing the transducer in such a way can trap air bubbles and cause erratically high fuel flow readings due to the optical sensor seeing refracted signals."

One other thing----The Flo Scan was a pretty weak thing---Yeah I broke one one time installing a AN nipple. The FT 60 is a much more robust unit. TO MY KNOWLEDGE, and please correct me if I'm wrong, I have NOT heard of a failure of a FT60 that the root cause was because it was hard mounted to a bracket. ANYWHERE.

Be advised---because we do ALOT of these installs, I will AGAIN be talking-or trying to talk --to EI at OSH and get them to give us a recommendation so we can develop an install package thats universal for most all of you guys. Yep---I'll report back after OSH.

Oh----if someone has a better idea, I'd love to hear it.

Tom
 
Manual F.I. VS. vapor lock and hard starts

My question is a little bit off subject because the main discussion is concerning the red-cube. Also, I?m a high pressure/electronic fuel injection guy, so the potential issues such as vapor lock and hard starts that can occur with with a standard manual fuel injection installation such as this really don?t apply to me. However, I?m curious to know why people don?t install a small 1/8? fuel return line ?T?d? in right at the spider divider. It seems to me that if a small fuel return line was incorporated into the plumbing and controlled via an on/off solenoid, that all of the hot fuel and vapors could be purged out of the system which would eliminate vapor lock and hot starts. My buddy installed a purge/return line such as this with his Ellison T.B. equipped -7. He was having terrible issues with vapor lock, but once he incorporated this little purge/return line, all of his vapor lock issues went away.
 
Jon, Chris just hasnt plugged it off yet---he knows about it.

Mark---AFP did have a purge valve for the FM200 servo. Don redesigned it so the purge wasnt necessary.
I cant speak for everyone, but I think a hard hot start on a FI engine is somewhat common, versus a carbed install, since the carb is up draft.
Downdraft carbs have a similar hot start issue---remember the hot running engines we had in the 60s and 70s with headers> the old Rochester Quadrajets were notorious for hot start---even some Holleys were.
Mark I assume you have a EFii or SDS injection, you have a full return fuel system and when the pump is running you (supposedly) have cool fuel that flows through the entire system and back to the tanks---just like your car. Mechanical Injection isnt like that.

Tom
 
Hey Tom. Yes, I have continuous, cool, high pressure fuel flowing through my entire fuel system, so V.L. or hot starts are never a problem. I understand that that carbureted and or mechanical F.I. systems and plumbing are completely different from my setup. However, I?ve seen so many people struggle with V.L. and hot starts with mechanical systems that I was just curious as to why more people don?t incorporate some kind of a little ?controllable? return/purge line into the plumbing so that they could just ?sweep? the hot fuel and vapors out of the lines?? When I saw the results my buddy had when he incorporated this simple ?controllable? fuel return/purge/sweep line into his plumbing, I was sold on his results and was/am convinced that this was/is the ?fix? for V.L. and hot start issues.
 
I know of several OE install on certified planes where its mounted on top of the engine, with 2 hoses, so if its good enough for a certifed install, why not an experimental?

One reason I can think of is that it is very rare for any certified aircraft to be a tightly cowled as an RV (though maybe the examples you are thinking of are.... can you mention specifics?). With small inlet and outlet openings (compared to most certified aircraft anyway), RV,s don't naturally cool via chimney effect when parked. Opening the oil door helps a lot but that does not directly cool the plenum area above the engine.

The OP put his idea out here and many people have offered their opinions. If he chooses not to heed any of the advice or comments, that is his choice. With you now offering defense of his plan, it somewhat appears that it was your design idea. If not, then it doesn't seem necessary.

One suggestion that I hope will be taken very seriously is the installation of a hard line between the flow transducer and the rear baffle. This section of baffling is exposed to a lot of vibration because of the mass of the oil cooler and the influence of the baffle seals on the non-moving interior surface of the top cowl. I have a serious concern with this. The excess hose causing a hard starting issue will simply be an annoyance and can be corrected with a future change, but a brake in the hard line could be very serious or worse.
 
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Scott---Chris came up with several ideas, and after doing some mock ups, we built the hoses and tubes for him for his application. The baffles are going to be reinforced, 1 due to the oil cooler, 2 for the bulkhead fitting/stainless tube install. We really tried to do a hose from the bulkhead fitting to the transducer, but the overall length was too short, too much offset, making a hose application not practical, with out a big loop. His servo to bulkhead fitting hose is long enough to reach the transducer, if necessary.

Tom
 
Scott---Chris came up with several ideas, and after doing some mock ups, we built the hoses and tubes for him for his application. The baffles are going to be reinforced, 1 due to the oil cooler, 2 for the bulkhead fitting/stainless tube install. We really tried to do a hose from the bulkhead fitting to the transducer, but the overall length was too short, too much offset, making a hose application not practical, with out a big loop. His servo to bulkhead fitting hose is long enough to reach the transducer, if necessary.

Tom

Then may I suggest that a hose be used for the entire circuit from the throttle body to the flow transducer and seal it with a grommet where it passes through the baffle.

I have seen dozens of different ideas implemented, in attempts to re-enforce that corner of the rear baffle and they all failed. The left rear corner is the least supported (because of how it has to jog around the #4 cyl head), but is the most vulnerable because of the mass of the oil cooler and hoses. This is evidence enough that there is a lot of vibration induced on this area of the baffling. Putting a hard line between the solidly mounted transducer and the baffle (which has tons of in service evidence to be always influenced by some level of vibration) is not a good idea.

I don't post very often regarding something I see as a potentially serious safety issue, but this is definitely one. I hope the OP will consider changing at least this one aspect of his design.
 
Scott, the baffle reinforcement does bring up a very valid point. We never really know how much is enough. So after thinking about this, I altered the inlet line and fitting arrangement to use a hose with enough flexibility that will solve that issue.

Tom
 
Wow!

Thanks to everyone for the thoughtful discussion!

Let me first tell everyone the most disappointing part of my Van?s -9A build. After considerable research on the three most likely engine sources, I decided that the best path to a trouble free engine install (admittedly my weakest skillset in the build) had to be buying a factory Lycoming through Van?s, as well as the Van?s finish kit. Honestly, I have a hard time believing that Van?s has any idea if the oil and fuel hoses, and control cables they sell with the kit have any possibility of fitting. One of the two oil hoses had no possibility of fitting (well documented elsewhere on VAF where the fitting will physically interfere with the oil filter), the throttle and mixture cables were both well short of reaching their positions, and as demonstrated, the fuel system is proving to be a bit of a challenge.

It also doesn?t help that my divider seems to have been mounted in an usual orientation by the factory, making one of Tom?s best solutions difficult without redoing the injector lines, which I?d prefer to avoid.

For the record, for whoever was asking, this is my design, Tom and I talked through its weaknesses, and I decided to start here. I?m the one who stepped in it.

So in summary, my engine install has been a total PITA, and my new look at an old challenge pretty much sucks. Bummer. However, I got exactly what I was hoping for by posting in this forum, and I?m genuinely grateful for the good feedback! My system will only get better from here, and Tom has already shipped a new flex hose prototype to replace the the hard line.

As uncomfortable as public scrutiny may be, I?ll keep this thread going with the hopes of coming up with a really good solution, and hopefully making it easier for the next builder. And BTW, Ed in Zimbabwe, your comment that the only place for these is in close formation with the aircraft made me laugh, thanks for keeping it light!
 
Some notes...

That is a really nice bracket. My compliments.

I'm with Scott regarding the excessive hose length and the hard line.

Bob's note regarding the loop is valid. Great place to store lots of vapor.

If the divider's inlet port is in an awkward position, re-mount the divider.

A red cube works fine with the flow path pointed vertical.

Mark, your idea regarding a solenoid-valved purge line is perfectly valid. An NC valve seems safe enough. A lot of us use a cable operated purge valve from Airflow Performance.

While on that subject, the original reason for the AFP purge valve was the use of a drum-type mixture valve on earlier fuel controls. The have a leak rate; some installations (not all) didn't exhibit a clean idle cut off. The valve dumps all line pressure back to the supply system. The most recent controls (notably the FM150 for RV folks) has a disc mixture valve, and a very low leak rate. The purge valve is not needed for a clean idle cut off. However, a builder can still install a purge valve and use it for its other valuable function, circulating cool fuel prior to start.
 
One note that I did not see mentioned: Clamping anything much heavier than ignition wires or spider lines to the push rod tubes is generally to be avoided. I?m not predicting anything catastrophic here, but the combined mass of the red cube, the steel bracket, and the attached lines is fairly substantial, and one end of this whole assembly appears to be supported by mid-span clamps on the tubes. The tubes are thin aluminum not intended to be structural elements, and are supported at each end by nothing more than a soft plastic washer jammed into bosses on the engine case and cylinder heads. It is hard to predict what sort of dynamic vibrational loads might be imposed upon the tubes by this assembly in flight.- Otis
 
Thanks to everyone for the thoughtful discussion!

Let me first tell everyone the most disappointing part of my Van?s -9A build. After considerable research on the three most likely engine sources, I decided that the best path to a trouble free engine install (admittedly my weakest skillset in the build) had to be buying a factory Lycoming through Van?s, as well as the Van?s finish kit. Honestly, I have a hard time believing that Van?s has any idea if the oil and fuel hoses, and control cables they sell with the kit have any possibility of fitting. One of the two oil hoses had no possibility of fitting (well documented elsewhere on VAF where the fitting will physically interfere with the oil filter), the throttle and mixture cables were both well short of reaching their positions, and as demonstrated, the fuel system is proving to be a bit of a challenge.

It also doesn?t help that my divider seems to have been mounted in an usual orientation by the factory, making one of Tom?s best solutions difficult without redoing the injector lines, which I?d prefer to avoid.

For the record, for whoever was asking, this is my design, Tom and I talked through its weaknesses, and I decided to start here. I?m the one who stepped in it.

So in summary, my engine install has been a total PITA, and my new look at an old challenge pretty much sucks. Bummer. However, I got exactly what I was hoping for by posting in this forum, and I?m genuinely grateful for the good feedback! My system will only get better from here, and Tom has already shipped a new flex hose prototype to replace the the hard line.

As uncomfortable as public scrutiny may be, I?ll keep this thread going with the hopes of coming up with a really good solution, and hopefully making it easier for the next builder. And BTW, Ed in Zimbabwe, your comment that the only place for these is in close formation with the aircraft made me laugh, thanks for keeping it light!

I am not sure what most of this has to do with the subject of your thread, but I am sorry to hear about your frustrations with some of the parts.

There is often a simple explanation for why a part doesn't fit a persons particular installation.

The engine control cables for example..... they are sized for a standard instrument panel installation. It is fairly common these days for custom panel manufacturers to deviate from that design. Specifically, the mounting plate at the base of the panel that the controls attach too. It has become common for them to supply a different part that locates the mounting hole flush with the face of the panel. That repositions the controls 1" - 1 1/4" further away from the engine than intended. That is more than enough change to make a control that would have worked, not work at all.

All of the parts in the FWF kits have been tested and are in use on Van's demonstrator aircraft so if they don't work, there is a good possibility that they either haven't been installed as intended or that there is something different or modified with the engine in question (such as a different oil filter adapter installed perhaps?).
 
Scott brings up an excellent point regarding the fit of the stock Vans hoses and other components. A hose may fit on the demonstrator aircraft, but that doesn't help a builder who is frustrated because it doesn't fit on their aircraft.

Rather than changing the aircraft to make an oil hose fit, we believe it is easier to build the oil hose to fit the exact configuration of the aircraft.

One thing we have learned through plumbing firewall forward hose kits is that there are so many little configuration variables that exist that what may work on one aircraft may not work on another.

There are a few things we can do to help mitigate this.

1. Tom and I have amassed a huge database of customer data which is organized by aircraft type and allows us to access a variety of different plumbing configurations so we can help build custom length hoses that fit. Chances are that we have probably already seen your configuration and have data on the way to make all the hoses fit perfectly. Sometimes manufacturers change things. When this happens, we hear about it from builders which allows us to refine our data even more.

2. Another thing that greatly helps is not viewing individual hose lengths as set in stone. For example, a VA190 hose has a fixed length and is used as an oil hose for both the RV10 and RV14. However, we view it simply as an oil cooler hose and adjust the length to fit the configuration of aircraft that it is going on. This means that the oil cooler hose that is part of our firewall forward kits will fit in the place of the VA190, but will be built to a slightly different length than a stock VA190. For instance, if you have a backup B and C pad mounted alternator on an RV14A, it causes us to change the length of this hose slightly. The customer never sees the small length difference, other than that the hose fits.

With all this said, there are still many times when we come across something new. Or, we have a builder find a better way of doing things. We view this as part of our R and D process and getting more accurate and complete data. If we ever build you a hose that doesn't fit, we will take care of you. It may mean shortening your hose, or it may mean building a new longer hose for you. It's all part of our 10 year hose warranty.

Chris,

I am not sure why the stock Vans components that you purchased are not all fitting to your liking. But, I do know this. I have known Tom for a long time. I started as a very satisfied customer of his. Now, we are business partners and talk multiple times daily as we work on new joint projects. You're in great hands, and he will take care of you from start to finish on this engine until you are flying. Part of the build is working through frustrations, but it's all worth it in the end.

Happy building everyone!!!!!
 
Rather than changing the aircraft to make an oil hose fit, we believe it is easier to build the oil hose to fit the exact configuration of the aircraft.

What I intended to mean was that if standard kit parts don't fit, there is a good chance that something in the configuration of the airplane is already changed from standard.

We now return you to your regularly scheduled advertisement commercial ;)
 
To echo Scott, I just finished my RV-7A using Van's IO-360 with Hartzell prop and FWF kit. Everything fit with no modifications required installed per plans. Obviously you have deviated from the Van's standard.

Also I have a red cube in my RV-12 per plans between the boost pump and engine pump inside the cockpit behind the firewall, like the 10. I did the same on my 7A and it appears to work fine and appears very accurate even without modifying the standard Dynon K factor with the boost pump off. Flow rate is way high with the boost on but it is rarely on. Firewall forward deals with heat and vibration, firewall back does not so for me I'd rather accept any inaccuracy and adjust the k value for X-country accuracy.
 
Scott,

No advertisement at all...just putting energy into machining a round peg to fit in the round hole. Tom has an impeccable customer service record. I met Tom years ago while building my -10 and he helped me back then as he has helped thousands of other builders get their aircraft flying.

The OP was frustrated that the stock components he purchased didn't fit. I haven't worked with Chris, but it sounds like he purchased all the parts including the engine as stock from Vans and assumed it would all fit. The stock engine that Lycoming delivered is apparently not set up exactly the same as the demo aircraft.

But it's not an issue....I'm sure Tom will take good care of Chris and provide solutions to get it squared away. One thing I have NEVER heard Tom say is to tell a fellow builder that "They did it wrong" He will work with them until it's right. He is a class act.
 
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For what it's worth... My engine has the same flow divider orientation. I was hoping I could find a better photo, but the one below gives the general idea. Several things have changed since it was taken 9 years ago but the general hose routing hasn't. I've since realized that this is a somewhat unusual flow divider location.

i-X4tncCM-L.jpg


My red cube is now suspended vertically (wires facing aft) by the fuel line exiting the servo and the one visible in the photo, been that way for about 500 hours. It is dead accurate and reliable, and seems to be completely unaffected by the boost pump.

My first red cube failed after about 350 hours and had been flaky for some time before that. I had it hard mounted to a bracket fixed to the magneto studs (no magneto due to LSE ignitions). The failure seemed to be heat-related, not vibration. The steel bracket and proximity of the engine (less than 1/2" to magneto block-off plate) did a terrific job of transferring heat to the red cube despite being wrapped in sleeve material. Wish I had pix of the red cube install, previous and current, but I can't find any.
 
UPDATE:::
I was able to talk to EI at Oshkosh. Actually quite pleasant, and some useful information. Idea is for the transducer to not accumulate any air that may change the flow indications. They did not have any issues with the way we have been installing them at the flow dividers. We'll work on the mounting thing.
The original install EI did was a firewall location on a Navion, and dont have any data in other locations---he said. So with that in mind, we are open to developing a good universal install location that works for most builders.
WE happen to like the flow divider location because its at the end of the common fuel flow path (before it divides to the cylinders), and for us uses 1 hose instead of 2. Certainly this is NOT the only install that works, and we'd love to hear of others. Scott, as a Vans Engineer, we'd certainly love to hear of your recommendations and results you've seen from the Vans demo and prototype planes.

Tom
 
Tom, I am very interested in what you come up with on the red cube install. I need to install mine (RV7, IO-360-M1B, everything standard), and am having a difficult time deciding where and how to mount.

Thanks,
John
 
Between pump flow reading

Is there a cause of the change in fuel flow reading when a boost pump is on or off when the transducer is installed between the pumps? I?m adding the cube to my setup, and it going to need to go between the pumps. Is there a known way to minimize? I tend to use the electric pump 100%. Low pressure.

Setup: Tanks to valve to boost pump (facet) to collator to red cube to engine pump to Ellison. The routing goes from the tradional collator position at the lower right edge of the firewall over the top of the engine to the top left front (fwd of #2)since it?s an H2.
 
Is there a cause of the change in fuel flow reading when a boost pump is on or off when the transducer is installed between the pumps? I’m adding the cube to my setup, and it going to need to go between the pumps. Is there a known way to minimize? I tend to use the electric pump 100%. Low pressure.

Setup: Tanks to valve to boost pump (facet) to collator to red cube to engine pump to Ellison. The routing goes from the tradional collator position at the lower right edge of the firewall over the top of the engine to the top left front (fwd of #2)since it’s an H2.

It is believed / speculated that the pulsations from the electric pump cause the wheel to go back and forth slightly and therefore occassionally count extra rotations when the pulsation occurs when the magnet is about to pass the sensor. the cube works by having fuel flow across an impeller and it counts each rotation of the impeller. The pulsations are likely seen in the fuel volume upstream of the mech pump when acting against the rubber diaphragm of that mech pump as it goes up and down. This is why you wouldn't see them in a setup with only elec pumps or any setup where the fuel flow is restricted in a more stable way, such as by the servo or carb.

Larry
 
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Thanks

Thanks, that?s what I thought the concern would be. Not sure how you beat that except with some form of accumulator in the system. I may have to rethink my full time use of the boost pump. Alternately, since I could always keep it on, I could calibrate around the cause, I guess.
 
It is believed / speculated that the pulsations from the electric pump cause the wheel to go back and forth slightly and therefore occassionally count extra rotations when the pulsation occurs when the magnet is about to pass the sensor. the cube works by having fuel flow across an impeller and it counts each rotation of the impeller. The pulsations are likely seen in the fuel volume upstream of the mech pump when acting against the rubber diaphragm of that mech pump as it goes up and down. This is why you wouldn't see them in a setup with only elec pumps or any setup where the fuel flow is restricted in a more stable way, such as by the servo or carb.

Larry, I've thought about it a good bit, as well as torn down engine pumps and a red cube.

The cube's impeller is a very light plastic part. It acts as a shutter for a light beam; no magnets.

Try this. Pulsation source is the engine driven pump. Consider; when the boost pump is running, both of engine-driven pump's poppet valves are pushed open. If fuel flow demand is low, they may close momentarily, but they would be open for much of the pumps diaphragm stroke. At high flow the boost pump may hold those poppet valves open all the time. Regardless of open duration, the diaphragm is still being lifted by the pump pushrod and lever, and then released so the big spring drives it downward. A descending diaphragm and an open inlet poppet would be enough create a momentary reverse flow at the cube's rotor. The result is extra interruptions of the light beam, i.e. a higher fuel flow indication.

That's my story and I'm stickin' to it...unless somebody has a better one ;)
 
Larry, I've thought about it a good bit, as well as torn down engine pumps and a red cube.

The cube's impeller is a very light plastic part. It acts as a shutter for a light beam; no magnets.

Try this. Pulsation source is the engine driven pump. Consider; when the boost pump is running, both of engine-driven pump's poppet valves are pushed open. If fuel flow demand is low, they may close momentarily, but they would be open for much of the pumps diaphragm stroke. At high flow the boost pump may hold those poppet valves open all the time. Regardless of open duration, the diaphragm is still being lifted by the pump pushrod and lever, and then released so the big spring drives it downward. A descending diaphragm and an open inlet poppet would be enough create a momentary reverse flow at the cube's rotor. The result is extra interruptions of the light beam, i.e. a higher fuel flow indication.

That's my story and I'm stickin' to it...unless somebody has a better one ;)

Your theory has a much deeper insight and is likely closer to reality than mine. It makes sense. I have great confidence that the reversals are due to the interactions of the two pumps and their constant changes in state.

Larry
 
Wading in way over my depth here

I'm assuming the momentary reversals of the red cube impeller that create pulse events counted as higher-than-true fuel flow are events that happen at a lower incidence than the constant pulses from fuel flow in the forward direction through the cube. As such, they would appear in an output not unlike extra ventricular beats in an otherwise normal EKG strip. Since there are no true fuel flow surge events like this I am aware of in normal operations, it seems like it would be straightforward to digitally filter out any bursts of 2x higher frequency pulses coming from the cube and count them as only two discrete pulses and not three (2 pulses from normal forward flow plus one backward pulse of the impeller in between them) or some similar type pf algorithmic interpolation that would assume steady-state flow during times of digital "noise" on an otherwise steady pulse train.

In other words, digitally excise the junk data and fill in the gap with an assumed background rate from the previous second or so of data stream.

This would have to be done at the EFIS software level. And there must be compelling reasons I haven't thought of why it can't be / hasn't been implemented to mitigate this known issue.

I hope the above made sense. It's hard to put these concepts into words without pretty pictures. It's harder if your background isn't technical writing :rolleyes:
 
Probably be pretty easy to get some data....

Really, this doesn?t sound like a significant data acquisition task. The filtering, I can think of lots of ways that could be a challenge.

Anybody remember those pesky accumulators Toyota uses to put at the end of the V6?s they put in Camrys and es300?s? If you know what I?m talking

Is the rotor buoyantly neutral in fuel? Is there a reliable check valve option (the failure modes give me the willies though).

Interesting.
 
Just a thought, along the lines of Dan's post, has anyone by passed the mechanical pump and tested with just the boost pump? Most being rotary vane pumps--Otis correct me--seems more constant flow stream than poppet valve pump.
Pretty simple to test--remove the supply and discharge hoses from the pump and connect them together with a AN815-6 union, boost pump on and check the flow.

Tom
 
Always on?

Thanks, that?s what I thought the concern would be. Not sure how you beat that except with some form of accumulator in the system. I may have to rethink my full time use of the boost pump. Alternately, since I could always keep it on, I could calibrate around the cause, I guess.

Why do you always keep your fuel pump on? Do you have a back up Incase that one fails? If you have a mechanical and an electric back up, you probably should shut the electric after takeoff to run only on the mechanical pump. That way you know the mechanical pump is working, the. If the mechanical pump quits, you have the electric pump to fall back on. If you are always on the electric pump, you have no idea if or when the mechanical pump quits. Then if the electric pump were to fail, your engine quits without warning. Just a thought...
 
As a data point I put my cube between the two pumps on the cockpit side of the firewall and have otherwise met all other red cube criteria on a RV-7 with IO360. Similar to stock RV 10 and 12 locations. With the boost off fuel flow is accurate but on is almost twice actual flow. Boost is only on for initial climb and final descent so I don?t see any significant affect. On continuously you?d have to do a lot of fudging to the ?k? factor for the EFIS but that is easy. I?d just double the impulse value as a trial and adjust from there by flight experience.
 
Has anybody installed one of these fuel Pulsation Dampers and if so, did it stabilize the fuel flow indication? It is supposed to be installed right at the Red Cube output on a low pressure (carb) system.

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:cool:
 
Pump on answer: A wise man suggested + H2

An accomplished RV builder and pilot suggested that there was no downside to keep the pump on. It’s what he does. Then there’s the H2 specifics. The fuel has to come up from tank position against gravity to the engine driven pump over the top of the engine, or roughly twice as high as a “regular” installation. As protection against vapor lock, I run the pump all the time. I check the engine driven pump by shutting off the electric pump twice during preflight, once immediately after engine start, the second time during run up/mag check sequence.

Maybe a two-speed pump? It’s been common in passcar for a long time now. Really, two voltage, direct PWM may not work for an interrupter type pump like it does for a DC motor. Hmmm.
 
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