Increasing RPM above previous maximum

[terrye]

There seems to be conflicting information on Red Cube Fittings and installation locations.

I'm in the process of installing the Red Cube in my RV-9A and since it has fuel injection, I'm locating the Red Cube just aft of the firewall where the boost pump for the carb would otherwise be located. Because of the geometry, I have an AN822-6D 90 degree elbow on the bottom inlet and an AN823-6D 45 degree elbow on the top outlet.

The installation sheet that was shipped with my Red Cube (1030032 Rev. C) only says:
"It is your responsibility to ensure that the installation of this fuel flow transducer, related fittings and fuel lines does not cause the fuel pressure to drop below the specified Minimum Inlet Pressure plus a reserve as outlined in AD23-16."
It also says:
"If the aircraft has a fuel pump(s), the flow transducer MUST be installed downstream of the last fuel pump."

Regarding the former, no restrictions on fittings are mentioned. Regarding the latter, I've read lots of posts where the Red Cube was installed upstream of one or both pumps with satisfactory operation.

I also downloaded from Electronics International's website, the Installation Instructions for Primary Glass Panel Engine Monitor MBP-50P (II 0425051 Rev I) which states on P25 in a box showing Fittings:
#4 Straight - AN816-4-4D
#6 Straight - AN816-6D
#8 Straight - AN816-7D

#6 45 deg - MS20823-6D

#4 90 deg - MS20822-4-4D
#6 90 deg - MS20822-6D

Based on the above information from the manufacturer, I'm designing my installation using angle fittings on the inlet and outlet of the Red Cube. If there is other manufacturer's information that I have overlooked, please let me know.

[Brantel]

An old post of consolidated info from the horse's mouth:

Originally Posted by Mathew Sharp

As far as I know Dynon distributes both the FloScan 201B as well as EI's FT-60.

The FloScan unit is much more sensitive to the angles/fittings entering and exiting the unit. EI's unit does not care. You can run 90 degree fittings in and out of ours without problems.

JPI does not sell EI's FT-60

Maybe you can get Dynon to trade you for a FT-60?

Good luck!

Matt

Originally Posted by Mathew Sharp

You do NOT want to rigid mount the transducer to the motor (any part) using just a fitting. It is a huge safety issue. The fitting could theoretically fatigue and break. You absolutely need to have flexible line on both sides of the Floscan 201B or the EI FT-60 (that Dynon now utilizes).

After manufacturing/supporting flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after both fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more. Frankly we don't care if the thing flows straight up, or if you put 90-degree fittings in and out (FT-60 only) of the transducer. Just don't mount it upside down or flowing sharply downhill.



Hope this helps,

Matt Sharp

Originally Posted by Mathew Sharp

Hello All!

Your friendly neighborhood EI Tech support rep here!

There are really two issues in regards to EI?s specifications on flow transducer placement.

1. Accuracy of the output of the flow transducer.
2. Safety.

Issue one is pretty basic. After manufacturing flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after the mechanical fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 and 231 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more.

The other more serious issue is in regards to safety. We want to make absolutely sure that the fittings on the transducers never are subjected to conflicting vibration planes. The engine will flex in the motor mounts creating conflicting vibration planes between the engine and the airframe. This is why the ?flexible line in? and ?flexible line out? is called out so often. This is also why we don?t want the transducer rigid mounted, via a fitting, to a carburetor or fuel pump. A contradicting vibration plane will focus the energy directly to the fitting. It is our sincere concern that with the two conflicting vibration planes here could cause the fitting to fatigue and crack. This would be bad?and we have seen it happen?.

On the bright side, we don?t care if the thing flows straight up, or if you put 90-degree fittings in and out of the transducer. Just don?t mount it upside down, flowing sharply downhill, or before the pumps.

Please let me know if you have any questions or if we may be of any assistance.

Matt Sharp

[Bob Axsom]

I removed the two hoses, capped the sensor ports, installed the old hose and ground ran the engine tonight. I need to reinstall the cowl and hope to make a test run tomorrow. I have to point out that most RV builders would be happy with 183 kt speed, the function was fine as far as fuel flow monitoring is concerned but I want ~190 kts that I had before so the objective is different. I'm sure you will be happy with the performance as I was until I ran the speed test.

Bob Axsom

[GeneL]

Bob I don't know about you, but I am going to have to be under 15gph to finish the 400nm race with half hr reserve. I may be stopping at one of the fuel stops since we will most likely will have a NW wind?? See you in Mount Vernon.

[Bob Axsom]

Originally Posted by GeneL

Bob I don't know about you, but I am going to have to be under 15gph to finish the 400nm race with half hr reserve. I may be stopping at one of the fuel stops since we will most likely will have a NW wind?? See you in Mount Vernon.

I agree generally but this year I am going all out for speed and I fully intend to take advantage of the no penalty fuel stop at Dixon. From what I see so far the wind will be around 10 knots out of 350 degrees with the same thing from the surface pretty much all the way up so fly low stop the clock at Dixon and lose almost nothing on the resume climb out.. Last year I flew with my tip tanks for a comfortable non stop range margin and gave up 3 knots. Finished 4th in RV Blue 1.44 mph behind Jeff Barnes - out of the running. I'm really pushing it this year but my latest speed tests are not encouraging. Here is some semi confidential information on RV entries:

Kevin Phelps 11 RV Blue RV-7A
Alan Carroll 12 RV Blue RV-8
Jon Ross 27 RV Blue RV-8
Robert Axsom 71 RV Blue RV-6A
Eugene Ledda 675 RV Blue RV-7A
Jim Huff 77 RV Blue RV-6
Douglas Shoup 96 RV Blue RV-4
Jeff Barnes 411 RV Blue RV-6TD
Tom Moore 621 RV Blue RV-7A
Tony Crawford 49 RV Red RV-4

Bob Axsom

[GeneL]

Bob, I won't be a threat speed wise, just getting a baseline. If they are truly "no penalty" fuel stops I might stop also?? Is the restart a true flying restart or end of runway start? Good luck, see you tomorrow. Gene

[Bob Axsom]

I've always avoided it with my old fuel burn rates but in order to go full speed with my current burn rate and no tip tanks I'm going to learn the rules on the job. See you there. I see Garry Wilcox has entered the Mt. Vernon 100 this morning - he is fast!

Bob Axsom

[Bob Axsom]

I think I said last night that I removed the cowl changed the plumbing and test ran the engine. I didn't have a lot of sleep the night/day before (it comes in increments at various times without regard to Earth orientation) and it drained me. I still have to reinstall the cowl and prepare for the trip tomorrow but I am holding out for 8 hours of sleep before I jump back into the fire. For those with technical interest that means no disciplined speed comparison test flight for now. I have a good feeling about it but no real information before the AirVenture Cup Race.

Bob Axsom

[Bob Axsom]

The situation kept getting worse until I replaced a repaired LASAR mag with a factory new unit and everything returned to normal. After replacing the mag I ran speed tests with and without the red cube in the fuel system and there was no clear difference.

Bob Axsom