B

Bob Axsom

Well Known Member
Since Red Hamilton, Marilyn Boese and I modified the engine with high compression pistons (same displacement - 360 cu in) I can go through a impressive amount of fuel which is fine for racing but for travel I need to cut it back in a controlled manner. Twice on the trip back from Reno to NW Arkansas I landed with low fuel. My thought was to install the EI fuel flow gauge using the "red cube" transducer. So far so good but I noticed that the inlet and outlet ports are 1/4" and my fuel system is 3/8". I talked to tech support at EI and was assured that this small point restriction pressure drop is well within the excess pressure margin of the pump driven fuel systems and will not result in a power reduction. I can rationalize that and for now I am proceeding with the order of the interface nipples but I thought I would ask for tech comments in this forum anyway.

Bob Axsom
 
My experience with the folks at EI is that they are a top notch group of folks. I would trust what they recommend.
 
The EI is STC'ed on lots of planes with 1/2" fuel systems with the same transducer. You should be fine. The RV-10 uses the same transducer with much higher fuel flow than your 360.
 
Are you injected, Bob?

If you are, you will note that the 1/4 inch ports on the transducer match the outlet port on the servo (feeding the flow divider). That said, it is a localized restriction, and it should be as far downstream on the pressure side of the pump(s) as possible to reduce the chance of vapor lock/cavitation issues.
 
Last edited:
When one first looks into the opening of the transducer it seems small but it works. The filter upstream will catch anything that might get stuck in the cube. And even 20 gph is not a lot of fuel to get through it. An hour is a long time for such a test and I'd bet a lot more than 20 gallons will run through without pressure.

I would feel uninformed without a fuel flow indication, have always had one, even back in the '80's with the LEZ and a 0235. In those days an auto unit from JC Whitney worked quite well.

Its primary function for me is setting cruise power. Once you know what speed a particular power setting (fuel flow) will produce, flight planning is quick, reliable and works. You do have to factor in wind but the basic TAS is consistent. With the -7, 8 gph yielded 150KTAS, 10gph 160KTAS. WOT at 75% ran about 11.5 gph and 172KTAS. (all running at peak EGT)

Down low 15.3 gph was 100%. You do see more than 15.3 gph but that is because the engine is running rich for cooling.

Early on I had a problem with idle with the -7 in that the engine sometimes quit after landing. The problem was high fuel flow, it indicated 2gph instead of 1gph. I sent the controller back to AFP for a check, they took it apart, found nothing wrong, put it back together, tested it and returned it to me. I reinstalled it, and worked fine. Fuel flow was at 1 gph at idle the engine did not quit again as before.

Fuel flow was the lead indication something was amiss. It is a worth while instrument in the aircraft.
 
The opening inside the red cube appeared to be approximately 3/16", even smaller than ID of 1/4" fittings. I measured 42 gph with boost pump on, fuel line taken loose at servo inlet and 12' X 3/8" automotive fuel hose ran into container. We're flowing 25.5-26.0 gph on takeoff without issues. My red cube is in the tunnel and is very accurate.
 
Bob, I had the same concern until I performed the fuel flow test on my -6A. The electric boost pump (Facet from Van's) is spec'd at 31 GPH, and that is what I got with the pump on. The red cube did not diminish the flow.
 
+1

I was flowing ~19 gph during Reno last year with a red cube.

The key here is the transducer must be fed fuel under pressure. If it is up stream of any pump, it will restrict flow. The manual is specific about that.


Wait, David-aviator, "at peak EGT" ? Don't you mean rich of peak, or lean of peak if that is your thing? You don't want to run at peak EGT. Probably a typo..
 
N54SG said:
+1

I was flowing ~19 gph during Reno last year with a red cube.

The key here is the transducer must be fed fuel under pressure. If it is up stream of any pump, it will restrict flow. The manual is specific about that.


Wait, David-aviator, "at peak EGT" ? Don't you mean rich of peak, or lean of peak if that is your thing? You don't want to run at peak EGT. Probably a typo..
Click to expand...

Tom,

Pretty sure he is talking about cruising up fairly high, or at least above where detonation is not a player, even at peak EGT. His WOT, 75%, 11.5 gph are what I'm basing that off of, as well as the other FF #s. 75% may be on the fringes of detonation concern at peak, and perhaps that is what you were referring to. If he was talking down low, I'd completely agree with you.

See you in September...where detonation will definitely be under consideration! ;)

For Bob Ax: Looking forward to seeing you explore the world of leaning and setting power by fuel flow, EGT, etc. My bet is you'll have detailed files on speeds, fuel flows and temps for your plane running at various settings. One great benefit is that you'll be able to see your EGT and CHT on all 4 jugs during a race, and can lean or richen for best power along the way. :)

Cheers,
Bob
 
Last edited:
Yes

rvmills said:
Tom,
...
For Bob Ax: Looking forward to seeing you explore the world of leaning and setting power by fuel flow, EGT, etc. My bet is you'll have detailed files on speeds, fuel flows and temps for your plane running at various settings. One great benefit is that you'll be able to see your EGT and CHT on all 4 jugs during a race, and can lean or richen for best power along the way. :)

Cheers,
Bob
Click to expand...

Yes, all of the above. I just got all of the old wiring, probes and instruments out tonight. The new probes are installed for CHT and EGT and the mount is installed on the firewall for the fuel flow transducer. I want to get them completed tomorrow because of some other mods I would like to complete before the race at Marysville on the 29th. The installation is complicated by the angle structure that I use to mount the radio rack on the back side of the panel. My space is so limited that I have to overlap that angle with the instrument mounting face. That requires me to fabricate a partial mounting face spacer and that is further complicated by the two toggle switches in the face of the EGT/CHT instrument. When I installed the SL-30 earlier I had to reorganize my panel switches (remove one and relocate seven) leaving two partial switch mounting holes at the bottom of this location. I had fabricated a cover plate for them that was compatible with the old instrument but I will have to fabricate a new one to cover those old switch holes and provide two new holes to accommodate the instrument switches on the front side of the panel.

The panel configuration almost before the current modification:

a2c289ad-011e-475a-9828-32b5d68f7e8b_zps005a265e.jpg


The new EGT/CHT instrument is going where the old EI digital EGT instrument is in the photo between the Terra Nav and Transponter units and the MAP 360 display (I switched the MAP 360 and the Terra NAV display after this photo was taken - I found I had to have the two GS/LOC/NAV displays together for intuitive operation). You can see the first old switch hole cover plate I fabricated below the old EGT - the new one will have to be larger vertically to accommodate the new instrument toggle switches. The new fuel flow gauge will go where the old EI CHT digital gauge is located to the right of the SL-60 and SL-30 - no problem there.

Bob Axsom
 
Last edited:
I ran all of the sensor wires and connected them to the new probes today

I ran all of the sensor wires and connected them to the new probes today. I'm still waiting for the fuel Flow transducer nippless. Turned out the cover plate for the old switch holes works fine for the new instrument as well - I just had to drill the instrument switch holes in it using the template/drill guide supplied by EI.

I now have an extra couple of 4 probe EI instruments for CHT and EHT if anyone is interested in them as is.

Bob Axsom
 
At 75% power peak EGT is sub optimal. It may well be better than say 50ROP but it is still not Rich enough, or not Lean enough.

Hey Bob, with higher compression pistons you should be able to run the same HP on less fuel, when LOP. Have you considered this? Assuming you have F/A ratio's that will do it.
 
I'm still at an early stage with the engine operation

RV10inOz said:
At 75% power peak EGT is sub optimal. It may well be better than say 50ROP but it is still not Rich enough, or not Lean enough.

Hey Bob, with higher compression pistons you should be able to run the same HP on less fuel, when LOP. Have you considered this? Assuming you have F/A ratio's that will do it.
Click to expand...

I had typed out a long detailed description of the things learned so far but this new computer lost it all when I happened to brush my fingers across the mouse as I went to grab it and my log in had expired. Summary:

We changed a lot beside the pistons even though we did not split the case.

The engine is very powerful and smooth but very different from my previous ~4,000 hrs with O-360-A4M (stock mags) and ~900 hrs with this O-360-A1A (LASAR ignition) before the mods. It does not get rough at peak EGT on the hottest cylinder.

The difference in operation is the primary driving force behind the instrument change - I need to be able to see all 4 cylinders EGT and CHT concurrently all the time.

Careful incremental leaning and switching between cylinders indicates the the peak EGT is approximately 200F lower than before the mod.

When I go over peak and continue to lean at WOT the engine keeps running smoothly but the OT increases and the OP starts dropping and appears to be going in a self sacrificing mode to give all it can even though I'm not giving it the fuel it needs. I have found that if I close the throttle part way and adjust the mixture to give it the fuel it needs for cooling I can get to a 10 to 11 gph burn rate for trips but a slight difference in settings can increase the burn rate a lot. With everything to the wall it will burn 20 gph easily. On the recent trip from Reno to northwest Arkansas I was able to complete the trip in three legs during the daylight hours of June 8, 2013 but lets just say the fuel remaining was scary small at Prescott, Arizona and at home (OK at Tucumcari, New Mexico). The fuel gauges (EI digital - resistive sender) were calibrated (by me) in 2 gallon steps and they are generally accurate but not perfectly linear - that is the driver for the fuel flow gauge mod.

The upcoming AirVenture Cup Race from Mount Vernon, Illinois to Oshkosh cannot be flown at max power without a fuel stop - much agony...

Bob Axsom
 
Last edited:
My speed is off about 7 kts

I am going to remove the Fuel flow transducer from the fuel system and reinstall the old hose to see if that has an effect.

Bob Axsom
 
Possibly an installation (my) problem

I focussed on noninterference routing, elevation, position, stability etc. and achieved all of that but I installed a 90 degree elbow on the input and output to facilitate this nice clean installation. I have been informed by two other racers that I shot myself in the foot. I am going to reinstall the old point to point hose for this weekend's races and work out a better installation later.

Bob Axsom
 
Bob,
You have one flow datapoint from the fellow with the facet pump in the earlier thread @ 31 GPH during his flow tests.

Here is another.
I have the Vans AFP injection boost pump with the red cube mounted after the engine pump and before the injection servo. I got 50 GPH through the red cube during my fuel flow tests. (6 minutes to fill 5 gal jug). I have a couple of elbows pretty close to the red cube too.
 
OK thanks Guys

Speed is king with me and I have lost 7 kts. Out it goes until I can work out a better installation after these races are over.

IMG_7116_zps7f41581c.jpg


Bob Axsom
 
Last edited:
An old post of consolidated info from the horse's mouth:

Mathew Sharp said:
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:cool:

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

Good luck!

Matt
Click to expand...


Mathew Sharp said:
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
Click to expand...


Mathew Sharp said:
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. :eek:

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

Matt Sharp
Click to expand...
 
Fuel System Change Back

I removed the cowl, changed the plumbing and test ran the engine last night. I pulled the in-line fuse for power to the Fuel Flow Gauge. 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
 
I am sure Bob did his installation by the book, so it is assumed it is after the engine diaphragm pump. From another thread, it seems Bob has a carb. Carbs have floats and needle/seat that don't like too much pressure at the needle. An online search yielded .5 psi to 8 psi range for the "fuel pressure". I have to apologize for not digging further, but for the hands-on engine guys, is this right is that at the pump exit or at the needle and seat? If so, is it is the spring in the pump that controls the pressure? If this is the case, we measure fuel pressure on the exit fitting, not downstream of the red cube, so Bob's fuel flow may be pushed by way too little pressure resulting in HP loss.

If a boost pump is used, I missed it somewhere. I have lots of speculation here without knowing what the fuel system looks like. Set me straight.
 
Last edited:
As far as I can tell...

I tried to do it per the EI instructions but I must admit that some writers and my reading do not mesh well. The EI manuals have a style similar to the LASAR timing manual but I tried to be sure I met all the stated requirements in my material selection, fabrication and configuration.

My fuel pressure pick up is off of the engine driven fuel pump in the form of a 1/8" tube connected directly to the fuel pressure gauge in the instrument panel. Typically the fuel pressure displayed from that point in the system is between 6 and 8 psi. I do have an AUX pump in the console before the engine driven pump that typically I use for starting and it drives the fuel pressure to the same level. I have not noticed a casually recognizable change in pressure when the engine driven pump comes into play or when I turn the AUX pump off after engine start.

In the racing world I won three races in a row before I installed the fuel flow transducer with the input and output curved 90 degree hose fittings. In the two races since the installation I've finished 3rd or 4th. I'm prepared to take what points I can get but I would like to see some 220+ mph speeds again. We will see.

Bob Axsom
 
Last edited:
Inconclusive results from today's race

Half way to turn 1 I was passed by Garry Wilcox Which is not that unusual because this Canadian and his RV-7 are blazing fast. But my speed was bleading off down to 154 Kts when I noticed the throttle was over half way closed. I pushed it to WOT and the speed started coming back but I knoticed the knob was back 1/2 inch again. I had not clamped down the friction lock. After turn 1 I passed Garry back again but the damage was done as far as results and concerned. AVC race to Oshkosh tomorrow.

Bob Axsom
 
The results hint that the speed is improved without the sensor

Race # Name Aircraft Class E.T. MPH KTS
Race 35 Mike Smith SX 300 Sport 0:25:50 301.86 262.31
Race 007 Rene Dugas Turbine Legand Turbine 0:25:57 300.51 261.13
Race 21 Alan Crawford Lancair Legacy Sport 0:27:40 281.86 244.93
Race 111 Klaus Savier LongEze FX Blue 0:28:48 270.77 235.29
Race 91 Bruce Hammer Glasair ITD FX Blue 0:29:28 264.64 229.97
Race 73 Steve Hammer Glasair ITD FX Blue 0:31:27 247.95 215.47
Race 14 Wayne Hadath F1 Rocket Sport FX 0:31:28 247.82 215.35
Race 46 Jeff Mallia Cozy III FX Red 0:34:10 228.24 198.33
Race 411 Jeff Barnes RV-6 RV Blue 0:35:22 220.49 191.60
Race 57 Gary Wilcox RV-7 RV Blue 0:35:48 217.83 189.28
Race 71 Bob Axsom RV-6A RV Blue 0:36:01 216.51 188.15
Race 22 Sam Hoskins Q200 Sprint 0:36:48 211.91 184.14
Race 355 John Martino Mustang II FX Blue 0:36:50 211.71 183.97
Race 01 Henry Punzi Mooney M20J FAC1RG 0:37:07 210.10 182.57
Race 193 Bobby Bennett S35 Bonanza FAC1RG 0:37:14 209.44 182.00
Race 77 Jim Huff RV-6 RV Blue 0:37:28 208.14 180.86
Race 83 Dave Adams Long EZ Sprint 0:37:29 208.04 180.78
Race 28 Jeff Ludwig Cirrus SR-22 FAC1FX 0:38:28 202.72 176.16
Race 49 Tony Crawford RV-4 RV Red 0:39:02 199.78 173.61
Race 64 Colin Hogan Commanche FAC1RG 0:39:41 196.51 170.76
Race 115 Michael Estu Glasair ITD FX Red 0:40:52 190.82 165.82
Race 3 Jerry Peck Long EZ Sprint 0:44:42 174.46 151.60
Race 898 Vern Kokosa Grumman AA5 FAC5FX 0:49:23 157.91 137.22
Race 02 Nathan Peck Quickie Sprint 1:00:00 129.97 112.94
 
Still have problems?

Finished 4th again at 209+ mph in AVC Race. E tach display erratic, mouse farts in engine running sound and feel. Probably still have problems.

Bob Axsom
 
No good objective test has been performed after the races.

I went up today to run a speed test with the old fuel line and no fuel flow sensor. The plane is in the same configuration otherwise as the one flown with the sensor in place. It would have given a solid set of comparable data but it didn't happen. The engine missed several times and after I got up to 6,000 ft pressure altitude I thought it wise to get it back on the ground. My panel mounted LASAR warning light came on at least twice so I believe I have an ignition problem that is getting worse. I suspect the sensor mag is the problem and I believe the one that is in there is a repaired unit. I plan on replacing it with a brand new unit, re-time it and see how that works. I am growing distrustful of repaired units. Once I work through this problem and run the test it would probably be a good idea to reinstall the sensor and re-fly the speed test to have a good functional comparison.

Bob Axsom
 
Bob Axsom said:
I went up today to run a speed test with the old fuel line and no fuel flow sensor. The plane is in the same configuration otherwise as the one flown with the sensor in place. It would have given a solid set of comparable data but it didn't happen. The engine missed several times and after I got up to 6,000 ft pressure altitude I thought it wise to get it back on the ground. My panel mounted LASAR warning light came on at least twice so I believe I have an ignition problem that is getting worse. I suspect the sensor mag is the problem and I believe the one that is in there is a repaired unit. I plan on replacing it with a brand new unit, re-time it and see how that works. I am growing distrustful of repaired units. Once I work through this problem and run the test it would probably be a good idea to reinstall the sensor and re-fly the speed test to have a good functional comparison.

Bob Axsom
Click to expand...


Thanks for the update Bob. It keeps us wanna-be's happy. :D
 
Test 8-6-13, new sensor mag fuel flow xducer bypassed

Well I completed the test flight with the new Sensor Mag and the fuel flow sensor bypassed. the two triangles processed in the NTPS three leg spreadsheet yielded speeds of 187.1 KTAS and 183.4 KTAS in that order for an average of 185.25 KTAS. The engine was running good with no small misfires and not a hint of a LARGE MISFIRE like I experienced on the last flight before I replaced the LASAR sensor mag. I flew for 1.2 hours and played with the leaning but I'm convinced it is not right yet. The surface temp was 33C (91.4F) and at 6,000 pressure altitude it was 26C (78.8F). I flew the test at 3,700ft MSL (S/B 6000 dalt according to the USAR handicap procedure). The armstrong test in the hangar last night seemed good but I will check that again when I go back out there later. I would like very much to get the fuel flow monitor back in and run another test but have to impose change control with only two days to go until I fly to Indianapolis.

The results are inconclusive in my opinion.

Changed my mind I'm going to put the transducer back in the fuel flow circuit and fly the race that way. I have to know and to do that I need the test. I'm still 55 points ahead of Jeff Barnes in an RV-6 and if I finish second the most he can gain is 30 points. God this makes me tired.

Bob Axsom
 
Last edited:
Transducer is back in the system

I reinstalled the hoses to the fuel flow transducer the same as before and weather permitting I'll test it tomorrow.

Bob Axsom
 
Xducer in wit 90 deg. connections test results

The conditions for today's test were similar to those for yesterdays test. I used exactly the same test method (USAR handicap procedure, 2 triangular patterns, 6000 ft d alt, Tru Trak Pictorial pilot directional control, Altrack altitude hold, WOT, ROP (tried for max power but I'm still a little uncertain with the new instrumentation), Max RPM 2720 and data post processing with the NPTS three leg spreadsheet.

The first triangle was 186.2 KTAS and the second was 186.4 KTAS. for an average of 186.3 which is slightly better than the straight hose with no transducer in the line. This test configuration used the hoses I made with the 90 degree connectors that incorporate a nice radius to accomplish the 90 degree change of direction I did not use right angle AN fittings to make theis change of flow direction.

That is the the end of the test for me. I found no evidence of a flow restriction that reduced the performance (SPEED!) of the RV-6A powered by a O-360-A1A even with 90 degree change of flow direction right at the red cube interface at both ends.

Sorry the irregular (unreliable) repaired LASAR sensor mag clouded the issue.

Bob Axsom
 
Update

Bob - thanks for taking the time to close this one. I was getting a bit worried about the fuel flow transducer.
 
You must log in or register to reply here.