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10-07-2014, 01:32 PM
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Join Date: Mar 2009
Location: Grand Rapids, MI
Posts: 1,004
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Interesting discussion!
I have often wondered why the fuel injection system is mounted on top of the engine and not on the bottom where it would be cooler when the engine is stopped. Has there been any thought towards this? Just assumed there is a good reason seeing how all engines are set up the way they are.
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Paul K
West Michigan
Unfortunately in science, what you believe is irrelevant.
2020 donation made, exempt but worth every dime!
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10-07-2014, 01:33 PM
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Join Date: May 2006
Location: Houston
Posts: 2,012
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Quote:
Originally Posted by Toobuilder
2 random thoughts:
1. They make fuel line insulation blankets for race cars that simply slip over the line and is velcro'd in place. Check with Summit Racing, et.al.
2. There are many Bendix equipped airplanes that idle (relatively) fine. I've had 3 in a row now and I've never had any die at a low idle. I'd be looking hard for any problems specific to your aircraft before trying somewhat "unconventional" fixes.
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Good information and points - thank you! Mine doesn't die. It idles a little inconsistently and pops/backfires occasionally.
Update - I found a similar product that is much cheaper. Will give it a shot and see. Can't see a downside. The point here, as I see it, is to buy some time between start-up and takeoff *after start up and the engine is already warm/hot*. (The time when the problem is pronounced.)
My hope is that this product might keep the lines from heating as quickly while the engine goes from warm to much hotter, taxiing for takeoff. If not - I'm out $25.
http://www.amazon.com/Thermal-Zero-Temperature-Exhaust-Aluminized/dp/B006TIOEGS/ref=sr_1_1?s=automotive&ie=UTF8&qid=1412720000&sr= 1-1&keywords=1%2F2+aluminized+sleeve
Last edited by Low Pass : 10-07-2014 at 04:45 PM.
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10-07-2014, 06:32 PM
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Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,357
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Quote:
Originally Posted by BillL
Doesn't this mean that there is a calibration solution as opposed to a design solution? I am just recalling some previous posts that mentioned a method (spring) to increase the pressure to the distribution block (spider) that largely eliminated this issue? It seemed to be the drain back diaphragm spring in the distribution block that gave higher pressure drop and therefore higher liner pressure up to the block.
Maybe the question should be: How is the Bendix design/calibration different that it presents this behavior?
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Maybe the IO-320 had fuel injection nozzles with smaller orifices then the ones on the IO-360 . The smaller orifices would require higher fuel pressure in lines to produce a given fuel flow, and the higher fuel pressure would increase the temperature required to boil the fuel.
The downside of smaller nozzle orifices is that they limit the maximum fuel flow, so while they might be a solution on an IO-320, they are less workable on engines that require more fuel flow for take-off.
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10-07-2014, 08:26 PM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,333
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I'd be nervous about the insulation introducing new vibration modes, which could be mischievous. An 1/8" OD tube vs an insulated diameter of perhaps 3/8" to 1/2" is a big difference. It's pretty windy in there...
As others have mentioned, investigate if you system will still deliver full fuel flow at WOT, but with smaller restrictors in the nozzles. Consult with the system manufacturer to get their opinion on what restrictors they may suggest would work. If you go to smaller restrictors, verify that WOT fuel flow is unchanged.
It is also not clear if leaning or full rich is better for idle, there are arguments for each being a better choice, depending on what is causing the idle problem.
I just ignore idle problems, which for me generally only show up in ~80F or warmer days, after landing. Sometimes I'll have to occasionally "goose" the throttle to clear things when taxiing in.
Fixing ground idle is not worth adding any additional risk to flight.
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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10-07-2014, 10:12 PM
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Join Date: Mar 2008
Location: Ramona, CA
Posts: 2,370
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Quote:
Originally Posted by AlexPeterson
I just ignore idle problems, which for me generally only show up in ~80F or warmer days, after landing. Sometimes I'll have to occasionally "goose" the throttle to clear things when taxiing in.
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Well, here in sunny SoCal, it has been over 80F every day since February.
I went up again today and after taxiing in the engine stopped again on the ramp when my idle dropped below 900 RPM. It took two tries to get the engine running again just to get off the taxi way. I had the wheel pants off this weekend and the brakes seem to be wearing OK, but I doubt if I will get more than a couple hundred hours on them at this rate.
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10-08-2014, 02:02 AM
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Join Date: Nov 2005
Location: Snohomish, Washington
Posts: 699
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Quote:
Originally Posted by Toobuilder
2 random thoughts:
1. They make fuel line insulation blankets for race cars that simply slip over the line and is velcro'd in place. Check with Summit Racing, et.al.
2. There are many Bendix equipped airplanes that idle (relatively) fine. I've had 3 in a row now and I've never had any die at a low idle. I'd be looking hard for any problems specific to your aircraft before trying somewhat "unconventional" fixes.
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A friend and I tried insulating the fuel lines on his airplane and found it did NOT help, if anything it made the problem worse. So we removed the insulation. My theory is it also insulated the lines from the little bit of airflow they have. I mean when you think about it you have metal injectors screwed into 300 degree plus cylinders and the spider bolted to the case all of which are absorbing a lot of heat.
__________________
Don Jones
Technical Support Manager
Dynon Avionics
CFI-IA, AGI, IGI
RV9-A
Last edited by Don Jones : 10-08-2014 at 02:11 AM.
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10-08-2014, 03:42 AM
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Join Date: Aug 2005
Location: Pasadena CA
Posts: 2,484
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Quote:
Originally Posted by bruceh
Well, here in sunny SoCal, it has been over 80F every day since February.
I went up again today and after taxiing in the engine stopped again on the ramp when my idle dropped below 900 RPM. It took two tries to get the engine running again just to get off the taxi way. I had the wheel pants off this weekend and the brakes seem to be wearing OK, but I doubt if I will get more than a couple hundred hours on them at this rate.
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Having it die is another matter all together. Do you have a low-inertia prop? Still, it should idle down to at least 600 or so. I'm wondering if you don't have another problem, like a bad flow divider.
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Stephen Samuelian, CFII, A&P IA, CTO
RV4 wing in Jig @ KPOC
RV7 emp built
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10-08-2014, 09:18 AM
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Join Date: Mar 2008
Location: Ramona, CA
Posts: 2,370
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I have the Sensenich Ground Adjustable composite prop, which is lightweight.
I also have the .022 injector nozzles for the AFP FI on the IO-320. It runs smooth as silk above 1000 RPM cold or hot.
At 1000 RPM taxiing, I'm moving pretty fast! This is the main issue -- having to ride the brakes a lot to slow it down.
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10-08-2014, 10:04 AM
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Join Date: May 2006
Location: Houston
Posts: 2,012
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Quote:
Originally Posted by Don Jones
A friend and I tried insulating the fuel lines on his airplane and found it did NOT help, if anything it made the problem worse. So we removed the insulation. My theory is it also insulated the lines from the little bit of airflow they have. I mean when you think about it you have metal injectors screwed into 300 degree plus cylinders and the spider bolted to the case all of which are absorbing a lot of heat.
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Interesting. Thanks.
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10-08-2014, 11:08 AM
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Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,589
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WE built some -4 hoses for a customer several years ago with firesleeve. Electronic injection, but never the less, it was insulated. Pretty cool looking.
Tom
__________________
Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com, www.asflightlines.com
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