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  #1  
Old 02-16-2015, 02:59 PM
TCONROY's Avatar
TCONROY TCONROY is offline
 
Join Date: Jul 2009
Location: Wilsonville, OR
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Default Sniffle Valve, Throttle cable, and Fuel Flow Xducr

I am building an RV-7 with standard IO-360-M1B from Van's and am running into a few minor issues after installing the exhaust.
1: The sniffle valve rubber hose is pretty close to the exhaust. I am able to angle it rearward with the soft AL tubing but is this going to be an issue? Is it safe to have that soft Al tube so close to the exhaust?




2: The throttle cable (with firesleeve) is almost touching the exhaust. There isn't enough room for the heat-shield that Van's provides. I don't see how the exhaust could be adjusted to allow for more room... ?




3: For those A&P's here...what do you think of my proposed fuel flow transducer (red cube) installation? I've messed with this for quite some time and need to finish this up now that the exhaust is in place. I'm thinking of using an adel clamp to help support the flexible line at the output of the fuel servo. This adds just enough rigidity that the transducer cannot move aft, interfering with the throttle linkage. I haven't seen this done before but several folks in the hangar say its sound. I'd like the opinions of the VAF community.



Much appreciated!
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Last edited by TCONROY : 02-16-2015 at 03:00 PM. Reason: Revise title
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  #2  
Old 02-16-2015, 03:22 PM
Bevan Bevan is offline
 
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Location: BC
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Not an expert here but...

1: The rubber hose is too close to the exhaust pipe. Fire sleeve may help. Also a metal heat shield will help.

2: Fire sleeved throttle cable it way too close to the exhaust pipe. A metal heat shield may not even help here. Is there such a thing as a double shield?

3: The fire sleeve that the red cube is "bundled" with is held together with a zip tie that may not handle the heat your are trying to avoid, thereby reducing your heat shielding. You don't want all that stuff falling down and sitting directly on the exhaust. "maybe add stainless lock wire in several places to do the job of the zip tie. Otherwise, find another method/location for the red cube.

Bevan
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  #3  
Old 02-16-2015, 05:31 PM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Here is what I have done, it’s been nearly 6 years and 500 hours.

1- Installed a 45 degree connector and routed with aluminum line. Zero issues so far
2- Installed a heat shield and fire sleeves just as you have done, no issues thus far
3- Installed Red cube between the electric and engine driven pump inside. The accuracy is within .2/.3 of a gallon in 30-33 gallon of fill up. I compare this every single time I fill up my tank and it has been repeatable without fail. With that accuracy, I think it is not worth the complication of installing in it in such tight spot which can cause other issues.

Mehrdad
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  #4  
Old 02-16-2015, 06:58 PM
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schristo@mac.com schristo@mac.com is offline
 
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Location: WA
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Default good fuel flow sensor spot for me...

This shot has all three

Fuel flow sensor, close to exhaust pipe linkage, and sniffle valve.

The flow sensor has given good results... It died on me and was replaced... I do not have fire sleeve on it now... lots of airflow between the cylinders there and have not had any issue 1100 hours now.

I have the throttle and mixture under the pan form a boss with one very close to the #1 exhaust stack... I have an extension to the cable end so it is a solid piece rather than the actual lined cable so there is no issue with melting the sleeve... lots of airflow here as well.

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  #5  
Old 02-16-2015, 08:01 PM
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tadsargent tadsargent is offline
 
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I took a different route with the sniffle valve. I did not want the fuel dripping on to my cowl then on to the floor, second, the close proximity seemed to to solvable with a Piper 491-091 90 degree angled valve. Extending it with an aluminum tubing was just the ticket.
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  #6  
Old 02-16-2015, 08:12 PM
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schristo@mac.com schristo@mac.com is offline
 
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Default dripping on the cowl???

Quote:
Originally Posted by tadsargent View Post
I took a different route with the sniffle valve. I did not want the fuel dripping on to my cowl then on to the floor, second, the close proximity seemed to to solvable with a Piper 491-091 90 degree angled valve. Extending it with an aluminum tubing was just the ticket.
... dripping on the cowl??? my plans show taking it aft with 1/4 AL tubing just past the cowl opening with an adel at the firewall.

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Last edited by schristo@mac.com : 02-16-2015 at 08:14 PM.
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  #7  
Old 02-16-2015, 10:01 PM
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RV7A Flyer RV7A Flyer is offline
 
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Location: US
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Sniffle valve - used a 45 degree fitting, then aluminum tube all the way back, wrapped in some heat-reflective material I got as a sample from a speed shop or someplace like that (yes, it goes all the way back to the firewall, then bends down a touch and cut at a nice angle to look good).

Red cube - mounted in the same general location, fabricated a steel "L" shape which is mounted to the sump and then then the cube is mounted to that (okay'd by the manufacturer)...no issues, 300 hours. Wrapped in firesleeve just as you have.

Also, whenever I needed a zip-tie firewall forward, I used the blue, high-temperature Tefzel zip-ties. Pricey, but holding up with no problems. (I also used Adel clamps with the high-temp blue cushions on anything on the engine, such as clamping the ignition leads, etc.).
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  #8  
Old 02-17-2015, 02:21 AM
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Taildrgr Taildrgr is offline
 
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On my 7 I put a heat shield at both the sniffle valve and the throttle cable. It is a tight fit at the throttle cable, but it is important to have it.

However, one note about the heat shields is that they are located at the crossover sliding joint.

I had read here on VAF about an exhaust flange failure that was possibly due to a frozen slip joint.

So I contacted Vetterman's and they said not to put the strap of the heat shield over the slip joint. The tight mounting strap could over time cause problems.

So I used the longer 4 inch heat shield and moved the mounting straps so they were outside the slip joint.
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  #9  
Old 02-17-2015, 07:31 AM
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Danny King Danny King is offline
 
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Location: Southlake, Texas
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Default Throttle cable

What you have done with the throttle cable will not work! At normal cruise speed there will be enough airflow to keep the throttle cable from melting, but at low speed the fire sleeve will act just like an oven, and will not save the cable from melting around the inter cable. It will freeze in place when it cools.

Example: Flying at 90k from Ripon to landing at Oshkosh, cables that close to the exhaust with or without fire sleeve will melt! Don't ask me how I know. My problem was with the mixture cable near, but not as close as your throttle cable. The mixture bell crank set up sold my Van's will move the mixture cable out of harms way, but I don't see a fix for your throttle cable short of a reroute of the exhaust. You might consider using a higher quality cable some guys are using that are not the plastic boat cables most of us installed.

I also vote on moving the red cube inside. I put the Doll's cube just after the fuel valve on the suction side of both pumps. I know, it won't work there. RIGHT.....
It works just fine, and has been giving me very accurate measurement for the last fifteen years! While I'm at it....I'll start another fire. No gascolators are required or even desirable in the RV set up. The low point in the system are the tank detains. Try to avoid anything that can act as a heat sink on the firewall side! The Doll has one fuel line running from the firewall fitting to the engine driven fuel pump. That's it! Everything else was installed by Lycoming and came with the engine, or is on the cool side of the firewall.
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Last edited by Danny King : 02-17-2015 at 08:16 AM.
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  #10  
Old 02-17-2015, 07:53 AM
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Default Get sniffle valve from Don at Airflow

I don't know about the second two problems, but I went with a sniffle valve from Don at Airflow Performance. It was about $25, and connected directly to an AN 45 flare fitting to Al tubing. The tubing routs back to the cowling as per the plans and as Christo has done it. No rubber tubing is used.

David
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