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Mag/Fuel pump blast tubes

What Blast tubes do you have?

  • Mags

    Votes: 73 68.2%

  • Fuel pump

    Votes: 43 40.2%

  • Alternator

    Votes: 57 53.3%

  • I don't need no stinking blast tubes

    Votes: 23 21.5%
  • Total voters
    107
bill@fusion4.net

[email protected]

Well Known Member
Trying to figure out if I should install any blast tubes as I finish up my firewall forward.
Seen some posts of people adding them to mags and or engine fuel pump.
What are people doing/ finding they need on the IO-540 in the RV-10.

Thanks,

Bill
 
I installed the two corrugated tubes as shown in the plans. Whether they are necessary to cool or lengthen the life of the mags, I can't comment on. They don't add any weight to speak of and are simple to install.
 
P-mags require a blast tube. When I replaced my small engine, I didn't add one for the fuel pump or alternator and haven't had any issues.
 
Stock engine/cowling/mags, 60A PP Alt, no fuel pump shroud and no blast tubes.
I installed non-reversible temperature labels on everything. I have not noticed anything over 200F. My cowl outlet max temp was 230F at 16,500' with 32F OAT...I could not believe it either. No problems after two hot summers. I am sure cooling air could not hurt unless it contained rain water.
 
I have the FI high pressure boost pump in the housing by the fuel valve. I didn't feel the need to keep the engine fuel pump cooled with a shroud.
Time will tell! Especially if I decide to try and run mogas.

The alternator and P-mags got the plastic conduit aimed at them.
 
So far we have 92 blast tubes, and not a single credible report of before and after temperatures.

I'm just sayin'.....
 
DanH said:
So far we have 92 blast tubes, and not a single credible report of before and after temperatures.

I'm just sayin'.....
Click to expand...

Dan, Do you have an idea of what temperature these components could tolerate? Certainly the alternator should be subject to the same as electronics, maybe 115 or 130 C, but fuel pump, or mags leaves me blank. Update Added: I sent an email to Champion, maker of Slick mags and a got a very nice reply within an hour!! The Slick mag limit is 185F and measured on the frame near the coil. (I have yet to know exactly where that is). That is pretty low!

I plan on several thermocouples to be available for phase I data collection, but without targets it won't be of much use. Oil cooler and heater output is another matter.
 
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I was trying to figure this out earlier today. Planning to aim tubes at the mags and tube to the fuel pump shroud. Where is the best place on the mags to aim the tubes? Should I do a tube on the Plane Power alternator? What about moisture if flying in the rain?
 
For what it's worth...

This is where I aimed it on my P-Mags, not sure about normal mags...



I needed to aim a blast tube at locaton it did not want to point so I used brazing rod threaded at one end to get it to hold a shape...



There's been a bit of discussion as to whether it's needed or not, but I installed a blast tube to the alternator, with holes in the side pointing directly at the diodes. There is a 1/8 hole in the bottom of the red cap for water drainage.





This is to the mechanical fuel pump shroud...



I also installed a blast tube pointing at my gascolator but did not get a photo. I'm still trying to figure out a shroud, difficult because of the location I chose...
 
Plane power has repeatedly said their current alternators do not need blast tubes unless they are being worked at over 80% load all the time. Below that they recommend NOT using blast tubes. So unless your alternator is old or very over worked, there isn't a need to cool PP alternators. Other manufacturers may have other ideas though.
 
I am looking at their instructions for the AL12-EI60/B, and it states "Install alternator per included drawing. Supply outside ram air to rear of alternator
By the use of 1? scat tube or other suitable ducting."
 
Give them a call and ask them specifically. You'll get the straight scoop on not needing the blast tube for normal loads.
 
I recently had to add a blast tube for the AFS tach pickup that screws into the mag vent port. It had been overheating and stopped reading tach. The blast tube fixed the problem. The trick was getting it to route to the mag and stay in place blowing right in the tach pickup.
 
I used a plastic cap that was protecting threads on something, and wrapped it with some of the red silicone tape that sticks to itself...
 
Blast tubes on mag, fuel pump and PP alternator.
Not easily visible but my blast tube to the mag is directly connected to the housing. Cool air blowing right where it needs to be.
Been flying in some very heavy rain and I don't see an issue.
I have no credible evidence of the effect of these blast tubes except a sense that pumping cool air into a cavity will cool the affected accessories.
What I do have is a very cool running engine and engine compartment with measured temperatures at the firewall averaging 140F on cooler days and 160F on the hottest days.
https://goo.gl/photos/mupxMgNAqzgqAT3J9
The tube connects to the stub on the left.
 
Ron RV8 said:
I used a plastic cap that was protecting threads on something, and wrapped it with some of the red silicone tape that sticks to itself...
Click to expand...

a washer can also be used. add some RTV to adjust the weep hole size. note: if I remember correctly, I believe the B&C alternator fan has been reversed so that it can absorb the cooling air. maybe someone can confirm this.

100_5491_zpswuxraxfc.jpg
 
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