I have a 1" hose that goes to what I think is the regulator/rectifier. It's been so long since I've done any engine work I don't even remember what the components are now!

Anyway, I wanted to route this to a NACA scoop on the side of the cowl, but I can not find where to buy a plastic or fiberglass NACA scoop for a one inch hose. All of them are for a 2" hose.

What did you all do? Where are you getting cooling air from? My cowl is ready to paint with the exception of maybe adding a nana scoop, so I'd like to figure this out ASAP.

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You sure you need cooling air to the regulator?

The UL Power install kit comes with all the plumbing for it so I'm guessing that's a 'yes'!

Mark, most installs I've seen pics of (including mine) take air for that blast tube to the R/R from the rear of the left cylinder bank.  Use a one inch flange for ducting https://www.aircraftspruce.com/pages/ha/flanged/ductflanges.php cut a hole, rivet flange, clamp hose, done.

David is right - it was the way UL instructions said to install the cooling hose.  I did mine on

the right, but it doesn’t matter which side.


Dave does your side nacho scoop go to your cabin heat?


It looks like you mounted the voltage regulator to t he backside of the ignition module. Per the UL Power rep at the last open hangar, that will burn up the regulator. The voltage regulator needs to be mounted to the firewall with thermal paste behind it. Also, if you take the air from a flange at the back of the engine baffle, you have pre-heated the cooling air. Why would you want to do that?

Either mount a 1 inch flange to the air scoop in front of the left cylinder bank (this is what Zenith ended up doing AFTER they burned up 3 regulators), or use a NACA vent on the lower cowling and then a 2 inch flange ($10) to the regulator baffle.

Arthur,  Not doubting anything you say here, but there are probably several of us who mounted the

regulator on the backside of the ignition module.  I used Homebuilt Help videos when I installed my

engine and that’s the way they did it.  I also read the UL installation manual and it said “firewall (or

elsewhere)” and that the back of the regulator against metal to help dissipate the heat. It did say you

could add thermal material to help with that.  I did mount my regulator off to the side (not directly opposite

of the modules) but the modules are spaced from that backing plate and I didn’t see them an issue.

Also, the manual shows the hose flange  mounted as David’s picture shows and my thinking is that the 

forced air at that location has not passed by the cylinders yet so shouldn’t be all that hot.

   I only have 140 hours on my engine so time will tell if I have it wrong.  My manual was from 2017 and

it seems like they should have been more specific if it was that big a problem.



I bought my engine in 2019 and consulted with the UL Power rep at the open hangar last fall. I noticed that the installation on the Zenith factory plane did not match the Zenith installation instructions.

Please note the regulator position (6182) on the firewall and the cooling source position (6199) on the Zenith factory plane with the UL Power engine on the attached pictures. Now note the original regulator position indicated by the extra holes in the ignition mounting plate (6183) and the original cooling air source (6183).

Why do you  think Zenith moved it?


Thanks Arthur,

  I just hadn’t realized it was a problem.  I need to do my condition inspection in

April so I’ll look at changing it.  Glad for this forum, I never stop learning from other


Arthur, those are good ideas!  The R/R is actually offset aft and off the plate holding the ignition module and heat pasted.  I hadn't considered using an alternate air pickup location/source...makes sense to me subjectively.  Would be interesting to quantify the ram air temp rise is from ambient thru the baffles to the R/R blast tube somehow.  Either way, it couldn't hurt to locate to the firewall and blast with ambient outside air direcrly.  Cheers!  


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