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SDSFI Fuel Return Pressure Regulator Firewall Mounting?

bluskydreamin

Active Member
Fellow 10 builders using SDSFI,

Where did you or plan to firewall mount the fuel return pressure regulator and return firewall bulkhead fitting?

I have seen some of the EFII regulator mounts but these are somewhat different considering that the EFII fuel loop is lower on the engine around the bottom of the cylinders. I am using top cylinder mounted injectors so the fuel feed and return lines interface on top of the engine....similar to a mechanical injection spider/purge valve assembly.

Considering future access to engine items like oil filter, aux alternator, ignition coil areas and keeping the regulator from seeing excessive radiant exhaust heat is a balancing act. Any pics would be greatly appreciated before I bust out the drill and get myself into trouble.

Thanks!
 
Disclaimer: I have not flown, but the engine has been run.

My fuel pump blockoff plate is a big piece of aluminum angle extrusion. One leg provides the blockoff to the engine, the other provides a shelf for a pair of #6 AN bulkhead fittings. Two flex lines lead from here to the firewall in the normal location. On the firewall, I have two more bulkhead fittings as usual. One of these (the supply) has the fuel line going back to the fuel selector. The return however has the Borla regulator attached directly to the bulkhead fitting. The regulator itself becomes a 90 degree bulkhead fitting, and the return line is simply attached to the outlet of the regulator. No extra lines or hose, and no mounting issues. Very simple.
 
SDSEFI fuel lines and regulator

I have the top mounted injectors. The SDS system will include a fuel block I mounted on the backside of the baffle. The reinforcement plate you see in the picture is actually a supplied drilling guide. I used it to drill the baffles and then to reinforce the installation. Ross was willing to sell me the circular route fuel lines you mention. He felt there was no advantage for vapor lock due to the high fuel pressure. I have found the fuel block supplied to be a cleaner installation and I have no vapor lock issues. The second picture is where I mounted the supplied Borla pressure regulator to the fuel pumps in the center tunnel. This allowed me to have a single MP line run from the engine through the firewall to a manifold in the cabin. That manifold supplies the two SDS MP sensors, the Borla pressure regulator, and the G3X MP sensor.
291i03m.jpg

nmx3t0.jpg
 
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Your installation is very clean Marvin. Nice! We've had a number of people with 390s contact us about EFI and I'm always happy to show them your photos.
 
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Looking at this picture, I simply installed the regulator directly to the firewall bulkhead fitting. (remove the hose and the nipple from the regulator, screw it right to the firewall fitting).

And yes, the above is very clean.
 
As a FWIW, there are alt engine'd a/c with auto style injection (functionally the same as SDS) flying successfully with the regulator immediately following the injection pumps. A single fuel line penetrates the firewall to feed the distribution block at the engine. The MAP line comes through the firewall to the regulator. In these systems, regulator bypassed fuel never sees engine heat since it stays on the cool side of the firewall, and there's virtually no risk of vapor lock since all fuel on the hot side of the firewall is at full pressure set by the regulator.
 
Borla

Looking at this picture, I simply installed the regulator directly to the firewall bulkhead fitting. (remove the hose and the nipple from the regulator, screw it right to the firewall fitting).

And yes, the above is very clean.

I agree that the pressure regulator could have been attached directly to the firewall bulkhead fitting. That actually would have been easier and the hose would have been less expensive. There would have been more room in the tunnel. In other words, woulda, coulda, and shoulda. This must be why people build more than once. :)
 
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As a FWIW, there are alt engine'd a/c with auto style injection (functionally the same as SDS) flying successfully with the regulator immediately following the injection pumps. A single fuel line penetrates the firewall to feed the distribution block at the engine. The MAP line comes through the firewall to the regulator. In these systems, regulator bypassed fuel never sees engine heat since it stays on the cool side of the firewall, and there's virtually no risk of vapor lock since all fuel on the hot side of the firewall is at full pressure set by the regulator.

There are many placements possible on the regulator. All fuel on an EFI system is under full pressure FWF (except maybe a few inches downstream of the reg) assuming the pumps are mounted FW aft as we always recommend.
Nothing can pick up much heat in these few inches. FW aft mounting of the reg will save a bit of fuel line and fittings. Conversely, with the dead head fuel system we generally use, having the reg closer to the fuel block helps purge air or vapor faster if someone ran a tank dry and that's our primary concern with reg positioning. There is less "contaminated line volume" involved which shortens the event.

While many speculate about it, never heard of an issue with FWF vapor lock and our EFI on aircraft yet with 100LL. Most possible issues arise at the pump inlet with mogas and poor plumbing practices- small line, too many 90 degree fittings, improper pump placement or orientation.
 
Clean install

Thanks for the info guys! I see the merits of both install ideas and certainly appreciate the clean work. Do you see any issues down the road potentially with having the MAP port mounted low and vertically?
 
Most of the alt engine installs I'm familiar with are running whatever E-mogas is available at the moment. No vapor lock issues.
 
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