Ed,

If you look around at other regulator brands, you'll find you've got your "adjustable" (meaning that you set the pressure) and your "adjustable rising rate" regulators. Rotary Performance sells the SX brand adjustable regulator, which they claim will flow as much fuel as your pump can throw at it (http://rx7.com/store/rx7/fcfuel.html). Brian Cain, a rotary racer based outside Dallas who posts on that other list occasionally, uses a Malpassi adjustable rising rate regulator. I did a quick internet search but did not turn up any Malpassi vendors outside Australia However, the latter regulator is really intended for turbo applications, where the rising rate regulator is intended as a kind of kludge fix to get the injectors to flow more at the top end. One warning I read was that you have to start your fuel maps all over again if your fuel pressure increases, leading to a richer fuel flow depending on manifold pressure.

One thought I had was that you might be needlessly introducing a complicating variable if you threw on an adjustable rising rate regulator. Wouldn't there be a difference in the fuel pressure you got from your regulator if you were at WOT at 4000' vs WOT at 12,000'? Your manifold pressure would be lower at the higher elevation (without a turbo), leading your regulator to flow less.  I haven't worked out any math on this but on initial reflection it might be a problem in an airplane that auto racers don't face (unless they're in the Pike's Peak hill climb).

Barry Gardner
Wheaton, IL

Ed Anderson wrote:

I think I may have found my problem with the pressure regulator.  Seen below (the Boost Adjustable one is the one I use).  In the description they mention are adjustable from 36-45 psi with a flow rate of 9.2-10.5 gal/hr.   I presume that means the return rate flow or if they mean the engine fuel used flow rate then clearly it is under-capacity to handle our rotary fuel flow.  

 

 The Pump I use (see below)  is rated at 45 gal/hr at 40 psi.  My nominal fuel flow at cruise is 7-8 gph.  If my logic is correct that would mean the pressure regulator would need to dump the unused flow of 45-8 = 37 gal/hour.  Yet, it seems that the regulator unit will only flow a max of 10.5 gal/hr.  Is a return of 10.5 gal/hr sufficient to keep the pressure at 40 psi while using 8 gal/hr?? In fact, would that return rate be sufficient to respond to manifold pressure variations?   I would not think so - but would like to hear what others may have as an opinion or knowledge on the topic.

 

Thanks

 

Ed

 

 

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

 

Fuel Pressure Regulators
Maintaining accurate fuel system pressure on any multiport EFI system is crucial to performance. MSD’s Adjustable Fuel Pressure Regulators allow you to fine tune the fuel pressure to meet the demands of your engine and injection system. Both Regulators are adjustable from 36-45 psi with a flow rate of 9.2-10.5 gal/hr. The inlet and outlets are 5/16” and a jam nut is supplied for special threads on the bottom to ease mounting to a bracket. These rugged Regulators are free standing so they don’t have to be mounted directly to a fuel rail and can be installed in any position. Fuel pressure is set with an adjusting bolt and is locked in position with a locking nut.
PN MSD2220

Boost Adjustable
This Regulator is designed for turbo or supercharged engines. As boost pressure increases, more fuel is required by the engine. This regulator features a boost reference circuit that adds more fuel in relation to boost pressure.
Boost/Fuel Pressure Regulator
PN MSD2222

 

 

 

High Pressure Electric Fuel Pump

Multiport EFI systems require a stable fuel supply to maintain best performance throughout the engine’s rpm range. This high pressure and high flow Fuel Pump features a roller vane pump mechanism which is extremely resistant to clogging and jamming. The pump mounts in-line (out of the fuel tank) with two supplied cushioned clamps for a quick and sturdy installation. The nipple inlet is 3/8” with a 5/16” outlet. The wire terminals feature brass studs for secure connections. Made in the USA, the pump is ideal for use as a “booster” for nitrous oxide applications, or as a stand alone pump for multiport EFI systems on engines up to approximately 500 HP. Capable of 43 gph at 40 psi/162l/h.
PN MSD2225