What is proper fuel pressure, etc ? - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 8 (permalink) Old 01-28-2011, 09:36 AM Thread Starter
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What is proper fuel pressure, etc ?

What is the fuel pressure regulator output?

Just realized in my custom application the fuel pump inside my Polaris RZR tank I am using has a regulator on the output of it and it lists 270kPa which is about 39 PSI. So, the fuel then goes to the RC51 through its regulator ... I am double regulated ... any issues with this? I know other types of regulators only perform well with a high differential pressure but not familiar with these in line fuel type mechanics. Or, perhaps I should eliminate the RC51 regulator since it seems to be one of the most common issues? By chance anyone ever looked to see if removing/bypassing this regulator would be easy? Part of the reason I am also asking this is my custom dyno tuned Power Commander map shows I was way lean from about 30 to 100% throttle (10 to 20 percent more fuel needed in the custom map) so have always had my concern about fuel flow, pressure, etc. It runs fine though with the custom map as far as I can tell but maybe I am missing some power ...

Thanks ...

Polaris RZR with an '04 SP2 transplanted in it. Chain driven through a gear box with axles and CVs. The only thing left stock on the RZR is the frame and plastics . But, the frame is beef'd up too .
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post #2 of 8 (permalink) Old 01-28-2011, 03:52 PM Thread Starter
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Did some more digging at it looks like its 50 PSI. So, if I am only giving it 39 PSI is that enough or is it going to be an issue?

Polaris RZR with an '04 SP2 transplanted in it. Chain driven through a gear box with axles and CVs. The only thing left stock on the RZR is the frame and plastics . But, the frame is beef'd up too .
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post #3 of 8 (permalink) Old 01-28-2011, 04:04 PM
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50 PSI is the normal fuel pressure.
The system is designed around that fuel pressure constant to calculate the amount of fuel needed and the injector open time interval.
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post #4 of 8 (permalink) Old 01-28-2011, 04:14 PM Thread Starter
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So not good if I only have 39 PSI max, correct? Or, since my Power Commander map is really richening it up is that an ok way to compensate for the lack of pressure?

Polaris RZR with an '04 SP2 transplanted in it. Chain driven through a gear box with axles and CVs. The only thing left stock on the RZR is the frame and plastics . But, the frame is beef'd up too .
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post #5 of 8 (permalink) Old 01-28-2011, 04:50 PM
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The system is needing 50 PSI with an expected fuel flow of 190cc/10 seconds.
It doesn't have to come from the RC51 fuel pump.
If you could find an aftermarket fuel pump for a car with adjustable pressure regulator, that should be able to replace the OEM unit.
If it gets the right pressure and minimum fuel flow, it doesn't care how or where it gets there.
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post #6 of 8 (permalink) Old 01-29-2011, 08:30 AM
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By increasing your rich setting doesn't increase your pressure, so no, it won't help.



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post #7 of 8 (permalink) Old 01-29-2011, 12:18 PM Thread Starter
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Thanks. I changed my pump to a 400cc/10 sec and it is 70-100 psi so I should be good now here. Looking into how to remove or bypass the 39 psi regualtor I have and just use the RC51 regulator. Sounding like I might be able to do a bolt tack welded inside the regulator to essentially bypass it by holding it wide open. Will need to go get a new custom Power Commander map done when I get it all figured out.

Polaris RZR with an '04 SP2 transplanted in it. Chain driven through a gear box with axles and CVs. The only thing left stock on the RZR is the frame and plastics . But, the frame is beef'd up too .
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post #8 of 8 (permalink) Old 01-30-2011, 08:22 PM
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How was the tank regulator working, on the return line?

Pressure settings are determined by the design of the injectors I believe which have an optimal pressure for being able to provide good atomization.
Pressurizing gas at high pressure may be problematic. It also increases the risk of a leak that will act as an injector to some hot part of the bike or a spark.
A safe system is a lower pressure pump with higher flow in the tank and a higher pressure pump that meets the flow need of the engine (WFO throttle at high rpm) and no back pressure to the tank past the regulator.
This depends on how far your tank is from the throttle bodies.
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