1. rrpfr

I've been reading and playing around with rrfpr on a bench for a while now. I have not ran a ski with one yet. I've read alot of people not getting a one to one raise. I'm wondering if the problem is in the adapter that goes on top of the fuel tank.

I recently had a chance to see a rad mount for the gas tank for a rrfpr. It looks like the opening coming from the fuel pump is around 1/8 of an inch. It looks like the main fuel line on the rxp is around 1/4 of an inch. I don't know the maximum pressure these pumps will put out but I'm assuming under 80psi. now based on simple calculations(and I know this does not apply 100% to real life) a 1/4 opening will alow 3.7 times the amount of fuel a 1/8 opening will at the same pressure. if the output of the pump is 1/4 inch and it is forced through a 1/8 opening and than back to a 1/4 opening, there would obviously be a drop in volume of fuel that could pass through that system since the pump will max out as far as pressure goes.

since most people set there base pressure without the ski running, there is no opening of the injector so the base pressure can be set to whatever the maximum pressure the pump can handle since there is no volume. now when the engine runs , in theory by reducing the size of anything from pump to injector will reduce volume which in turn will result in lower pressure at wot.

I don't know the size of the rude but will play with one this week.

I like 05limited homemade setup. it seems like it will produce the best results as far as the most volume of fuel. this would mean higher fuel pressure at wot, which then you could set your base pressure lower. but I don't know how well it will hold up in rougher waters.

2. Very interesting. Let us know if the Rude rrfpr has the 1/8" line going to the pump in the tank as well, or if it is bigger.

3. but in the end, isn't the amount of fuel determined by the INJECTORS, not necessarily the fuel pump - as long as the pump is sending enough fuel to ensure the ski isn't running lean. Example...the RRFPR is a rising rate fuel pressure regulator - so as you throttle up the pressure 'ups'. With 42# injectors, setting the regulator at 60psi with the engine OFF ensures that you are actually presurizing the lines with MORE fuel than the injectors can actually send to the motor at any one time - so you always have more fuel available....

right???

4. Originally Posted by WOT
Very interesting. Let us know if the Rude rrfpr has the 1/8" line going to the pump in the tank as well, or if it is bigger.
It's 5/16

5. The amount of fuel is determine by the ecu, fuel pressure, and injector size. The base pressure doesn't really matter. Its the WOT pressure with the correct AFR that really matters. You adjust fuel pressure for WOT and whatever the base/ idle pressure is what it is.

6. In order to install an o-ring on the pressure in to the regulator adapter the feed hole would be a max of .187. The ID cut for the o-ring is .207.. The boss that the adapter fits into is .322" .

7. I'm seeing some inconsistency in the rude RRFPR. I have a innovative LMA3 hooked up and am recording fuel pressure via a transducer along with several other inputs. The fuel pressure transducer is teed into the pressure gauge on the rude. I am not seeing any increase in output pressure as the boost increases. There basically is no rise at all. Anyone else seeing this issue?

8. beer, I just went and checked. the rude is .158 . 1/8 inch is .125 and 3/16 is .1875 so the closest it would be is 5/32 . if the opening was 1/4 it would allow 2.4 times the volume of .158 and if the opening is 3/16, it would allow 1.37 times the volume.

9. Originally Posted by yacser1
I'm seeing some inconsistency in the rude RRFPR. I have a innovative LMA3 hooked up and am recording fuel pressure via a transducer along with several other inputs. The fuel pressure transducer is teed into the pressure gauge on the rude. I am not seeing any increase in output pressure as the boost increases. There basically is no rise at all. Anyone else seeing this issue?
You can check to make sure the regulator is functioning properly by using a compressor set at 10 psi and using a blower nozzle to pressure up the boost sense hose on the regulator. If you are seeing a 10 psi increase in fuel pressure then the reg is functioning properly. We have been seeing a lot lately where the stock fuel pump is falling down on the job and not flowing enough to provide adequate rise when the ski is on the water and under load. If this is the case on your ski check out the Walbro GSS342 fuel pump. It's a direct replacement.

10. Thanks for the tip on how to test the rude RRFPR. Will give it a shot this weekend and advise. I know there have been some posts on the capacity of the stock pump that I reviewed on this site. It showed the stock pump to have plenty capacity for over 300HP if I recall correctly. thanks again