Fuel pressure regulator
Discussion
Hi Mate
I added a Sytec adjustable FPR to my 350i, The original solid state FPR was set to a max of 36psi...Mine is now adjusted to 38psi @ WOT.
This has given my around 2hp and now have smooth acceleration...The gauge is a glycerin filled type that can be left on the FPR and TBH its a good diagnostic tool that shows up any faults in the fuel rail or pump.
The FSE need the gauge for setting up only and then it has to be removed....however I have heard good things about them......
Ziga
I added a Sytec adjustable FPR to my 350i, The original solid state FPR was set to a max of 36psi...Mine is now adjusted to 38psi @ WOT.
This has given my around 2hp and now have smooth acceleration...The gauge is a glycerin filled type that can be left on the FPR and TBH its a good diagnostic tool that shows up any faults in the fuel rail or pump.
The FSE need the gauge for setting up only and then it has to be removed....however I have heard good things about them......
Ziga
Curious nomenclature...
They're known as 'rising rate' regulators; but they don't increase the maximum fuel pressure (unless you adjust them that way but you could do that with a 'normal' regulator). The standard FPRs drop the fuel pressure when idling and at low throttle openings, these regulators don't drop the pressure as much; so they're kind of 'reduced fuel pressure-drop' devices rather than 'rising-rate' devices.
In playing with megasquirt, I've been surprised how quickly the standard FPR drops the fuel pressure when you're not at full throttle; so what these 'rising rate' things actually do is keep the fuel pressure high and make the fuel mixture much richer for almost all engine operating conditions. Good for power, bad for emissions and fuel economy; I guess Rover were unsurprisingly more interested in emissions/economy than we are!
For wide-open-throttle pulls on dyno a rising rate regulator would have no effect; it's the 'adjustable' bit that would give you more power as you can increase the fuel pressure to whatever gives max power. It would be interesting to see what a 1:1 rate regulator set to a higher fuel pressure would feel like during normal driving when set to the higher fuel pressure to give max power.
They're known as 'rising rate' regulators; but they don't increase the maximum fuel pressure (unless you adjust them that way but you could do that with a 'normal' regulator). The standard FPRs drop the fuel pressure when idling and at low throttle openings, these regulators don't drop the pressure as much; so they're kind of 'reduced fuel pressure-drop' devices rather than 'rising-rate' devices.
In playing with megasquirt, I've been surprised how quickly the standard FPR drops the fuel pressure when you're not at full throttle; so what these 'rising rate' things actually do is keep the fuel pressure high and make the fuel mixture much richer for almost all engine operating conditions. Good for power, bad for emissions and fuel economy; I guess Rover were unsurprisingly more interested in emissions/economy than we are!
For wide-open-throttle pulls on dyno a rising rate regulator would have no effect; it's the 'adjustable' bit that would give you more power as you can increase the fuel pressure to whatever gives max power. It would be interesting to see what a 1:1 rate regulator set to a higher fuel pressure would feel like during normal driving when set to the higher fuel pressure to give max power.
Edited by The Hatter on Friday 31st March 23:43
Hi Martin
Happy to report my 420SE drives really well at super low speeds as well as WOT
She's got the old fashioned original adjustable Weber unit which is not the rising rate one.
The SEAC on the other hand shunts like a good one at low speed and is way happier at mid / full throttle. Can't ID the FPR on that, no markings and I don't recognise it
G
Happy to report my 420SE drives really well at super low speeds as well as WOT
She's got the old fashioned original adjustable Weber unit which is not the rising rate one.
The SEAC on the other hand shunts like a good one at low speed and is way happier at mid / full throttle. Can't ID the FPR on that, no markings and I don't recognise it
G
Wow, some great info there guys, really appreciate it. Sounds like it's the adjustable part which makes the difference, and it is just the low to mid range where i would like to increase performance. Having said that, if it is the adjustable part which matters and you are just making things run richer, is that not the same as adjusting the AFM by altering the spring tension. I did this to make the car run a little richer, which kind of worked, but I couldn't get the car to idle or run smoothly without some shunting, so put it back.
RubbishFettler said:
Wow, some great info there guys, really appreciate it. Sounds like it's the adjustable part which makes the difference, and it is just the low to mid range where i would like to increase performance. Having said that, if it is the adjustable part which matters and you are just making things run richer, is that not the same as adjusting the AFM by altering the spring tension. I did this to make the car run a little richer, which kind of worked, but I couldn't get the car to idle or run smoothly without some shunting, so put it back.
This is why a rising rate is better...The extra fuel will only be called for when the engine needs its, most solid state FPR go from 0-36psi when the vacuum is increased on the diaphragm ...The rising rate steadily increases the fuel volume to suit the changes in the vacuum and demands from the engine.You don't really need a rolling road to set one up as you can simulate WOT by clamping the vacuum from the plenum to the FPR once the car is at normal operating temperature, An RR is however good for fine tuning....And of course knowing what your hp is...
Thanks Guys, I think form all that it's going to be worth doing. Good tip about the fuel lines by the way, although I have had mine checked over couple of months ago, so should be ok on that score; I'll let you know how I get on. Car has had lot's of tlc this winter so looking forward to getting out there in some decent weather and visiting one or two events if there is anything happening up north.
Steve
Steve
Glen, I suspect the shunting at low engine speed on the SEAC will be the cam, not the fuel pressure. I have a similar thing on the 350i with a fast road (long duration) cam, it's crap at low engine speeds due to the cam overlap giving internal EGR (ie the intake and exhaust valves are open at the same time so the vacuum in the plenum at idle/low speed drags exhaust gas back into the cylinder rather than expelling it into the exhaust) - but as you say it's great at medium/high speeds... all part of the fun!
You can't do a lot with a flapper system but fuel pressure is one thing you can play with; I think the adjustable regulators are helpful, but I'm not sure if a rising rate one will give much more than a 1:1 adjustable regulator set to a higher pressure. It's best to fit an AFR meter and watch what happens with the different set ups under part throttle and full throttle, and then decide.
Just thought I'd give an update, finally got around to fitting an FSE regulator. Acceleration generally is better, but the real gain has been in smooth running and throttle reaction. In other words, everything you guys said, so thanks to all. This is a great upgrade and I wish i had done it earlier. Typical though, car is running great and I have done everything I wanted to it over the last 5 years but a change in circumstances means I am now going to have to sell - gutted, but I guess that's how it goes- I have really enjoyed owning the car and help on this site has been invaluable.
Steve
Steve
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