LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently December 13, 2018, 4:18 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 12 posts ] 
Author Message
 Post subject: Low cost adjustable FPR
PostPosted: December 14, 2017, 9:18 am 
Offline

Joined: February 28, 2009, 11:09 pm
Posts: 1290
Location: Connersville, Indiana
I'm using an OEM FPR, works fine but it looks like crap and for safety reasons, would like to use stainless braided return line, so universal FPR's look attractive. They seem to come in two price categories, cheap and WOW!. Any good ones in the cheap range?

Bill


Top
 Profile  
Reply with quote  
PostPosted: December 17, 2017, 2:33 pm 
Offline

Joined: February 28, 2009, 11:09 pm
Posts: 1290
Location: Connersville, Indiana
Okay, time to fess up.

Several ago, I purchased one of the cheap regulators. Nicely made, but absolute failure as a regulator. Operating on 70 psi (air) it is impossible to regulate flow. When the adjustment gets to the point that pressure starts to drop, it drops suddenly and shuts off. Will not resume until the adjustment is backed way off, at which point it jumps up to 70 psi. The "jump", or release is so sudden, I can actually feel it. Installed a weaker spring, same story but at a different in the adjustment range. I have taken it apart, everything is clean and really looks good.

Why would a pressure regulator be "sticky" in action?

Bill


Top
 Profile  
Reply with quote  
PostPosted: December 17, 2017, 4:29 pm 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 5921
Location: SoCal
Normally I'm all for building/modifying stuff, but wouldn't mess with a FPR. Just too much on the line: leaks, inconsistent operation, fuel incompatibility, or worst case, suddenly making the engine go dangerously lean.

_________________
Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


Top
 Profile  
Reply with quote  
PostPosted: December 17, 2017, 9:57 pm 
Offline

Joined: February 8, 2014, 10:47 pm
Posts: 492
Location: Cornholio OR "Where the magic happens"
How does steel braided hose increase safety?

The words fuel pressure regulator don't apply to EFI regulators.
They are really pressure relief valves.

_________________
I don't know who I am, when I am somebody else.


Top
 Profile  
Reply with quote  
PostPosted: December 18, 2017, 9:07 am 
Offline

Joined: February 28, 2009, 11:09 pm
Posts: 1290
Location: Connersville, Indiana
The helpful hints are so overwhelming, I don't know where to start.

Bill


Top
 Profile  
Reply with quote  
PostPosted: December 18, 2017, 10:14 am 
Offline
User avatar

Joined: September 22, 2005, 8:12 am
Posts: 1523
Location: 4AGE in S.E. Michigan
Disclaimer: I have not worked on a FPR, but on hydraulic systems it could be the angle on the seat is to steep. Realizing that we are talking 1000 to 3000 PSI Vs 30 to 70 PSI for an EFI. There is a hell of a lot stronger spring pushing on the back the piston seat, which causes it wedge in place on the pressure relief valve. Dave W


Top
 Profile  
Reply with quote  
PostPosted: December 18, 2017, 4:26 pm 
Offline

Joined: February 28, 2009, 11:09 pm
Posts: 1290
Location: Connersville, Indiana
davew wrote:
Disclaimer: I have not worked on a FPR, but on hydraulic systems it could be the angle on the seat is to steep. Realizing that we are talking 1000 to 3000 PSI Vs 30 to 70 PSI for an EFI. There is a hell of a lot stronger spring pushing on the back the piston seat, which causes it wedge in place on the pressure relief valve. Dave W

No angle here. The mating surfaces are a disc and flat seat. About as simple as things can get. I was hoping someone would say, "Hey moron, y'er hooking it up bakards". Speaking of backwards, I tried that. It worked a bit better, took maybe 5 seconds to shut completely off.

Bill


Top
 Profile  
Reply with quote  
PostPosted: December 19, 2017, 12:26 pm 
Offline
User avatar

Joined: March 30, 2011, 7:18 am
Posts: 1446
Location: central Arkansas
Bent Wrench wrote:
The words fuel pressure regulator don't apply to EFI regulators.


They're typically bypass regulators. The high-end carb regulators work the same way, with a return line to the tank.


Top
 Profile  
Reply with quote  
PostPosted: December 19, 2017, 1:02 pm 
Offline

Joined: May 1, 2012, 9:43 am
Posts: 316
Location: Medicine Hat, Alberta, Canada
I would take a look at the shape of the valve seat. It sounds to me like what's happening is that when the valve starts to open slightly, the flow forces it open significantly and the pressure drops off. A good valve would have a bit of taper in either the seat or the "needle" that closes the valve. The needle is often a ball rather than a needle. If it's a flat disc that closes off the flow, then that's probably the issue right there. It would be very hard to control that. Do you have a pic of the internals?


Top
 Profile  
Reply with quote  
PostPosted: December 19, 2017, 2:28 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7563
Location: Massachusetts
You may be right about finding a cheap one. This one is not cheap, but I thought it was good quality. You may be able to find generic knockoffs of this unit. The reason I liked these folks was that if you go through their web site, they hav published graphs of the "error slope" for their units. What that means is it tells you the quality of the regulation, if you double the input volume, the output will change a bit too and they show you what that is.

Whenever you see that type of information it tells you that you are dealing with people that actually designed something and didn't throw it together or copy someone else's work etc. So according to their site the mini fuel regulator is smaller but it has a larger error as the fuel source pressure varies...

https://www.summitracing.com/parts/fue-53501-1/overview/

Maybe your problem is that your source of air is far beyond the units ability to regulate? I don't know why but air is different than fuel and when the unit opens up is is not relieving the pressure so it open too far and jams?

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
PostPosted: December 20, 2017, 2:16 pm 
Offline

Joined: November 13, 2009, 9:31 pm
Posts: 98
Location: Connecticut
Is the unit you have intended to regulate (go in-line between the pump and rail) or to pressure relieve (between rail and a return line) which is more typical.
They function differently and if you are trying to use one for the other, you will have issues.

Operating on air, you may have issues that will not occur with fuel (or water, etc.) based on compressibility and viscosity differences.

Can you describe your test setup? I'm not really following your description of events very well, what adjustment are you making and which pressure starts to drop? If this is a return flow device, there should be no pressure on the outlet line, but you specify working with 70 psi air, so I am assuming you are supplying air from a regulator on a compressor to the inlet of the device, so that regulator will compensate flow until you get outside it's capacity (too much, or to low for it to regulate) and things will get funky fast. Regulators directly in series do not always behave as nicely as they might.

_________________
Planning a Duratec powered, Miata suspended 442


Top
 Profile  
Reply with quote  
PostPosted: December 21, 2017, 8:42 am 
Offline

Joined: February 28, 2009, 11:09 pm
Posts: 1290
Location: Connersville, Indiana
duratec7 wrote:
Is the unit you have intended to regulate (go in-line between the pump and rail) or to pressure relieve (between rail and a return line) which is more typical.
They function differently and if you are trying to use one for the other, you will have issues.

Operating on air, you may have issues that will not occur with fuel (or water, etc.) based on compressibility and viscosity differences.

Can you describe your test setup? I'm not really following your description of events very well, what adjustment are you making and which pressure starts to drop? If this is a return flow device, there should be no pressure on the outlet line, but you specify working with 70 psi air, so I am assuming you are supplying air from a regulator on a compressor to the inlet of the device, so that regulator will compensate flow until you get outside it's capacity (too much, or to low for it to regulate) and things will get funky fast. Regulators directly in series do not always behave as nicely as they might.

BINGO!
Yesterdays posts prompted me to question my setup. Well, I was treating this regulator like an air pressure unit. As Sgt Bowe, my basic training Sgt used to say, "We don''t do it thataway!". The problem was me, not the regulator. :oops:
Properly plumbed into our domestic water system, the little regulator gave smooth response up to its flow capacity.

Bill


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY