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Injection pressure regulator
vinny1275 - 25/9/07 at 08:05 PM

Evening all,

Well, the collecting of components for the injection / megasquirt setup is going OK, but I need a fuel pressure regulator. Looking on the Bay, there are loads of these: clicky

They do look a bit chavvy, but will they work, and (probably more important), pass the SVA?

TIA,


Vince

NeilP - 25/9/07 at 08:11 PM

You'll just have to mount it in a prominent position or paint it over with black hammerite - Reasonably cheap for the spec...

Agriv8 - 25/9/07 at 08:38 PM

Vinney,

Get one with a presure gauge as this is very usefull for fault finding set/up.

On mine the vacume side is disconnected as the EFI can do a better job of controlling how much fuel to lob in.

personally using an FSE regulator.

regards

Agriv8

oadamo - 25/9/07 at 08:57 PM

get a fse the cheap ones are a pain in the arse to set they have cheap plastic diaframs in.
adam

BenB - 25/9/07 at 09:19 PM

I'd definately get one with a pressure gauge in it- especially on a cheap one. At least you can monitor the pressure so you know when it goes pete tong....

RazMan - 25/9/07 at 10:41 PM

I've got an FSE with gauge - very handy when mapping.

MikeRJ - 26/9/07 at 09:40 AM

quote:
Originally posted by Agriv8
On mine the vacume side is disconnected as the EFI can do a better job of controlling how much fuel to lob in.


If you are running separate throttle bodies this is understandable. However if you have a plenum and a single (or two) throttle bodies and are using a MAP sensor for load sensing then I don't agree. The baseline fueling level on ECU's like the Megasquirt and VEMS assumes a constant fuel pressure for starters.

If ECU's were better than a relative pressure regulator, why would any car manufacturers ever bother with them?

Agriv8 - 26/9/07 at 11:38 AM

quote:
Originally posted by MikeRJ
quote:
Originally posted by Agriv8
On mine the vacume side is disconnected as the EFI can do a better job of controlling how much fuel to lob in.


If you are running separate throttle bodies this is understandable. However if you have a plenum and a single (or two) throttle bodies and are using a MAP sensor for load sensing then I don't agree. The baseline fueling level on ECU's like the Megasquirt and VEMS assumes a constant fuel pressure for starters.

If ECU's were better than a relative pressure regulator, why would any car manufacturers ever bother with them?


Hi Mike as I understand it.

The FSE presure valves ( and similar ones ) adjust the fuel presure in proportion to the vacume in the plenumn, a suction pipe connects the plenumn to fuel presure regulator. when there is a vacume in the plenumn this will make the Fuel presure regulate the fuel presure on the fuel rail.

In my setup I have a Map sensor and a Wide band Lambda.

Why would I want a mechanical device deciding to change the fuel presure on the rail.

My Vems Ecu can do this by opening the Injector longer and looking at the resulting Lambda changes and deciding what to do next.

You may wish to do somthing slightly diferent If I was running full sequential ( I.e. wanting the correct ammount of fuel at the exact moment ) but a better way arround this would be to fit the correct CC injector rather than having the FSE messing arround with the fuel presure on the fuel rail.

I may have it completly wrong. But i am off to discuss on the Vems forum as you have planted the Seed of doupt


Regards

Agriv8

RazMan - 26/9/07 at 12:27 PM

I've always had trouble understanding the need for a vacuum triggered regulator. As Agriv8 says, it would more logical if the ecu was to take complete control but I seem to recall that injector duty cycles are a limiting factor here, and the resolution is easier to calibrate when you can increase the pressure at appropriate times. I am not sure of the reasons behind this though - maybe you can fool the ecu into thinking you have bigger injectors but still keep the engine frugal at lower revs?

rusty nuts - 26/9/07 at 05:07 PM

I think you will find the reason manufacturers use a vacuum operated regulator is down to price £££ ?

chriscook - 26/9/07 at 05:56 PM

Why would fitting another or more complicated part be cheaper if it can all be done in the ECU?

By reducing the rail pressure at low load (high vacuum) you need to open the injector for longer to get the same amount of fuel. This means that you can make small adjustments to the amount of fuel easier at such loads because there is a limit on the resolution of the ecu to be able to control the pulse width.

quote:
Originally posted by rusty nuts
I think you will find the reason manufacturers use a vacuum operated regulator is down to price £££ ?

RazMan - 26/9/07 at 08:27 PM

quote:
Originally posted by chriscook

By reducing the rail pressure at low load (high vacuum) you need to open the injector for longer to get the same amount of fuel. This means that you can make small adjustments to the amount of fuel easier at such loads because there is a limit on the resolution of the ecu to be able to control the pulse width.


That's what I said ..... or meant to say anyway