MSefi.com read only forum (Jan.15,2018)

I am in the process of getting the bits and bobs for the injection system on my Avenger Tiger.

I am a little confused about the fuel pressure regulator. My car runs ITBs but the pressure regulator has a vacuum input for the rising rate. Do i need to tap each runner to provide a vacuum signal for the regulator - bearing in mind the cam has lots of overlap and thus causes all sorts of problems at 'tickover'. Can i just leave the vacuum signal off and thus the regulator would not reduce pressue at tick over/low engine speed i.e. it would be a constant 3 Bar at all engine speeds. Would this be a problem? Or can i get round it during mapping?

Cheers

Nev

While you can run without a vacuum reference, this requires smaller pulse widths at idle because there is a higher pressure difference across the injectors.

nt,

And the smaller pulse widths Matt mentions are harder to control accurately, as well as being more affected by any differences between what you have entered for your opening time and the actual opening time (which can be harder to measure accurately).

So in most cases, you want to vacuum hose hooked up to the fuel pressure regulator.

Lance.

Ok cheers for the answers.

I need to run a vacuum signal if at all possible, good.

However, i am still a little concerned that if my idle, and off idle to around 2500 rpm, produce a very low and erratic vacuum signal would this not cause me more problems than i might solve?

Cheers

Nev

I guess nobody thinks it will be a problem and i should stop worrying!!!!

Your original post asked about the the vacuum reference to the fuel pressure regulator. With your ITBs and high-overlap cams, your vacuum signal will likely be erratic, but I'll bet it will flucuate faster than the regulator can respond, so the regulator will likely put out even pressures based on some steady mean value of MAP.

That said, the question of a source or MAP -- for the regulator AND for MS -- is not indicated. Depending on the signal you send to MS, you might get variable fuel flows (PW) based on an erratic MAP being used in the PW calculations. THOSE variations would be significant and would dwarf any FPR variations. If you have solved the signal-to-MS problem, you surely will have solved the FPR problem and you can sleep well at night. If you have NOT solved the MS MAP-signal delimma, there is much discussion on the boards on that subject.

Yes my question is completely aimed at the Fuel Pressure Regulator. I run my Ignition on RPM and TPS and will do so with fuel as well. I do not have a MAP sensor and do not intend to run one on this engine - Alpha-N for me on this one.

I have now been in contact with another person who runs the same engine as me and he too has injected his. Seems there are only two of us! He found that the FPR would not hold steady so now runs a fixed rate and spent a lot of time mapping.

Cheers

Nev