11 replies to this topic

[Chris M]

I’ve been rebuilding my engine & carried out a few mods along the way. It’s a ‘98 MPI I’ve fitted a swiftune cam kit, a big valve ported head & it’ll have a maniflow exhaust manifold & stainless system. The question is do I need to fit a fuel pressure regulator?
It so why & how would I set it up?

[Bat]

Hi,

You'll need to get it on a rolling road and if it's short of fuel then yes a rising rate regulator will give extra fuel pressure at higher engine loads.

You'll need them to set it up so it's giving the right amount of extra fuel to go with the extra airflow your mods have created.

This is due to the fact the standard ECU cannot be mapped to provide extra fuel for modifications.

Cheers :?

[Fast Ivan]

I would see how it performs with the standard set up, it may be fine, if not see above ^^

[rich_959]

You're running a similar set up to mine (though the engine is sat waiting for a body to go into!). All the posts I read on here and advice from elsewhere suggested the standard fuel pressure is fine (3 bar from memory?). Those who have fitted the regulators have often ended up having them set at exactly the same standard pressure so it seems. 

[Bat]

Hi,

The right type of regulator is key. Most regs are 1:1 ratio, the rising rate or power boost type are a 1:1.7 ratio.

This means as manifold pressure drops, when you put your foot down, the fuel pressure increases 1.7 times compared to the standard regulator. This is where the extra fuel comes from as the injector is still open the same amount of time the only way to increase the fuel going in is to increase the pressure.

Cheers :)

[Chris M]

Thanks for the advice guys. I think I’ll try it first & then decide . ?

[Pete - W.Sussex]

I’ve bought a power boost regulator but I’m still waiting for the (modified similar to yours) engine to come back from the engine builder so I don’t know whether I’ve wasted my money or not but I will definitely get it on the rollers when I get it on the road!

Like you, I have done all the reading and as Bat says there is a certain logic to why the power boost reg would help. The MPI fuel pressure is 3 bar, the ECU will adjust the injector durations based on feedback from the lambda sensor but when you need more fuelling is when you put your foot down on an engine that is breathing more efficiently. So higher fuel pressure at that point will give you exactly that before the lambda/ECU ‘catches up’. The ECU does not measure manifold pressure. At steady throttle the power boost returns to 3 bar so it should be ok with MOT emissions. That’s my non technical explanation probably not explained very well and there are lots of different views but for what it is worth I’ve gone for one and I can’t see that it will do any harm!

[rich_959]

Pete. Bat - thanks for that, both good explanations. As the OP, I guess I'll see how mine runs (still a long way off) and if need be look at a regulator and rolling road session further down the line.

 

Pete, which regulator did you buy?

[Pete - W.Sussex]

This one:

http://www.minispare...|Back to search

[Steve220]

The ECU does not measure manifold pressure. At steady throttle the power boost returns to 3 bar so it should be ok with MOT emissions. That’s my non technical explanation probably not explained very well and there are lots of different views but for what it is worth I’ve gone for one and I can’t see that it will do any harm!

Yes it does. The MAP sensor sits on one of the inlet runners.

Mems works in closed loop at idle, so the base pressure is partially irrelevant for the emissions test. The PBV is only good should the engine be running lean during throttle applications. It NEEDS to be set up on a rolling road as too lean can cause damage and lose power and too rich will cause bore wash.

Edited by Steve220, 22 May 2019 - 09:28 PM.

[Pete - W.Sussex]

Oops! I stand corrected, thanks

[rich_959]

This one:

http://www.minispare...|Back to search

 

Thanks Pete.