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MG MGF Technical - Power Boost Valve

Carl, in the thread "On a day like today" you mention an adjustable fuel pressure regulator. Is this what B&G sell under the name "POWER BOOST VALVE" (BGF420).

This is one add-on that doesn't seem to be discussed much these days. After searching the archives, there don't seem to be too many positive comments.

Any comments on its value (benefits) anyone?
(Got a 57i and am looking at ordering the 52mm TB so maybe I should tack this on to the order...)
John Pickup

Spooky I was about to ask the same question!

I thoght power boost valves don't let more fuel into the engine, they just mean the pressure is there quicker, so when you floor it the increased fuel will be available immideatly.

That's my understanding of it too Kingsley.
Rob Bell

Hi John, I have a FSE Power Boost Valve fitted to my mpi,it makes a very noticable difference to your torque in the mid range where you will be running a little lean since fitting the 57i filter(around 3500rpm).Also if you are fitting the 52mm throttle body you will get a dramatic change in your mid range torque.I am down in Fleet this weekend if you want a demo? My mobile= 07967-694185. All the best, Duncan.
duncan dorrell


I'm in Wokingham not far from fleet ! would love to pop over to check this out..if its convienient..


Hi all,
Duncan really said it all , but here is my impression of the FSE : If You have a bog standard car with no options like sports-exthaust etc. the FSE-valve will not impress You! The effect of the valve comes when "everything possible" in bolt-on accessories are fitted. The slight hesitation at acceleration + more grunt at low revīs is then soo clear.... In other words, the power is instant there instead of some slight delay and rubber band feeling.
There is an excellent DIY-explanation on Dieterīs site.

BR, Carl.
Carl Blom

Too early in the morning =:). Should of course bee the dissaperance of the slight hesitation at acceleration....
Carl Blom

As far as I know the power boost valve maintains constant fuel pressure as opposed to the standard system which regulates it. The result of this is not more power but better throttle response. I believe that one of these will deal with the lag problem you get at low revs after fitting a decent air filter and performance exhaust. The cost is higher fuel consumption.

If you get one let us know what difference it makes as many of us never got round to fitting one for one reason or another.

technical data, seems to describe the problems i have exactly. too good to be true??

paul weatherill

The MEMS is only so adaptive, and it regulates the fuel thru the injectors, knowing the pressure behind them (fuel line) the PBV incresses this pressure and therefore the maximum amount of fuel that can pass thru the injectors- I don't know how this effects the MEMS, it probebly buggers its version of the map, but as the map is lean I don't spose it hurts to much (in fact a rich engine is better than a lean one). A better result would be by changing the ECU!

Will Munns

Valves have two functions. One is to allow an adjustable base level fuel pressure which can be set higher. e.g 0.5 bar pressure increase with K series MPI injector (not VVC) will see an increase in fuel flow from approx 160 cc's per minute to 180 cc's per minute. The second function is to increase the speed and rate of change of fuel pressure in reaction to changes with inlet manifold pressure changes that occur with throttle movement.

Where your entering into a full load situation with wide open throttle then the ECU is in open loop and so will take all the fuel it can and operate on the basic premise of what is in the base map will be what is delivered. No adaption.

When the car is operating at a lighter throttle then the system will enter closed loop and so the feedback from the lambda sensor in the exhaust will see changes to the injector open time within a much wider range. The system is adaptable here.

Basic system parameters takes account that the pressure regulator is a mechancial device and so will have mechanical tolerance and over time the characteristics and perfromance of the item will change. To this end whilst the MEMS system data shows fuel pressure as being a nominal 3bar, the reality is that the system is geared to accept between 2.8 and 3.2 bar. I have used the latter setting to good effect and retained normal operation.

Roger Parker

So would adding a PBV on a following car show good improvement?

It's a VVC
with TT exhaust
8.5 HT leads
K&N 57i kit
Trophy Throttle body

Cheers, if it's that good, I am interested.

Hanah Kim

Hello Hanah,
In a word,YES! Get one fitted,you will not be dissapointed! Pipercross Viper kit will make you even more impressed!



this wasn't me with that website, but Nikolaj. I only helped installing and took the pictures.

Hanah, no DIY 4you ;)
Better take it to your mechanic.

@ Carl, disn't you promise to see fo chearish alternatives ?

Dieter K.

:-) Ok thanks. I am waiting for Mike Satur's reply as B&G charges too much delivery fee (3 times Mike's).

Not sure if Mike keeps it in stock tho...

>>Hanah, no DIY 4you ;)
Better take it to your mechanic.

What!! Are you dissing me Dieter? :-) Yeah I know.. my trusty mechanic will do the job. I don't think I can handle the pressure (pun intended)


(i am tossing between getting the PBV or registration number 'TOY MGF' or 'I HAN I'. Can't decide between the two.)
Hanah Kim

Hi Dieter,

Yes, there are some alternatives to the FSE but the quality of that thing was up to my expectations a long time ago when it was fitted to a Porsche... So IMO it is well worth the price. The usual trick is to get an original (or from any other FI car - they are all more or less the same !) and "shim" the spring or even make it adjustable with the aid of a setting screw and also add a small fuel pressure meter. One can see several cheap but reliable DIY oneīs at trackdays etc. But converting one is NOT a simple kitchentable DIY... :(
Maybee I will make up a description and some pict. for Your site. Donīt remember but did I send pict of the re-arranged ignition coilpack on my VVC ?

BR, Carl.
Carl Blom

I did not want to fit a Power Boost Value as I was worried about Bore wash. This is when too much fuel jets pumped into the bore and washes the oils that surround the bore. This causes premiture engine wear. However I had to. I have a lot of bolt on goodies, like K&N, SP exhaust, Icon, TB, Anti CAT and Cams. The car run very lumpy on tickover. Surprising enough the PBV stopped it. I was thinking I would have to get a full engine management system.

Did it make a difference to power? A little on acceleration.
Steve Kemp

Surely, under steady state, no more fuel should enter the combustion chamber, based on negative feedback from the lamda sensor???
Rob Bell

This thread was discussed between 31/10/2002 and 04/11/2002

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