Power Boost Valve

parry

parry

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I drove eddies S3 205 a couple of weeks ago and it seemed livelier that any other 205 I had driven. The only mod was a power boost valve and good exaust.

I am thinking of getting the power boost valve as well, has anybody used them, is there a diference in power?

PA
 
How much can you get a power boost valve for?
I have one on my series 3, it goes wild, i have a spare if your interested..
Make me an offer. It is a 4 bar valve which will swap straight over from the original one. Original valve is only 2.6 bar.
:) :)
 
Adjustable fuel pressure regulators will do very little on a standard engine. By increasing the fuel pressure you can get more fuel through the injectors but what is the point when you haven't changed anything else?

It MAY make a little difference if you had better induction and a freer flowing exhaust system. But I wouldn't count on it making a sizeable difference.

A malpassi reg will set you back about $165. That's what mine is costing me.

Darren
 
My 205 SI is running lean, white plugs and a bit flat in the mid range, better when cold because of the cold start enrichening. It goes a bit better after I reduced the plug gaps, they were way too wide.
It has no doubt an analogue ECU, so a bit hard to change things there, but I was thinking that boosting the fuel pressure might solve the problem.
Does anyone know what type of valve the SI uses and whether an adjustable one could be fitted?

Graham Wallis
 
Unless I'm mistaken, wide plug gap --> weak spark --> less efficient combustion --> richer running. This was a problem in my housemate's Rover, which consistently spewed black smoke until we pulled the plugs and discovered they hadn't had the gap set by the installing mechanic mallet

I think The 205 has a similar Bosch L(E)-Jet system to the EFI 505s, which means there should be an Allen head on the air flow meter box (possibly covered by a rubber cap.) Turning one way will richen the mixture, the other will lean it.

Graham: It's possible your regulator has failed completely, the easiest way to check is to use a fuel pressure gauge that Tees into the fuel line where it enters the fuel rail, and checks that the pressure is as specified/constant. I imagine these are expensive, but most decent mechanics will have one.

I'm with Darren wrt the benefits of higher fuel pressure on a standard motor, pushing more fuel into the combustion chambers will help to a degree, but if there's no more air getting in there then the benefits will be limited.

<small>[ 20 May 2003, 03:33 PM: Message edited by: Gus ]</small>
 
Adjustable pressure, what a Gimmick!!
The standard ones are also adjustable, but they adjust with Vacuum, which means as the rail needs to suck more fuel, the vacuum increases, thus opening the regulator more, it doesn't supply a constant 2.5 bar it may only supply up to 2 bar of pressure, and increases as the engine needs it, if you car is standard, and is running lean, either the regulater is not operating, or your fuel pump is suspect.
 
std. fuel regulators work like this:
at atmospheric pressure. ie wide open throttle, they deliver the full advertised fuel pressure eg 3.0 bar.

Under all other throttle positions there is a vacuum, produced by the engine. Max. vacuum being at idle. There is a vacuum tube linking the inlet manifold to the regulator.

The vacuum produced by the engine is SUBTRACTED from the WOT fuel pressure. So at idle, you might have 0.75 bar of vacuum. Fuel pressure at idle would be 3 - 0.75 = 2.25 bar.

If you add 0.5 bar, via adjustable regulator, or by squashing the regulator in a vice, you add 0.5 bar under ALL conditions. If the resultant mixtures are outside the operating range of the O2 sensor, it will be stinking rich. If the O2 sensor can take care of, then well and good. The only way to tell is to measure the voltage coming back from the O2 sensor.

It is rare that a manufacturer would run an engine lean at WOT. So why add more fuel there? They do however, often skimp at part throttle and/or acceleration, to get through emissions testing. Engines can tolerate weak mixtures under part load, but not at WOT.

So hence the power boost valve. It increases the fuel pressure, when the vacuum drops. When you possibly need a richer mixture.

Using fuel pressure to vastly increase fuel volume is a waste of time, as the volume delivered is proportional to the sqaure root of the pressure

ie
36psi - sq. root = 6
40psi - sq. root = 6.32

6.32/6 = 1.05 or 5 percent

If you need heaps more, you'll need bigger injectors.

If you want to see if your engine is going to benefit from a power boost valve (or richer mixtures somewhere in the rev. range), disconnect the vacuum tube from the regulator. Don't forget to block it off. You will then have richer mixtures under all but WOT conditions.

It's a very cheap way to find out.
 
Yes,I was thinking that the regulator valve may have shifted its calibration giving less pressure and a weaker mixture. By putting on an adjustable one I thought I may be able to get the mixture spot on.
The experience I had with the Autronic System on the 505 V6 was interesting, every adjustment known to man was avaiable via the ECU but a shift in pressure from the mechanical fuel pressure regulator would throw all of this out the window!
Of course the throttle body system on the 205 SI may present an entirely different scenario.

Graham Wallis
 
The standard 205 Gti S1 runs a Bosch 2.5 bar reg. The 'Jaz' engined cars(90 kw 405, BX or 205 S3 engines run a 3.0 bar reg. This will do the same thing as a power boost valve to a standard engine. More snap response, but no power. (The PBV is 65 Pounds out of England.) Not worth it unless you do other work, because it will just cause your standard car to run rich. Maybe it can get rid of flat spots, but it will run rich. On my hotted up 205 motor I originally set it at 3.4 bar feeling it was the best, but the dyno revealed it was running rich. I gained stacks more power when it was backed off to 3.2 bar, which gave the car enough fuel for the mods to work.
Dont waste your money on a PBV in a standard car.
 
Chris (XQ), give one of these uprated fuel presure regulators a go and let me know what you think :cool:

<small>[ 22 May 2003, 07:00 PM: Message edited by: Phasis ]</small>
 
Dont bother witha PBV first up, just get a suitable Bosch 3.0 bar regulator. Takes all of a minute to put on. New is better than used but it depends on the price. Will cost next to nothing I suspect. Dont waste the money on a PBV unless you do stuff to get more air in and out of the motor.
 
So where are these located on the car and where would u suggest I look to track one down?
 
dont waste your money, if you need it get a malpassi adjustable reg, dont waste the extra money on a fancy name.
 
although the 405 does run higher psi reg..not by much...but higher...i still havent heard an explanation for this...basically same motor???i put one on my gti; adjusted afm and i really did notice an improvement; nothing spectacular but a well spent 20 bucks...

cheers
dino
 
Hi Parry,

The Power Boost Valve was a TSE brand I think. From what Paul told me the theory was that it allows higher furl pressure ONLY on 1/2 to full throttle opening, to prevent "leaning out" on redline acceleration runs. To be honest with you, I only felt a marginally improvement...and that was in the smoothless esp. when reving...I think the PBV has limited impact cos the ECU will try to compensate to "some extent" if you try to make it too much fuel pressure and therefore ie. too rich...The PBV IS adjustible easily using 1/4 turns...

One VERY important point...my PUG had the most pronounced improvement not from the PBV but it was the 2" MAGNEX system. and ooops, did a little bird somewhere say that this British system does not connect onto a CAT??? :confused: wink wink wink All the best with the sprints and love to check your car out on the track one day.
 
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