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PostPosted: Fri Sep 14, 2018 2:47 pm 
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Joined: Sat Jul 15, 2017 5:35 pm
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Location: Abingdon Oxfordshire
A couple of weeks ago a question arose regarding a fix to a little gadget called FILTER KING. My response questioned the validity of the claims made of it based on general engineering, interpretation and just plain and simple basic physics. In my response, that was met with a few disbelievers. Here’s a fuller explanation of my physics and engineering bent. I don’t expect everyone to take this on board, understand or even believe what I’m about to say. Especially if you’ve just spent £60 or so on this miracle cure-all.

I used the words fuzzy logic earlier which some seemed to imply that I was being insulting. Not a bit of it. Others used the term snake oil. So first, let’s look at what I meant by fuzzy logic. It’s a hard thing to describe so I’ll explain it with an example of simple schoolboy fuzzy logic.

Tell your kids that you have just discovered that you have not 10, but ELEVEN fingers. Show them your right hand and count the fingers backwards……., 10, 9, 8, 7, 6…….. and then add the 5 from the other hand……. Which gives you ELEVEN. Yep, there it is for all to see. Mathematically, there’s your eleven…..! You’ve arrived at the figure alright but factually, it’s incorrect because the working out is based on fuzzy logic.

Let’s look at this gadget. But first a confession. Many years ago when these little wondrous gadgets first hit the shops in the late 70’s(?), my friend Don Chapman, MGB GT owner, living in Thatcham and scribe for a couple of popular motoring magazines of the era, was asked to try one of these little gadgets for the motoring supplement of one of them. The gadget was supplied by a motoring shop close to the Clock Tower in Newbury. So far, so good.

The claims were, well….., marvelous but a bit ‘wishy–washy’ as you’ll read later. Clearly trade descriptions, transparency and honesty were not the rage then but, as now, a bit of what’s politely called ‘obfuscation’ was OK as you can clearly read. We weren’t able to get into the guts of the gadget but as you can see from the sales blurb we had a pictorial inside view. So from that we could see what was involved. In short, it was a secondary fixed (but manually adjustable) through-valve, one size fits all, spring loaded diaphragm sat atop a filter in a fuel bowl. Nothing more or less

By now, ignoring the additional filter, we, including triple carb University Motors Downton MGC owner John Richards, were already questioning why on earth does one need a FIXED valve in the fuel line, when there is already a known, good, workable self adjusting, self regulating valve already in the fuel system……… You couldn’t make it up. As things stand and to simplify things, think of your household toilet. The water (the petrol) flows into the cistern (the fuel bowl). As soon as the cistern/fuel bowl is full, the ball-cock (the float) lifts and causes the arm to seal the inflow of the water (fuel). With me so far…….. and stay awake at the back……

Short flush and a small amount of water goes to flush the bowl. Little blip of the throttle and a small amount of fuel goes and does what it does. Needle valve allows the same(?) volume of fuel to top up the fuel bowl. Give the car a bit o’ welly (or a BIG flush of the cistern) and the fuel fills the bowl quicker and as such the pump keeps up with the demand……fills fuel bowl…… needle valve shuts off, stops flow, pump stops and so on - and on - and on. That’s it, that’s all (basically) there is to it. It is an effective variable flow, self adjusting valve. Well maintained, it’s fuel tight and efficient.

Then there are the claims made for this gadget. Let’s look at them – and make sure that you’ve got an advert for ladies hair shampoo nearby for a comparison of the absurd statements, such as ‘…luxurious volume…..’ and ‘…..touchably full…..’. I mean….., they don’t fool you do they? And neither should the horse manure claims made by this gadget. Let’s look at them
Regulates the pulsation of the fuel pump
No it doesn’t! It’s 10 feet away from the pump! The pump is a pulse machine…., that’s how pumps work. You can regulate a pump (a power washer and infusion pumps are good examples). But the SU pumps on our standard cars pumps when ….. anyway. And if you don’t believe me, even your heart does EXACTLY the same. That’s how your doctor takes your……, er……, pulse!!!!!!!
(And talking of which, although it doesn’t say so - but it might as well have - you will NEVER get more pressure than your fuel pump can supply)
Prevents unpleasant air bubbles
WHAT…..! Where are these unpleasant air bubbles coming from for heavens sake and what’s so unpleasant about them. If there are any in the system, then you need to ask how they got there in the first place. On our Mini, it’s a gravity feed to the pump. And quite how these unpleasant bubbles have overcome the laws of physics and nature must remain a mystery. Anyway, the pusher pump, pumps the fuel forwards. The bubble-less fluid just goes the way that it’s always gone. Into the fuel bowl. Unpleasant air bubbles……, where do they get these flowery worded pamphlet writers from?
Reduces the formation of carbon residues.
Spare me..... Pure and absolute horse shi……, manure. It does nothing of the sort. Now, I’m no chemist but pray, tell, just how can this gadget perform this miracle of science? After all, your car now fitted with this magical gadget is still burning the same petrol in the same engine unless I’m missing something. It’s not just an indefinable statement, it is pure guff
Diminishes he danger of fires in the car
I’m already losing the will to live. The flowery word there is ‘diminishes’. Diminishes by how much - and how if the car is already well maintained? By definition, it’s flammable fuel in a closed system. So in what way CAN it diminish the danger of fires in the car. The petrol and other flammables are already there
Improves the performance of the engine
Improves what exactly? Top speed, efficiency, acceleration, warm-up time, thermal efficiency of the oil – or what. And how can it. Put very simply the engine runs on the fuel that is delivered. If it’s insufficient, then you’ll feel it. If it’s too great, you’ll feel and see it too. The engine gets and takes what it needs from the fuel bowl. If the engine needs a bit more, the needle valve remains open to let more in. It needs less, the valve stays closed for a bit longer. It does this thousands of times on the journey
Vigourises your worn engine.
Just joking…. No, it doesn’t say that – but it might as well, in keeping with the remainder of the pure guff
Enables fuel savings from 5% to 10%
Well just let us all SEE not only the independent laboratory test reports but the true road test reports too. Strange that despite a bit of a google search, I can’t find any
Gives regular and constant idling
Oh, deary me….. Any well maintained car will give you this. This is down to a well maintained fuel system and not another valve and fuel filter
Makes easier driving in long queues
Sorry, but this farcical play-on-words nonsense MUST end soon….., please spare me the torment before I loose he will to continue
Prevents overflowing of carburettor
No, no, no….., the bloody fuel bowl needle valve (or whatever you’ve got) does this. No fuel bowl cut-off valve, then the fuel return pipe does the same job
Filters with a high capacity filter
Hurrah……….., we got there in the end. Yes….. It contains a filter. You could simply remove the superfluous crap and just keep the filter because that’s all it REALLY does. But you don’t need to spend £60 to get a fuel filter

It doesn’t end there either. Elsewhere they’re talking about……… I could go on…. it’s all intelligible mumbo-jumbo. Even Diane Abbot talks more sense than this. Or maybe not…..

So, given that, what would I need a fixed pressure valve for, albeit a manually adjustable one, when I’ve ALREADY got a variable valve that’s integral within the existing system.

Now, you’re going to say to me that that’s all very well but sometimes we need more fuel and pressure at the engine than the little SU pump can deliver and the needle valve can restrain. You might, but this ain't going to cure it. Remember Don using his MGB as the test bed, John wasn’t game to test the same gadget on his monster triple SU carb Downton MGC. But I had an MGB GT V8. Now if anything should prove the worth of this gadget, it’s an MGB GT V8. Docile as a kitten at low speed but a raving fuel guzzling monster at HIGH speed. But hold on……..

We didn’t even need to bother. The mighty MGBGTV8 had the same SU pump as the MGB and virtually identical to our Mini’s. It also had a couple of big HIF SU carbs. If it’s volume of fuel you need, the little SU pump will deliver it. It does it well enough at 128mph on the V8. If you’re worried about the SU’s needle valves failing to restrain the pressure, feat not! Those same needle valves did all you ever needed.

In short, it's a frill if not a total fraud. Just my opinion of course and I’d appreciate positive or negative comments, backed up with facts of course

Last edited by Peter Laidler on Fri Sep 14, 2018 2:56 pm, edited 1 time in total.

PostPosted: Fri Sep 14, 2018 6:03 pm 
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Location: Cambridge, MA, USA
"Regulates the pulsation of the fuel pump. No it doesn’t!"

Don't take this personally Peter, but I think you've missed the point somewhat. Unlike a toilet bowl which is open to atmospheric pressure as its balance, this is mostly a closed system.

As far as I understand it, normal operation of the carb is to create a partial vacuum in the choke tube due to the air flowing over the jet hole. This sucks fuel from the bottom of the float bowl at a steady rate, based on engine RPM.

The needle valve attached to the float will be either open or closed, depending whether the chamber is full or not at any particular time. Incoming fuel from the pump, via the needle valve, is used to balance against the vacuum, to keep the system in equilibrium.

(Yes, there is a small pinhole above the needle valve, but it's more of an overflow and not nearly large enough to keep the system in balance in my opinion. I think it's there more to allow things to balance out on much longer timescales that we're dealing with on the engine strokes)

The problem as I see it, is that when the needle valve opens the free space in the float chamber is replenished by fuel, which is injected directly AT FUEL LINE PRESSURE. As the SU and similar fuel pumps provide pulses not smooth flow, so the pump's power and idle strokes result in a cycle of pressurization and de-pressurization of the float bowl. i.e. surging.

Since there is nowhere for the surge pressure to be relieved, the pressure in the choke tube up to the jet has to match the incoming fuel pressure, resulting in over-fueling of the mixture when the fuel pump is on its power stroke - i.e. too rich. When the fuel pump is on its idle stroke, the opposite - lower pressure in the float bowl works against the vacuum from the choke tube, resulting in under-fueling of the mixture - i.e. too weak

On small capacity engines, or at low revs, this doesn't matter nearly so much as the needle valve will be closed most of the time. But on performance engines at high revs, the relatively small capacity of the float chamber is struggling to keep up with demand of the engine, so the needle valve is open a significant longer amount of time.

Since the cycle time of the SU fuel pump is on the order of 1/4 second, and the cycle time of the engine demand is on the order of 1/100 of a second (assuming 6000 RPM / 60s) you can see the fuel pump has a very large effect on the engine behavior as for 25 engine cycles will be overly rich and the next 25 will be overly weak. That's not good...

Adding any kind of regulator in between the fuel pump and the carb effectively provides a damping of the fuel surges. Modern cars achieve the damping by having a fuel pump which is over specified for its required flow, and a return pipe so that 'unwanted' fuel can be dumped back into the tank.

I'm not too familiar with this particular King regulator, but it appears to be using a secondary adjustable sprung valve to cut off the feed from the fuel pump, essentially a restrictor plate with a fixed volume feeding into a fuel reservoir. The back-pressure from the restrictor plate results in pressurization of the fuel line from the pump, so that the surging is not telegraphed into the reservoir. The carb can then obtain its demand of fuel from that reservoir, using vacuum alone rather than receiving directly from the fuel pump.

I don't make any judgment or defense of the somewhat outrageous claims that this vendor suggests result from using their product, but the concept of using a flow restrictor to fill a reservoir at a constant rate is perfectly valid, and as above I think at least some of the claims are supported by the evidence.

ps. Mark, please feel free to delete this thread if you think its inappropriate for the board.

PostPosted: Fri Sep 14, 2018 6:12 pm 
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Joined: Sat Jul 15, 2017 5:35 pm
Posts: 2377
Location: Abingdon Oxfordshire
Phew..... I've bitten too many bums and trod on too many toes Iain so I won't be making any further comments. I'll keep all my comments to myself in the future and become what they call a 'silent lurker......' or a taker of info as opposed to a provider of info

PostPosted: Fri Sep 14, 2018 6:22 pm 

Joined: Mon May 30, 2016 1:04 pm
Posts: 575
Location: Norfolks highest point
Anyway :lol:
I’ve got a new old stock filter king boxed I don’t need as my requirements don’t demand that style of performance.
Any offers greatly received.
The salesman within me says they are great :? :D

PostPosted: Fri Sep 14, 2018 6:32 pm 
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Joined: Thu Jun 24, 2010 6:35 pm
Posts: 4800
Location: UK
It's not just performance that it enhances though Jeremy - read the blurb again ;)

Just think of the easier driving in the long daily queue to get out of Great Yarmouth :lol:

PostPosted: Fri Sep 14, 2018 8:29 pm 
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Peter, I don't disagree with anything you've written there about this gadget at all, though I've seen them, I've not tried one, but one aspect of it that it may have that may have been over-looked is the volume of fuel it can hold and that that may act as a 'swirl pot' of sorts. Beyond that, it appears to be just a fancy looking 'bling' filter.

Most of the claims made just read like the usual snake oil non-sense advertising of the day.

Rich, OK mate, so Peter has rattled your cage here mate, though I know he hasn't set out to do this, it's only your chosen interpretation of his words. Peter doesn't say (write) this stuff for the fun of it, he's seen it for what it is and methodically set out what he sees in words that we can all understand. Instead of sprouting off with an insulting flaming post, either i) don't read it or ii) set out what you see. Clearly you feel these do live up to some of the devices claims, OK, so how? Set it out here so we can all get a better understanding, don't just sit back stewing over a bleedin' post on the forum, that was an attack on no one, and then come out calling a fellow and equal member, all sorts.

PostPosted: Fri Sep 14, 2018 8:53 pm 

Joined: Mon May 11, 2015 4:16 pm
Posts: 456
Location: Scotland
Where angels fear to tread?

I could not help picking up on the comparison with the heart and blood circulation analogy. It in fact explains nicely how the Filter King works. In the Filter King there is a diaphragm that acts against a spring. Therefore the chamber volume is variable. Let’s get back to the heart.

When the heart discharges a pulse of blood it over comes the pressure in the aorta, the major artery to the rest of the body, and the heart valve opens. The pressure is now greater in the aorta than previously, but the aorta is elastic so expands, absorbing and attenuating the pressure. It absorbs the energy. As the pressure drops, the heart valve closes while the heart is at rest (between pumping actions) but the elasticity of the aorta continues to pressurise the blood until the next pulse. Thus smoothing the flow. Yes there is still a pulse. In youth the pressures are between 70 and 120 mm of Mercury. As we age and the Aorta becomes more ridged the differential in pressures across the pulse ( systolic and diastolic) increase. This is analogous to having fixed wall piping between the fuel pump and carburettor.

Clearly the Filter King operates in a similar fashion. The elasticity of the diaphragm is able to absorb the peak energy and then, as the pressure drops, releases that energy so maintaining the pressure while the pump is in “rest mode”. Thus it smoothes the flow and reduces the swing in pressure experienced by the float chamber needle valve.

That’s my take on it anyway.


PostPosted: Sat Sep 15, 2018 1:52 am 
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Dearg1275 wrote:
The elasticity of the diaphragm is able to absorb the peak energy and then, as the pressure drops, releases that energy so maintaining the pressure while the pump is in “rest mode”. Thus it smoothes the flow and reduces the swing in pressure experienced by the float chamber needle valve.

That is because that is exactly what it does.
Diaphragm pumps (mechanical or electrical) are fixed displacement and as such deliver a volume to the system being supplied. The downstream system turns this into an imperfect sinusoid of pressure which depends entirely on the restriction (pipe bore, number of bends, valves etc). This imperfect sinusoid has an RMS value of pressure which is the value the manufacturers quote (I think for SU it is 2.5 to 3.5 PSI). However, depending on the system the peaks can be a lot higher than this.

Due to the design and construction of the float chamber and jetting arrangements, horizontal fixed venturi carburetors are much more sensitive to variations in delivery pressure so the fluctuations of pressure provided by fixed displacement pumps causes them issues, particularly at idle, low engine speed and large throttle position changes. They will invariably run weak and then rich with the attendant drivability issues. When the engine starts to consume the full delivery volume, the excursions in pressure smooth out and the pressure at the inlet smoothes out.

The additional diaphragm and spring (pressure regulator) in the system smoothes all the peaks off giving the effective RMS value constantly.

Thinking about it, the only vehicle equipped with Weber or Dellorto carbs that I have ever worked on which did not have a pressure regulator as standard fit from the factory was the 2.5l Land Rover Defender (90/110). Of the others, some had filters some did not.

If I recall correctly, the Facet electric pumps have an internal regulator which bleeds outlet flow back to the 'sump' of fuel that sits around the pumping mechanism, which is why they 'click' all the time they are on.

In my experience, carburetors with small area float chambers (eg. SU H and HS series) are the least affected by cyclic pressure, the wider areas of the HIF series and the Stromberg/Zenith and fixed venture down-draught are a little worse and the wide open chambers of the sidedraught and quad chamber downdraughts are the most sensitive.

I put this down to the relative distance between the point of force on the float and the needle (shut off) valve and the exposed area. Larger areas give larger volumes for a fixed fuel level and as the carburetors are mass flow systems, this significantly changes the effective mass acting on the jet, leading to rich or lean operation in areas of low air consumption or rapidly changing air consumption.

I do not have empirical results to back this, as all the work I did with this stuff was done either on test beds (work) or 'seat of the pants' dyno (own cars).

What I did learn was there are three things that MUST be in place before you do any work on setting up the carburetor in this order:
1: Fuel supply must be clean, stable and big enough to be greater than the engine will need at it's highest consumption.
2: Float chamber vents must be bigger than the minimum size required to vent all the fuel vapour produced when it all gets hot.
3: Float level(s) must be set correctly, the same AND never changed while you are working, otherwise all previous settings are useless.

Point 2 is the one most often missed, as the carburetor gets hot the incoming fuel acts like a coolant to the chamber and the lighter fuel fractions 'boil off'. This is not a real issue as most of the light fractions are there for cold starting and contribute less to the overall performance when driving warmed up. However, if they cannot exit the float chamber then fuel cannot get in and the engine will run lean.

PostPosted: Sat Sep 15, 2018 9:00 am 
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Joined: Thu Jun 24, 2010 6:35 pm
Posts: 4800
Location: UK
So basically it serves two purposes ....

1, to filter the fuel and

2, the most important or relevant part compared to a £6 fuel filter .... it acts as a dampener to the fuel pulsing from the pump to give a steady, regulated flow to the carburettor.

I can see the sense in both of the above.

As for some of the other claims - just sales pitch :roll:

PostPosted: Sat Sep 15, 2018 1:07 pm 
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Joined: Mon Jun 10, 2013 9:57 am
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Location: Australia
Here is a "how does it work" article in this magazine from 1986.

RAC offical certified trial No. 903 on a standard Marina 1.3 with a filter king fitted showed a 10.6% overall mpg improvement ... hp?t=32280

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