Reducer maintaining pressure? - KME Silver

[mattstead]

Hi, I'm struggling to get my AFC KME Diego system perfectly tuned on my Suzuki vitara 1.6. It's a system I sucessfully fitted to my wifes car almost 4 years ago, but removed it after a year when she sold the car. It's just been sat in the garage ever since. I've fitted it fine, but found that it wont maintain a state of tune from one drive to another.

I noticed that it drove much better whenever I filled the 100 Litre tank, but only for a while, so thought there might be a pressure issue.

With the software on I noticed that there was a setting for setting the "working pressure", but is this the cars normal, petrol, working pressure or setting a gas working pressure?

When I had the software running I saw that the pressure was dropping to a lowly 0.45 Bar, and it was switching back to petrol...I tried cranking up the pressure on the KME Silver reducer and the car ran much better, but even though I'd upped the pressure to 1.5 bar, the next time I looked it was set at over 2 Bar. I always believed that I'd set a pressure and that the vaccuum acting against the vapouriser would maintain the pressure, but it still varies dramatically betwen 0.7 bar and now over 2 bar depending upon acceleration.

Can anyone explain if the vapouriser is supposed to maintain a pressure? I've heard that some KME Silvers have history for nor maintaining pressure.

Thanks.

[rossko]

Only take note of gas pressure when running LPG, you can get misleading readings when gas is shut off. In the perfect world, gas pressure would be constant. In reality you get ov over/undershoot off na don-load, your sis very excessive.

Be sure your MAP sensor and reducer vacuum pipes are seeing the same vacuum and in good order; be sure that vacuum is actual MAP and not the wrong side of a check valve or other complication if tee'd into existing vacuum line.

Be sure your pressure sensor and pipework are good. A confidence check would be to pull off both vacuum and pressure pipes and see that your laptop reports zero differential pressure.

Be sure you haven't squashed or kinked the supply pipe from tank to front.

After all that, the symptoms are like a clagged filter. Or a gummy reducer - sitting around could do that.

[beamerguy]

On my BMW the idle gas pressure is set at about 1.1bar when I put my foot down it goes upto about 1.6-1.7bar, the only time I see 2bar is when I switch the car over to petrol. I took my kme vapourizer apart and cleaned before fitting has it was 2nd hand and was full of wax, so yours might be clogged up with wax also.

Mark.

[mattstead]

Thanks for the info. The pressure on mine drops under acceleration, not increases. I will strip down the vaporiser and replace the filter to see what I can find.

Thanks again.

[beamerguy]

Thats bad, it means that the vapourizer wont supply enough fuel in that situation, it might be that u have connected the vaccum line to an incorrect place on the manifold, it sounds to me that the vapourizer is not subjected to vaccum at idle and somehow is subjected to vaccum when u accelerate but I cant see how that can happen. I thought it might be possible that u had connected the vaccum connection on the vapourizer to the gas pressure side of things but that would in theory increase pressure so it cant be that, it's got to be something to do with where the vapourizer is getting its vaccum from. The adjustment screw sets the static pressure, in other words it sets the max pressure when there is no vaccum or pressure, however when subjected to vaccum the pressure will drop and when subjected to atomspheric pressure reach the static setting and then go beyond if subjected to boost on a turbo or supercharged car.

Mark.

[andy evans autogas]

I've seen one before do something similar when the reg was off the car for some time and then refitted to another car and not run on gas whilst the conversion was competed. Take the regulator apart and undo the big nut 27mm???? And clean the valve and seat .. That worked a treat on the only one I've seen this happen on. Hope this helps.

[mattstead]

Well I've changed the KME silver vaporiser for a nice new one, and I'm pleased to say that it now maintains a contstant pressure (currently 0.87 bar). It's not yet running perfectly, I've got the injectors pulsing at the same duration as petrol, and mapped it so that the petrol and gas maps seem to sit on top on top of each other, unfortunately under high vacuum loads it tries to kangaroo up the road - I've noticed that under these conditions the vacuum reading reaches its maximum of 0.99 Bar.....could it be that I almost have too much vacuum?

I also can't get it running under any sort of load such as fan, or lights, (in fact it switches to petrol when the brake lights come on and you come to a stop, as its not set up to idle under load).

[rossko]

now maintains a contstant pressure (currently 0.87 bar).

That seems a bit pansy, you'd usually run more like 1 -1 .5 bar

I've got the injectors pulsing at the same duration as petrol

Do you really mean that? It's not usual or particularly desireable.

I've noticed that under these conditions the vacuum reading reaches its maximum of 0.99
Bar.....could it be that I almost have too much vacuum?

That's what's supposed to happen. As the throttle opens, the manifold pressure rises (less vacuum); at full throttle you'd expect close to atmospheric (1.0)

[mattstead]

I've got the injectors pulsing at the same duration as petrol

Do you really mean that? It's not usual or particularly desireable.

Really? Everything else I've read says to get the injectors matching the millisecond duration and percentage use of the petrol ones. That could be the answer if this isn't the case.

[rossko]

The devil's in the detail.
You're delivering a different fuel through different injector system at a different pressure and temperature, there's not much hope of perfect match under all conditions.

The "matching" involved is to get the same effective amount of fuel injected - that will probably involve a different injection period on petrol and gas. Not least because gas injectors are physically bigger clonkier thangs than petrol injectors and act more slowly.

The method is to take advantage of the gas being slaved to the petrol, and the petrol being closed-loop i.e. adjusting itself.
The gas inj period is derived from, but not the same as, the petrol period - it has fiddle factors applied because it's all different fuel, mechanisms, etc.
You'll understand that when, under the same conditions, the petrol system shows the same inj period, that's a good match. Under those conditions, the gas time could be anything. It's usually a bit bigger than petrol (those slower clonky mechanisms).

So if you idle on petrol and see 3.0mS times ... you would expect to idle on gas and see petrol times of 3.0mS too .. but the gas might typically be 3.5mS. Be clear about what you're comparing.

It's important to get it right in the closed-loop working area of the petrol system, because you don't have the use of the self-adjusting mechanism as a tool under all conditions e.g. full throttle. Getting that area right has to be extrapolated from the closed-loop area, which is what the autocal tries to do for you.