Thoughts Appreciated: Air Flow + Mixture

[Diff]

You should re do the 'open loop' adjustment of the vapouriser after refitting the pistons.

Good luck,

Regards, Diff

[hangover]

Fisha, did you end up getting htis sorted ? What is the system you are using for the closed loop control ?

Thanks,

Nick.

[fisha]

Fisha, did you end up getting htis sorted ? What is the system you are using for the closed loop control ?

Thanks,

Nick.

ECU is an OMVL Millenium.

OK - bit of a follow up - but overall, its running super smooth with the filters bolted straight onto the carbs as shown in the first picture ( it aint that clean anymore though! )

A number of issues that I have found and resolved since this post originated:

a) the closed loop system didn't seem to be working properly - i dont know why but I was finding that the stepper motor was clamping down on the gas supply at idle and this was causing the engine to falter.

Cure: I have removed the stepper motor from the gas supply pipe to the carbs. all other parts are still in place ( ECU etc ) but just that it now effectively runs in an open loop mode.

B) One of my spark plugs was duff. This was causing #4 cylinder to sometime fire properly and sometimes not. This I think was the principle cause of my stuttering on low throttle when cruising. This also meant my fuel mix was unreasonably rich at times, causing me to have to tune down the LPG to get a good reading. Overall result though was the other cylinders were running lean - leading more rough running.

Cure: New plugs and gaps set properly - then re-tuned

c) The vapouriser needed a general servicing. I found a couple of issues with the vapouriser. The first was that it just needed a good clean. The solenoid was gunged up causing the LPG liquid supply to run down and cut out.

Cure: New diaphram kit and a thorough clean of the insides to get rid of the heavies. Paying close attention to all the small holes around the solenoid.

d) The tension adjuster in the vapouriser had lost its springiness. The diaphram that controls the main feed of gas works against a spring. The more preload and pressure you put on the spring, the harder the diaphran has to work against it. However, my spring had no real action to it. It either let the diaphram run slack, or would make it very hard to move. There was nothing really in between.

Cure: I took the spring and stretched it to expand out the coils. This meant that the spring engaged against the diaphram sooner with little force, and then gradually increased its force in a much more linear manner. This allowed for a much better range of tension adjustment. This action has posed some questions in my mind as the to real detailed effect it'll have on the fuel mix, but i haven't fully investigated those yet.

Overall result is my engine runs really really well. Considerably better than I ever thought it would. It idles at about 800rpm, but it'll happily drop to 400rpm when in gear and still pull away smoothly. Its really quite difficult to stall.

Although I'm running in an open loop mode, my emissions returned a decent enough pass ( compared to before ) and my ecomony is returning an average ot 14.5 to 15mpg. I recently did a motorway run upto Aberdeen and it returned just over 17mpg. Thats not bad considering I have a set of wide mud tyres on, the car was fully loaded and I had a bike rack on the back. Average speed was about 55 to 60 which is a nice easy going pace for me in that car.

[hangover]

Good to hear, so the carbs are still less the pistons? do you think that either the stepper or the ecu or even the ego sensor were possibly faulty ? I am looking at the pro's and cons and so far your's is the only carby rangie i have seen with a cl system fitted. I had basically the setup with the twin strommies etc but i was having problems getting it to run right ( similar probs to what you were having) so i pulled it off and fitted a holley carb and a simpler impco system just so i could use it.

[fisha]

I'm not sure what the problem is with the stepper motor. i can hear it whirr and click, but i've not closely looked at it as i was in a rush to get the car running and througth the MOT.

Since doing that, i've found the car to be perfectly driveable, ecomonic enough and thus the need hasn't been there to improve the setup.

I still have the pistons removed, but will probably re-fit them further down the line.

Other items i found helped in the long road to good running has been to replace the 2 diaphrams in the carbs, and also the gaskets where the carbs join the inlet manifold.

Out of all of the fixes, the new spark plugs made the biggest and most notable difference.