LPG tickover adjustment - works fine but what is it doing ??

Post by **ghost123uk** » 05 Jul 2006, 11:42

I am one of those who have to know how things work !!

I recently adjusted the brass screw with the spring under it on "the big black thing" in the engine bay of my T25 Gasure conversion.

The tickover duly rose to the speed I wanted

But I need to know what I have adjusted !!

I mean, on a carb, assuming the mixture is correct, one adjusts the throttle butterfly "stop" adjuster, easy to understand.

But why doesn't that same process apply to our wonderful Gasure gas conversions ?

What does that brass screw actually do ( and does it affect the mixture above tickover ? )

Post by **speleobod** » 06 Jul 2006, 20:33

If you read the instructions that Steve gives with the conversion you will see a sectiuon listed on how to set idle speed after refit etc. The carbs do very little with LPG and this screw basically sets the idle speed. Geting the balance between the idle and the brass mixture nut is a bit of an art and I think I am going to need to see Steve and his meter as I may have played too much with my brass nuts!!!!

So beware. If it aint broke etc etc

Post by **TYG** » 06 Jul 2006, 21:28

here's a tip
if you are going to fiddle/play with your screw/s mark them up (tipex is good) then if it all goes titties up you can turn them back to where they started from

Post by **ghost123uk** » 07 Jul 2006, 10:00

@ speleobod - Aye I read that, the slight adjustment I made brought my tickover to where I like it - so thats OK - I wasn't fiddlin for fiddlin sake.

Sorry you are having problems with you knuts

@ TheTick - Yeh good tip that - I used to do that on "trim pots" inside radio gear.

My post was more to learn about what goes on - My system is working great, I just like to understand things fully, and I don't know just what that brass screw is actually adjusting. I assume it is the amount of gas at tickover only ?

Post by **alden1957** » 07 Jul 2006, 16:09

I believe its a valve that allows a small amount of gas through into your venturis to enable the engine to tick over when minimal suction is present.i.e. when throttle butterfly is only slightly open, similar to petrol idle screw on a carb. I'm sure someone will correct me if I'm wrong but seems logical to me...
Al

Post by **ghost123uk** » 10 Jul 2006, 09:56

Cheers Al, that sounds quite possible.

BUT

What if the engine stalls and is then left with the ign on but not running, does that valve allow a little bit of gas to be constantly emitted ?

I doubt it, but I will just have to go and find the manufacturers site or summat, for a full explanation of how the system functions.

We all know that running it too weak will reduce power, but is it bad for the engine as well. like running a weak petrol mix causes overheating of piston crowns and exhaust valves, is it the same with gas ?

( I mean, if I wanted to drive to the south of France and back, I might decide to weaken the mixture for the long M/Way bits to save money !! - but, even at my cruising speed of 65 / 70, would this be OK ? )

so much to learn, so little time ( who said that !! )

Post by **alden1957** » 10 Jul 2006, 16:38

Your question..What if the engine stalls and is then left with the ign on but not running, does that valve allow a little bit of gas to be constantly emitted ? No...With ignition only on gas doesnt pass through..there is a wire to your main gas switch that is connected to the coil to tell the system that engine has ignition on and is turning over or running.. i.e. coil negative
Regarding weak or rich mixture..I would treat it like petrol..dont letv the engine struggle..let it run nice and smooth..and set it so it does..
I thgink Steve is on hols but try and find out more info from Pete Headley...I'm sure he'll know..
Al

Post by **steve8090** » 10 Jul 2006, 17:25

If any of you are unsure of how to treat the system and how it works you are more thna welcome to come over to the garage anytime and I'll explain it to you, I will not put it on a public forum and give away some of my hard earned knowledge.

You do ask some daft questions

Post by **ghost123uk** » 11 Jul 2006, 08:22

@ Al - well that confirms what I thought.
I do run it at a mixture that feels just right, these questions arn't because I have any problem, I just like to understand things fully !

@ Steve

You do ask some daft questions

I know, I know, Some of my Q's are more looking for affirmation than outright questions. It's how I learn stuff.

Cheers guys