Morning all

Another job on the SVA fail list was the emissions being too high. Had a quick look through the Haynes and the only thing it looks like I can adjust is the mixture screw on the side of the 32/36 DGAV weber carb.

It says scew into carb to reduce co2 and out to raise. Is it really as simple as that to reduce the emissions or are there other things to take into account.

So if anyone can provide in basic terms a guide to getting the emissions to 3.5% on a pinto with 32/36 weber bcarb I'd be grateful.

Cheers
Nigel

I take it you mean CO rather than CO2. You need to make the mixture less rich to reduce CO.

Sorry early still, yep the CO emissions need reducing. so if I simply screw the mixture screw in until the engine idle is effected and back out until it goes back to normal that should have a noriceable diffrence on the emissions?

Is there anything else to be aware of apart from that?

why not buy yourself a colour tune plug from Halfords, well worth it and you can see how your changes are affecting the mixture. I've used them for almost 20 years and they are superb and simple to set up emissions, also good at fault finding, lets you see inside the engine when its running and you use the colour of the flame as the guide...sky blue (like below) being spot on, yellow being rich and pale blue being lean, dead easy












[Edited on 23/10/08 by Mr Whippy]

cheers

as to original question is it purely the mixture screw that I can adjust to effect emissions or is there anything else to consider that can also reduce them.

Cheers
Nigel

Sorry to hear your car failed SVA Nigel, seems that it was a good fail though, nice & easy to rectify.

Have you booked your Re-test?

Regards,
Lee.

no not yet Lee I really don't want to have to go more than twice so want to make sure that the 8 things on the list are well and truly done.

That's why i'm trying to sort out what other factors could effect the emissions.

I thought that engine idle speed, timing and mixture would be the contributing factors but wondered if there was anything else.

Float chamber level - too high too rich & vice versa

Suddenly the emissions aint looking so easy. I didn't think that there were more than a coup;le of things that could be altered to effect it.

Don't want to drive back to the retest without knowing it's going to pass the emissions.

You really need to set it up it on an emmissions tester to get is set accurately, can you take it to a local MOT test station to use their machine?

Regards,
Lee.

Im sorry that i cant help you directly but i used this site to help me understand the 38DGAS and set ups before SVA. Have a look in tech section, might be something of interest in there.

http://www.redlineweber.com/

I was lucky in that SVA guy handed me a screwdriver when mine was about to fail emissions. He didnt say a word but i twiddled a screw and as soon as the readings were displayed correctly he hit a button and took screwdriver off me.


I set mine up roughly with colourtune at home then checked on local MOT places tester. Still needed a fiddle at SVA though. I should have concentrated on making the result very low rather than as close to 3.5 as possible. I was just concerned about the drive to test if it was too weak.

Thanks Darren

There was a useful document on setting the idle in relation to the mixture and how to check the jets etc are the correct size.

That gives me something to work to before getting the levels checked at a garage

Assuming every thing else is set (timing, tappets etc) then yes turning the screw in is how you weaken the mixture.

Small amounts can make quite a difference though. You realy need a gas meter (colour tune if not). Back in the day I could get pretty close by ear but I don't get the practice anymore with modern ECU controls.

What were the readings at SVA

adr

4.6 and should be 3.5

idle was 1200 which is a bit high but mixture screw looks well out so I assume lower idle and lower mixture should sort it then test with a meter.

Roughly how much % difference can I get using the mixture screw?

Any thing from so weak it wont idle to too rich to idle.

Turn it clockwise a turn and see how it sounds. It'll increase revs as you do, so keep correcting that as you go. Go too far and the revs will fall. If you blip the throttle and as it comes back to idle revs falter (drop too far) and then recover its too weak.

Needs a meter really.

adrian

As others have said get it on a gas analyser . Turning the mixture screw in will reduce the C.O. and should drop the hydrocarbons . Tight valve clearances will cause high hydrocarbons as will misfire and incorrect timing If you have a vacuum gauge and a connection on the manifold not vacuum advance take off you can use it to adjust mixture . You want the highest steady vacuum you can get. A very underrated tool.