Co Adjustment Failure

[RINRIN 1]

Hi,

 

I go for a co setup I was going setup co to 1% ad idle and 0.5% at 3000 rpm. and I set my pugs co to 1.7% because only at that value I get 0,5% at 3000rpm. Then I tried to adjust my friends pug, but when we try to get 0.5% co at 3000 rpm the co at idle was 3%.

I dont understand why is that difference. What is the poblem on my frineds pug?

Any ideas

[RossD 44]

The screw on the AFM will only set the CO % at idle - I don't think it should have any effect higher up in the rev range. THis is controlled by the AFM and the ECU.

[Saveit 0]

The screw on the AFM will only set the CO % at idle - I don't think it should have any effect higher up in the rev range. THis is controlled by the AFM and the ECU.

 

As far as i know thats not right. The screw will adjust the CO% through the whole rev range, but the AFM can be a pain in the a** to mess with by my experience.

[RossD 44]

Ok, there ya go, I'll stand corrected!

[RINRIN 1]

All the resistance checks are done on the AFM and is OK.

Can it be the fuel pump failing to send enoung pressure?

[Tom Fenton 1,542]

As far as i know thats not right. The screw will adjust the CO% through the whole rev range, but the AFM can be a pain in the a** to mess with by my experience.

 

Ross is correct. The screw only alters the idle mixture. Through the rest of the rev range is controlled by the resistance of the springs in the AFM.

[RINRIN 1]

So the spring in the afm gets old and does not osciliate in order?

[Alteran 1]

So the spring in the afm gets old and does not osciliate in order?

 

Maybe your friends AFM has been fiddled with in the past. Weakening the AFM spring with cause the door of the AFM to open easier when air shoots into the engine. Thus causing a rich mixture at revs.

[RINRIN 1]

I am sure that his AFM did not fiddled before.

[Saveit 0]

Ross is correct. The screw only alters the idle mixture. Through the rest of the rev range is controlled by the resistance of the springs in the AFM.

 

Okay ill stand corrected then But isnt the screw on the AFM to adjust the hard/softness of the spring? I had my car on rolling road, and the guy said it was much to lean. He adjusted the screw on the AFM and it resulted in more gasoline through the whole rev range?

[welshpug 1,657]

no, all the screw does is open or close a bypass channel in the AFM, this basically alters how much the flap moves when it has low vacuum pressure working against it.

 

Larger throttle openings are not affected by the bypass screw as the flap is opened further.

[Saveit 0]

Ahh okay. So if you are to adjust the the whole rev range then you have to move the little plastic gear/sprocket indside the AFM either clockwise or anticlockwise - right?

[welshpug 1,657]

I don't think you should move that at all, if its working correctly, if it isn't, it needs remanufacturing IMO as there are no specifications available for the spring tension required.

Edited June 2, 2009 by welshpug

[RINRIN 1]

When I set my co at idle to 1.0% then at 3000 rpm the co is 0.25%

When I set my co at idle to 1.6% then at 3000 rpm the co is 0.5% which is the value that we want to have. So the screw looks like effecting some how, please try if you have a change.

Also if Whelspug says than I can go after that. So my friend AFM is working but just old

[Shepp354 0]

My understanding is that the screw is a taper to control idle mixture by allowing air to flow into the engine bypassing the AFM flap and the injection system's control. So screwing it out allows more unmetered air in and makes for a leaner mixture.

 

Were your results acheived by reving from idle or under load? If from idle (low load) then I think that you will be on very part throttle and the flap will only be open a touch and the amount of air being taken in through the bypass screw will have an effect on what's being taken through the AFM as a whole.

 

When the engine is under a decent load (a more open throttle) the flap will be further open and the amount of air passing the flap in the AFM will be much greater than than the air through the bypass so the screw won't effect the mixture so much. So for most driving conditions the idle mixture screw has no effect and the amount the flap can open against its spring tension is how mixture is controlled.

 

So the screw changes very low load and idle mixture and the spring changes mixture the rest of the time. I'd not play with the spring tension without a rolling road to prove the changes are for the better.

 

It could be your results are what what you might expect!

 

Hope that makes sense

 

 

When I set my co at idle to 1.0% then at 3000 rpm the co is 0.25%

When I set my co at idle to 1.6% then at 3000 rpm the co is 0.5% which is the value that we want to have. So the screw looks like effecting some how, please try if you have a change.

Also if Whelspug says than I can go after that. So my friend AFM is working but just old

[RINRIN 1]

Thanks very much.

 

but all above that an AFR is the solution to these problems. The first thing that I will do is to buy an AEM AFR