mixture setting tips!!

''Perhaps this is some magical trait of the Golf that just so happens to perfectly set up a safe AFR throughout the entire rev range ''


PLEASE read paulc's afr thread.

the idle mix screw gives the afr a value which is maintained throughtout the revrange due to the mechanical nature of the kjet system.

it actually HAS to set up a safe afr.

i am talkin about a standard dx, as thats whats mostly on here! tho the principle will apply to a modified car runnin kjet ie NOT ecu controlled.

Have you got a link to this thread?

"it actually HAS to set up a safe afr"
How? I'm new to Golfs so would like to know how AFRs are set up/corrected

because all your doing when u adjust the mixture screw is changing the position of the airplate in relation to the fuel feed. the leaning out at higher revs, which is right,  is controlled by the cone the airplate moves through.
the 'idle' mixture screw is the base value the afr is set to.
the fuel flows, not because of any  other controls than the air plate and wur.
fuel pressure could have an effect but only if it was seriously low. that would then be indicated by a lack of power when you put your foot down, it would probably idle and run ok tho.

there is no other fuel management system on these cars than the idle screw…….

pauls thread:
The Mk1 Golf Owners Club

JSeaman said

Have you got a link to this thread?

"it actually HAS to set up a safe afr"
How? I'm new to Golfs so would like to know how AFRs are set up/corrected

Its set by reading the CO level at idle. This is typically done using a gas analyser, the cheapest which is around ?75 these days, I think. For those who don't have one and can't justify buying one, there are 2 options:

1. Take it to a garage (who do have one)
2. cabriaulait's method above

Do you know how CO varies with AFR?
Do you know the relationship between AFR and cylinder temperature?
Do you know where the lean misfire limit is?
Do you know how AFR varies with rpm, on a Golf GTI?

Unless you knew this, you wouldn't know when your engine was about to enter an unsafe running zone.

Suffice to say, VW's recommended method (and pretty much every other manufacturer's, at the time - no cat to damage) is safe enough.

I'll have a read of that thread later and get back to you

Before I do please clarify that your stamp on the brake pedal method isn't recommended by VW?

OK I've had a look at the thread and have no reason to think the brake pedal method is in any way safe/advised. Once again, is this VWs proposed method or something thought up by someone here?

Your questions about CO, AFR, cylinder temps etc just go to back up my point about guessing the tune.

"Unless you knew this, you wouldn't know when your engine was about to enter an unsafe running zone. "
You would with an EGT sensor and wideband electronics. You don't by pressing the pedal

"VW's recommended method … is safe enough"
But is this their recommended method?

You cannot prove it except to say that empirically, it does - cabriaulait had his car later checked using the proper measuring devices and it was only 1/8 turn out.

But how much is 1/8 of a turn  :wink:   
Bert
Thank god i have a diesel  8)

Well, by the looks of things you have the kit to show what's going on - any chance you can hook your wideband up and do some tests on what thafr/co levels are doing when you stomp the pedal?

Bert said

But how much is 1/8 of a turn  :wink:   
Bert
Thank god i have a diesel  8)

Do you mean how much the AFR varies, if you turn the metering head screw 1/8 turn? Or how much the CO varies?

hmm love these threads i always arrive just as a tangent is about to start

i dont have the afr problem i use a lc-1 and to be honest you could run very lean with a k-jet lump without any engine problems ie melting pistons ect

''Well, by the looks of things you have the kit to show what's going on - any chance you can hook your wideband up and do some tests on what thafr/co levels are doing when you stomp the pedal?''

itll show no difference if already correct tho :wink: thats the idea.

You can see in real time this alteration to the mixture by pressing the brake pedal though - would be interesting so see how valid the comment is

Due to the way I've clamped the lambda probe at the end of the exhaust, I can't accurately measure AFR at idle. I'd have to make another exhaust probe…

That's a shame, if you ever remove it or get a spare would be very interested to see if the figures back up the theory.

God i wish i knew what your all goin on about. I got lost at idle!! :?

I'm not taking sides but I'm going to give cabs method a go. I've been messing about with that 3mm allen key and the timing for the past 10 years and I havn't done any damage at all to the engine as yet. I don't have all the scientific tools and I'm not willing to pay silly garage prices to get a so called bodge up tune job. So one more adjustment using cabs method won't do my engine any harm. I'll let you know if it works for me  :wink:

if anyone in the notts area wants to have a play on a C02 machine let em know.

M7R said

if anyone in the notts area wants to have a play on a C02 machine let em know.

CO

Sorry my bad, not been 100% with it lately…. ops: