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Discussion Starter · #1 ·
Alright, I *know* my mixture is off after driving around last night and pulling into my driveway and my roomate (who was outside riding his bike at the time) asked me what "that smell was." I got out of the car with it just idling, and all you could really smell was a decent but not overly excessive amount of unburned fuel. I pulled each plugwire to make sure that each cyl was firing and burning, and all seems fine.
Now, I know there's a way to adjust the mixture using a wideband exhaust analyser, but I don't have one. Are there any reliable "shadetree mechanic" ways of properly adjusting the mixture?
Thanks in advance.
 

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Re: Adjusting CO without exhaust sniffer? (need_a_VR6)

Yep, but you need a dwell meter ($30-$40, got mine fron sears). There is a Lambda Test port near the cold start valve, it's a female connector with a blue and a brown lead. Hook the dwell meter up to that and it should be bouncin' around 45 degrees, if not paly with your mixture. If that doesn't work, consult your Bentley http://****************.com/smile/emthup.gif
 

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Re: Adjusting CO without exhaust sniffer? (need_a_VR6)

What car / what engine/ what injection system, Dignifant or CIS?
If CIS lambda see vwbyte.
 

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Discussion Starter · #4 ·
Re: Adjusting CO without exhaust sniffer? (gearhead455)

Info: 84 Rabbit GTI, 2.0 ABA/Hydro, CIS-lamda
Is there any way to do the same thing as a dwell meter with a DVM that is able to read duty cycle? And if so, what should it be with the engine warm and at idle?
Thanks guys!
 

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Discussion Starter · #7 ·
Re: Adjusting CO without exhaust sniffer? (need_a_VR6)

Here is the current verdict... Drove home with my borrowed meter, got everything up to temp. Plugged into the plug and read 69Hz, 81.2%duty. Figured this was way rich (valve on 80%, sounds reasonable).
Adjusted the CO to get it down to about 50%, ended up around 48.7-51.2% fluctuating, sounds nice. Now, when I hit the throttle switch, it drops solid to ~39%.
Now I'm confused! If I was running rich before, shouldn't the throttle switch be bringing me to 70% duty or something? Is my throttle switch actually leaning out my mix, or was I waaay lean before?
Anyone have good numbers for the duty cycle both for a hot idle and with the throttle switch?
 

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Re: Adjusting CO without exhaust sniffer? (vwbyte)

What about a car with just CIS injection?
I was told that an O2 sensor with a voltmeter hooked up was a way to check the readings.
Any truth or more ideas on this?
Peace
 

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Discussion Starter · #10 ·
Re: Adjusting CO without exhaust sniffer? (ABA Scirocco)

Well, that site helps, but will the readings on the dwell meter (40, 50, 60, etc) be directly comparable to duty cycle readings? (or is that what dwell is?)
If so, according to that site, both cold idle and full throttle should be richer than 50, more in the 40 or slightly under range. You are suggesting near 60, which is it?
Still confused and thinking of buying a dwell meter before the weekend.
 

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Re: Adjusting CO without exhaust sniffer? (need_a_VR6)

quote:[HR][/HR]Well, that site helps, but will the readings on the dwell meter (40, 50, 60, etc) be directly comparable to duty cycle readings? (or is that what dwell is?)
[HR][/HR]​
the range on a dwell meter is 0 degrees - 90 degrees.
so to convert from dwell reading to duty cycle multiply the reading (in degrees) by 1.111
to convert from duty cycle to dwell angle, multiply the duty cycle reading by .9
either way, if you have a dwell meter, at normal idle, the reading should oscillate around 45 degrees, and the full throttle enrichment should move it up to around 72 degrees.
if you have a duty cycle meter, it should hover around 50% at idle, and 80% at full throttle.
and 80rabbitc, you can read the o2 sensor output, but this inidicates the actual mizture of the engine. no matter how the mixture is adjusted, if the engine is running in closed loop (not warmup, and not full throttle) the fuel injection will adjust until this reads .5 volts (within it's limits, there is a such thing as too far off)
if you measure the duty cycle, this is the correction the computer is making to keep the oxygen sensor at .5 volts. it's important for the duty cycle to hover around 50% so the computer has the range to correct for both rich and lean conditions.
bye
 
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