Club 80-90 Forums

You're messing with my head now, a gauge with no numbers, how can that be so.

No need to defrost the drivers window either

I've never used an A/F gauge, so don't know how they work in practice. I imagine they move around with load quite a bit so will be difficult to compare between vans ?

937carrera wrote:You're messing with my head now, a gauge with no numbers, how can that be so.

No need to defrost the drivers window either

I've never used an A/F gauge, so don't know how they work in practice. I imagine they move around with load quite a bit so will be difficult to compare between vans ?

my closed loop LPG system on the tin top stays pretty much in the middle when cruising,but not stationary always on the move but yes it swings alot when not

Today I investigated a knocking when starting particularly when hot, it happened after the last oil pump change so I assumed it was something I did but apprears not just this pipe hitting this tin, bent it out the way

P1100397 by Paul_Barr, on Flickr

then I noticed a water drip, I have seen it before and it then dawned on me the pipe was split, luckily I had a spare so swapped it over.

P1100400 by Paul_Barr, on Flickr

rocker gasket leaking again so got the sealant out

P1100399 by Paul_Barr, on Flickr

I'll just leave this here...
https://www.customandcommercial.com/vw- ... nes_23906/" onclick="window.open(this.href);return false;

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ajsimmo wrote:I'll just leave this here...
https://www.customandcommercial.com/vw- ... nes_23906/" onclick="window.open(this.href);return false;

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oooooooooohhhhhhhhhhhhhhhhhh

Is that "ooohhh, they're nice" or "oooOOOooohhh" whilst clutching a handbag, R&M style?

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ajsimmo wrote:Is that "ooohhh, they're nice" or "oooOOOooohhh" whilst clutching a handbag, R&M style?

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oooohhhh thats nice

never seen those, going to try some, always get a leak on no3 just above exhaust, same both vans.

Thanks for the link Andrew. Just ordered two.

happy to help

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2.1 DJ Air fuel gauge
I fitted one because I felt like it and because on my DG van with LPG it has helped to tune and diagnose problems.
I have been watching it for a while and I have come to the conclusion that at higher revs it is lean with up to and past half throttle, on lower revs it tends to be jumping back and fourth unless on light throttle when its lean
High revs or low revs foot to floor its mid range to rich.
To those in the know does that sound right?

20180609_192726 by Paul_Barr, on Flickr

Don't know if I'm in the know for a DJ, but this is what I would expect from other cars

Full acceleration - rich
Idle - normal to lean
Overrun - lean
Constant speed cruising - normal to a little lean
Light acceleration, should be a little on the rich side.

It looks as though you need a little more fuel when the engine is at higher revs and under acceleration. Is your DJ open loop lambda or is it a fixed map?

The guy that does my mapping always avoids being lean under acceleration and will sometimes tip some extra fuel in for cooling. Not good for economy, but that's not generally the objective.

Thanks for the info
DJ is fixed map
its quite new to me only had it 18 months so still learning I don't think.its adjustable bit might indicate an air leak or gummed up injectors.

its running 95 on 5 degrees so I might try a tank of 98 on 10 degrees it maybe that thats the cause.

That certainly won't do any harm, but putting a higher octane fuel in won't change the air / fuel ratio, it will however give greater protection against detonation.

On the timing, I'm not sure of the conditions you are talking about and if it's BTDC or ATDC. I'll need to think about how the a/f meter works to decide if timing adjustments will change what you are seeing. Lean mixtures need more advance.

Have you checked your fuel pressure, if that's low then you'll have a lower quantity for a given duty cycle.

How does the DJ detect throttle position, is there a potentiometer in the throttle body ? That could be out of adjustment or giving a wrong reading.

An air leak would generally have a reduced effect at higher engine speed, (small orifice so limited flow) so I doubt that's the issue. Maybe injectors could do with a clean, or at least check their delivery rates at full duty cycle against spec. (whatever that is). I very much doubt that the injectors are at full output on a DJ, but you'll need someone with real DJ experience to advise you there.

Has anyone ever taken one to a rolling road to be remapped ?

But an air fuel guage does not really measure air fuel ratio
it just detects if there is oxygen left in the exhaust by lambda sensor afaik
so a higher octane fuel would use more of the oxygen surely?

Cetirus paribus

I've got two answers, one instinctive, the other more reasoned.

Octane is simply a measure of resistance to knock, it doesn't really affect the burn process provided detonation does not occur. High octane fuel in a car makes no difference at all, unless the timing is changed to take advantage of the ability to take the additional advance without detonation.

If however you are looking at total oxygen availability, then in addition to the o2 in the air there are also oxygenates (hydrocarbons with oxygen molecules) in the fuel, for example ethanol / MTBE. It's these additional sources of oxygen that give a better resistance to knock.

If you are detecting unburnt oxygen with the a/f sensor, then that means there was insufficient carbon / hydrogen molecules to burn with the available oxygen. Providing more oxygen in the form of fuel oxygenates (as opposed to pure hydrocarbons) isn't going to solve this. Either way I think it's pretty marginal.

I've stopped short of the chemical equations, because that would be more revision work, and I already scratched my grey cells on Lucas points for RogerT this weekend so take the above as a view for discussion, rather than absolute science.