Funny afr's

[R5gttDJ]

Right got my afr gauge wired up

On tick over it sits fine 13-14
However on normal driving it sits at flat 10's all the way
Flooring it in 2nd it stays at around 12.2-12.8 then when I hit 3rd it falls to 13 unless I lift the throttle for a second then it goes back down to 12.2 and stays here through to 4th and 5th right through a long pull!
So why have I got this flat spot and rich normal driving?
It's only 3rd gear that has the problem??
Do you's think I have one if them 'group a' rubbish in my car?
this is at 14 psi and I want to have 18 psi hopefully after tweaking
Anybody help here?


Cheers

[casper]

Your best off checking afrs @ wot in 4th gear so thats foot flat to the floor.Saying that the first thing you want to do is stop flogging your car and strip the carb to measure what jets etc you have in there.:agree:

[TNT ANDY]

Right got my afr gauge wired up

On tick over it sits fine 13-14
However on normal driving it sits at flat 10's all the way
Flooring it in 2nd it stays at around 12.2-12.8 then when I hit 3rd it falls to 13 unless I lift the throttle for a second then it goes back down to 12.2 and stays here through to 4th and 5th right through a long pull!
So why have I got this flat spot and rich normal driving?
It's only 3rd gear that has the problem??
Do you's think I have one if them 'group a' rubbish in my car?
this is at 14 psi and I want to have 18 psi hopefully after tweaking
Anybody help here?


Cheers

1st stage may be too large.

What turbo have you got?
How much pressure are you running?
Cams?
What size main, 1st, 2nd and A/C have you got?

[R5gttDJ]

T2/25 turbo technics
14psi
All standard apart from 1.00 ac
270 cam

[R5gttDJ]

I put the 1.00 ac in but tbh I don't know the other jets could have been tampered with before me, how do I measure the Venturi size to see if its a group a?

[TNT ANDY]

measure everything bud, all jets etc. because that looks wrong. Measuring the ventur, easy - wip the carb off and get a set of verniers up there. You're going to be stripping it anyway. BTW, there may also be a tare in the gasket which does it's job on the enrichment circuits.


Strip down - re-built and check all sizes of jets / venturi. With the setup you have got, I would expect to see pretty normal, stable fueling with the standard carb with the A/c and stage (1 or 2 can't remember which it is now) swap over.

[R5gttDJ]

Thanks mate I'm going to whip it off at the weekend and have a look

[Alex]

As above really; strip it all down, measure and clean everything. I'd stick a standard A/C in aswell and go from there. :)

[R5gttDJ]

I'm thinking maybe acc pump will cause the richness at part throttle?

[R5gttDJ]

All jets standard apart from ac jet had the carb off last night?

[Alex]

As above really; strip it all down, measure and clean everything. I'd stick a standard A/C in aswell and go from there. :) ;)

[R5gttDJ]

So do you think the ac jet cud be the problem should I make it larger?


Cheers

[casper]

It could be a number of things.Start by checking your main jet and a/c jet.Put these back t:agree:o standard.

[R5gttDJ]

It's got a standard main so I think I will increase the ac jet




Thanks

[casper]

Make sure you check your jets with a micro drill bit.They may have been :agree:drilled.

[Woznaldo]

R5gttDJ, it sounds like you are suffering the same symptoms that I last had with my Carb. Unfortunately I never found out what the problem was. My car has been of the road for over a year now and I have rebuilt my Carb in an attempt to fix the issue once and for all, but the car has run on the road yet so I can't confirm if the rebuild has worked?

What I will say is, I took to all mating surfaces of the Carb and enrichment device with 1500 grit wet and dry (on a flat surface) just to make sure that wasn't the issue either?

I'll let you know how it turns out by the months end.... ....hopefully. :sad2: