Idle mixture tuning

[Phizinza]

How do I get it right? How do I know if it is right?

If I screw it in and screw in the idle up as well it idles good while warm. If I screw it out and unscrew the idle up it idles good while warm. I can't get it to idle good while cold though. And I'm having thermostat problems right now so it ain't getting warm.

[Durania]

This a weber or a hitachi?

[Phizinza]

Hitachi(s)

[Quidam]

Hi,

 

"And I'm having thermostat problems right now so it ain't getting warm."

 

Well, I'd fix this first, then go from there.

 

hth

 

Doug

[Loyale 2.7 Turbo]

Yes, I Agree that First should be Fixed the Thermostat, but This is Your Twin Carb Subie? ... if so, Why don`t you use a Pair of Webers 32/36 it will be Amazing! ... instead of those Craptachis...

My 1985 EA82 Never got the idle mixture Screw to do a Good Adjustment while it had the Craptachi carb, but Since it has the 32/36 Weber Setup, to Adjust the Idle Mixture Screw Became so Easy, (Now it gives the Same Response as my `69 Mercury with in line 6 engine while Adjustment) Just if it is Too Open or Too Close, the Engine Shakes... but Movin` the Mixture Screw between that two Points, makes the Engine Runs Soo Smooth...

Kind Regards!

[Skip]

Phiz

As I'm sure you know

the first part is balancing the carbies

(I used to work on Triumphs, AHs and Jags

all with multiple air/fuel mixers.)

 

Use a "unisyn" or a hose to your ear

they must match air flow first.

Raise the throttle a bit, they must "take off" the same amount.

 

Then set them both at about 1.5 turns out

working one - turn out till it stubles, turn in till it stumbles

set half way inbetween.

 

Do the other the same way.

 

Recheck balance

strart over if it changed.

 

They can be buggers, but with time and patience you will

perservere.

[Phizinza]

^ Skip, so your saying use a tube to get a ventury effect on top of the carb and listen? Then set both to sound the same? I guess use two pipes, one on each ear?

 

I could go 32/36 Weber's, but I think that will be too much air, plus I don't have any money to spend on Weber's and my dual carbs have givin me good economy and brilliant power. The std carbs are sometihng like 20/27's? And there is quite a large range at the bottom of the pedal that does nothing, so I believe they are oversized for the type of driving I do (under 5000rpm).

[Skip]

"so your saying use a tube to get a ventury effect on top of the carb and listen? Then set both to sound the same? I guess use two pipes, one on each ear?"

 

Precisely, I only use one tube or a Unisync (air flow measuring device)

 

Just listen to one and compare it to the other.

 

Loosen the linkage that connects the carbies before doing this

balance job - but you knew that.

[Phizinza]

This is why I like talking to you old school guys. No offence intended. You don't just say "you'll need to get them balenced by a shop". OR you need to buy a kit to do that.

Cheers mate, I'll give it a go.

[backinbrat]

so u were sayin they wernt balanced before? hmmm lol

 

i had idle problems with my hitachi, it wouldnt idle from cold, and i set that up to run 3.1% it must be somin 2 do with the hitachis. and that was to get the best out of it as poss, if you can, do the same, as said, balance first, and then if you can get hold of an emissions tester, and set it up to run at bout 3.1% as far as i know, thats the optimum for power, which is the only thing im worried bout haha! MPG is bout last on my list! otherwise you can run alot lower than that, and get back your MPG, but sacrifce a bit of power

Edited January 4, 2009 by backinbrat

[Phizinza]

I balanced them, pretty easy.

But still getting problems with exhaust noise, sounds like fuel is burning in the exhaust maybe. So I think there is something screwed with my carbs. I think L2.7 might be right in saying weber it!

But what size webers.... hrmmm.

 

Other option is convert to LPG and put a turbo on while I'm at it.. I have a manifold with a TB mod'ed to it already (was my megasquirt spfi project). Just would need to get an LPG installer to install gas to it and for me to build turbo headers with up and down pipes. Then add 6-8psi and I'd be cruising. Of cause I'd loose about 10% power with the LPG, but the turbo would make up for it. And LPG being half the price of petrol here, might be a good idea.

 

Still not sure what I'm going to do. Its just

is really pissin me off and I have no idea what it is or how to get rid of it.

[Skip]

Mr. Fizz-in-za Sir,

I agree it sounds like excess fuel is burning

and or at times exploding in the exhaust system.

 

We both know for this rapid oxidation to occur three main

elements are needed.... fuel and 02 with ignition.

 

You do not mention any camshaft changes but a man of your

potential and resources, well I have to ask?

 

If there is sufficient overlap in the cam profile it can lead to the

sound we have hear.

 

Next the ignition timing comes into play as the over lap and the

timing of the spark will allow ignition to progress through the

cylinder and into the exhaust.

Retard the spark (pull back the timing some blokes call it)

and see it it changes the situation.

 

Did you by chance check the balance of the air flow

at any points above idle?

 

The point I am looking for is why is there extra fuel

that remains unburned and finds it's way down stream.

Could the carbs be jetted to rich (like maybe they are both

set up to run by them self on a mono carb manifold)?

 

We both know a rich mixture results in exhaust backfiring,

where as a lean mixture will cause backfiring through the carbie.

 

Hope some of this helps.

 

 

 

 

Way of the wall: are not pits great, I put one in my shop

when I built it, sure makes life easier sometimes.

Don't see them around much anymore as ins.

regulation are tight. Lifts seem to rule these days.

Nice job on the sound video!!

[Phizinza]

Skip,

Cam shaft is standard dual carb EA81 jap spec. Hasn't changed since it was in the Brumby.

I've got the timing set to 11degrees BTDC. I had it set to 8 BTDC when I got the brumby the engine came in and I set it to 14 BTDC. Never made that noise.

The only things that have changed since the engine was in the Brumby not making this noise have been:

Stripped down the carbies, cleaned them, put them back together with new gaskets. And also cleaned up the vacuum piping, replaced some pipes with new shorter ones etc.

Removed a piece of pipe just after the y-pipes that had all sorts of "adapters" in the middle of it ending up in the 2" pipe being less then 1.5" restricted.

Put a 2.5" exhaust (I know, over sized and unnecessary but I had the pipe and the bends sitting there) after the y-pipes.

 

I was thinking maybe it was removing that 1.5" restriction, but I've got a video of it with the old exhaust cut off after the cat (which is just a hollow box on the old setup) and it made the noise, not as bad maybe, but it made it.

The carbs haven't been change/rejetted etc. But maybe when I stripped them down something went wrong..? Dunno what could of. I didn't miss any parts putting them back together.

 

It did also backfire the other day out of the carbs? Just after coming off throttle at around 2000rpm then coming onto the throttle from idle it backfired, and sounded like it was the carbs not the exhaust.

 

I will have a listen to the balence at different rpm's today