?fit balance line impco freshie for stoic??

Propane, Butane, LPG, GPL, C3H8, C4H10
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jono
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?fit balance line impco freshie for stoic??

Post by jono »

I am attempting to straighten up an old CA125 fresh air mixer to get better values and hopefully better mileage. Exact same set up CA125 and Cobra give better from another car same weight, same engine , just 475,000 fewer kilometres :)
Running a tail pipe analyser on it only just get 14.9, maybe 15.0 and 15.1 while cruising. It was about 14.4 earlier this evening and then I fitted a leaning ring - just one and got idle up from heavy 13.2 up to 15.3 , also got the improvement on cruise.
The mixer is very old (was old 10 years ago :) ) but with a newer silicone diaphragm less than 5000km on it.

Am I likely to get an improved AF ratio by installing a balance tube between the Cobra and the CA125 (or just after it )

Then question may be where. I think the mixer has a 1/8th or so plug in its side and also has a brass outlet currently blanked off - it is for dual fuel apps I believe.
Unsure if 1/8 style plug is in correct place - the pick up needs to be close to the exit of the mixer ??

The Cobra has a brass breather plate in the cover so that should be fine so long as we have threaded hole.


Am running a balance line in my turbo IMpCO 200 and L combo so understand a few things about balance lines just need some finer tips for this one, and am I going to achieve an improved, closer to stoich reading ??

Oh, spring colour under the lid of the mixer was green - what changes can I get from changing to a different grade/colour spring ?

thanks

jono
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Re: ?fit balance line impco freshie for stoic??

Post by jono »

Update.
I have found the Cobra has a 1/8 NPT thread in the cover under the brass gauze cap.

There does not appear to be anywhere to hook up a balance line to the 125 mixer, although I cannot see around the entire unit now I have reinstalled it.

It has the brass dual fuel vacuum lift connection and oddly a plug on the side of the vapour inlet.
Someone correct me if I am wrong, I think I can simply tap into just after the mixer prior to the throttle body ? to get same pick up as a bal port on the bigger 200 and 225 mixers.....

Steptoe
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Re: ?fit balance line impco freshie for stoic??

Post by Steptoe »

Running a tail pipe analyser on it only just get 14.9, maybe 15.0 and 15.1 while cruising.
Just because u have leaned the mixture out, doesnt mean that it will get better milage, If the timing was diaqled in correctly before hand the chances are leaning out u will hurt your milage badly.

Sound strange?
OK... there is a piont between 12 and 18 degres ATDC That the max explosion (max compression must occur for max effiency...) this piont withing the 12 to 18 degs is a narrow +/- 2 degs tops... When one changes compression , fuel, mixture and lots of other parameters, this also changes the speed of the flash across the chamber to max explosion... change that speed and u change the piont ATDC that this explosion takes place.
So assuming that the engine timing was dialed in correctly orginally, lean out even .5 AFR and u will need to add a little to the timing because of the slower flame.
The basic Things that influience effiency, require change in timing for a given engine, are
load.. hence a VA advance for more advance for lean light load cruise.
RPMS...more rpms the time to fire becomes less AND the dynamic compression of the engine changes
The combination/ balance of cent advance and the VA parts of the dizzy work in conjuction of rpms, engine load (vaccuum)

Little over simplified but hop u undrstand the basic principle...
Change the mixture re dial in the timing need to happen.
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jono
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Location: New South Wales, Oz

Re: ?fit balance line impco freshie for stoic??

Post by jono »

As you may recall, it is a bit funny me giving thanks to Steptoe :) , this system has been up and runnuing for 10 years and umpteen km and was time for a change. The vac advance is in use, not tested it actually working though. On this subject, the other engine comparison has no vac advance - due to the throttle body not having such a port ( Mitsubishi Lancer ? on a Subaru).

The original conversion to dedicated LPG was throw it in and drive - not subjected to such technology as the Vane unit I have in my hands now :) - this is its real first chance to shine its best

Other comparisons are the better economy comes from a new mixer, new engine, 20/60 .235 cam just right for potential turbo and fuel of choice, plain old dizzy whereas the old mixer, old stock factory engine runs a tweaked dizzy with max advance of 28 and initial 14, stock cam designed for wetrol

Just trying to set some base values.
I have a copy of a CA100 mixer specs which claims it has a balance port. At the moment I am having no luck downloading a non corrupted adobe from their website in order to view a pdf file on the CA125. Might just have to pull the mixer out again - wash bay out first and save on hand cleaner this time :(
Mr Steptoe , I do know you are more into the bigger cubes, have you played with such teensy mixers such as the 100 series ?
It may just be time for a new mixer and I just happen to have a CA100 waiting for a project ........

MLGPropane2
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Re: ?fit balance line impco freshie for stoic??

Post by MLGPropane2 »

jono,

The Impco mixers have small silver screws on the "Throat" of the mixer...and any one of them can be removed and
replaced with a nipple to access "Air Valve" vacuum. Best power, mileage, and emissions, with LPG occur at Lambda .96
Stoich for a 50/50 mix of propane / butane is AFR 15.6 X .96 = AFR 14.98. A Mix of 70% propane and 30% butane X .96
needs AFR of 15.07. I prefer to use enough "lean rings" to close the Idle Mixture screw completely,,,the WOT mix is set
with the restriction in the mixer fuel inlet.

Best Regards

Roger Wheeler

Steptoe
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Re: ?fit balance line impco freshie for stoic??

Post by Steptoe »

Mr Steptoe , I do know you are more into the bigger cubes, have you played with such teensy mixers such as the 100 series ?
It may just be time for a new mixer and I just happen to have a CA100 waiting for a project
Bottom line.. it doesant matter if the engine is a bb chev or a 1912 2 cyclinder Jowett engine, runs on petrol cng or lpg..
Change the mixtures, or any of the othe parameters and one has to change timing.
The mixers/ carbs have 3 basic circuits, idle, power and cruise....and like wise a dizzy has power (total) idle, and cruise (VA) functions to match
You say "It may just be time for a new mixer..." Well I dont dispute that, but trouble shooting on "Mays" and assumptions is very hit in miss into a very big target.
This may explain why so many of us set up out engines, dial them in, then dont have to touch them other than service for the next 15+ yrs, 120,000 miles at least.
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jono
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Re: ?fit balance line impco freshie for stoic??

Post by jono »

Thanks Roger, that is interesting info. It would be more helpful if as consumers we were informed and/or guaranteed the mix ratio of butane and propane, but we are not, take it or leave it :( Guess that is where running a car with engine management may help or hinder with timing (knock sensors) and O2 sensor control.

I think I know the screws, mind sees them on 225, better hav a closer look, must be same thread as that brass nipple with the rubber plug on it. Time to remove again and inspect. Only thing is I thought balance need greater ID 3/8" hose, so use 1/8" plug hole and fittings. Did a lot of tinkering with the turbo set up and its bal line ID's (prior to finding a vapour leak under boost, through advance diaphragm, into distributor, 2psi boost, spark, KABOOM !! :D )

Steppy, was trying to say this is the dial in tune attempt, previous ten years has been seat of the pants & drive it, with dizzy mods. Not set up by anyone else but me.

I cobbled it all together. Air is drawn through a side indicator light in the front guard, into an air filter box (V6 Commodore) just inside the bay LHS, goes through a generic multifit power steering rack boot to get across to the mixer mounted sideways on what used to be an AC bracket, so mixer mounted on the engine, draws vapour from about ten inches away with the Cobra mounted on inside guard.Vapour then travels through mild steel pipe 56mm OD for about two feet, to a 100 x 50mm box steel 300mm long, sits atop a pair of Hitachi carbs on the boxer motor (quadthrottle !!) Carbs are missing floats and venturi innards with vent holes blocked off where fuel plungers were.

jono
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Location: New South Wales, Oz

Re: ?fit balance line impco freshie for stoic??

Post by jono »

oh, and taking in Rogers suggestion of the silver screws in the side of the body for a balance take off - they are both in use as I custom made a mounting bracket to mount the mixer to the engines cast iron bracketry where the AC was.

Looking at my 200 mixer the balance port inside is a directional , almost pitot tube extra in the casting, not just a hole, likely designed to pick up more mid stream than along the outer edge of the inside airflow ?

Steptoe
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Re: ?fit balance line impco freshie for stoic??

Post by Steptoe »

It would be more helpful if as consumers we were informed and/or guaranteed the mix ratio of butane and propane, but we are not, take it or leave it
Best power, mileage, and emissions, with LPG occur at Lambda .96 Stoich for a 50/50 mix of propane / butane is AFR 15.6 X .96 = AFR 14.98. A Mix of 70% propane and 30% butane X .96 needs AFR of 15.07.
That is less than 0.1....to put that in perspective, a change in altitude in a hilly city, or ambiant temps between day and night will give differences that small.
Monitoed or unmonitored such a small diference is insignificant for our general puropses .

Dialing in any engine get the idle, cruise and power circuits in ball park, then dial in the timing curves, fine tune the mixtures then fine tune/ confirm the timing curves.
Do each of the cruise, power and idle timing separately...
IE lock the weights, disconect block off the VA,
establish the idle by turning the dizzy...note the spec
Power Fire up, turn the dizzy to give your total, make the runs above the cent all in, best time ave is your total spec.
Cruise, run 2, 1 at 30 mph the other 60 mph rpms establish these 2 pionts as the VA all in , piont in the cent curve.
Now graph these pionts / specs up and put the approiate spring weights, VA vaccuum and number dregrees and total cent in the dizzy to meet these specs...

All rule of dialing in, never change 2 things at once... If the dizzy is not locked to establish these, and unless very experianced in dailing in timing, and have a lot of graph paper, there are too many parameters happing at the same time in a dizzy in many cases...espec cruise.
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jono
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Joined: Wed May 16, 2007 11:46 pm
Location: New South Wales, Oz

Re: ?fit balance line impco freshie for stoic??

Post by jono »

Well, since having one EA81 subie engine with only 20,000 odd km giving me 540km on 60 litres with the differences being 480,000km less than my other EA81 in same model ute, 20/60 cam and 4 speed instead of the five speed my other ute delivered 70l for 540 km/ factory cam. I found it was at least idling two points too much, added one leaning ring and the results seem to be much the same each week - going further on my fuel ! I pushed it this time, so confident the not so accurate gauge was same as last few weeks and stretched it to a mile under 600kms and it took just under 75 litres and a third of this was towing at least 300kgs! An improvement of at last half a litre every 100km. The leaning ring will have paid for itself with two long tank fulls. Cheerin' :D

C3H8
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Re: ?fit balance line impco freshie for stoic??

Post by C3H8 »

The cobra reg usually has a choice of two springs. Blue -1.5" WC or orange -.5" WC. The CA125 is normally used with the blue spring. Using the orange spring will result in rich mixtures as its original purpose was to richen the mixtures in conjunction with some kind of fuel control device. You mentioned a green spring. I don't think there is a green spring made, however in the back of my mind is a vague memory of a green sping that might have been available that changed the reg pressure to -2" WC. This spring owuld richen mixtures quite a bit. I can't find a reference to the green spring in the manual so I am unsure if it actually exists.

As for the balance connection. The CA125 should have an opening marked BAL on the casting. This is the correct opening to use for balance connections to the regulator. It should be located very close the the vapour inlet on that mixer. As you have noted the reg is threaded under the brass screen specifically for this purpose.

jono
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Re: ?fit balance line impco freshie for stoic??

Post by jono »

C3 , I think I meant the spring in the mixer as have not ripped into the Cobra converter itself. Thanks, for the tip on where to find the bal. outlet port but this CA125 does not have one !

C3H8
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Re: ?fit balance line impco freshie for stoic??

Post by C3H8 »

You can make your own by drilling into the adaptor bolted onto the top of the mixer.

I belive your mixer spring is the right colour. Only one type of mixer spring exists from the factory for the mixers.

bumpstart
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Re: ?fit balance line impco freshie for stoic??

Post by bumpstart »

green spring for CA100/CA125 air valve is ( century ) US-s2-85
when the going is hard, don't retard, remember your lubrication

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