Impco CA125 question...

Propane, Butane, LPG, GPL, C3H8, C4H10
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Location: Burlington, WI!!!

Impco CA125 question...

Post by schwoch1 »

Hi all, this is my first post for me, but I have been lurking for a while ;)

I am in the process of gatheriing parts to do a dual fuel conversion in my 1990 Volvo 740 with a non turbo 2.3 (B230F).
My main question is, can I modify a standard CA125M mixer to operate the same way as the CA125M-10 (full air valve lift). There is a considerable price difference between the two units and I am an ASE master certefied tech. with 15 years of experience, so a little modification work don't scare me in the least. Just looking at some of the poor pictures that I have of the -10 unit, it looks as if there is a vacuum solenoid that I presume puts full manifold vacuum to the mixer diaphragm to open the it fully. Am I thinking in the right direction or am I totally wrong, or do I even need to use the -10 unit????

Also 1 last question, I was told by some of the local so called "experts" that I am asking to make a bomb because the of the large intake plenum volume that most EFI intakes have, but when I see some converted Ford and GM V8's that have HUGE intake volume and they seen to operate just fine for hundereds of thousands of miles (just seen a 5.4 Ford V8 in a E250 van with 745,000 miles on it, all on propane)or should I just tell the so called experts to, um, mind their own business.

Thanks for any help that is received, and I am looking forwards to hearing back from you all!!

Mike Schwochert

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Joined: Thu Oct 07, 2004 7:57 pm
Location: Central Texas


Post by franz »

The CA 125 will work fine without the solenoid, since fuel injection systems monitor manifold vacuum or mass airflow. Now, if it were a carbureted system, you would indeed need to lift the diaphram to avoid choking the engine.
As for the plenum, that too is a problem. Your "experts" are correct, it is potentially an issue. That 5.4 with over 740,000 miles on propane without a manifold burst is a rare bird, something I suspect has popped in the past.
Large volume intake manifolds have a lot of air and fuel in transition, and when a closed loop fuel mixture sees a change in fuel mixture as indicated by the O2 sensor, the change is managed by the vaporizer, which changes the pressure of the fuel sent to the mixer, which then alters the air-fuel mixture in the manifold. An engine can rotate up to 20 times before the changed air-fuel mixture reaches the O2 sensor, and there the backfire occurs!
Now, if the system were open loop, the chance of a backfire is greatly reduced.

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