Propane Mixer Requirements
Propane Mixer Requirements
(OP)
I am currently building a turbocharged Ford 2.3 engine for racing. I'm hoping to manage 350-400hp and plan on using my readily available Impco parts. My dilemma is that I seem to be on the borderline of using one 425 mixer. Should I just fabricate my intake to accept two mixers? Or is it possible to overcarburate with mixers? In theory they should both only open according to the engine's needs and boost. Or is my theory all wrong?
Tom
Tom





RE: Propane Mixer Requirements
RE: Propane Mixer Requirements
Tom
RE: Propane Mixer Requirements
The 425 is vastly over carbureted for this engine in normal aspirated mode (read as non-boost and low speed) but will work at higher airflow rates. You could stage two 225's in progressive mode, one opening first, then the other.
I would also plan on two model E vaporizers too.
Franz
RE: Propane Mixer Requirements
I think Impco have a tie up with an Italien company BRC who make injection equipment.
RE: Propane Mixer Requirements
Being as though I have access to lots of Impco parts(but very little others)I plan to make this a budget project. Injection would be nice, but there still seem to be so many unknown factors(and costs)involved.
Tom
RE: Propane Mixer Requirements
Setting up an injection system for performance is possible but it requires special injectors (not gasoline units!) and other proprietary stuff. Also, the injection tables will have to be generated from scratch as the gasoline tables will not work. Impco will not sell any injection stuff to the consumer/installer, and there is no off the shelf Impco LPG injection equipment available. They are in R&D only.
Franz
RE: Propane Mixer Requirements
RE: Propane Mixer Requirements
For starters, set initial timing 5 degrees more advanced than with gasoline. If, and only if, you are familiar with the built in recurving properties of the Ford distributor (thats not the function of this website) recurve the total timing to about 35 deg BTDC at 3000 rpm.
Not sure what you mean by a propane chamber, the Impco doesnt have one. If you have the 425, there are two adjusting screws, the smaller one for idle mixtures, the larger for max gas flow, also called the power valve, although it will not give more power, only less by gas restriction.
To set the idle, use a gas analyzer and adjust for approx 1% CO. For the larger screw, its best to usually leave it alone unless you have access to a chassis dyno and gas analyzer, then set for 1% at full throttle load.
Franz
RE: Propane Mixer Requirements
RE: Propane Mixer Requirements
When you apply a carburetor in blow through mode, the sizing gets factored in inverse proportion to the density ratio you are targeting with the turbo-intercooler system. So a carburetor that is good for 200 hp at ambient conditions will be good for 400 (on the air side, anyway) if density is doubled. You will have to develop the gas delivery side of the system to deliver the peak required gas flow, but in principle that shouldn't be a problem if the gas regulator is pressure compensated from the mixer. I agree with franzh that one Model E would be marginal to inadequate at 350-400 hp so you better go with two. There are some things you can do with the primary and secondary springs to optimize the regulator for a specific pressure, but the passages inside are the limiting feature. Impco has developed some higher flow E's for certain customers but I don't know if they are available aftermarket.
You will also be hard pressed to find a high pressure regulator to deliver the flow you want when your tank pressure is depleted below 1000 psi (I know the HPR 3600 isn't capable), but if you plan to keep the tank topped up that may not concern you.
I know many have taken the Ford 2.3T past 400 hp on gasoline, but that's with the benefit of internal cooling via enrichment. You better figure on a decent water injection system to keep exhaust temperatures down and keep from detonating.
RE: Propane Mixer Requirements
Otherwise, you are right on target.
Franz
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RE: Propane Mixer Requirements
I'm kinda sloppy in my terminology for the Impco regulators, i.e. when I think Model E, I don't distinguish between the LPG and CNG variants, at least until the fuel is specified. They all say 'Model E' on the cover.
I guess another reason I lump them together is all the heavy duty CNG applications I did with those regulators, I used the propane vaporizor base with the CNG regulator assembly (does that make it a PEV?), to reheat the CNG after it was cooled from the Joule Thompson effect in the high pressure regulator. We did not want sub-freezing gas flowing through the fuel system potentially creating problems with fuel metering. This was a concern in heavy duty applications where sustained flows above 100#/hr are commonplace.
RE: Propane Mixer Requirements
The "P" means pressure. The "E" is the series, while the "V" means vacuum, even though the units would flow as soon as fuel was supplied (the PE and PEV CNG units.)
Sorry to get off of topic.
Franz
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RE: Propane Mixer Requirements
RE: Propane Mixer Requirements
RE: Propane Mixer Requirements
Will they be too big when running off boost, and should the linkages be staged to reduce this problem, should it exist?
I have built n/a small blocks in the past running single 425's, but never anything boosted, or anything that required 2 x mixers/vapourisers.
Ben.
RE: Propane Mixer Requirements
The Eng-Tips forum is for engineers to discuss engineering topics, not really to discuss personal projects, even though that seems to be the thread!
Note to anyone else: I am not re-directing posters for any services, this is information only.
Franz
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RE: Propane Mixer Requirements