turbo on propane



anyone have any experience running a turbo and using propane ?
turbo's and propane go together like wheels and tyres.makes heaps of power due to the octane rating of the fuel.very easy to set up also as blowing through the mixer(carby)is a lot easier than petrol.only a richer diaphram is needed,so mounting position is not changed.9-91/2:1 comp and 10lb of boost is very reliable and 15lb's is ok(if you use a copper head gasket and "o"ring the head.(water injection is also advisable steve
using an impco 300a mixer or even a 425 wouldn't it be easier to draw through? What about timing?
avoid the 300a as it is mainly a duel fuel mixer.depending on engine size ,go for the 425.on a large(over250cuin)engine,i would go for duel 425's or in my case(on a blower)i used 3x225's.my son in law uses 2x225's on his blown holden 202 cu in inline.not having accelorator pumps it's hard to over carburate.(if a little bit's good a lot must be better!!)
chinook, buickroadster. I agree with all you say. My experience with LPG started in the bad old days of wage freezes and carless days in the late 70's/early 80's in New Zealand. My dad worked at a local Power Utility Company, and suddenly all his work vehicles were LPG. Our country just about set itself bankrupt because of over spending, and when the oil shocks hit, every one was converting there sixes, V8's and even fours to funny fuel (LPG and CNG). Then the oil glutt hit, and the gear stayed in peoples basements untill the Gulf Crisis in 1991. Lately, our crap Unleaded Fuel (it has benzene levels of up to 4%, and total aromatics have been up to 56% in the first batches) has caused people with big engines ( 200 cubes and more) to look at it again. Ford and GM Holden sell dual and sole fuel propane vehicles here and in Australia in large numbers. Just about every Ford Falcon taxi in Oz is a gasser!

You guys are so lucky! Down here in New Zealand Impco LPG gear costs big time! My Falcon uses a CA 300 A5, which is used as a sole fuel mixer, no gas (petrol here, in our quaint South Pacific Pom English), just runs on Liquid Propane Gas. There are two types of CA 300... A 348 cfm carb (217 hp net possible), and a 432 cfm carb (270 hp net possible), both at 1.5 inches of Hg flow pressure.

Rated as a two barrel, they flow 492 cfm and 611 cfm repectively, at a flow drop (pressure) of 3.0 inches of Mercury. These days, the silicone gas valve "rubber" is of qood quality, and can handle low pressures of turbo -charge as a blow through system without melting or perforating. My little 2.3 V6 runs a stock engine, with about 6 pounds of boost on a small IHI turbo just plonked onto the stock rhs manifold with a welded plate. It runs the CA 300 A1, that 348 cfm number. The management of fuel air ratios, general control by vacuum and the fact that there are only three methods of fuel enrichement calibration, (all with a screw driver, spanner, or set screw) makes these systems amazingly simple. Set idel, wot, and lean cruise, then check them on a rolling road, adjust your ignition, and they stay in tune for ages!

In instillations where there is a fuel control valve, like a normally aspirated, non turbo German 2.3/2.6/2.8 Ford V6's or electronic contolled unleaded 2.8 Chevy V6's, they run really well too. A 350 Chev will like a CA 300 A5 more than the smaller A1.

But the CA225 and CA 425 are simply the best. They are worth over $NZ 500 over here, much more than the CA 300's. I'd rather run two CA 300's linked together down here, because they are more plentiful.

I've seen dual CA 425's, which have 920 cfm, run on stock 351 Cleveland V8's down here, and dual CA300 A1's on a Cross flow 4.1 (696 cfm!). My next door neighbour has a cross fire 1982/84 TBI intake from a Corvette, and runs two CA 300 A5's on his ( 864 cfm).

So long as its a big engine without a huge cam, the Impco carbs are hard to beat. They flow a great deal of propane gas, and are variable in the venturi to allow more resident fuel/air ratios than some of the best injection systems. Never run them rich like a conventional vehicle, as propane doesn't cool the exhast valves like a standard or high-test fueled vehicle. And don't run them lean. Make sure you double up on your L or E-series convertor if you are producing more than 260 hp. The E-series convertor flows the same 325 hp net as the L-series, but an L will always freeze up earlier on a big engine.

I'd always go for a blow through turbo, rather than a draw through because of the point Discokin6 raised a while back...over run back fire. A normally aspirated, non turbo six or v8 with more than half a liter of gas volume above the trottle plates is just itching for the unused LPG on over run to get ignited in the plenumb chamber, and then go back up the intake to the carb. A CA 300 has a backfire arrestor, which vents the gas to the atmosphere rather than trying to take the carby off! CA 425's don't have this feature.

This issue with over run back fire is dealth with in modern dual fuel conversions by electronically reducing the total ignition advance when running on LP Gas. Seams like propane engines can run heaps of lead on the throttle, but back fire like crazy when on a trailing throttle. The propane gas is light, and doesn't like to settle out like atomizaed petroleum does, so it wafts around looking for a fire source. The ignition advance provides it. So just think about what a slug of propane above a hot turbo will do if there is heaps of it on over-run. It may ignite!

I have seen articles with people like Ak Miller at Bonneville with a twin propane 351 runing CA 425's as a draw through turbos, though, so if your smart and its dyno tuned, then the over run back fire condition could be taken care of by reducing advance on over-run

This is way I did the blow through on my little Cologne V6 Cortina, to reduce the chance of something like that happening.

The only problem is that Impco says you shouldn't go above 9 pounds of boost in a blow through. This is to do with pressurising the convertor and slowing the flow of propane into the carby. So here again, a draw through may be better than a blow through, since the converter is "seeing" much more vacuum. Argue it with a propane conversion expert!

Oh, buy the way, there is a Falcon XF with a draw through Sprintex super charged 250 six on the "Triple Carb 2v" part of this forum. It runs an Aussie Gas Research carb. These things run Century converters, and are very good carbs. Most turbo V8's can use two of these throttle body type LPG carbs, and they can flow 350- 450 cfm depending on the version. Some are staged, some are simultaneous, but they are quite a revolution in dedicated propane fuel systems.

Just a thought:-
One method of tameing a high boost turbo is setting up an anti-detonation injection system. I've said there is no cooling affect from propane, and holeing a piston or taking out valves is not a good look! Throw in some water or water/methonal on wide open throttle, and divse a system to dump the same mix into the plenumb chamber above the throttle butterfly on over-run. Get a shop manual and study the 1978 to 1982 over-run enrichment circuit from a Mazada RX7. This should allow you to optimise the ignition on your engine, without ruining exhast valves from high exhast gas temperature.
thanks for the response xecute and after reading your comments I'm a little nervous.In Canada propane is plentifull and parts are very common, for instances I can gat used impco 425 mixers for about $25 cdn.. So upon your rec. I would use a 425 ,I have one on my 460 which is in the truck now. I want to use the 300 -6 because my fuel mileage with the 460 is horrendous and I thought that with a turbo I could have my cake and eat it. Would a turbo give me the low rpm response I want in the 2000 to 3000 rpm range ?Could I use a msd unit to control my timing?
Have you thought of using an AU Gas throttle body in a blow through set up. Ive set quite afew older fords up with this bit of gear and always thought a blow through would work well.
what is an AU gas throttle body ? I had planned on using an efi intake with the thraot hogged out to fit 5.8L throttlebody .
As fitted to straight gas AU Falcons. It simply bolts to any falcon throttle body mount and operates as a gas distributor (Similar to a gas stove only inverted with holes on the inside) it is a bit restrictive but for a turbo it would work well!!!