SIMON HOLTBY

I recently converted my Z28 to run on propane to help reduce fuel costs. It is about half the price of petrol in the UK.
Performance is identical up to about 50 mph above which kick down causes the gearbox to change down and the engine power dies. Also top speed is about 110 mph and was 140 with petrol.
I can live with this although the kick down causes overtaking problems. If I want to drive real fast I can always switch to petrol.
The problem is due to the vapouriser being too small. Engine goes lean, I used a voltmeter to check lambda output. Have any of you guys converted to propane? If so can you recommend a vapouriser that will give same performance as petrol.
One strange thing about running on propane is that after 5k miles the engine oil looks about the same as the new stuff you put in. i.e it does not turn black. I guess oil changes could be extended. Hopefully engine should last longer too, although I have heard of people with burned exhaust valves. I think this only applied to engines that required leaded fuel.
Finally I'm thinking about buying a set of rear louvers. Any of you got a set in good condition. I have heard the original GM ones are the best. Let me know a price and I'll check on postage cost to see if it is worth doing.

Cheers

Simon

1988 IROC 5.7 sucks gas kicks ***

ede

no one here has as far as i know but it's pretty popular with industrial engines to be converted and a lot of industrial engines are the same or similar to the engine in your car. look at a few site for industrial applications.

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

SSC

This might not be too helpfull but at least it will give you a direction. Holley makes special carbs for propane & gas I havent seen any in a while but the guy who used it said theres no difference in power between fuels.
I dont know what the laws are in the UK but im fairly sure since your using an aternative fuel you wouldent need a cat or any emmisions equiptment, right? That might give you some options if swiching carbs is as much hassel over there as it is here. Also on a non related topic are they still making Red Dwarf episodes???
SSC

SIMON HOLTBY

Thanks for the replies. I don't expect many of you have converted to propane as gasoline is so cheap in the US.
I think the holley carb would require a different inlet manifold from the TPI unit I have fitted.
It would be helpful to talk to someone who had successfully converted a small block chevy engine.
I think the leading manufacturer in the US of vapourisers is Impco. I'll send them a mail.
For anyone interested take a look at www.lpg-kits.com from whom I bought the DIY gas kit.
Also emission equipment is not required on pre 93 cars in the UK.
I'm not really a Red Dwarf fan but I cannot remember seeing new series for sometime now.
In a recent topic fuel consumption was discussed with people claiming they get 30 mpg from the 5.7 engine. They are dreaming aren't they?
I get doing mixed driving 22 mpg with petrol and 18 mpg with propane and thats imperial gallon which is 20% more than US. As I said earlier propane is half the price of petrol about $1.86 per US gallon so it is like getting 2 *18 = 36 miles per gallon now.

Simon

SSC

Thats sad about RD .
But thats interesting I havent seen or heard of a TPI running propane I'll have to check into that might be helpfull in the future .
As far as full goes one of the moderators??? gets 35mpg with a custom prom. That might be something to look into. As far a gas prices were paying about as much 1.65$ per gallon for low grade fuel.
SSC

Sitting Bull

I had a propane kit on my old taxi, a 1979 Chevy Impala with a 350 engine. It ran great! We had to replace a head gasket once when I was down in Tucson, Arizona back in 1991. The guys at the shop were flabbergasted that an engine with like 200,000 miles on propane had NO carbon deposits in the heads. Clean as a whistle.

One thing many people don't know is that propane and gas require entirely different timing curves. If the guys who did your conversion did not recurve your distributor then take it back to them for a weights and spring change. I can't remember which way it should go, quicker or slower, but it is completely different than gas. That's why "dual fuel" setups are the worst of both worlds--they are no good for gas and no good for propane. Keep in mind that propane has less energy per unit than gas, that's why your mileage will be marginally better on gas. And while your oil looks clean, you should still change it after 5,000 kms because the additives just wear out at that time no matter what. Spark plugs will last longer, as well, though you need a good hot spark to light the mixture.

Other than that, retarding the timing will give you more top end horsepower, while advancing it will squeal your tires off the line. 110 mph is plenty for the street in my book

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1986 Camaro Sports Coupe
T-tops, variable wiper, power hatch, rear defrost, third brake light
LG4 305 V8, Hooker Shorty headers, 3" pipe into Walker Quiet Flow dual exhaust
Edelbrock Performer intake, "Damonized" Q-Jet 4bbl, K&N filter, Crane ignition kit
TH700R4 transmission and Derale cooler
Air conditioning, power windows, power door locks, power brakes, power steering, tilt wheel
Kenwood cassette, Pioneer 6x4 component front speakers
Rockford Fosgate 6x9 Punch rear speakers
Z-28 front and rear sway bars
Aluminum slots and Goodyear 225x60R15 Eagle HP tires
243 horsepower and 326 foot pounds of torque at the flywheel
_ _ _ _ _ __ _ _ _ _ _
Yea verily, and he smote the smog heathens from his small block Chevy, even from the air pump to the converter ...
Todd 1:1

Sitting Bull

Heh, heh

I remember paying a measly 2 cents per liter for propane here in Calgary back in the 80s!

That is like 8 cents per US gallon ...

Did I have a big smile on my face after paying only 75 cents to fill my 20 gallon tank? Oh yeah

AlkyIROC

Everything Sitting Bull said.

When I had my 79 4x4, I converted to propane when it was $0.15 per liter. Just after that the govt started taxing it and they now keep it at roughly 1/2 the cost of regular fuel. From an economical standpoint it's not worth converting a newer vehicle to propane with the electronic fuel management systems on cars now. It was a good switch from carburated ones though.

Propane does have less BTU's or energy per gallon so you need to burn more to produce the same amount of power. The lower cost of the fuel will still be cheaper in the long run.

Other than having to use hotter plugs the only other thing that should be done to an engine that's been converted to propane is to have the exhaust rotators welded. I never did on my 4x4 and it run fine.

Plus sides are that propane has a higher octane rating. It's around 105. Build a high compression engine and propane will be more efficient. Propane also goes directly into the engine as a vapour. Gasoline goes in as atomized liquid.

I've seen a 9 second propane powered drag car with a tunnel ram and 2 Impco 425 mixers on top of it.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

brharris27370

Doesn't propane have an octane rating of 110? So to make the same power as gasoline you either have to raise the compression on the engine or run a supercharger on it to take full advantage of the system. If you are running lean you will have to cure that first. Larger jets maybe.

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91 Camaro RS 5.0L Black Convertible 700R4
** Added so far **
*GM Wonderbar,Alston SFC's,spohn LCA's and Panhard rod
*Turbo City Inj Spacer
*Dual Snorkel Air Filter
*March Performance Pulleys
*GM 3.42 Gears with OEM Zexel POSI
*Edelbrock headers
*3" High Flow Cat
*3" Dynomax Exhaust
*Walbro 255 lph Fuel Pump
***Future 330hp Vortec Crate with LT4 hotcam and 454 TBI

SIMON HOLTBY

Yes, I have been told that propane has an octane rating of 110 also. To take full advantage you need at least 12 to 1 compression, the ignition advancing and a cam with less overlap to avoid backfires through the inlet manifold. It is a big problem with some cars with a mechanical flap air flow meter as the flap is slamed shut during a backfire and the unit explodes. I think it is OK with a hot wire MAF sensor but the air filters will be the next restriction. Automatic cars are prone to backfires during kickdown as the ignition is retarded by the ECU.
Can the ignition on our cars be advanced just by turning the distributor? When I'm running on petrol will the knock sensor protect the engine from detonation if the ignition if advanced more than stock?
The UK government is keen to promote propane use here due to the lower emissions. If you buy a new car you can get an 80% grant towards the conversion which is on average $2100. My DIY kit cost $700. So garages are making a lot of money doing conversions.

Simon

brharris27370

I would recommend DIY programming if you want to run dual fuel and play with the timing. If you let the computer retard when running petrol it will run like sh#t. If you look at the chip programming on this site you can program a chip to run 2 setups (there is wiring diagram and everything). Make on program using your current chip configuration for petrol and another with advanced timing for propane. With the wiring diagram you can flip a switch between the 2 programs and should run a lot better than you are now.

SIMON HOLTBY

I may give it a try but I think it is above my ability. Thanks

Mark 86 TPI

it works

yankeecarman

iTrader: (9)

I have duel fuel (LPG & Gasoline) on my 84Z28 here in Australia. Australia has an abundance of Propane and consequently there are a lot of cars running this fuel. I dont know a lot of the discussion of this topic. I do know that LPG tends to make the engine run a little hotter. My performance when on LPG is not as good as when it is running on gasoline. I have had it on my car for about 4 years and find it very good. One thing that does happen is that the carby runs a little dry even though I run the car on gasoline about 25% of the time. The carby sticks a little and needs to be oiled on the outside connections. I really couldnt tell you much about running LPG with TPI engines but there are a lot of cars over here that would be doing that. The price btw is 35 cents per litre compared to gasoline at 86 cents per litre. LPG has enjoyed a lower tax so far but this year that is about to change. If the price gets to close to gasoline, I will be thinking of removing the system and only running on gasoline. The miles per gallon is less for propane compared to gasoline. Any help. Sorry not to be more help on the mechanical side of things.

dankhound

Lpg has less heat enery than regualar gas. That is why you lack the power you used to have. It also burns faster so you would have to retard your timing for your engine to run properly.

Timmie

little correction.
LPG burns SLOWER then gasoline.
en timing needs to be advanced.
LPG has a much higher octane number and you can actually can run a higher compression on LPG then on gasoline.


( I know im bringing a topic back from the dead. just wanted to correct this statement )