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Old 07-17-2005, 05:30 AM
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How does temp & pressure affect injectors?

Because as gas prices soar and the air gets yellowish gray ....

and my wallet gets lighter...

and my lungs blacker....
{not to mention "actions" taken to "aquire" the cause, precious "black gold"}
I've been think about CNG.

It burns clean clean from what I hear.

And it can be bought in bottles like propane.

So instead of needing a high pressure refill station you just unplug your bottle and exchange it at the local station, or full service where an attendant changes it for you.

and if it works like I hope..

Us, as mechanics could open up our own little shops that convert cars over to CNG or gasoline at the flip of a switch! and also own the refill station, so my wallet will grow.

But if it was truely and specifically financial iI would have kept my mouth shut, but it's not.

So my question remains, how does temperature and pressure affect fuel injectors?

It seems like CNG could just be plumbed into the fuel line with a regulator and the car would run on CNG!

Hook it up with one way check valves on the gas line and on the CNG line with a switch to change between the two and it would run off either fuel at the flip of a switch.

Your thoughts and oppinions and knowledge:
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Old 07-17-2005, 03:18 PM
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everything is larger for cng systems ... the injectors look more like sprinkler heads and the press regulators are much more complex

also, gas grill style tanks are NOT for use on vehicals and you have to use auto approved tanks

conersion kits, to my understanding, cost between 2500 and 4K , but depending on how much u drive a year, the kit could pay for itself in as little as 3 years
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Old 07-20-2005, 07:27 PM
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NXS

I have a similar system on my truck now that runs propane instead of cng. They are similar, but natural gas has less energy (1000 btu's per cubic foot vs. 2500 for propane). CNG has a high octane like propane also. The problem is that the cars factory computer is set to the properties of gasoline. When you change fuels the computer has problems (ie. at startup the factory computer tests the knock sensor by advancing the timing a pre programed amount. Problem is with the higher octane the engine needs more advance to get the same result, because the computer is set up for gasoline it dosent see the knock and thinks the sensor is faulty. It sets a code and retards the timing thinking that the sensor is bad. Result, car runs poorly).

There are many other things to consider too. Gasoline is a liquid and can be regulated and pumped back to the tank (no return to the tank with propane and cng) and cng and propane are generally a vapor. So using the same injectors is not easy to do. Propane and cng also are subject to change in pressure with temperature, so this would need to be addressed too.

The system I have has a separate set of vapor injectors (made by keihin) and a separate computer. It starts on gasoline until certain parameters are met. It then switches to propane. It uses a set of injector simulators to fool the factory computer into thinking that the gasoline injectors are still firing. These simulators also turn off the gasoline injectors. The propane computer reads the injector pulse from the cars factory computer and adds or subtracts milliseconds depending on temp and pressure of the propane passing through them. The vapor injectors operate at around 30psi. It works pretty well and it is similar to some of the cng conversions which bring the gas from 3600psi to 25 psi for the injectors.

One other thing to consider is that because of the lower energy content of the gaseous fuels the engine will burn more of them to replace the gasoline. So its not quite an even gallon per gallon replacement. My particular system on my c7500 truck gets 6 mpg on propane and it got 7 on gasoline. My pickup gets 10 on propane and 13-14 on gasoline. My wifes truck, which has a different older conversion gets 12 ( both have 454s hers is tbi, mine is the sfi). I am still doing some tuning on my system though.

Now after all that you have to consider price. Since I am in the propane business it is cheaper for me. For the average guy it isnt that cheap. Propane around here goes for $1.50 to $2.30 per gallon. Gasoline is around $2.45 per gallon. Natural gas without road tax works out to be close to about a $1.10 per gallon here. Using my truck and the prices listed as an example; it would cost the average joe $0.19per mile for propane, $0.16 per mile for gasoline, and $0.18 per mile for CNG (with $0.18 per gallon( or equivalent) road tax for AZ). You factor in the cost for conversion and finding a place to put the tank and then gasoline dosent look so bad anymore. In the past there was a big enough price differential to offset the hassle of running a different fuel. Not so any more.

The only people that these type of alternate fuels benefit are people who are in the energy industry( who have access to cheaper fuel) or people who are really concerned about the tailpipe emissions of their vehicles.

Hope that answers your questions sorry for the long post.

John

Last edited by propaniac; 07-20-2005 at 07:31 PM. Reason: forgot somthing
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Old 07-20-2005, 10:43 PM
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No, don't be sorry for the long post. I really learned a lot from that, you almost reminded me of Hank
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Old 07-21-2005, 09:05 AM
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Propane and propane accessories
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Old 07-21-2005, 09:18 AM
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Roughly, what is the cost of a controller & injector setup like you mentioned?
Quote:
The system I have has a separate set of vapor injectors (made by keihin) and a separate computer. It starts on gasoline until certain parameters are met. It then switches to propane. It uses a set of injector simulators to fool the factory computer into thinking that the gasoline injectors are still firing. These simulators also turn off the gasoline injectors.
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Old 07-21-2005, 09:24 AM
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{not to mention "actions" taken to "aquire" the cause, precious "black gold"}


HMMMMM.....
FUNNY????
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Old 07-21-2005, 09:39 AM
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I don't find anything funny about it and I don't think bracketeer does either! I'm really just looking for the solution to the worlds problems, not to mention my own.
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Old 07-21-2005, 10:22 AM
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Quote:
Originally Posted by NXS
I'm really just looking for the solution to the worlds problems, not to mention my own.

SUICIDE MAYBE?
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Old 07-21-2005, 10:43 AM
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I'll leave that to you and the other soliders out there.
Thou shalt not tempt thy God.
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Old 07-21-2005, 02:04 PM
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The system I am using is made by a company called Prinns, they are in Holland. I got it through a place in Canada. The kit which includes the computer, injectors, vaporizer, and lockoff (everything you need under the hood)is a little under $2000.00 US.

Easy there fellas

John
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Old 07-21-2005, 07:16 PM
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you might find this a good read
http://www.kettering.edu/~lpgvan/SAE-LPG.html

IMO that is the way to do it (Liquid and not gassious injection).

If the motor is made to run on 'pane it will get the same mileage as petrol and have more power...it just won't be cheep to build the injection setup.

Also IMO CNG is only a good idea if you get the fuel for very cheep.
CNG is about 1500psi in the tank. Also because it is still a gas at that pressure the tanks will need to be HUGE in order for you to have much range.

'Pane on the other hand is liquid at about 150psi, has stoich fuel mixture energy ratings about the same as petrol and is about the same density. What that means is that the tanks won't take up much more room then your factory tank (they are cylinders insted of boxes so they use the space a bit less efficiently).

My plan is to have a 'Pane powered 67 Firebird...but it looks like even buying the f-body is a few years out I might start messing with 'Pane/NO2 injection in my S10 just for fun
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Old 07-21-2005, 07:48 PM
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At a plant I worked at a few years back, a snake-oil selling engineering manager convinced somebody to convert our heavy duty hilos to CNG from propane. It was a huge headache.

We also built some CNG converted Econoline vans. It was more of an experiment and publicity stunt than anything else, if it worked better a lot more people would be doing it.... but it does have its place for those who can get the fuel cheaper or are handling it anyway.

When the people in high places who control tax policy and such decide we need to use alternative fuel they will make it economically attractive.... I see corn juice in my future if I live long enough.
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