Propane Tunning Questions?

-=TWITCH=- · 05-21-2003, 05:47 PM

What is the limit with Propane if there is one? I am running a big16g with all the mods I need but fuel mods. My only fuel mod is The IPO propane kit. I have a logger on the way and wanted to know what I could run with a stock fuel system and propane with a big16g? I am running 14-15psi right now with the propane and was wondering if anyone knows if this is safe? I have no logger right now but should have one up and running within a week or so. How much PSI could I reasonably run with just propane as my only fuel mod? Eventually I will get pump and bigger injectors but for right now what should I run?

Thanks Chris R

WillRaceForBeer · 05-23-2003, 01:46 AM

Hey Twitch, You shouldn't be pushing the stock fuel on 14-15psi, given that propane is always available at those boost levels. I wouldn't push any higher psi without logging timing, o2's and seeing how hard your injectors are curringly working. If they arn't working excesively hard at 15psi, your fuel pump can flow more (fuel pressure gauge?), and all other data checks out on your soon to be logger, than turning it up boost wouldn't be out of the question.

BTW i don't run propane yet, so i'm no expert, just a dreamer who read alot about propane injection recently.

GL with your setup man!

-Jon

sallystrothers · 05-23-2003, 10:57 AM

I favor water injection over propane injection any day. Water has infinite octane, propane has 118 octane. Water has higher heat of vaporization and it costs nothing.

Sounds risky to me to be using propane injection as your only source of additional fuel. Maybe add an adjustable FPR.

-=TWITCH=- · 05-23-2003, 12:37 PM

Well I got the logger up and running but im not really good with understanding the data. I would post some results but I can not find the tunerstein player anywhere to get the datalog from my palm to my PC. if anyone has it I really need it. I think the car is running really rich. o2 volts wehre around .83 untill the top of third at about 7000rpm they hit .95 and the timing is kinda hard for me to understand. I really need to post the results for you guys to help me out. as soon as I find the tunerstein player I will.

Chris R

-=TWITCH=- · 05-23-2003, 12:43 PM

Water has infinite octane? Water has NO octane, if you add alcohol to your water you can make extra octane but you will not get the octane level up to 115-118 level. Many my friends use AQUAMIST and that is the only way to go if you choose water injection IMO. Aquamist and propane work in a different way. Propane lets you run more boost because of the higher Octane and water lets you run more boost because of the lower intake temps. Propane is just as good as water if setup the right way! Just gets the job done in a different way.

sallystrothers · 05-23-2003, 01:08 PM

Hmmmm... what is the definition of an octane rating?

Basically it refers to the flashpoint (in different units). Water has NO flashpoint since it does not burn. Thus, water has an infinite octane rating. Adding alcohol to it hurts water injection's main purpose, and is usually only done to keep it from freezing and to lubricate the pump. You are right that water injection and propane injection work in different ways. But water injection both lowers the intake temp and increases the effective octane more so than propane. The only reason to use propane is if you have maxed out your fuel system and need more fuel. Which in that case I think it is sloppy to add more fuel with an uncontrolled device.

"Water exists mainly in a liquid state because that is its most stable inter-molecular structure. When we apply heat energy to it, its molecules begin to expand: a great deal of heat is absorbed during this process owing to water's specific heat capacity - approximately 4.2kJ/(kg.K). When the water changes from the liquid to gas state, large amount of heat energy is consumed in sustaining the process. The latent heat of evaporation is 2256kJ/kg, approximately six times more than gasoline! Because of its huge specific- and latent- heat capacity, water is the perfect liquid for regulating excess heat under certain engine-operating conditions, for example induction charge air cooling; but its biggest contribution is inside the combustion chamber where, under excessive loading, pre-ignition and detonation can otherwise occur. Such abnormal combustion is particularly common in force induction engines..."

nine5raptor · 05-23-2003, 03:32 PM

also,....

you actually inject so little propane that I doubt it changes the octane more than 1 or so. 118+92/2=105 @ 50% of each
10%=94.6
5%=93.3

see what I mean? What % are you running in terms of moles? Maybe 5% or less, I would think.

the main benefit of propane, I would imagine, would be the better atomization of the fuel in the cylinder, thereby decreasing lean/rich areas in the cylinder. This will combat knock by homogenizing burning mixture and reducing the lean spots the flame front hits (causing explosions--essentially the burn rate is much higher and creates high pressure zones).

Water injection, as explained above, combats knock by raising the octane significantly by "clogging" up the af mix and slowing the burn rate down. It takes a lot of heat energy to break the hydrogen bonds and vaporize water (disallowing it to be used to burn more a/f) .