Engine/Transmission (1994 - 1998) Tell me about HVAC

[biggy238]

I want to know about HVAC. I know alot of you guys have him in your sigs.



After that. I want to know about propane injection. I searched and founds HVAC's run down on gasseous love and some guy being rather combative about their systems, but it was all written in 2000. Are there any improvements?



I don't get the whole thing because propane isn't a catylist in a combustion reaction and it also doesn't "burn slower" like marco argued against hvac's explainations. Chemically there is no such thing as burn slower. either reactants react or they don't in combustion, which is all based on stoichiometry.



This left me thinking that the only true advantage to propane is that it combusts in the combustion chamber slightly before diesel is injected. In essence the propane ignites the diesel because the propane is already burning, which creates a more complete burn of the diesel fuel before any of it exits the combustion chamber. This would have an affect similar to an egr system because it completely burns the combustion gasses. This give higher efficiency and ofcourse more yield.



If i'm off badly, someone please tell me whats actually going on with some chemical validation.

 

[Bob4x4]

Hvac was one of the first to unleash the 24 valve power,He is no longer with us. R. I. P. Nowel is missed by all of us that knew him.



I haven't played with propane myself. I live drug free. It is not like egr,egr displaces oxygen thereby cooling the combustion,which reduces nox.



Bob

 

[Vaughn MacKenzie]

Biggy your post really brings back memories



I too read all the propane discussion and its advantages such as more complete combustion, MPG, etc. etc. While HVAC was one of the early proponents of propane I wasn't that interested in it and thought it was overrated. I disagreed with the higher MPG arguement because while it gave you better numbers on paper with diesel mileage, combined MPG was not as good.



I know in 2000 HVAC set up his propane and ran it quite a bit. He had a tank in the back of the Red Rocket and left it on most of the time when I was riding with him once that year. As I recall he had it set to come on at 5 lbs boost. I had him flip it on and off and there wasn't that much noticeable difference in normal driving.



Vaughn

 

[biggy238]

The performance to PITA ration was what i was after ultimately Vaughn so thank you. So what happened to Nowell?



The reason I found it similar to EGR was the fact that it reduces harmful emmissions by dropping NOx, It just accomplished the task in a round-about way.



Does my thinking on he combustion make sense? The compressed air in the cylinder ignites the propane before diesel is ever introduced doesn't it?

 

[bmoeller]

Originally posted by biggy238

So what happened to Nowell?

Read it here-



http://turbodieselregister.com/forums/showthread.php?s=&threadid=87807

 

[biggy238]

I've got to stop typing in the dark. . I leave out too many letters.



I read 3 pages of that post. What you are is how you are remembered.

 

[CUMINNTSTRKN]

Originally posted by biggy238

The compressed air in the cylinder ignites the propane before diesel is ever introduced doesn't it?

this exactly what happens which is why lpg causes detonation, which is very harmful to our head gaskets!!!!



jim

 

[JoshPeters]

Originally posted by CUMINNTSTRKN

this exactly what happens which is why lpg causes detonation, which is very harmful to our head gaskets!!!!



jim

My question is why does it produce more power then? I know 2 trucks that have it. Yes it does smoothen out the power pulses (less knocking). But it also is producing less soot, equaling more power out of that ammount of injected fuel because it is being burnt more completely.



Still learning... .



Josh

 

[biggy238]

The pre-ignition of the LPG ignites the diesel as it is injected. The diesel reaches its ignition point more quickly, which should give the fuel a more complete burn. (reason #1 for more power and reason#1 for less soot)- exactly what you said.

The propane should carry more oxygen to the reaction chemically(reason #2 for more power), which would explain why people consider it an oxidiser similar to nitrous oxide.



It can't be a catylist because the gas is consumed in the reaction, again backing up the oxidiser idea.



The thing is i'm still learning like you said, and i'm just guessing at this. It's been a loooooong time since i've looked at the chemical basis of all of this. But, those are the two things I think back up what is happening.

I don't get the knocking being smoothed out. In theory the temp of the compressed air in the cylinder should ignite the lpg just before TDC which would cause a serious knock if the amount of gas was too high. The lpg would ignite just before TDC (i don't know the timing of the fuel injection yet) which would in turn ignite the diesel fuel more quickly than if the compressed air were to ignite the fuel by itself.

 

[JoshPeters]

I think it smooths out the knock similar to the new common rail engines... it ignites earlier smoothing out the power pulse/ignition pulse giving it a smoother pulse, elminating/reducing the knock that we hear.



Josh

 

[T. Baker]

It is my understanding that the propane does not ignite until the diesel is injected then it burns all around the diesel helping to burn it completely.



The reason it doesn't ignite on compression is because it is way to lean for self ignition. If you run enough propane it gets close to stochiametric ( proper mixture for self burning ) and will pre ignite causing a bad knock and posible engine damage.



Proper mixture ( stochiametric ) is very improtand for self ignition. without it you get no fire. That is why a gas engine won't run if it is flooded or is too lean even though there is a hot spark in there with the fumes.

 

[Forrest Nearing]

I thought propane had a lower ignition temperature than diesel?

 

[T. Baker]

I don't know but I stand by my guess that it has to be stochiametric to light off - to leen and it won't burn without the help of diesel.

 

[jponder]

How in the world can propane or butane injection add oxygen to the system??? It is fuel, It is a smaller chain hydrocarbon than diesel but its the same thing FUEL!

 

[biggy238]

If that is the case what do lpg forklifts run on? It isn't exactly self igniting. . friction due to compression should ignite it in a diesel. I was basing that on otto diesel's original engine (which ran on coal dust initaially)



Jponder: the chains don't include oxygen??



See this is what i wanted to know. What is the chemically and physical basis for the performance. If propane were just an extra fuel it would kill the reaction i would think.

 

[biggy238]

And forrest:



I thought almost all fuels other than kerosene (and it's refinements like jet fuel) have a lower ignition point.



Thats why I think the propane is burning before the diesel is injected.

 

[jponder]

The chains absolutely dont include Oxygen. Methane, Ethane, Propane, Butane and their associated dehydrogenated varieties have absolutely NO Oxygen in their chains all the way up to 1. 3. 5 trimethyl pentane which is what most people call octane or GAS there is no Oxygen in the chains its pure hydrocarbons. Propane and Butane is fuel plain and simple. It is like diesel except its a smaller chain and forms a gas at lower temps due to low molecular weight. Butane for instance boils at . 5 degrees centigrade

 

[T. Baker]

Biggie are you forgetting that there is lots of air going through a propane carburator before it goes into the fork lift? There is no oxegen in propane. Propane is a hydrocabon chain just like the rest of the fuels - hydrogen and carbon that turn into Co2 and H2o when oxidized ( burned ).

 

[biggy238]

Well to put it simply, one can't forget what he has never known. And secondly, My comment about the forklift was in response to the idea that propane MUST have the diesel to ignite. This isn't true. All it needs is oxygen as in any combustion reaction. Spud launchers are an excelent example. Air, hairspray( butane propane, methane and some others) and a spark.



I've only experienced a level 105 chemistry. . which I managed to fail twice. I picked up alot *(should have passed the second time) but I hate homework. I haven't had the chance to experince any chained hydrocarbons. I appreciate that you've eliminated the roll of propane in the process (albeit aggressively so) but I'm now interested in WHEN it ignites. I also don't see where things go if stoichiometrically we could consume as much diesel fuel as propane in this reaction. IF propanes potential energy yeild is released so much more efficiently, why are we wasting time with diesel fuel? There's something to this thats being left out.



My question is this. Why add a different fuel when we already have an abundance of another one to power the reaction?



Like I said, i'm asking and learning. . not preaching.

 

[biggy238]

O. k. so i'm getting this.



A lean mixture yeilds no real performance.

A rich mixture causes the knock (preignition)



Get it right per fuel injection and the diesel in conjunction with the propane ALMOST completely oxidise, where with just diesel there would be oxidants left over, which equates to lost power and higher emmissions.



That alone could have sparked the catylist thoughts.



This also explains why i've seen propane in conjunction with nitrous oxide, which i do believe is an oxidiser. Ofcourse i'm probably wrong there too.