Propane pressure adjustment


New Member
Feb 20, 2002
I just installed my propane kit last night. When I hooked the regulator to the tank it shows 100 psi as well as the low side had the same reading. The only way I could adjust the low side was to open it all the way and bleed of the pressure with the hex head on the bottom of the regulator. I adjusted it to 50 lbs and left it there.


Is this is the correct way to set the pressure? What kind of boost are you running and at what pressure? Am I way off at 50 psi?
OK, 50psi will likely be too little pressure, I would shoot for 100psi with 75psi being the absolute minimum. Remember you also have to overcome boost pressure so 50-20=30psi, 100-20=80psi.

I never messed with a hex on the bottom of the regulator, I would simply turn the bottle off and and then activate the system to relieve the pressure then turn it back on with the regulator adjusted for low pressure and turn it up to desired setting.

As for me and what I run, my boost is set for 18psi with 24*timing and the regulator pressure is set for 100psi. It comes on aroung 12psi and I have the smallest jet installed. Basically I am running tha same tune on the street as I was at the track when I ran the times in my sig.

I have noticed that the bottle pressure depends alot on outside temp so if you have the pressure adjusted lower than the lowest bottle pressure (when it is cold outside) you will have an easier time tuning it since you will see the same amount of propane no matter what the bottle pressure and temp are.

I would say that 75psi regulated pressure would probably be the lower limit of what I would ever set it at. After that it is just a slow process of adding boost and adding propane to see what you can finally get with no knock. A chip with a BLM lock isn't a bad idea either since the ECM will try to pull fuel on the WOT BLM block when you are driving part throttle under boost and the propane is being injected. I saw mine go down to around 100 or so with the rest being around 128.
Very good info. Thank you. Its a bit hard for me to do any major tuning until I rebuild my trans but I get the idea. I just thought it was odd when I turned the bottle on and the valve was closed I got the same pressure in the high and the low. The only way I knew to release the pressure just short of wiring an activation switch in was to release it on the other low pressure fitting.

Do you ever come to Phoenix (Firebird, Speedworld)? If so let me know when. I would like to see your setup and steal some of your knowledge.

Thanks again
Originally posted by lrover2
Do you ever come to Phoenix (Firebird, Speedworld)? If so let me know when. I would like to see your setup and steal some of your knowledge.

Thanks again

I try to avoid that mess comonly known as Firebird:D and also the Phoenix area as a whole (hole). I really have no reason to go up there as we now have a track down here that you can get more than 3 runs in a night and don't have to drive 125 miles each way.

As for seeing my setup, it is classified.:eek: :D
Well I guess I will have to venture over to Tucson and sneek a peek that way. :eek: I have some friends that go to that track now and then. As far as classified you claim its all stock hmmmmm;) Your right about firebird though. That place sucks unless you catch it on an off night (raining).
I used to have the OGS kit and here is how I do it.

Turn the knob all the way out counter clockwise, then install it to the propane bottle. Inlet will be whatever PSI, SLOWLY turn it clockwise until the pressure you want is reached, it must not be higher than the inlet pressure.

That's it. Don't touch the knob and do not be bothered by what the outlet gauge is reading afterwards, no matter higher or lower than the inlet gauge. The only time the outlet gauge will be accurate is when it is injecting, but you'll be too busy grabbing the steering wheel hard :)

What you need to do is remember your desired pressure and make sure the inlet is always higher than that.
Well this propane shouldn’t be as difficult as it seems to be. My 02's are in the real low 800's and I am getting some terrible knock. I can hear it! Do you think clipping the green wire and grounding it would help? Which end do I ground or both? My 02's were this high with the alky I was running and I didn’t get the kind of knock I am getting now. Is there less tolerance with propane as far as the initial setup?
Maybe there is a possibility its because of my trans slipping. I am trying to ease into it but maybe is letting go just enough to throw things off.
Well turn the propane injection knob all the way MAX.. set the inlet to 80 or 90 PSI (with the method mentioned above) Activate it at low boost around 7 PSI.

It should give you a starting point
Try turning the boost down to a safe level and turn off the propain, if you are still getting knock then try some higher octane. If it doesn't go away then, you have other problems you need to address before anything else.
I was running 21 lbs of boost with alky and almost zero knock besides transitional. If I bring it down to 15/16 I don’t get the knock but 18 lbs and propane its going crazy. Its like my car doesn’t appreciate what I am trying to do for it. Ungrateful :eek: !
Yeah but your car was previously tuned to use alky and now you're trying to use the same tune for propane. It's likely not to work. Your setting for the alky are probably too lean for the propane. I found that when running propane you tend to lean out just little and alky you lean out alot. just my experience.

When I say lean out, I mean taking out the gasoline injected from the injectors.
If you haven't clipped the green wire yet, DO IT. You're likely suffering 'rich knock' by flooding the engine with propane.
Originally posted by S10xGN
If you haven't clipped the green wire yet, DO IT. You're likely suffering 'rich knock' by flooding the engine with propane.

I am feeling the same thing about the rich knock.
Just go back to your low boost and no propane and tune from there very slowly. Turn the propane down as far as you can and slowly up the boost untill it is running good with not knock. Also check your plugs and replace if necessary, I am guessing they are pretty dirty and look rich.

I noticed also that when running propane it has a tendency to allow, and get rich knock. Since it is a fuel and being added in descent quantitys it is pretty easy to get the mixture too rich and the natural reaction is to either add more fuel, propane, or pull some boost. That doesn't work if you are already rich and it is rich knock. I guess it just takes a different mentality to be able to tune propane, that is why I say start over and go slowly injecting as little propane as possible and tuning for it, then start making some bigger changes and more power.

I currently have mine set up for 17-18psi and very little propane using the smallest jet, a regulator pressure of 100psi, and DC of 50%. It isn't perfectly tuned and the O2's are still a little high and about .800-.820v with some false knock on the shifts (which is driving me crazy and preventing me from getting around to tuning it all perfectly)