How to make a LOW COST CNG Compressed Natural Gas conversion Kit work the best.
How to set up your engine to get the most out of CNG Compressed Natural Gas system.
Most of the information that is in this article is my testing on a 1999 VW Beetle 2L AEG but will work on a lot of engine that are BI-Gas CNG Conversions and those that are using hydrogen injection add-on’s like run your car on water.
I lot of things have been said and posted on the web on CNG cars/ Conversion Kits. You can’t do this or this will not work a lot of this is miss information and here say.
Back in I think the early 70s leaded fuel was remove from the USA at that point all car manufacture that were sold in the USA had to make there engine last with out using Leaded fuels. This means the valves and seats as well as the guides need to last with out lead as a lubing agent.
So you need to run the best synthetic oil in the engine to start with CNG or BI-Fuel. This just gives the valve guides a little more lubricant and with CNG you can go a long way between oil changes like 20K+.
On CNG you can run a lot more timing in the engine this will give you more power and better mileage. So how can you do this on today’s new computer controlled engine with out reprogramming the ECU? What I did on the 2L VW engine is I started with making up a new crank positioning sensor that was smaller then the one in the block. I used some VW ones I had from ABS/other engines sensors with a plate to move them around in the hole.
This failed badly so what I did was take the original one and used a file and sanding drum to cut away the side of the sensor to relocate it in the block to get all the base timing out of it. I added 10 degrees to the base timing with out the check engine light coming on.
I use some Toyota black pan sealer to seal it they have never leaked. You must take care when sanding not to cut the wires inside the sensor or it will be junk.
I put a new thermostat in the engine you need to get it up to temperature as fast as you can for it to work on CNG the best.
So for the BIG change CNG likes some timing witch I have added now for the compressing CNG can take a lot of it at 120+ octanes. I went to the way back machine for this one.
In the 70s I and my older brother were big Chevy guys and Street Drag racing was our game. But back then if you needed some thing to make you go fast you had to build from a block of steel or aluminum. So working with steel truck head gaskets to get the best small block deck height and compressing some times you would stack them up.
You will need to check out a few head gasket and check there thickness for VW they are made of 3 pieces there are steel out side gaskets with a thick aluminum middle and a few rivets’ holding it all together. I drilled the rivets’ out and tossed the aluminum middle. I used a copper sealer spray and you do need to pull the head at this time yes the head comes off there is a trick to using the copper sealer. Now put it all together and you can check the compression you will see it has gone up a lot. Start it up O NO Bang Bang Bang I forgot I did say I did this in the 70s I forgot to check the piston to head clearances. I had to pull it apart you could see were the front and back of the piston hit the head. The pistons had a squishes band like two half moons above the deck. I did not wish to pull the pistons apart and the cost for special pistons did make sense.
So I did what we had done in the 70s was grease up the pistons top ring land with the piston down about a inch then turned it over to about a 1/8 inch from the top and the cut off the squish band. Put it all together and it ran great I used Hi Test gasoline at this time on. But on CNG it loved it so how can it be no Check Engine Light.
Well most cars have knock sensors that controls the timing if it do’s not see a set value above the set programmed limits it will give the engine as much timing as it will take for the best power and emissions. On gasoline it pulls the timing back to a safe timing but on CNG at 120+ octanes’ it runs it at the maximum. See the ECM does’s not know you pushed the base timing a head. By 10 degrees.
This should work on those that just need a little more power on a stock engine with out to much work or those that use hydrogen injection add-ons too. I will add some of the pic to the gallery soon.
I hope this helps you can view some of my work at my site www.CNGvw.com
Bob Mann
