Jeep 4.0L Propane Conversion and PCM adaptive memory reset

[zidodcigalah]

Hello, 

I have some trouble with mpgs, idling and acceleration on my Wrangler YJ 1995. 4.0. Recently went to a mechanic, he connected my PCM to a DRBIII scantool, and he told me that the adaptive factor is -80%. He did reset all adaptive memory, and I can feel improvement in mpg and acceleration. 
Is there any way to reset adaptive memory other than connecting it to a scantool? I've read on internet about touching positive and negative cables (or grounding postitve), that it empties the capacitors in PCM adaptive memory. The reason I'm asking this is because I don't have scantool available all the time, and that this error is due to a bad LPG map (I have converted this JEEP to propane).. So I would like to once again reset memory, and after PCM relearns to copy that map to a LPG controller so there would not be any differences.

[Moses Ludel]

I would only do this with a scan tool, the grounding of a positive cable or pairing of positive and negative leads sounds like a high risk to the PCM.  The good news is that you have both Mopar/DRBIII and several aftermarket scanners (like OTC) that are capable of resetting the adaptive factor in a stock Jeep PCM.  This broadens your access to tools.

So, what kind of mapping do you use for the LPG?  If you reset a stock 4.0L PCM and start with its base memory or default, that would still be a gasoline fuel map.  Did your LPG controller come with an interface to the Jeep 4.0L PCM?  Or do you program the LPG controller by itself?

Moses

[zidodcigalah]

Do you maybe have exact OTC model that can read live data and dtc's from Jeep OBDI? I've just found Snap-on mt2500 scanner, pretty cheap kit (adapters,cartridges) on e-bay. Seem like it has live data, dtc reader, testing, troubleshooting etc. so I guess I will give it a try.
In regard to LPG: after PCM relearn and forms gasoline map, I can connect PC to a LPG controller. There is no interface to Jeeps PCM from LPG controller but there is LPG auto-calibration mode. LPG controller monitors operation of various sensors and fuel injectors in different situations (idle, WOT etc) and form it's own LPG map based on that. As far as I know, LPG controler  uses Jeeps O2, MAP and is connected to fuel injectors also.

I started having trouble when bad (rich) LPG map was manually loaded so it messed up PCM maps - with long fuel trim (if I remember this property well) being like -80%.
In this application Jeep PCM works all the time even when LPG is on, only gasoline injectors don't spray gasoline.

[Moses Ludel]

zidodcigalah...OTC Genisys and Encore would be prospects for what you need to do.  Here is information on the Genisys, it's been around for a while and might be available used:  https://www.otctools.com/sites/default/files/genisys_touch_release_notes_3.1.0.32_final.pdf

Here is information on the Encore, which has been out for a while and might be available used:

https://www.otctools.com/sites/default/files/encore_release_notes_v2.5.0.8_final_0.pdf

Here is a video interview I did at the recent 2016 SEMA Show Las Vegas on the latest OTC scanner technology, which would only be available new:

http://www.4wdmechanix.com/new-otc-evolve-scan-tool-demonstration/

Any device you get must have software and adapters to work with your Jeep 4.0L engine.  I'm sure you know that already...

Interesting LPG package...Please share details and photos, others will find this of value.  I was very excited about propane/LPG carbureted systems in the late 1960s, when I-H and others promoted LPG as an option for fleet medium-duty truck operators.  GM played with compressed natural gas engines (CNG) in the early '90s, I tested a pickup with CNG for the Portland Oregonian newspaper.  

The GM aftermarket installed systems had leak issues from the supplier, and GM quickly stopped marketing these models.  (The engines ran on gasoline and could be switched over to CNG.)  Too bad, propane and CNG are a valuable alternative to gasoline and can provide cleaner tailpipes and dramatically reduced engine wear. 

Moses

 

[zidodcigalah]

LPG controller is AC Stag (i think its made in Poland), it's connected to Jeeps O2 and Map sensor. Every cylinder has it's own lpg injector ( its sequential system).  This is photo I've found on internet but my installation is similar. You can see that there is a reducer near battery, lpg hoses that go from reducer to injector rails on the right side of the engine. Also, reducer has to be connected to a cooling system. On my car gasoline injectors are wired to a LPG controller (which is not seen here) so that they are shut down when car runs on LPG. As far as I understand, when running on LPG Jeeps PCM send signal to gasoline injectors - and since gasoline injectors are closed that signal is forwarded to a LPG controller so it can calibrate itself (when you perform calibration of the system) and control its own LPG injectors. LPG controller can be accessed by PC with proper cable. I've even found that there are mobile apps that communicate with controller via bluetooth, but you need to have a bluetooth adapter connected to a controller. LPG tank is located in the rear of the vehicle. Those who are interested in this can find more info at: http://www.ac.com.pl/products-autogas/

Driving on LPG should not be more dangerous than on gasoline. LPG tanks are pressurized, but they are made of thick steel and tested on much higher pressures than working pressures (this applies to entire system). Tanks have safety valves in case of increased pressure, traffic accident, that release pressure from tank. Dangers come from installations that are not checked periodically or were installed unprofessionally. LPG can't lit inside tank (like gasoline), but danger comes from leaks that can occur on neglected system components ( like hoses, connectors) and mix with some source of heat.

[Moses Ludel]

zidodcigalah...I am really excited about this technology and have questions about your system.  (See your quote below with my red comments.)  Why were you motivated to make this conversion?  How popular is it in Europe and why?  My first attraction was as a fleet truck mechanic.  I saw the immediate gains in propane use.

I interviewed Ak Miller in the late 1980s at his shop in Pico Rivera, California.  Ak was a WWII pilot and automotive/off-road racer with a wide reputation.  At that time, he was experimenting with EFI and natural gas conversions for PG&E (a Bay Area/Northern California utility company).  Ak was a strong proponent of turbocharging and was trying to work that into the equation.  

When I got on the propane bandwagon in the late 1960s, I was primarily concerned about the fuel cost savings and the phenomenon of nearly zero wear on cylinders due to lack of fuel washing (lubricant starvation or dilution).  Engines in the truck fleet were postwar to early-'sixties and notorious for cylinder taper on teardown...Propane engines could run for hundreds of thousands of miles without cylinder taper, had virtually no carbon buildup, showed a dramatic decrease in bearing etching, went way longer between oil changes and sidestepped the roster of maladies inherent to gasoline fueled engines.  This is a substantially cleaner tailpipe/emissions plus fuel octane with a pump equivalent in the 103 range! 

That was at the time when lubricant quality was nowhere near today's levels.  Today, you could run Chevron's Supreme Isosyn formulation oil (available everywhere and inexpensively at places like Costco where I buy it for our magazine fleet!  This oil would last for 15,000 miles in a propane fueled engine, maybe changing the oil filter halfway between changes and topping off the oil.  Even the oil filters last longer.  This stuff burns clean!  

Note: The biggest break gasoline engines ever enjoyed was the changeover to electronic fuel injection and spark management.  Controlled A/F ratios and spark timing have dramatically increased the life of I.C. engines.

There were a few significant "caveats" when making the Impco conversions in the day (a carburetor-like system still available: https://centuryfuelproducts.com/small-engine-tri-fuel-propane-natural-gas-conversion-kits/automobile-conversion-kits-to-propane-lpg-natural-gas). You did not want to use a heat riser on the exhaust manifold or the usual intake manifold crossover heat passage found in carbureted V-type gasoline engines.  Unlike a gasoline engine that requires a warmed intake plenum as quickly as possible for complete combustion when the engine is cold, propane will detonate in a hot manifold.  Major truck manufacturers, for their "factory" propane packages found in medium duty truck options, would offer V-engine intake manifold gaskets that blocked off the heat crossover passage.  I-H provided factory engines like the 345 or 392 with these types of gaskets in place if you ordered the propane option.  GM offered aftermarket over-the-counter propane intake manifold gasket sets with block off plates in place.

Some systems involved a propane carburetor that completely replaces the OEM gasoline type carburetor.  Other "dual fuel" systems try to incorporate an air intake propane induction that keeps the gasoline carburetor in place.  These systems flowed propane through the gasoline carburetor body.  I'm not fond of this latter approach, as propane often leaks out of worn throttle shaft bores and anywhere else there is a gap!  Regardless of my opinion, here's the dual-fuel alternative:  https://centuryfuelproducts.com/support/generators/difference-in-conversion-kits/generator-dual-fuel-conversion-kit.

As for leaks, propane is heavier than air and gaseous: It sinks to the floor.  In my view, this is the most significant danger associated with work around propane vehicles.  In professional shop manuals, there were always caution statements about propane finding its way into sub-floor work pits and becoming a catastrophic issue when a smoker tossed a cigar or lit cigarette butt into the pit.  Electric drop cord lamps were also on the cautionary list...Ventilation of shop space was always a recommendation to clear possible fumes from floor areas.  Service pits needed to be cleared of low-hanging gaseous propane.

The pressurized fuel and tanks generally do not present a safety hazard as you note.  All hoses, couplings, the tank and any part of the fuel supply system must meet propane safety standards.  Safe routing of fuel lines, away from heat and debris damage, is a critical installation concern, just as it should be with gasoline.  The saving grace with propane is its pungent odor, you can generally detect a leak, and there are gauges for actually finding propane/LPG or CNG leaks.  Fuel tank mounting location is important, away from collision risks, passenger exposure or volatile and corrosive environments.

2 hours ago, zidodcigalah said:

LPG controller is AC Stag (i think its made in Poland), it's connected to Jeeps O2 and Map sensor. Every cylinder has it's own lpg injector ( its sequential system).  This is photo I've found on internet but my installation is similar. You can see that there is a reducer near battery, lpg hoses that go from reducer to injector rails on the right side of the engine. Also, reducer has to be connected to a cooling system.

Do you have this cooler routed to the A/C system?  If so, does the A/C need to run the entire time that the propane fuel is in operation?

On my car gasoline injectors are wired to a LPG controller (which is not seen here) so that they are shut down when car runs on LPG.

Do you have individual (six in this case) port LPG injectors?  Is there a separate manifold?  I do not see added injectors on the system in the photo.  Are they running fuel down the common rail for the OEM gasoline injectors?  Using the stock injectors to flow the propane?

As far as I understand, when running on LPG Jeeps PCM send signal to gasoline injectors - and since gasoline injectors are closed that signal is forwarded to a LPG controller so it can calibrate itself (when you perform calibration of the system) and control its own LPG injectors. LPG controller can be accessed by PC with proper cable. I've even found that there are mobile apps that communicate with controller via bluetooth, but you need to have a bluetooth adapter connected to a controller. LPG tank is located in the rear of the vehicle. Those who are interested in this can find more info at: http://www.ac.com.pl/products-autogas/

Do you rely upon the PCM and OEM distributor for spark delivery when running on propane?

This must be a somewhat popular alternative at Europe if there are apps and this degree of parts available.  Was your system specifically designed for the Jeep 4.0L engine?  Or did you have a generic system that you have modified to work with your YJ Wrangler's Jeep 4.0L inline six?

Driving on LPG should not be more dangerous than on gasoline. LPG tanks are pressurized, but they are made of thick steel and tested on much higher pressures than working pressures (this applies to entire system). Tanks have safety valves in case of increased pressure, traffic accident, that release pressure from tank. Dangers come from installations that are not checked periodically or were installed unprofessionally. LPG can't lit inside tank (like gasoline), but danger comes from leaks that can occur on neglected system components ( like hoses, connectors) and mix with some source of heat.

Agreed...With reasonable precaution, these vehicles (same as a warehouse forklift and other indoor equipment with I.C. engines) can be safe.  Mounting the tank wisely is part of that safety...Thanks much for sharing this "Jeep" technology, I'm excited, others should be!...Moses

 

 

[zidodcigalah]

Well, my Jeep has 130000 miles on odometer and I guess it was mostly driven on LPG here. Main reasons LPG is popular here is that its price is lower than that of gasoline (lowest octane rating for gasoline in my country is 95 octane and its price is 1.32$ per liter -approx 5$ per gallon). LPG costs around 0.60$ per liter so it's around twice cheaper. But there is one problem - engine consumes more propane than petrol (in some cases it can go to 30% more than on petrol). But this depends on a lot of factors: what is the type of the system, was it installed professionally, quality of propane injection map etc.

Tailpipe is a lot cleaner, lot less emissions... It's popular mostly in Eastern Europe because of its price, but it's also getting popular in the EU because of less emissions, therefore more benefits when doing yearly registration of the vehicle etc. It's pretty expensive to ride american cars in Europe if you don't switch over to LPG. 

My vehicle was not serviced so often by previous owners so it developed valve tap when its cold and I've already had to change crankshaft and bearings. But I bought it knowing this and knowing that oil in it was more like a grease than lubricant, so I can't attribute this to LPG. But I guess that I can attribute to it that when I did compression test, I got results like it just came from factory. Cylinder walls, pistons, rings, everything is like it has 130 miles on it instead of 130000. 

Now about systems, there are two types commonly used here: sequential and vacuum operated(we call it venturi here). Both of them enable the driver to select if he would like to drive on LPG or on petrol, they are dual systems. In each system it is recommended to drive on petrol until engine (and therefore reducer) gets to 40-50 ℃ operating temperature before switching to LPG. 

1. In sequential applications it works like multi point injection in petrol vehicles, each cylinder has it's own LPG injector, which is controlled by LPG controller. LPG controller is wired to petrol injectors (so it can read injector times and to cut them off when you turn on LPG). It is also wired to O2 and map sensor so it can control AF ratio. You get LPG in liquid state from tank to reducer. Reducer is connected to LPG filter (with one rubber hose). From LPG filter you get two rubber hoses that conduct propane to groups of injectors ( in my case there are two groups with three injectors in each group). Then on, from each LPG injector goes small diameter rubber hose which is hooked to intake manifold ( manifold is drilled as close as possible to engine head, mostly near where the petrol injectors go into intake manifold). This systems are a bit more expensive than vacuum operated, but they provide much better mpg  (comparable to those on petrol) than vacuum operated and you have minimal power loss (1-2%). I'm not sure if this type of system can be installed when petrol injectors are not hooked to intake manifold, or when vehicle doesn't have electronic fuel injection.

2. Vacuum operated (venturi) don't have injectors nor controllers. There is a hose from reducer to mixer (which is installed below throttle body). LPG is sucked in intake manifold by engine vacuum,  so propane-air mix is made inside intake manifold. You only need to have switch (which controls when vehicle operate on petrol and when on propane) and emulator for petrol injectors (which cuts them of if you have electronic fuel injection in your vehicle). These systems get less mpg (there were some applications with lambda sensor and one injector but they still get more power loss and worse mpg than sequential systems). Trouble with this system is that detonation could occur inside intake manifold, so it's not recommended for vehicles with plastic intake manifold. Detonations cannot happen in sequential systems.

There are some modern applications of sequential systems that read parameters from OBD2 or CAN but I'm not pretty much familiar with them.

Now about the classic sequential system: here is the wiring diagram of 4 cylinder version (this type of systems that have no OBD connection or any kind of interface to petrol ECU, everything is wired on directly ).

About your questions:
Do you have this cooler routed to the A/C system?  If so, does the A/C need to run the entire time that the propane fuel is in operation?
- Reducer is connected to engines water cooling system. It helps it to reach optimal operating temperature and later on to maintain it. If it was not connected to it it would virtually freeze during operation. I don't have A/C in my Jeep but I guess it doesn't make any difference. 
Do you have individual (six in this case) port LPG injectors?  Is there a separate manifold?  I do not see added injectors on the system in the photo.  Are they running fuel down the common rail for the OEM gasoline injectors?  Using the stock injectors to flow the propane?
- Yes, I have individual injectors (six) but there are in 2 groups of 3. Two hoses conduct propane to each group, and from each group you have three small rubber hoses that conduct LPG to intake manifold. There is no separate manifold, OEM manifold is drilled near petrol injector ports. I've marked this on the photo on the bottom of this post. You have OEM injectors for petrol and special injectors for LPG. There is no direct connection between them, but they are both wired to a LPG controller.

Do you rely upon the PCM and OEM distributor for spark delivery when running on propane?
-Yes.
This must be a somewhat popular alternative at Europe if there are apps and this degree of parts available.  Was your system specifically designed for the Jeep 4.0L engine? Or did you have a generic system that you have modified to work with your YJ Wrangler's Jeep 4.0L inline six?
-This system is generic, made for vehicles with 6 cylinders and electronic fuel injection. I have Stag manufactured system (with some parts from other companies), but I'd strongly recommend Italian made LOVATO kits (here is a link to one of its applications http://www.lovatogas.com/php/eng/lpg_systems_detail/id_39_prodotto_easy-fast-c-obdii-8-cylinders-lpg.html ).

I hope that I somehow explained this.. I'd be glad to answer if there are more questions.
Regards, Petar.

 

[Moses Ludel]

Petar...Thanks for expanding on the LPG system's details.  It makes sense that the "cooler" is simply attached to the heater hose to provide engine coolant temperature for the LPG system.  LPG does not like cold, many use a block heater to start a propane engine in the winter.  Do you use a block heater to raise engine and coolant temperature before starting the 4.0L in the winter?  Or do you simply start on gasoline and wait for complete warm-up before switching to propane?

With a sequential system like yours, you only experience a 1%-2% drop in power?  That would be very good for running on LPG, maintaining horsepower in a stock engine has always been a challenge with propane conversions.  "In the day", we talked about a loss of 10% power despite the relatively high octane.  As you share, sequential port injection is much more efficient than a vacuum or venturi system.  On gasoline, port injection/MPI (Mopar EFI Conversion Kit) adds over 50 horsepower to a formerly BBD-carbureted 4.2L Jeep inline six engine.  The intake plenum runners on long inline sixes are dramatically different lengths.  When the carburetor is in the middle of the intake manifold, the #1 and #6 cylinders suffer.  Port/MPI injection is a major gain for gasoline—propane, too!

On the Stag-4 System illustrated, the ignition spark timing is controlled by the Stag ECU, again using the stock distributor (2.5L or 4.0L, depending upon application)?  Is the Stag/propane distributor like a 4.0L gasoline engine with all spark timing controlled at the PCM or Stag ECU?  If so, are the Stag or LOVATO software programs for fuel-and-spark management well engineered?

So your LPG injectors flow propane to drilled holes in the 4.0L manifold—by way of hoses.  Propane is under regulated pressure.  This is close to port injection, but are these propane injectors really just "valves" to let propane through.  The "injectors" do not "boost" the propane pressure, correct?  The regulated LPG pressure flows through the propane injectors to the intake manifold at the same regulated pressure?  Or is there an actual boost in PSI created by these injectors?

I am very impressed with the advancements made around propane fueled EFI engines.  Ak Miller was finding his own way with EFI/propane technology nearly 30 years ago.  It has come very far since that time.  Kudos to Stag and LOVATO!

Moses 

 

 

[zidodcigalah]

No, there is no block heater, I drive on gasoline until engine gets to 90-100 deg Fahrenheit. 
I found that info on internet about 1-2% percent power loss. The thing is that I had both vacuum and sequential, I had much worse mpg and noticeable power loss on vacuum system. I don't feel any difference between driving on propane or petrol now with sequential system (except from the wallet thickness and tailpipe smell  ).

The only info that Stag ECU gets from Jeeps PCM is that of petrol injector timing. There is no separate distributor for LPG here. Distributor is the same distributor used when running on petrol. I'm not sure, but I think that Stag ECU relays on Jeeps PCM for timing (PCM controls timing from it's own sensors). I think that only thing that LPG ECU controls is air to fuel ratio for propane, based on it's own map, O2,map sensor signal and injector timing that it reads from Jeeps PCM. But I think that there are systems that read crankshaft,camshaft etc sensor data from OBD and then they control ignition timing on their own.

You can say that they are like valves. Pressure is reduced primary inside reducer, after that there is pressure in hoses that go from reducer to injectors.  As far as I know, there is no pressure boost after injectors, the propane is then sucked in by vacuum I guess.

[Moses Ludel]

zidodcigalah...I see how the factory OEM distributor and PCM "fire" the injectors and also adjusts the spark timing.  Since the spark timing responds to the OEM sensors, this is interesting.  The 4.0L engine does not use a knock sensor.  Apparently, the octane of the propane is enough to prevent detonation/ping.  The PCM is setting the timing based upon the stock petrol engine's fuel and spark maps.

It is quite a chore to map out a fuel/spark management program.  Years ago (1989-90), I built an Electromotive fuel management system that worked with a Jeep 4.2L Motorcraft distributor. This was a conventional distributor with centrifugal and vacuum advance mechanisms.  This meant that the Electromotive system only controlled fuel flow and A/F ratios.  An O2 sensor was employed plus MAP, TPS and a coolant sensor.  

The TBI unit was a G.M. 4.3L V-6 two-barrel unit.  I had no software guidelines and had to modify a default map that was flashed into the Electromotive unit.  In 1989-90 era, building an aftermarket EFI system was an "on your own" proposition.  The later Howell Engineering 4.2L retrofit EFI is actually similar to what i did, using a stock or aftermarket conventional distributor and a G.M. TBI unit.  Credit to Howell for making a standalone, fixed timing distributor work well with the TBI unit and its ECU fuel map!

Interesting technology with your use of LP gas...Thanks for creating a smaller carbon footprint while reducing fuel expense and dramatically increasing your engine's lifespan!

Moses