I have been running my car on propane for some time now. Initially the vapouriser was way too small but I have now bought the largest one available. The gas supply pipe has a valve which is controled by its own ECU and takes readings from the lambda sensor and throttle switch. It tries to run at lambda other than when you accelerate during when it quickly opens the valve.
It is a much simpler system to that controlling petrol and I can tell from monitoring the lambda voltage that it cannot regulate mixture as well, hence 15 mpg on propane and 21 on petrol.
I'm still finding that at high engine output the mixture is lean, lambda voltage is almost zero, on petrol it is 0.6V .
What I would like to do is burn a prom that will add petrol when it is needed.
I have spent the last few days reading threads on this section and have learned a lot, thanks. I already have an EMP20 programmer and plan to use a AT29c256 chip and as a matter of course convert to ARAP code (disconnecting 9th injector). I'll also be using WINBIN.
What I initially thought of doing was setting most of the MAF fuel settings to zero and then increasing fuel in MAF 5 and 6 to half their current values then going for a spin to see if mixture has improved.
Questions.

Is this idea feasable?

How does the fueling work on closed loop. Open loop it takes the values from the Eprom but when closed loop does it moniter the lambda sensor and injects as much fuel as it likes or only a percentage difference to the open loop values in MAF 1 to 6.

If the ECU goes in to limp home mode it uses fuelling from another chip? if so mixture will be way too rich I plan on connectin a relay to the warning light to kill the propane. Is this a good idea?

In Winbin what is DFCO, BPW factor, ESC and when it says Delta LV8 what does the delta mean?

I would like to be able to switch to petrol only could this be done by switching to a standard chip ie swop between 2 EEproms (prom pak?)

I compare my engine to having a carb and fuel injection fitted. I want to use the carb as much as possible but use the FI to correct the fuelling.

Any replies to any of the questions greatly appreciated.

Simon

88 5.7 camaro

 

Interesting! So is propane cheaper than gas there? I just want to double check a few things first- you are running tpi? How are you running the propane? (how/where is it physically injected into the plenum?) What is the ecu that controls the propane? And what tables are available to tune in the propane ecu? As for the decreased mileage-propane will not give you as much power output as natural gas and even less than gasoline.
Closed loop it looks at the o2 sensor (lambda), and adds or subtracts fuel to try to keep it at 14.7:1. Does the propane ecu attempt the same? The same A/F ratio?
I take it you currently have the original ecu fuel disabled? How? I see what you're getting at-adding a little gasoline in with the propane-but I'm not sure how that would work out. Anyone else on that one? Or are you thinking of adding propane to a primarily gasoline system?
I'd try to increase the flow at "power enrich" with the propane first-maybe a custom larger valve.
Limp home mode-it uses "default" settings from "another chip", so your fuel would be way off then.
DFCO=deceleration fuel cutoff, BPW=base pulse width factor, ESC is the knock control.
I know that you can add in propane to a diesel engine in the intake as a power/milieage adder, but I'm just not sure how it would do with gasoline.......

 

Thanks for the reply 'drive it'. In the UK gas/petrol is $5, propane $2.25 and heating propane as found in heating/camping bottles is $1 per US gallon. As our cars are thirsty by european standards and petrol is so expensive the only realistic way for me to run my car is on propane.
My car is an 88 5.7 TPI Camaro with auto box. Kind of turns heads like a Ferrari does in the US but other than fuel costs its so cheap to run parts seem so cheap.
I fitted the system myself the propane tank is 55 litres 14.6 usgal and fits nicely under the cargo hatch/speakers. A pipe runs from this to the vapouriser unit which is in the engine bay infront of the brake servo. Its a sphere about 7 inch diameter and converts liquid propane to a vapour. Engine coolant also circulates through it to stop it freezing.
I cut the rubber hose between the throttle body and the MAF sensor and fitted a 3 1/4 inch mixer which is where the propane is injected. This reduced the diameter of the intake but I have found it has next to no effect on performance.
When I first installed the propane I did not have a propane ECU. Gas flow is controlled by how hard the engine sucks. It sucks on a rubber diaphragm in the vapouriser which opens a gas valve proportionately. Some guys leave their cars like this but mixture control is way off and I often got an engine warning light with fault codes for engine too lean or rich.
Next I fitted a lambda control unit which is a valve in the gas vapour pipe controlled by a stepper motor this has its own control unit which is connected to the lambda sensor and throttle position sensor. It is not programable at all. If the mixture is too rich it weakens it and vica versa. It is crude as it is always adjusting for what has happend than what is happening.
If a custom propane engine was built it would have more power than a gas engine as it is 110 octane. A gallon of diesel has more energy in it than a gallon of gas but as it is lower octane power is less, but economy is much better!
As it is at the moment performance is very similar on propane but as I said if I floor the throttle from a stop it cannot supply enough gas and accelerating hard above about 80 mph the lambda voltage gets very low almost zero.
I could get over 20 mpg on propane by restricting the gas vapour pipe. This would provide better mixture control for normal driving as it swings way too rich at the moment but top end performance would be even more reduced . But I would be happy with this if I could richen the mixture with gas.
It is kind of like this.. Say some one gave you a carb to fit on your car from a small engined car and said all the fuel it used was a 1/4 of the price you would be tempted right? You could still keep the original fuel injection system also but all the fuel it used was full price so you would only have that operating when you had too.
At the moment when I have the engine running on propane a relay switches power from the injectors. I dont get any warning lights! I'd like to reconnect these injectors and have them adding gas also. At the moment if I did so the engine would get about twice the fuel it needed.
I have Craig Moats scan software working and was thinking that if I find values of air flow/ MAF voltage at which the mixture is lean I could some how add gas. If I set all the 6 MAF tables to zero does this mean no gas is injected? I could then get some data running on propane and increase the values in say table 5 and 6 until lambda voltage is increased.
I'm kind of new to this prom programing but I'd like an expert to let me know if it can or cannot be done. If it can I'll try and work it out.
Finally I'm desperate to get hold of a 29c256 chip they are impossible for the DIY guy to get hold of here. If I send some $ or something else as payment could someone help me out please.

Thanks for reading

Simon

 

OK, now I've got an idea of what you're trying for. I'm no expert, but I'll try to help.
I would put volt. back to the injectors; you should be way rich then, so rich it would have blms below 108 and would have a hard time running.
Instead of changing the maf tables first, try to change the inj. constant to get in the ballpark of 128 blm's. It's gonna' take some trial and error, just err on the rich side for engine safety!
This is just using the same principle as "regular" tuning. If you enable the inj. and it's rich at all maf air flows, then change the inj. constant to get it close across the board first. So if your blms are low, tell the ecu that the inj. are bigger so it gives less pulse width and thereby leans it out.
Then if it's just lean at upper gps airflow-non PE-adjust the maf tables. However if it's only lean at PE mode, then adjust the PE % change to A/F ratio vs rpm table.
Now another question on the propane system-if the pressure in the tank drops, is there a safety to cut off the engine? Because if you're running both fuels and you lose propane press. it could still run, but with dire results for your engine if it goes way lean!
The only problem that jumps out at me is the inj. pulse width may be so short that it has a hard time with "proper" metering of the fuel, but if it's at higher rpms, then it shouldn't be as bad as too short of pulsewidth at idle.
And yes you could just swap chips when you want to run on gasoline only. Sounds like an interesting project!
On the AT29C256 prom-just e-mail me your address of where to send. Good luck

 

Thanks again for the reply. Firstly in answer to the running low on propane question. I had not considered this problem however I will fit a pressure switch in the gas line to detect low pressure.
As we mentioned before if the engine goes in to 'limp home mode' the fuelling will be way too rich as it does not use the eprom values any more but uses some other prom right? If the warning light comes on I plan to connect a relay to kill the propane and run only on gas so it will be OK. Also I'm thinking of wiring this 'propane' low pressure switch to actually switch the car in to 'limp home' mode. This could be done by breaking a circuit to say the MAF sensor. Hopefully all this will cure 2 major proplems. So if I run out of propane car will run on gas only but car will be in 'limp home mode' which should be OK to get me to the next filling station. Also if I get a warning light for any other reason car will not have gas and propane (too rich).

What I'm now thinking of doing is removing the lambda control unit for the propane. I think this will only cause problems as it will fight against the cars ecu also trying to get lambda. I'm thinking of setting the vapouriser to provide say 80% of the fuel requirement (obviously 100% is ideal but not acheivable) and so the car/gas ECU can now do all the correcting.
I'm still learning about BLM, INT and cells. Please correct me if I'm wrong here. I think there are 16 BLM cells which increase proportional to MAF voltage/airflow or do ther also increase due to other factors such as RPM?
In a given cell it tries to acheive the correct lambda voltage/mixture if the mixture is correct it sets a value of 128 if mixture is weak BLM will be set higher and lower if rich. However I got the following values ideling on propane. Closed loop.


Lambda voltage 610, 234, 553, 632, 119, 663, 155, 194

BLM All 160

INT 179, 176, 180,180, 180, 178, 177, 180

These values were obtained while ideling in cell 0. I thought if mixture was rich BLM and int was less than 128? I'll send the scan file to you. Works with Excel.

Thanks for offering to send me an eeprom. I'll mail you my address. Please let me know yours I would like to send you something in exchange. If I'd sent you money the bank would get most of it in changing the money to dollars.

Simon

 

Forgot to mention..

Running with propane and gas (very rich) as you mentioned may cause a problem of a backfire through the inlet manifold destroying MAF sensor and air box. I think I may start by setting injector size large say 40.
Also if I do run out of propane and car runs very lean only on gas will it not throw code 44 'lean exhaust' and car will be in limp home mode so it will be OK.

Simon

 

Back again!


Just looked throught the scan file and I have a Code 44 'lean exhaust' . I cannot remember the light coming on for it. Maybe that is why it has set all the BLM values so high.

Also got a code 34 'low airflow'. Sometimes when i start the car when it is cold it runs bad. Searched the archives and it is a faulty MAF relay. I'll get the codes cleared and see what BLM values I get.

Simon

 

You had a few questions in there-hope this covered most.

 

Simon, could you please post a list of what parts you bought to make it possible to run the car on propane?

I also have a TPI Camaro, and gasoline prices are almost as bad in Sweden as they are in UK....

 

I'm late home from work tonight. I'll mail you later with more info but I bought the kit from www.lpg-kits.com I think total cost was about 700 pounds. The site has a lot of info.

Simon

 

I went for a test drive with the laptop today. Having reset the ECU I first drove about 10 miles on gas and found all the BLM's were OK mostly about 130. The injector constant is set at 23 lb however I thought the 350 had 22 lb injectors? If this was changed it should be OK.
Then I cut the gas and switched to propane. The scan file I sent you showing the car running lean at idle has been corrected by adjusting the idle screw on the vapouriser. The BLM values were OK up to about cell 10. Yes they were a bit up and down but there is no way the propane control is going to be as accurate as gas fuel injection.
As I thought it is at high load/ rpm that I need to add gas. Can this be done can I switch gas off totally at low load and on a high?

ZaphodB, You need a propane tank, vapouriser, mixer and lambda controller. Vapouriser needs to be the largest you can find. Take a look at the web site I mentioned and do a web search for LPG and most of your questions should be answered. If not let me know. Is LPG common in Sweden?

Simon

 

Nice idea, but you might research some more on how propane effects engine life. It's absolutely brutial on exhaust valves, and seats. They why they generally use it in low performance applications. Yes there are some exceptions but it's a sruel chemical to tame. I'd first worry about getting the gasoline end of thnigs right, and understand how that works then worry about making it a dual fuel engine.

 

Propane conversion was popular in the UK in the seventies but engines did suffer as you mentioned with exhaust valves and seats. This was mostly due to engines requiring leaded petrol and there is no lead in propane. With the arrival of lead free engines/petrol in the nineties (we are a few years behind the US) engines no longer require lead and so it is now considered that propane is OK.
Infact it is considered that propane is better as there is no carbon build up in the engine as it burns cleaner and the gasses that blow past the pistons contaminate the oil less.
110 octane fuel I guess burns hotter though causing problems.
I hear arguments both ways on this subject.
Yes I plan to do some tunning on petrol/gas first to learn how it is done.
Thanks

Simon

 

First, I am NOT an expert on propane. I have looked at converting on other vehicles in the past but never did due to some horror stories.

I have a buddy that converted to propane on his **** F250 w/ camper and a 460. We have a LOT of hills and some grades can be over 8% for 25+ miles. (The wife and I play a game where we guess how many dead vehicles we will see when we drive some of these roads - 1 point for a car, 1/2 point for a motorcycle, 2 points for an RV towing a car and double points if on fire).

Anyway, after a summer of driving his camper converted to propane he started noticing a serious loss of power and overheating. Turns out he burnt the head gasket between two cylinders. Worst, it had basically burnt a hole between both cylinders as if the propane had acted like a cutting torch and he basically toasted the block.

He took his truck to a few mechanics and propane specialists who said the install was not "the best", but the install itself did not cause the problem (they were not willing to testify in court that the install caused the problem so my buddy could sue for the new motor).

After a little more investigation and talking to a few more people he learnt that this is a very common problem on people that convert camperized vehicles to propane that hope to save a buck. On flat land, where the vehicle may not see any heavy loads, they seem to have less problems with propane. But in mountainous areas where you can have heavy loads on the engine, propane engines seem to have a high failure rate.

Common problems are burnt valves (as mentioned above) and head gaskets. The problem my buddy had was very extreme and I had never really ever heard of an engine burning through to two cylinders. But according to my friend, this is not that unusual for camperized vehicles that are converted to propane.

My buddy has removed the propane system on his new motor and plans on buying a truck with a diesel next time.

 

LPG is not that common here yet, but I think it will be quite soon. Because of the very high taxes on gasoline...... It is not quite as bad as in the UK, but not much better, I pay 8.75 SEK per litre 95 Octane Unleaded, to give you an idea of how much that is, 1 USD is about 10 SEK... 1 GBP is about 14 SEK.

That is why I am interested in the posibility of having an alternative to gasoline.

Most likely I'd use LPG for longer trips, and switch to gasoline when taking it to the track and stuff like that.

 

The most common problem is with backfires through the inlet manifold which can be quite expensive as it can damage MAF sensor, airbox etc.
Guys building custom propane engines have very little valve overlap to help prevent this.

Simon