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S10 1988 (TBI) propane conversion

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Old 02-13-2012, 11:47 PM   #1
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S10 1988 (TBI) propane conversion

Hello again!!
This time I'm getting a bit ahead of myself. The next project, or one that I'll tackle pretty soon (I hope) is converting to propane. (Propane/Gasoline).
One strong reason is economy.

Other reasons are :
--cleaner engine,(therefore longer lasting engine) ,
--cleaner emissions (almost zero pollution),
--greater flexibility of fueling/duration of fuel tank, (if you're running a long
trip and run out of LPG, you can continue with Gasoline until you find an
LPG station, etc),
--not to say that LPG lasts longer plus you can have the size tank you decide
--another reason is simpler carburation tune-up, (once tunned, it rarely fails)
--some claim gas octane exceeds that of Gasoline, (therefore more power)
--Constant fuel feed : if you go off-road and hill climbing, the inclination of
the terrain does not affect fuel supply to the injectors nor performance,
(whereas with Gasoline sometimes it does),
and there's several more.

If anyone has knowledge or experience with this, please do share it here. I have a bit of propane experience but not with this type of engine (GM TBI).
Although I have general knowledge of Mechanics, Electricity and some other crafts and feel able to accomplish it, but what better than having peers interact and share information and fresh ideas.

So go ahead and fire away your thoughts and maybe this will enlighten more than one. As they say, two brains think more than one. . .
Greetings,
Old 02-14-2012, 12:45 AM   #2
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Re: S10 1988 (TBI) propane conversion

Although I have not done a TBI I have done a few dozen conversions over the 4 years I worked at a conversion shop. I do not know what the laws are where you are, but here the conversion must be done at a licensed conversion shop by a licensed conversion tech. Also here any conversion now must use a dedicated ECM just for the propane. I was not involved in conversions at the time this requirement came into effect here.

From what I know about conversions going dual fuel as you suggest, you are creating some very significant compromises. For example, propane like a cooler thermostat, much more initial timing advance but the same total advance, much higher higher compression (around 13.0), and a cold intake manifold.

Using the dedicated propane ECM will take care of the timing, but everything else is a compromise. So do you want the best performance and gas mileage out of gasoline, or propane. With a compromise you will get neither. A dedicated propane engine will get about 10% less MPG than it did on gasoline, but it will produce about the same power. A dual fuel conversion running on propane will get about 20% less MPG and make less power.

Combining 2 fuel systems means maintaining 2 fuel systems. If you need to pass emmissions this can be a challenge as well as more cost.

Things are also now much more complicated as far as reliability and maintenance goes.

You are also now carrying more weight. Propane weighs 1 lb per liter. A 100 liter tank, about all that will fit under the truck, will weigh about 160 lbs when full.

On the topic of fitting tanks, all compressed gas fuel tanks must be cylindrical, not the most space efficient. Remember also that you can only fill the tank to a maximum of 80% capacity.

I know it sounds good that if you run out of propane you can just keep going on gasoline, but besides the above mentioned compromises you also need to know that fuel injectors are cooled by the gasoline running through them. While running on propane you are cooking the gas in the injectors, be prepared to service them often. Also if you are running mostly on propane your gasoline is getting stale, read less MPG and power and increased injector service again.

Long post but hopefully I've answered most of the questions you would be asking.
Old 02-14-2012, 02:27 PM   #3
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Re: S10 1988 (TBI) propane conversion

What timing, i had actually be thinking the same thing after working on the gut truck at work. From what I have researched, unless going full propane ill stick to gas, the cost of having multi with no real bennies has lead me away from this.
Old 02-14-2012, 02:39 PM   #4
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Re: S10 1988 (TBI) propane conversion

As a kick ass turbo install this would be fantastic.

Propane = 110 octane
Propane is delivered to the intake at near freezing temp
Propane is self regulating regarding boost

So it's possible to have 10.0 compression and 15 psi boost and still have the engine live!

Oh, and on the plus side propane extends your oil changes immensely as their is no carbon byproducts introduced to your oil.
Old 02-14-2012, 04:30 PM   #5
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Re: S10 1988 (TBI) propane conversion

Quote: Originally Posted by AWD V8
Although I have not done a TBI I have done a few dozen conversions over the 4 years I worked at a conversion shop. I do not know what the laws are where you are, but here the conversion must be done at a licensed conversion shop by a licensed conversion tech. Also here any conversion now must use a dedicated ECM just for the propane. I was not involved in conversions at the time this requirement came into effect here.

From what I know about conversions going dual fuel as you suggest, you are creating some very significant compromises. For example, propane like a cooler thermostat, much more initial timing advance but the same total advance, much higher higher compression (around 13.0), and a cold intake manifold.

Using the dedicated propane ECM will take care of the timing, but everything else is a compromise. So do you want the best performance and gas mileage out of gasoline, or propane. With a compromise you will get neither. A dedicated propane engine will get about 10% less MPG than it did on gasoline, but it will produce about the same power. A dual fuel conversion running on propane will get about 20% less MPG and make less power.

Combining 2 fuel systems means maintaining 2 fuel systems. If you need to pass emmissions this can be a challenge as well as more cost.

Things are also now much more complicated as far as reliability and maintenance goes.

You are also now carrying more weight. Propane weighs 1 lb per liter. A 100 liter tank, about all that will fit under the truck, will weigh about 160 lbs when full.

On the topic of fitting tanks, all compressed gas fuel tanks must be cylindrical, not the most space efficient. Remember also that you can only fill the tank to a maximum of 80% capacity.

I know it sounds good that if you run out of propane you can just keep going on gasoline, but besides the above mentioned compromises you also need to know that fuel injectors are cooled by the gasoline running through them. While running on propane you are cooking the gas in the injectors, be prepared to service them often. Also if you are running mostly on propane your gasoline is getting stale, read less MPG and power and increased injector service again.

Long post but hopefully I've answered most of the questions you would be asking.
Thanks for your comments, sure is useful talking with a guy with experience.
Ok, in regards to legality (emissions) I don't think its an issue here (State of New Mexico). What I don't think you need is an ECM to make it efficient. Of course there's always a state-of -the-art way of doing things but...older carburated cars didn't need it and most Propane vehicles still don't use it, here's why, because LPG is a clean fuel by nature and has clean combustion itself and the few adjustments you can do on the evaporator can fine tune the carburation (or combustion mix). If you measure emissions on a badly carburated Propane engine, I'm sure you won't get even 20% of a what you get with a gasoline operated car, no matter how good this gasoline system is.
So, I know the government is always trying to get more money and keeps inventing ways to charge more on everything and creates more and more regulations but just tell me, what's the case of penalizing those who operate cleaner burning fuels by imposing more fees and requirements? A propane car is already a virtual zero-polluting vehicle and the Gov should give stimulus instead of obstacles. Okay but thats just my rant on the issue.

Now in what refers to timing, I haven't really looked into it, good that you point it out, I don't know what you mean by "initial" timing advance, do you mean at cold start? or "initial" meaning at slow speed (even when hot). If the latter is true, it could be an issue. My idea is that the current MAP will keep on doing the job (timing advance) since I don't see a reason to change it. The MAP works with the manifold pressure and that determines the advance.

What I think could help is changing the performance chip (if that is possible) to a custom programmed chip suitable for LPG. If I can't get it, then its still ok, as far as I can see, the current ECM with current chip should do the job not too bad.

All the other sensors don't have to be a problem but would need to experiment or get some advice (IAC, temp, Oxigen). In regards to the TPS, since there will be no gasoline feed but still as the throttle opens more fuel will feed, (vacuum increases) it should act similar as before. (Am I ok on this?).

Thermostat, can use a colder one, shouldn't affect gasoline performance much anyway.
TBI injectors cooked...
In regards to the injectors (TBI, remember) they are way up there, LPG will not pass through them (they are designed for liquid not gas) and still being dry most of the time is not very good but I don't think that will affect too much. Will have to experiment and see. Now I would love to hear if someone has experimented using the actual TBI injectors to inject LPG, but thats another issue.
Clarifying, I didn't plan to use the actual TBI injectors with LPG but rather use the LPG system as a parallel system in the truck and only using what can be used as common components.

LPG "Injection"
What I'm planning is to inject the LPG directly into the intake Mani or it could be with a carb adapter. . .actually this issue is what mostly I need help with and would like your opinions.

If everything else fails...
If I can't get it to work satisfactorily with Propane and the current ECM system I can look forward to replace the TBI with a mechanical carburator and change the distributor to a vacuum one...yes, go back a bit to the stone age but, keeping in mind that I will keep it in good tunned shape and use it occasionally, but I'm hoping I won't have to go that far...

keep up the good feedback, Thanks
Old 02-14-2012, 04:47 PM   #6
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Re: S10 1988 (TBI) propane conversion

Quote: Originally Posted by Sonomanclature
What timing, i had actually be thinking the same thing after working on the gut truck at work. From what I have researched, unless going full propane ill stick to gas, the cost of having multi with no real bennies has lead me away from this.
The cost of the Propane equipment is, an initial cost but think about all the benefits; cleaner emissions, cheaper price of fuel per gallon, more miles per gallon, cleaner engine, very little residues inside, actually doesn't need heavy maintenance, the evaporator does need service once every so many years but really scarcely, no fuel filter maintenance, even smoother idle, the list goes on.
Now the problem in converting these trucks is the ECM. That is why we're going to deal with it and solve it.
Cheers
Old 02-14-2012, 04:57 PM   #7
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Re: S10 1988 (TBI) propane conversion

Yes you can use an "old school" propane system, it's just that if emission regulations require a computer to control propane mixture you are bound by that. If emissions are not a problem, then go old school, much simpler.

Initial timing refers to the base timing and how quickly the advance comes in. Typically base timing is 0º, with propane you could probably run 15º and recurve your advance to come in quicker and to a total of 36º
If you are going duel fuel you will need an add on computer control to accomplish this.

None of you gasoline sensors would come into play with old school.

Thermostat for propane should be 160º, for gasoline to run in closed loop 190º, so pick one. The 160º in gasoline operation will lower MPG and an increase emissions. The 190º in propane will cause lower MPG, lower performance and shorter valve life.

Even though the injectors are higher up they will still cook the gasoline inside and gum them up. You will find out after several days of propane operation. Repeat this pattern over and over and one day it will not be drivable on gasoline, hope that you haven't just run out of propane at the that time.

Propane in a duel fuel conversion is flowed over and through the OEM TB. You will have a hood that slips over the TB and a hose connected to the propane mixer. The OEM TB will use the throttle plates to control flow into the engine. In a duel fuel conversion the injectors are now a restriction in the intake flow for the propane, see this as reduced power. When in gasoline mode see the propane mixer as a restriction, see this as reduced power.

If you think that swapping a gasoline carb in place of the TBI injection and still going duel fuel, you will now be running the carb dry before you switch to propane, fun to do when in traffic
And when running on propane your carb is now cooking. Gaskets and neoprene parts are drying up and shrinking. One day when you switch back to gasoline the carb will flood the engine because the gaskets have now shrunk and don't seal any more, not to mention the horrific hesitation you often have because the accelerator pump cup has shrunk and can't pump now.

Direct propane injection IS possible if you have the money. It's working very well in diesels. They idle on a very small portion of diesel to set the ignition timing, but can switch between diesel and propane on the fly as propane has a high octane. Not practical yet for gasoline.

Still interested in a duel fuel system?
Old 02-16-2012, 03:08 AM   #8
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Re: S10 1988 (TBI) propane conversion

Quote: Originally Posted by AWD V8
Yes you can use an "old school" propane system, it's just that if emission regulations require a computer to control propane mixture you are bound by that. If emissions are not a problem, then go old school, much simpler.

Initial timing refers to the base timing and how quickly the advance comes in. Typically base timing is 0º, with propane you could probably run 15º and recurve your advance to come in quicker and to a total of 36º
If you are going duel fuel you will need an add on computer control to accomplish this.

None of you gasoline sensors would come into play with old school.

Thermostat for propane should be 160º, for gasoline to run in closed loop 190º, so pick one. The 160º in gasoline operation will lower MPG and an increase emissions. The 190º in propane will cause lower MPG, lower performance and shorter valve life.

Even though the injectors are higher up they will still cook the gasoline inside and gum them up. You will find out after several days of propane operation. Repeat this pattern over and over and one day it will not be drivable on gasoline, hope that you haven't just run out of propane at the that time.

Propane in a duel fuel conversion is flowed over and through the OEM TB. You will have a hood that slips over the TB and a hose connected to the propane mixer. The OEM TB will use the throttle plates to control flow into the engine. In a duel fuel conversion the injectors are now a restriction in the intake flow for the propane, see this as reduced power. When in gasoline mode see the propane mixer as a restriction, see this as reduced power.

If you think that swapping a gasoline carb in place of the TBI injection and still going duel fuel, you will now be running the carb dry before you switch to propane, fun to do when in traffic
And when running on propane your carb is now cooking. Gaskets and neoprene parts are drying up and shrinking. One day when you switch back to gasoline the carb will flood the engine because the gaskets have now shrunk and don't seal any more, not to mention the horrific hesitation you often have because the accelerator pump cup has shrunk and can't pump now.

Direct propane injection IS possible if you have the money. It's working very well in diesels. They idle on a very small portion of diesel to set the ignition timing, but can switch between diesel and propane on the fly as propane has a high octane. Not practical yet for gasoline.

Still interested in a duel fuel system?
Thanks for the insightful comments....yea I thought about going old school ..am not totally convinced its the best avenue though because electronic fuel injection is a bit better when all the controls work well since its computer controlled.
I've heard with OBD II you can replace the Prom for different performances. Don't know if that is possible with OBD I? I know some HHO users just change the Prom chip so it works with hybrid HHO. . but thats another theme. If that was possible I could go that way. . . . do you know something about this? (modifying the Prom chip)

In regards to the injectors gumming up, yes that certainly can happen...if you're not careful.. used to have a classic Mopar ('72 Charger SE (sb)318) years back with Propane + Gasoline and what I did by advice of a friend was to start the engine with gasoline daily then once warm, switch to LPG. This helps to carbonize the valves a bit to avoid excessive erosion on them (i was told) since LPG is a bit tough on the valves on the long run...also easy start on cold days, propane is slow at starting cold, this also keeps the carb gaskets from drying too much... That way, you keep both systems in use and good shape. I never had major trouble with gaskets or such.... Its the philosophy of the end user that matters. Its not about just starting the motor and taking off but to monitor your engine and observe how its performing. Of course ride and enjoy but watching things also.

Now switching from gasoline to LPG was always easy and I could do it on the fly...flip the switch to the center (no connection) and wait till you burn all the gasoline still in the carb ...wait till car stalls a bit (empty carb)..then flip it to "LPG" and bam!..car keeps going ..from LPG to gasoline is a bit more of a ceremony since you have to fill the carburetor first could take some seconds and the 2 fuels should not mix in that direction, just make a momentary stop..

So yes, Im still at it, i still think a 2 fuel system is cool (or 3..add HHO) although of course you can encounter some challenges..
Do you know who sells the throttle plates/adapter for this GM TBI (2.8) ? I haven't seen any. . .
Old 02-16-2012, 12:52 PM   #9
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Re: S10 1988 (TBI) propane conversion

dont know anything bout propane conversion but very nice write ups awd v8!

what about a propane injection similar to a meth injection. not totally running on propane but turning it on when cruising on the hwy or possibly city driving. reduce fuel say to 40% and supplement with a small flow of propane to maximize mpg and minimize the amount of propane carried. im sure a hybrid would still require some crazy tuning but not as much work since your not going from a oily liquid to a gas. also could you say plug the feed into the recirc line or create a custom nozzle into the tbi so you can bypass the injectors?
Old 02-16-2012, 01:42 PM   #10
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Re: S10 1988 (TBI) propane conversion

Any place that sells propane equipment will have the adapter to the throttle plate, and you can buy the throttle plates from them as well.

I've not considered "blending" propane and gasoline, makes no sense if you have a better, cleaner, cheaper fuel to run in a system already installed.
Old 02-16-2012, 07:48 PM   #11
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Re: S10 1988 (TBI) propane conversion

You could always round up one of those electric S10s they made.
Old 02-16-2012, 07:59 PM   #12
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Re: S10 1988 (TBI) propane conversion

Quote: Originally Posted by Blkwdw86
You could always round up one of those electric S10s they made.
And then install a propane powered generator and you will have a propane hybrid, best of both worlds.
Old 02-16-2012, 10:49 PM   #13
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Re: S10 1988 (TBI) propane conversion

I am also interested in propane conversions. They are fairly common here in AZ. But I had in mind something different from what I normally see, about a 5 gallon tank mounted under the rear of the truck/SUV. Back in 1969, my dad had a new F-150 with a propane conversion. Of course it used a carb instead of FI, and he had a huge tank, about the size of an across the bed tool box, mounted in the front of the bed. I don't remember if it also burned gasoline or not. It was fairly common back then to convert farm vehicles from gasoline to butane/propane. I remember him saying he could drive from coast to coast without having to refuel. Propane is very easy to get here, and it shouldn't really cause any problems if it were set up to run on only propane. I wouldn't mind having one of those large tanks if it were low enough to fit under a tonneau cover.
Old 02-17-2012, 07:02 PM   #14
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Re: S10 1988 (TBI) propane conversion

Actually i was thinking about installing the tank underneath the bed...i need to find a slim style tank not too fat..I used to have a dump truck (hobby use mostly in California ) and it had a couple propane tanks under the dump bed, very cool, didn't take cargo space, and by the way, operating the truck w/propane was very economical, and it was a heavy lil monster. ...now in what comes to the s10, don't know if the tank/s would fit ... an option would be a body lift, just 3 inches or so or convert it to flatbed. . .
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