Propane gas conversion review (long post)

[cobraboy]

One would think there would be a pre-programmed "map" to download to the chip in the ECU, or at minimum a new chip. And aren't most modern ECU systems "closed loop" systems with an O2 sensor that adjusts timing and mixture automatically?

All changing spark plugs would do is change the combustion chamber "heat". If the engine is backfiring, it may have "hot spots" causing it, necessitating a much cooler plug.

Does the propane burn completely? Does the timing have to be changed to prevent detonation?

As far as engine damage, the only things I know of that would cause it would be friction and heat. Does the propane burn hotter? Does it increase engine temperatures? Is that why more oil is consumed?

I would think that a sound engine with good compression/healthy rings would handle a conversion well. Bad rings may allow blow-by, and perhaps early oil contamination, resulting in damage.

I'd be interested in the engineering aspects of the post-conversion product.

 

[AZB]

Oh please, don't hurt yourselves with these issues. The bottom line is this: these systems are working fine in DR and people have been saving a ton of cash on fuel for many years. Why worry about all the high temperatures and compression factors? let the system do its job and go on with your lives. This system is really not all that difficult as we make it out to be. It works, the car engines are not being damaged, the cars run smooth and money saving is really whats it all about.
AZB

 

[Hipocrito Mejia]

We're just discussing the differences with the better systems used abroad. As I said, the Italian system is the best available in DR at this time, but to that it is the optimum solution, or that the car runs as orignal, or that it doesn't cause premature engine damage, is wrong.

We all know the Dominican mentality. If it works, then it's fine. We'll ask questions later.

 

[Robert]

Oh please, don't hurt yourselves with these issues. The bottom line is this: these systems are working fine in DR and people have been saving a ton of cash on fuel for many years. Why worry about all the high temperatures and compression factors? let the system do its job and go on with your lives. This system is really not all that difficult as we make it out to be. It works, the car engines are not being damaged, the cars run smooth and money saving is really whats it all about.
AZB

AZB, get over yourself. The technical aspects are an interesting discussion.
They do lots of things here in the DR, that doesn't mean they do them right.

 

[Chip]

Here's some calculations on the savings"

- mileage 12,000 mi per yr
- fuel efficiency - 25 mpg gas, 20 mpg propane
- gas cost US4.90, propane US1.80
- Cost per year gas 12,000/25*4.90 = US2352
propane 12,000/20*1.80 = US1080

- Savings = 1352. For around US500-1000 an engine can be rebuilt here. The breakeven point is sometime in the first year. This scenario is obviously on the conservative side as far as fuel efficiency for the propane goes, because I find that typically for the same amount of miles travelled, the cost is a third less, which would lead me to believe there is minimal difference between the fuel efficiency of the two fuels. This could be attributed to the fact that with propane I typically drive much slower than with gas, as there is less power.

 

[AZB]

AZB, get over yourself. The technical aspects are an interesting discussion.
They do lots of things here in the DR, that doesn't mean they do them right.

This is my point, we confuse ourselves with the technicality aspect of the issues and then totally lose the original idea. This system is really not at rocket science level. This is a simple system which works fine for cars in general just like the dominican inverters, they also work fine. They have been installing these propane systems for many years here so they must know by now what works and what doesn't. Like I said earlier, this is not alien technology from another planet. This is a simple system and dominicans have perfected its use to their daily needs. If after 5 years my engine fails, I would be more than glad to either rebuild my engine for 500 dollars or get a nice engine for 350 dollars and have it installed for another 150 dollars. case closed. I still come out way ahead than anyone with gasoline engines
AZB

 

[Robert]

One would think there would be a pre-programmed "map" to download to the chip in the ECU, or at minimum a new chip. And aren't most modern ECU systems "closed loop" systems with an O2 sensor that adjusts timing and mixture automatically?

All changing spark plugs would do is change the combustion chamber "heat". If the engine is backfiring, it may have "hot spots" causing it, necessitating a much cooler plug.

Does the propane burn completely? Does the timing have to be changed to prevent detonation?

As far as engine damage, the only things I know of that would cause it would be friction and heat. Does the propane burn hotter? Does it increase engine temperatures? Is that why more oil is consumed?

I would think that a sound engine with good compression/healthy rings would handle a conversion well. Bad rings may allow blow-by, and perhaps early oil contamination, resulting in damage.

I'd be interested in the engineering aspects of the post-conversion product.

The better LPG kits come with sequential injectors and programmable ECU's to get the right gas:air ratio, timing etc.

As far as I can see, the timing is advanced a little due to the higher octane value of propane, plus LPG burns more than normal fuel, hence less carbon deposits.

A good kit, properly installed on a good condition engine will give performance close to gasoline, plus the engine will last longer.

 

[Robert]

This is my point, we confuse ourselves with the technicality aspect of the issues and then totally lose the original idea. This system is really not at rocket science level. This is a simple system which works fine for cars in general just like the dominican inverters, they also work fine. They have been installing these propane systems for many years here so they must know by now what works and what doesn't. Like I said earlier, this is not alien technology from another planet. This is a simple system and dominicans have perfected its use to their daily needs. If after 5 years my engine fails, I would be more than glad to either rebuild my engine for 500 dollars or get a nice engine for 350 dollars and have it installed for another 150 dollars. case closed. I still come out way ahead than anyone with gasoline engines
AZB

We got it AZB, don't keep on. We have moved on, the discussion has evolved. Either contribute intelligently or step back, it's that simple.

 

[Hipocrito Mejia]

The better LPG kits come with sequential injectors and programmable ECU's to get the right gas:air ratio, timing etc.

Exactly! A programable piggyback ECU is used to control fuel and timing only, leaving all other functions to be controlled by the car's original ECU. A proper tuning would involve adjusting the system's ECU from its base map during 4 to 6 dyno passes.

As far as I can see, the timing is advanced a little due to the higher octane value of propane, plus LPG burns more than normal fuel, hence less carbon deposits.

Actually, there should be significant timing advance. Assuming that regular gas in DR is 87 octane, which we all know it's not, (who knows the real number?) and LPG is around 108-112, this would give the tuner the chance to be very aggressive with timing maps for the new ECU.

A good kit, properly installed on a good condition engine will give performance close to gasoline, plus the engine will last longer.

This is where the tradeoffs begin. LPG has a lower energy potential than gas, but its higher efficiency and octane rating allow for the above mentioned aggressive timing maps, thus compensating for the higher energy potential of gas. The lower operating temps prolong engine life; however, the tradeoff is the lack of lubrication as compared to gas, which then has a tendency to shorten engine life. In the end, it may be a wash.

 

[cobraboy]

Any links to the various systems, especially with the piggyback ECU?

When one says 'Italian system" what does that mean?

I'll probably have it done even with the disallowed LPG subsidy. I just want to know exactly what I'm getting into technically.

 

[AZB]

When one says 'Italian system" what does that mean?

Old news, deleted.

 

[Hipocrito Mejia]

Any links to the various systems, especially with the piggyback ECU?

Here you go! This is a top of the line system and there are lots of pics showing professional, clean installs. They are a far reach from "the best" seen in DR.

www.gastech.org.uk

When one says 'Italian system" what does that mean?

This is the commonly used term for the best currently available in DR. It's an abreviated version of a full kit manufactured in Italy.

 

[Robert]

Now that's how to do it, nice link and some very nice installs!

How do the conversions in the DR adjust for LPG temperature and pressure if they do not use any form of ECU?

 

[Hipocrito Mejia]

How do the conversions in the DR adjust for LPG temperature and pressure if they do not use any form of ECU?

They don't! That's why people experience inconsistent idle and performance.

The DR method works, but even in its finest manifestation, it is a crude solution. Putting in new, regapped spark plugs, and making manual fuel pressure adjustments without giving any consideration to timing, fuel octane, varying engine loads, etc., is not any real tuner's idea of properly tuning such a system.

 

[Rocky]

They don't! That's why people experience inconsistent idle and performance.

The DR method works, but even in its finest manifestation, it is a crude solution. Putting in new, regapped spark plugs, and making manual fuel pressure adjustments without giving any consideration to timing, fuel octane, varying engine loads, etc., is not any real tuner's idea of properly tuning such a system.

That might explain the strange sound I hear from the exhaust, as well as the alleged premature death of the engine.

 

[Hipocrito Mejia]

Rocky, the strange sound that you hear is the car being out of tune. You previously mentioned the old days and tuning cars by ear, so you know what I mean.

Now, if I had to take a guess based on my amateur experience tuning modern gasoline engines, I would say that the premature death is due to the lack of lubrication from LPG, as opposed to gasoline, and exposure to engine knock over a prolonged period of time. Keep in mind, that engine knock has to be really severe before it becomes audible to the human ear, which is the tuning instrument of choice for the mechanics doing installation of these kits in DR.

 

[AZB]

So I guess the italian system is a bad idea. I just didn't know it was so bad for the engine. Thanks guys, I better buy a new engine now and carry it in my trunk in case this one burns out. To me it sounds like at any minute now.
I am done with this tread. Might as well erase this post too.
AZB

 

[Rocky]

So I guess the italian system is a bad idea. I just didn't know it was so bad for the engine. Thanks guys, I better buy a new engine now and carry it in my trunk in case this one burns out. To me it sounds like at any minute now.
I am done with this tread. Might as well erase this post too.
AZB

If we didn't care about you and your car, we wouldn't have responded.
It's the never ending search for the truth, and from the truth, we can be forewarned and thus, forearmed.
I wish you well with your experiment.
As long as you come out ahead in the deal and that you spend less on rebuilds, repairs or engine replacements, than the sum of money you save on fuel, then you're laughing.

 

[Hipocrito Mejia]

Nobody is saying that the system you got installed is a bad idea. It is the best of what's currently available in DR, and over a few years of use, it pays for itself and then some, so in the end, it makes economic sense. It's simple math... just look at Chip's post.

However, this thread moved on into the technical aspects of making this conversion and the best kits and methods available elsewhere. Stop taking the discussion to heart and thinking that everyone is attacking your decision to convert. IMO, you made a wise decision, given the pros and cons, so just move on and go enjoy your new found pesos from the fuel savings.

 

[cobraboy]

So where is a piggyback mapable ECU available? And does a chassis dyno in the DR even exist (we used them for the fine tuning of 500+hp big block V-8's we'd stuff into our 2200lb. Cobra reproductions, the genesis of my handle)?