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Old 05-19-2012, 09:43 PM   #1
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Default LPG on turbo Miata

Hi all,

First post here, but I've been checking this site for quite a while now
I've recently bought a turbo miata. It's running an FM III kit with MiataLink ECU.

I want to run it on LPG. The price of LPG is nearly 1/3 of the price of fuel, so it's kinda a no-brainer.
The LPG system would be a multipoint injection setup. The problem however, is that all the companies here use some sort of piggyback ECU to control the LPG. Also, the car keeps it's current fuel system, and an extra tank etc is added. The car starts on fuel, and switches to LPG after a mile or so.
The car also switches back to fuel when it reaches a certain rpm, depending on the customers wishes.

Now, this apparently works pretty well, but why have 2 fueltanks, 2 ecu's, lose a lot of trunk space and mess up the balance, if you could run the car on LPG only?

I suppose it would also be better if the LINK could control the gas injectors, so that it has direct access to everything etc, and not the manipulated data from the LPG-ecu. Should be a lot safer too, and you could log/view the tune with the controller/laptop yourself.

Has anyone experience with this? Can the LINK control the gas-install?
Apparently LPG would be interesting for turbo cars, since the octane-number is quite a bit higher, so you could run more boost.

In short: I just want cheap fuel, without ruining the cars weight(distribution) too much

(fyi: fuel costs ~8.5$/gallon, lpg costs ~3$/gallon. I should make the costs for the gas install (~2800$) back in a year or two, and could do a whole lot more fun kilometers without worrying too much about the gas prices )
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Old 05-19-2012, 10:23 PM   #2
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what is lpg?

some sort of natural gas or something?
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Old 05-19-2012, 10:25 PM   #3
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liquid petrol gas, a mix of propane/butane
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Old 05-20-2012, 12:56 AM   #4
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Jasper, this is a very interesting idea.

LPG is not widely available in the US and Canada, which is where the majority of the folks on this forum (myself included) are located, so there's probably not a lot of first-hand knowledge to be found here. In fact, I didn't even realize that LPG "injectors" such as you describe existed. The few vehicles I have seen which were converted to run on what's called "natural gas" here (primarily methane) all used a device which metered fuel mechanically into a common plenum, sort of a cross between the 1970's Bosch K-Jetronic CIS system and a carburetor.

If you plan to keep the dual-fuel system, you might look into the use of a Megasquirt ECU as opposed to the Link. Megasquirt has the ability to switch between two fuel maps and two ignition maps based on a single input, so you might simply use a single electrical signal to switch fuel and ignition maps as well as a bank of relays to toggle between the two sets of injectors, disable the main fuel pump, etc.
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Old 05-20-2012, 03:22 AM   #5
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Quote:
Originally Posted by Terror Factor View Post
fyi: fuel costs ~8.5$/gallon, lpg costs ~3$/gallon. I should make the costs for the gas install (~2800$) back in a year or two, and could do a whole lot more fun kilometers without worrying too much about the gas prices
LPG use has become very popular in Slovakia recently because of the price advantage and availability of inexpensive diy conversion kits. Many delivery businesses / taxis etc are switching so people expect government fuel duty price hikes to make up for lost revenue.

A friend looked into doing this on his mx5 and his conclusion was that he would need to retain a small petrol tank for cold starting as the gas needs to be evaporated though it could be possible to get around this with an electrical heater of some sort. The weight of a typical kit is about 50 kg so not that bad. Typical kits here run less than 1000$ installed, 2800$ must be some Scandinavian prices?
http://allegro.pl/instalacja-lpg-sta...341345416.html
LPG cars run with a distinctive odor and easy to tell when Corvettes, BMW m5s, hummers, escalades etc are running LPG.
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Old 05-20-2012, 03:19 PM   #6
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Quote:
Originally Posted by Joe Perez View Post
Jasper, this is a very interesting idea.

LPG is not widely available in the US and Canada, which is where the majority of the folks on this forum (myself included) are located, so there's probably not a lot of first-hand knowledge to be found here. In fact, I didn't even realize that LPG "injectors" such as you describe existed. The few vehicles I have seen which were converted to run on what's called "natural gas" here (primarily methane) all used a device which metered fuel mechanically into a common plenum, sort of a cross between the 1970's Bosch K-Jetronic CIS system and a carburetor.

If you plan to keep the dual-fuel system, you might look into the use of a Megasquirt ECU as opposed to the Link. Megasquirt has the ability to switch between two fuel maps and two ignition maps based on a single input, so you might simply use a single electrical signal to switch fuel and ignition maps as well as a bank of relays to toggle between the two sets of injectors, disable the main fuel pump, etc.
I might be wrong about the injectors, but as far as I know, they use a second set of injectors.

I've read before that the megasquirt can be used to run 2 maps, but I rather keep the Link, as the costs of converting it to megasquirt would be quite high, although I'm not sure how much I could get back by selling the Link.

Quote:
Originally Posted by sturovo View Post
LPG use has become very popular in Slovakia recently because of the price advantage and availability of inexpensive diy conversion kits. Many delivery businesses / taxis etc are switching so people expect government fuel duty price hikes to make up for lost revenue.

A friend looked into doing this on his mx5 and his conclusion was that he would need to retain a small petrol tank for cold starting as the gas needs to be evaporated though it could be possible to get around this with an electrical heater of some sort. The weight of a typical kit is about 50 kg so not that bad. Typical kits here run less than 1000$ installed, 2800$ must be some Scandinavian prices?
http://allegro.pl/instalacja-lpg-sta...341345416.html
LPG cars run with a distinctive odor and easy to tell when Corvettes, BMW m5s, hummers, escalades etc are running LPG.
I've also read that starting (when cold) is apparently one of the main problems with LPG, but I don't think it's not solvable. An electric heater like you say might be a solution, I'm not sure.

The price that I quoted is for the system and the full install, as in: Leave your car, get it back the next day with a full lpg system. LPG has to be installed by a certified installer here. You used to be able to do it yourself, but it's not allowed anymore. That also included a 'flashlube' system, a system to lubricate your valves.

I am not sure if there are any LPG only vehicles here in Belgium. It's not that popular (most people run on diesel) here, and an lpg installer I contacted some time ago said it might be because of legal problems. Those vehicles get registered as gasoline+lpg, apparently not LPG only.

The best option is apparently an liquid lpg injection system, instead of a vapor injection system. It has quite some benefits: http://www.lpgli.com/features.html

It also seems to solve the cold starting issues, and provides even more cooling. Looks like the perfect turbo-fuel lol

EDIT: link to a site (of an lpg-installer in the uk) that explains all the systems: http://www.lpgc.co.uk/index_files/TypesofLPGsystems.htm

Do want the liquid injection setup, seems to be the right way for my goal. I'll be mailing an installer that installs those systems now for some more information

Last edited by Terror Factor; 05-20-2012 at 04:51 PM.
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Old 05-20-2012, 06:11 PM   #7
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Quote:
Originally Posted by Terror Factor View Post
I might be wrong about the injectors, but as far as I know, they use a second set of injectors.
This could be. The only systems which I have seen in the US were of the hobbyist variety, built by individuals who were clearly not skilled engineers.


The matter of having to start on gasoline puzzles me slightly. Here in the US, propane gas is sometimes used to power medium-sized emergency electrical generators, which is the only are in which I have some first-hand experience. I have worked at two radio stations which used propane-fueled generators in the range of 25 to 50 kilowatts electrical output, and neither of these had any provision for starting on gasoline. They were fueled only by propane, and started up instantly just like a gasoline engine.

Admittedly, these were both in Florida, where temperatures almost never drop below 0C.


Some interesting links above. I need to spend some time digesting them.
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Old 05-20-2012, 06:26 PM   #8
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Well, I've been reading all evening now, I think I can explain!
An LPG system that doesn't use liquid injection, needs some heat to make sure that all the LPG is in gas form before it's injected. When it's cold, that's not the case and I suspect that the system isn't calibrated for that, and has issues to start. That's why they start on petrol (no need to vaporize it first), and switches to gas when the engine is warm enough.

With the liquid injection, the gas is supposed to be in liquid form when it's injected, so it doesn't matter if it's cold (gas stays in liquid form easier), so starting is no issue.

I am seriously hooked on this liquid injection thing lol. It's apparently quite common to even see an increase in power, because the air that enters the engine is a lot colder (gas going from liquid to gasform absorbs heat). The gas acts somewhat like an intercooler.
This, combined with the higher octane rating, is excellent for turbo cars.
And it's definitely interesting if it saves you nearly 2/3's of gas money, like it does here!

AK Miller is a name I've seen somewhere too. An American who apparently specialized in turbocharging and converting to gas afterwards, for performance
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Old 05-24-2012, 08:25 PM   #9
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Finally got a talk with an installer. Apparently they usually start the cars on fuel, even with a liquid injection system. The reason is that the petrol ECU adds more fuel on a cold start, but for lpg that's not necessary/doesn't work very well.
He was going to contact the manufacturer (Vialle) and asks for some more information, since they normally don't remove the petrol equipment.

Normally this shouldn't be an issue with my car, since the LINK can get programmed, and the cold start enrichment should be able to get changed (?)

I forgot to ask him if they can install the LPG injectors where the fuel injectors are now, so they don't need to drill holes in the manifold/the injectors are in the best possible place/I can make some money back by selling the fuel injectors, but I think that shouldn't be a problem, technically at least. I'm not sure how this works legally, since you only seem to see dual fuel, and no lpg only cars :/
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Old 05-24-2012, 11:08 PM   #10
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Quote:
Originally Posted by Terror Factor View Post
I forgot to ask him if they can install the LPG injectors where the fuel injectors are now,
I'm still curious to know whether they configure the system in the same way as a petrol injection system, with one injector per cylinder, pulsed in sync with the crankshaft.

I've just never seen such a system used to deliver LPG / propane.

Quote:
I'm not sure how this works legally, since you only seem to see dual fuel, and no lpg only cars :/
Well, you could always remove the main petrol tank and replace it with a half-litre can.
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Old 05-24-2012, 11:29 PM   #11
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I'm still curious to know whether they configure the system in the same way as a petrol injection system, with one injector per cylinder, pulsed in sync with the crankshaft.

I've just never seen such a system used to deliver LPG / propane.
It does! http://www.suzukituning.com/General/...m#_Toc26108858

Even the 'newer' systems that use vapor injection are sequential systems.
There's a decent explanation on the link I previously posted: http://www.lpgc.co.uk/index_files/TypesofLPGsystems.htm
Quote:
Well, you could always remove the main petrol tank and replace it with a half-litre can.
I think I'll do something like that if they aren't allowed to remove the whole petrol system. A 5l tank or so as a backup, should I run out of fuel, I don't have to get towed lol (since you can't carry lpg around in a plastic container)
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