wildrova
15-03-2010, 11:09 PM
First proper automotive post (my ride and an intro doesn’t count), so I thought I’d make it a huge one…
Right then, first things first, the following is a number of Q's from someone who doesn't have a clue about what they're talking about. :) So with that said, it's time to make an idiot of myself.
I'm trying to school myself on engine tuning and how LPG (specifically liquid inject LPG) effects the process and the more i read the more confused I get.
Me thinks that at its very simplest, tuning of an engine optimizes key aspects such as AFR's and ignition timing. That is, fueling levels are matched to the amount of air being drawn into the engine and ignition (spark) is set in relation to TDC. All of this is done while ensuring the engine does not run too lean or too rich. This would explain why a re-tune is recommended when an air intake is changed to a more effective item.
Given the above, so long as enough fuel can be delivered to each cylinder to match the air being drawn in, an effective tune can be reached. This would explain why big forced induction setups require an upgrade of the fueling system because the stock fuel system and injectors can no longer physically deliver the fuel required.
Now, the next part is where i get even more confused:
There seems to be two Liquid Injection LPG systems on the market - JTG Liquid Inject, which a number of people have and are happy with, and Orbital Lpi which seems to have less of a following.
The two systems seem to be similar in their operation with a few key differences.
JTG Liquid Injection
In the case of the JTG system it appears that a LPG injector is tapped into the manifold close to the original petrol injector. The LPG injector is physically matched to the petrol injectors specifications so that the two injectors flow the same amount of fluid over the same period of time and at the same pressure.
Next, some fancy wiring is done, so that when the switch is made from petrol to LPG, the signal from the cars computer is diverted from the petrol injector to the LPG injector. Because the injectors are the same, the cars computer knows no different and still assumes that it is firing a set of petrol injectors.
This means that if the vehicle is tuned for LPG, the tune is conducted in the same way a normal petrol tune would be conducted, however, gains can be made due to the different characteristics of LPG as a fuel. As far as the vehicles sensors and computer know the vehicle is still running petrol.
If the above is true (although very simplified) then I vaguely understand what is going on.
Where I get completely confused is when I look at the Orbital Lpi system…
Orbital Lpi
After a bit of searching I believe that the system Orbital uses might actually be a Vialle Lpi sytem. A bit of further searching located the following document…
http: // www .suzukituning .com / General / VialleLPi / Vialle%20LPi%20Technical%20Manual . htm
After reading parts of the document (and I must admit, most of it went over my head) I think the system works as follows…
1. LPG Injectors are tapped into the manifold near the petrol injectors
Are these injectors physically matched to the petrol injectors in the same or similar way as the JTG system??
2. An intermediate computer controller is installed between the cars ECU and the injectors. This has a number of set parameters that modify the standard petrol injector signal for use with the LPG injectors.
3. As with the JTG system, when the fuel is changed to LPG the cars ECU still believes the engine is running on petrol.
Where I get really really confused to the point of not knowing what is going on is how engine tuning and modifications affect this process.
Is it still the case that as long as the LPG injectors can flow enough liquid at the correct pressure, more performance can be extracted from the engine.
i.e. is the restriction on tuning an engine on Orbital LPG the same as tuning a straight petrol engine - eventually the injectors will not be able to meet the demand of the tune (all other mods being equal)
Is there some other magic occurring inside the LPG controller that restricts the tuning of an engine after the system has been installed.
Can reasonable power still be made with this system for example 370fwkw from an L98 with supporting mods
And finally, given the Orbital system appears to be similar in its setup to sequential vapour injection (an LPG controller that intercepts the vehicles ECU signals) do the answers to my questions apply in to vapour injection systems as well??
Have I got it all wrong and it’s a case of this grasshopper having much to learn??
Regards,
Paul
Right then, first things first, the following is a number of Q's from someone who doesn't have a clue about what they're talking about. :) So with that said, it's time to make an idiot of myself.
I'm trying to school myself on engine tuning and how LPG (specifically liquid inject LPG) effects the process and the more i read the more confused I get.
Me thinks that at its very simplest, tuning of an engine optimizes key aspects such as AFR's and ignition timing. That is, fueling levels are matched to the amount of air being drawn into the engine and ignition (spark) is set in relation to TDC. All of this is done while ensuring the engine does not run too lean or too rich. This would explain why a re-tune is recommended when an air intake is changed to a more effective item.
Given the above, so long as enough fuel can be delivered to each cylinder to match the air being drawn in, an effective tune can be reached. This would explain why big forced induction setups require an upgrade of the fueling system because the stock fuel system and injectors can no longer physically deliver the fuel required.
Now, the next part is where i get even more confused:
There seems to be two Liquid Injection LPG systems on the market - JTG Liquid Inject, which a number of people have and are happy with, and Orbital Lpi which seems to have less of a following.
The two systems seem to be similar in their operation with a few key differences.
JTG Liquid Injection
In the case of the JTG system it appears that a LPG injector is tapped into the manifold close to the original petrol injector. The LPG injector is physically matched to the petrol injectors specifications so that the two injectors flow the same amount of fluid over the same period of time and at the same pressure.
Next, some fancy wiring is done, so that when the switch is made from petrol to LPG, the signal from the cars computer is diverted from the petrol injector to the LPG injector. Because the injectors are the same, the cars computer knows no different and still assumes that it is firing a set of petrol injectors.
This means that if the vehicle is tuned for LPG, the tune is conducted in the same way a normal petrol tune would be conducted, however, gains can be made due to the different characteristics of LPG as a fuel. As far as the vehicles sensors and computer know the vehicle is still running petrol.
If the above is true (although very simplified) then I vaguely understand what is going on.
Where I get completely confused is when I look at the Orbital Lpi system…
Orbital Lpi
After a bit of searching I believe that the system Orbital uses might actually be a Vialle Lpi sytem. A bit of further searching located the following document…
http: // www .suzukituning .com / General / VialleLPi / Vialle%20LPi%20Technical%20Manual . htm
After reading parts of the document (and I must admit, most of it went over my head) I think the system works as follows…
1. LPG Injectors are tapped into the manifold near the petrol injectors
Are these injectors physically matched to the petrol injectors in the same or similar way as the JTG system??
2. An intermediate computer controller is installed between the cars ECU and the injectors. This has a number of set parameters that modify the standard petrol injector signal for use with the LPG injectors.
3. As with the JTG system, when the fuel is changed to LPG the cars ECU still believes the engine is running on petrol.
Where I get really really confused to the point of not knowing what is going on is how engine tuning and modifications affect this process.
Is it still the case that as long as the LPG injectors can flow enough liquid at the correct pressure, more performance can be extracted from the engine.
i.e. is the restriction on tuning an engine on Orbital LPG the same as tuning a straight petrol engine - eventually the injectors will not be able to meet the demand of the tune (all other mods being equal)
Is there some other magic occurring inside the LPG controller that restricts the tuning of an engine after the system has been installed.
Can reasonable power still be made with this system for example 370fwkw from an L98 with supporting mods
And finally, given the Orbital system appears to be similar in its setup to sequential vapour injection (an LPG controller that intercepts the vehicles ECU signals) do the answers to my questions apply in to vapour injection systems as well??
Have I got it all wrong and it’s a case of this grasshopper having much to learn??
Regards,
Paul