What makes the S4 engine more powerful then the S3 32V engine?
10-06-2003, 10:50 AM
#31
Pro
Thread Starter
Lagavulin,
Your post made me realize that even though the temperature in the combustion chamber is lower for the forementioned setup than a standard MURPHed 928, there is a lot MORE heated air in the cylinder. I guess that this means that even if the peak temperature is lower, the amount of heat energy transported into the pistons will be higher.
This may mean that, as long as you don't get any detonation, cast pistons is OK for high compression, low boost set-ups, but forged pistons is needed for low compression, high boost applications?
It is tempting to have a go at the 20psi setup with cast pistons, though... IF the pistons can take the extra heat, it may be good to have that extra safety from detonation if the mixture should get lean for a moment. I suspect the piston crowns may take a second or two of lean conditions as long as no detonation occurs?
I am sorry to hassle you all with these questions that I am sure will be evident after some studying! I hope to find the time soon.
Regarding fuel mods, why does so few use an engine management system like Electromotive or Haltech? Is the original system better in any way? It seems strange to spend thousands on supercharging and then risk detonation. I know that tuning of a stand-alone engine management system is a lot of work, but at least it can be done.
Your post made me realize that even though the temperature in the combustion chamber is lower for the forementioned setup than a standard MURPHed 928, there is a lot MORE heated air in the cylinder. I guess that this means that even if the peak temperature is lower, the amount of heat energy transported into the pistons will be higher.
This may mean that, as long as you don't get any detonation, cast pistons is OK for high compression, low boost set-ups, but forged pistons is needed for low compression, high boost applications?
It is tempting to have a go at the 20psi setup with cast pistons, though... IF the pistons can take the extra heat, it may be good to have that extra safety from detonation if the mixture should get lean for a moment. I suspect the piston crowns may take a second or two of lean conditions as long as no detonation occurs?
I am sorry to hassle you all with these questions that I am sure will be evident after some studying! I hope to find the time soon.
Regarding fuel mods, why does so few use an engine management system like Electromotive or Haltech? Is the original system better in any way? It seems strange to spend thousands on supercharging and then risk detonation. I know that tuning of a stand-alone engine management system is a lot of work, but at least it can be done.
10-06-2003, 12:55 PM
#32
Burning Brakes
Join Date: Aug 2001
Posts: 1,117
Likes: 0
Received 0 Likes
on
0 Posts
Ian,
I hope as the supercharging 'trend' begins to come to fruition there will be far more people running stand alone management. Otherwise, 'development' in this area will grind to a halt.
It is really the only way to get really impressive HP/TQ, on this or any other car that was not originally designed to be force inducted.
The stock system can safely adjust for some boost, if you run larger injectors and some more fuel pressure. But you start messing around in the 12 PSI+ boost range, you really need management - sure a forced induction scenario can "work" with the factory L/LH/LH2 system, but it is so far from optimal, sooner or later issues will start to crop up.
Boost requires a completely new set of fuel and ignition curves that are just not practically "doable" with the factory electronics. In order to be accurate you also have to be able to reference boost - which is not an input on the 928's LH brain that I'm aware of (though there may be one, I have yet to see it identified).
Greg
I hope as the supercharging 'trend' begins to come to fruition there will be far more people running stand alone management. Otherwise, 'development' in this area will grind to a halt.
It is really the only way to get really impressive HP/TQ, on this or any other car that was not originally designed to be force inducted.
The stock system can safely adjust for some boost, if you run larger injectors and some more fuel pressure. But you start messing around in the 12 PSI+ boost range, you really need management - sure a forced induction scenario can "work" with the factory L/LH/LH2 system, but it is so far from optimal, sooner or later issues will start to crop up.
Boost requires a completely new set of fuel and ignition curves that are just not practically "doable" with the factory electronics. In order to be accurate you also have to be able to reference boost - which is not an input on the 928's LH brain that I'm aware of (though there may be one, I have yet to see it identified).
Greg
