trying to understand Turbo Timing
01-11-2005, 05:52 AM
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trying to understand Turbo Timing
So i am researching turbo timing and am finding lots of threads that don't really give me the overview i am looking for. I want to know why a turbo car is timed the way it is? why is it retarded per pound of boost, how is power gained through timing? What does a good reliable street car's timing look like? I have been told that 17-19 degrees is a pretty safe amount of timing, I assume that is advanced and then as boost is added it is retarded...no? If you have some info for me or know of a good link you could shoot my way that would be great, Thanks.
01-11-2005, 07:36 AM
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Re: trying to understand Turbo Timing (Benjithx)
hear goes....
ok...first you gotta know what preignition is....
preignition is when you ignite the combustion process too soon, and when the cylinder is going up....the combustion process is pushing it down...this is very bad for the motor. Preignition can be caused by a lot of things. One surefire way to cause preignition is to fire your spark early (advance)
Retarding the timing....The only reason we retard timing is for safety. Advancing your ignition will give you more power. The goal of the tuner is to have the combustion process start pushing that piston down as soon as possible as long as its on its way down. If he does it too late, you will lose a lot of power.
Advance too much--preignition
Retard too much--loss in power
a tuner must find a median between the two
ok...first you gotta know what preignition is....
preignition is when you ignite the combustion process too soon, and when the cylinder is going up....the combustion process is pushing it down...this is very bad for the motor. Preignition can be caused by a lot of things. One surefire way to cause preignition is to fire your spark early (advance)
Retarding the timing....The only reason we retard timing is for safety. Advancing your ignition will give you more power. The goal of the tuner is to have the combustion process start pushing that piston down as soon as possible as long as its on its way down. If he does it too late, you will lose a lot of power.
Advance too much--preignition
Retard too much--loss in power
a tuner must find a median between the two
01-11-2005, 07:48 AM
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Re: trying to understand Turbo Timing (DaZman69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 »</TD></TR><TR><TD CLASS="quote">preignition is when you ignite the combustion process too soon, and when the cylinder is going up....the combustion process is pushing it down...this is very bad for the motor. Preignition can be caused by a lot of things. One surefire way to cause preignition is to fire your spark early (advance)
</TD></TR></TABLE>
Pre-ignition is caused by a heat source other than the spark plug. IE a hot spot in the combustion chamber or super-heated air/fuel. It's uncontroled ignition which can lead to detonation.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Advancing your ignition will give you more power. The goal of the tuner is to have the combustion process start pushing that piston down as soon as possible as long as its on its way down. If he does it too late, you will lose a lot of power.
</TD></TR></TABLE>
The goal is to make peak cylinder pressure at about 16-20 degrees after top dead center. This will give the gas expansion the greatest mechanical advantage on the crankshaft. The goal of the tuner is to get the PPP (peak pressure point) as close to this "sweet" spot as possible without detonating.
Read up:
http://www.fs.isy.liu.se/~larer/Projects/main.html
</TD></TR></TABLE>
Pre-ignition is caused by a heat source other than the spark plug. IE a hot spot in the combustion chamber or super-heated air/fuel. It's uncontroled ignition which can lead to detonation.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Advancing your ignition will give you more power. The goal of the tuner is to have the combustion process start pushing that piston down as soon as possible as long as its on its way down. If he does it too late, you will lose a lot of power.
</TD></TR></TABLE>
The goal is to make peak cylinder pressure at about 16-20 degrees after top dead center. This will give the gas expansion the greatest mechanical advantage on the crankshaft. The goal of the tuner is to get the PPP (peak pressure point) as close to this "sweet" spot as possible without detonating.
Read up:
http://www.fs.isy.liu.se/~larer/Projects/main.html
01-11-2005, 07:50 AM
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Re: trying to understand Turbo Timing (DaZman69)
This is the way I have always understood it. Im sure one of the top tuners on the board can either agree or tell me where I am wrong.
If the timing is advanced to much the EGT's will go pretty high. This in turn like DaZman said will cause predet. That is not good. Rember that compresing air creates lots amounts of heat. If you delay/retard the whole process of combustion you are creating a situation with less heat.
Step retarding, I have haerd is the best way to do your timing. Im sure you know what this is, but if not, its when you set your timing at certain values at different amounts of boost. The higher the boost the more is retarded. This is becuase the heat genereated from more compressed air is more than say a standard atmosphere (given both are at the same timing value). Basically for one set timing, a NA car produces less heat at the value, than someone running 2bar of boost at the same value.
All in all you retard the timing to try to stay away from heat which in turn stays away from predet. You can also add fuel to the equation to help cool things down. Fuel is used to start the combustion process and is also used to be a 'coolant' for the process. I think the key is finding a good balance between the timing and the fuel amounts.
Like I said that is how I have come to understand it. Please take it as my thoughts until one of the more exp. tuners have verfied it.
If the timing is advanced to much the EGT's will go pretty high. This in turn like DaZman said will cause predet. That is not good. Rember that compresing air creates lots amounts of heat. If you delay/retard the whole process of combustion you are creating a situation with less heat.
Step retarding, I have haerd is the best way to do your timing. Im sure you know what this is, but if not, its when you set your timing at certain values at different amounts of boost. The higher the boost the more is retarded. This is becuase the heat genereated from more compressed air is more than say a standard atmosphere (given both are at the same timing value). Basically for one set timing, a NA car produces less heat at the value, than someone running 2bar of boost at the same value.
All in all you retard the timing to try to stay away from heat which in turn stays away from predet. You can also add fuel to the equation to help cool things down. Fuel is used to start the combustion process and is also used to be a 'coolant' for the process. I think the key is finding a good balance between the timing and the fuel amounts.
Like I said that is how I have come to understand it. Please take it as my thoughts until one of the more exp. tuners have verfied it.
01-11-2005, 09:05 AM
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Re: trying to understand Turbo Timing (Civicman86)
So take my car for example, b16, hondata, and lets say 2 bar, How should my timing be set initially and how should it change as boost climbs. Also can hondata do step timing on its own or should i install my MSD BTM from that last setup.
And where does the 18-19 degrees of timing that i was told to use come into play is that the total amount of timing retard at full throttle. For instence if my idle timing is at 0 and as boost raises it starts to retard until it is at full boost (18-19degrees)
And where does the 18-19 degrees of timing that i was told to use come into play is that the total amount of timing retard at full throttle. For instence if my idle timing is at 0 and as boost raises it starts to retard until it is at full boost (18-19degrees)
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01-11-2005, 09:41 AM
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Re: trying to understand Turbo Timing (Benjithx)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">read one of my threads on tuning, ive discussed this in detail quite a bit</TD></TR></TABLE>
Bolded for emphasis.
Do a search using his name while checking both "recent" and "archived" threads.
Bolded for emphasis.
Do a search using his name while checking both "recent" and "archived" threads.
01-11-2005, 10:05 AM
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Re: trying to understand Turbo Timing (Benjithx)
Let it be known that it takes TIME to ignite the air/fuel mixture. The spark plug does not ignite exactly at 0 degrees top dead center because that would be very inefficient, which would result in lack of power.
The initial timing or the idle timing is set at 16 degrees before the piston hits top dead center, that way the spark has 16 degrees of crank rotation to ignite the fuel completely. However, as RPM increases, the ignition has to be advanced either mechanically or electronically (ECU). The reason for this is because as the RPM increases, there is less time for the spark to ignite the fuel completely so the spark has to occur earlier.
But remember this, for forced inducted engines and high compression engines, the pressure inside the cylinders is so much greater than in an average car, which means the combustion process is much faster than a low compression engine. There will be a higher chance of pre-ignition (ignition of the air/fuel, NOT by the spark plug, but by mainly 'hot spots'). Pre-ignition will cause detonation, where two flame fronts collide. That is , the flame front from the spark plug collides with the flame front from the 'hot spot'. This causes an extreme spike in cylinder pressure which causes a big mess.
A good analogy is derived from water waves such as when two waves created by Jet Ski's collide, they will smash into each other and create a huge splash in the water.
Because the forced inducted engines combust the air/fuel mixture faster, less advance is needed. The ECU (Hondata, AEM, etc...) will retard the ignition timing according to increase in boost, RPM, Etc…(According to the ignition map done by the tuner) so that the spark occurs later, therefor there will be less heat/less chance of pre-ignition.
The important part is, the way the engine runs all depends on the tuner and how you want the engine to run. You can have the engine tuned conservatively so that it has a low chance of detonation, makes good power, and is reliable or you can have the engine tuned to make maximum power, but have a higher risk of blowing the engine.
The initial timing or the idle timing is set at 16 degrees before the piston hits top dead center, that way the spark has 16 degrees of crank rotation to ignite the fuel completely. However, as RPM increases, the ignition has to be advanced either mechanically or electronically (ECU). The reason for this is because as the RPM increases, there is less time for the spark to ignite the fuel completely so the spark has to occur earlier.
But remember this, for forced inducted engines and high compression engines, the pressure inside the cylinders is so much greater than in an average car, which means the combustion process is much faster than a low compression engine. There will be a higher chance of pre-ignition (ignition of the air/fuel, NOT by the spark plug, but by mainly 'hot spots'). Pre-ignition will cause detonation, where two flame fronts collide. That is , the flame front from the spark plug collides with the flame front from the 'hot spot'. This causes an extreme spike in cylinder pressure which causes a big mess.
A good analogy is derived from water waves such as when two waves created by Jet Ski's collide, they will smash into each other and create a huge splash in the water.
Because the forced inducted engines combust the air/fuel mixture faster, less advance is needed. The ECU (Hondata, AEM, etc...) will retard the ignition timing according to increase in boost, RPM, Etc…(According to the ignition map done by the tuner) so that the spark occurs later, therefor there will be less heat/less chance of pre-ignition.
The important part is, the way the engine runs all depends on the tuner and how you want the engine to run. You can have the engine tuned conservatively so that it has a low chance of detonation, makes good power, and is reliable or you can have the engine tuned to make maximum power, but have a higher risk of blowing the engine.
01-11-2005, 10:27 AM
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Re: trying to understand Turbo Timing (TurboSmart)
Ok so i am a little confused, The engine need to advance it self a little to compensate for RPM and also needs to retard itself for boost to avoid predet. 
01-11-2005, 05:57 PM
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Re: trying to understand Turbo Timing (platinum00)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Benjithx »</TD></TR><TR><TD CLASS="quote">Ok so i am a little confused, The engine need to advance it self a little to compensate for RPM and also needs to retard itself for boost to avoid predet. </TD></TR></TABLE>
Correct. The time it takes for the signal from the ECU to the distributor to the spark plug and the spark to actually happen only takes a few thousands of a second. the thing is in a hundreth of a second the piston can move quite a bit:
ex: at 7000rpm =~ 119 revolutions in only one second!
hence the signal to ignite the spark must be sent sooner at higher RPMS becuase the time for the spark to actually happen the piston will have moved quite a bit.
And yes you also need to retard the timing in boost because of the higher chance for detonation like everyone has stated correctly.
Correct. The time it takes for the signal from the ECU to the distributor to the spark plug and the spark to actually happen only takes a few thousands of a second. the thing is in a hundreth of a second the piston can move quite a bit:
ex: at 7000rpm =~ 119 revolutions in only one second!
hence the signal to ignite the spark must be sent sooner at higher RPMS becuase the time for the spark to actually happen the piston will have moved quite a bit.
And yes you also need to retard the timing in boost because of the higher chance for detonation like everyone has stated correctly.
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