Should I retard timing?
11-18-2008, 06:54 PM
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Should I retard timing? I have a 2000 camaro ls1 engine patriot STAGE II HEADS/(224/224/581 LIFT CAM 3600 STALL... PROFESSIONALLY TUNED... TIMING SET AT 27 DEGREES
CAN I LEAVE THE TIMING AND RUN A 150 WET KIT? I INSTALLED TR7 PLUGS...
TRYING TO GET THE MAX HP & POWER..... OR SHOULD A RETARD BY 2 DEGREES EVERY 50HP LIKE EVERYONE SAYS..?
CAN I LEAVE THE TIMING AND RUN A 150 WET KIT? I INSTALLED TR7 PLUGS...
TRYING TO GET THE MAX HP & POWER..... OR SHOULD A RETARD BY 2 DEGREES EVERY 50HP LIKE EVERYONE SAYS..?
11-19-2008, 09:50 AM
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If you are trying "TRYING TO GET THE MAX HP & POWER", you will need to retard the timing.
By adding nitrous oxide to an engine, the total amount of oxygen is increased and other gasses that do not support combustion (mostly nitrogen) are decreased. This speeds the burn rate and requires less timing advance for peak output. It is hard for many people to grasp gaining power with less timing, but it’s a fact. Peak cylinder pressure must occur approximately 20 degrees ATDC to make peak power. If you speed the burn rate, peak cylinder pressure will occur to soon. It is easy to run too much ignition advance with nitrous, but too much will not only hurt power, it can quickly bring a nitrous engine into detonation and destroy it.
By adding nitrous oxide to an engine, the total amount of oxygen is increased and other gasses that do not support combustion (mostly nitrogen) are decreased. This speeds the burn rate and requires less timing advance for peak output. It is hard for many people to grasp gaining power with less timing, but it’s a fact. Peak cylinder pressure must occur approximately 20 degrees ATDC to make peak power. If you speed the burn rate, peak cylinder pressure will occur to soon. It is easy to run too much ignition advance with nitrous, but too much will not only hurt power, it can quickly bring a nitrous engine into detonation and destroy it.
11-19-2008, 05:42 PM
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While the site ray quoted above is correct, I really don't think it does a good job explaining what visually is going on. If you are optimally running the correct amount of timing N/A your peak cylinder pressures are going to fall right around 15~20* ATDC. What does this have to do with nitrous right? Well the same is true for nitrous. We need to keep that peak pressure after tdc. Why is this so? Well think of it as a hand pushing down on the piston. If you're applying more pressure to the face of the piston as its traveling up towards TDC, its naturally going to slow and your peak pressure is going to occur too early and there won't be enough of a driving force back down on the piston for the follow through. So the next questions is how can we shift that peak pressure back to where it needs to be? The info from Ray is correct. The firing of the spark plug is going to dictate when the peak pressure is going to occur so if we pull a few degrees out, the peak pressure is going to shift back to its optimal position. 15~20* ATDC. We also need to understand that detonation likes pressure and heat. If you fire the plug too early, you're giving the mixture in the chamber more space and time to grow in nature. This is going to generate higher cylinder pressures versus a spark fired later in the cycle. Higher pressures help lend a hand to detonation which we really need to suppress.
This is a complicated process to understand but once it clicks it becomes a very easy concept. Is it overkill for the average user? Yes, which is why most of the time you're usually ok with timing on the smaller shots.
Ray, please correct me if I am wrong, but I believe this is the site you were quoting in your post: http://www.nitrouskits.co.uk/Technic...is-nitrous.htm There is some more interesting reading over there for those interested. Thanks.
Nick
This is a complicated process to understand but once it clicks it becomes a very easy concept. Is it overkill for the average user? Yes, which is why most of the time you're usually ok with timing on the smaller shots.
Ray, please correct me if I am wrong, but I believe this is the site you were quoting in your post: http://www.nitrouskits.co.uk/Technic...is-nitrous.htm There is some more interesting reading over there for those interested. Thanks.
Nick
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01-01-2009, 04:54 PM
#11
Here's my explanation I use in my lead paragraph in my timing pull write up:
[QUOTE Robert56] Nitrous increases the speed of the flame front, so you're bringing the advance back to properly time the pressure spike to the retreating piston. Meaning, preignition can occur, and lead to detonation with to much timing (stock and/or added advance). What this is saying is, the nitrous causes the cylinder to fire early, like when it's coming up on the compression stroke, this can do big time damage, and is prob the #1 reason the ring lands go. Also, you can see this early firing is less than optimal for ultimate power, and thus, not very volumetric efficient. You want it to fire at the time period when the piston wants to go down for the power stroke, not fighting an up traveling piston (preignition). I hope this makes sense, and if anyone else reading along has additional input or clarification, that would be great.
Here is a great video that shows just how fast nitrous can cause the combustion process to increase. Watch how the paper towel burns at a normal air supplied rate, then once it gets to the N2O it just takes off. Thanks to srsnow from the NitrousForum.com site for the video.
http://s108.photobucket.com/albums/n...t=MOV00443.flv [/QUOTE Robert56]
Robert
Why do we need to Pull Timing?
[QUOTE Robert56] Nitrous increases the speed of the flame front, so you're bringing the advance back to properly time the pressure spike to the retreating piston. Meaning, preignition can occur, and lead to detonation with to much timing (stock and/or added advance). What this is saying is, the nitrous causes the cylinder to fire early, like when it's coming up on the compression stroke, this can do big time damage, and is prob the #1 reason the ring lands go. Also, you can see this early firing is less than optimal for ultimate power, and thus, not very volumetric efficient. You want it to fire at the time period when the piston wants to go down for the power stroke, not fighting an up traveling piston (preignition). I hope this makes sense, and if anyone else reading along has additional input or clarification, that would be great.
Here is a great video that shows just how fast nitrous can cause the combustion process to increase. Watch how the paper towel burns at a normal air supplied rate, then once it gets to the N2O it just takes off. Thanks to srsnow from the NitrousForum.com site for the video.
http://s108.photobucket.com/albums/n...t=MOV00443.flv [/QUOTE Robert56]
Robert
