Pulling timing for Nitrous... Someone explain please
04-26-2002, 07:58 PM
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Re: Pulling timing for Nitrous... Someone explain please Thanks! you may be right. Ill check tommorrow. But i still want the larger Pot and smaller resistor..only to increase the range of temp reading. It seems I gain a bit by advancing the timing NA as well..so for me I want to make it so not only can I retard for nitrous use..but get a little advance for NA use. And Now that you mention it...I am sure your right about the high end of resistance being for the lower temps. So hopefully the 9k ohm pot with the 200 ohm resistor will give me around 0 degrees IAT reading and the 200 ohm maybe 180 degrees IAT.
Thanks! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Thanks! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
04-29-2002, 06:42 PM
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Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ryan23silverado:
<strong>
Anyway, engines are more prone to detonation when the fuel is compressed more. Retarding timing= less compression at the time of ignition= less a chance of knock. But!! (at least this is what i always have thought) less compression= less power. Maybe I just took a long time to get nowhere, but I want to find this question out myself also.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When you retard the timing the piston gets closer to TDC and you have more compression at the time of ignition.
Say you can eliminate detonation with high octane fuel, there is an ideal timing advance for max. power, to much advance, there is to much pressure build up BTDC you lose power, not enough advance, the peek pressure happens to far past TDC and part of the power is lost at the bottom of the power stroke.
When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.
Just some more info. for discussion. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ April 29, 2002, 06:44 PM: Message edited by: WS6underPRESSURE ]</small>
<strong>
Anyway, engines are more prone to detonation when the fuel is compressed more. Retarding timing= less compression at the time of ignition= less a chance of knock. But!! (at least this is what i always have thought) less compression= less power. Maybe I just took a long time to get nowhere, but I want to find this question out myself also.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When you retard the timing the piston gets closer to TDC and you have more compression at the time of ignition.
Say you can eliminate detonation with high octane fuel, there is an ideal timing advance for max. power, to much advance, there is to much pressure build up BTDC you lose power, not enough advance, the peek pressure happens to far past TDC and part of the power is lost at the bottom of the power stroke.
When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.
Just some more info. for discussion. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ April 29, 2002, 06:44 PM: Message edited by: WS6underPRESSURE ]</small>
04-30-2002, 08:57 AM
#23
Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by WS6underPRESSURE:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ryan23silverado:
<strong>
Anyway, engines are more prone to detonation when the fuel is compressed more. Retarding timing= less compression at the time of ignition= less a chance of knock. But!! (at least this is what i always have thought) less compression= less power. Maybe I just took a long time to get nowhere, but I want to find this question out myself also.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When you retard the timing the piston gets closer to TDC and you have more compression at the time of ignition.
Say you can eliminate detonation with high octane fuel, there is an ideal timing advance for max. power, to much advance, there is to much pressure build up BTDC you lose power, not enough advance, the peek pressure happens to far past TDC and part of the power is lost at the bottom of the power stroke.
When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.
Just some more info. for discussion. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Now THAT was exactly what I suspected.... Very cool answer. Thanks!!!
- Matt
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ryan23silverado:
<strong>
Anyway, engines are more prone to detonation when the fuel is compressed more. Retarding timing= less compression at the time of ignition= less a chance of knock. But!! (at least this is what i always have thought) less compression= less power. Maybe I just took a long time to get nowhere, but I want to find this question out myself also.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When you retard the timing the piston gets closer to TDC and you have more compression at the time of ignition.
Say you can eliminate detonation with high octane fuel, there is an ideal timing advance for max. power, to much advance, there is to much pressure build up BTDC you lose power, not enough advance, the peek pressure happens to far past TDC and part of the power is lost at the bottom of the power stroke.
When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.
Just some more info. for discussion. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Now THAT was exactly what I suspected.... Very cool answer. Thanks!!!
- Matt
05-04-2002, 02:08 PM
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Re: Pulling timing for Nitrous... Someone explain please Ok I am gunna be running a 100 maybe a 150 shot on my stock motor, what size resistor should I try to use instead of my IAC to gimmie some retard??
05-04-2002, 02:21 PM
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Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by TBaGZ:
<strong>Ok I am gunna be running a 100 maybe a 150 shot on my stock motor, what size resistor should I try to use instead of my IAC to gimmie some retard??</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well..I just put the new potentiometer in. It is a 10k ohm pot and reads 10k on one end of the scale and 2 ohms at the other. Corresponding IAT readings are now 258 degrees at the 2 ohms and 20 degrees at 10k. When monitoring timing with the scan master I get 24.5 degrees total timing at WOT with the high temp setting (258) and 27.0-27.5 with the lowest temp setting (20). So its about a 3 degree swing from one end to the other. But it will be different on a stock program...mine is Ed Wright custom.
For your setup I might try a 200ohm resistor. I believe that will give you a reading of around 150 degrees F on IAT. Probably retard you about 2 degrees.
<small>[ May 04, 2002, 02:23 PM: Message edited by: 383LQ4SS ]</small>
<strong>Ok I am gunna be running a 100 maybe a 150 shot on my stock motor, what size resistor should I try to use instead of my IAC to gimmie some retard??</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well..I just put the new potentiometer in. It is a 10k ohm pot and reads 10k on one end of the scale and 2 ohms at the other. Corresponding IAT readings are now 258 degrees at the 2 ohms and 20 degrees at 10k. When monitoring timing with the scan master I get 24.5 degrees total timing at WOT with the high temp setting (258) and 27.0-27.5 with the lowest temp setting (20). So its about a 3 degree swing from one end to the other. But it will be different on a stock program...mine is Ed Wright custom.
For your setup I might try a 200ohm resistor. I believe that will give you a reading of around 150 degrees F on IAT. Probably retard you about 2 degrees.
<small>[ May 04, 2002, 02:23 PM: Message edited by: 383LQ4SS ]</small>
05-04-2002, 06:43 PM
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Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by WS6underPRESSURE:
<strong>[QUOTE]When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">BINGO!
Knock or no knock, this is right on the money. As was also stated by someone earlier, less total timing can give you more power on the juice due to the faster burn rate. To optimize HP output you want to peak the cylinder pressure just after TDC. Advancing timing too much combined with the faster burn rate of a nitrous charge can wind up peaking the cylinder pressure before TDC so the pressure winds up cusioning the piston to TDC and actually robbing power.
<strong>[QUOTE]When you add more oxidizer and fuel to the cylinder, the mixture burns faster so you need less timing, keeping the timing the same you'll lose power because you have to much pressure build up BTDC because of the quicker burn.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">BINGO!
Knock or no knock, this is right on the money. As was also stated by someone earlier, less total timing can give you more power on the juice due to the faster burn rate. To optimize HP output you want to peak the cylinder pressure just after TDC. Advancing timing too much combined with the faster burn rate of a nitrous charge can wind up peaking the cylinder pressure before TDC so the pressure winds up cusioning the piston to TDC and actually robbing power.
05-31-2002, 11:50 AM
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Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 383LQ4SS:
Well..I just put the new potentiometer in. It is a 10k ohm pot and reads 10k on one end of the scale and 2 ohms at the other. Corresponding IAT readings are now 258 degrees at the 2 ohms and 20 degrees at 10k. When monitoring timing with the scan master I get 24.5 degrees total timing at WOT with the high temp setting (258) and 27.0-27.5 with the lowest temp setting (20). So its about a 3 degree swing from one end to the other.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Do you have a diagram on how they all wired together?
Thanks <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
-Tuan
Well..I just put the new potentiometer in. It is a 10k ohm pot and reads 10k on one end of the scale and 2 ohms at the other. Corresponding IAT readings are now 258 degrees at the 2 ohms and 20 degrees at 10k. When monitoring timing with the scan master I get 24.5 degrees total timing at WOT with the high temp setting (258) and 27.0-27.5 with the lowest temp setting (20). So its about a 3 degree swing from one end to the other.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Do you have a diagram on how they all wired together?
Thanks <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
-Tuan
05-31-2002, 04:05 PM
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Re: Pulling timing for Nitrous... Someone explain please It doesnt get any simpler. Its the same as disconnecting the IAT plug and sticking a resistor in each plug hole. The only difference is this resistor has a dial and I ran extra wire to mount it in the cockpit. It doesnt even matter which wire goes in which hole.
05-31-2002, 04:39 PM
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Re: Pulling timing for Nitrous... Someone explain please Do you happen to have the part number from Radio Shack? I'm trying to do a search online via RadioShack.com
What is the wattage do we need for the resistor?
Thanks
-Tuan
What is the wattage do we need for the resistor?
Thanks
-Tuan
06-02-2002, 03:32 PM
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Re: Pulling timing for Nitrous... Someone explain please I'm not gunna even open my mouth about the idea of relying on knock retard. If you dont understand why this is bad in a nitrous application then nothing I say is going to convince anyone otherwise.
The reason you retard timing under nos is to delay the combustion event to avoid detonation and reduce load on the shortblock at high cylinder pressures.
Ignoring the nitrous flame rate (which is also an issue, but has already been covered here), as you increase horsepower, the cylinder pressure increases.
This loads the shortblock badly. At TDC, cylinder pressure does not generate any rotational force, it only tries to shove the crank through the bottom of the block. When you retard the timing you delay the combustion event, so you make cylinder pressure at a point where the shortblock can turn this into rotational force rather than stress on the parts.
But more importantly, you can only make so much cylinder pressure before detonation. If you delay the combustion until after TDC then the cylinder pressure drops and therefore detonation is reduced, or you can run more juice before running into detonation.
At first it would seem that this would be a detrement to power, but you have to step back and look at the big picture.
If the total combustion area (the sum of the chamber, piston reliefs, gasket area, and piston/block alignment) is 78 CCs (as in a LS1) and you develop peak cylinder pressure at TDC, it runs pretty good. You can increase the nitrous until it starts to detonate, but that's as far as you can go.
If on the other hand you intentionally retard the timing 10 degrees the piston has moved down .036" before peak cylinder pressure occurs (based on the LS1's 6.1" rod, 3.62" stroke). What this does is increase the combustion area by 7 CCs to 85 CCs. This additional 9% means you can make 9% more cylinder pressure (9% more tq and horsepower) before running into detonation.
/THAT/ is why you retard timing on the bottle.
- Steve
The reason you retard timing under nos is to delay the combustion event to avoid detonation and reduce load on the shortblock at high cylinder pressures.
Ignoring the nitrous flame rate (which is also an issue, but has already been covered here), as you increase horsepower, the cylinder pressure increases.
This loads the shortblock badly. At TDC, cylinder pressure does not generate any rotational force, it only tries to shove the crank through the bottom of the block. When you retard the timing you delay the combustion event, so you make cylinder pressure at a point where the shortblock can turn this into rotational force rather than stress on the parts.
But more importantly, you can only make so much cylinder pressure before detonation. If you delay the combustion until after TDC then the cylinder pressure drops and therefore detonation is reduced, or you can run more juice before running into detonation.
At first it would seem that this would be a detrement to power, but you have to step back and look at the big picture.
If the total combustion area (the sum of the chamber, piston reliefs, gasket area, and piston/block alignment) is 78 CCs (as in a LS1) and you develop peak cylinder pressure at TDC, it runs pretty good. You can increase the nitrous until it starts to detonate, but that's as far as you can go.
If on the other hand you intentionally retard the timing 10 degrees the piston has moved down .036" before peak cylinder pressure occurs (based on the LS1's 6.1" rod, 3.62" stroke). What this does is increase the combustion area by 7 CCs to 85 CCs. This additional 9% means you can make 9% more cylinder pressure (9% more tq and horsepower) before running into detonation.
/THAT/ is why you retard timing on the bottle.
- Steve
06-02-2002, 09:34 PM
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Re: Pulling timing for Nitrous... Someone explain please After putting in a 1K ohm resister my temp went up to 122 degrees. I probably going replace it with a lower resistance resistor to raise it up to 160.
But I did run into one problem though. Now, when I take the resistor out, instead of reading the usual temp, it drop down to -38. That's right negative 38 degree. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
Do you guys have any clues on why is it doing this? Did I short out my IAT sensor? If I need to replace this, do you where I can order one? Any how much does it cost?
Thanks
-Tuan
But I did run into one problem though. Now, when I take the resistor out, instead of reading the usual temp, it drop down to -38. That's right negative 38 degree. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
Do you guys have any clues on why is it doing this? Did I short out my IAT sensor? If I need to replace this, do you where I can order one? Any how much does it cost?
Thanks
-Tuan
06-02-2002, 10:16 PM
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Re: Pulling timing for Nitrous... Someone explain please -38 would be what it reads with the IAT disconnected. Make sure the connections are plugged in right. And any of the potentiometers at Radio Shack should be ok to use since the IAT signal is very low power. Just make sure it says 0-10k ohm
06-03-2002, 08:46 AM
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Re: Pulling timing for Nitrous... Someone explain please </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 383LQ4SS:
<strong>-38 would be what it reads with the IAT disconnected. Make sure the connections are plugged in right. And any of the potentiometers at Radio Shack should be ok to use since the IAT signal is very low power. Just make sure it says 0-10k ohm</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The plug connection is very secure. So I guess the IAT sensor is gone. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
<strong>-38 would be what it reads with the IAT disconnected. Make sure the connections are plugged in right. And any of the potentiometers at Radio Shack should be ok to use since the IAT signal is very low power. Just make sure it says 0-10k ohm</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The plug connection is very secure. So I guess the IAT sensor is gone. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
06-03-2002, 09:09 AM
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Re: Pulling timing for Nitrous... Someone explain please I just found this thread http://forums.corvetteforum.com/zerothread?id=184918 <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
My car is also throwing the same codes, P0113 & P1111. So I'm going to pick up a new IAT at the dealer ($18) and try it out.
-Tuan
My car is also throwing the same codes, P0113 & P1111. So I'm going to pick up a new IAT at the dealer ($18) and try it out.
-Tuan
