Nitrous tuning info...
11-28-2010, 05:19 PM
#1
Nitrous tuning info...
Copied and pasted from http://smotherssupercars.com/nitrousclass.html
By Monte Smith
Here's a little to give you an idea of what's going to be talked about....These are some things Monte's talked about on different internet forums that I've just copied and pasted;
I know the NOS suggested jetting is larger on the fuel and that will be dead rich. Will it run? Sure. Will it hurt anything? Likely not at these low HP levels. Are you getting near what you should from the kit? Absolutely not. It has been preached for years that "rich is safe" and most guys tend to believe it, but that could not be farther from the truth. Excess fuel just beats the crap out of the rings. 99% percent of nitrous related engines failures are from too much fuel, too much timing, or both. It is EXTREMELY rare to burn a motor by getting the nitrous system too lean. Barring a mechanical malfunction or an extremely bonehead tune up change, that is nearly impossible to do.
As far as A/F numbers, for some reason, people seem to think nitrous motors need to run way richer than they do in N/A form...again, not true. As an example, if your motor makes best power N/A at around a 13:1 A/F ratio, a moderate nitrous tune (less than 250 hp) will be fine at that same 13:1 A/F ratio, provided you get the timing correct. Although I would not suggest you go straight to these numbers, I run the 632 in the drag radial car, at about 13:5.1 A/F ratio, with about 600hp worth of spray. The Pro-Mod car also runs over 13:1.1 with over 900hp worth of juice. Anything in the 9,10, or 11 range, on spray, is DEAD RICH.
Fuel color on the end of the plug, on the flat face, the last couple threads, or whatever, has nothing to do with the tune up. That is from idling, driving it back, or something similar. The mixture is read at the very base of the porcelain and if you can see a ring of color with your naked eye, you are DEAD RICH. The base of the porcelain should be a clean white and if there is color there, it should take a magnifying plug light to see it and it should be very faint. At this point, you will be somewhat close. Dark specs is usually detonation and the fact that you described your straps as a "grey color" sounds to me like you have too much lead in the motor. If the strap or end of the plug looks like it has been hot, such as this "grey color" you describe, it is generally over timed. If the gaps open after a run or the sharp edges are no longer sharp, you are over timed. Depending on the plug you run, there will be no "heat line" on the strap. If you run NGKs (and you should) and see a "heat line", you are over timed. The proper tune will deliver a plug that is scary clean on the porcelain and a strap that takes on a little of a dusty cinnamon color on the strap....
You did not ask, but one other thing, the weather does NOT change your tune up. Does not matter if it is 30 or 130 outside, it is always cold in that intake. Once you have the mixture right, the only thing you have to change for good or bad air is the timing. And "rich" is not safe. You have to do something horribly stupid to get a motor lean enough to burn it. You will slow the car down before you get it lean enough to burn a piston. An overly rich tune, on the other hand will beat pistons out of the motor in short order. 90% of "burned pistons" are caused by a rich tune.
A public forum is the worst possible place to get advice on nitrous, unless you are fishing for advice on WHO can help you. Everyone has a different idea and tries to convince you to go their way and tell you the other guys don't know what they are talking about. Help at the track is the same way. My advice, find someone you trust and work with that and only that person. You can listen to everybody else, just don't do what they say until you and your selected tuner talk about it. People have different ideas and methods.
Me for example, I don't run anywhere near suggested company jetting in my tune ups and this scares some guys away. But I know those patterns are generally at least 30% rich to cover their backsides. I know this because I test the stuff on a flow bench. I don't use mathematical jet area formulas that don't work, I use real world numbers. I also don't like low pressure tune ups. I don't really care that most people use 5-6lb tune ups, I prefer a higher fuel pressure and change the jetting patterns accordingly. So like I said, pick someone you trust, deal with them and stay off this board on this issue. ...
The only other thing I would say, is based on what you listed above and how you say the plugs look. It sounds like you are running too much spark lead....As far as troubleshooting your system, make sure both coils are working. Past that, take the nitrous solenoid apart and check for trash and make sure the plunger is good and has no nipple on it. A nitrous solenoid only opens .040. A bump on the plunger will easily cut the nitrous flow in half, resulting in a seriously rich tune.
Lots of good info there...Especially for all the guys that think rich is safer than lean...This guy will be coming to Oklahoma to put on a nitrous tuning class that I believe I will be attending.
By Monte Smith
Here's a little to give you an idea of what's going to be talked about....These are some things Monte's talked about on different internet forums that I've just copied and pasted;
I know the NOS suggested jetting is larger on the fuel and that will be dead rich. Will it run? Sure. Will it hurt anything? Likely not at these low HP levels. Are you getting near what you should from the kit? Absolutely not. It has been preached for years that "rich is safe" and most guys tend to believe it, but that could not be farther from the truth. Excess fuel just beats the crap out of the rings. 99% percent of nitrous related engines failures are from too much fuel, too much timing, or both. It is EXTREMELY rare to burn a motor by getting the nitrous system too lean. Barring a mechanical malfunction or an extremely bonehead tune up change, that is nearly impossible to do.
As far as A/F numbers, for some reason, people seem to think nitrous motors need to run way richer than they do in N/A form...again, not true. As an example, if your motor makes best power N/A at around a 13:1 A/F ratio, a moderate nitrous tune (less than 250 hp) will be fine at that same 13:1 A/F ratio, provided you get the timing correct. Although I would not suggest you go straight to these numbers, I run the 632 in the drag radial car, at about 13:5.1 A/F ratio, with about 600hp worth of spray. The Pro-Mod car also runs over 13:1.1 with over 900hp worth of juice. Anything in the 9,10, or 11 range, on spray, is DEAD RICH.
Fuel color on the end of the plug, on the flat face, the last couple threads, or whatever, has nothing to do with the tune up. That is from idling, driving it back, or something similar. The mixture is read at the very base of the porcelain and if you can see a ring of color with your naked eye, you are DEAD RICH. The base of the porcelain should be a clean white and if there is color there, it should take a magnifying plug light to see it and it should be very faint. At this point, you will be somewhat close. Dark specs is usually detonation and the fact that you described your straps as a "grey color" sounds to me like you have too much lead in the motor. If the strap or end of the plug looks like it has been hot, such as this "grey color" you describe, it is generally over timed. If the gaps open after a run or the sharp edges are no longer sharp, you are over timed. Depending on the plug you run, there will be no "heat line" on the strap. If you run NGKs (and you should) and see a "heat line", you are over timed. The proper tune will deliver a plug that is scary clean on the porcelain and a strap that takes on a little of a dusty cinnamon color on the strap....
You did not ask, but one other thing, the weather does NOT change your tune up. Does not matter if it is 30 or 130 outside, it is always cold in that intake. Once you have the mixture right, the only thing you have to change for good or bad air is the timing. And "rich" is not safe. You have to do something horribly stupid to get a motor lean enough to burn it. You will slow the car down before you get it lean enough to burn a piston. An overly rich tune, on the other hand will beat pistons out of the motor in short order. 90% of "burned pistons" are caused by a rich tune.
A public forum is the worst possible place to get advice on nitrous, unless you are fishing for advice on WHO can help you. Everyone has a different idea and tries to convince you to go their way and tell you the other guys don't know what they are talking about. Help at the track is the same way. My advice, find someone you trust and work with that and only that person. You can listen to everybody else, just don't do what they say until you and your selected tuner talk about it. People have different ideas and methods.
Me for example, I don't run anywhere near suggested company jetting in my tune ups and this scares some guys away. But I know those patterns are generally at least 30% rich to cover their backsides. I know this because I test the stuff on a flow bench. I don't use mathematical jet area formulas that don't work, I use real world numbers. I also don't like low pressure tune ups. I don't really care that most people use 5-6lb tune ups, I prefer a higher fuel pressure and change the jetting patterns accordingly. So like I said, pick someone you trust, deal with them and stay off this board on this issue. ...
The only other thing I would say, is based on what you listed above and how you say the plugs look. It sounds like you are running too much spark lead....As far as troubleshooting your system, make sure both coils are working. Past that, take the nitrous solenoid apart and check for trash and make sure the plunger is good and has no nipple on it. A nitrous solenoid only opens .040. A bump on the plunger will easily cut the nitrous flow in half, resulting in a seriously rich tune.
Lots of good info there...Especially for all the guys that think rich is safer than lean...This guy will be coming to Oklahoma to put on a nitrous tuning class that I believe I will be attending.
