What effect, if any, does spark/timing have on AF ratio?
11-12-2007, 01:46 PM
#21
Man here is a heated argument, But I totally agree with Wait4me and Redhardsupra, In fact yesterday I was performing a Dyno tune for a Nitrous car, I set the A/F to 12.9 for the NA pull, Then cut back some timing to check on another issue, A/F dropped to 12.5. This is not the first time for this anomaly, I have tuned quite a few cars and playing with the timing DID affect the overall A/F ratio. This is not something that I think might happen or heard that it could or could not, This DID happen EVERY time I tuned so ?????
11-12-2007, 02:09 PM
#22
Man here is a heated argument, But I totally agree with Wait4me and Redhardsupra, In fact yesterday I was performing a Dyno tune for a Nitrous car, I set the A/F to 12.9 for the NA pull, Then cut back some timing to check on another issue, A/F dropped to 12.5. This is not the first time for this anomaly, I have tuned quite a few cars and playing with the timing DID affect the overall A/F ratio. This is not something that I think might happen or heard that it could or could not, This DID happen EVERY time I tuned so ?????
You can have a difference in burn, and end up with different levels of 02 in the pipe, it still does not change the amount of fuel thats being ingested by the engine.
11-12-2007, 06:22 PM
#23
True. The physical amount of fuel and air inducted into the motor are the same regardless of how much combustion has taken place. And the term AIR FUEL RATIO doesn't mean FREE OXYGEN PERCENTAGE. They are totally unrelated.
If we all went down to Ed's shop and plugged in a wideband and a 5 gas machine into the same car you would see that 5 gas machine wouldn't budge much when timing was altered while the WB would show a difference.
This is one thing that is dangerous about tuning. Your tuning is only as good as the measurements you take or what you can deduce through hands on experience. We must all be aware of the limits of certainity.
So now you might think if Free O2 is so inaccurate why use it?
That is because with other gases you can get two answers for any given amount of gas emitted. If you combined a CO and O2 sensor together you might be able to avoid the incomplete combustion issues. At that point why not measure all 5 gasses?
If we all went down to Ed's shop and plugged in a wideband and a 5 gas machine into the same car you would see that 5 gas machine wouldn't budge much when timing was altered while the WB would show a difference.
This is one thing that is dangerous about tuning. Your tuning is only as good as the measurements you take or what you can deduce through hands on experience. We must all be aware of the limits of certainity.
So now you might think if Free O2 is so inaccurate why use it?
That is because with other gases you can get two answers for any given amount of gas emitted. If you combined a CO and O2 sensor together you might be able to avoid the incomplete combustion issues. At that point why not measure all 5 gasses?
11-12-2007, 08:10 PM
#25
True. The physical amount of fuel and air inducted into the motor are the same regardless of how much combustion has taken place. And the term AIR FUEL RATIO doesn't mean FREE OXYGEN PERCENTAGE. They are totally unrelated.
If we all went down to Ed's shop and plugged in a wideband and a 5 gas machine into the same car you would see that 5 gas machine wouldn't budge much when timing was altered while the WB would show a difference.
This is one thing that is dangerous about tuning. Your tuning is only as good as the measurements you take or what you can deduce through hands on experience. We must all be aware of the limits of certainity.
So now you might think if Free O2 is so inaccurate why use it?
That is because with other gases you can get two answers for any given amount of gas emitted. If you combined a CO and O2 sensor together you might be able to avoid the incomplete combustion issues. At that point why not measure all 5 gasses?
If we all went down to Ed's shop and plugged in a wideband and a 5 gas machine into the same car you would see that 5 gas machine wouldn't budge much when timing was altered while the WB would show a difference.
This is one thing that is dangerous about tuning. Your tuning is only as good as the measurements you take or what you can deduce through hands on experience. We must all be aware of the limits of certainity.
So now you might think if Free O2 is so inaccurate why use it?
That is because with other gases you can get two answers for any given amount of gas emitted. If you combined a CO and O2 sensor together you might be able to avoid the incomplete combustion issues. At that point why not measure all 5 gasses?
Example: Today I tuned a Maggie GTO, with forged pistons and slightly lower compression than stock. Without being able to monitor NOX I would have never got it as lean, with as much timing, and felt like I had it safe.
11-13-2007, 12:12 AM
#26
And thats why I do. I was an emissions specialist long before I started tuning. They go hand in hand.
Example: Today I tuned a Maggie GTO, with forged pistons and slightly lower compression than stock. Without being able to monitor NOX I would have never got it as lean, with as much timing, and felt like I had it safe.
Example: Today I tuned a Maggie GTO, with forged pistons and slightly lower compression than stock. Without being able to monitor NOX I would have never got it as lean, with as much timing, and felt like I had it safe.
You are going to take a 30 seconds look at this graph and all your questions will be answered from why lean cruise isn't allowed in the US to why extra oxygen causes you to overfuel.
Not orginally posted by me. Don't give me the credit.
This graph tells to alot. You can tell if you are falsely lean by seeing that you aren't putting out alot of NOX. Or if you add fuel and your CO shoots up then you know you were spot on with AFR but it was something else.
So if any of you guys have 8,000 dollars to get the right equipment and want to be protuners I just gave you the intro. Don't have 8Ks? See Ed
04-12-2008, 09:38 AM
#28
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It may have affected what you were seeing on the WB, but it doesnt mean it caused any more fuel to be run thru the engine with XXX amount of air.
You can have a difference in burn, and end up with different levels of 02 in the pipe, it still does not change the amount of fuel thats being ingested by the engine.
You can have a difference in burn, and end up with different levels of 02 in the pipe, it still does not change the amount of fuel thats being ingested by the engine.
If you advance the timing and get a leaner WB reading then surely it is an accurate reflection of what is going on regarding afr's , given that the burn has been more complete ?
If that is correct adjusting timing does have an affect on the AFR of an engine whilst the fuel ingested remains stable.
cheers
