A few tuning questions
TalonEclipseMixGsx
06-29-2007, 12:02 AM
Ok well tonight i was reading about tuning and timing. Before i had just tuned with the wideband keeping the A/F ratios between 10 and 12. Well i decided to go see what my timing would be. This was at 20psi
35mph 5125 rpm 12*timing
68mph 5667 rpm 14*timing
84mph 6421 rpm 13*timing
Now i read that if u fall below 15*timing advance u are getting too much knock. But everything reads fine as far as air/fuel ratios go. Should i really be too worried about this?
Next question i also noticed my fuel trims being way off, which im sure is do to me not having an o2 sensor plugged into the harness. They are supposed to add up to 0 on a 2g, well at WOT they are both 0. But, normal driving stft is at 24 while ltft is at 0. I don't know if this is affecting my timing or not. But a friend told me to keep the wideband connected to the the o2 housing, since thats the most accurate reading. Is it better to connect it to the rear o2 on the exhaust pipe? I know since i took the factory o2 sensor out i get the check engine light, a fuel trim that is way off, and usually about 180-200miles to a tank. So should i move the wideband to the back and put the stock 02 sensor in, or leave it like it is? Does it really throw off the readings that much if it is connected to the rear o2?
Ok, last, i think my mph is off on the speedometer. Its probably because i switched from the stock 17 gsx wheels to the stock 16 gst wheels. The logger and the speedometer are about 4-5mph apart. So, while the logger is sayin im doing 40mph, the speedo is sayin around 45. Is there a way around this, or am i just going to have to live with it?
35mph 5125 rpm 12*timing
68mph 5667 rpm 14*timing
84mph 6421 rpm 13*timing
Now i read that if u fall below 15*timing advance u are getting too much knock. But everything reads fine as far as air/fuel ratios go. Should i really be too worried about this?
Next question i also noticed my fuel trims being way off, which im sure is do to me not having an o2 sensor plugged into the harness. They are supposed to add up to 0 on a 2g, well at WOT they are both 0. But, normal driving stft is at 24 while ltft is at 0. I don't know if this is affecting my timing or not. But a friend told me to keep the wideband connected to the the o2 housing, since thats the most accurate reading. Is it better to connect it to the rear o2 on the exhaust pipe? I know since i took the factory o2 sensor out i get the check engine light, a fuel trim that is way off, and usually about 180-200miles to a tank. So should i move the wideband to the back and put the stock 02 sensor in, or leave it like it is? Does it really throw off the readings that much if it is connected to the rear o2?
Ok, last, i think my mph is off on the speedometer. Its probably because i switched from the stock 17 gsx wheels to the stock 16 gst wheels. The logger and the speedometer are about 4-5mph apart. So, while the logger is sayin im doing 40mph, the speedo is sayin around 45. Is there a way around this, or am i just going to have to live with it?
kjewer1
06-29-2007, 10:34 AM
Ok well tonight i was reading about tuning and timing. Before i had just tuned with the wideband keeping the A/F ratios between 10 and 12. Well i decided to go see what my timing would be. This was at 20psi
35mph 5125 rpm 12*timing
68mph 5667 rpm 14*timing
84mph 6421 rpm 13*timing
Now i read that if u fall below 15*timing advance u are getting too much knock. But everything reads fine as far as air/fuel ratios go. Should i really be too worried about this?
You were doing so well spelling tuning and timing with one "n" and one "m," I got completely blindsided by those damned "U's"... :shakehead All intarweb shortcut grievances aside, let me try to answer your questions.
Between 10 and 12 is a bit vague. Is this all at WOT? If so, 12 is too lean, and 10 is too rich. :) Shoot for a relatively flat 11:1 across the RPM range at WOT, from when the turbo achieves full boost to redline. While the turbo is still spooling, and airflow is lower, you can keep it a little leaner. I like to be under about 12.5:1 with any positive manifold pressure however, gradually dropping to that 11:1 at full boost. Hope that makes some sense.
The comment about dropping below 15 degrees indicating too much knock is not really the case. It's far more dynamic than that, since it all depends on what your timing is actually supposed to be. :) In your case it can be difficult to determine this, since you are using an airflow modifying tuning device (the AFC). We can try to estimate your airflow/rev and make a guess though. Assuming you are around 35 lbs/min (you can verify this on your logger with a 2g) at 20 psi and 6000 rpm, and assuming your AFC correction factor is between -18% (~10:1) and -28% (~11:1) for th 550s, you end up between 1.9 and 2.1 g/rev airflow. This tells me you should be between 16 and 19 degrees at 6k rpm, so you are having between 3 and 6 degrees of timing pulled due to knock, which is certainly worth looking into. ;)
It is also worth mentioning that AFR is only one of many factors involved in knock. I've scattered motors at 10.5:1 AFR on 118 octane race fuel. ;) Timing has a much more profound effect, and there are several others that have some influence. Fuel octane, intake charge temp (intercooling), cam design and cam gear setting, static compression ratio, dirty combustion chamber, sharp corners/hot spots, plugs too hot, excessive piston to head clearance, etc. And things that make the ECU think there is knock when there may not be, like bad knock sensor (look for the tell tale black "goo" leaking out of it), lifters and other mechanical noises, etc.
Next question i also noticed my fuel trims being way off, which im sure is do to me not having an o2 sensor plugged into the harness. They are supposed to add up to 0 on a 2g, well at WOT they are both 0. But, normal driving stft is at 24 while ltft is at 0. I don't know if this is affecting my timing or not. But a friend told me to keep the wideband connected to the the o2 housing, since thats the most accurate reading. Is it better to connect it to the rear o2 on the exhaust pipe? I know since i took the factory o2 sensor out i get the check engine light, a fuel trim that is way off, and usually about 180-200miles to a tank. So should i move the wideband to the back and put the stock 02 sensor in, or leave it like it is? Does it really throw off the readings that much if it is connected to the rear o2?
You are correct in thinking that the bad trims are related to the lack of a front O2 sensor. The front O2 sensor is the only input to fuel trims. ;) I would highly recomend moving the WBO2 to the rear O2 sensor location if you don't run a cat, and putting the stock front sensor back in the O2 housing. If you run a cat, or have an exhaust system with leaks in it that may affect the wideband sensor being placed downstream, go to a muffler shop and have a 5 dollar O2 sensor bung welded into a safe and convenient location in the downpipe. Lastly, if your wideband O2 provides a simulated narrowband output, you are welcome to wire that in and see how it works. They often do not work as well as the stock O2 sensor, but if yours lets you reflash the WBO2 with user selectable stoich point it can be made to work well enough. But you're on your own for that... This post is getting long enough. :)
Ok, last, i think my mph is off on the speedometer. Its probably because i switched from the stock 17 gsx wheels to the stock 16 gst wheels. The logger and the speedometer are about 4-5mph apart. So, while the logger is sayin im doing 40mph, the speedo is sayin around 45. Is there a way around this, or am i just going to have to live with it?
If you find the diameter of both tires you can see how much of the discrepancy is attributed to the tire change. You have about an 11% difference between the two. The tires can't account for all that, usually less than 5. Odds are you just have an inacurate speedometer, which is quite often then case with these cars. Tach too...
35mph 5125 rpm 12*timing
68mph 5667 rpm 14*timing
84mph 6421 rpm 13*timing
Now i read that if u fall below 15*timing advance u are getting too much knock. But everything reads fine as far as air/fuel ratios go. Should i really be too worried about this?
You were doing so well spelling tuning and timing with one "n" and one "m," I got completely blindsided by those damned "U's"... :shakehead All intarweb shortcut grievances aside, let me try to answer your questions.
Between 10 and 12 is a bit vague. Is this all at WOT? If so, 12 is too lean, and 10 is too rich. :) Shoot for a relatively flat 11:1 across the RPM range at WOT, from when the turbo achieves full boost to redline. While the turbo is still spooling, and airflow is lower, you can keep it a little leaner. I like to be under about 12.5:1 with any positive manifold pressure however, gradually dropping to that 11:1 at full boost. Hope that makes some sense.
The comment about dropping below 15 degrees indicating too much knock is not really the case. It's far more dynamic than that, since it all depends on what your timing is actually supposed to be. :) In your case it can be difficult to determine this, since you are using an airflow modifying tuning device (the AFC). We can try to estimate your airflow/rev and make a guess though. Assuming you are around 35 lbs/min (you can verify this on your logger with a 2g) at 20 psi and 6000 rpm, and assuming your AFC correction factor is between -18% (~10:1) and -28% (~11:1) for th 550s, you end up between 1.9 and 2.1 g/rev airflow. This tells me you should be between 16 and 19 degrees at 6k rpm, so you are having between 3 and 6 degrees of timing pulled due to knock, which is certainly worth looking into. ;)
It is also worth mentioning that AFR is only one of many factors involved in knock. I've scattered motors at 10.5:1 AFR on 118 octane race fuel. ;) Timing has a much more profound effect, and there are several others that have some influence. Fuel octane, intake charge temp (intercooling), cam design and cam gear setting, static compression ratio, dirty combustion chamber, sharp corners/hot spots, plugs too hot, excessive piston to head clearance, etc. And things that make the ECU think there is knock when there may not be, like bad knock sensor (look for the tell tale black "goo" leaking out of it), lifters and other mechanical noises, etc.
Next question i also noticed my fuel trims being way off, which im sure is do to me not having an o2 sensor plugged into the harness. They are supposed to add up to 0 on a 2g, well at WOT they are both 0. But, normal driving stft is at 24 while ltft is at 0. I don't know if this is affecting my timing or not. But a friend told me to keep the wideband connected to the the o2 housing, since thats the most accurate reading. Is it better to connect it to the rear o2 on the exhaust pipe? I know since i took the factory o2 sensor out i get the check engine light, a fuel trim that is way off, and usually about 180-200miles to a tank. So should i move the wideband to the back and put the stock 02 sensor in, or leave it like it is? Does it really throw off the readings that much if it is connected to the rear o2?
You are correct in thinking that the bad trims are related to the lack of a front O2 sensor. The front O2 sensor is the only input to fuel trims. ;) I would highly recomend moving the WBO2 to the rear O2 sensor location if you don't run a cat, and putting the stock front sensor back in the O2 housing. If you run a cat, or have an exhaust system with leaks in it that may affect the wideband sensor being placed downstream, go to a muffler shop and have a 5 dollar O2 sensor bung welded into a safe and convenient location in the downpipe. Lastly, if your wideband O2 provides a simulated narrowband output, you are welcome to wire that in and see how it works. They often do not work as well as the stock O2 sensor, but if yours lets you reflash the WBO2 with user selectable stoich point it can be made to work well enough. But you're on your own for that... This post is getting long enough. :)
Ok, last, i think my mph is off on the speedometer. Its probably because i switched from the stock 17 gsx wheels to the stock 16 gst wheels. The logger and the speedometer are about 4-5mph apart. So, while the logger is sayin im doing 40mph, the speedo is sayin around 45. Is there a way around this, or am i just going to have to live with it?
If you find the diameter of both tires you can see how much of the discrepancy is attributed to the tire change. You have about an 11% difference between the two. The tires can't account for all that, usually less than 5. Odds are you just have an inacurate speedometer, which is quite often then case with these cars. Tach too...
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