I know that is topic has come up multiple times in the past but I have not found a definitive answer.
According to "EEC IV Inner Workings," by tmoss (2002),
"A word of caution to those who install long tube headers. In order for the O2 sensors to operate properly, they must be at, and stay at, a minimum temperature. If you place the HEGO O2 sensors farther away from the head than the stock location, you may have the sensor too far away to keep it hot enough to read correctly due to the cooled exhaust gases. This causes the EEC to enrich mixture and may cause plug fowling. Ceramic heat coating the headers will help maintain exhaust gas temperature. The EEC has a timing table used to time the sampling of the O2 sensors to coincide with the arrival of the latest cylinder exhaust pulse from each bank. Moving the HEGO sensor further away (or closer for that matter) may result in an ill-timed sample, which could also cause improper air/fuel mixtures to occur due to the O2 sensor not sampling when the pulse passes the sensor. One way to compensate for the additional time needed due to adding length in the Long tube headers is to change the timing table with an EEC-Tunerâ or TwEECerâ."
Considering this information, does anyone know if placing O2 sensors as far upstream as possible in the collector so as to sample all four cylinders in a long tube header provides sufficient minimum temperature and remain within the distance for the sample timing?
If so, great; my question is answered.
If not, what is the solution to this issue other than scrapping the long tube headers and reverting back to shortys?
The thought crossed my mind to run 4 O2 sensors 9-12" from the last cylinder, but that sounds like overkill.
What would be involved in tuning the computer to compensate for the additional time for the sample on the long tube? This tuning would be pointless if my temperature is still an issue at that distance.
Thanks,
Mike
According to "EEC IV Inner Workings," by tmoss (2002),
"A word of caution to those who install long tube headers. In order for the O2 sensors to operate properly, they must be at, and stay at, a minimum temperature. If you place the HEGO O2 sensors farther away from the head than the stock location, you may have the sensor too far away to keep it hot enough to read correctly due to the cooled exhaust gases. This causes the EEC to enrich mixture and may cause plug fowling. Ceramic heat coating the headers will help maintain exhaust gas temperature. The EEC has a timing table used to time the sampling of the O2 sensors to coincide with the arrival of the latest cylinder exhaust pulse from each bank. Moving the HEGO sensor further away (or closer for that matter) may result in an ill-timed sample, which could also cause improper air/fuel mixtures to occur due to the O2 sensor not sampling when the pulse passes the sensor. One way to compensate for the additional time needed due to adding length in the Long tube headers is to change the timing table with an EEC-Tunerâ or TwEECerâ."
Considering this information, does anyone know if placing O2 sensors as far upstream as possible in the collector so as to sample all four cylinders in a long tube header provides sufficient minimum temperature and remain within the distance for the sample timing?
If so, great; my question is answered.
If not, what is the solution to this issue other than scrapping the long tube headers and reverting back to shortys?
The thought crossed my mind to run 4 O2 sensors 9-12" from the last cylinder, but that sounds like overkill.
What would be involved in tuning the computer to compensate for the additional time for the sample on the long tube? This tuning would be pointless if my temperature is still an issue at that distance.
Thanks,
Mike
