Originally Posted by A56 (Post 356608)

I put them anywhere between 10" - 14" out on the primary tubes, try to find a good average for all eight and stick with that # of inches away from port. If you have a step in that area, put them right after the step, this helps because you just added some area to the primary tube, and if you do it just after a step the area change isnt as critical. Make sure you use a long O2 weldment, so the O2 dosent protrude into the tube excessively. In the collector I put them in the choke if the choke isnt excessively small, or just before the choke as to not change the area but get all the gasses. Though lots of people say not to put them in the collector, I dont agree, if your collector isnt short, they work fine there. I have not tried them on a straight collector, but can only assume you will get outside air at low RPM.

Mark Lelchook
F/SA

Originally Posted by A56 (Post 356620)

Well there you go then, at low RPM the pulses draw back outside air into the collector, especially on a 4 cyl with a 180 degree pulse.

Mark Lelchook
F/SA #764

Originally Posted by Ed Wright (Post 356664)

Problem with putting it in a primary tube is, if you get something in a jetborvinjector you won't see it in your run log. With it in the collectors, you will see a lean indication. You won't know which Cyl, but you will know which bank. If it develops a misfire for any reason you will see a lean indication, but a misfire from ignition, etc) you won't always hear it at high RPM) will cause an erratic reading. A misfire causes lean spikes. Only way I would want one in a primary would be having one in each tube.
I know I don't know everything, but have been tuning EFI cars for 23 years now, and have done it both ways. I much prefer them in the collectors, at least a foot from the end.

Originally Posted by Ed Wright (Post 356670)

Art, is the coolant temp the same? Anytime I have had one pop & bang it has looked lean. If the engine is cooler I would guess it's a tad lean. My stuff always goes down the track quickest richer than the dyno liked. If your problem is at lower temps you might try adding a little fuel in your air/fuel coolant temp correction table, at the temp you are seeing first pass. That's providing you don't warm
It up to the same temp it runs at the rest of the day.