EricD

Hi all!

I can get a good deal on a Thorley header for my 87 4runner with a 22re.

My O2 sensor is currently located on the stock manifold, and the Thorley header that fits my truck is the THY550Y with the O2 sensor located on ONE of the cylinder exits.

Has anyone tried one of these headers? I am curious as to whether I might lose mileage by having the O2 sensor on only one cylinder.

On my searches people say "yeah it probably COULD be a problem, so you should locate it after all the pipes converge, blah blah blah."

But has anyone acctually tried it on only one cylinder? What was the outcome?

Right now I have poor mileage (15mpg) and I'm sure its due to a leak in the manifold causing the O2 sensor to give wrong readings and making it run rich.

I'd hate to get a header to fix that leak problem, but still have poor mileage because of the O2 sensor only grabbing readings from one cylinder...

Am i being paranoid?

Any input?

EricD

I'm wondering as well, that lets say I do move the O2 sensor further away from the engine, would that mess with the computers reading because of the temperature change? Its a single wire O2 sensor, so that means no heater.

kiyobrown

I just put an LCE header on my rig. You HAVE to extend the O2 sensor wire to reinstall your O2 sensor down in the connector pipe. My power has gone up and MPG's are the same. It's just fine if you choose to move it firther downstream. Just make sure when you clean up the wire to extend it, you don't get any shielding wire in with your signal wire.

And there are a bunch of folks that have DT's. If your engine is in good health, it will be fine to have it read off of one cylinder.

abecedarian

Moving the sensor downstream can have some effect on things but only because it takes longer to heat up.
Since your existing sensor is on the manifold, you shouldn't experience any significant issues with it. If you did decide to put a sensor after the collector, I would recommend using a heated sensor just to help with driveability; a universal 3 wire (1 signal, 2 for the heater) should work- you'd just have to wire up the heater.

EricD

Ok, so your saying since its on the manifold right now, if I get the header with the O2 sensor closer to the engine, that I should be ok? With it being on only one cylinder?

abecedarian

Yep. Should be fine. The only difference is the factory manifold puts the O2 sensor in a position that can sample multiple cylinders. If the engine is in a fair and consistant state of tune, even compression, etc., sampling only one cylinder won't have a significant impact.

EricD

Ok, well then I should get a compression test done on my engine before going ahead with this then I'm guessing?

I'm about to do a full tune-up on it myself right away too.