Long tube headers & TBI

[hmatiak]

Any issues having the o2 sensor down in the collector on a set of long tube/full length headers?

 

[chosen(1)]

yes if you use a stock replacement, no if you use a heated o2 sensor.

With the sensor so far away from the engine it will not get hot enough and the engine will not run at it's peak efficiency.

 

[hmatiak]

More info on the heated o2?

 

[Stomis]

yes if you use a stock replacement, no if you use a heated o2 sensor.

With the sensor so far away from the engine it will not get hot enough and the engine will not run at it's peak efficiency.

I wouldnt say it will NEVER run at efficiency but the motor will DEFINITELY need to be heated up all the way.

Heated O2 is simple. White is IGN hot, Green or purple goes to the original wire, 1 or 2 blacks are grounds. Make sure you dont soldier the green wire it will screw the resistance reading up on the o2 sensor.

 

[eagle mark]

Any issues having the o2 sensor down in the collector on a set of long tube/full length headers?

The standard internet answer is "no. It will not get hot enough."

My real world testing says "no problem"

It will go into open loop more often at idle but other than that nothing! Heated o2 sensors are an advance in emmissions technology and do nothing else other than keep the ECM in closed loop while a car idles in line waiting for an emmissions test at the test station!

 

[RedBrute]

Last fall I converted my son's '79 to TBI. It has hedman elites on it and I installed the O2 sensor in the collector. During single digit temps at idle it will drop out of closed loop while sitting at a red light and the idle quality would change (290HP GM crate engine). Other than that it made no difference while driving. Some day I'll swap in a heated O2, but it causes no problems as it is.

 

[eagle mark]

Last fall I converted my son's '79 to TBI. It has hedman elites on it and I installed the O2 sensor in the collector. During single digit temps at idle it will drop out of closed loop while sitting at a red light and the idle quality would change (290HP GM crate engine). Other than that it made no difference while driving. Some day I'll swap in a heated O2, but it causes no problems as it is.

Beleive it or not it's easier to tune the next bigger cam than the one in the 290HP engine. Why? I have no idea...

I have the same headers with a stock cam and when it goes into open loop at idle like at a light I can not tell the differance. I'm sure the open loop idle could be tuned (chip) to do the same with your 290HP.

 

[dave w]

I say the ECM makes a HUGE difference with a Heated O2. The older 7747 ECM at a slower 160 baud rate ... it's not a big deal if the single wire O2 sensor is in the header collector. Using the newer faster 8192 baud rate ECM, without a heated O2 sensor, in my humble opinion, is not a good plan. The newer 8192 baud rate ECM's have two timing tables and two fuel tables with more range in RPM's and Vacuum measurements than the older 160 baud rate ECM. The difference in speed between the older ECM and newer ECM is like a measurement once a minute (160 baud) and a measurement once a second (8192 baud). So how long does someone wait at a stop light? A heated O2 sensor could pay for itself by saving a few drops of fuel at a stop light? So I wonder ... how many stop lights ... how many drops of fuel per stop light??

dave w

 

[RedBrute]

I worked with TBIchips (Harris Performance now) to get a chip done. Took 5 chips to dial it in and now that warmer wearher is here it doesn't seem to drop out of closed loop. My '87 Blazer has Thorley tri-Y's on it and I may move the O2 bung on that down to the collector. It currently is up at the "Y" for the back 2 cylinders on the drivers side, I think sampling 4 cylinders is better than 2.

 

[RedBrute]

I understand what your saying but realistically fuel economy is not a concern with that engine in that big a truck, just want reliability and cosistency that FI gives vs a carb.