Just completed a fresh build 355 with stock tpi in my Formula. Is it necessary to have exhaust for the ECM and the O2 sensor to get along? I am trying to work the bugs out and am just wondering. Does anyone have any experience with this?

I should add that I have shorty open headers at the moment with an O2 sensor in. Right now the car is slow. I am going to get the codes today, but someone I work with tells me I need exhaust and I don't know for sure if that is the case.

the 02 sensor is probably the most important sensor besides the MAF. Without it, the engine doesn't know if its running rich, lean, or right where its supposed to be. That can affect power A LOT.

You should have some sort of exhaust. You don't want outside oxygen to get to the O2 sensor. If it does and the sensor reads it, it'll totally screw up your engine fueling.

You need to slow the exhaust stream down a little so the 02 can work a little more efficiently. An exhaust will do that.

Not only what the above posters have said, but open exhaust like that will feel slow because there is no back pressure and the low end torque goes away some in exchange for high end flow. If you don't have enough flow from the intake/heads, open exhaust is counterproductive in light of a more tuned exhaust for low end power. Basically, if the induction system on the car is set-up for low end power and not for high revs and you have zero back pressure and exhaust essentially set up for high revs top end power, they are working against each other or at least not benefiting each other...

OK, Thanks to all of you. I am going to get some glasspacks put on it this week. This thing is about 2 seconds slow in the 1/4 mi. I think. I am also unsure of my vacuum line routing. I got rid of the smog pump but I still have lines hooked up to the charcoal canister. I don't have a line that goes from the tank vent to the canister though. So I am going to have to look at that stuff again. Do you guys think that that kind of thing could slow it down that bad?

Remember this:
The 02 sensor is out of the loop at wide open throttle (makes no changes based on it's readings)

Once I got it on a scanner I found out that I had a bad ECM. That was sort of a relief because of how slow my car was, I ran 15.21. So I switched out my Memcal is a different ECM and ran last night. Best time 13.91, shifting at 5000. I ran 13.990 shifting at 4200. I have a total stock tpi and open headers so I have some room for improvement.

also 2.02 heads
This cam http://www.summitracing.com/parts/SUM-K1106/
stock rockers.
flat top pistons.
TH350 w/ hughes 2500 stall
29.5" slicks
Moser 12 Bolt 3:73 Eaton

time slip:
60' 2.018
330' 5.787
1/8 8.904 @ 78.39
1000' 11.617
1/4 13.917 @ 98.12

How close do you think I can get to 12's with free and cheap mods? I need to get it some more air, I know. Or maybe I should ask what would be the most cost effective mods to get me close to 12's.

Thanks!

You need atleast 12 inches between the tail pipe ant sensor, and it's a good idea to merge the banks into one and mount the sensor down stream like the OE did.

Your open exhaust is hurting you, exhaust needs to be tuned just like the intake and right now the two are at opposite ends of the spectrum.

I was thinking about putting 3" tubes with glasspacks and bring them out just in front of the rear tires. btw. How importand is it to have a speed sensor? Right now I don't have one in.