Open Headers- Need input

[angrysk8r]

Originally Posted by gectek

well lets see, on the first point...look at scan tool data. If you have even seen a vehicle with open manis, when it goes to closed loop and actually looks at the O2 readings, it will see alot of oxygen in the "exhaust" which is really ambient air mixed in with the actual exhaust, then it will think a lean condition, so it will dump more fuel and keep dumping more fuel until the long term fuel trims are mxed out somewhere in the range of +24 ish. then it will choke on its own fuel. The oxygen sensor ONLY senses oxygen, nothing else, that part is common sense. And also if the knock sensor goes off, this will reduce timing, but the fuel will still be there from it staying pig rich and nothing to make a better burn due to the decrease in spark advance...thats what i meant. it doesnt add fuel but takes away spark, but by taking away spark and leaving the massive rich condition, isnt that the same thing

shock24z is pretty experienced with a powrtuner....much more so than most people on these forums

The o2 sensor isn't going to be seeing ambient oxygen...even with open headers there is going to be enough pressure in the exhaust that the ambient air isn't going to get into the exhaust

[gectek]

well personal experience tells me ur wrong...i wouldnt say it if i havent seen it. We are running a stand alone TBI 350 on a stand and it has open manis on it and you can see all sorts of dumb readings. the engine runs fine until closed loop time, then it runs like pooh...

[angrysk8r]

either way...ambient air isn't going to be in the exhaust unless the engine is off

[gectek]

whatever you say

[angrysk8r]

Then answer me, how would this ambient air enter the exhaust? I'm not trying to be a **** but I have a decent amount of experience with these cars and I just don't think there is any way open headers can have such an adverse effect on your engine

[gectek]

well just like there is no perfect air pump, there is no perfect vacuum. there is no perfect air flow into your combustion chamber. do you think when your valve opens that all the air rushes in and nothing comes back out the intake valve...there is time between exhaust pulses, plus the exhaust gasses dont run in a full out straight line race out the pipe, even if it is a straight pipe. turbulence happens, air pressure happens, and just because the exhaust runs all the time the engine is ondoesnt mean that air pressure only happens when those exhuast pressures come out the pipe...even a couple milliseconds is enough time for air pressure to act. how do you think your cyl fills up with air charge when it is running at 6k rpm...or faster

[angrysk8r]

Originally Posted by gectek

well just like there is no perfect air pump, there is no perfect vacuum. there is no perfect air flow into your combustion chamber. do you think when your valve opens that all the air rushes in and nothing comes back out the intake valve...there is time between exhaust pulses, plus the exhaust gasses dont run in a full out straight line race out the pipe, even if it is a straight pipe. turbulence happens, air pressure happens, and just because the exhaust runs all the time the engine is ondoesnt mean that air pressure only happens when those exhuast pressures come out the pipe...even a couple milliseconds is enough time for air pressure to act. how do you think your cyl fills up with air charge when it is running at 6k rpm...or faster

I'll agree with you on the imperfections however I just don't think, at least with grand am headers, that there is going to be enough time in between pulses for air to get all the way up to the o2 sensor

For example, observe the o2 sensor placement on a set of S&S headers:


I just don't see how there would be any way to allow for air to get that far up into the pipes, even at idle, and forget about going part throttle or wot.

[gectek]

well how can air travel all the way through you intake to the valves to the cyl in that same time...pressure differentials happen faster than you can think...it happens whether you want to believe it or not and i have those ss headers, i know where the sensor location is. air travels farther than that in a short time to get to your intake valve...

[angrysk8r]

Originally Posted by gectek

well how can air travel all the way through you intake to the valves to the cyl in that same time...pressure differentials happen faster than you can think...it happens whether you want to believe it or not and i have those ss headers, i know where the sensor location is. air travels farther than that in a short time to get to your intake valve...

thanks for explaining that air can travel fast through the intake, it was a concept i was struggling with

and basically you're saying, that there is going to be enough of a pressure differential in the exhaust, that is already under pressure, to pull ambient air into the o2 sensor? I would love to see scans of this, considering i've run open downpipe with the narrow band just as far down the exhaust as a set of s&s headers with no problem at all, hell my downpipe probably dumps at about the same spot as the s&s headers would if you ran open headers

[Shock24Z]

Originally Posted by gectek

well lets see, on the first point...look at scan tool data. If you have even seen a vehicle with open manis, when it goes to closed loop and actually looks at the O2 readings, it will see alot of oxygen in the "exhaust" which is really ambient air mixed in with the actual exhaust, then it will think a lean condition, so it will dump more fuel and keep dumping more fuel until the long term fuel trims are mxed out somewhere in the range of +24 ish. then it will choke on its own fuel. The oxygen sensor ONLY senses oxygen, nothing else, that part is common sense. And also if the knock sensor goes off, this will reduce timing, but the fuel will still be there from it staying pig rich and nothing to make a better burn due to the decrease in spark advance...thats what i meant. it doesnt add fuel but takes away spark, but by taking away spark and leaving the massive rich condition, isnt that the same thing

Ya I'm pretty aware of the theory of the matter but unless its been tested on a 3400 car and there are scans to prove it why should I just accept your word for it that it will happen? Niether of us know for sure. I do know that I've seen a 3400 with an open downpipe run fine for some time now.

If I had a 3400 to scan with open mani's I would gladly do so and share whatever results I find... but I don't.

Edit: Just had another thought. When you go dyno, if you don't have a spare bung welded in already they'll just clamp a wideband to the end of your exhaust... its literally sitting in the open. This seems like a pretty extreme example of an o2 functioning near ambient air.

Originally Posted by PhantomLover007

I would be greatly worried about exhaust getting into the cabin. Even on short drives, the CO2 can affect you.

Haha, if its a big concern I should be long dead.

[gectek]

Originally Posted by angrysk8r

thanks for explaining that air can travel fast through the intake, it was a concept i was struggling with

and basically you're saying, that there is going to be enough of a pressure differential in the exhaust, that is already under pressure, to pull ambient air into the o2 sensor? I would love to see scans of this, considering i've run open downpipe with the narrow band just as far down the exhaust as a set of s&s headers with no problem at all, hell my downpipe probably dumps at about the same spot as the s&s headers would if you ran open headers

well that isnt the only thing you are struggling with...we can just agree to disagree...ive seen it

[angrysk8r]

I'm not entirely sure what you're getting at, but I'll just assume I just won at the internet

[Shock24Z]

Originally Posted by gectek

ive seen it

On a grand am?

[gectek]

yes on a grand am, an a stand alone engine, on a few v8s running open headers...i was running open manis before i swapped to the headers...and it had that problem....and skater you can assume anything you want, doesnt mean you won...just means that you are having trouble grasping a theory that my grade school cousin can understand...seriously how much pressure do you think is IN an exhaust pipe when they vehicle looks at the O2 sensor...which is NOT at WOT....itll ignore the O2 then also, because it goes back to its predetermined set of WOT instructions. how much pressure is in that exhaust pipe at say 2k rpm...take a wild guess and ull still be wrong. put a pressure gauge in the exhaust sometime and read it with no restriction there is not much pressure...wow big surpise

[Shock24Z]

Insults aren't necessary dude. The guy isn't dumb. He fabbed his own turbo setup that has been running for over a year so he knows something about cars.

[notsoaveragej0e]

methinks Shock and teh Angry one know each other.

[Shock24Z]

Its a possibility. I haven't tried to hide it by any means though.

[angrysk8r]

Originally Posted by gectek

yes on a grand am, an a stand alone engine, on a few v8s running open headers...i was running open manis before i swapped to the headers...and it had that problem....and skater you can assume anything you want, doesnt mean you won...just means that you are having trouble grasping a theory that my grade school cousin can understand...seriously how much pressure do you think is IN an exhaust pipe when they vehicle looks at the O2 sensor...which is NOT at WOT....itll ignore the O2 then also, because it goes back to its predetermined set of WOT instructions. how much pressure is in that exhaust pipe at say 2k rpm...take a wild guess and ull still be wrong. put a pressure gauge in the exhaust sometime and read it with no restriction there is not much pressure...wow big surpise

haha, i guess you didn't catch the sarcasm when i said i was having trouble understanding that simple concept, also I was trying to lighten up the mood by saying i won at the internet, but i suppose you didn't catch that as well

And I didn't ever say how much pressure was in the exhaust, but even if it is just a slight amount of pressure it's enough to keep ambient air out, do you really think there is suddenly going to be enough of an opposite pressure differential to suddenly pull ambient air half way into the exhaust? Doesn't make much sense to me

[Shock24Z]

Originally Posted by angrysk8r

but even if it is just a slight amount of pressure it's enough to keep ambient air out, do you really think there is suddenly going to be enough of an opposite pressure differential to suddenly pull ambient air half way into the exhaust?

I think I know his answer to this one.

[gectek]

yah...[/flame off]...go ahead and run whatever you want OP...dont listen to me
think whatever you want...plus you were the one that got rude first, im feeling more and more like Aaron for some reason, oh well