Open Headers- Need input - Page 4

Shock24Z · 08-05-2008, 01:03 PM

If we put an o2 bung near a downpipe exit (note: turbo car) and scanned for differences to see its effects on the o2, would you accept this as a valid test for/against the open header theory?

It won't take long to drill a hole and weld in a 1$ bung and scan.

gectek · 08-05-2008, 03:47 PM

no need, do it if you want, but there isnt any need to go through the extra trouble to satisfy an arguement on a forum, but on a turbo car it is a little diff i will give you that. my car isnt TC its NA, so diff principles apply accordingly

angrysk8r · 08-05-2008, 06:10 PM

we do have a scan of me running open downpipe, and like i said the o2 sensor placement is approximately where it would be on a set of headers and it dumps about where a set of headers would, shouldn't be too different than a NA car at part throttle and idle

http://scandepot.net/viewscan.php?pk=5184

Shock24Z · 08-05-2008, 06:20 PM

Let it rest for now... I'll scan an N/A 3400 open manifolds if the opportunity arises.

angrysk8r · 08-05-2008, 06:49 PM

Quote:

Originally Posted by Shock24Z

Let it rest for now... I'll scan an N/A 3400 open manifolds if the opportunity arises.

hmm i wonder if brad would let us borrow his car for a half hour

Shock24Z · 08-05-2008, 06:51 PM

Just wait until he asks you to replace the LIM gasket...

99Alero_Boy · 08-05-2008, 08:21 PM

Quote:

Originally Posted by 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

AaronGTR · 08-05-2008, 10:11 PM

Quote:

Originally Posted by 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

If you are running open headers at idle (meaning very slow exhaust gas speeds) and the O2 sensor is very close to the outlet (like it is on TOGs) there will be a certain amount of reversion and mixing going on at the outlet causing the O2 sensor to read some oxygen rich air and screw up the fueling. You won't have enough exhaust gas coming out fast enough to keep the reading consistent unless you are in high rpm all the time. Basically you'd need a dump tube extended behind the headers to keep air from contaminating the exhaust stream around the O2 sensor.

Now, with the O2 sensor placement on S&S headers, yeah it probably wouldn't be a problem. Of course, I've never agreed with where they put the O2 sensor either and think it should be at the bottom like TOG's so that it reads all cylinders just like the factory setup. So if you're smart and have the O2 sensor in the right place, then running open headers at less than WOT would be a problem.

angrysk8r · 08-05-2008, 10:52 PM

hmm point taken, we'll have to do that little experiment though just to see what happens

lone_wolf025 · 08-05-2008, 11:15 PM

Don't forget that during the cycle there are moments when BOTH valves are open, albeit for a short amount of time. So if a little exhaust happens to get drawn into the cylinder in that moment, the pressure difference could allow for some ambient air to get inside at low RPM.

Come to think of it, all this talk of greater airflow messing with the o2 sensor might help explain why under certain conditions the PCM flags a code saying the o2 sensor is reading pig rich...Headers and dp/hi-flo combo would probably do it...

angrysk8r · 08-06-2008, 01:48 AM

Quote:

Originally Posted by lone_wolf025

Don't forget that during the cycle there are moments when BOTH valves are open, albeit for a short amount of time. So if a little exhaust happens to get drawn into the cylinder in that moment, the pressure difference could allow for some ambient air to get inside at low RPM.

Come to think of it, all this talk of greater airflow messing with the o2 sensor might help explain why under certain conditions the PCM flags a code saying the o2 sensor is reading pig rich...Headers and dp/hi-flo combo would probably do it...

no, overlap is normal and won't draw air very far into the exhaust, not to say some could make it a little bit

and if there was extra air in the exhaust it would read lean...

gectek · 08-06-2008, 08:17 AM

it does read lean...it always switches from rich/lean

Badblack04GT · 08-11-2008, 08:10 PM

I lost 10 HP on the dyno running open cutouts VS closed... that's on a cammed 3500 with longtubes. Of course it wouldn't be all that bad if you kept the stock system in place to drive around on and opened the cutout at the track

Louder isn't always better...

Shock24Z · 08-12-2008, 12:20 AM

Can't argue with that.

08-05-2008, 03:47 PM	#62
gectek I hate nose hair AKA: John Join Date: Oct 2006 Location: Lubbock, TX Posts: 2,051 Vehicle: 2002 Grand Am GT sc/t	no need, do it if you want, but there isnt any need to go through the extra trouble to satisfy an arguement on a forum, but on a turbo car it is a little diff i will give you that. my car isnt TC its NA, so diff principles apply accordingly __________________ If you unscrew ur belly button, will ur butt fall off? Procrastinators UNITE!!!.....tomorrow

08-06-2008, 08:17 AM	#72
gectek I hate nose hair AKA: John Join Date: Oct 2006 Location: Lubbock, TX Posts: 2,051 Vehicle: 2002 Grand Am GT sc/t	it does read lean...it always switches from rich/lean __________________ If you unscrew ur belly button, will ur butt fall off? Procrastinators UNITE!!!.....tomorrow

08-11-2008, 08:10 PM	#73
Badblack04GT Superdave AKA: Dave Join Date: May 2004 Location: Quad cities, Iowa Posts: 88 Vehicle: 1989 Camaro RS	I lost 10 HP on the dyno running open cutouts VS closed... that's on a cammed 3500 with longtubes. Of course it wouldn't be all that bad if you kept the stock system in place to drive around on and opened the cutout at the track Louder isn't always better... __________________ 2003 Avalanche Z71 2006 Trailblazer 1989 Camaro RS- Cammed 3500 LX9 swap, P&P'd top end, Longtube headers, ITB's, built 700R4/3500 stall, 3.73 posi, etc.. -- WOT-Tech FTW!

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08-05-2008, 01:03 PM	#61
Shock24Z GAGT - Member AKA: Andy Join Date: Aug 2005 Location: Lincoln, NE Age: 32 Posts: 371 Vehicle: 98 Grand Prix GTP	If we put an o2 bung near a downpipe exit (note: turbo car) and scanned for differences to see its effects on the o2, would you accept this as a valid test for/against the open header theory? It won't take long to drill a hole and weld in a 1$ bung and scan.

08-05-2008, 06:10 PM	#63
angrysk8r GAGT - Member AKA: Luke Join Date: Sep 2005 Location: Lincoln NE Posts: 331 Vehicle: 1999 Grand Am SE	we do have a scan of me running open downpipe, and like i said the o2 sensor placement is approximately where it would be on a set of headers and it dumps about where a set of headers would, shouldn't be too different than a NA car at part throttle and idle http://scandepot.net/viewscan.php?pk=5184

08-05-2008, 06:20 PM	#64
Shock24Z GAGT - Member AKA: Andy Join Date: Aug 2005 Location: Lincoln, NE Age: 32 Posts: 371 Vehicle: 98 Grand Prix GTP	Let it rest for now... I'll scan an N/A 3400 open manifolds if the opportunity arises.

08-05-2008, 06:51 PM	#66
Shock24Z GAGT - Member AKA: Andy Join Date: Aug 2005 Location: Lincoln, NE Age: 32 Posts: 371 Vehicle: 98 Grand Prix GTP	Just wait until he asks you to replace the LIM gasket...

08-05-2008, 10:52 PM	#69
angrysk8r GAGT - Member AKA: Luke Join Date: Sep 2005 Location: Lincoln NE Posts: 331 Vehicle: 1999 Grand Am SE	hmm point taken, we'll have to do that little experiment though just to see what happens

08-12-2008, 12:20 AM	#74
Shock24Z GAGT - Member AKA: Andy Join Date: Aug 2005 Location: Lincoln, NE Age: 32 Posts: 371 Vehicle: 98 Grand Prix GTP	Can't argue with that.