Exhaust tuning

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Mar 3, 2009 | 06:59 PM

Whippled 496

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From: Lake Shore, MD

Exhaust tuning

I wanted to get a thread going on whats actually involved in "exhaust tuning". Sounds pretty stupid, but the only thing I can think of is just refining the VE Table due to an increase in air flow. I am going to do a C&P from my other thread for those who didn't want to wade through 8 pages of me and my header delivery, install, and exhaust setup. So here is my last post from that thread......

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Originally Posted by Whippled 496

Got the WBO2 hooked back up and went cruising today. First thing i noticed is the headers made my AFR pretty lean. I had it dialed in to 14.6 with about a 1% swing before the LTs went on. New AFR after headers and before tuning was around 15.4-15.6. It makes sense i suppose now that I have more air flowing through the pipes. I did a few hours of AutoVE'ing and got the AFR back where it should be. BoostVE is still a little rich (10.90 - 11.25) because I pulled that whole table down a few percent not knowing how the headers were going to effect it.

Now here is the really odd part of what i noticed. I lost absolutely no boost at all!! I dont understand it. I am still between 140-144kPa at WOT and if anything....it seems more consistant. I know its breathing better as seen by the lean readings before tuning....but it hasen't effected the manifold pressure at all . This leads me to think there is something else with this setup that has me governed at the 6-7psi level and I dont know what it is. Thats another topic though. As for the truck....running great! Feels great! Can't wait to see if it picked up any time at the track next month.

That basically that sums it up I guess, just wanted to see what others did to tune for exhaust other than the obvious CAT, O2, and EGR deletes. Also wanted to see if anyone had any takes on why my boost didnt drop.

Mar 4, 2009 | 04:42 PM

Whippled 496

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Wow....slow tuning month...LOL.

Mar 4, 2009 | 04:56 PM

charcold-bowtie

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yeah it is. I would think getting the VE back in line is about all. Maybe timing changes on a really drastic change.

Mar 5, 2009 | 08:51 AM

Wilde Racing

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From: Behind the TIG welder

Where is the wb mounted, heat will change the readings some, though Wide bands should be more consistent than 02sensors. I think you are on the right track though, a more steady boost would indicate less revision/contamination due the the long tubes. The fact that it is now lean is interesting, is the air fuel ration only off at idle?

Mar 5, 2009 | 09:11 AM

Whippled 496

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From: Lake Shore, MD

WB is mounted about 8" past the passenger side header collector and about 16" before the CAT. It "WAS" lean before I retuned the VE but i corrected that ....I just assumed it went a little lean due to more air flow with the long tubes vs. the manifolds. Boost seems more consistant now and the top end has a whole different feel than it used to. I just want to be sure the VE table is all thats really tunable with regards to "exhaust tuning".