[fullboogie]

Please see my other posts for details on this. The only reason I am making a separate post is for search purposes for the future.

In a nutshell - I installed a catless H-pipe along with 4:10's and a tune to compensate for the gears and to turn off the rear O2's.

I chased down really bad detonation and lean a/f ratios for a while before reinstalling the factory H pipe to narrow down the possible causes. Detonation was gone, and a/f ratios were perfect. Turns out the computer is intolerant of simple mods such as a catless H-pipe, much like a good CAI. I'll work with one of the tuners to get this resolved, but now you guys know. Who knew?

[Bkbulldog]

I know im off topic but i insallted a CAI in my car and the wire that is closest the throttle body that you have to take off the stock instake and put it on the new one it will sometimes slip out why is this?

[texas_mustang]

im about to install my o/r h-pipe.

maybe you didnt have a correct tune for the o/r h pipe. wont just turning off the rear o2 sensors cause you to run to rich?

[fullboogie]

That's my whole point - apparently a catless H pipe needs a revised tune. I'd not seen one thing about this in all the other posts. Perhaps my car is unusual, but it didn't like the H pipe without a tune.

BTW when the rear O2's are turned off it has no effect on the a/f ratio. At WOT the computer ignores the O2's anyway.

[tarpeeler]

my mods are o/r h 3in catback twin 62 throttle body 4.10s and jlt intake and i havent had even the smallest problem yet

[Bhblondguy]

I also have an o/r h-pipe. No problems for me either. It's in the tune.

[texas_mustang]

i thought you had to tune for an o/r pipe

[fullboogie]

Originally Posted by texas_mustang i thought you had to tune for an o/r pipe

Apparently so, after talking with DynoJoe. I had no idea. Live and learn, eh?

[5.0 Junkie]

I put my O/R H on with stock tune. Ran fine. CEL came on due to catalyst efficiency code, but still ran fine. Seth at Brenspeed said no tune needed, just turn off rear o2s. YMMV

[texas_mustang]

i know its kinda off topic, but did yall notice any gains from your o/r h pipe?

[fullboogie]

No gain. Did it strictly for the sound. With the Maggies it's a tad loud, but not obnoxious.

For those of you who didn't need a tune, I'm envious. I guess every car is different...Or maybe '08's are finicky? At least I found the problem...

[her name is ponie]

I ran an off road h and a off road X with no problems maybe you just had some bad luck

[leebunnyz]

same here...i had an o/r h for about a year with no problems...hell i have kook headers on now and dont have a tune and it still runs fine.

[qwik48r]

how did you know it was lean? heard it pingin? I have a or/x on an 08 and have datalogged with NO detonation... actually, when the car was completely stock, I had more detonation... ford calls it normal... pshhhhh.. ass mongers. its even in the user manual

[fullboogie]

Qwik - I have an XD1/LC1 wideband and have configured the analog2 output to run to the Xcalibrator. I then ran all that to my laptop and ran LiveLink to datalog. I datalogged like crazy all weekend, laying the a/f graphs over the rpm, spark, knock sensor and other graphs. All the data showed I was running very lean, and there was audible pinging in every gear. A local tuner told me today that some cars are like this with a catless H pipe, and he's seeing more and more of it on 08's and 09's. Wonder if Ford changed the tune?

[JAY'SRED02]

Glad you was able to figure it out. I am putting my stock h pipe back on this weekend. I hear too many rattles and the wife doesn't like the strong exhaust fumes.