Step-son's big prix

[GRR8APE]

My step-son has an '07 Gran Prix with a cute little 5.3L. The motor is just turned the wrong way! Seriously... He has a electric cutout in place of the cat. This means no O2 sensor. He thinks this will not effect anything except for the dummy light on the dash. Is he correct? I think having no O2 sensor at all would cause some fuel trim issues. Please help us o'wise one.

[GRRRR8]

It will effect catalyst efficiency and set a code unless he has turned off the rear O2. It wont effect the front O2s.

[GRR8APE]

So just a re-tune to delete rear O2? By-the-way the cutout is in place of the cat, so no cat at all. He is trying desperately to catch me.

[usf3983]

He is trying desperately to catch me.


im not an expert, but that seems futile. could get expensive.

[dispatchg8gt]

If the cutout is before the first O2 it will screw with his trims at WOT. Engine goes open loop at WOT and bases fueling off what the first O2 sensor reads. If the car ain't seeing flow past the first O2 bad shit could happen.

DISCLAIMER: This is based off my knowledge of the 3800 series III in my 04 GP Comp G.

[GRRRR8]

If the cutout replaces the cat, just get it tuned to turn off the rear O2(s)

['02 ws6]

Or buy some 02 simulators.

[JP GXP]

The car is mine. And so all I have to do is tuned out the rear 02 and that's it?

[Darkside]

Not sure you'll gain a whole lot from it. Any other exhaust upgrades? Might get a little stinky as well.

[done12many2]

The car is mine. And so all I have to do is tuned out the rear 02 and that's it?

Have the rear O2 sensors disabled in the tune and retune for the cutout. It should sound terrible! Good luck with the project.

[JP GXP]

Have the rear O2 sensors disabled in the tune and retune for the cutout. It should sound terrible! Good luck with the project.

I think it sounds good, you decide Closed and Opened (http://www.youtube.com/watch?v=jIs1PbZBoX4) Closed Drive By (http://www.youtube.com/watch?v=_hVdFbLT_Po) and Open Drive By (http://www.youtube.com/watch?v=eU-lMCMQAmM). Thanks for the good luck wishes.

It made a decent difference in times and doesn't stink at all.

[Darkside]

DH numbers - 0-60: 4.8 sec 1/4: 13.4@108 2.6 60'

This is why I don't like DashHawk or any other numbers besides an actual dragstrip. Every tenth you lower in the sixty foot is good for two tenths in the quarter mile. So the dash hawk is saying that if you got a 2.0 sixty, you would be at a 12.2. What are modded Gxp's running these days?

[JP GXP]

I always thought it was a tenth to tenth ratio, maybe a little lower? How'd you get the tenth to two tenths ratio? 12.8 @ 108 with 2.0 60' makes sense. The couple of modded GXPs I know of are in the low 13s, most are stock running high-midhigh 13s. I plan on getting some real numbers next month, hopefully.

[GRRRR8]

.10 in the 60fter = approx .15 on the big end.

[JP GXP]

.10 in the 60fter = approx .15 on the big end.

Was not aware, thanks for the info, I know DHs are off. I'm just hoping for low 13s, 12s would be nice, but I'm sure I need a little more done for that, thanks for the help guys.

[superspud]

Was not aware, thanks for the info, I know DHs are off. I'm just hoping for low 13s, 12s would be nice, but I'm sure I need a little more done for that, thanks for the help guys.

my DH numbers for my completely stock G8 are:

o-60: 4.7s

1/4 mile: 13.2 @108.74

if that gives you indication on the accuracy of DH...

[DRCUSTOMPARTS]

If it was a supercharged GP he would be able to beat you, there's a lot more mods available for the S/C V6 than the N/A V8. Some of them are turning 11's with more boost/cam/intercooler. They don't even make headers for the GXP, so you're limited with what you can do to it. A turbo would get it into the 12's easy though!

http://www.youtube.com/watch?v=6NS03jBi-XQ&feature=related