[theuntouchable]

I haven't started diagnosing yet as this just happened... I think i know what the problem is but it won't hurt to get a second opinion.

Got my cats sliced off last night.

This morning, 1st and 2nd gear have now power what so ever.... my boost gauge confirms as even at WOT it won't go past 0 psi. It's feels like stock.

3rd gear onwards... power comes back and boost at WOT runs normal (about 13.5 psi).

While at the exhaust shop i noticed the guy used smaller diameter pipes (much smaller) after taking off the cats. When i asked him why he said that it would be better for fitment purposes.

Could this be causing the problem? or maybe an exhaust leak?

I didn't notice last night as i wasn't giving it much throttle. It was way too loud after getting the cats removed and just sounded horrible!!

All my mods are in my signature.

The only ones i haven't put in yet are the cams, oil separator and electric water pump. (was planning on putting them in this weekend)

[05horse]

im sitting at the shop now about to have mine cut off.


figure worse case senario..high flows since ford wants $1600 a pair, and no one seams to have 1 extra layng around lol




least im getting a H pipe out of it

[2oo5GT]

that's strange that they used a smaller diameter. they can still use a 2.5 pipe and flare out the ends more to fit over the stock 2.5 pipes. That's just either being cheap or lazy. Now that section is a small restriction.
Usually when you go to a more high flow exhaust, you could lose 1lb of boost but your issue is strange. So no boost in 1st and 2nd and then it comes on in 3rd? I have Bassani midlengths, X pipe with no cats and catback and see a solid 15psi in 1st gear and so on.
I would check all of your vacuum's and make sure everything looks good.

[gmantheman]

Originally Posted by 05horse

im sitting at the shop now about to have mine cut off.


figure worse case senario..high flows since ford wants $1600 a pair, and no one seams to have 1 extra layng around lol




least im getting a H pipe out of it

Ford wants 1600 for a pair of cats? That's expensive. These are the hi-flows that I bought mpe-59956 - Magnaflow 2.5" High-flow Catalytic Converter for all Mustangs - Catalytic Convertors - Mustang Performance Parts

[theuntouchable]

Originally Posted by 2oo5GT

that's strange that they used a smaller diameter. they can still use a 2.5 pipe and flare out the ends more to fit over the stock 2.5 pipes. That's just either being cheap or lazy. Now that section is a small restriction.
Usually when you go to a more high flow exhaust, you could lose 1lb of boost but your issue is strange. So no boost in 1st and 2nd and then it comes on in 3rd? I have Bassani midlengths, X pipe with no cats and catback and see a solid 15psi in 1st gear and so on.
I would check all of your vacuum's and make sure everything looks good.

Shouldn't the restriction affect all gears though? How come it is only affecting 1st and 2nd?

I've already checked all the vacuum lines and all is good.

I will definitely be taking it back to the shop and changing out the pipes. I'm just trying to understand why this is happening.

Can anyone explain it?

[mustangdave2008]

Well, first off, that's a Federal crime. But, to each his own.
What did they do with the O2 sensors? Their location is critical to proper operation. The second set of sensors tells the computer how the cats are doing so you have really confused the car now. Most likely,a custom tune can fix you up, but driving it without one, you risk catastrophic engine failure because of out of whack air/fuel ratios. The car may be in limp home mode.
A tune can cut off the second set, but you have to have the first set on and in the right location.

[theuntouchable]

Originally Posted by mustangdave2008

Well, first off, that's a Federal crime. But, to each his own.
What did they do with the O2 sensors? Their location is critical to proper operation. The second set of sensors tells the computer how the cats are doing so you have really confused the car now. Most likely,a custom tune can fix you up, but driving it without one, you risk catastrophic engine failure because of out of whack air/fuel ratios. The car may be in limp home mode.
A tune can cut off the second set, but you have to have the first set on and in the right location.

Well... first off, I don't live in the US so it's not a federal anything

If you'd just take a second to look at my sig you wold have noticed that i DO have a custom tune.

I've spoken to Brenspeed and they said they had disabled the o2 sensors in the tune and that it would be alright for me to take off the cats.

[q8wellcraft]

run your car on the dyno and check the air and the fuel i think u need a new tuning

[Crazystang89]

Something is messed up with your tune. Removal of the cats should in no way affect your supercharger making boost.

[stlwagon]

Originally Posted by mustangdave2008

Well, first off, that's a Federal crime. But, to each his own.
What did they do with the O2 sensors? Their location is critical to proper operation. The second set of sensors tells the computer how the cats are doing so you have really confused the car now. Most likely,a custom tune can fix you up, but driving it without one, you risk catastrophic engine failure because of out of whack air/fuel ratios. The car may be in limp home mode.
A tune can cut off the second set, but you have to have the first set on and in the right location.

Rear O2 sensors have zero to to with air/fuel ratio. They control nothing.

[stlwagon]

Originally Posted by theuntouchable

Shouldn't the restriction affect all gears though? How come it is only affecting 1st and 2nd?

I've already checked all the vacuum lines and all is good.

I will definitely be taking it back to the shop and changing out the pipes. I'm just trying to understand why this is happening.

Can anyone explain it?

If anything I would expect you would be seeing more boost with the smaller pipes.

[Back@itagain]

Originally Posted by theuntouchable

Well... first off, I don't live in the US so it's not a federal anything

Hilarious! I always find it comical when people want to talk about the law and can't even get jurisdiction right!


Hope you got it figured out by the way...lets us know what it turned out to be.

[jgorm]

Originally Posted by Crazystang89

Something is messed up with your tune. Removal of the cats should in no way affect your supercharger making boost.

+1. There is some other issue.

[theuntouchable]

Originally Posted by jgorm

+1. There is some other issue.

Even though the tune was just fine right up until i removed the cats? What could be wrong with the tune?

What other issue could there be?

[gtcrafty]

Not enough backpressure?