Finally solved...the 3rd cat vs no 3rd cat debate

[99V8SHO]

Today I had my 3rd cat replaced with a piece of straight pipe. I figured that now would be a good time to get some solid 0-60 times. Here are my findings.
Mods: - K&N cone in engine bay (Yes, I know, a true CAI is in the works)
- Borla mufflers, no resonator

0-60 times: All runs done within two hours of eachother. Outside temp reading pegged at 74F. 70% humidity. The straight is an 1/8 mile perfectly flat stretch.

- 3rd cat in place: First run - 6.71
Second run - 6.74

- 3rd cat replaced with straight pipe: First run - 6.54
Second run - 6.61

- Running right off the y-pipe: First run - 6.84
Second run - 6.89

- With stock exhaust (before ANY exhaust work) I ran a consistent 6.85


So as you can see, no low end torque was lost with the removal of the 3rd cat, in fact it made me quicker. Running right off the y-pipe, however is not the way to go. But I will tell you this. It sounds SUPER sweet. Almost deafening. Sounds like an F-body on crack. I agree that every V8 SHO owner should listen to their exhaust uncorked at least once before they (or their SHO) dies. You will not regret it...though your neighbors will.

 

[SHOGrabber]

Sweet! That is some good info. I have been wanting to do this with a new flex pipe myself. I will also do the test before and after.

 

[99V8SHO]

Keep in mind that these are only 0-60 times. 1/4 mile times may be different. I unfortunately, do not have a 1/4 mile straight around here to test on.

 

[2 4shofast]

I knew that is sounded much better when I removed it but it is good to know that faster times might have been acheived also. Thanks for the good info

 

[Glue Maker]

D@mn, now I have to do it

 

[99V8SHO]

Here are some pictures comparing the new pipe to the cat-pipe.

 

[djbartu]

How would you compare the sound with vs. without the third cat?

I would love to remove it (easy mod to knock 2 tenths off the 0 - 60). However, my car is loud enough with the Flowmasters and really don't want it any louder.



By the way, those are good 0 - 60 times! Measured with a G-tech Pro,the best I ever got out of my '96, with mods, was 7.5 seconds (which is about the same as the magazines got back in '96).

 

[99V8SHO]

I really don't think I am really running 0-60 in 6.5 seconds. I see the time flash at me just before my speedo reads 60. But that doesn't bother me. The thing I like about the GTech is it is consistent. If it is giving me false readings, it is being consistent with the false readings. I have done the runs on the same stretch every time, albeit in different weather conditions, but not the case with my little experiment with the cat.
There is a noticible volume increase and a slightly throatier growl at idle and in low RPMs. I didn't really notice a huge volume difference at WOT. I don't think it will be unlivable with Flows.

 

[DavidT]

nice work.
Did you fabricate the straight pipe (and weld the hanger pcs. and 2 flanges)
is it bolted in at each end?

 

[99V8SHO]

I came up with the idea and brought it up to a guy I know who does custom exhaust work. I provided flanges and gaskets and some cash and he provided me with a cat bypass. The flanges are welded on to each end of the test pipe and on to each end of the cat. I can bolt either one in whenver I choose.

 

[DavidT]

hmmm. Maybe you should look in to hosting a group buy

 

[99V8SHO]

I was actually thinking about it. I am having this same guy custom fab me a CAI. He said it could be done, I just need to bring it in for measuring and fitting. I have no problem hosting a group buy. I would be something like $100 for the bypass and $50-$75 for the CAI plus shipping. The problem is I cannot pay for all this up front as I am a college student with limited income so I would need payment up front and people do not like doing that.

 

[DavidT]

well, I would like to see the CAI when its finished. I may be interested in both.
I am also thinking about an exhaust cut out too... wouldn't it be overkill WITH the bypass pipe?

 

[99V8SHO]

Don't see why it would be. The point of the cutout is to have the exhaust as free-flowing as possible, correct? A cutout would accomplish that, along with the lack of a cat. If anything, that bypass pipe would make a more convenient spot to put a cutout.