[oldman]

To answer the question once and for all, can the Borla 60608 be put on a bone stock exhaust system?
Yes it has been asked and the posted pictures have the Borla front connectors too (between header or stock front cats) to the 60608. We are talking does it work on a BONE stock exhaust.

Why go with the 60608? It is one of the few actual straight through 2 and 3/4 designs. My only fear was if it was going to cure my low rpm 1100 to 1500 resonance issue for instance 40 MPH in 5th,45 MPH in 6h. Without primary cats my engine freaks out at these RPMs and gears.

So today CA offroad pipes, factory headers and the 60608 installed inback of the 2nd cats... results are surprisingly quiet and really no it truly behaves like stock. A surprise because to be honest in general short large diameter resonators don't do much, balance this out that the per piece Borla stuff are 2 and 3/4 (there systems are all 3"). So yup actually works.

So this probably concludes my quest after like 20 tries for a quite system that flows well and that has a high RPM engine sound vs just loud.
stocker headers, CA front cat deletes, move rear 02 to behind factory 2nd cats, factory 2nd cats, Borla 60608, and then stock exhaust back.

Oh, BTW, my ancient Lisle exhaust expander broke 10 years ago or so, I tried two lifetime expanders and they broke first use. I got a lisle (pronounced lyle) and it can actually take a impact gut and it expanded the pipe like butter on a hot cake.


Here it is:

[Gary H]

Heehee, great minds!

[oldman]

Looks like you are running the bone stock x pipe back, your sig says de-cat, but they look like cats. I'd like to know your overall impression on an auto LT4 before and after the setup and why you went to the twin resonators?

[avalonandl]

Our X pipes should be further forward to get the best scavenging. Like right at the front of the 60608 pipe.

[oldman]

I gave up micro-managing the exhaust as the twin wall ID of the front cats is like 1.8" and makes a steep turn. I would assume what you have stated as correct, I don't think it amounts to much.

[Gary H]

Originally Posted by oldman

Looks like you are running the bone stock x pipe back, your sig says de-cat, but they look like cats. I'd like to know your overall impression on an auto LT4 before and after the setup and why you went to the twin resonators?

Secondary cats are hollow & welded back up, done before I started modding.

Why double resonators? Have you heard a fully de-catted system running into a stock suitcase?

[Gary H]

Originally Posted by avalonandl

Our X pipes should be further forward to get the best scavenging. Like right at the front of the 60608 pipe.

I'm sure to let the GM Engineers who designed the original system know

[oldman]

Originally Posted by Gary H

Secondary cats are hollow & welded back up, done before I started modding.

Why double resonators? Have you heard a fully de-catted system running into a stock suitcase?

roger that, IMO it is even worse with the M6

[avalonandl]

Originally Posted by Gary H

I'm sure to let the GM Engineers who designed the original system know

I put the Xpipe there on my 2005 GTO and it gave the car a completely different sound very exotic almost like a Ferrari. But it screamed a higher rpm.

[oldman]

Originally Posted by avalonandl

I put the Xpipe there on my 2005 GTO and it gave the car a completely different sound very exotic almost like a Ferrari. But it screamed a higher rpm.

Stock the GTO did not have an X right? It looks like the aftermarket systems put the X far back, like the 6th gen. To me this is more of a factory sound mod vs a performance (extraction) mod.

[avalonandl]

Originally Posted by oldman

Stock the GTO did not have an X right? It looks like the aftermarket systems put the X far back, like the 6th gen. To me this is more of a factory sound mod vs a performance (extraction) mod.

The GTO had a resonator just behind the cats where the 2 pipes came together. It was the perfect place to put the X-pipe and I replaced the 4 chamber mufflers with Magnaflow 14616 6 inch glass packs.

[gmcvt]

So for Oldman:
stocker headers, CA front cat deletes, move rear 02 to behind factory 2nd cats, factory 2nd cats, Borla 60608, and then stock exhaust back > 1 7/8" Lt's with cats and possibly the 60608's to stock exhaust(npp)?

Considering the 1 7/8 Lt's route, what do you see as the drawbacks to that arrangement besides say heat and cost?

[oldman]

no drawbacks. The stock 2nd cats back probably start cutting into HP at about 550 to 600 HP, say 10 HP, by 750 probably 15 HP or more. 2 and 3/4 sections factory or aftermarket add 50 engine HP to the above numbers for flow issues vs HP loss; basically at that point the crush section and factory suitcase are removed and some 2 and 3/4 replacement stuff added. So just something to consider.
I'd coat the header and heat wrap the starter.

[gmcvt]

Cool. Advice taken. I have been reading through several of your older posts, just gathering data. I thought I remembered at one point (seems a couple of years back) that you commented on possible tip in response/torque potentially effected with the LT's. But I may be remembering that incorrectly because I think in my "counting the cost" thread, you said that it would not.

Thanks again for all this info. For those with ears to hear, you offer lots of advice that can save money and unmet expectations. It is a tremedous gift to be able to read through the posts over the last couple of years from you (and PRAY, FRAXUM ETC...) and gather so much info. There is plenty enough here for the average person to learn and make very good decisions.