Richard,

I removed the secondary cats on my oem exhaust and did a 2.25" "gundo" hack mod... it does sound leaps and bounds better then stock ( but that is not saying much) and it freed up the flow .. it feels slightly faster and better throttle response but ....at that rate... why not get a europipe so you can keep the Swiss police happy ?

 

I think if you are going to leave any of the stock piping in there, you would be better off to do the simple hole saw mod instead which works well for mild mods.

 

I tried that once didn't like it, so will do it the hard way

 

When you do it that simple way you by pass the stock piping which is good but I think to leave any of the stock piping in is not a good performence choice unless you still plan on using the hole from the simple mod but then it doesnt make sense to go to the other way also??

 

well this way I am getting rid of the MOST of the constricted piping & have already removed 80% of the cats. Drilling directly through the rear pipe for the bypass sounds crap after you have removed the cats & doesn't add anything to performance

 

It does sound like crap if the cats are removed and hole saw.
Really from what I saw on the dyno with stock exhaust mods is , wasting your time doing a complete gut of ALL the cats with stock piping and no hole saw mod....Better to leave only one cat on each side and then do the holesaw for better sound and performance, dyno proven, over above method.No need to remove both cats because the stock inner piping CAN NOT make use of that extra flow...unless hole saw is added..
Still the best is 2.5'' piping swap..
I am done with this stock exhaust stuff...lol..Good Luck.

 

http://forums.rennlist.com/rennforum...ke-inside.html

John, if you read what I wrote & have studied the pics above, I have already tried the holesaw with 100 cell cats only and its CRAP, Drone & No Performance, hence why it makes sense to go STAGE 2 or 3 and cut out he bull**** mid section of the OEM set up and run this with 100 Cell Cats & no Pac Mans

 

Richard,I dont know how a 100 cat sounds in a stock exhaust mod ,never heard one with those exhaust mods.Only totally gutted or with one factory cat..
That is very weird you didnt get any performance out of a cat/ hole saw mod But if your car is more modified then a flash you probably wouldnt notice as much..
Just trying to share here,and hopefully help..
Just be done with it if you are modifying more then a flash with your car and buy a good after market one..

 

& then go to Jail with the Swiss Police ! that is exactly why I am trying to Mod the F..K out of the OEM system in a sensible manner, did u look at my Dyno as you asked for one ????

 

Just be done with it if you are modifying more then a flash with your car and buy a good after market one..[/QUOTE]

yep, i agree 10000 %... take your time and save your money for well built parts... don't waste your time on a stock exhaust!!! with a flash and a nice exhaust you'll feel the best bang for your buck.. do it at the same time, trust me.. all others, unless you go big, will never compare to these two!!!

Good luck!

 

HI,Yes I did look at it and forgot to put the to together..
That is a nice HP line ,as it carries it pretty good, once it does hit..That is probably DIN HP ratings,a tad more then SAE..Nice peak TQ numbers when converted also. ..Rear wheel dyno I take it.
So,I dont think your car just has just a tune..lol..
What exhaust did you use for that ,the current one?
Maybe you could do a 2.5''cross pipe in the muffler body which others do use to make big HP with that type,like Protomotive.

 

John, That was a Rear Wheel Dyno with the 2.5 Inch Speedtech on, although it didn't rev noticeably more easily with this system. Here are the pics of the LHS part section I intend to remove

 

If you don't want to drop $2-3K on a new exhaust and you have some fab skills you can custom build your own as I am doing. Picture below is in-process x-pipe before welding....look for an upcoming DIY thread on this, I am just waiting until I complete and install for full step-by-step (I don't care for in-process wait 2 weeks for the next update thread). Plan is cat-delete, x-pipe, dual straight mufflers, and stock tips.

 

I think you fail to see Richards point. He is not trying to be cheap. He is far from that, I have done business with him. He has the $$ to go out and buy an exhaust, and he has. He is trying to comply with Switzerland automotive noise/exhaust law in keeping the exhaust quiet but louder when he really gets on it but most important he wants free flowing. He also wants to keep the stock exhaust frame/work so it looks 100% stock to the Swiss police...

 

Richard, if you are going for performance, removing those won't do anything. If you are going to make it slightly louder, i would remove 2/3 in order to help with keeping drone down. What i did like i said before, remove the secondary cat, but you know how that secondary cat has a shield at the end covering it up and pushing the air flow to the outside wall of the exhaust, leaving a 1.5" gap between the shiled and the wall of the exhaust where the exhaust air goes ( very restrstive). I took that shield and flipped it, so it would make the flow of the air go towards the middle of the car. I had it so that shield would point to the cut out 2.25" of the drill hole i made, BUT even then.. still restrictive.