Thinking about keeping stock exhaust.
 

I was just doing some thinking about my turbo setup. My question is how much spool up and response will I lose if I keep my stock exhaust with cat and use a begi downpipe? and if I ditch the catalytic?

I dont want to spend a lot of money on the whole kit initially and wouldnt mind swapping the rest of the exhaust out later.

Thanks

either way it will kill performance horribly

You can run with the stock exhaust for now if you're keeping the boost very low, but your turbo kit will be severely, SEVERELY hindered by it. For the cost investment, it's a BIG bang for the buck to invest in a 2.5" exhaust.

That plan will work just fine. By the time winter rolls around you can swap that shit out and have a vastly improved car come spring time :D

The cat is a bigger hinderance than the stock exhaust. Get rid of it now, and upgrade the cat-back later as budget allows.

Alright so I guess i'm going all out right from the start. Money isn't the issue here, its taking the smarter approach.

Heres a question. Do exhaust flanges differ depending on the diameter of the pipe used?

I ask because if I get a begi DP which is 2.5inch and thats bigger then the factory exhaust, doesnt the step down at the flange create a bottle neck? What happens if I want to upgrade the rest of it?

Yes the flange changes relative to the size. I progressive step down is no more a flow restriction than the cat, muffler, or even the 2 someodd inch pipe we run stock.

I made 280hp on my Talon with stock exhaust and gutted cat. Was it the right way to do it? No.

So if I decide to go with a 2.5 inch all the way back to match the begi DP, how would I obtain the flange necessary to mate the rest of the system to Begis piece?

The local muffler shop should have them in stock it is only a 2 bolt flange.

Does the flange that comes with the begi DP if mated to the stock exhaust create a bottleneck? Will it have to be replaced or opened up if a new exhaust is installed?

i advise you do it right the first time and save yourself a lot of headaches...do the whole exhaust, you dont have to go all out, do a 2.5" cruch bent mild steel, and you'll be ok with your goals...

I noticed HUGE gains in spool and power just by going from a stock exhaust to a $140 mandrel-bent 2¼" ebay special catback.

Quantitatively: I was at ~75%DC on NB injectors at my AFR targets with the stock exhaust, redline at 7.5-8psi . Retuned with the nex exhaust, and now I run out of injector (100DC) at about 6k rpm at wastegate pressure. I had to set the overboost protection down lower and have to stay way out of high boost until new injectors arrive and get cleaned.

Do it once, do it right. 3" or go home.

I'm with this guy /\

The stock cat is the greatest restriction. I measured it.

Whats the price difference of the pipe?

Besides isnt Begis DP a 2.5inch, does attaching 3 inches to it make that much difference? Unless I have to get a 3inch DP too. I think its marginal benefits after a certain point.

BEGI's DP is normally a 2.75", and they stepped it up right before the wastegate rejoins to a 3" for me for $30 extra. I then had a custom 3" midpipe w/ a 3" Magnaflow cat made to mate the 3" enthuza to the 3" BEGI DP.

On my begi S5 downpipe 3" my gt3071 turbo spools about 700rpm earlier with catless 3" than with factory exhaust. power difference was also major.

My Begi DP does not mate well with my 2.5 FM catback. And it hits the K-member. I'm getting the catback reflanged and a testpipe made next week to mate better with the DP. Probably take the lower section of the DP off and hit it with a BFH.


Frank