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

Ditch the stock exhaust... it's like putting a banana up the damn tail pipe.

Mark

I used my stock exhaust for a while, car performs much better with my 2.5" diy rig, but stock was tolerable to keep things as simple as possible when installing my turbo.

I followed the begi install directions to a t and eventually the DP put so much pressure on the exhaust that it cracked at the cat flange.

Before the exhaust cracked the car was freaky quiet. Like some kind of luxury car or something.

im running a turbo soon i got a magnaflow highflow cat and a borla cat back, should i get a straight through or keep the high flow?

I ran around with my stock exhaust on for a while, no big deal. A lot of power was left on the table, but it was nice to get the car up and running quickly. It was also ridiculously quiet, like silent. Now I have a 2.5" system with a highflow cat and $25 flowtech muffler. Unless someone can back it up with some proof, I don't believe a 2.5" cat is going to be a bottleneck in a <250 hp car.

If I decide to make my own exhaust will I have to tell begi to use a bigger flange on the downpipe or it doesnt matter?

Im guessing they use a smaller flange otherwise to mate to the stock exhaust, id just like to clerify this.

Sounds like BEGi are the people to talk to about this one.

My cat cost about 10 whp in a 250 whp car, and a little response too. Partly due to the fact I can't hold boost up to redline. Used to hit 13 psi, now it's more like 11. I'm a sad panda.

At least you aren't a Trueno Panda. :inout:

Ben, that wastegate solution I was telling you about has been working great. However, I was not able to source you an extra actuator. Bolts right in, just needed to be lengthened.

Kindly remind me what the actuator was from.
Ben's going to look through his pile o turbo parts for a spare 16G actuator.

off a 300zx t25 iirc.


http://i21.tinypic.com/zwep0n.jpg

There is a cheap one they are talking about on m.net