Ok...Is it safe to have a full 3" exhaust
...with a 2.5" inlet muffler?

 

Is it safe? Yes. Is it going to be beneficial? No. It will undo any positive effect the 3" exhaust gives you.

 

What is the downside to having this setup? and are there any benefits?

 

Is this on a turbo or n/a?

 

TII...with a...i think a t03 turbo

 

With a 2 1/2" muffler there is really no point in having the 3" exhaust pipe from the turbo. You are adding a restriction back to the system. If you are going to do this then you may as well run 2 1/2" all the way from the turbo. The car will run just fine but you may see a little quicker spool up and a little more horsepower from the 3" muffler. It may be a similar effect to running with and without a cat. On a turbo no exhaust is best so go as large as possible. There is a way to make a smaller pipe work but this isn't it. One thing that could be beneficial is if you run the turbo straight into a larger pipe such as 3 1/2" to 4" and then taper it down to a smaller size around 3" about a foot later. This has a neat effect on turbos of helping to simulate no exhaust but only if the piping size chosen is large enough.

 

I was just wondering...because before i had a 3" muffler on it, but it was just too loud, so i put on the stock muffler. I noticed that when i had the 3" muffler, the turbo would always be spinning...even at low rpms, but now that i have the smaller muffler...it only spools up when i punch it or when i'm at higher rpms.

 

any thoughts on this?

 

http://www.supraforums.com/showthrea...hreadid=110847



prolly one of the best tech threads out there

 

just wondering... what if from the 3" pipe to a y-pipe 3" inlet-2.5" outlet then two 2.5" mufflers? would that be somewhat similar as 3" straight thru? or just any piping from bigger size to two smaller size?

 

anybody else?

 

IIRC thats racing beats setup.

I like singles though. Less bends, less restrictions, less weight. They are just a little louder generally (true duals aside )

 

Two 2.5" pipes have considerably less restriction that a single 3" pipe. That fact more than compensates for the restiction caused by a well-built Y-pipe, so a single sytem isn't necessarily less restrictive than a dual.
A dual system will weigh more, but the difference is a tiny fraction of the car's total weight, so the chances of you actually noticing it are slim.
The big advantage of a dual system is that two parallel mufflers work much better at reducing noise than a single one. While exhaust volume is always a personal preference, the authorities may not necessarily agree with your preference...
Cost is a non-issue. Either you're happy to pay a bit extra, or you're not.

BTW, I believe RB's system splits into two 2.25" pipes (I may be wrong), which won't flow as well as a single 3".

 

The whole idea for a turboed car (IF you want more hp) is to free up the exaust. The larger you go all the way back lets say 3" to a 4" tip the better the turbo will spool up. If you have a 3" then go to the 2.5" it really doesnt help at all. But i see that your worried about the loudness of this system. I feel that turbos are actually normally quiter than non turbo so if you ask me having a single is really not that bad, i havent had any problems yet with police (got to be smart about it). So to answere your question if you want your exaust system to be quieter then your going to have to look into a good dual setup. That will give you twice the silencing effect on the car. Just keep in mind you wont get as good of performance than a good single system.
Goodluck

 

Oh yea...i forgot ot mention...its changed to single exhaust...3" exhaust but 2.5" muffler...sorry ididn't specify that.

 

And...do the presilencers effect performance much? and do they really muffle the sound a lot?

 

3" going into 2.5" mufflers is like the bottle neck effect (or imagine a funnel with water going thru it)

 

Yes, presilencers help quiet the exhaust note tremendously!

If you had a 3" single system w/ no presilencer I can imagine it was loud. I have a 3.5" turbo back single w/ only 1 muffler and it is INCREDIBLY loud w/ the tip silencer removed.

I mean, I had an NA and drove it on w/ only the thermal reactor and two precats and it was actually quieter!

Your presilencer must be stainless and have stainless or ceramic packing to stand up to the heat! I have heard Borla XR-1 mufflers work well.