is a downpipe worth it?

[JiveMasterT]

as many of you know, punishment racing is having a neat special on DPs for this month, and im considering getting one of those. i have a full 3inch straight through exhaust and i was wondering if getting a 2.5 inch downpipe would be worth it? i am mostly stock, except for the stuff listed in my profile. please let me know... theres only a few days left, .

 

[Drifter00]

Yes, the stock downpipe is very small and thus very restrictive. You will notice a nice gain by adding a 2.5" DP and a high flow cat/test pipe.

 

[TurBoGs-T]

You said you have a straight thru exhaust now. Or is it just a 3 inch catback with the stock Dp. If the 2.5 is dirt cheap then i would go for it cause you can do damage with a 2.5 dp. But if it's not all that good of a deal and you don't want to worry about upgrading again. i would just go 3. don't get it twisted 2.5 has alot of potential. But you won't get the full potential of the 3 inch you have now if you go 2.5.

 

[fish3rboi]

Yea that puzzled me, why go a 2.5" when you currently have a 3" setup. Just complete the 3" setup.. Unless you like buying things twice! Then go right on ahead.. get the 2.5" and immediately start saving up for the 3" because you will want it

 

[midnght]

Think of your exhaust as a bottle. The downpipe is the neck and the rest of the 3 inch system is the fat part of the bottle.

Now, fill a glass of water and just flip it upside down over the bottle neck. You will get some water inside, right.

Then, take another bottle (equal size) and cut the neck off so that is is the shape of a cup (equal roundness all the way from top to bottom. Fill up that glass of water again and flip it over the top.

You get more water through the top and end up filling the glass more than if it had a bottle neck. Turbo cars produce enough gas to flow very fast.

Replace:

Water-->exhaust gas
Bottleneck-->stock downpipe
cutoff bottleneck-->3" downpipe
rest of bottle-->3" downpipe back (testpipe or more restrictive 3"cat)

You will only flow your smallest opening. There are MANY analogies you can read on the site. But they are all going to tell you the same thing. Get a full TURBOBACK 2.5 or 3 inch system and be done with that part of your buildup!!

 

[fish3rboi]

Originally posted by midnght
Think of your exhaust as a bottle. The downpipe is the neck and the rest of the 3 inch system is the fat part of the bottle.

Now, fill a glass of water and just flip it upside down over the bottle neck. You will get some water inside, right.

Then, take another bottle (equal size) and cut the neck off so that is is the shape of a cup (equal roundness all the way from top to bottom. Fill up that glass of water again and flip it over the top.

You get more water through the top and end up filling the glass more than if it had a bottle neck. Turbo cars produce enough gas to flow very fast.

Replace:

Water-->exhaust gas
Bottleneck-->stock downpipe
cutoff bottleneck-->3" downpipe
rest of bottle-->3" downpipe back (testpipe or more restrictive 3"cat)

You will only flow your smallest opening. There are MANY analogies you can read on the site. But they are all going to tell you the same thing. Get a full TURBOBACK 2.5 or 3 inch system and be done with that part of your buildup!!

That confused the hell out of me until I read it for my third time. Should make a video to demonstrate what you were describing. Would take less time to understand.. j/p

 

[midnght]

Originally posted by fish3rboi
That confused the hell out of me until I read it for my third time. Should make a video to demonstrate what you were describing. Would take less time to understand.. j/p

How bout this:


TURBO-dp-HIGHFLOWCAT-2.5"EXHAUST-2.5EXHAUST OUTLET


lower case is smallest section and will be choking the gas

 

[fish3rboi]

 

[JiveMasterT]

thanks guys, maybe after i do my intercooler piping then ill go for a full 3 inch downpipe. i have a 3 inch cat-less exhaust at the moment and that will have to do i suppose.

 

[TurBoGs-T]

Originally posted by JiveMasterT
thanks guys, maybe after i do my intercooler piping then ill go for a full 3 inch downpipe. i have a 3 inch cat-less exhaust at the moment and that will have to do i suppose.

Opening the exhaust will do alot more than the intercooler piping. The turbo is driven by the exhaust. So even if you make it so it's capable of getting more air into the engine you are still gonna be stuck pushing the same out. Right now that 3 inch back is doing nothing at all. Like Chad and I were tryin to say earlier you are only as good as your smallest pipe. So right now you might as well consider yourself stock. I would highly suggest the dp first. it will make a big difference.

 

[midnght]

 

[psi on u]

what i did (this is me of course ) i went down the street to my muffler shop had them run a 2.5 exhaust built to my car and had them cut out almost all of my down pipe except maybe 9 inch of it and the stock down pipes like 2 .25 so to me that difference is not that big of a deal especially since i paid 180 bucks for a full exhaust

 

[JiveMasterT]

if i went to the exhaust shop by my house and had them make me one it would be much cheaper than buying one premade. my question is, do i need one of those flex sections or not? some of the ones i see for sale have a flex section in them, and i dont think that the exhaust shop would do one, at least not cheaply. i personally dont care about how loud my car is cause its already insanely loud... thanks.

 

[midnght]

A 2.25 bottleneck is still a bottleneck. You are not going to see the full potential of a turbocharged car with ANY bottlenecks in the intake or exhaust track. Why not just spend a little money and do it right
But hey, to each his own. I won't do it like that but you can. Just giving a response that is an answer that would be the BEST outcome, not 'something that gets you by'. Sure you can do it and save, but chances are you will eventually do it right in the end.

 

[ARTSUPRA]

Not to cretisize the punishment racing products but they are only 2.5" and are crush bent, for $99 it's an ovesome deal but I think that 3" from the turbo to the muffler no cats would do nicely and will add more power

 

[JiveMasterT]

yeah yeah yeah, i got that. im going to do a 3 inch down pipe, but do i need a flex section in it like some of the premade ones, or can i just have a solid pipe?

 

[ARTSUPRA]

Flex section is very important first because it takes off the stress and second if you building your own it will never be perfect and you need some flexibility to make exhaust and catback fit

 

[JiveMasterT]

okie dokie, guess that solves that.

 

[herovueboi]

3" dp is pretty big for the garret t-25, the downside of the 3" dp is that you might experience some boost creep.

 

[paranoidTSi]

I put 3" on the stock system, runs fine.

The downpipe is probably one of the biggest upgrades where I actually felt a difference, your RPMS will dramatically improve (as in accelerate)..I noticed my top-end is a little tougher now too.

Don't expect ungodly results, but its well worth the money.

 

[CowPimp]

It's definitely one of the more effective ugprades early on in the modification of DSMs. Go for 3", and go with a mandrel bent DP.

 

[JiveMasterT]

since funds are tight for upgrading my car im trying to do it in peices... im going to be doing a new fuel system and a t-28 in the future, but i need to do the supporting mods first. btw, if i got a boost controller would that stop boost creep? i get it now as is.

also, whats the difference between mandral and crush bent? and what would an exhaust shop likely do? thanks.

 

[midnght]

Originally posted by JiveMasterT
A. btw, if i got a boost controller would that stop boost creep?

B. whats the difference between mandral and crush bent?

C. what would an exhaust shop likely do?

D. thanks.

A. It will help but not cure. It has to deal with the exhaust flow. Most can cure it with the combo of an good electric boost controller and a well ported manifold and o2 housing.

B. Mandrel=smooth bends (Go to here and see what a mandrel looks like. You have to go thrugh the menu, but it is there.)
Press(crush)= has ripples on the inside of the bends, that also makes
for a smaller diameter than what you are going for.

C. MOst shops do only pressbent (crush bent exhaust)

D. Your welcome!!
Here is the flexsection you asked about earlier!


Look here to DIY

 

[Razor_DSM]

i put a full 3" system on my 1G, custom catback and extreme 3" ss DP. Ivr tried it both with a test pipe and the cat, and have seen no major differences except sound and smell, . I would go with a high flo cat rather than a test pipe the car will sound a whole lot meaner (not Raspy), wont smell like rotten eggs, and there will still be more than enough flow for the average dsmer. at the moment im runnung 10psi with no bost creep ( maybe 1 psi) i hate winter, damn oil/coolant leaks and is to god damn cold to fix them.

rule # 47563 - never apply large amounts of boost to a 170k 1g with leaking fluids

oh and pefromance wise all i have in the aircan mods and an afc and man ill tell ya there is a huge difference with a 3", like the difference between a 10psi stock car, and that same car @15psi, not only that the turbo spools fasssst

i did manage to take out my friends 92 TSi awd auto road racing, he has a small 16g at 16psi.

plus when your ready to build your 2.4L , and try to run it on the stock exhaust, *cough* *cough* not reccomended