# 2.25'' exhaust is fine?



## max9505672 (Dec 1, 2010)

I have a 2.25'' mandrel bend TT exhaust on my Mk1 rabbit but i'm going turbo for next summer and I'd like to know if it's going to be too restrictive?

I'll be running a little turbo (T3 60 trim) with low boost aiming for maximum 200hp.. Maybe 2.5'' would be better but as no one makes bigger exhaust than 2.25'' for Mk1's it'll have to be custom so my question is: Would the investment really worth it or my actual exhaust could do the job?

Thanks


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## Capt.Dreadz (Jun 4, 2003)

To restrictive...You'll be choking the sh*t outta that turbo. Go 2.5".


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## 206danebmx (May 16, 2001)

TT makes a 2.5", if you're talking 16v. Even if it is not 16v, you should be able to adapt it. Check the link below:

http://techtonicstuning.com/main/index.php?main_page=product_info&cPath=2_11_4_16_67&products_id=53


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## max9505672 (Dec 1, 2010)

Without being optimal I am still going to be able to achieve that ''around 200hp'' with that 2.25'' exhaust?


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## TBT-Syncro (Apr 28, 2001)

max9505672 said:


> Without being optimal I am still going to be able to achieve that ''around 200hp'' with that 2.25'' exhaust?


would you sooner make 200hp at 8psi or 14?


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## Capt.Dreadz (Jun 4, 2003)

TBT-Syncro said:


> would you sooner make 200hp at 8psi or 14?


I'll take "What's less restricting & allows you to make more power with less boost..." for $500 Alex (Trebek)


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## chadr (Feb 12, 2000)

the bigger exhaust the better you'll be, as they said. However, I still have a 2.25" tt exhaust and 200 hp at about 10 psi with a 2.0 16v. Didn't want to replace the exhaust at the time and so far I've been happy with just 200 hp. 200hp and satisfied probably isn't the norm around here though.


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## max9505672 (Dec 1, 2010)

Thank you Chadr thats what I wanted to hear.. I may have to boost a little bit more than 10 psi since it's only a 8v for my part but I think I can reach my goal


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## elRey (May 15, 2001)

300whp @ 6KRPM and 16psi on *2.15"* stock mk4 cat-back exhaust. 2.0L 16vt


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## pimS (Jan 7, 2009)

You can make it with the small exhaust, but your cheap fix could cost you more in the long run.
Running more boost puts more stress on the engine + things will get a lot hotter with the small exhaust. Wich is what you don't want.


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## cabzilla (Jan 3, 2000)

elRey said:


> 300whp @ 6KRPM and 16psi on *2.15"* stock mk4 cat-back exhaust. 2.0L 16vt


and it probably would have been 370whp with a proper exhaust. what's your point?


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## elRey (May 15, 2001)

cabzilla said:


> and it probably would have been 370whp with a proper exhaust. what's your point?


Read the thread then I think my point will be evident.


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## HidRo (Sep 19, 2003)

Whoah!
70whp on a 300hp engine, just by changing the exhaust?
I would love to see that on a dyno!


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## sp_golf (Nov 28, 2007)

HidRo said:


> Whoah!
> 70whp on a 300hp engine, just by changing the exhaust?
> I would love to see that on a dyno!


More like 30-40, still a big restriction if you ask me.
Anyone that wants to run a small exhaust on a turbo car, get an electronic cutout and 3" DP


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## cabzilla (Jan 3, 2000)

HidRo said:


> Whoah!
> 70whp on a 300hp engine, just by changing the exhaust?
> I would love to see that on a dyno!


I picked up 50 whp going from a catted 2.5" to a straight 3" eight years ago. This was ~13psi on a small turbo vr6.


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## HidRo (Sep 19, 2003)

Wouldn't the catalyst rob that power? And not only you could get something free by going 3", but also due to the cat removal?


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## max9505672 (Dec 1, 2010)

I thought about using an electronic cutout and 3'' DP I even posted on Vortex and people kept telling me it wasn't a good idea.. Have you ever seen an electronic cutout on a turbo engine? I was thinking about putting it right after de DP, before the 2.25'' exhaust..

And what about the one made by Raceland?: http://www.racelandus.com/p-68-3-electric-cutout-bypass-exhaust-system.aspx


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## max9505672 (Dec 1, 2010)

I'm going to use the car for street and occasionnal trackdays.. On the street on everyday basis, I wont need that 3'' exhaust and for the trackdays, I could just hit that little switch to go wide open 3''


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## elRey (May 15, 2001)

http://forums.vwvortex.com/showthre...16vT-build&p=67911054&viewfull=1#post67911054










Having gone that route, I'd say avoid electric and fab a boost actuated cutout.


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## max9505672 (Dec 1, 2010)

Why? It broke?


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## elRey (May 15, 2001)

Over time (months) the motor gets weaker and weaker and stops holding the valve tightly closed.

Of course I used it daily


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## HidRo (Sep 19, 2003)

1st question, did you dyno with and without the cutout? So you would see the power gain?

2nd question, isn't that 16V engine, from the Golf2?

Edit: kept on reading your thread, and I got to the dyno graph, but it's with more boost, so it doesn't really compare


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## sp_golf (Nov 28, 2007)

cabzilla said:


> I picked up 50 whp going from a catted 2.5" to a straight 3" eight years ago. This was ~13psi on a small turbo vr6.


I picked up 58whp going from stock cat/2.25/VR6 muffler to open DP 2.5" DP :laugh: [email protected] vs [email protected] I put a bit more timing in it @ open DP but you guys get the point


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## HidRo (Sep 19, 2003)

So, you could have 358whp if you went from stock VR6 to 3"! :laugh::laugh:


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## sp_golf (Nov 28, 2007)

There is lots of power to be gained from going 2.25" to 3". That is the point.


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## GTijoejoe (Oct 6, 2001)

Capt.Dreadz said:


> To restrictive...You'll be choking the sh*t outta that turbo. Go 2.5".


Honestly this isn't true....2.25 to 2.5 isn't such a huge difference that 2.25 is super choke and 2.5 isn't..... realisitically look at his power goal 200hp max

My original setup many many years ago was the 2.5" dp to stock ABA cat ( I think 1 7/8") to a 2.125" catback. made 207whp, 222wtq @8psi on NGP's dyno.

Think about how many OEM tubocharged vehicles there are with small exhausts (by our aftermarket standards) let alone instantly going into a super restrictive cat.... for your power goals 2.25" will be fine, it would be best to utilize a 2.5" but if nobody makes it and you don't want to sped $5-600 for someone to make it, it won't be a big deal, its not like you are going to have super high EGTs, knock issues etc etc....... could you make more power with a larger exhaust, yes.... could you make your power goal with less boost, yes. Is it really going to make a giant difference at your power level... NO not in my opinion, there are so many examples of vehicles which should have similar restrictions make the same or more power

Unfortunately you have to realize you've asked a question on a forum which is obsessed with performance, so the majority of ppl are going to answer with that mind set.
I think a good case in point is my Evo9, stock is 286hp, 289tq @ 19psi tapers to 14 at readline....the exhaust is 2.25" on the dp side, has a smashed section to clear the transfer case and than as a 2.25" catback. I've tuned this car on the stock setup to 22psi holding until redline, without a doubt making 300+bhp/btq... if you generically asked anyone on this site about this type of setup they'll tell you that 2.5" pipe is too small... 'choked' if you will, but obviously that isn't the case... and certainly it will make a ton more power with a full 3" setup, but the current setup isn't dangerous even though the 3" is best. Its really about your power goals and what is required to get there safely/reliably.

Edit: Correction, I just got home and measured my stock evo exhaust, full 2.25" and makes at least 220awhp 100% stock on CBRD's lowest reading mustang dyno ever (~250+ dynojet). It was really easy to measure because I had to cut it off the car when I changed it out since the flanges were so rusted lol :laugh:

FWIW, you should have absolutely no problem making 200whp on 2.25" exhaust, especially with 2 wheels


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## Big_Tom (Aug 19, 2007)

3" ftw :thumbup:


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## GTijoejoe (Oct 6, 2001)

Measured my stock exhaust and updated my previous post


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## .T.o.n.y. (Apr 3, 2003)

GTijoejoe said:


> Honestly this isn't true....2.25 to 2.5 isn't such a huge difference that 2.25 is super choke and 2.5 isn't..... realisitically look at his power goal 200hp max
> 
> My original setup many many years ago was the 2.5" dp to stock ABA cat ( I think 1 7/8") to a 2.125" catback. made 207whp, 222wtq @8psi on NGP's dyno.
> 
> ...


Finally a knowledgeable response.... Most on here "hear" something then pass that info on as their own and swear by it. Your power goal is easily attainable with 2.25" hell i made well over 300 horse on my VRT with the Autotech 2.5" catback with magnaflow muffler. If its in your budget go for 3", if not 2.25" will work just fine.


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## sp_golf (Nov 28, 2007)

2.Quick said:


> Your power goal is easily attainable with 2.25" hell i made well over 300 horse on my VRT with the Autotech 2.5" catback with magnaflow muffler. If its in your budget go for 3", if not 2.25" will work just fine.


That's just common sense, but going with a bigger exhaust is worth the power gains. Just because something is possible doesn't mean it's the best way or even a good way to do it. slapping together a turbo set up is easy, anyone can do it and make okay power.. doing it properly is something a lot of people have no clue about.


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## vento86 (Oct 13, 2008)

206danebmx said:


> TT makes a 2.5", if you're talking 16v. Even if it is not 16v, you should be able to adapt it. Check the link below:
> 
> http://techtonicstuning.com/main/index.php?main_page=product_info&cPath=2_11_4_16_67&products_id=53


i plan on getting this for my all motor bunny


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## TBT-Syncro (Apr 28, 2001)

sp_golf said:


> That's just common sense, but going with a bigger exhaust is worth the power gains. Just because something is possible doesn't mean it's the best way or even a good way to do it. slapping together a turbo set up is easy, anyone can do it and make okay power.. doing it properly is something a lot of people have no clue about.


all this talk of power, but no one has brought up how much higher EGT will be with the smaller exhaust, and if anything, thats the real reason to properly size.

:beer:


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## pimS (Jan 7, 2009)

TBT-Syncro said:


> all this talk of power, but no one has brought up how much higher EGT will be with the smaller exhaust, and if anything, thats the real reason to properly size.
> 
> :beer:


I did, but they keep blabbering about the power output


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## Jeebus (Jul 8, 2001)

sp_golf said:


> slapping together a turbo set up is easy, anyone can do it and make okay power.. doing it properly is something a lot of people have no clue about.


Well put. :beer:


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## GTijoejoe (Oct 6, 2001)

TBT-Syncro said:


> all this talk of power, but no one has brought up how much higher EGT will be with the smaller exhaust, and if anything, thats the real reason to properly size.
> 
> :beer:


Actually we did, and "how much" is something no body even knows nor can reflect thats its no good.
For example you think my EGT's on my Evo are dangerous 100% stock? I don't think so, and it still makes more power than the OP's goal on a 2.25" exhaust... his is just an example FWIW, every setup is going to be different especially on different engines, bu its a great example to put things into perspective on what is "necessary" and that is desired.


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## sp_golf (Nov 28, 2007)

TBT-Syncro said:


> all this talk of power, but no one has brought up how much higher EGT will be with the smaller exhaust, and if anything, thats the real reason to properly size.
> 
> :beer:


EGTs aren't really an issue, especially if the tune takes EGTs into consideration. I can tell you that the difference between 2.25" catback and open 2.5" DP @ 250whp is almost negligible as far as EGTs go.


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## max9505672 (Dec 1, 2010)

Thanks Gtijoejoe for your answer, that's pretty much what I wanted to confirm. I know 2.25'' might not be optimal that's just commom sense but as long as my goal is reasonably achievable it's ok.

For the DP now, should I go 3''even with the 2.25'' exhaust line? That way if I want to upgrade anyday the DP will already be done


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## sp_golf (Nov 28, 2007)

max9505672 said:


> Thanks Gtijoejoe for your answer, that's pretty much what I wanted to confirm. I know 2.25'' might not be optimal that's just commom sense but as long as my goal is reasonably achievable it's ok.
> 
> For the DP now, should I go 3''even with the 2.25'' exhaust line? That way if I want to upgrade anyday the DP will already be done


Go 3" on the DP.


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## .T.o.n.y. (Apr 3, 2003)

Im not understanding why theres so much debate? The OP asked if 2.25" would be too restrictive and the answer is no. Less exhaust restriction the better, will 3" be better with lower EGTs? Sure but it doesnt sound like this guys trying to build a monster it sounds like he just wants something fun.


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## chadr (Feb 12, 2000)

I know this thread is pretty much complete, but I did get to a dyno last week and made 210 whp at 10 psi with a 2.25" tt exhaust. At 6 psi it was 180 whp. For the sake of my 020 and whatever else may be prone to breaking I may not be pushing more than 10 psi for a while. ~240 hp at the crank isn't too bad in a light a2 anyhow.


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## GTijoejoe (Oct 6, 2001)

chadr said:


> I know this thread is pretty much complete, but I did get to a dyno last week and made 210 whp at 10 psi with a 2.25" tt exhaust. At 6 psi it was 180 whp. For the sake of my 020 and whatever else may be prone to breaking I may not be pushing more than 10 psi for a while. ~240 hp at the crank isn't too bad in a light a2 anyhow.


... well now its really complete :laugh::snowcool:


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## .T.o.n.y. (Apr 3, 2003)

chadr said:


> I know this thread is pretty much complete, but I did get to a dyno last week and made 210 whp at 10 psi with a 2.25" tt exhaust. At 6 psi it was 180 whp. For the sake of my 020 and whatever else may be prone to breaking I may not be pushing more than 10 psi for a while. ~240 hp at the crank isn't too bad in a light a2 anyhow.


what turbo are you running?


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## Big_Tom (Aug 19, 2007)

sp_golf said:


> That's just common sense, but going with a bigger exhaust is worth the power gains. Just because something is possible doesn't mean it's the best way or even a good way to do it. slapping together a turbo set up is easy, anyone can do it and make okay power.. doing it properly is something a lot of people have no clue about.


this :beer:


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