Question on exhaust manifold and exhaust...

[tsi1991awd]

Would it be a bad idea to get an aftermarket exhaust manifold, downpipe, and full exhaust if I'm not wanting to heavily mod the car? And will it affect the backpressure negatively?

I bought my 91 TSI AWD from a mechanic and he said he wouldn't put an exhaust on the car because it will mess with the backpressure. I am wanting just a bit more power and my exhaust manifold has a couple of small cracks in it. That's why I ask about the aftermarket manifolds.

What type of manifold would be good?

 

[All_Boost16G]

N/A car need alitle back pressure. Turbo cars on the other hand, love free flowing from the turbo back. If you don want to heavily mod the car, i would remover the exshuast manifold and the O2 housing, and just port them alittle. There are quite a few write ups on how to port, and it is a very cheap mod, if you have some time. Dsm's have a very restrictive exshust. So added a 3in or even a 2.5 downpipe and catback, will greatly increase power, and spool. You will defintally feel the difference. There are quite a few companies that make decent priced downpipes. I know punishmentracing makes a true 3 in downpipe, and catback systems are endless, just depends on what you want to spend.

 

[tsi1991awd]

So you say I shouldn't replace the turbo manifold? Only the downpipe and exhaust?

There are a couple cracks in the manifold like I said...smoke came out of them when I seafoamed...

 

[shawnmr]

on turbo you dont need back pressure

 

[1gDSM4g63]

Replace the manifold for a ported 2g manifold.

 

[All_Boost16G]

Sorry I missed the cracked manifold, I personally would try to find another stock 2 manifold and port it, they are cheap. But if you would like to spend some money, I would look into a Forced Performance cast manifold. They flow awsome and look awsome. Becareful with some of you ebay manifold and pacesetter manfolds, they will tend to crack due to no support for a heavy turbo and a weak metal.

 

[xdxoxuxgx]

You can get the 2g manifold and a turbo back exhaust, these are light modifications, but you will notice the difference. And you should be able to get them for under $1k.

 

[tsi1991awd]

So I take it the 2g flows better? And would I still port it? Also, it is direct bolt on...I wouldn't have to get a different turbo or anything right?

Also, if I got a 3 inch downpipe and 3 inch exhaust and the manifold do I need to tune it or will it be fine?

 

[pj91gsx]

So I take it the 2g flows better? And would I still port it? Also, it is direct bolt on...I wouldn't have to get a different turbo or anything right?

Also, if I got a 3 inch downpipe and 3 inch exhaust and the manifold do I need to tune it or will it be fine?

no need to tune, but it is likely that you will have boost spike because of no back pressure, you can mod the wastegate to fix that. 2g manifold are less prone to crack.

 

[All_Boost16G]

2g's flow btter and are less likely to crack, you do not have to port, but its a cheap and easy mod to do if the manifold is off, the 2g manifold will bolt right up to the turbo you have, same with the o2 housing. I would also suggest porting this to while its off, but you don't have to port either the manifold or the o2 housing if you don't want to. Also you will not need any tune for the a downpipe and catback.

 

[All_Boost16G]

no need to tune, but it is likely that you will have boost spike because of no back pressure, you can mod the wastegate to fix that. 2g manifold are less prone to crack.

Also with porting the o2 housing should help eleminate the boost creep.

 

[tsi1991awd]

What would have to be done to the wastegate to eliminate the boost spike.....and is boost spike and creep the same thing?

 

[MrBoxx]

Boost spike is when boost rapidly rises to a point above your desired pressure, then settles back down. Boost creep is when you hit your desired pressure, and then boost slowly rises above that with no signs of stopping.

For 12psi desired boost pressure, examples as follows.
Spike: 5psi-8psi-10psi-18psi-12psi-12psi-12psi

Creep: 5psi-8psi-10psi-12psi-12psi-13psi-14-psi-15psi-etc.

Porting the turbine housing inlet will help take care of boost creep, which is notorious on the TDO5 turbos. You'll have to port a smoother, larger path to the wastegate inlet, instead of the 90* turn that the exhaust has to currently take to get out of the turbine housing. Porting the O2 housing a little larger may help. A Peepers-mod wastegate actuator has been shown to help with boost creep also, and should help eliminate spike. The Peepers-Mod WGA article. Please note that attempting to modify the wastegate actuator like Matt's method is in no way a task for a beginner. If you have doubts, contact him for more info, or resort to one of the other options that he outlines in his article.

If you have an automatic 1g, you have a TD04 13g stock, so the 2g manifold won't bolt up correctly. If you have a 14b, then you're good to go.

 

[pj91gsx]

Also with porting the o2 housing should help eleminate the boost creep.

yea. but the spike will most likely still be there, I ported the manifold turbo and o2 housing, and it still spiked. btw, is boost creep different than boost spike or are they the same thing?

 

[tsi1991awd]

I have a 5 speed 1g. Would I really need to do the porting? Does it hurt anything if I don't?

 

[MrBoxx]

yea. but the spike will most likely still be there, I ported the manifold turbo and o2 housing, and it still spiked. btw, is boost creep different than boost spike or are they the same thing?

See my post above for the difference.

Would I really need to do the porting? Does it hurt anything if I don't?

Do you really need to? No, but like most people mentioned, you may experience boost creep or boost spike, which, if you don't have the supporting fuel mods, may cause you to run into a lean condition, detonation, knock, fuel cut, etc. And those things WILL hurt things. It's best just to do the porting while you have the turbo, mani, and O2 housing off the car in the first place.

 

[tsi1991awd]

So if I do a downpipe and exhaust, pretty much I'd have to do the porting....

But do I have to modify the wastegate like that link? Because I don't think I'll be able to do that.


Edit: Would this be a good manifold to get? eBay Motors: MITSUBISHI DSM 1G 2G 4G63 GST GSX PORTED TURBO MANIFOLD (item 120313143362 end time Oct-09-08 21:54:40 PDT)


And O2 housing?

eBay Motors: DSM PORTED EXTERNAL O2 DUMP HOUSING Talon Eclipse 1g 2g (item 260294863284 end time Oct-08-08 19:12:34 PDT)

 

[MrBoxx]

The manifold looks decent; no cracks, already ported.

The O2 housing... honestly, you're not going to want to dump an internally gated turbo. It may be cool to hear that sound, but after a while, you're going to hate it. Anyone who's driving next to you is going to hate it. Your neighbors will hate it. It's best to stay with a recirculated O2 housing if you can. If you like the looks of that O2 housing though, I'd check out Punishment Racing's selection. I currently run his O2 housing (recirc'd) and it's pretty amazing. The welds are awesome and he guarantees his products for life. He also runs pretty good sales on his products from time to time.

You don't have to modify the wastegate actuator like MrPeepers. If you needed to stay with an internally gated turbo and were boost creeping like mad regardless of porting or exhaust routing, then that's one option. If you don't creep, then nothing needs to be done. But porting is generally recommended regardless.

 

[tsi1991awd]

The manifold looks decent; no cracks, already ported.

The O2 housing... honestly, you're not going to want to dump an internally gated turbo. It may be cool to hear that sound, but after a while, you're going to hate it. Anyone who's driving next to you is going to hate it. Your neighbors will hate it. It's best to stay with a recirculated O2 housing if you can. If you like the looks of that O2 housing though, I'd check out Punishment Racing's selection. I currently run his O2 housing (recirc'd) and it's pretty amazing. The welds are awesome and he guarantees his products for life. He also runs pretty good sales on his products from time to time.

You don't have to modify the wastegate actuator like MrPeepers. If you needed to stay with an internally gated turbo and were boost creeping like mad regardless of porting or exhaust routing, then that's one option. If you don't creep, then nothing needs to be done. But porting is generally recommended regardless.

So that manifold is basically all I would need? Since it's already ported and all....and I bolt my turbo and everything up to it and that's it?

And on the O2 housing, what would be bad about dumping it?

Also, would this be the recirculated one? eBay Motors: DSM PORTED INTERNAL O2 DUMP HOUSING Talon Eclipse 1g 2g (item 250303448222 end time Oct-09-08 21:23:07 PDT)


Does the lower part of the manifold need to be ported too? The part that the turbo bolts up to....or only the upper portion of the manifold and the O2 housing?

 

[fulanititoo8198]

Yes you wouldn't need to do anything to that 2g manifold it's already ported and it will bolt up. The vented o2 housing is personal preference it only opens when you hit the desired boost level so it only gets annoying if you let it. I personally like the sound, but that's just me. With some cheap o2 housings they aren't routed ideally and can heat your engine bay up. Other than that I would recommend going with name brand parts not ebay for reliability sakes. The 2g manifold is usually only ported at the collector not the runners and the o2 housing can be ported as well. Search around.

 

[tsi1991awd]

So I can just bolt up the bottom portion of my manifold to that ported 2g and not worry about anything else besides the O2 housing? Also, I know cheap ebay parts are usually no good...I was just kind of using those as reference. I would probably go with the Punishment Racing one.

Does the cat still bolt up to the downpipe or would I need to get a different one...or is it eliminated?

 

[fulanititoo8198]

So I can just bolt up the bottom portion of my manifold to that ported 2g and not worry about anything else besides the O2 housing? Also, I know cheap ebay parts are usually no good...I was just kind of using those as reference. I would probably go with the Punishment Racing one.

Does the cat still bolt up to the downpipe or would I need to get a different one...or is it eliminated?

Seems like your a little confused on the manifolds. The exhaust manifold you have now you fully replace with a 2g exhaust manifold or which ever one you choose to buy. That connects to the turbine side of the turbo. The turbo's exhaust and wastegate exit into the the o2 housing which hooks to your downpipe. Whether or not that o2 housing fits your stock downpipe depends on which one, but most do work with it just check with them before ordering.

 

[tsi1991awd]

Oh....well the link I posted to the ported 2g manifold only has the upper portion, there's nowhere to connect the turbo, that's why I was confused. I guess I have to find that lower portion then......would that need to be ported too, or left alone?


Edit: would the EVO 3 manifold be a good choice if it were ported as well? Also, the part where the turbo connects...I guess you call it the turbine housing...do I need to change that or just leave it? That is the part I am confused about. Changing the manifold part and the O2 housing are no problem

 

[MrBoxx]

The turbine housing is part of the turbo. That bolts to the manifold with 4 bolts. While it's off the manifold, remove the turbine housing from the turbo center section and port it, or have it ported. Check VFAQ Site - Visual Frequently Answered Questions on how to port a turbine housing. There are also several threads and articles here on porting.

The O2 sensor bolts to the side of the turbine housing with 4 bolts (or studs, or combination of bolts and studs) If you're getting that tubular O2 housing, you won't need to port it.

An Evo3 manifold would be fine, ported or unported. Even a 2g manifold unported would be fine for you.

 

[tsi1991awd]

I purchased an EVO 3 manifold that has been ported. Got a good deal on it, I think.

So after I port the turbine housing and put the O2 housing on, everything will bolt up to a PR 3" downpipe, right?

Also, will the cat still bolt up to the DP or is it eliminated?