Exhaust flow/horsepower?

[CyFi6]

Well currently my car has the following mods...
7MGTE
2.5" intercooler piping/larger intercooler
57 trim CT26
3" downpipe
Gutted cat
2.5" cat back
MaftPro tuning - 15PSI boost
Fuel upgrades

My question is concerning the exhaust... I am wondering if the 2.5" catback is really costing me any horsepower, and if it is, is it anything noticeable? At what point is a 3" exhaust really necessary, or when does anything smaller really become a restriction? I am happy with the exhaust I have now/the sound and not sure if it is worth spending $500+ to step up from a 2.5" to 3". Any insight would be great.

 

[IBoughtASupra]

With that PSI and upgraded turbo, a three inch should be put in by now.

 

[bioskyline]

3 inch all the way. turbo engines are differnt from N/A cars. excess backpressue tends to slow down the turbine, reducing the turbos response time.

half an inch is alot. going to a full 3 inch you will notice spool is faster, reducing turbo lag, and gaining more hp on the butt dyno.

 

[spikesnstuff0905]

You don't need to worry about backpressure, because you will always have something between your block and the end of your exhaust. It's a turbo. The turbine will provide all the backpressure you need until boost kicks in, and going 3" will give you a prominently quicker spool time.

 

[Inygknok]

Emission tests, on the other hand, might want you to keep your cat, even if just a high flow one. Depending where you live of course.

Also, you could visit a muffler shop and have the exhaust made for your car in 3". Way cheaper than a brand-name exhaust and it works just fine.

 

[IBoughtASupra]

What you can do is have a test pipe made and have another test pipe but with a cat on it. Use a California Emission cat since that should pass in any state.

 

[CyFi6]

I figured as much, was just wondering if there was any actual proof that a 2.5" was restrictive at this point. Not too worried about emissions, as I have all the emissions devices on hand. I have thought about having an exhaust shop make a 3 inch exhaust, but considering that they don't do mandrel bents it doesnt seem to be a very good option.

 

[gurley0916]

I used to have a 2.5 catback with a 3 inch down pipe and going to the 3inch made a pretty decent power gain. You dont find the car feeling choked on top end especially. You dont need to spend 500+ on an exhaust. We have people locally like steven and albert who have done exhaust work. Just buy the materials and Im sure they can help out.

 

[dubsupra209]

3in exhaust wont cost 500 buy a muffler which could be anywhere from 100-250 (used/new) and exhaust pipping is about $70 from downpipe back then should only cost no more then 100 (cost me $60) to have exhaust bent and mounted so your looking at more like 350..selling my used apexi n1 for 100 lmk if your interested

 

[GrimJack]

If you're happy with the setup you have now, consider pulling out the dead cat and putting in a bypass. Then, when you want the extra performance, you simply flip the switch and the bypass opens right there.

If you have smog tests where you live - which sounds doubtful, considering you're running with a dead cat now - have the bypass put in with VBands, and get a cat setup to bolt into the same location when you need to pass smog.

 

[Blackdawg]

Or you could get a QTP exhaust cutout haha

but 3'' exhaust isnt bad at all. DMs kit is like 350. i have read its a huge difference. and in my friends stock 7mgte it made a massive difference.

 

[OfnaRcR4]

I'm a cucumber.. And 3 inch.

 

[SC61 MK3]

you could take off the 2.5" exhaust and run open downpipe for testing purposes to see if the gains from a better flowing exhaust are worth the $

 

[shaeff]

you could take off the 2.5" exhaust and run open downpipe for testing purposes to see if the gains from a better flowing exhaust are worth the $

I used to run a RS*R Concept cat-back. It had the resonator deleted, and was pretty much as straight through as they come. It sounded *amazing*, but the canister was just too big for my liking. When I went to the dyno several years back, I removed the exhaust and drove down open downpipe. Even the difference from a 3" exhaust to open downpipe (which happened to be a BIC DDP) was noticeable. Going from 2.5" cat-back to open 3" downpipe will make a huge difference.

I <3 open downpipe.