I see a lot of threads asking about running an aftermarket downpipe and test pipe with stock catback.I know this is bad because it causes bottlenecks in the exhaust and pretty much chokes it, but I couldnt find any about running stock downpipe with aftermarket test pipe and catback. Will this be alright to do or is it a bad idea since the stock downpipe piping is much smaller than 3".

I have a catback installed already and my test pipe just came in. Would it be alright to just tune it with stock downpipe? What kind of gains will i see? How much more power will i see with an aftermarket downpipe?

Mods will be:
WORKS drop in filter
Hallman Pro Boost Controller
Walbro 255 Fuel Pump
Buschur Magnaflow Catback
MAP test pipe

 

With the test pipe installed...you might see about 10-15 hp with your mods and a tune.

Many evos have stock cats and aftermarket exhaust everything else.....you can go about your exhaust many different ways and combos but the best gains are seen with a full tbe system with high flow cat or test pipe...

 

Woah, really? I thought with just a tune you gain at least 20hp? or did you mean just with the test pipe because I heard test pipes gain like 10hp with a tune?
At the moment car is still on stock tune, all it has is a drop in filter and catback exhaust.

 

There is a ton of variables that come to play when measuring gains from hp/tq (elevation, mods, temp..)

But yea your kinda correct, you will see about ~ 20hp from just a tune and ~10hp on top of that from a tp.

 

So there is really no gains from the catback or drop in filter? Just the tune and test pipe?
How much extra hp will a downpipe add?
Oh yea im on 91 octane also how high should I up the boost for daily driving?

 

IMO, you can't just go "oh a tune add 20hp and a TP adds 10hp, etc etc.". It how the whole setup works together that makes your power, not just one part.

It would be best for you to get a full turboback exhaust with test pipe, a boost controller (MBC or 3port) and a tune. With those two parts and a tune, you will be at 300hp in VD, give or take 10hp. A stock EVO 8 does about 240-250hp in VD.

If you have a TBE w/ test pipe and tuning, you should be able to boost about 25psi, tapering to 20-22. If you use a cat instead of a test pipe, then I would recommend 23-24psi, tapering to 20.

Also, instead of a WORKS drop-in filter, you should get an OMG filter from Speed Element or GST. It will bolt right onto the MAF and help you hold boost and get better flow up top. If your worried about being stealth, then do the hack airbox mod to hide the filter.

 

Well I already have an MBC, test pipe and catback, and the WORKS filter, my mod list is on the first post, so I guess I have to pass on the OMG filter for now since im kind of on a budget :/ Im going to hold off on the tune then so I can get a downpipe for a turboback system, and hopefully hit 300hp

So with the testpipe, 25 psi is safe and reliable on 91 octane for every day driving? I just want to make sure because this is my only car and I drive it everyday lol

 

Cool. BTW, the OMG filter is only $45

Yeah, save for a DP, then do a tune.

Yes, if you have a test pipe and a good tune, 25psi is safe and reliable for daily driving.

 

Oh really? Im might have to get my hands on one then

Thank you for all the help! I really apappreciate it!
And sorry for so many questions, but this is the last one! lol

I wanted to get a buschur downpipe to go along with my MAP testpipe and buschur catback, but I noticed the Megan racing downpipe is around $150 and the buschur downpipe is $289. Are they really that different or is a 3" downpipe just a 3"downpipe? Is it ok if I mix different exhaust brands like that?