Exhaust Flow question 2.5 inch with cutout vs 3 inch?

[4gfun]

So my intermediate pipe ripped in a perfect place to attach a cutout. I don't care about noise, so I wanted to put a cutout between the cat and the muffler as a clamped cutout makes a very cost effective solution in this case. The existing cat is a hi flow catco and the muffler is a magnaflow. The existing exhaust size is 2.5"

How much less power will I make with this setup as opposed to a 3" setup with a muffler? (mind you either would be catted)

I can't imagine there would be a huge difference if any. I ask because I read that a 20g at higher boost is a no no with a 2.5 inch exhaust. This is why I went with an E316g but want to know if a 2.5 inch catted exhaust with a cutout would work out fine with a 20g at higher boost or not.

Thanks

 

[4gfun]

Edited my post- I meant to say use a 2g AWD DP with a 1g AWD catback. Sorry about the confusion

The downpipes are a direct bolt in. If you use a 1g DP it will bolt directly to your factory cat in it's factory location, it's the 1g AWD catback that isn't quite long enough to make it to the rear.

If I remember correctly, the 2g catback is long enough that it will add on your 2" (or whatever amount it was, can't remember off the top of my head) and take up where your cat was. If I remember correctly the 2g DP paired with a 1g catback had the perfect length to run a full turboback exhaust. If it needs extended at all you could always buy a small 3" test pipe and have that bolted inbetween to give you the added length you need.

Upon further investigation (and finding your thread on the .org) you'd need 12" test pipe, not a 2". If I had a damn 2g awd downpipe I'd throw it on my galant to test fit with my 1g catback. Unfortunately all I have currently is a fwd DP which won't even come close to working.

This is making for a good read. Thanks for the info...don't want you to kill yourself test fitting stuff though.

EDIT: Thanks for the additional info...reading that too. Creative with the exhaust hangers....no problem...half are missing/broken/modified/etc

So what's your take on the whole cutout deal with my setup? Looking back a few years, looks like someone has run high 11's on an e316g with a Buschur 2.5" catback.

 

[lauj2gdsm]

2 1 2 inch 2 5 inch Electric Exhaust Dumps Cut Out Pick Up 20HP | eBay

get this. half these guys are talking nonsense.. use it when you need close it when you are driving around town.. should flow enough for anything you have now and in the future. weld it before your cat. you car future is in your hands.

 

[Tyeler18]

This is making for a good read. Thanks for the info...don't want you to kill yourself test fitting stuff though.

EDIT: Thanks for the additional info...reading that too. Creative with the exhaust hangers....no problem...half are missing/broken/modified/etc

So what's your take on the whole cutout deal with my setup? Looking back a few years, looks like someone has run high 11's on an e316g with a Buschur 2.5" catback.

I personally planned on running a 2.5-3" cutout on the stock catback on my galant. Still haven't decided for sure if that's what I want or not. I'm trying to retain a stock appearance since I use it as my DD, while still having the performance of my 1g when I want it.

A 2.5" on a 16g isn't going to make that much bigger of a difference when compared to a 3" until you're actually pushing the limits of the turbo. I've run a full 3" ending at a 5" straight pipe exhaust on an evo 3 16g and saw spool times that averaged slightly slower than a s16g on a 2.5" turbo back. Both were run in the low 20psi and honestly I don't think I would've seen much of a difference going to a 3" on the s16g.

 

[4gfun]

2 1 2 inch 2 5 inch Electric Exhaust Dumps Cut Out Pick Up 20HP | eBay

get this. half these guys are talking nonsense.. use it when you need close it when you are driving around town.. should flow enough for anything you have now and in the future. weld it before your cat. you car future is in your hands.

Taken under advisement except...

1) Would clamp not weld....U-clamps are included with the manual cutout...if they leak so what
2) After the cat since the Catco is probably only killing 2hp over a test pipe...so no emissions violations when pulled over only noise
3) Would leave wide open since I hardly ever drive the car and would be muffled by the car

Yes master, it's future is in my hands!

Thanks

I personally planned on running a 2.5-3" cutout on the stock catback on my galant. Still haven't decided for sure if that's what I want or not. I'm trying to retain a stock appearance since I use it as my DD, while still having the performance of my 1g when I want it.

A 2.5" on a 16g isn't going to make that much bigger of a difference when compared to a 3" until you're actually pushing the limits of the turbo. I've run a full 3" ending at a 5" straight pipe exhaust on an evo 3 16g and saw spool times that averaged slightly slower than a s16g on a 2.5" turbo back. Both were run in the low 20psi and honestly I don't think I would've seen much of a difference going to a 3" on the s16g.

See that's the thing, I plan on pushing the limits of the turbo e.g. 25 psi. Now they have removed the E85 gas station around here so my limits are better defined. That is the only positive about it I guess. The s16g was what I had on there before. Previous owner told me it was a b16g. Had I known it was a s16g I wouldn't have boosted it to 25 psi so much. A s16g is a wonderful turbo. All things considered, I'd stick with that if I were you! Just slightly less flow than an E316g. Now a cutout with your stock exhaust would be a totally different animal. I have a feeling we will be trading parts soon.

 

[Tyeler18]

Taken under advisement except...

1) Would clamp not weld....U-clamps are included with the manual cutout...if they leak so what
2) After the cat since the Catco is probably only killing 2hp over a test pipe...so no emissions violations when pulled over only noise
3) Would leave wide open since I hardly ever drive the car and would be muffled by the car

Yes master, it's future is in my hands!

Thanks



See that's the thing, I plan on pushing the limits of the turbo e.g. 25 psi. Now they have removed the E85 gas station around here so my limits are better defined. That is the only positive about it I guess. The s16g was what I had on there before. Previous owner told me it was a b16g. Had I known it was a s16g I wouldn't have boosted it to 25 psi so much. A s16g is a wonderful turbo. All things considered, I'd stick with that if I were you! Just slightly less flow than an E316g. Now a cutout with your stock exhaust would be a totally different animal. I have a feeling we will be trading parts soon.

I actually run the s16g on one of my other dsms and yes it's a much better turbo in my opinion than any of the other 16g variants. Plus I only paid $100 for it brand spanking new, so that alone made it wonderful (machine shop didn't know what it was)

You may* suffer some running it post cat if you plan on flowing that much air, although I don't know exactly when the restriction is on 2.5". Like everyone else was saying, ideally you'd want to put it as close to the turbo as possible, but if anything you can put it on, run it with the cutout where you want and see how it spools, then drop the downpipe and see where it spools. Probably isn't going to be much of a noticeable difference, but that's the best way you could go about it.

 

[4gfun]

I actually run the s16g on one of my other dsms and yes it's a much better turbo in my opinion than any of the other 16g variants. Plus I only paid $100 for it brand spanking new, so that alone made it wonderful (machine shop didn't know what it was)

You may* suffer some running it post cat if you plan on flowing that much air, although I don't know exactly when the restriction is on 2.5". Like everyone else was saying, ideally you'd want to put it as close to the turbo as possible, but if anything you can put it on, run it with the cutout where you want and see how it spools, then drop the downpipe and see where it spools. Probably isn't going to be much of a noticeable difference, but that's the best way you could go about it.

Thanks, well cut the old damaged pipe out and put the cutout in it's place. Work of art for just U-clamps. The best part is that I can drive open cutout and still carry on a phone conversation since it is post cat and the cat muffles some of the sound.

I can't say what it has done for power since my car is way out of tune.

 

[4gfun]

Guys,

I need your help. Things didn't work out so well putting the cutout on my midpipe post cat.

The muffler ended up snapping off from the front (probably due to the setup being too rigid). Luckily it didn't come completely off the car.

With that said, I think I am going to try and get the cutout pre-cat.

Some of you say that a 2.5 inch cutout pre cat should flow just as good as a 3 inch exhaust.

I have to bring it to an exhaust shop tomorrow and was thinking of having them move the cutout closer to the turbo (if by chance they will do it which I seriously doubt)

Thanks

Ended up getting a shop to put it pre cat....

 

[Tyeler18]

How did it turn out pre-cat?

 

[4gfun]

How did it turn out pre-cat?

Thanks for asking!

Well....

1) Far too noisy. It sounded alot better post cat. I could carry on a phone conversation and the person on the other end never noticed. I never thought I'd say this in my life but 40 is fast approaching for me.

2) Also, I don't know if he put it in the "sweet spot". It is pre cat, but not all too far before the cat. I don't know if it needed to go right where the downpipe meets the turbo to be as good as 3" or what??

I am thinking of the electric cutout, but the other poster's post scares the heck out of me where he mentions it breaking all the time!

I will be getting a ticket with this thing in no time I assume.

 

[007jimmy]

I just bought a 3" e-cutout for my car and its plumbed right off my downpipe (right after the o2 housing). The rest of my exhaust is 2.5", no cat or resonators but a stock style muffler to control noise. Its great. Noise and performance when i want it and nice quiet daily driving around town.

No more teeth chattering full open exhaust. Since the cutout isnt under the middle of the car its not even that loud unless you really get on it.

 

[4gfun]

I just bought a 3" e-cutout for my car and its plumbed right off my downpipe (right after the o2 housing). The rest of my exhaust is 2.5", no cat or resonators but a stock style muffler to control noise. Its great. Noise and performance when i want it and nice quiet daily driving around town.

No more teeth chattering full open exhaust. Since the cutout isnt under the middle of the car its not even that loud unless you really get on it.

Which e-cutout did you get? Is clearance or heating up any component an issue? Come to think of it...since this is already done and finished...might as well convert it to a throttle body cutout myself.

Thanks