Downpipes vs. Full Exhaust

[Never thought]

So I dont know much about exhausts, as this is the first car I am looking at potentially swapping it out. My main concern is drone, so right now the only exhaust option that appeals to me is the Jun BL EVC exhaust since I can quiet it down at will, or making it loud, which is super appealing. But it is fairly pricey (probably $2K at least with shipping).

I then started reading a little about downpipes but havent found a ton. JUN BL claims a 30HP increase, which I find hard to believe (usually 10 is a lot). But assuming the 30HP increase is true, and I went with just the Jun BL downpipes (which are about $400), would I see the full performance gain of getting a full exhaust? Would it be louder than stock?

I also saw that the Jun BL downpipes delete the secondary catalytic converter. I am assuming this will mean I wont be able to pass emissions, is that right? If so, are there any downpipes that wouldnt impact emissions (same with after market exhausts)?

 

[xot1]

Most non-EVC exhaust mods won't probably pass emission tests.

 

[DaJackson]

Generally on turbo cars you will see more gains with a quality down pipe than you will with a cat back. Stock downpipes are generally very restrictive.

30hp may not be crazy depending on what the stock design vs Jun BL’s design is.

 

[Kamauxx]

I wish I could buy stuff like this from Amazon or Walmart so i could just return it if I didn't like it.

One of the vendors said there would be no change in sound or performance by changing the down pipe alone. Of course he's trying to sell complete exhaust systems to take that for what it's worth .

 

[DaJackson]

There is likely to be little change in sound with just a downpipe. Unless you go with a non-catted DP your essentially just smoothing out the airflow from the turbos to the mufflers. The muffler end is where you will see noticeable changes in sound. I’d guess Downpipes would be about 10% of the sound change on a full turbo back exhaust.

However I would guess that the DP makes up 70% of the performance change of a full TBE. All of this varies some depending on how the stock system is built vs what the aftermarket option is.

 

[ballistic]

me personally i would definitely do downpipes if i'm adding boost. i don't know for sure if there's going to be a noticeable about of increased drone inside the car. probably not. but gaining an extra 30hp is definitely possible. when you see people say 10hp from exhaust it's most likely only catback.

 

[Kazz]

I'm not sure you can get the 30hp from downpipes alone. I'd check with the part mfr. Is that after I've already replaced the exhaust?

 

[Kia Stinger]

I'm not sure you can get the 30hp from downpipes alone. I'd check with the part mfr. Is that after I've already replaced the exhaust?

I think that 30 horsepower potential is without anything holding back air flow - so after the rest of the exhaust was opened up, there'd be a 30 horsepower potential gain...

 

[Kamauxx]

There is likely to be little change in sound with just a downpipe. Unless you go with a non-catted DP your essentially just smoothing out the airflow from the turbos to the mufflers. The muffler end is where you will see noticeable changes in sound. I’d guess Downpipes would be about 10% of the sound change on a full turbo back exhaust.

However I would guess that the DP makes up 70% of the performance change of a full TBE. All of this varies some depending on how the stock system is built vs what the aftermarket option is.

These particular down pipes do on fact delete the cats though, right?

So is it safe to say an increase in sound is to be had?

Anyone want to buy a set of used down pipes if I install them and don't like em?

 

[Never thought]

So I realized the Jun BL is catback exhaust, so it does not include downpipes but they show a 30HP increase. There is nothing to show what the HP gain is for the Jun BL downpipes.

 

[xot1]

me personally i would definitely do downpipes if i'm adding boost. i don't know for sure if there's going to be a noticeable about of increased drone inside the car. probably not. but gaining an extra 30hp is definitely possible. when you see people say 10hp from exhaust it's most likely only catback.

I tried changed the exhaust to a louder one (no downpipe), but removed it after 2 weeks because of the drone. I don't know if all exhausts are like that but it was quite annoying.

 

[Never thought]

I tried changed the exhaust to a louder one (no downpipe), but removed it after 2 weeks because of the drone. I don't know if all exhausts are like that but it was quite annoying.

That’s my fear

 

[Never thought]

I tried changed the exhaust to a louder one (no downpipe), but removed it after 2 weeks because of the drone. I don't know if all exhausts are like that but it was quite annoying.

Was that exhaust for the Stinger? If so, what did you get?

 

[xot1]

Was that exhaust for the Stinger? If so, what did you get?

I got the GT type (non-EVC) from Jun BL and I don't intend to bash the product, which I think is fine.
Anyway, it was supposed to be one of the most drone-free of all models. But still...
When driving in city or when driving aggressively, the sound was really good and almost no drone.
But when cruising on the highway just around the speed limit, this is when the drone was the worst (around 2k~2.5k RPM). Of course I could avoid that RPM range but by doing so, I was forced to drive a bit slower than the speed limit (=than the traffic). What I didn't like most is that when I was trying to pass someone, normally it is super easy, a little more gas and the car passes everyone, right? But with the exhaust, a little more gas means you enter that specific RPM range and cabin noise gets super loud, the car vibrates... (Giving it more gas to go over 3k RPM and within seconds you're over 120mph which is not always the purpose). So whenever I wanted to go a little bit faster, it felt like the car was struggling, which ironically made the car feel slower to me (when cruising).
When driving aggressively, no complain, but I'm not street racing everyday to go to work or to the supermarket...
Maybe all exhaust mods are like that and I wasn't aware of it, but for me (and my girlfriend) it had more cons than pros. My friends, however, thought it was super good. But at the end of the day, I'm the one driving so after 2 weeks of trying to get used to it, I reverted to the stock exhaust.
I think it depends on people's taste, expectation and sensitivity. It is not for everyone and if you are not familiar with exhaust modifications, I would recommend trying the exhaust on another car first before making a decision.

The cold start sound was badass though.

 

[DaJackson]

These particular down pipes do on fact delete the cats though, right?

So is it safe to say an increase in sound is to be had?

If they delete the cats then yes you should have an increase in sound. I don’t know how restrictive the stock exhaust is so I can’t speak to how much but I would guess it would be slightly less than the increase if you just swapped the axle back.

 

[Never thought]

I got the GT type (non-EVC) from Jun BL and I don't intend to bash the product, which I think is fine.
Anyway, it was supposed to be one of the most drone-free of all models. But still...
When driving in city or when driving aggressively, the sound was really good and almost no drone.
But when cruising on the highway just around the speed limit, this is when the drone was the worst (around 2k~2.5k RPM). Of course I could avoid that RPM range but by doing so, I was forced to drive a bit slower than the speed limit (=than the traffic). What I didn't like most is that when I was trying to pass someone, normally it is super easy, a little more gas and the car passes everyone, right? But with the exhaust, a little more gas means you enter that specific RPM range and cabin noise gets super loud, the car vibrates... (Giving it more gas to go over 3k RPM and within seconds you're over 120mph which is not always the purpose). So whenever I wanted to go a little bit faster, it felt like the car was struggling, which ironically made the car feel slower to me (when cruising).
When driving aggressively, no complain, but I'm not street racing everyday to go to work or to the supermarket...
Maybe all exhaust mods are like that and I wasn't aware of it, but for me (and my girlfriend) it had more cons than pros. My friends, however, thought it was super good. But at the end of the day, I'm the one driving so after 2 weeks of trying to get used to it, I reverted to the stock exhaust.
I think it depends on people's taste, expectation and sensitivity. It is not for everyone and if you are not familiar with exhaust modifications, I would recommend trying the exhaust on another car first before making a decision.

The cold start sound was badass though.

Good to know and thank you! This is the exact reason I am only considering the EVC or downpipes. With the EVC I can quiet it down as needed.

 

[xot1]

Good to know and thank you! This is the exact reason I am only considering the EVC or downpipes. With the EVC I can quiet it down as needed.

EVC is surely more convenient!
But I wish there was an exhaust that sounds good without drone when cruising, not only when driving like a madman.

 

[TuscaniCustoms]

So I dont know much about exhausts, as this is the first car I am looking at potentially swapping it out. My main concern is drone, so right now the only exhaust option that appeals to me is the Jun BL EVC exhaust since I can quiet it down at will, or making it loud, which is super appealing. But it is fairly pricey (probably $2K at least with shipping).

I then started reading a little about downpipes but havent found a ton. JUN BL claims a 30HP increase, which I find hard to believe (usually 10 is a lot). But assuming the 30HP increase is true, and I went with just the Jun BL downpipes (which are about $400), would I see the full performance gain of getting a full exhaust? Would it be louder than stock?

I also saw that the Jun BL downpipes delete the secondary catalytic converter. I am assuming this will mean I wont be able to pass emissions, is that right? If so, are there any downpipes that wouldnt impact emissions (same with after market exhausts)?

If you don't want cabin drone EVC is the only option, either buy exhaust that already has this (easier and cheaper than buying it later plus modify exhaust to install it) or buy non evc exhaust and EVC valve later. Most aftermarket performance exhausts have drone as if they wouldn't they wouldn't be performance exhausts but same as stock so there would be no point right?

Down pipes alone sure won't give you +30hp, I don't think even whole exhaust system would give you that much, could be wrong but I think I'm not. You just have to be realistic and not believe all claims about hp and torque increase my by exhaust and intake manufacturers.
If you want down pipes with cats then german bastuck is the only option right one but prices are just crazy Bastuck 3.3 T-GDI V6 Exhaust kia stinger

If you get jun bl downpipes exhaust will be louder but it won't give you much power so if you want to get more power you should ad full catback exhaust. If you eliminate one restriction only (stock downpipes) you are left with another restriction or bottle neck if you want and that is stock exhaust so you haven't really achieved much.
It might sound like me or some other vendor trying to sell more but you can try and see for yourself. I installed only full catback first on my car and I couldn't say I gained any power, maybe a few hp and it sounded barley a bit louder than stock (tiburon bastuck exhaust) but then I added maintec headers and magnaflow 200cel cat and car got a lot louder and power gain was noticeable.
With power also came cabin drone which was annoying when driving at high rpm on highway so I had to add cut off valve (EVC valve from QTP performance) as there are no EVC exhausts for tiburons. Now it's great, max power and sound control whenever I want at a push of a button on remote

 

[Kamauxx]

If you don't want cabin drone EVC is the only option, either buy exhaust that already has this (easier and cheaper than buying it later plus modify exhaust to install it) or buy non evc exhaust and EVC valve later. Most aftermarket performance exhausts have drone as if they wouldn't they wouldn't be performance exhausts but same as stock so there would be no point right?

This isn't true. I've owned modified exhausts on a GTO, Corvette, and 3 Camaros.

The only time I ever had any drone was when I put dynomax "mufflers" on a Camaro, and dumped them in front of the rear axle.

With a good setup drone can be avoided. A good muffler, H-pipe, X-pipe, resonators, location of parts within the system all have an impact on the frequency needed to hit the drone's sweet spot.

 

[xot1]

This isn't true. I've owned modified exhausts on a GTO, Corvette, and 3 Camaros.

The only time I ever had any drone was when I put dynomax "mufflers" on a Camaro, and dumped them in front of the rear axle.

With a good setup drone can be avoided. A good muffler, H-pipe, X-pipe, location of parts within the system all have an impact on the frequency needed to hit the drone's sweet spot.

Camaro is naturally aspirated.
I heard it is much harder to avoid drone with the stinger's (twin) turbo charged engine.