Cobb downpipe vs. Helix downpipe (review)

aspensti05 · 10-12-2005, 08:09 AM

I am posting this because I searched but could not find anyone comparing the two. Most of this is already talked about on the forums but it's not together in one post nor are they compared directly to one another. Since I've owned and used both maybe this can help someone out in the future.

First impressions/thoughts:

The Helix box opens lengthwise so it is very easy to get out. After opening you will see it is wrapped in bubble wrap and the hardware(gasket and bolts) is taped to the downpipe. There are no instructions, but you really don't need any. Remove the bubble wrap and you are treated to an entirely polished downpipe, worthy of hanging on the wall. The logo is welded to the side of the cat which is located right after the turbo in the vertical part of the pipe. The design of the downpipe apears to be "bling" first, engineering/performance second. The welds are good to great, but the taper(or lack of) of the cat, and location of the cat and O2 bung are not optimal.

The Cobb box opens at the end which means you have to pull it out. Not a big deal, but harder than the Helix. The Cobb downpipe has foam wrapped around the ends and the middle. There is no included hardware, because you reuse the factory spring bolts and donut gasket to mate with the stock or Cobb catback. The box did include a Cobb Tuning plastic license plate frame and an instruction sheet. Remove the foam wrap and it is a mix of quality and engineering. While this downpipe is not shiny and "bling," anyone who knows anything about exhausts will appreciate the welds, the cast bellmouth, the location of the O2 sensor bung and the design/location of the cat. It is a bit disappointing to pay this much and see raw stainless pipe much like you would at a muffler shop, but it is totally understandable because of the cost that went into the design/R&D and the cast bellouth. Plus you never see it once it is on the car, and if you wrapped either downpipe in heat wrap one wouldn't notice the polish or lack of. Cobb’s downpipe is a case of function first, form 2nd. Some people complain about the taper at the end of the Cobb downpipe. This is what Cobb has to say about it:

"Finally, the fact that we do allow a proper fitment of our downpipe to cat-back systems means there is a slight reduction in pipe diameter at this point. In order to reduce any performance robbing backpressure, we've custom built a smooth transition that is completely smooth and free of turbulence. While there are many downpipes performing this transition by simply welding a 3" pipe to a smaller flange -- creating massive turbulence and exhaust restriction -- our design has proven not to be a restriction in performance in applications up to 450 HP."

Considering they have way more experience and test equipment that I do, I am sure they know what they are doing/talking about. I never plan to see more than 300whp in my STi.

Installation:

The install of both is about the same, except a few minor differences worth noting:

The Helix requires moving of the drain tube as it will touch and melt it. The Cobb does not.

The Cobb exhaust needs to reuse the factory donut gasket to mate with the stock catback or Cobb catback. I can't speak for everyone but I had to do some cutting of the donut to get it to fit the end of the downpipe. I wasn't expecting that at all.

The O2 bung on the Cobb is right on top very easy to get to. The O2 bung on the Helix is on the drivers side under the intercooler. I didn't have to take off the intercooler to install either, but I'm not sure how easy it would be to access the bung with the Helix installed on the car. For me neither one is an issue at this point because I don't see using that feature anytime soon. This picture does a great job of showing three things:

1) exhaust flow
2) crushed/melted ac drain
3) location of O2 bung

This next diagram shows the Helix cat(poor) vs the Cobb cat(best) design:

In addition to the design of the flow before and after the cat, the Cobb as a performance advantage over the Helix because of actual location of the cat. The Cobb cat is all the way at the end of the downpipe right before the O2 sensor and the flange to mate up with the midpipe. The Helix cat is right after the turbo.

There is more info why one is better than the other at Cobbs site rather than quoting it here I will just link it:
http://www.cobbtuning.com/tech/exhaustdesign/

Sound/Performance:

It is worth mentioning a few things first. I've had four downpipes total, stock, Perrin catless(version 1), Helix catted and now finally Cobb catted. The Perrin catless sounded horrible. It was too loud(with the Perrin catback version 1 dual tips) and changed the sound from deep boxer rumble to a fart can sounding Honda.

The Helix catted was used with the Perrin catback (version 1 dual tips)and the Cobb used with the Cobb catback. So my impressions are with those setups vs one another.

The Helix downpipe sounded about the same as the stock downpipe with the Perrin catback. If anything is was slightly louder. Until the engine/cat warmed up it sounded raspy and during the first few minutes I shifted at 3500rpms or less because it sounded crappy. After that it mellowed out and sounded great! Also during the warm up the Helix didn't seem to flow as well, but thats ok because you shouldn't be getting on it until the engine and cat are warmed up anyways. The performance was slightly slower(seat of the pants) and turbo spool up was delayed slightly over the Perrin catless by a 200-300 rpms.

The Cobb downpipe doesn't seem to change in sound warmed up vs. cold. With the Cobb downpipe installed the turbo feels like it spools and moves air like it did with the Perrin catless. Compared to the Helix it spools a few hundred rpm earlier and faster. The entire Cobb turbo back is much quieter than the Helix downpipe and Perrin cat back combo. So much so that with the windows up it sounds only slightly louder than stock. But that is not my final observation. Due to all the rain here, I have not had the chance to hear it with the windows down, nor is the exhaust fully broken in yet. I will edit this post with my final thoughts. I do miss the sound of the Helix and Perrin combo at idle though.

Conclusion:

Both are great downpipes. The Helix is a better value costing about $225 less if each was purchased alone. The Cobb won't match up to many of the 3" catbacks out there without some work because of the way it tapers and uses the factory donut gasket. The Cobb is better designed, and appeared to have more engineering but I don't know that it adds enough power or decreased turbo lag to justify the price tag. If you want the highest quality downpipe with the most R&D behind it and price is not an object get the Cobb. Otherwise as it is already suggested lots around IWSTI go for the Helix. You can't go wrong with either.

T1mmmy · 10-12-2005, 08:16 AM

Great write up between the two! I was one of the few debating on either the Helix catted vs the Cobb catted, and because of my budget, i decided to go Helix.

However, imo, i dont think you give enough justice to the perrin TBE. My friend just recently installed his on a 2002 WRX, and i think it doesnt sound too bad at all.

However just my .02c .

I love my helix catted downpipe. I can hear a slight difference between the helix vs the stock when mated to the stock catback.

Tim

aspensti05 · 10-12-2005, 08:23 AM

Quote:

Originally Posted by T1mmmy

However, imo, i dont think you give enough justice to the perrin TBE. My friend just recently installed his on a 2002 WRX, and i think it doesnt sound too bad at all.

I noticed you used the word "recently."

If his Perrin TBE was purchased recently, there are some differences between your friends and mine. His has a resonator in the midpipe that mine does not have. His may also be the single tip version. Mine was the dual tip and Perrin has noted that the dual tip is louder than the single tip.

I don't know what other changes Perrin might have made, but they have said the newer version of their exhaust is quieter. That may be the reason, but I don't have any experience with that version. I will go back and edit my write up to note that I had version 1 with dual tips.

I can for a fact say my 2005 STi went from sounding like a deep and throaty boxer above 3500rpms with the stock downpipe and Perrin V1 dual tip cat back, to sounding like a fart can Honda above 3500rpms with the addition of the Perrin catless downpipe. It sounded awful to me and did not do the car any justice at all. This was my experience.

mx_9 · 10-12-2005, 10:36 AM

Nice writeup. Did you plug up the upper sensor bung or did you leave it as is? I left mine unplugged but saw one over the weekend that was plugged, so now I'm curious as to what others are doing.

aspensti05 · 10-12-2005, 10:39 AM

mx_9 no clue what you are talking about. The bung right after the turbo is to be used for a wideband O2 sensor for air/fuel readings during tuning. the bung right before the midpipe uses the factory rear O2 sensor. The factory primary O2 sensor is in the uppipe not the downpipe.

Please clarify which sensor you left unplugged.

mx_9 · 10-12-2005, 10:45 AM

Aspensti: I was referring to the tuning bung for the wideband 02 sensor. I left mine as I received it from Cobb, I believe as shown in the picture that you provided. The one I saw this weekend had a bolt screwed into it.

aspensti05 · 10-12-2005, 10:50 AM

The picture of the Cobb downpipe has the plug in it. This is how it should look/arrive from the factory. If there is no plug in it, and no sensor in it, then I would think your exhaust would be really loud and you would be letting hot exhaust gas out under your hood. This is a really bad idea.

This is how it should look:

JJ18Sniper · 10-12-2005, 11:21 AM

Are there people converting the cobb downpipe to a full 3" fitment for 3" catbacks? I've always liked the downpipe, but I am interested in a 3" catback... anyone with experience?

mx_9 · 10-12-2005, 11:38 AM

Quote:

Originally Posted by JJ18Sniper

Are there people converting the cobb downpipe to a full 3" fitment for 3" catbacks? I've always liked the downpipe, but I am interested in a 3" catback... anyone with experience?

No, but... I am about to add the Cobb catback to my Cobb DP. I am going to have a before and after dyno run since I am protuned (Ecutek) and am interested in what the A/F and boost will look like. I'll also get a chance to compare readings from a Dynojet (what I was tuned on) and a Mustang AWD (a local source for just dyno pulls). If you are interested I will PM you the gains (if any) that I see. (Understanding that my setup includes the 3.00" to 2.5" to 3.00" section, but is Cobb nonetheless)

***Neanderthal Racing*** · 10-12-2005, 11:39 AM

Cobb downpipe vs. Helix downpipe (review)

it's nice to see a product comparison based on actual experience rather than speculation. great job!

***KarlSTI*** · 10-12-2005, 11:40 AM

Quote:

Originally Posted by mx_9

No, but... I am about to add the Cobb catback to my Cobb DP. I am going to have a before and after dyno run since I am protuned (Ecutek) and am interested in what the A/F and boost will look like. I'll also get a chance to compare readings from a Dynojet (what I was tuned on) and a Mustang AWD (a local source for just dyno pulls). If you are interested I will PM you the gains (if any) that I see. (Understanding that my setup includes the 3.00" to 2.5" to 3.00" section, but is Cobb nonetheless)

I'm interested in see the gains too....can you post?

jgheels2003 · 10-12-2005, 11:45 AM

I used to run the Helix catted on both the stock turbo and Deadbolt 20g. After getting great results with both applications, I can't imagine paying another $200+ dollars for something that wouldn't offer any performance gains. If the placement of the Helix cat is so bad (APS for that matter too), do you realy think they wouldn't redesign the thing?

The Cobb is a ripoff. Not b/c its isn't great quality and doesn't work. It just cost a couple hundred more than something that works just as well and is equal in quality.

mx_9 · 10-12-2005, 11:45 AM

Quote:

Originally Posted by KarlSTI

I'm interested in see the gains too....can you post?

Sure. My dyno run is set for Monday. Just to clarify my previous comments: I'm currently tuned with just the DP and Ecutek. I decided to go the full TBE since the tuner said I was leaving some top end HP on the table with my stock catback. The tuner is in Atlanta, I'm in Raleigh. There is a local mustang awd dyno that I worked out a deal with to do a pull as-is, install the catback, and do two more pulls to see what the results are. There will be no additional tuning. Just the catback. I'll post the catback addition pulls.

aspensti05 · 10-12-2005, 11:53 AM

Quote:

Originally Posted by jgheels2003

The Cobb is a ripoff. Not b/c its isn't great quality and doesn't work. It just cost a couple hundred more than something that works just as well and is equal in quality.

Have you owned, touched, installed and driven with both?

I don't think the Helix is anywhere near the quality or engineering of the Cobb downpipe. Pretty polish does not equal quality.

That said, it's only a downpipe and it can only do so much. Is the Cobb over-engineered? Probably.
Will the Cobb out last the Helix, longer than you own the car, maybe even longer than the life of the car? Probably.
Could the Helix cat location cause it to break down faster or fail faster? Yes. Will it do that during the 50,000 to 100,000 we own our cars for, probably not.
Do we all race our cars and subject them to conditions outside normal operations? No, but some of us do.

Running a stock car around the track aggressively and continuously is much harder on the engine than running an upgraded turbo(assuming it is tuned properly)

Rdrcr · 10-12-2005, 11:53 AM

Quote:

Originally Posted by BruceChapman

Cobb downpipe vs. Helix downpipe (review)

it's nice to see a product comparison based on actual experience rather than speculation. great job!

Agreed!

Thanks for the write-up.

I just wish Cobb had a divorced wastegate like the Invidia V3. That would make my decision much more difficult.

Mike

10-12-2005, 08:09 AM	#1
aspensti05 Spec C Club Car: BMW M5 993 Turbo Location: Southwestern, CT Posts: 1,293 Join Date: Sep 2005 Trader Rating: (5)	Cobb downpipe vs. Helix downpipe (review) I am posting this because I searched but could not find anyone comparing the two. Most of this is already talked about on the forums but it's not together in one post nor are they compared directly to one another. Since I've owned and used both maybe this can help someone out in the future. First impressions/thoughts: The Helix box opens lengthwise so it is very easy to get out. After opening you will see it is wrapped in bubble wrap and the hardware(gasket and bolts) is taped to the downpipe. There are no instructions, but you really don't need any. Remove the bubble wrap and you are treated to an entirely polished downpipe, worthy of hanging on the wall. The logo is welded to the side of the cat which is located right after the turbo in the vertical part of the pipe. The design of the downpipe apears to be "bling" first, engineering/performance second. The welds are good to great, but the taper(or lack of) of the cat, and location of the cat and O2 bung are not optimal. The Cobb box opens at the end which means you have to pull it out. Not a big deal, but harder than the Helix. The Cobb downpipe has foam wrapped around the ends and the middle. There is no included hardware, because you reuse the factory spring bolts and donut gasket to mate with the stock or Cobb catback. The box did include a Cobb Tuning plastic license plate frame and an instruction sheet. Remove the foam wrap and it is a mix of quality and engineering. While this downpipe is not shiny and "bling," anyone who knows anything about exhausts will appreciate the welds, the cast bellmouth, the location of the O2 sensor bung and the design/location of the cat. It is a bit disappointing to pay this much and see raw stainless pipe much like you would at a muffler shop, but it is totally understandable because of the cost that went into the design/R&D and the cast bellouth. Plus you never see it once it is on the car, and if you wrapped either downpipe in heat wrap one wouldn't notice the polish or lack of. Cobb’s downpipe is a case of function first, form 2nd. Some people complain about the taper at the end of the Cobb downpipe. This is what Cobb has to say about it: "Finally, the fact that we do allow a proper fitment of our downpipe to cat-back systems means there is a slight reduction in pipe diameter at this point. In order to reduce any performance robbing backpressure, we've custom built a smooth transition that is completely smooth and free of turbulence. While there are many downpipes performing this transition by simply welding a 3" pipe to a smaller flange -- creating massive turbulence and exhaust restriction -- our design has proven not to be a restriction in performance in applications up to 450 HP." Considering they have way more experience and test equipment that I do, I am sure they know what they are doing/talking about. I never plan to see more than 300whp in my STi. Installation: The install of both is about the same, except a few minor differences worth noting: The Helix requires moving of the drain tube as it will touch and melt it. The Cobb does not. The Cobb exhaust needs to reuse the factory donut gasket to mate with the stock catback or Cobb catback. I can't speak for everyone but I had to do some cutting of the donut to get it to fit the end of the downpipe. I wasn't expecting that at all. The O2 bung on the Cobb is right on top very easy to get to. The O2 bung on the Helix is on the drivers side under the intercooler. I didn't have to take off the intercooler to install either, but I'm not sure how easy it would be to access the bung with the Helix installed on the car. For me neither one is an issue at this point because I don't see using that feature anytime soon. This picture does a great job of showing three things: 1) exhaust flow 2) crushed/melted ac drain 3) location of O2 bung This next diagram shows the Helix cat(poor) vs the Cobb cat(best) design: In addition to the design of the flow before and after the cat, the Cobb as a performance advantage over the Helix because of actual location of the cat. The Cobb cat is all the way at the end of the downpipe right before the O2 sensor and the flange to mate up with the midpipe. The Helix cat is right after the turbo. There is more info why one is better than the other at Cobbs site rather than quoting it here I will just link it: http://www.cobbtuning.com/tech/exhaustdesign/ Sound/Performance: It is worth mentioning a few things first. I've had four downpipes total, stock, Perrin catless(version 1), Helix catted and now finally Cobb catted. The Perrin catless sounded horrible. It was too loud(with the Perrin catback version 1 dual tips) and changed the sound from deep boxer rumble to a fart can sounding Honda. The Helix catted was used with the Perrin catback (version 1 dual tips)and the Cobb used with the Cobb catback. So my impressions are with those setups vs one another. The Helix downpipe sounded about the same as the stock downpipe with the Perrin catback. If anything is was slightly louder. Until the engine/cat warmed up it sounded raspy and during the first few minutes I shifted at 3500rpms or less because it sounded crappy. After that it mellowed out and sounded great! Also during the warm up the Helix didn't seem to flow as well, but thats ok because you shouldn't be getting on it until the engine and cat are warmed up anyways. The performance was slightly slower(seat of the pants) and turbo spool up was delayed slightly over the Perrin catless by a 200-300 rpms. The Cobb downpipe doesn't seem to change in sound warmed up vs. cold. With the Cobb downpipe installed the turbo feels like it spools and moves air like it did with the Perrin catless. Compared to the Helix it spools a few hundred rpm earlier and faster. The entire Cobb turbo back is much quieter than the Helix downpipe and Perrin cat back combo. So much so that with the windows up it sounds only slightly louder than stock. But that is not my final observation. Due to all the rain here, I have not had the chance to hear it with the windows down, nor is the exhaust fully broken in yet. I will edit this post with my final thoughts. I do miss the sound of the Helix and Perrin combo at idle though. Conclusion: Both are great downpipes. The Helix is a better value costing about $225 less if each was purchased alone. The Cobb won't match up to many of the 3" catbacks out there without some work because of the way it tapers and uses the factory donut gasket. The Cobb is better designed, and appeared to have more engineering but I don't know that it adds enough power or decreased turbo lag to justify the price tag. If you want the highest quality downpipe with the most R&D behind it and price is not an object get the Cobb. Otherwise as it is already suggested lots around IWSTI go for the Helix. You can't go wrong with either. This ad is not endorsed by this member. Please register or login to hide this ad. Last edited by aspensti05 : 10-12-2005 at 11:42 AM.

10-12-2005, 08:16 AM	#2
T1mmmy Professional STI Racer Car: 2004 STi Location: Nashville Posts: 740 Join Date: Apr 2005 Trader Rating: (9)	Great write up between the two! I was one of the few debating on either the Helix catted vs the Cobb catted, and because of my budget, i decided to go Helix. However, imo, i dont think you give enough justice to the perrin TBE. My friend just recently installed his on a 2002 WRX, and i think it doesnt sound too bad at all. However just my .02c . I love my helix catted downpipe. I can hear a slight difference between the helix vs the stock when mated to the stock catback. Tim

10-12-2005, 10:36 AM	#4
mx_9 Spec C Club Car: 04 STi Location: Cary, NC Posts: 1,030 Join Date: Feb 2003 Trader Rating: (0)	Nice writeup. Did you plug up the upper sensor bung or did you leave it as is? I left mine unplugged but saw one over the weekend that was plugged, so now I'm curious as to what others are doing.

10-12-2005, 10:39 AM	#5
aspensti05 Spec C Club Car: BMW M5 993 Turbo Location: Southwestern, CT Posts: 1,293 Join Date: Sep 2005 Trader Rating: (5)	mx_9 no clue what you are talking about. The bung right after the turbo is to be used for a wideband O2 sensor for air/fuel readings during tuning. the bung right before the midpipe uses the factory rear O2 sensor. The factory primary O2 sensor is in the uppipe not the downpipe. Please clarify which sensor you left unplugged.

10-12-2005, 10:45 AM	#6
mx_9 Spec C Club Car: 04 STi Location: Cary, NC Posts: 1,030 Join Date: Feb 2003 Trader Rating: (0)	Aspensti: I was referring to the tuning bung for the wideband 02 sensor. I left mine as I received it from Cobb, I believe as shown in the picture that you provided. The one I saw this weekend had a bolt screwed into it.

10-12-2005, 10:50 AM	#7
aspensti05 Spec C Club Car: BMW M5 993 Turbo Location: Southwestern, CT Posts: 1,293 Join Date: Sep 2005 Trader Rating: (5)	The picture of the Cobb downpipe has the plug in it. This is how it should look/arrive from the factory. If there is no plug in it, and no sensor in it, then I would think your exhaust would be really loud and you would be letting hot exhaust gas out under your hood. This is a really bad idea. This is how it should look:

10-12-2005, 11:21 AM	#8
JJ18Sniper Silver Member Car: 05 Subaru WRX STi Fav Mod: DB 20G, Diamond Black BBS RE's, S2K retrofit Location: NY Posts: 4,594 Join Date: Jul 2004 Trader Rating: (6)	Are there people converting the cobb downpipe to a full 3" fitment for 3" catbacks? I've always liked the downpipe, but I am interested in a 3" catback... anyone with experience?

10-12-2005, 11:39 AM	#10
*Neanderthal Racing* GT R US Car: CUTN EDG project Fav Mod: $20. mudflaps from auto zone Location: my cave Posts: 5,847 Join Date: Dec 2003 Trader Rating: (1)	Cobb downpipe vs. Helix downpipe (review) it's nice to see a product comparison based on actual experience rather than speculation. great job!

10-12-2005, 11:45 AM	#12
jgheels2003 Spec C Club Car: 2003 Z06 Location: Greensboro, NC Posts: 1,214 Join Date: Oct 2004 Trader Rating: (3)	I used to run the Helix catted on both the stock turbo and Deadbolt 20g. After getting great results with both applications, I can't imagine paying another $200+ dollars for something that wouldn't offer any performance gains. If the placement of the Helix cat is so bad (APS for that matter too), do you realy think they wouldn't redesign the thing? The Cobb is a ripoff. Not b/c its isn't great quality and doesn't work. It just cost a couple hundred more than something that works just as well and is equal in quality.