Hydr0nium

I volunteered to purchase and review the newly developed Corksport single exit cat back exhaust system, and want to write up a full report to review the product. I hope that this is useful to anyone interested in the system, or anyone that is on the fence about this or another single exit exhaust system.

First of all, I want to give a big thanks to Corksport for actually developing this system. I always appreciate companies that take a risk to develop a new product. There is a lot of time and money spent in these types of projects with virtually no guarantee of recouping that investment. So thank you Corksport and your development team for offering another single exit exhaust system to the RX-8 community!

Product Review:

The product was shipped to me quickly, cheaply, and packaged really well. All the major void spaces within the box were filled with packaging paper so that the components would not jostle during shipping. All the piping was bubble wrapped and the muffler section had extra protection around the tip and canister. The installation hardware was in its own separate box, and all the paperwork was encased in plastic.





Items in the box included:

Purchase receipt
Warranty Information
Installation Instructions
All necessary hardware to complete installation (picture below)
Exhaust pipe section
Muffler Pipe section



Product dimensions and build quality:

The ID of the pipe sections is 2.4":


The muffler tip is 3.4" ID:


The wall thickness is 0.05":



The welds are beautifully done except for one instance:


I don't know what happened to this one, but obviously not of the same quality as the rest, but I have zero concern that it will break or leak:


The inside of the piping was all properly cleaned up except for one instance, but nothing a little bit of filing can't fix:


And finally, the inside of the canister:


So as you can see the build quality is superb, with very few cleanup omissions. Very impressive.

Installation and assembly:

The inclusion of an installation manual was very unexpected, and a great reference. Installation was a little slow for me, but I like to take my time the first time around. The most difficult part was removing the old exhaust from the rubber hangers. The only tip I can suggest is to use a really large screw driver as a lever and keep at it. It takes a significant amount of elbow grease to remove these, so don't be worried to put your back into it.

The only other hiccup I had was connecting the flared end section to the catalytic converter. The instruction manual assumes you are able to remove the rear studs so that you can install the ones that were supplied with the system. I could not remove these, and therefor had to make some adjustments to the compression springs in order for this to work.

With this exhaust, the factory 14mm nut that comes off the studs/spring section cannot be rethreaded onto the studs with the factory springs. You need to cut off about 3/16" from the spring inorder for it to fit properly. This equates to about 1.5 coils:


This will leave you with a spring approximately 1" long:


Once this step is completed, it is really just a matter of bolting things up, hanging the exhaust, and making sure there are no leaks. Fairly straight forward, and no real surprises.

One caveat though:
This system WILL require you to modify your exhaust shroud. I didn't complete this step yet, and will as soon as I can source a replacement shroud. I personally don't like doing permanent body modifications without a backup available. So for the meantime I will run without the shroud.

Overall impressions and sound results:

This exhaust system is EXTREMELY light weight. It weighs 14.2 lbs according to my scale, compared to the stock 40lb system (39.9 on my scale). This is probably the biggest selling point for this system.

The price is very reasonable, especially compared to some of the heavier, dual exhaust systems. It was shipped to my door for around $400 even. Great price for a great product.

Fitment was spot on. I thought there was going to be some issues when mocking it up, but once you get the hangers bars fully seated in the rubber hangers, it all comes together nicely.

And now for probably the most important aspect to any exhaust system; sound.

This exhaust is loud, louder than I was expecting. Very aggressive idle, and revving is intense. The 1-3k RPM range is a little rough under load with a little bit of resonation, but the sweet spot is at 3.5 and above. The tone is excellent, very deep and pronounced.

Here is a before/after video for you to get an impression of this system. Just bear in mind that the video does not capture the intensity accurately:



Conclusion:

This is a very reasonably priced, lightweight exhaust system, quite possibly the only factors that matter with modifications on this platform. I cannot speak on horsepower gains or anything of that matter. But we can safely assume that no noticeable gains will be made with this system alone. However, the weight savings IS noticeable, and very appreciated. The only strike in my book against this exhaust is the volume. I am not sure it will pass noise restrictions at track events/autocrosses in it's current state. I suggested to corksport that an inline muffler be added, but the sacrifice will be price and weight. Adding in your own muffler is definitely an option, and one I might be pursuing. Or the addition of a silencer might benefit as well.

Hopefully this review will answer most of the questions you had about this exhaust. If you have any further, please feel free to post them here, and I will answer them to the best of my abilities. Thanks guys!

yomomspimp06

sounds good. no popping?nice When you get a chance how about some drive-bys and in car vids? I know the sound is slightly different under load. I also know that the sound quality is much better in person. So far so good minus the shroud problem :/

9krpmrx8

iTrader: (46)

Some more pics would be appreciated too. I'm not surprised it is loud but I am surprised that you were surprised My HKS Hi-power was very loud.

It's too bad the piping is only 2.4"

pdxhak

iTrader: (2)

Just install a turbo and the loud issues go away

Nice review.

bingo

Thanks, good write up

Hydr0nium

Unfortunately, the exhaust is clearly going to be too loud for me to complete in any sort of sanctioned event, so I have gone back to stock until I find something to replace it/suppress it.

I did try to get some incar video, but it didn't turn out very well.

See above.

That is actually exactly what I was thinking. I feel like this would be a perfect car for turbocharged applications, both for noise and flow.

Why is 2.4" dia. too small? This system flows incredibly well, and I wouldn't really see any application where it wouldn't fit (except something incredibly rare like a 3 rotor turbo car, or LS swap.).

autoxgt

Are you still running the factory mid-pipe and cat? Sorry if I missed it.

flyinglizard

iTrader: (1)

Nice Review. I just got their dual exhaust about a month ago and I love it so far. Quality is great and it has a sweet spot at ~ 3500 - 4500 RPM where it is almost silent so it doesn't drone on the freeway. FYI I previously had the TurboXS exhaust (mated to both the OEM cat and their racepipe) and I hated it in both instances. Way too heavy and way too loud/unpleasant sounding.

2.4" inches is NOT too small unless you're running FI.
OEM is 2.25 and obviously flows extremely well since there is so little power to be gained with aftermarket exhausts.

cfm251

iTrader: (3)

I like this! ive been meaning to freshen up my old exhaust setup.

cfm251

iTrader: (3)

Curious as to the price. If you cant publicly post please pm thanks.

Hydr0nium

Yes, everything else is stock other than a drop in K&N filter (with intake baffles removed), and this cat-back.

Exactly. There is really no reason to have anything larger than stock other than the perceived idea that larger piping is better. Even for most FI applications, 2.4" will be plenty of piping to flow properly. Like I said above, you would need something crazy like a 3 rotor turbo swap, or something with more displacement than our engines to require anything larger than 2.4".

See above. In all honesty, the diameter of piping will not come into play unless you are making somewhere around 300-350 whp on these cars.

GeorgeH

iTrader: (2)

Do you know this for a fact? Have you had the sound level checked at a track day or autocross? You might be surprised. My system is very loud - to the point that I am very self-conscious on the street. But I have never had a problem at a SCCA solo event. If you have not already done so, I suggest bolting it back on and taking it to an event. It's the only way to know for sure.

Hydr0nium

No, I have not had this officially measured at my events, but I am fairly certain it would not pass.

My event locations have a 93 and 100 db cap, and according to corksport:

I completely agree with you: I won't know until I actually get it measured--but I would not like to chance the DNF and will just run my stock setup this weekend.

Very unfortunate, because the weight savings is so attractive!

GeorgeH

iTrader: (2)

Note that most clubs give you a grace period. Unless it's a national event, you can normally get away with one bad weekend.

Also, the SCCA solo doesn't measure at 10 ft. Don't remember the exact spec but it's further away.

I say run it as-is at least once & see.

Hydr0nium

Looks like Corksport is going to rush deliver me a silencer. So I will bolt it back up for Sunday and get readings with it on and off. So we will see how it does then.

ShinkaEvo

iTrader: (3)

Tempting...somehow I couldn't find it on their site...?
Let us know how the resonator works.

Hydr0nium

It hasn't *officially* been released yet, but will be soon. Probably once I have wrapped up all the loose ends--testing wise.

Stay tuned!

Hydr0nium

So as far as I know, they didn't take sound (of course) at this event. Apparently if there aren't enough workers, sound is the first item to be cut. I asked several people, including the chief of workers, and he wasn't able to source any sound logs during the--but I digress, on to the review:

Here are some pictures and dimensions of the silencer that CorkSport sent me:











So as you can see this is a very large reduction in flow area (almost 9.25x smaller). In my opinion, this is way too small, and back pressure will be an issue with this size of an opening.

The silencer installs fairly deep into the muffler, and is attached by one bolt and nut. This is a problem, because the silencer itself isn't a very tight fit. So any slack results in extreme vibration and noise. If there were two points of attachment, this issue would be resolved. But currently, the only thing I can think of would be to add a layer of header wrap around the perimeter of the silencer to create a tight fit.

As I said, the lose fit creates alot of unwanted noise. In my test video (posted below), you can actually see the silencer deflecting at 7K rpms. I took this video after a 30 mile trip home from the autox on the highway. I tightening the silencer pretty well before I left, and I think the vibrations loosened it up a bit more.

Sound suppression wise, this thing works excellent! In car sound is almost to stock level at highway speeds, which I didn't think would be possible. Cruising speeds, and low speeds are excellent. Acceleration, especially hard acceleration are a different story. The only way to describe it is...cheap. It makes the system sound very cheap. The deflection of the silencer allows additional exhaust gasses to escape around the outside of the silencer which actually sounds like water rushing through a narrow pipe. Coupled with the metalic sounds during gear changes (engine deceleration) just make it worse.

So in summary, does the silencer do its job effectively? Yes, very well. Does it improve the system, yes and no. It makes it drivable in neighborhoods and on the highway. Getting on the highway is not so pleasant, but it turns what I would call a race only exhaust into a streetable exhaust.

Would I recommend this system? Yes. If you are looking for an affordable, light weight, easy to install system that is backed by a very reputable company, most definitely yes--only if you don't mind/are looking for a loud system.

I would also recommend this for racing applications. Auto crosses I still feel might be a bit of a gamble, especially if you have strict sound regulations. But as far as time trials/HPDE's, you will more than likely be fine.

Finally, here is a before/after video of the silencer installed and uninstalled. Like I said, I took this video after I got home from the autocross, driving 30 miles at 75mph. I think the vibrations might have loosened the bolt a bit, so the metallic sounds can be cut down significantly if you really crank down on the nut&bolt.

Revs are 3, 5, 7, 3k rpms in both before/after.


I hope this review was helpful! Let me know if you have any further questions, and I will answer them to the best of my ability. Thanks!

yomomspimp06

sounds great without the silencer...not so great with it
thanks for the vids and review