After almost a year with the GTR and getting the build to its current state, I knew dealing with drone was inevitable once the catless downpipes were added to the car based on input from other GTR owners and tuners I've spoken to. I originally started with a Greddy Ti 94mm XL system that proved to be too loud for my tastes even with stock downpipes. Sold that after two weeks and purchased/installed an AMS non-resonated midpipe from ACG. Although that setup sounded nice, it produced too much drone at legal freeway speeds.
Prior to our Thanksgiving interstate road trip, Sam at Importsports drop shipped a Borla XR1 muffler so I could have my local muffler shop install it. The added muffler seemed to hit the spot in cancelling out any type of drone at highway cruising speeds. To my ears, the stock catback with resonated midpipe and stock downpipes was the perfect combination. There was no drone or rasp yet had a refined sound on the outside without discomfort inside the cabin. We completed my Alpha 9 build in early January 2017 which included the installation of the AMS catless downpipes. The volume and tone changed once the catless downpipes were installed and not for the better as the drone returned. It really started to get old after < 2k miles so it was time to start researching larger diameter (4"/102mm) exhaust systems that would yield improved performance but not necessarily the increased decibels.
There are differing opinions and perceptions of drone and some GTR owners are perfectly fine with the added noise and willing to sacrifice comfort to tolerate it. Some even prefer their exhaust systems obnoxiously loud which is obviously not my style or preference since the car is taken on long trips. Overall, I prefer my FI cars to be silent from the exhaust end when cruising at normal highway speeds and filled with high-pitched dual ball bearing turbo suction noise when WOT. Think large displacement turbo diesel motor with multiple large diesel mufflers and less so the trumpet-like sound of the typical GTR aftermarket exhaust system. It was quite easy to find something to accomplish the latter but quite challenging to do the former. Not too many folks go around publicly asking for the quietest exhaust system available on the market.
The 4" exhaust systems I looked at were the GTC Titan, Boost Logic, ETS, SBD, Fabworx, and Tomei exhaust systems. I was able to eventually narrow it down to just the GTC Titan based on feedback from Kerry (Goonthree) and videos; or so I thought. While researching the GTC Titan, I came across other exhaust systems on the gtr.co.uk forums from UK-based tuners that are not commonly installed on GTRs stateside. Two companies in particular -- Litchfield and Garage Whifbitz -- stood out with both systems marketed at 95-96dB which complies with the track noise restrictions at Silverstone. There were some GTR owners selling both types of exhaust systems on the forums because they were TOO QUIET?! Eeeeh?!!
Intrigued by those posts, I contacted both tuners for more information. Garage Whifbitz offers a bargain of a system at < $2,000 for a 4" SS system that included a resonated midpipe. Litchfield, although priced higher, was my choice for various reasons (more mufflers, brand, etc.). The availability of extended video sound clips and pictures of the Litchfield system on Youtube and Instagram also ultimately helped me make an informed decision. I was very close to pulling the trigger with the Garage Whifbitz system (it's cheap!) but the lack of multimedia sound clips was the deciding factor. I wasn't comfortable making a decision based on a single 10-second sound clip of free-revving. Hopefully more media will be available in the future. It seems like the Whifbitz system might be comparable at a cheaper price for those on a budget.
After a few days of back and forth analysis between two specific 102mm UK exhaust systems, I decided to go with the Litchfield system. Also being a big proponent of extensive real world R&D and having already owned many AMS products, Litchfield was a good fit and made sense from that standpoint as some would also consider Litchfield a top-tier brand with high quality products and the after-sales support to back up those products.
I reached out to Litchfield's parts manager -- Lee Turley -- directly via telephone to discuss my options. Lee clarified the configuration options available for the exhaust system and it was clear the triple-silenced system was what I needed. It consists of three mufflers/resonators in the midpipe in addition to the two large rear mufflers. A quote was sent via email the same day and I wire transferred the funds over to Litchfield from my bank (required for international transactions).
The midpipe had to be produced while the other components were in stock and ready to ship. At this point, I was told the midpipe would take 2.5 weeks to receive. The full system shipped out six calendar days after placing my order with shipment received two days thereafter via UPS Express a total of eight calendar days to my home; far in advance of the estimate. Lee was very helpful during this process and in answering all the questions regarding whether the configuration was enough to cancel out the drone. He assured me it was more than sufficient.
Fitment and installation:
After DIYing the installation of the Greddy exhaust on ramps I swore I would never do another DIY exhaust installation on the GTR without a lift. However, with 14 cars booked at ACG in preparation for the Shift-S3ctor event on 2/28, the installation simply wasn't going to happen at the shop unless I wanted to wait until later the following week. DIY it is!
Before starting the install, I remembered new exhaust gaskets for the flanges between the downpipes and midpipe were not included with the system. I could either order new replacements a few days in advance or reuse the old gaskets if still in good condition. The local auto parts stores here in San Diego did not have 3" inner diameter gaskets for two-bolt exhaust flanges in stock when I checked; especially not the metal ones. Even though new gaskets were initially used between the mid and downpipes, I noticed some signs of slight leakage on the upper side of the flanges. Because I wanted to use high-temp silicone (Hondabond or comparable) anyway to prevent any future leakage, I chose to reuse the gaskets as they were both in excellent condition. Thanks to the guys at Importsports in Denver for that tip to eliminate the leakage. Even though ISP didn't do the original install, they had warned me weeks in advance to look out for the leaks while the exhaust system was off the car and advised me on how to remedy it for the foreseeable future.
Installation was pretty straight forward. Having worked with vBand before, things went pretty smoothly. The most important thing to remember -- tighten the vBand clamps after everything is lined up on the same plane -- otherwise things will never line up. The midpipe was a challenge due to the weight of the three mufflers. Due to the lack of space to maneuver underneath the car, it felt like doing a skull crusher with a barbell to get the piece in the proper position and alignment. It is important to note that the main muffler on the midpipe could scrape while going over certain speed bumps when installed on a lowered car. Other than the space constraint challenges, the exhaust went on without a hitch.
I spent quite a bit of time on the exhaust tips with the infinite amount of ways to align the tips and due to a minor issue where the piping of the tips were a hair smaller in diameter than the maximum clamping diameter of the OEM exhaust tip clamps. Even when the OEM clamps were maxed out, there was some movement where I could rotate the tips if enough force was used. Although the tips weren't going to fall off the exhaust, I wasn't comfortable with the movement. If it wasn't 1am at this point, I would have just gone out to buy different clamps but I improvised to get it done. To tighten things up, I inserted some stainless steel strips (stainless steel ties with ends cut off) into inner the circumference of the clamps. The strips (shims) slightly increased the diameter taking up the slack and allowing the clamps to bite down. Problem solved.
I spent another hour or so adjusting the tip angle, elevation, and depth so the exhaust tips would stick out slightly further than the stock alignment with hopes of less soot on the bumper when on 91 octane. At this point, I was done literally and figuratively. Startup and test drive would need to happen later in the morning since it was almost 3am once all everything was buttoned up.
Here are some photos taken off of Litchfield's IG account showing the entire system. Due to the lack of a lift, even with a full frame wide angle, I could not take good enough photos showing the entire system. Note the third vBand connection in the photos. The updated piping I received eliminates the need for that third vBand flange near the rear diff. Makes it harder to install but less connection and potential leak points.
Sound and Performance:
Having started up the car for a few seconds to check for leakage the previous night with the garage closed, I wasn't expecting cold start to be that eventful. To my surprise, it was even quieter with the garage open -- in a good way. As soon as I drove down the driveway and common area streets in 1st gear, I knew it was much quieter than the previous setup. There was no longer any reverb off of the buildings and it sounded pretty similar to stock even when engine braking with the throttle closed.
I drove a few miles on the side streets and on the freeway to get engine and transmission oil up to temperature in preparation to go WOT. Part-throttle low RPM sound or the lack thereof was exactly what I had hoped for. The exhaust is near silent in the low RPM band during normal part-throttle driving between 2-4000 RPM with no detectable drone. Freeway cruising was now boringly quiet with the run-flat tires stealing the show; a sound I didn't really notice with the catless downpipes.
Oil temps finally reached my target of 170°F so it was off to my favorite straightaway. The exhaust came alive especially toward the top end of the powerband when I let it rip in second/third gear. Perfect. Most folks typically associate loud with fast and quiet with slow. Sounds can be deceiving but the butt dyno isn't. Although it wasn't as loud as before, the car felt faster especially in the midrange and top end. Well save the low end power and backpressure of a smaller diameter exhaust debate for another time.
Since I let my tuner, Chris Black, know my intentions in advance of installing the larger exhaust, he advised that a datalog would be needed to ensure the tune was still within parameters. We confirmed the fuel trims and AF ratios still look good and we will confirm HP/TQ figures are within safe limits in a dyno session at ACG in the coming days. During the recording of the videos, I felt the clutch slip for the first time in the two months since installing the Alpha 9+ turbos so I'm guessing the car might be up on HP/TQ from the 640/554 we originally put down on the ACGs Mustang dyno in early January. We shall see.
For those that want the performance of a large diameter exhaust without the noise or drone for everyday normal driving, the Litchfield 102mm Triple-Silenced system is the clear winner. The exhaust is marketed at 95-96dB to comply with track sound restrictions at Silverstone and, after a full week of testing, I have no reason to dispute that claim. It is as advertised -- super quiet. Cruising is no louder than stock and it can be deep and throaty when going WOT. It is quite possible the system could be even quieter with stock downpipes as my car has AMS catless downpipes. Other mods that may or may not make a difference in sound are also in my signature.
A big thanks to Lee Turley at Litchfield Motors, Chris Black, James at ACG Automotive, Sam at Importsports Performance, Kerry (Goonthree), not just on the exhaust advice, but for the continued support on my entire build.
Videos & sound clips:
Videos are best viewed with headphones or full range speakers to experience the full effect...
The following video is from Litchfield's site. The blue GTR runs the same triple-silenced exhaust system and gives a better idea of what it sounds like on the track. Start at 3:03 if you wish to skip directly to it. Compared to the gray GTR, it is much quieter.
UPDATE - 3/9/2017
The dyno session at ACG Automotive was yesterday afternoon and Chris Black was able to clean things up with three pulls. We confirmed what usually happens going to a larger exhaust without a revised tune during the initial baseline run. The car gained 32HP up top and lost some low end torque. Looking at our street logs from last week, we knew that was going to occur due to increased boost on the top end under heavier loads in 3rd to 4th gear. The HP gain might not be considered a direct result of the exhaust; more so the boost increase due to a freer flowing exhaust. Would be interested to hear thoughts on this.
Because the car is still running a stock transmission, we elected to keep things conservative as the clutch was starting to slip with the bump in power. Chris kept me at +10HP over my original tune numbers with a similar torque number (648/555 on a Mustang dyno). We also added the Cobb TCM add-on to adjust clutch capacity and added two more maps (low and medium in addition to kill).
I'm pretty happy with the numbers and the car runs great so, unless something unforeseen occurs (knock on wood), the car will remain in its current state for a little while until I'm ready for a Shep transmission. Thanks to James and Scott at ACG along with Chris Black for the continued support in getting the car running perfectly!
Here's the video and some photos from yesterday:
Edited by L.L., 01 May 2020 - 02:24 PM.