Exhaust System Testing

Khrome Werks AR-100 versus SuperTrapp 2-1

Why compare two exhaust systems?
Despite the proliferation of big inch EVO engines, there seems to be little information comparing exhaust systems for these engines. Prior testing results on 80CID engines has generally shown the ability of 2-1 systems to provide better power than 2-2 systems. There is a new crop of large OD 2-2 pipes for big inch and high power engines. Nightrider decided to test one of the better 2-2 pipes available against the de-facto standard of 2-1 systems.

Khrome Werks AR-100
Khrome Werks manufactures their "AR 100" line of 2-2 pipes. The AR 100 exhaust system is a 2" OD exhaust system that uses Khrome Werks patented anti-reversion technology to improve power. The AR 100 pipes are one of the best engineered and manufactured exhaust systems on the market today. The quality of the chrome is superb. Fit and finish on the test pipes installed on the 94 FXDL test bike was excellent.

SuperTrapp 2-1
The SuperTrapp 2-1 system is a tried and tested system that has been used by Nightrider in most of its performance projects over the past 6 years. This exhaust system consistently sets the standards for power that other pipes are compared against. The particular exhaust system used in this test was a set of chromed pipes marketed under the Rev-Tech name.

How and what was tested?
The test methodology was simple. Run dyno comparison tests of the SuperTrapp with and without baffles against the AR 100 pipes for a total of 3 tests. Minor jetting adjustments were made to provide the best possible results, but no changes were made to ignition timing. The tests were conducted on a DynoJet 250 located at CycleRama in Pinellas Park, FL. 

The un-baffled SuperTrapp test was conducted because past tuning efforts have resulted in the highest horsepower and torque figures from this configuration. When the pipe is run without the baffles, the power band is quite narrow and peaky. This is a good combination for drag racing, but it is deemed unsuitable for street performance. This pipe setup is also very loud, sounding more like a race bike than a street machine.

The normal street configuration of the SuperTrapp on this engine is 21 disks and an open end cap. This configuration is also similar to those in other tests published by several v-twin specialty magazines. The power band for this setup is known to be very wide and flat, something that is very desirable for good street performance. The normal  SuperTrapp setup has always had very reasonable noise levels to it, and the typical smooth sound of unequal length 2-1 pipes. True performance enthusiast seem to like the sound while unknowing v-twin purist is more worried about the pipe not looking like they expect a Harley to look like.

The performance of the Khrome Werks AR-100 was the unknown factor in these tests. Prior testing of 2-2 pipes against SuperTrapp had generally resulted in disappointing horsepower and torque results. What the other 2-2 pipes did not have was the large diameter pipe and the AR technology. The power output of the Khrome Werks AR-100 pipes was quite unexpected and very refreshing to see.  The sound on the AR-100's is a very pleasant, low pitched rumble. These may be the best sounding 2-2 pipes on the market.

What about Twin Cam engines?
Because the test engine was a large bore EVO engine without a longer stroke and has a bathtub style combustion chambers on the heads, it is probable that TC 95 engines would see similar results with components that matched the specifications of the EVO parts.

What is our analysis of the results?
Running a SuperTrapp 2-1 without baffles is not recommended for anything other than race applications. A comparable test of the Khrome Werks AR-100 pipes without baffles was not conducted, but there is reason to believe that these modified pipes would show an increase in horsepower. Experience tells us that a set of modified AR-100's would match or exceed the horsepower produced by the SuperTrapp. The un-baffled SuperTrapp test was conducted to provide a benchmark number to compare the street configuration 2-1 and AR-100 against.

The baffled SuperTrapp makes above 100 ft.lbs. of torque between 3200 and 5700 RPMs. The SuperTrapp made better power below 4500 RPMs than the 2-2 pipes. The AR-100 makes above 100 ft.lbs. of torque between 3700 and 5800 RPMs.  Above 4500 RPMs the AR-100 pipes are making 2-4 HP more than the SuperTrapp's up to the testing limits of 6500 RPMs.

How would this play out for performance?
From stoplight to stoplight, the SuperTrapp has the advantage. This is a "street" performance situation where torque rules. For dyno shootouts, high RPM roll-ons or on the Drag Strip the higher horsepower of the AR-100 pipe would win the race. An engine with a 6000-6500 RPM working RPM limit will spend very little time below 4500 RPMs. Here is where horsepower rules.

What is the recommendation?
Ignoring the performance results of a good 2-1 exhaust system is hard to do. The mid-range power potential of these systems produces a strong street machine. But there are a lot of riders out there that do not like the looks of the a 2-1 system. There is also a growing number of street/competition bikes out there that will not compromise performance for street-abilility. These are the riders that the Khrome Werks AR-100 pipes are made for. For riders that are looking for uncompromising maximum horsepower, good looks and a pleasant sound, the AR-100 is the exhaust system for you.