Fundamentals
The J-series engine incorporated into the KB1 employs a very similar layout as the J-series engine native to the TL/TL-S, as well as the Accord V6 lineup. Having transverse engine layout is inherent with most Acura/Honda V6’s. Honda resorts to a primary catalyst for each side of the exhaust manifold, which is cast into the head itself. Essentially it’s an extremely compact 3-1 merge that takes place before it even exits through the head into the primary catalysts. Primarily tuned for optimal efficiency in emissions, as well as manufacturing ease, it leaves much to be desired on a performance level.
There are three components of these engines that are typically turned to for performance gains. The primary catalysts (or pre-cats), J-Pipe, and the Cat-back exhaust system. The pre-cats are fairly short in length and compact in shape thus much diversion from the factory design besides incorporating a higher flowing catalyst is fairly limited. Following the pre-cats the J-Pipe merges the two pulses from the separate banks together. Manipulating the factory J-Pipe in this case allows us more flexibility in adjusting the powerband to produce the desired increase in power and torque.
Factory Exhaust Setup
It’s easy to see the multiple restrictions the KB1 exhaust system inhibits over the 3G TL-S. This is in part due the choice of going with a semi-true dual setup for the RL. This produces a series of restrictions right from the beginning of the exhaust gas flow. The initial merge from bank 2 into the y-merge of the factory J-Pipe compromises performance greatly as friction to velocity ratio is much more critical in these sections of the exhaust system than it is further back towards the mufflers (Pinpoint A).
The factory setup involves many unnecessary power robbing components such as the merge into a single catalyst (3rd catalyst) to retain the manufacturing ease of using the same 3rd cat that can be found on all their transverse V6 power plants (Pinpoint B). Coming out of the 3rd catalyst it splits back to a true-dual setup. This again results in an unnecessary friction component as well as another source that will create internal turbulence (Pinpoint C). At last but not least, the factory design incorporates yet another hiccup designed to reduce exterior exhaust note which is the addition of 2 resonators per exhaust stream and a reduction of ID tubing size at the exit of those resonators (Pinpoint D).
ATLP J-Pipe & Mid-Section 1
Our first plan was to make a part that replaces only the J-Pipe itself with the remainder of the exhaust system stock, but there is much left to be desired with only a J-Pipe replacement on a factory system that has this much restriction. A slightly more out-of-the box thinking landed us with the final decision to proceed with a J-Pipe & mid-section that allowed us to result in the most measurable power gains, enclosed an option to upgrade to hi-flow catalyst of the factory bottleneck, and also produce a more prominent exhaust note over the tinny, near non-existent note.
As proven by numerous dyno results and tests we have done to document various merge locations, we’ve shown that moving the merge further downstream up to a certain distance, consistently produced a higher torque and horsepower output throughout the whole powerband. In order to accommodate the J-Pipe to work with the factory cat-back exhaust system, while maintaining most useable power we designed a J-Pipe that extends back to the axle back mufflers flanges. This in term allows us to utilize a properly placed x-over merge to keep the velocities efficient throughout the entire length, which also means there will be a consistent power gain, not just found at wide-open throttle (WOT) that other parts claim.
The prototype design and R&D will be document here for clients to follow along. The first picture of many to come is only a non-functional mock up piece of the work in progress and is merely to show a rough idea of where this will be going. The final production piece will encompass mandrel bends, full 439 stainless steel construction, and will be a complete bolt-on replacement. Of course this will allow the KB1 to retain is factory look and drive-ability.
Loading ...