Project Lexus IS-F Part 2: We test the PTS – Joe Z Series Exhaust

,

People either love or hate the IS-F rear exhaust section. A lot of people call the IS-F’s rear exhaust section “fake tips”.  Really they are just a styling feature for the rear fascia.  Since the IS-F was introduced several other exotic cars like Ferrari have adopted similar features.  When you look underneath the car, you can see that the “fake tip” is actually a rather sophisticated part which includes a stainless rear heat shield with a diffuser.  The diffuser has a scoop which collects air from under the car to cool the exhaust stream so it won’t damage the rear bumper.  It’s kinda neat.

The PTS – Joe Z exhaust also has nice features like thick, laser cut stainless flanges that resist warping for a better seal.  No slip fits, mild steel flanges or other crap here. Many cheaper stainless exhausts actually have mild steel flanges; the Joe Z is 100% stainless.  The welding on the system is all hand TIG, not MIG and is quite beautiful, like fabricated race car pieces.  All welded seams are hand port matched.  The muffler sections and tail pipes are polished while the mid pipe is a brushed mill finish which looks pretty nice while sparing the expense of polishing a part that no one will ever see.  The tubing is thicker walled, about 14 gauge.  This is to reduce ringing; a Lexus is after all a Lexus and not a race car.  Some weight can be added here to make the car more daily drivable.

Like the stock exhaust, the PTS muffler feeds into the diffuser in about the same position.

The 2.5” tubing is appropriately sized for the engine.  One of the coolest features is a siamesed X pipe in the mid pipe.  Joining sides of a dual exhaust system helps reduce droning by having exhaust pulses mix and cancel out.  Joining sides of a dual system also usually improves low and mid range torque.  Although the most common way to do this is with an H pipe, the X pipe does this more efficiently.  Some companies literally make an X out of the tubing but this adds turbulence and backpressure as the exhaust streams are forced to mix in a limited cross sectional area.  Joe Z has the exhaust streams communicate in a smooth sweeping merge that does not add backpressure.  We use this sort of X in all dual systems we design for this reason.

The exhaust fits nicely under the car with no problems with rattles or body contact.

The PTS – Joe Z system uses two sets of mufflers.  First are a pair of straight through perforated core resonators.  Joe tells us that many iterations of these resonators were tested until these were found as the ones that reduced droning on the IS-F engine.  Length, perforation count and packing density were all fiddled with to come up with these silencers.  Finally, the exhaust exits though twin large case straight through perforated core absorption type mufflers.  Like the resonators, these mufflers were tuned around the engine for a lower sound level free of irritating droning.

Wow that is a nice exhaust system!

The mufflers exit into the stock IS-F exhaust diffusers exactly like the stock exhaust does.  All hangers and other exhaust parts are made of 304 stainless and are tig welded.  A lot of other exhausts sometimes cheat lower grades of materials here but not this exhaust.  Despite being a true dual system the PTS – Joe Z Series exhaust saves six pounds over stock.