Headers/ Oil Cooler

Some of the other work I did on the car in 2015 was adding headers/cats/x-pipe, C5 Z06 Titanium axle back, and an oil cooler with integrated thermostat.

 

Here are the headers I went with, XS Power makes them.  They are very similar to the American Racing Headers design but only cost $800 instead of $1800.  Sorry ARH but I am not paying $1800 for a set of welded tubes, that is what a ball bearing turbocharger costs and turbos have WAY more complicated machining/casting operations and exotic materials.  There was some weld breakthrough on the inside of the collector and where the primaries are welded to the flange, which I cleaned up with a Dremel, but otherwise I was decently impressed with their quality.

Formed collector, not pretty but it gets the job done. 

X-pipe with high flow cats.  Nice extra O2 bung on the x-pipe for a wideband.

Stock cats/H-pipe.  Heavy!

 

Stock exhaust manifold.  Actually pretty light but definitely sapping power.  Even when I first bolted on the headers without a tune it was a very noticeable power increase in both mid range and high RPM.  Plus they sound awesome...

 

Weight-wise, the headers/cats/x-pipe was maybe 6-8 lbs lighter than the stock setup but that was how much the oil cooler added, so I came out even.  The axleback was where the big savings were, going from steel to Ti.

For my oil cooler setup I went with this handy thermostat from Improved Racing that opens only when the oil hits 212F.  Bolts in place of the stock oil temp sensor and has the two fittings for the cooler plus room for the oil temp sensor to go back in.  Nice part.

Adapter plus braided lines.  Nabbed a lightly used DRM setup off of Corvette Forums.  Added insulation where the lines pass near the headers.

Headers installed with C5 Z06 Ti axleback.

Oil cooler installed.  Oil temps much more stable now, never seen them get above 240 in the dead of summer on asphalt hot lapping autox runs.

Shocks!

Here's an overview of the work I did to adapt a set of Ohlins TTX36 shocks to my car.  Why didn't I just buy a set of Penskes or MCS's?  It definitely would have been faster and easier but Ohlins USA is located about 20 minutes from my house and I know some guys that work there so I was able to get a little discount on my parts which made the cost less of an issue, and rebuilds/revalves are a manner of stopping by on my lunch break.  Plus the TTX dampers are the only 2-way shocks that have both low speed compression and rebound adjustments, which is the important region for autocross use.  And lastly, because they look cool and are unique!

 

Started with some stock shocks, a couple drawings of the interface joints on the TTX's, and some Delrin spherical upper mounts based on a Hardbar/Banski design.  The fronts were easiest since they use a T-bar lower mount and a pintop upper.  Only thing I had to figure out was how to go from the Ohlins shaft threads to a C5 upper mount, and what size T-bar I needed to make.

Some CAD time and a little lathe work by a local machine shop, and we have a front shock.  Uses an Ohlins spherical bearing with a machined T-bar for the lower mount and a custom adapter from the Ohlins shaft to the spherical Delrin upper shock mount.

Here is one of the shocks getting dynoed at Ohlins USA.  I spec'd out the valving based on stock C6 Z06 high speed with a fattened up low speed zone.  One of the benefits of the TTX shock is that it has massive adjustment range so that even if I guessed off on the valving (which I was pretty far off on the rear shocks), you can still turn the clickers and get them dialed in.

Here is the first iteration of the rear shocks.  Same upper mounts as the fronts, with new pieces to go from the TTX bolt pattern to the C5 lower control arm. 

Ended up needing a spacer to clear the reservoir.

Spacer welded in.  Not the prettiest mount but it works as a prototype.  I am planning to update these to a single machined piece.

Finished rear shock.  Laser cut upper mount also pictured, which replaces the stamped steel stock upper mount.  I made a flat piece to take some stack height out of the assembly to get more shock travel.  Rear upper mounts are being updated for 2016.

 

So how do they drive?  Fantastic!  Going from C6 Z06 shocks to these was an incredible difference, both in general body control and in the fact that I was able to quite easily adjust them to tame some bad habits the car had like excessive corner entry oversteer.  I used Neil Robert's shock tuning guide and in the course of a single 2-day autocross event was able to make big changes to how the car drove.  I am now able to attack transitions and corner entries much harder than before without fear of the car losing control.