This is a high quality custom rear diffuser for the Datsun 240Z, 260Z and 280Z. It is CNC cut from 1/8" aluminum, precision formed and TIG welded. It is designed to fit around the OEM fuel tank but will likely work will a fuel cell depending on size and location. The diffuser is open on the driver side to allow room for exhaust but also has that opening mirrored on the passenger side for those running a fuel cell and dual exhaust. Installation (though recommended to be done by a professional) is fast and easy and all of the needed hardware is included. In a matter of 30-90 minutes depending on the installer this diffuser leaves the back end looking clean but aggressive. It is available in raw (unfinished) aluminum or powder coated matte black and weighs only 14 lbs. The openings for the exhaust are 10" wide and 5" tall not including the cutout for the exhaust tip.
Below is some feedback from Steve Hoyles who has track tested our S30 Rear Diffuser. His comparison graph can be seen in the pictures above.
I spent some time on the track over the holidays trying to get my car
setup with your diffuser and I thought I would share some data. I run
your diffuser on both my personal race car and we also have one on my
team's WRL race car. Both cars are 240Z's (see photos attached). On
my race car I run a front splitter which extends to the engine cross
After mounting the diffuser the car immediately has
much more rear grip but understeers badly. After playing with setup I
found that adding 3 PSI to the rear tires and setting the wing to zero
degrees (6 degrees without diffuser) balanced the car fairly well. A
comparison graph of the data of the best diffuser run vs. my previous
personal best is attached. The diffuser run was about 0.8 seconds
faster (1:45.0 vs 1:45.8) and about 5MPH quicker at the end of the
longest straight. The car is still a little understeer biased so my
mid corner speeds are a little off with the diffuser but I think with
a little more tuning I could get another half a second out of it. I
am a staff instructor at this track and I have thousands of laps on
this car. Dropping 0.8 seconds in one tuning session is very
I'm very happy with how effective the diffuser is at adding rear
downforce while keeping the drag of the car low.
Thank you for making such high quality products for these old cars!!
With your stock diffuser and a 3" splitter the car is VERY balanced and easy to
drive at the limit.
Diffusers are used in most racing venues and below is an excerpt from Wikipedia that describes the theory behind a diffuser.
When a diffuser is used, the air flows into the underbody from the front and sides of the car, accelerates and reduces pressure. There is a suction peak at the transition of the flat bottom and diffuser. The diffuser then eases this high velocity air back to normal velocity and also helps fill in the area behind the car making the whole underbody a more efficient downforce producing device by reducing drag on the car and increasing downforce.
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