Project GD STI- Keeping Cool with Greddy and Koyo!


The Synapse DV comes with all mounting hardware and plumbing.  We liked the cool quick release vacuum lines that the DV comes with.  The DV is available with Greddy, HKS, Turbonetics and Tial type flanges or with steel or aluminum universal weld on flanges.  The DV is also available with flanges for most OEM turbo cars as well for quick installs.  We opted for the universal aluminum weld on flange.  The DV tops are available in blue, black, red and gold if you want to color coordinate your engine compartment.  A blue one is shown here.
To keep things cool since much of our grill area is now obscured by our front mount intercooler we opted to upgrade our radiator with Koyo's racing aluminum radiator.  The Koyo radiator has been recently redesigned for better cooling. Koyo's revised version replaces the wide fin pitch 53mm thick core of the old version version with their new super efficient 36mm thick “Hyper V” core.  While being a thinner core at 36mm it is equally as effective since it has been designed with a much higher fin density.   It is still thicker than the stock core which measures 25mm. This improved version saves weight, improves space and air circulation to the engine and other components.  Thinner cores are better at heat exchange.  As a general rule of thumb for most heat exchangers, the majority of heat exchange takes place in the first 1.5 inches of the core which happens to be 37mm, about what the Hyper V core is.  Going thicker does not gain that much more cooling capacity.
The Koyo radiator has a CNC machined billet filler neck, giving much strength to this high stress part.  No plastic here.
The Koyo radiator features all TIG welding and perfect factory like fitment.  The radiator drops into the car and all brackets and fans bolt right up.  The radiator top tank features a 1/8 NPT fitting to aid in the fitment of temperature sending units or surge tanks if desired.
Koyo also makes high pressure radiator caps to help raise a cooling systems coolant boiling point and reduce pump cavitation.  Unlike another common brand of “performance” radiator cap commonly sold on the market. the Koyo cap is stamped from a heavy gage of steel so the tabs won't bend under pressure and fly off.
The Koyo cap gasket is composed of high temperature silicone rubber instead of cheap rubber like the other brand of caps.  This helps assure a long life and tight seal.


  1. Do you have any other picture for where the cooler mounts. Im trying to install the same kit on a 2004 sti and have trouble figuring out where the lower bracket goes.


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