The Best of 2010: The Sierra Sierra TIme Attack EVO


HKS Kansai intake mainfold
The HKS Kansai intake manifold has a much larger plenum chamber, shorter runners and a larger throttle body from an Infiniti Q45.  On a well modified engine the manifold can be good for 30 or more hp.  A Cosworth Thermal Guard intake manifold gasket helps reduce heat soak from the engine to the intake manifold.
sierra sierra evo
The Fuel Safe fuel cell has a foam filled rubberized bladder for crash safety.  The fuel cell has an internal high volume low pressure fuel pump that fills a built in surge tank.  Two Bosch 044 Motorsports fuel pumps take the fuel from the surge tank to the engine.  The surge tank keeps the car from getting fuel starvation under high cornering loads.

The Cosworth long block breathes through an HKS Kansai intake manifold equipped with an Infiniti Q45 VH45DE throttle body.  An OEM throttle body was chosen because of its superior sealing. Many of the popular aftermarket Mustang throttle bodies leak boost and do not have durable throttle actuation hardware. The manifold is insulated from engine heat by a Cosworth Thermal Guard Intake manifold Gasket.  In the manifold 1600cc RC injectors feed the hungry engine with oxygenated VP MS109 fuel being pumped from the Fuel Safe fuel cell by two Bosch Motorsports 044 pumps. The Bosch 044s draw from the Fuel Safe cell’s internal surge tank with baffles and trap doors. This internal surge tank is fed by a low pressure in-cell fuel pump. The internal surge tank prevents fuel starvation under high G loads.

Sierra Sierra EVO full race twin scroll manifold
A Full Race Twin Scroll exhaust manifold speeds spool by 1000 rpm and feeds the exhaust to the top secret Eric Spec sleeve bearing turbo.  Twin Tial Wastegates keep the exhaust pulses discrete for maximum use of every bit of pulse energy.
twin scroll turbo
In a twin scroll turbo, cylinders 1-4 are paired into one side of the turbine housing and cylinders 2-3 are paired into the other.  That way the exhaust pulses are kept 180 crank degrees apart.  This helps volumetric efficiency by keeping backpressure in check, gives the turbine discreet pulses for better efficiency and reduces overlap charge contamination.

A Full Race Twin Scroll exhaust manifold is used.  Twin scroll manifolds pair cylinders 1-4 with 2-3 feeding into opposite sides of a divided turbine housing. The twin scroll utilizes the engine's pulse energy of the engine to spool the turbo faster.  With the divided housing the turbine wheel is hit with 4 sequential discrete pulses, this transfers more exhaust energy to the wheel helping it spin up faster.  The divided housing also improves volumetric efficiency as the overall pressure in the exhaust and turbine housing is less due to the pulses being evenly spaced out in timing.  There is also less opportunity for charge contamination due to reversion because the pulses are kept separate so a pressure pulse from a cylinder on the exhaust stroke cannot back flow and contaminate a cylinder on overlap.  This allows the cams to be run on a tighter lobe center which helps the engine have a broader powerband.  The divided housing turbo and a twin scroll exhaust manifold can improve turbine efficiency by around 15% which can speed spool by around 1000 rpm or make up for a 25% gain in rotating mass, like some of the lag caused by a larger turbo. The twin scroll manifold is kept fully divided by running two independent Tial 38mm MSV wastegates.  

sierra sierra turbo
Secret Eric spec turbo.  He isn't talking but I took a guess at what it is.  Read the text to find out.

The exhaust gasses are fed into a Garrett TO4 non ball bearing turbo speced out by Eric Hsu.  He won't tell me what it is, but I think it’s a BCI-18 wheel in a 4″ SO4 type housing probably with a high 80 something mm exducer and a fairly high trim.  The exhaust side is probably a NS111 or T350 type wheel with a 70 something trim with an 0.80 something A/R exhaust housing.  Am I close Eric?

sierra sierra evo
A lightweight Cosworth core intercooler chills the charge air and a C&R radiator keeps the coolant temperature under control.  Check out those trick quick release Wiggins clamps on the charge tubing.  Those cost some duckets!
sierra sierra evo
A Tial blow off valve is used.  All of the coolant and charge air plumbing  uses the purple Wiggins quick release clamps, just like F1 cars!  This speeds maintenance.

The exhaust is fed from the turbo to a Custom 3.5″ stainless steel exhaust fabbed up by Sierra Sierra's Mike.  The exhaust is ovalized for better aerodynamics under the car NASCAR style and to clear the flat bottom belly pan. On the pressure side, the air is fed into a Cosworth spec lightweight tube and fin 24″x12″x4″ intercooler.

sieera sierra evo
The 3.5 inch exhaust is pretty free flowing.  It's fabricated from thin wall 321 stainless for light weight.  The exhaust is put together with quick release V-Band clamps, one bolt and it's free.
sierra sierra evo
The exhaust is oval under the car so it can fit under the flat bottom.  It exits on the cars side.  Two exits are used so the cross sectional area is not decreased as the tubing goes oval.  Oval tubing is used so the exhaust can fit under the aerodynamic floor pan.

sierra sierra evo

Leave a Reply

Your email address will not be published. Required fields are marked *