Sarah Forst posted on October 28, 2009 16:21
Project Acura NSX Part 3, Building a Race Proven C32 Engine
By Billy Johnson and Sarah Forst
At MotoIQ we have always contended that it is a much larger challenge to build an engine to hold up to the stress of road racing than nearly any other motorsports. For road racing or time attack an engine has to live despite being pounded on for many minutes at a time. A typical track session is 20 to 30 minutes long, way longer than a quarter mile or freeway blast. The continual stress of track driving is an acid test for an engines reliability, coolant and oil temps soar and the engine is run near redline for many seconds at a time.
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| The C32 has a lightweight alloy block with an open deck. The open deck gives good cylinder and head cooling and even heating of the top of the bore and combustion chamber for good emissions. Free standing cylinders also are easy to machine precisely and do not distort when the heads are bolted on. However for high powered turbo applications the free standing cylinders flex compromising head gasket sealing. Under heavy loads the cylinder walls can even fail. |
A high powered road racing engine cannot be slapped together using cheap Chinese knock off parts bought on Ebay. The attention to detail required to be reliable in this environment is intensive. In our case we will be taking on one of the biggest challenges for the tuner, building a track reliable turbocharged engine out of an engine that was not designed by the factory to be turbocharged. In this case, every bit of the engine must be scrutinized for suitability.
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| The C32 has a strong bottom end with main caps secured by 6 bolts each. The block has deep skirts and and double registers with large contact areas and cross bolting for stiffness. However when you more than double the stock power, the bores can distort causing bearing and crank problems. |
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| In this photo you can see the dual registers for the main caps and the holes for the ridged cross bolting. |
Project NSX is the Brainchild of FX Motorsports Development, an NSX tuning shop whose time attack turbo NSX is currently smashing unlimited class records throughout the Redline Circuit. FX Motosports Development is transferring a lot of the knowledge gleaned from their time attack program to build the ultimate NSX turbo street motor. The goals of our motor is to make a rock reliable 500 to 550 wheel hp on 91 octane pump gas with the ability to be track driven without missing a beat. Basically this engine is the same powerplant that propels Billy Johnson's FX Motorsports Development NSX Time Attack car to over 750 whp on race gas. For our project car, big power numbers are just a turn of the boost control knob and a tank of race gas away.
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| To fix the cylinder issues, Darton MID sleeves were used. The MID sleeve butts against the walls of the block and adjacent cylinders so the cylinders are fully supported. The MID sleeves are wet sleeves meaning that they are standing freely in the water jackets. The fins you see machined in the sides of the sleeve are called register fins, these give the sleeve support and still allow coolant to flow around the sleeve to improve cooling. The buttress you see at the top of the sleeve prevents the sleeve from moving or flexing even under high loads. The buttress is grooved and drilled to allow coolant to flow freely around the top of the cylinder and the head. This gives far better cooling and detonation resistance compared to regular sleeves. |
The C32 V6 Honda motor powering the NSX although being over 13 year old is still a pretty high tech powerplant, even by today’s standards. It displaces 3179cc with a 93 mm bore and a 78 mm stroke. It has a 10.3:1 compression ratio and a light alloy block and heads. It was also the first Honda engine to feature the revolutionary Vtec variable cam timing system. The C32 pumps out 290 crank and 224 lb/ft of torque in stock form. Of course we plan to more than double this!
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| In this top view of the MID sleeve you can see the buttress grooving and drilling. The MID sleeve is made of centrifugally cast ductile iron. This gives a finer grain to the metal for better wear, better frictional and ring compatibility properties. |
Follow us as we show how FX Motorsports Development gets it done, building both rock solid reliability and outstanding power.