Time Attack Terror: FXMD's Record Setting Acura NSX
By Mike Kojima and Billy Johnson
If you follow Time Attack at all you are probably very familiar with FXMD's Acura NSX Unlimited RWD killing machine piloted by our own Fast Lap Editor, Billy Johnson. In the 2009 Time Attack season the NSX has given the competition the business in every event it has entered for an undefeated 2009 Redline Time Attack season. Some of the sizzling times posted by the car are a 1:45.247 at Buttonwillow 13CW, 1:18.555 at Willow Springs, 2:13.057 at Spring Mountain and a 1:36.103 at Autoclub Speedway.
The NSX has been not only winning its class but also taking top honors for the overall fastest time as well. To our knowledge this makes the FXMD NSX the fastest time attack car in North America. A lot of other publications in both print and on the web have featured the NSX but not like how we are, into the deepest recesses of its guts. A lot of you MotoIQ fans are serious gear heads and are probably curious about what is inside the ultimate time killer. So pull up a chair and let us take you around and inside what is probably the fastest production based full unibody car in North America.
|The 3-1 tubular header for the left cylinder bank is visible here before it feeds into the large TO4Z turbo, the blue anodized cannister is the 44mm Tial wastegate.|
The base of any successful race car is a strong engine and the FXMD NSX is no exception. The Acura C30A engine with VTEC is built not for peak power but tractable horsepower over a wide range and stone solid reliably when run hard for long periods of time. The engine has been steadily evolving over the past year into a solid, trouble free package. The engine puts out over 750 whp on high boost. The block is fortified by Race Engine Development with Darton MID centrifugally cast integrated deck sleeves punched out to 93mm (the stock C32B size) and billet main bearing caps. An FXMD forged billet crank and rods and CP pistons are used for the reciprocating components. An unusual semi dry sump system assures lubrication under high G loads. Two engine driven pumps scavenge the oil pan to an external tank where it is de-aerated, cooled, and pumped back to lubricate the engine by a heavily modified stock oil pump with bigger and stronger gears. The heads are fitted with Ferrea valves and Supertech valve springs, and titanium retainers. There have been a lot of mistakes about the engines specs and internals made by other publications but we have been deeply inside of it. To learn more about the engines internals in detail you can read about it here.
|The large oval tube exit is the main exhaust. The smaller one is the wastegate discharge. Good wastegate plumbing is important as sometimes over 60% of total exhaust flow can come from the wastegate! The exhaust discharge location helps the lower diffuser create more downforce by energizing the flow around the exit of the diffuser.|
|Here is the FXMD street turbo system being test fitted to our project NSX. We are including these pictures so you can see how the turbo fits into the chassis with the diffuser off. Nearly the same turbo system that powers Billy's race car is going to go on our project car. Stay tuned!|
|Another view of the street turbo system. |
The engine’s horsepower is fortified by an FXMD turbo system using an equal length stainless tubular header feeding a single Tial Sport Garrett TO4Z Journal bearing turbo. Boost is controlled by a Tial 44mm external wastegate. A single turbo is used instead of the usual easier to package on a V configuration engine, twin turbos because of a single turbos inherent simplicity, packaging, and efficiency. Being a mid engine, the exhaust system is just a short piece of stainless tubing with an oval transition to exit. The pressurized air from the turbo is cooled by an AFI water to air intercooler with a Tial blow off valve preventing compressor surge at lift throttle. Engine management chores are handled by a Motec M48 firing RC1600cc injectors. A Motec CDI keeps the fire lit even with sometimes difficult to ignite E85 green fuel.
| The Garrett TO4Z is covered by a cermaic blanket to control heat in the crowded rear of the car.|
| The Motec ECU and CDI unit are located in the car's cabin away from heat on this carbon bulkhead.|
| This is a larger volume plenum for the engine's intake manifold.|
| The trunk area is full of stuff, not luggage. The lower box is the water to air intercooler, you can see the Tial blow off valve on the intercooler discharge. The other boxes contain a ducted heat exchanger for the engine oil, the transaxle and the engines air box! This is a complicated car!|
| The is the heat exchanger for the rear mounted water to air intercooler in the front of the car. Hot water is pumped from the intercooler to be cooled here.|
|This is the surge tank and reservoir for the water to air intercooler located in the front trunk. The pump is near here as well.|
From the engine, the power is taken to the ground via an RPS billet twin carbon disc clutch and lightweight flywheel that feed an FXMD modified transaxle. A close ratio JDM gear set is deburred and WPC treated for strength. For details on the transaxle prep click here.
| The radiator is ducted here and the discharge air is routed up and out vents in the hood. This help generate more front downforce.|
| The surge tank and the bleed point for the cooling system is mounted on a high spot in the engine compartment.|
| The oil tank/ de-aerator for the dry sump system is mounted in the engine compartment. The FXMD NSX is one of the most complicated race cars we have yet to see!|
An OS Giken limited slip diff was specifically tuned and set up for the cars traction requirements. It is a little known fact that diff set up is a vital element in dialing in a cars handling. For details on how this was done, check here. FXMD modified axles with vented and polished CV joints finish out the drivetrain.
|Since grounding on the alloy body NSX is a little problematic, this box heps.|
|The FXMD NSX uses a RPS Twin disc carbon clutch to contain the Honda engines power. After this picture was taken, the metal clutch plates were WPC treated. Billy reports that this greatly improved clutch smoothness.|