The Best of 2010: The Sierra Sierra TIme Attack EVO


sierra sierra evo

Flashback Friday – The Time Machine, Sierra Sierra's Record Holding Time Attack EVO VIII
By Mike Kojima and Eric Hsu, photos by Jeff Naeyaert

Ever want to look at a time machine and see what makes it tick?  Follow us and we will show you.  No we are not characters from an H.G. Wells novel but tour guides around what is for now the fastest production unibody based car in North America: Sierra Sierra's 2004 EVO VIII time attack machine.  In true MotoIQ style we will reveal many of the cars secrets and inner workings in a way that you just can't get from the other magazines and web sites.

sierra sierra evo

Powered by Cosworth!


sierra sierra evo engine
The engine bay on the Sierra Sierra EVO is crowded but tidy.  The car runs a nearly off the shelf Cosworth 2.2 liter long block with a Full Race turbo system and an Eric Hsu spec turbo.

At the 2010 Redline Time Attack season opener at Buttonwillow the Sierra Sierra EVO made history by turning the fastest lap by a time attack car around Buttonwillow Configuration 13 CW turning a 1:43.20 breaking the long standing North American Time Attack record set by the exotic HKS CT230R set in November 2007 of 1:43.523.

sierra sierra evo
Since we caught up with the car while the team was working on it, lets take a tour around  and see some of its speed secrets.

Is the Sierra Sierra car some uber machine made from unobtainium?  Did it cost millions to build?  Are there things inside that are impossible to replicate?  The truth is no.  In our opinion the CT230R is a much more sophisticated machine, approaching a SuperGT (JGTC) car in its level of prep.  It would be possible for a privateer to build something like the Sierra Sierra car as believe it or not, most of its parts are off the shelf and available to the public. Although these components may be expensive, they are purchasable by anyone.   The true secret of the Sierra Sierra car’s speed is not so much of the sum of the parts but through careful prep and testing done by a professional ex Formula Atlantic team, Cosworth and the driving skills of Dave Empringham.

sierra sierra evo eric hsu
Eric Hsu, Cosworth mastermind, inspects the head during between round maintenance.  He was inspecting the head but we asked him to look serious and point at something.  The EVO was plagued by head sealing problems early in the season which was resolved by the addition of gas filled o-rings after this article was originally written.
sierra sierra evo engine
The block's sealing surface is being inspected by Mike from the Sierra Sierra team with a ground metal bar and feeler gauges for warp.
sierra sierra evo
 The only thing you can't buy besides the secret Eric spec turbo are these prototype Cosworth cams that are bigger than the current M2 grind.  Cosworth may sell these soon.
sierra sierra evo
Tomei adjustable timing gears are used to tune cam timing.  Eric spent many hours on the dyno tweaking the cam timing to come up with a wide powerband.

So enough talking, let’s look inside the EVO starting with the engine.  The engine is pretty basic technology, at its core is an off the shelf Cosworth EVO VIII non variable cam timing 4G63 long block which anyone can buy.  The Cosworth long block consists of Cosworth's big valve CNC ported cylinder head with dual valve springs and Ti retainers, Cosworth 94mm forged billet stroker crank, Cosworth connecting rods, Cosworth 86mm forged pistons, Cosworth rod, main and thrust bearings, Cosworth H11 head studs, ARP main bearing cap studs, Cosworth 1.3mm FSL stopper type metal head gasket and a Cosworth cam timing belt.  The sole prototype parts in the long block are a pair of Cosworth prototype cams that may be available for sale soon.  Cosworth's Eric Hsu has spent a lot of time experimenting with cam timing to obtain a broad and tractable powerband.

Eric Hsu
Reading plugs is a lost art but Eric is old enough to know what he's doing in this case.

Sierra Sierra evo

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