Sierra Sierra EVO Pre-WTAC 2011 Update


Superlap Australia: And what about the rest of the world? We are certainly seeing more and more Cosworth parts turning up on cars in Australia with quite a few of our entries even running full Cosworth built engines.

Eric Hsu: The great thing about a weak US dollar is that it makes anything from the US more affordable for everybody else! Cosworth parts are now available in Australia at All Star Garage, HiOctane, Tuspeed and a few others. These companies  all stock and order Cosworth parts regularly which is great for customers who don’t want to deal with customs, shipping, money transfers, or getting jacked on eBay.

This year I’ll be coming to WTA 2011 with Tyler who is another Cosworth engineer. We are planning to visit customers and potential customers in other states and check out the Aussie market for ourselves. The way I see it, the more customers Cosworth has in Australia, the more excuses I have to come every year!

Aside from that, we’re also coming to scope out the Prep’d Motorsport Lotus Elise. There’s been talk within the Cosworth USA engineering department to develop Elise parts and to build the ultimate Time Attack Elise.

Superlap Australia: Awesome Eric thanks for your time. Last year the Sierra Sierra car was an absolute crowd favourite and I am sure this year will be no different. We look forward to seeing you guys at the creek in August.

Eric Hsu: Yep, I can’t wait for the event. Aside from competing in the event, the World Time Attack Challenge is the best Time Attack event I have ever been to. While I haven’t been to any in the UK, they don’t have all of the world renowned Time Attack cars in one place, on the same track, on the same day trying to smoke the crap out of each other.

Being in the heat of that kind of competition is just plain awesome. WTAC is a really special event. Everybody’s friendly, you’re surrounded by ultra fast turbo cars, and Sydney is an awesome city with plenty to do. Plus Aussie beer is pretty damn good too.  I always tell people to take a vacation and make it to Sydney during the WTAC so they don’t miss the event of the year. See you guys soon!

Aside from the fact that we were all too busy to really publish anything, it finally caught up to me and people have been blowing me up and EVERYBODY has been asking me for the past couple of months, “WTF is going on with the Sierra EVO!?!” So let’s get to the point. Here are some pictures of those mods I spoke about in the interview. 

Here is the latest and greatest BorgWarner EFR 9180 turbo. It’s the largest turbo in the EFR line and it was chosen because of both the compressor and turbine’s additional flow capacity over the 8374. The latest and greatest Sierra Sierra spec Cosworth 4G63 breathes incredibly well. The 8374 wasn’t big enough for the Cosworth 2.2L at 2.2bar of boost (google EFR compressor maps) at 79 lbs/min.  Brock from BW suggested we use the 9180 and because of the increased turbine stage efficiency, we might get away with only a slight increase in lag, but with a measureable increase in top end power. It turns out Brock was right. Now with the 9180, we have more boost on tap should Dave request it (and he probably will). Remember that Christine is a heavy pig with very little of the factory sheet metal cut out of the car. So where Tarzan in the CyberEVO lays down the lap times with balance and finesse, Dave and Christine does it with brute power. If you look inside the car, you’ll find that it’s amazingly intact. Attached to the turbo is also a lightweight version of the Full-Race twin scroll exhaust manifold with a slightly larger inside diameter than standard. Not yet attached to the exhaust manifold are the trick Turbosmart wastegates.

While the EFR turbine housing is quite a large piece, it is a zero compromise part that was optimized extensively using both CFD simulation and gas stand testing. The giant turbine wheel is of course made from Titanium Aluminide for ultra low inertia. What about the extra lag you might be wondering? I made changes in cam timing, some remapping of the Cosworth Pectel SQ6 ECU, and the engine generated the exact same response as the 8374, but with a bundle more up top (57hp @ wheels) at the same boost. This was of course due in large part not only to the turbo’s greater operating efficiency, but also to the Cosworth head and SWB cam package’s efficiency. Of course I don’t really recommend using a 9180 whenever matchbot tells you to use an 8374, but in this instance the hardware was there to support the turbo. For more information of BW EFRs check out my original article about the EFR Feature Set.

These trick little Turbosmart wastegates are the bomb. Mike can change the springs in around three minutes in the hot pits if necessary. How does he do it so quick? Check out this article about the CompGate 40 wastegates.

Here is latest version of the Cosworth 4G63 94mm 2.2L stroker components.The rod bearing is the same rod bearing used in the legendary Cosworth DFV F1 engine. Through building and racing 4G63s in extreme conditions, we’ve designed the ultimate crank, rod, and piston combination to endure both extreme cylinder pressures and RPM.

You can see here that a 100mm stroke crank is the weakest of all 4G63 configurations. Sure, a drag or street engine can get away with it, but a lap around the road course is like 10 quarter mile runs back to back PER LAP. A crank has to be super robust to withstand the cyclic thrashing of road racing. The rod journals on this latest Cosworth 94mm stroker crank are oversized by 4.2mm to increase the amount of overlap between the main and the rod journals. The rod journals are also narrower than stock so that there is considerably more material around each rod journal. It is also heat treated using the same proprietary Cosworth 90 hour heat treat and quench procedure our F1 crankshafts are subjected to.

Leave a Reply

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