Sierra Sierra EVO Update & BorgWarner EFR Turbos



Unfortunately or fortunately (depending on who you are) this is the last time you'll see a T04 anywhere near this EVO. T04s are relatively inexpensive and reliable on any other car, but Christine eats them for lunch. Before you come to the conclusion that sleeve bearing turbos are inferior, let's not forget the three GT35Rs Christine destroyed previously when the engine was making less power. T04 #1 was reliable up until 520 track miles (I log mileage of engines and turbos). This isn't a highway drive to San Jose 520 miles. This is 520 hard as fuck miles of continuous acceleration and deceleration between 6000-8600rpm. We thought we were stylin' at 520 miles, but then turbo #2 failed in less than 160 miles while we were at Sydney, Australia at the World Time Attack. #2 had excessive thrust in it and the wheels made excessive contact with the housings. Turbo #3 lasted the rest of the time in Sydney and through some dyno testing, where I retuned Christine to run on E85, which totalled approximately 140 miles. Then on the next test at Buttonwillow back in August it decided to give up:


It looks like the turbine wheel pretty much broke right off the shaft. I've seen turbine wheels spit out of the exhaust before on smaller turbos like Mitsubishi TD05s and Garrett GT2860Rs, but I can't say that I've ever seen a big ass T04 turbine wheel break and spit out the exhaust. The turbine wheel didn't quite get all the way out the exhaust. Mike found the remains of it 6″ behind the NTK UEGO sensor.


Back to that fine day at our September Buttonwillow test:

After the turbo fastener situation was fixed, Emp took Christine back out to re-baseline the car. After returning from Australia with softer suspension settings, Richard (team manager) and Emp wanted to work their way back to the Buttonwillow settings. Toward the end of the day, I noticed the water pressure was getting a bit high again which indicated a leaking head gasket. This isn't really a WTF?, but more of a FUCK AGAIN? After Emp brought the car back to the garage, Mike and Jet changed the head gasket pretty quick, made some setup changes and that was the end of day one.

It's no big secret that we've had some head sealing issues with Christine. It's fascinating to me how drag racing, internet tuners, and street car 4G engine builders/tuners like to comment on the situation. When's the last time they tried to do a 20 minute session at 700hp? Admitedly at Cosworth we've been slow to come up with a solution, but when we design a solution it will be done right. 1960s spec copper wire jammed into a groove is not “right” so it wasn't even a consideration. Anyhow, we designed some trick solutions and after some “motivational conversations” between Dennis (SSE team owner) and Cosworth, we've executed part 1 of said modifications. Stay tuned for a future update on the multi-faceted head sealing solution. What I can tell you for now is that the solutions are based on our WRC and Champ Car turbo engine head sealing experience so you know for damn sure it's going to be good. Lyon, one of our engine builders, was at TRD during Toyota's reign in GTP with the 1000+hp 503E 1.9L in-line 4 too so his input also helped tremendously.

Continuing on….after some warming up of the tires and brakes in near ideal conditions the following morning, Emp cranked out a 1:43.5 on two session old C91s. Damn, we should have had new tires on. Oh well, we were there just to test after all. Its not like we were there to smoke our old record. Or were we? It always seems that way, but how else would you measure progress? Another WTF? was when Emp was complaining about some massive wheel spin coming out of turns 1 and 3 and it was causing him to nearly go off track so he was having to back off on the throttle. The E85 conversion generated another 42whp and quicker boost response over the VP MS109 unleaded fuel, but that wasn't enough to smoke the tires like it was. In many cases drivers are always bitching about something, but when Emp says something is wrong, it means that something is wrong. We found out later that the ACD (active center diff) fluid pump was not working so in actuality we ran the 1:43.5 with an almost front wheel drive car. Anyhow, with the window of opportunity going away (it gets hot at BW real quick), the guys put on some fresh Hankook C91s with stickers and Emp went out again. His first out lap yielded a 1:43.7, but in the middle of the second hot lap, the biggest WTF? of all occured.



The Bus Stop is directly in front of the hot pits so we saw it all happen in slow motion. Emp was hauling ass turning into the Bus Stop at full tilt when a giant plume of white smoke blew out of the exhaust. Then smoke from under the hood filled the cockpit with smoke immediately after. Emp pretty much slammed on the brakes which inadvertently brought the EVO to a spin and stopped. He climbed out and there were small flames coming out of the hood so he started grabbing sand and dumping it into the hood vents. There were also flames at the exhaust exit on the body work which we later found to be engine oil burning.


Mike and Jet grabbed some fire extinguishers and took a rental car out there to put out the flames. Luckily the fire was put out with minimal damage. Watching it all helplessly from the hot pits was pretty sketchy though.


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