The Supra has a full 3.5-in exhaust system, custom built by Modified by KC. Here’s a shot of the MKC 3.5-in downpipe, which starts off of with the V-band flanged 3-in turbine outlet, and quickly flares up to the full 3.5-inches. It’s white because it got sent off to Swain Tech for its White Lightning high temp coating, along with the beautiful PHR exhaust manifold featured in Part 4.
In 2007 I’d performed a test for Modified Magazine, which compared the power difference between a 3.0-in exhaust system with “closed”, recirculated wastegate versus this actual 3.5-in exhaust using the same wastegate, but “open” and venting to atmosphere.
Given the 3.0-in “closed” had a total 7.07 square inches (in2) flow area, including the wastegate, the 3.5-in “open” system not only measured 9.62 in2, but the surface area of the HKS 60-mm wastegate had to be added because it was now venting to the atmosphere. This meant an additional 4.38-in2, for a total of 14-in2—or a 100% increase in flow! The difference between a 3.0 “closed” system to a 3.5 “open” is huge.
As a result, at 19 PSI the power went up from 527whp to 609whp on pump 93 and methanol injection, with a peak 103whp gain up top. At 29 PSI the power rose from 699whp to 764whp, but the car seemed to be running out of boost or reducing timing in the latter run. It looked like it wanted to hit around 775-780whp but we stopped there, given our fuel.
Evenso, I’d proven that, even at just 500whp, you can do better than just a 3.0-in exhaust diameter if you want to significantly free up power. I preferred not to go to a full 4-in system because I didn't want to deal with clearance issues, and the noise level would surely be increased. But since we've now gone from a single 60-mm HKS wastegate to twin 46-mm Precision Turbo units, our new total wastegate flow area was 5.15-in2, which was a 17.5% flow increase over the 60-mm unit. This difference alone raised our turbo-back exhaust area to 14.77-in2, which also meant a 5.5% increase in flow over the previous 3.5-in setup. Hey, we'll take it!
When compared to a 4.0-in exhaust with one 44-mm wastegate (which has a 14.91-in2 surface area), some might be surprised to find out that our 3.5-in twin wastegate setup flows 99% as well, and is both quieter and provides better ground clearance than the 4.0-in setup.
When the manifold came back from Swain Tech, I wrapped it with Thermo Tec exhaust wrap to help keep the heat inside the piping, and away from the rest of the engine bay (and hood paint).
The final touch was Thermo Tec’s 2000F protective spray. The silver color matches the rest of our engine bay better, and has stayed this color for months thus far.
The turbo blanket pictured here is also from Thermo Tec, and it covers our PT6766 1.15 AR split turbine housing, which is also Swain coated. See Part 5 for more details. This picture also shows what the wraps and blanket look like after about 3k miles. They're still as good as new.
As mentioned earlier, this car is now running on AEM’s Infinity EMS, which provides as much bang for your buck when comparing to EMS units costing 50% more. Our Supra is also running on AEM's newest 2.96 version software, which was just released less than a month ago. Installation was made easy using AEM’s Supra-specific plug-and-play harness. Porsche 996 and 997 turbo owners will be happy to find out that AEM has just released a plug-and-play harness for them!
In the United States, we must remind you that alll AEM Infinity stand-alone ECU’s are legal only for off-road use, and should be not used on any public highway. As long as the AEM Infinity is installed on Project Supra, this car is officially an off-road-use car only.