Ooh, pulse turbocharging is very very very interesting! I work at an automotive research company and we’re working on a project related tot hat right now actually. Basically, most turbos are tested on a steady-flow gas stand, and efficiency maps are generated at various pressures and flow rates. On the engine,…

Basically yeah. You want minimal pre-turbine volume so that you get the most amount of energy delivered to the turbine. Preventing pre-turbine heat transfer also helps deliver more energy to the turbo.

Turbos operate on a pressure differential. For the same volume flow rate, hotter gas will have a higher pre-turbine pressure. Higher pressure differential leads to more choo-choo.

While I generally agree with your premise, there are a couple things that aren’t quite right in your argument.

The emissions should be compliant, period.

So if you’re apexing late and, as you put it “cornering harder”, then wouldn’t the FWD car actually be able to carry less speed through the corner because it needs to make a tighter turn?

I was seriously asking, why couldn’t you carry the same speed into the corner? Weight distribution? What if a RWD and FWD car had the same weight distribution?

Yeah, I know that more weight up front gives more grip. But now we’re talking about weight distribution, not drive layout. I know it may not be common, but if a RWD car and a FWD car had the same weight distribution, then their braking, corner entry, and mid corner grip should be the same right?

Race car is faster than road car, details at 10

Why couldn’t you carry the same speed through the corner with a RWD car? Braking, turn-in, and steady-state lateral grip should be completely independent of drive layout.

Why couldn’t you carry the same speed into the corner with a RWD car? Braking, turn-in, and steady-state lateral grip should be completely independent of drive layout. I think the slow in, fast out mentality is more for novice drivers than something inherent to the RWD layout

A common solution theorized at this point is to keep the test that same for certification, but also perform spot tests under different conditions and set a separate limit (say 1.5x the regulated amount) for those tests. I think it would be a good step in the right direction.

They’re not necessarily cheating while being tested, they’re just engineered very carefully to pass the test. The problem is that test does not appear to successfully represent real-world driving. I would argue that the problem lies not with the automakers, but with the regulations themselves.

Crashing into an identical vehicle traveling at the exact same speed would be exactly like hitting a wall at the same speed. Having two cars doubles the kinetic energy of the crash, but the energy is dissipated over 2 cars, resulting in the same damage to each as if they hit a wall.

A head-on collision with an identical vehicle with each car travelling 50 mph would result in the same inertial forces as crashing into an immovable barrier at the same speed.

Haha true...I feel that current diesel emissions regulations are about right when it comes to the amount of various emissions allowed, the problem is the testing procedure that does not reflect real world driving, and the large exclusion zones of the engine operating map where the regulations do not have to be met.

It’s important to note that this lawsuit is not coming from the EPA, but from “ANDREI FENNER and JOSHUA HERMAN”...just two random guys. At this point, the government is not investigating GM for emissions cheating.

It’s important to note that this lawsuit isn’t coming from the EPA, it’s from “ANDREI FENNER and JOSHUA HERMAN”...just two random guys. Yes, the truck may emit more that the regulated amount of certain emissions, but the testing they did was for real-world driving, not the regulated test cycle.

It’s all off-cycle testing...they drove a truck in stop-and-go traffic with a Portable Emissions Measurement System (PEMS) hooked up. Stop and go traffic is nowhere near the type of driving encountered on the test cycle, and PEMS units are notoriously inaccurate.

While you’re right about small particles being very hazardous to human health, typically diesel soot has larger particles and all modern diesels have particulate filters that remove most of the soot from the exhaust stream. Some modern direct-injected gasoline engines have actually been shown recently to emit more of…