Race cars’ exhaust flames a cool waste of fuel
Dear Car Talk: I have exhausted all avenues but still haven’t found the answer.
As an avid fan of motorsports, I find very baffling as to why, when a car is decelerating, there is usually the presence of flames coming out of the exhaust. To decelerate, one cuts off the gas to the engine, but every explanation I can find says the flames come from unburned fuel.
That seem to be counterintuitive to me. Since you are the encyclopedia of things mechanical, the ultimate guru of gas, I was hoping you could explain this mystery. — Steve
Steve: I have no expertise in motorsports, Steve. The last thing I want to do after working on motors all day for a living is to come home and work on them for sport. But it’s definitely unburned fuel being combusted in the exhaust system.
How does it get there? Well, race cars have different valve timing than your typical Honda Civic — on which you have to pay extra for the fire breathing package. Because its sole purpose is to run at high speed and full power, the opening and closing of the valves on a race car engine is optimized for those conditions.
To provide that maximum performance at high rpm, they increase the overlap between the intake and exhaust valves. So, compared to your 2014 Hyundai Elantra, for instance, there’s more time when both sets of valves are open.
When the engine is running at 5,000 rpm, pretty much all the fuel that’s pouring into the cylinders gets combusted and used. But, when the car suddenly decelerates, some fuel continues to pour in but can’t be burned fast enough.
So, that excess fuel ends up being sucked out the exhaust valves and ends up in the exhaust system.
Those exhaust systems are generally straight pipes, with little to no baffling or curves to muffle sound like we see on passenger vehicles, so a flame that gets ignited by the spark as the fuel leaves the cylinder can easily come right out the back.
While that’s a terrible waste of fuel and a source of smog, it does have the benefit of looking very cool.
Dear Car Talk: I have a 2003 Pontiac Bonneville that has not been driven since the March 2020
lacks any type of intuition. It can be confounding, although has plenty of technology available and integration with smart phones. The design and integration place the infotainment system near the bottom of the segment and detracts from an otherwise high-quality interior.
As a mild hybrid, the tamer v60 has an EPA rating of 23 mpg/ city and 30 mpg/highway. I averaged nearly 27 mpg in a week’s worth of mostly suburban driving.
There are only two trims offered: B5 Plus and B5 Ultimate. My tester was the Ultimate with a base price of $54,100. This trim level has the following standard features: ventilated Nappa leather seats, Harman Kardon Premium Sound System, air purifier, park assist, pilot assist and special interior illu0mination. My tester had several other add-on features including 20-inch 7-spoke wheels, Bowers and Wilkins sound system, climate package and special paint color. As such, my tester had a final MSRP of $63,585.
With just a teeny bit more power (like that supercharged version) and a little better infotainment system, the 2023 Volvo V60 might be the “vagn” of choice for those who still love station vagns, er I mean wagons.