I've always wondered what the effects are on exhaust and turbo spooling, especially at low speeds and part throttle. Conventional wisdom with turbo's says that a larger diameter downpipe and catback exhaust improves turbo spool speed and improves performance by improving efficiency. At full throttle this makes sense. The turbo works less pushing the air out becoming more efficient and makes more power.
Take for example the GM 2.7L turbo 4clinder L3B engine. It has a dual volute turbo to spool up quick and provide peak torque around 2k RPM's depending on the application. AFE makes a larger mandrel bent downpipe and catback exhaust for this engine in the Silverado/Sierra configuration (off-road only). Video's on the Youtube show the turbo spooling up MUCH quicker even at part throttle. The trucks sound like performance diesel engines right off idle.
So more than likely this improves performance at wide open throttle...but I've always been curious what would happen under normal part-throttle conditions. You'd be into boost quicker and off-idle torque would improve...but what about part throttle fuel efficiency, throttle response, overall drivability, etc?
Is this a free lunch (off road only)? Or does getting into boost sooner kill fuel mileage? Thanks!
Take for example the GM 2.7L turbo 4clinder L3B engine. It has a dual volute turbo to spool up quick and provide peak torque around 2k RPM's depending on the application. AFE makes a larger mandrel bent downpipe and catback exhaust for this engine in the Silverado/Sierra configuration (off-road only). Video's on the Youtube show the turbo spooling up MUCH quicker even at part throttle. The trucks sound like performance diesel engines right off idle.
So more than likely this improves performance at wide open throttle...but I've always been curious what would happen under normal part-throttle conditions. You'd be into boost quicker and off-idle torque would improve...but what about part throttle fuel efficiency, throttle response, overall drivability, etc?
Is this a free lunch (off road only)? Or does getting into boost sooner kill fuel mileage? Thanks!