stupid question?
04-27-2007, 01:47 AM
#1
Three Wheelin'
Thread Starter
Join Date: Sep 2003
Location: Bremerton, WA
Posts: 1,750
Likes: 0
Received 0 Likes
on
0 Posts
stupid question?
I'd like to learn more about turbocharged cars and turbos in general. I'm pretty stupid about them quite frankly 
I've read that our cars make more boost when more load is placed on the engine. This why we make boost faster in 4th gear than third, for instance. Right?
So, here's my stupid question.
Do you racers with ~600 lbs shaved from your car have to wait longer for boost?
I've read that our cars make more boost when more load is placed on the engine. This why we make boost faster in 4th gear than third, for instance. Right?
So, here's my stupid question.
Do you racers with ~600 lbs shaved from your car have to wait longer for boost?
04-27-2007, 06:36 PM
#2
Rennlist Member
No. Less weight means less torque is required to get the car moving. This means the car speeds up faster, thus going thru the RPMs quicker, thus accumulating boost faster. Besides, it's not necessarily (particularly in racing) about how quickly boost comes on. To quickly, and the car is uncontrollable. Also, power-to-weight ratio is ultimately what matters usually, not speed of boost accumulation.
To give you an example, I am part of an engineering design competition which builds formula-style racecars using no more than 610cc of engine displacement thru a 20mm restrictor. One team from Norway (I think) built a turbo F4i engine (600cc) that netted something like 120hp (which is absolutely incredible thru such a small restrictor) but on the dyno sheet between 6k and 8k the car quadrupled its horsepower. The boost came on so suddenly that none of the drivers could control the car in any of the dynamic events.
To give you an example, I am part of an engineering design competition which builds formula-style racecars using no more than 610cc of engine displacement thru a 20mm restrictor. One team from Norway (I think) built a turbo F4i engine (600cc) that netted something like 120hp (which is absolutely incredible thru such a small restrictor) but on the dyno sheet between 6k and 8k the car quadrupled its horsepower. The boost came on so suddenly that none of the drivers could control the car in any of the dynamic events.
04-27-2007, 10:51 PM
#4
Rennlist Member
Hey I was in FSAE, learned a lot. One of the best ways to learn about turbochargering is books, this forum, and of course fixing your car.
The engine has more time to spool up in the higher gears. One of the big things is that you have to look at the gear ratios and where the torque is.
Turbocharging is essentially using the pressure from the exhaust pulses to push a turbine(hot side) is connected to a shaft that is connected to a compressor. The compressor(cold side), because of the way the shaft is spinning, sucks air in and because of the shape of the blades and compressor housing, the air is compressed.
Going back to a naturally aspirated engine that sucks(Vacuum) more the faster the engine spins, a forced induction via turbocharger has exhaust pulses that increase with engine speed and spin the turbine faster which in turn starts to force air into the engine via the compressor. The forced air reaches boost when the turbocharger spins fast enough to overcome vacuum.
Turbochargers are known for torque because of the way that compressed air effects an engine. When air is forced into the intake manifold and into the cylinder, there is much more air in the cylinder than in a naturally aspirated engine, hence a larger explosion, which creates more torque felt by the piston and connecting rod. With more air, you have to add more fuel to suffice a safer stoichiometric ratio of air and fuel. Too much air and not enough fuel(lean) can cause detonation in the cylinder which is firing from air compression not necessarily the spark plug.
The 944turbo uses an intercooler to reduce charged air temperatures into the engine by using air coming into contact with the intercooler like a radiator to cool well coolant. The reason that intercooling is worth the hassle of adding more plumbing is evident. Cooler air is denser than warm air so the turbocharger can compress and cram more air into the cylinder. This is more efficient and powerful than not using an intercooler. The air from the turbo is warmed by the compressor because of thermal conduction from the hot side of the turbo. This is why intercooling makes sense.
In order to control boost, the 944 turbo uses a variety of instruments to achieve reliable boost. The engine has a knock sensor computer that reads engine data and vacuum/boost pressure to determine how much is too much. When the knock sensor decides to, it electronically opens a valve(cycling valve) to let pressure to the wastegate and open another valve that defers exhaust pressure from the turbine. The pressure from the cycling valve comes from a hose connected to the intercooler pipe.
Oil is a major player in turbocharged engines(like most engine) for the reason that the turbo gets extremely hot and oil "cooks" and thins or breaks down the viscosity that in turn reduces the oils ability to lubricate the engine.
I'm sure I'm beating a dead horse and I'll let the other guys help... and I'm tired
The engine has more time to spool up in the higher gears. One of the big things is that you have to look at the gear ratios and where the torque is.
Turbocharging is essentially using the pressure from the exhaust pulses to push a turbine(hot side) is connected to a shaft that is connected to a compressor. The compressor(cold side), because of the way the shaft is spinning, sucks air in and because of the shape of the blades and compressor housing, the air is compressed.
Going back to a naturally aspirated engine that sucks(Vacuum) more the faster the engine spins, a forced induction via turbocharger has exhaust pulses that increase with engine speed and spin the turbine faster which in turn starts to force air into the engine via the compressor. The forced air reaches boost when the turbocharger spins fast enough to overcome vacuum.
Turbochargers are known for torque because of the way that compressed air effects an engine. When air is forced into the intake manifold and into the cylinder, there is much more air in the cylinder than in a naturally aspirated engine, hence a larger explosion, which creates more torque felt by the piston and connecting rod. With more air, you have to add more fuel to suffice a safer stoichiometric ratio of air and fuel. Too much air and not enough fuel(lean) can cause detonation in the cylinder which is firing from air compression not necessarily the spark plug.
The 944turbo uses an intercooler to reduce charged air temperatures into the engine by using air coming into contact with the intercooler like a radiator to cool well coolant. The reason that intercooling is worth the hassle of adding more plumbing is evident. Cooler air is denser than warm air so the turbocharger can compress and cram more air into the cylinder. This is more efficient and powerful than not using an intercooler. The air from the turbo is warmed by the compressor because of thermal conduction from the hot side of the turbo. This is why intercooling makes sense.
In order to control boost, the 944 turbo uses a variety of instruments to achieve reliable boost. The engine has a knock sensor computer that reads engine data and vacuum/boost pressure to determine how much is too much. When the knock sensor decides to, it electronically opens a valve(cycling valve) to let pressure to the wastegate and open another valve that defers exhaust pressure from the turbine. The pressure from the cycling valve comes from a hose connected to the intercooler pipe.
Oil is a major player in turbocharged engines(like most engine) for the reason that the turbo gets extremely hot and oil "cooks" and thins or breaks down the viscosity that in turn reduces the oils ability to lubricate the engine.
I'm sure I'm beating a dead horse and I'll let the other guys help... and I'm tired