RE: 'Beyond 400hp' Mercedes-AMG A45 caught testing
Discussion
petrolhead4 said:
No doubt Mercedes will make this engine strong enough to deliver 100,000 miles or more.
I do wonder however whether the 9-speed gearbox has been chosen and calibrated especially to minimize the turbo lag that must come from such a highly boosted engine, and more critically just how responsive can this engine be in manual mode?
Your better off leaving the DCT in auto mode.I do wonder however whether the 9-speed gearbox has been chosen and calibrated especially to minimize the turbo lag that must come from such a highly boosted engine, and more critically just how responsive can this engine be in manual mode?
The A45 has the AMG Speedshift version of the DCT which changes gear in 0.1 seconds. Ive got one and its brutal.
Manual mode is pointless. The computer does a better and quicker job than me.
Saabaholic said:
petrolhead4 said:
No doubt Mercedes will make this engine strong enough to deliver 100,000 miles or more.
I do wonder however whether the 9-speed gearbox has been chosen and calibrated especially to minimize the turbo lag that must come from such a highly boosted engine, and more critically just how responsive can this engine be in manual mode?
Your better off leaving the DCT in auto mode.I do wonder however whether the 9-speed gearbox has been chosen and calibrated especially to minimize the turbo lag that must come from such a highly boosted engine, and more critically just how responsive can this engine be in manual mode?
The A45 has the AMG Speedshift version of the DCT which changes gear in 0.1 seconds. Ive got one and its brutal.
Manual mode is pointless. The computer does a better and quicker job than me.
And turbo lag is practically non existent even in Sport mode, and definitely so in Sport+ and Race modes.
227bhp said:
Long stroke engines do not make more torque, no matter what you do with the stroke and bore if the rest of the spec (including CC) stays the same so will the maximum power/torque output.
A shorter stroke engine WILL rev further because the piston speed will be lower than the long stroke version. That's why F1 engines have very short stroke and wide bores - to allow them to rev to very high rpm.
Correct, purely on geometry with equal displacement, a longer stroke engine does not produce more torque. But usually within the margins of automotive turbocharged engines with small differences is bore/stroke, since long stroke doesn't rev as high for several reasons (higher inertial stress and smaller valves), they are usually tuned for lower down torque which works well as piston speeds and efficiency are higher. So in the end they usually are equal within the margins of consumer engine tuning. But ultimately a higher revving engine most definitely will produce higher power if that is the goal, however at a cost of efficiency and nowadays one usually rather resorts to higher boost pressures as these don't penalise efficiency as much. But where such doesn't matter, like bike engines, they run 200hp/l without FI, they simply rev about twice as much with a stroke almost half the bore... A shorter stroke engine WILL rev further because the piston speed will be lower than the long stroke version. That's why F1 engines have very short stroke and wide bores - to allow them to rev to very high rpm.
mwstewart said:
I suggest you get with the times and have a read about ion sensing technology.
Pre-ignition and knock can be considered the same thing for what we are discussing here: a limitation in peak power due to elevated combustion pressure or extremes of temperature.
No they cannot be considered the same thing, the subject is still studied in great lengths, and no sensor on earth can predict the onset of knock, once the conditions that trigger knock or super-knock occur in a gas mixture, it is too late to stop it.Pre-ignition and knock can be considered the same thing for what we are discussing here: a limitation in peak power due to elevated combustion pressure or extremes of temperature.
The Ion sensor and anti-knock strategy adopted in EFI systems are reactive, knock occurs before anything can be done about it.
Keep reading glossy german car brochures if that makes you happy, but don't try to publicise on a forum arbitrary soundbites of information as some sort of conclusive statement on what is a complicated subject.
Edited by TwinExit on Monday 12th November 13:32
Onehp said:
227bhp said:
Long stroke engines do not make more torque, no matter what you do with the stroke and bore if the rest of the spec (including CC) stays the same so will the maximum power/torque output.
A shorter stroke engine WILL rev further because the piston speed will be lower than the long stroke version. That's why F1 engines have very short stroke and wide bores - to allow them to rev to very high rpm.
Correct, purely on geometry with equal displacement, a longer stroke engine does not produce more torque. But usually within the margins of automotive turbocharged engines with small differences is bore/stroke, since long stroke doesn't rev as high for several reasons (higher inertial stress and smaller valves), they are usually tuned for lower down torque which works well as piston speeds and efficiency are higher. So in the end they usually are equal within the margins of consumer engine tuning. But ultimately a higher revving engine most definitely will produce higher power if that is the goal, however at a cost of efficiency and nowadays one usually rather resorts to higher boost pressures as these don't penalise efficiency as much. But where such doesn't matter, like bike engines, they run 200hp/l without FI, they simply rev about twice as much with a stroke almost half the bore... A shorter stroke engine WILL rev further because the piston speed will be lower than the long stroke version. That's why F1 engines have very short stroke and wide bores - to allow them to rev to very high rpm.
A 4 stroke engine relies on the piston to travel end-to-end of its travel to initiate and complete the phases to generate force at the transmission. The more distance a piston must travel, the more time it takes at a given piston speed to fill the cylinder with fresh gas charge, or discharge exhaust gases, or compress the mixture, and so forth. For an engine to INCREASE RPM (and thus accelerate/propel the car) combustion pressure must exceed the load / resistance at each combustion event, and every cycle the piston travels up and down over a greater distance which implies more time taken at each phase as it reaches the end piston speed at given end RPM.
Engine power is measured in different ways and one of the most misleading methods is the 'inertia' dyno where many 'long stroke' cars report higher WHP figures than what is estimated from the factory rating.
When placed on a load cell type dyno (which uses similar principles to engine dynos used by the likes of 99% of car makers), it spits out WHP readings that fall very close to the factory rating. Short stroke (sub 80 mm) motor'd cars will show similar numbers across different dyno types providing external ambient and fueling conditions are constant.
Edited by TwinExit on Monday 12th November 13:55
Merc are getting into a power war they can’t win imo.
As long as Audi keep the current 2.5 then they can keep making minimal tweaks to stay one step ahead, there was a pre facelift RS3 8v making 675bhp with standard internals and gearbox quote reliably on the Audi forums and with the facelift in the states people are running the same with a bigger turbo bolted on and Intercooler and away you go.
As long as Audi keep the current 2.5 then they can keep making minimal tweaks to stay one step ahead, there was a pre facelift RS3 8v making 675bhp with standard internals and gearbox quote reliably on the Audi forums and with the facelift in the states people are running the same with a bigger turbo bolted on and Intercooler and away you go.
Chazclark said:
Merc are getting into a power war they can’t win imo.
As long as Audi keep the current 2.5 then they can keep making minimal tweaks to stay one step ahead, there was a pre facelift RS3 8v making 675bhp with standard internals and gearbox quote reliably on the Audi forums and with the facelift in the states people are running the same with a bigger turbo bolted on and Intercooler and away you go.
You think AMG cant "win" a power war?As long as Audi keep the current 2.5 then they can keep making minimal tweaks to stay one step ahead, there was a pre facelift RS3 8v making 675bhp with standard internals and gearbox quote reliably on the Audi forums and with the facelift in the states people are running the same with a bigger turbo bolted on and Intercooler and away you go.
OK....
Besides, this incremental power race simply means that both brands end up in the headlines when the latest variant is released.
There are reasons to buy each rather than just outright power anyway....
Advevo said:
I might be interested in this car.
But
Can you leftfoot brake and use throttle on same time.
Does the 4wd system disconnect when using throttle and brake same time.
Does it have mechanical diffs. I really want no ediff braking one wheel.
Yes you can left foot brake. The wife does it all the time. But
Can you leftfoot brake and use throttle on same time.
Does the 4wd system disconnect when using throttle and brake same time.
Does it have mechanical diffs. I really want no ediff braking one wheel.
No idea about the other 2 questions.
Drive one and see, they are superb.
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