Prove my Dad wrong
Discussion
My Dad has a E39 touring 530d (M sport).
His major criticism is the turbo lag, mainly from a standing start. For example, getting into gaps on roundabounts. He asks, why can't BMW etc install a reservoir of compressed air to drive the turbo in the absence of exhaust gas flow to drive the turbo?
My answer is that the required volume of air would dictate an unfeasibly large pressure vessel to be held somewhere in the car... but we can't begin to determine how big, or at what pressure, such a vessel would need to be.
Can you?
P.S. Yes, my first answer was "if that's what you want, buy a S6 petrol" and my second answer was "better planning".
Edited for pedantry, my mistake.
His major criticism is the turbo lag, mainly from a standing start. For example, getting into gaps on roundabounts. He asks, why can't BMW etc install a reservoir of compressed air to drive the turbo in the absence of exhaust gas flow to drive the turbo?
My answer is that the required volume of air would dictate an unfeasibly large pressure vessel to be held somewhere in the car... but we can't begin to determine how big, or at what pressure, such a vessel would need to be.
Can you?
P.S. Yes, my first answer was "if that's what you want, buy a S6 petrol" and my second answer was "better planning".
Edited for pedantry, my mistake.
Edited by goneape on Saturday 14th March 07:22
goneape said:
My Dad has a E39 touring 330d (M sport).
No he doesn't.Pedantic s aside, maybe it could be possible, in theory. you'd simply run a very, very high pressure to meet the challenge of size.
But the real question is why bother, there are other anti lag systems out there, or by a twin turbo 535d/335d etc.
WRC teams played around with it - Ford example here and I'm sure Subaru tried similar too.
https://www.highpowermedia.com/blog/3808/the-surge...
https://www.highpowermedia.com/blog/3808/the-surge...
One of the ideas in the Koenigsegg camshaftless technology http://www.cargine.com/ is to use the engine as compressor to store air in a pressure vessel that can be used to provide 'boost' before a turbo spools up.
Something like that anyway, I read it a few years ago.
Something like that anyway, I read it a few years ago.
They often get around the problem these days with twin turbo chargers a light pressure and high pressure working at different revs and loads.
Formula one engines have electrically controlled turbos to reduce lag. They utilise the energy recovery systems known as MGU-H which is effectively an electric motor joined often via a shaft through the V-Valley to the Turbo charger on the other end of the engine. By controlling the current flowing through the motor you can effectively spool up or stall the turbo charger or vary boost output. If you've seen the size of the turbo compressor housing on current F1 engines you'll know why they need this to combat lag - they are simply enormous! Undoubtedly, this will be a system that will make its way onto production cars in the future.
Formula one engines have electrically controlled turbos to reduce lag. They utilise the energy recovery systems known as MGU-H which is effectively an electric motor joined often via a shaft through the V-Valley to the Turbo charger on the other end of the engine. By controlling the current flowing through the motor you can effectively spool up or stall the turbo charger or vary boost output. If you've seen the size of the turbo compressor housing on current F1 engines you'll know why they need this to combat lag - they are simply enormous! Undoubtedly, this will be a system that will make its way onto production cars in the future.
goneape said:
My Dad has a E39 touring 330d (M sport).
His major criticism is the turbo lag, mainly from a standing start.
Is it auto or manual and it it broken? Compared to other Tdi's of the era, the 6 cyl 3l in the E39 has very little lag and a relatively low boost threshold, because it is generally speaking, about a litre of swept capacity bigger than most other dervs (they being 2.0 litre engines). Yes, there is some lag, and you have to have the engine spinning at say 1800rpm to get a swift getaway (if it's auto, it always will be thanks to the Torque convertor slip ratio), but i can't say i've ever noticed a significant problem with that engines response?His major criticism is the turbo lag, mainly from a standing start.
Thanks for the pedantry etc. Yes these days the hybrid stuff meets the need better, but I can't see him cashing in his investments for a 918 any time soon. I wasn't aware of the WRC stuff, that was really interesting. It looks like it comes down to the usual trade off of good enough for 95% of the market vs. The expense of making it perfect. The best solution seems like a trade in for a twin turbo model, if it's that big a deal.
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