Car for high hills

[henk4]

Originally Posted by nota

why would a supercharged engine have any lag at all?

why are we not all supercharged then?

[LeonOfTheDead]

A bit of lag is present on supercharged engines, as the compressed air you are using is the result of the previous cycles (as on a turbocharger) and revs (so the compressor is always a bit late on the demand), still the lag is minor than on a turbocharger.
On the other hand, SC suffers for a quick fall in power at high revs, especially after the point of maximum power.
In all engines the power curves is more steep after the point of maximum than before, so if you consider that a SC is mechanically powered connecting it to the main shaft (directly or not, doesn't matter) and that the power it requires is more constant than the one the engine delivers, that means at higher revs you are using a larger part of power than at lower revs.
Therefore SCs aren't suitable for high revving engines, generally, but afaik they produce less boost than TBs, or better, it's easier to get an higher boost with a TB than with a SC.

Somehow this explains why on mixed layouts (using both systems) the SC is use at low revs and the TB at higher ones.

[Man of Steel]

Originally Posted by LeonOfTheDead

A bit of lag is present on supercharged engines, as the compressed air you are using is the result of the previous cycles (as on a turbocharger) and revs (so the compressor is always a bit late on the demand), still the lag is minor than on a turbocharger.
On the other hand, SC suffers for a quick fall in power at high revs, especially after the point of maximum power.
In all engines the power curves is more steep after the point of maximum than before, so if you consider that a SC is mechanically powered connecting it to the main shaft (directly or not, doesn't matter) and that the power it requires is more constant than the one the engine delivers, that means at higher revs you are using a larger part of power than at lower revs.
Therefore SCs aren't suitable for high revving engines, generally, but afaik they produce less boost than TBs, or better, it's easier to get an higher boost with a TB than with a SC.

Somehow this explains why on mixed layouts (using both systems) the SC is use at low revs and the TB at higher ones.

If I could only understand half of that I would consider myself a pretty 'technical' man. Frankly I don't know sh*t what is going on under the bonnet. I should follow a technical course for cars (dummy level) of some sort... Ever

[drakkie]

Originally Posted by Man of Steel

If I could only understand half of that I would consider myself a pretty 'technical' man. Frankly I don't know sh*t what is going on under the bonnet. I should follow a technical course for cars (dummy level) of some sort... Ever

If you like, you can borrow an excellent book from me. I saw you live in the neighbourhood so.. PM me if you like to!

[nota]

Originally Posted by LeonOfTheDead

A bit of lag is present on supercharged engines, as the compressed air you are using is the result of the previous cycles

Inside a supercharged engine at merely 600 rpm, that 'previous cycle' was about 0.4 seconds ago..

[LeonOfTheDead]

Originally Posted by nota

Inside a supercharged engine at merely 600 rpm, that 'previous cycle' was about 0.4 seconds ago..

that's quite a lag, not only from an engineering point of view.
Also, is there any modern engine idling at 600 rpm?
Surely not from the EU market, afaik, would be a nightmare for the Euro (insert here the number you prefer) emissions level as the combustion would be quite, well, shitty, especially in smaller engines (unitary displacement I mean).

[nota]

Originally Posted by LeonOfTheDead

that's quite a lag, not only from an engineering point of view.
Also, is there any modern engine idling at 600 rpm?

I was using 'worst case' but ok lets try this 'previous cycle' lag at a still-low 2,400 rpm .. about 0.1 seconds!

Hardly discernable imo

Surely not from the EU market, afaik, would be a nightmare for the Euro (insert here the number you prefer) emissions level as the combustion would be quite, well, shitty, especially in smaller engines (unitary displacement I mean).

Doesn't EU market have any supercharged vehicles?

[ronbros]

WELL! at least you guys agree that it should be a PRESSURIZED INLET SYSTEM.

[LeonOfTheDead]

Originally Posted by nota

I was using 'worst case' but ok lets try this 'previous cycle' lag at a still-low 2,400 rpm .. about 0.1 seconds!

Hardly discernable imo

Doesn't EU market have any supercharged vehicles?

I was thinking about cars with such a low idle, and btw, supercharged vehicles are quite a few over here.
BTW, 0.1 secs as a lag can be almost invisible for the driver, and indeed SC cars suffers of a very limited lag (still technically present isn't it), but if you consider that a full cycle at 2.400 rpm last about 0,05 secs, but in that range f time the actual rpm can very substantially, you just can't avoid the lag while accelerating. Basically inexistent for the driver, I completely agree, still it contributes, together with the always present ECU, to create the feeling of a disconnection between what you do and what the car does.

If 0.05 secs weren't a problem, then why to bother with ultra fast gearboxes?! The answer is marketing, I know, couldn't care less about those paddles, still it's something people bother (even if they perhaps don't know what they are doing).
I agree with you Nota, and once another evidence the SC lag is very small is that, even at low rpm, it is preferred to a TB.
In this situation both systems are working in the worst conditions, still the SC is the quicker to react, and probably the more efficient of the two given we are talking about similar similar engines and layouts.


What surely helps a SC system is that it isn't influenced by how much load you're applying/asking, but just on the revs.
For a TB being at 3.000 rpm staidly or while fully accelerating is completely different as the exhaust fumes are completely different in their quality and quantity (as you are on a different power curve), while for the SC 3.000 rpm are just that.

Originally Posted by ronbros

WELL! at least you guys agree that it should be a PRESSURIZED INLET SYSTEM.

or a very large and torquey engine, in the good old American way I guess.

[ronbros]

MY VOTE! go for a good turbodiesel

[Ferrer]

Originally Posted by nota

Doesn't EU market have any supercharged vehicles?

Jags, Mercs, Lotuses and Audis off the top of my head.

I personally prefer thw throttle response of a supercharged car, but I'm certainly nowhere near as technical as Damiano...

[LeonOfTheDead]

Right, Audi uses SCs, forgot about them.I may be wrong, but I guess MB is the one using SCs on the smaller engines (considering normal cars, so no Lotus here).
VAG has the 1.4 liter, btu that's an hybrid (SC + TB).
anyone else?

Lately I can't bother anymore reading magazines and press releases.

[nota]

Originally Posted by LeonOfTheDead

I was thinking about cars with such a low idle,

In 'drive' my old Merc V8 idles at 550~600 rpm, with good oil pressure!

BTW, 0.1 secs as a lag can be almost invisible for the driver, and indeed SC cars suffers of a very limited lag (still technically present isn't it), but if you consider that a full cycle at 2.400 rpm last about 0,05 secs, but in that range f time the actual rpm can very substantially, you just can't avoid the lag while accelerating. Basically inexistent for the driver, I completely agree, still it contributes, together with the always present ECU, to create the feeling of a disconnection between what you do and what the car does.

If 0.05 secs weren't a problem, then why to bother with ultra fast gearboxes?! The answer is marketing, I know, couldn't care less about those paddles, still it's something people bother (even if they perhaps don't know what they are doing).

As you say, 0.05 happens so quick it is basically beyond human perception, and btw is incomparably less lag than you get through torque converter slip. Anything much less than a second is a non-issue imho.

I wouldn't be surprised if there's more inbuilt 'lag' in the (flexible) engine mounts than 0.05~0.01

[wwgkd]

As long as we're discussing supercharged engines I have a question that's been bothering me for a while. As was mentioned earlier they don't work as well at high rpms, so why does the Caterham Levante with a 10,500 rpm redline and the Lotus Elise/Exige with close to it use a supercharger? I understand the fact that it minimizes lag but it seems like effeciency at those higher rpms would be a bigger issue, yet it does seem to work fine.

[Ferrer]

Originally Posted by wwgkd

As long as we're discussing supercharged engines I have a question that's been bothering me for a while. As was mentioned earlier they don't work as well at high rpms, so why does the Caterham Levante with a 10,500 rpm redline and the Lotus Elise/Exige with close to it use a supercharger? I understand the fact that it minimizes lag but it seems like effeciency at those higher rpms would be a bigger issue, yet it does seem to work fine.

Guessing, ease of installation?