View Single Post
      09-30-2012, 05:00 AM   #383
NISFAN
Brigadier General
NISFAN's Avatar
England
67
Rep
4,245
Posts

 
Drives: The best kind of F30 :)
Join Date: Aug 2012
Location: Bedford UK

iTrader: (0)

Quote:
Originally Posted by swamp2 View Post
No backwards, first lag is the phenomena, not the revs (as you explicity state) and it is not the rev range when "boost" is produced but the phenomena when "boost" is not being produced but being requested.
Yes, exactly....people expect boost from idle to red line.

Where they feel the biggest deficit of boosted power is just off idle. This is not lag, this is a Turbo below it's boost threshold. i.e. in a rev range where the turbo is not getting enough exhaust energy to produce positive boost. If the engine were kept below this threshold boost would never be produced.

Quote:
Originally Posted by swamp2 View Post
No one knows the exact quantity, arrangement, size nor much else about the new cars FI system. The biggest variable will be the presence or absence of some sort of electric turbo or other lag reducing technique.
This statement proves how common the mis-labeling of 'LAG' is. This electric tri turbo arrangement will be to reduce boost threshold, not to counter lag, but as the common misconception is that lag is boost threshold it gets labelled as an anti lag device.


Quote:
Originally Posted by swamp2 View Post
Not quite. The S65 has one of the broadest and flattest torque bands around. With a good turbo you get more torque at low rpms, good from a dig or for pulling stumps but not what makes a car the most exciting nor the most potent at the track. Turbos then generally can not keep up their performance to a very high redline thus their band width suffers.
Right I need to explain this better. Lets say you take an S65 engined M3 and turbo charge it. You leave everything about the engine exactly as it is, cams, compression ratio, everything. But you now have a large sized turbo that comes on boost (the boost threshold thing once again) at 4000rpm, and runs hard til the redline.

Now if you were to drive this Turbo S65 M3 you would get used to the intoxicating power that the turbo produces. After a few hours behind the wheel you would start to notice the how poor the response is below 4000rpm. This is your same beloved S65 but without boost, that seemed to have a lovely spread of torque, but now feels flat un boosted.

This is what I mean, a Normally aspirated engine has lag all the way to the red line, as it never gets that high torque boost hit.


Quote:
Originally Posted by swamp2 View Post
That's nonsense. Anyone who says that a very sporty engine like the S65 suffers from lag is utterly confused about lag.
Make sense now?