Quote:
Originally Posted by Boss330
NISFAN: It seems you are debating two different issues as one. Turbo lag and whether a turbo engine makes more power...
No one claims that a turbo engine does'nt make more power. It DOES! That's why they can downsize to a 3l engine and make a quicker car. Just as with the E60 vs F10 M5. It's just that the power delivery isn't as instant in a turbo engine.
To quote CAR on the Audi S4: "throttle response that could only be achieved on a turbo-free motor."
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Well the two points are this:
If I take an NA engine and turbo charge it. The throttle response will be EXACTLY the same as it was in NA form. In other words the torque curve will be identical.....until.....the turbo starts producing positive pressure. So where is the lag?
Of course this config will be significantly more powerful than the NA it was based on.
So second option is to make an x powered engine to equal an an x power NA. This will be based on a smaller displacement engine + turbo. Yes of course the non boosted torque curve will be the same as an NA engine of same displacement (trying not to complicate things, but actually a boosted engine can run smaller duration camshafts that will promote higher torque lower down in the rev range). Only in this scenario, will a guy used to 4 litres feel let down by the lower (due to smaller displacement) torque values, until boost is held.
Example 1 Now dyno runs on turbo charged engines show that lag is at it's worst when you go from idle WOT. In this scenario, a.) turbo speed is as low as it can be b.) engine flow is low to start with, mostly likely below boost threshold any way.
Example 2 Opposite scenario is torque being controlled at high'ish revs (for example holding road speed mid corner on long sweeper, part throttle), then going WOT. Here turbine speed will be high to start, and exhaust gas will be high to energise the turbo. Lag in this scenario could be as little as 0.1 second.
The biggest road user complaint is that the turbo doesn't spool instantly when going for a lazy no gear change. Sure you are putting the engine into Example 1 territory. Drop a gear or two and you edge towards Example 2. You control the lag. This delayed acceleration is not much different to an NA, trundle along in an s65 M3 in 6th gear manual at 30mph, floor it and nothing much happens.
So you can see that lag depends on how you look at an engine turbo combo. Sure there is a delay before boost is produced on WOT, but torque is identical to an NA version of the same engine.
This reinforces my point that an NA has lag all the way to redline, because the boost never comes no matter how hard you rev it or push on the throttle. Yet NA enthusiasts bang on about Turbo lag. To me Turbo lag means that the engine has a turbo, which is a great thing. It means you are extracting as much power out of a set of internals as you possibly can.