Is it Turbo Lag?

I have been enjoying my 02 A4 Avant 1.8T 5 spd for about six weeks now. If I start off spirited, the car moves our alright, then at around 3k rpms it
snaps me back into the seat, and I have to back off before I shift. I am guessing this is what is known as turbo lag. It's kind of an awkward sensation. Is that typical of these 1.8 T engines? I am wondering if it needs to be checked out. Thanks in advance. - Len
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No mate, turbo lag is where you plant your foot & nothing happens for a second or two then whhoooshhhh! It's mot as bigger problem now as on old Saab's etc. What your are experiencing is some kind of overrun for emissions or some other bloody annoying crap reason!!
My wife's A4 Cab does the same thing & I hate it for that reason only.
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Sounds exactly like turbo lag to me. Some manufacturers get around it by adding a small turbo (in addition to the regular big one) that spins up quickly despite the slower exhaust velocity at lower rpm. Audi on their 2.7T uses two of the same size, but that engine has enough displacement to provide decent torque even at low rpm. And with each turbo filling just one bank of 3 cylinders, each one can be small enough to compress air at lower rpm while being big enough to compress air at the redline. Engine design is full of compromises.
When you say you 'start of spirited' I'm guessing you use some clutch slip to get and then keep the engine near 3000 rpm - until the clutch fully engages and you floor the throttle. If you don't, that's one way to increase the exhaust velocity enough so the smallish motor doesn't spend much time fighting to breathe well. You'll typically get the best acceleration numbers this way. It's also an excellent way to decrease the life of your clutch if done poorly.
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I'm very judicious with my clutching. I'm not letting it slip like you suggest. I usually am off the pedal asap. The same takeoff happens in all the gears when the engine gets around 3000, but it is most prominent in 1st gear.

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Len S. wrote:

That's the way turbo lag will seem the worst, but when it spools up near 3k rpm, the 'turbo smile' feels the best because of the dramatic difference.
The fact you feel the same effect in each gear confirms it is turbo lag and therefore nothing to worry about unless it changes as the miles go by.
The lag of the 1.8T actually isn't nearly as bad as early turbo cars from the 1980s. Those engines had _nothing_ below a certain rpm, but once it kicked in the rush was often violent and had somewhat unpredictable effects on handling, especially if you were exiting a turn where smoothness was key to good lap times.
Enjoy.
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Probably also means he's changing up too early. Keep it on boost!!
andyt
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Thanks for the information. - Len

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Bear in mind that -- unlike a torquey, beefy V8 such as the one found in the '04 S4 -- the smallish, 1.8T engine works best above 1950RPM, at which point the turbo is fully spooled up. Also, if you had a larger engine previously (mine was a 3.0L V6) you may be alarmed that optimal cruising happens at what you might consider high RPM's. I typically downshift at 2.5K, and upshift around 4.5K, and cruise on the highway at well above 3K. I still get 28mpg.
When I first got my '02 A4 I was alarmed because I was used to shifting much lower, and cruising much lower. These days it's just another way to enjoy the pleasant exhaust note.
--Cesar
wrote:

= Cesar Borgia
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Well, I am definitely guilty of shifiting up at rpm's lower than you use (usually around 3k) and downshift around1.8 to 2k. This car is so easy to just go sailing way past the speed limit, so I guess I'm just being careful, and in doing that, I am ending up shifting just before the real fun starts. Are you sure the turbo is fully spooled that low (1950k)? I figured the push I described in the beginning post was the point where the turbo is fully spooled. Maybe it is just the point where the gate fully closes and gives all the boost. - Len

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fun
<Much snippage>
http://tinyurl.com/33j42 shows a comparable power curve (IIRC, the TT225 has a less peaky power curve than the 180, so the torque will be even lower) I'd say that 3000rpm is basically just getting onto the torque curve (around half of the rated power output of the engine..)
Quite a few rechips lower the point where the boost comes in (mine does the opposite, which I prefer, in terms of engine response - it feels much more like the 180 I originally test-drove. I know that this sounds odd, but a sharper curve and higher peak power /feels/ sportier, if you're more used to tuned normally-aspirated engines)
H1K
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I have doubts that the car has been chipped. As far as I know, the car was a lease return and was registered in Connecticut. Why would somebody mod their car when it is not really theirs does not make sense. A friend of mine has a 99 A4 and he says that his turbo kicks in at around 4k. I don't know if that even merits comparison.
I am thinking that it is just a matter of me getting acclimated to the cars abilities and limits. It is after all just a 4 cylinder engine and it's an avant (heavier than the sedan). To expect super performance is not realistic. Expecting good performance is more like it. I still love the car.
Thanks for all the responses. There's a bunch of good people in this ng. I appreciate it. - Len S.

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wrote:

I have a 2004 1.8q and always drive in Tip mode. When I am in 2nd I can feel a little 'bump' at around 2800 rpm or so and then I go to 3rd. I thought this was the lag.
What is happening in 2nd then as I go thru the bump?
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Len S. wrote:

Your turbo charger doesn't kick in until around 3K rpm.
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If
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"Turbo lag" is the bit that happens /before/ 3k rpm*
The "problem" you're experiencing is "Turbo smile" ;o)
--

Hairy One Kenobi

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Well then, I guess having a happy turbo is not such a terrible thing, eh? Turbo smile ... hmmm. So it's not a problem, it's a feature?

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Len S. wrote:

If you have had an 02 for only 6 weeks, this strongly implies that you bought it used.
Could the previous owner possibly have installed an aftermarket 'chip' for the ECU? That would certainly create more non-linear power delivery curve than would stock tuning.
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Hi Len,
What you are experiencing is what's known as "boost onset". The turbo will spool then begin to deliver a massive amount of air beginning a few RPMs before making power. Turbo lag refers to how long after spooling to when the engine really begins to make lots of power. It can occur at any RPM point prior to loading (mashing the gas) the engine, including well above the boost onset RPM.
What you feel is normal for a turbo car. It's the reason for "turbo smile" and the "turbo smile" is why I will forever buy turbo cars.
-Guy 02 S4 02 WRX

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