Janet

I have to admit some technical ignorance tonight. I've read posts about "turbo lag" without really knowing how to recognize it. My 180Q is my first turbo-charged car.

During my pm commute, when I was in a bit of a hurry, I made a VERY quick left-hand turn across 2 lanes of traffic with a car approaching fairly quickly. I feel like I "know" my TT well enough by now to have a better idea of how close I can cut it when I'm driving....my odometer turned 2500 miles today.

WELL..."Fritz" performed pretty much as expected when I hit the gas...hard...as I made the turn. But after a second or two, I suddenly felt like I was down at NASA testing my body's reaction to high G's or something. SOMETHING (the turbo, maybe?) kicked in big time and I was simply FLYING down the street at a rate of acceleration I haven't experienced before! I don't think I've ever stepped on the TT's gas that hard, starting out in 1st gear, so I hadn't felt that sensation before. I was a little startled...but thrilled at the same time!

But it is the one or two-second lag which I'm curious about. Do you think I experienced the 180Q's famous "turbo lag" which you guys mention with such regularity?

Thanks...

Janet
'00 180Q

AkRascal

Y U P

L Mies

As the current driver of a SAAB 900 turbo, I'd have to say that's a pretty good description of turbo lag. I don't know first hand (yet) how much the TT's drive-by-wire system masks the effect in normal driving, but in the SAAB, one has the unmistakable impression that the engine is doubling in size as it passes through 3000 revs, and the turbo spools up.

The other side of this coin is that if you're caught if 5th gear at 1500 revs, with a truck about to crush you from behind, the trip up to 3000 revs seems to take a rather long time.

Jonathan

"Turbo Lag" is the transition from zero-boost to full boost -- in the TT, Audi has attempted to keep this to a minimum by using two small turbochargers rather than one large one (because there is less mass in two small fan blads versus one large fan blade, they should be able to spin up quicker than a single large turbocharger)

Normally the engine control unit eases the speed of the turbocharges up gradually, so you don't notice a sharp transition between zero boost (when you're idling there's no point in shoving more fuel into the engine) and full power. However, if you punch the throttle from idle, there is still a small delay before the turbos spin up and start cramming fuel into the system.

That's essentially what happened when Franz decided to say "hello".

It would have been a rougher transition with a larger, single turbo unit. The nice thing about the TT is more the many conditions under which you will _not_ feel any significant turbo lag, leaving a only a few conditions where you will experience a large amount of lag.

Jonathan
'00 180q

Jenner

The 180TT only has ONE K03 turbo. The 225 has ONE K04 turbo. Where did you get TWO from?!??

HokieTT

Them sounds like downshiftin' words! (nt)

L Mies

... for the reason stated. Simple mistake. Lighten up.

Jenner

Somehow I missed the mention of the S4 in the previous post by Jonathan, where was it?

Janet

Yes, I WAS accelerating essentially from "idle", after waiting for someone else to turn first.

Jonathan

My models mixed, but the lag stuff is still valid -- small turbochargers spool up faster, and therefore you get less lag. Ergo, if the 225's have K04's, (and I'm assuming that these are larger, in order to cram more fuel into the same size engine) then it's highly probably that they will experience slightly more turbo lag than the 180's.

The other thing that will reduce turbo lag is to incrimentally apply boost -- rather than turn the boost pressure on full bore like a light switch, bring it up gradually like a dimmer switch. That way lag is diminished because the turbos have fewer RPM's to increase to get to full pressure from any point, and the power produced by the engine as it revs up is more consistent. You still get the same amount of peak power, it's just accessable in less time and spread out more evenly over the power band.

Car & Driver did an interesting comparison a while back about aftermarket chips, and chose to do all of their experimenting on normally-aspirated vehicles, as turbocharged vehicles lend themselves well to performance gains simply by increasing the boost pressure. I think of this much like overclocking a PC -- you hear about the success stories ("I just tell it to go faster, and it does!") but you don't hear much about the cost because people feel silly when they melt their toys. Granted, there are some pretty serious gains to be made by doing this, so perhaps I'll look into a chip in a few years --I've little interest in voiding the warranty I purchased before getting all of the trouble-free miles that I was promised. 48,300 to go!

Jonathan
'00 180q<ul><li><a href="http://www.caranddriver.com/FrameSet/0,1350,_sl_NewArticle_sl_0_cm_1633_cm_2323_1_16_cm _00,00.html">Car and Driver interesting review of aftermarket chips</a></li></ul>