I know there is a supercharger kit for the A4 2.8. I just want to know if there is a turbo kit available and who makes it. Thank you.

It all depends on how well set up the turbo system is. A properly matched turbocharger with an intercooler and properly redone fuel system (larger injectors, re-programmed ecu) should produce more overall power without much noticable lag. Compressor type superchargers produce no extra power on the low end, but lots on the high end (usually 4000+ rpm). Positive displacement superchargers (like the PES) produce lots of bottom end torque, but are relatively inefficient, and produce less power at high rpms due to excessive heating of the intake charge. Turbochargers offer good lower-rpm response (if properly sized, lag shouldn't be much of an issue for a street turbo system) and lots of top end power, without any parasitic drag. On the down side, turbocharger systems are more complicated, thus require more engineering, thus are more expensive to buy and maintain. But for ultimate power/efficiency for the street, you can't beat a nicely done turbo :) (been thinking about getting one for my M3...am I insane???)<p>Brad

The Eaton supercharger that the PES kit uses is supposedly quite efficient (relative to other superchargers). It creates very little drag and has a bypass valve for increased fuel efficiency, which is why it has been pretty much the only unit used in OEM applications for major auto makers. <p>The PES kit would make more efficient power with an intercooler, but there is simply no room to easily fit the piping. There would be much more room to fit an intercooler with a turbo kit (since the physical size of the turbo compared to the s/c leaves much more room available in the engine compartment for intercooler piping), which would be an advantage. HOWEVER, the real beauty of the supercharger kit is the fact that it is a true bolt-on kit that provides power where it is used the most on the street. So, while the end result of a turbo may be as good or better than the PES kit, a turbo kit would be a much more involved undertaking, requiring oil and coolant supplies, custom exhaust manifolds, etc. Comparatively, the PES kit is a walk-in-the-park. A handy fellow could get it installed in a day in their driveway.<p>Lastly, why do you say that the positive displacement superchargers excessively heat the intake charge at high rpm? I didn't think this was the case, but I am no expert.<p>Mike

Ain't I a stinker? ;-)<br>

I'm always interested in reading posts about the PES because I intend to get it within the next couple of years after I take care of some other issues. How handy does one have to be to install it in a day? I can bolt and unbolt too, but I'd be working solo. My biggest concern is getting halfway through the job, then getting into a jam, necessitating a call to my friendly Audi dealer to undo everything I've worked on. What about hiring a reliable or recommended local mechanic? Thanks in advance.<p>98.5 2.8 30v tipqs

If you want simple installation and a big power boost, superchargers are the way to go. BUT<p>Positive displacement superchargers are less efficient by a significant margin over compressor type setups (like compressor type superchargers and turbochargers). The positive displacement superchargers use some way or another to actually squeeze or push the air into the engine. I believe the Eaton unit used in the PES system is a 'roots' type, the least efficient....but hey it does it's job well! (heck that's all they use on the top fuel dragsters). Other positive displacement 'chargers like the whipple (two screws used to push the air) are more efficient, but also more expensive. "efficiency" essentially refers to how much extra heat energy is transferred to the intake charge during the process of forcing more air into the engine. The roots type uses two interleaving rotating lobes to push air into the engine, which also tends to 'beat up' the air as it goes, sorta like the mixer you have in your kitchen. This heats up the air (theoretically, if you had a high enough setting and really big fat mixing extensions on your mixer, you can heat up your batter too :) The 'beating' effect obviously increases as supercharger speed/engine speed increases.<p>Compressor type setups tend to throw, or accelerate air so that it compresses against the outer edge of the compressor housing. This method produces much much less heat. I guess a good analogy is - would you rather slide down a big ramp, launched through the air, into a net (compressor type) - or would you rather be hit by a fast travelling bus and knocked through the air into the net (roots type)? <p>The more heat, the less dense the air intake charge (less air means less power), and also more combustion chamber heat, which can cross that fine line between lots of power and lots of detonation. Wow this message is getting really long - bottom line, I'm an M3 driver and I've talked with guys who have owned/driven supercharged M3's and Turbocharged M3's. They always say the supercharged M3 is very fast and smooth, but they also say the Turbo M3's will shred the tires and rip heads off...I know which one I would prefer :) Hope this helps explain my reasoning some more...<p>Brad<p>

Still the Turbochargers do not have the low-end grunt that the S/C has. And IMO, the low-end is what the A4 needs most in the 2.8. In stock form, it really doesn't begin to pick up steam until around 3k rpm. Plus, on street race, light to light, the low-end power (off the line) is what's going to count the most. For the M3, Turbo's may be the way to go, as I believe they have plenty of low-end even in the stock engine.... even the 328i's are this way.<p>G. Hale<br>'98.5 2.8 QMS

I wouldn't do it alone, as an extra set of hands makes it "much" easier. However, if you have a mechanically inclined friend, it isn't that difficult. Anything that is "done" can be fairly easily "undone". Regardless, plan on taking an entire weekend, as it isn't something that is worth rushing. <p>The directions are very thorough, and include 3 to 4 illustrated photos on each page. They are very explicit and take you through the install step-by-step in detail. <p>Mike

I think you are confusing the positive displacement superchargers with centrifugal superchargers. If you want some good reading on the subject, check out European Car's May issue. The Get Technical section has a writeup on positive displacement superchargers.

Umm, I think maybe my previous message confused you... I stated:<p>"I believe the Eaton unit used in the PES system is a 'roots'<br>type, the least efficient.."<p>in the last message I wrote...go back and re-read the whole thing, I was pretty much describing the differences between centrifugal and positive displacenment setups.<p>Brad

Not to sound argumentative here, but just look at the 1.8T. It is a turbo and it has plenty of low end torque. Unless you're going with an ungodly large turbo, the V6 should put out plenty of exhaust to spin a relatively small turbocharger very quickly...a smaller turbocharger, but still able to produce well over 300hp.<p>Brad

Your write up is a bit misleading. Your definition of efficiency appears to be that the most efficient unit heats the air charge the least. There are many other factors to be taken into account as well. <p>Exhaust Driven Supercharger (turbo)<br>Advantages: can spin up separately from engine speed, wasted exhaust energy can be used for more power. No parasitic drag on engine crank.<br>Disadvantages: complicated plumbing, hi underhood temps, higher backpressure, if you try to reduce backpressure with bigger turbo, you get more lag.<p>Centrifugal Supercharger<br>Advantages: simple installation, less underhood plumbing, no lag<br>Disadvantages: linear increase in boost, so it can only produce max boost at one rpm setting. Engine power increases as rpm climbs. Heat production. Parasitic drag on engine crank.<p>Positive Displacement (Roots)<br>Advantages: same as centifugal, plus boost pressure remains constant from idle to redline. This gives tons of low end torque as well as substantial HP increase.<br>Disadvantages: Heat production, parasitic drag.<p>I understand what you are saying about the air getting beaten up versus thrown, but the bottom line is that you are compressing a large amount of air into a small space and that is going to account for the vast majority of the rise in temp. I would think that the method of doing so would account for only a small fraction of the temp change, if anything. I have yet to see anything that quantifies whether there is a larger temp increase between Roots and centrifugal blowers. If you have something, I'd be interested in seeing it. One other factor to consider is that with a centrifugal blower, you are going to lose some of your boost just because the vanes are pushing backward as well. This can increase backpressure. With the Roots design this does not happen. Whew, I think that does it. <p>Chris<br>Waiting for a 12v Eaton supercharger

Sorry if my text was misleading. At least you got the point the second time! Efficiency when comparing two compressor types (even amongst two centrifugal types) deals with heat production. Other factors, such as complexity and under-hood heat, are factors but have nothing to do with the design of the forced induction unit. I'm also not clear on what you mean by 'backpressure' on the compressor side, where are you measuring 'boost'? I've always thought boost was measured on/near the outlet of the compressor housing, past the compressor wheel? I think perhaps we are just using different terms to describe things, and we are just confusing each other :) Either way, I don't have any hard numbers laying around right now to prove the differences in efficiency between roots designs and centrifugal compressors, but it is a fairly widely know fact that there is a significant difference between the two designs. If I find any numbers I will forward them on to you. <p>Brad

Yeah, we probably are confusing each other. I was referring to backpressure on the intake side of the compressor and boost on the outlet. I just think that the small difference in air temp on the boost side between centifugal and roots blowers is more than outweighed by the amount of boost provided at the low end by a roots. The reason that turbos snap your head back is that the power comes on late vs the roots. At that point the supercharged car would be out ahead if running comparable boost pressures. You really should check out the EC article, it is quite informative.<br>