Fellow Audi Enthusiast:

I am interested in purchasing a pre-owned Audi A4 2.8 and wondered what year was the 5-valve per cylinder technology introduced on the A4 2.8? Also, what is the factory Audi warranty and are there any recalls, model years to avoid, or things to look for? Last, are there any disadvantages of buying from a non-Audi dealership other than "...a certified Audi"?

Thanks in advance for your assistance,
Andrew

if under warrenty, there is no difference between buy at Audi dealership or non-Audi dealership.<ul><li><a href="http://tech.vw.com">TSB</a></li></ul>

FrancisK gave vital info; however,think '98 had both 2V and 5V models. Open hood; if it sez "30V", that's the 5V model.
Don't know price difference bet. '98 and '99, but think all '99's had power passenger seat; '98 definitely doesn't.
If you're looking for a manual tranny, drive it. Main complaint on my '98 30V is long time for engine RPM to die between shifts; hurts fast upshifts. If you want a wimp stick, you're on your own.

... But I don't really mind it. Is this a function of the 30V setup or a computer-driven characteristic?

Computer driven, supposedly helps with lowering emissions.
Kev
98 2.8QMS

I hate changing clutchs (took me about 20 hours of work on my last Quattro), so I just dump the clutch right off idle. Maybe not the fastest take off, but I do tend to get a lot of miles out of my clutch. The nice thing about the heavy flywheel is the energy in it goes right into the driveline, I think I'd have to rev it a lot more, or slip it if I went to a lightened flywheel. I'd think differently if I raced, but I also wouldn't expect the same life out of the parts.

Actually the problem is common to most modern cars. The 30 valve does not have a heavy flywheel. Instead, this a computer/recirc valve emmissions device. When you close the throttle quickly, there are high emmissions due to unburned fuel exiting the combustion chamber. Slow the throttle action, and you have lower emmissions.

Long piston stroke engines ( like most German cars ) = lots of torque at low rpms. The problem is a lot of inertia. These designs are usually long lived as well.

High end sports cars ( Ferrari etc ) use expensive and complicated devices to deliver that wonderful carb-like sharpness. Most of these cars are short stroke designs.

Some aftermarket chips may address this.

April

so I agree, it's probably not flywheel as much as delayed throttle closure by the computer when the engine is under load.

Both the 2.8 and 1.8T DO have heavy flywheels and this explains why they build and lose revs slowly. A Miata, forinstance, builds revs much more quickly because it does have a light flywheel. It doesn't explain why the revs hang between shifts. This is the work of the computer which is trying to reduce emissions.

The 1.8T and 2.8 are also long-stroke engines which may cause the slow to build revs as well and do give them more torque. Inertia doesn't have much to do with the torque though. Leverage does. A long stroke engine has more leverage on the crank giving it more torque. If you put a light flywheel in, it's still going to have the same torque. The downside of this is higher piston speeds which means lower redlines.

As for "complicated devices to deliver that wonderful carb-like sharpness", I'm not sure what this means. Fuel injection actually gives much better throttle response in pretty much all cases. Ferraris and the like DO have light flywheels and short stroke engines which contributes greatly to their throttle response. Plus, they take the time to tune them correctly.

You're confusing a number of engine design parameters and their results. You are right that most new cars hang the revs between shifts and that the computer is doing this. Most performance chips for the 1.8T stop this behavior.

nt

The A4 does have a cold air valve between the intake maifold and air meter bypassing the throttle butterflies - which is a ECU controlled that can be opened or closed depending on temperature and load. But I don't think this is controlled by ECU for every revup/down. The ECU will open this valve a bit to add more air - and raise the rpm after a hard run so that the engine will not flood and converter will not build up, but as far as every rev is concerned, I don't think it comes into play.

Think crank weights. Think rods. Deep piston skirts. Often fewer larger displacement pistons. Long stokes usually have a heavier powertrain ( for many reasons we won't go into here;-). Every time the piston changes direction, it must overcome the stored energy ( via weight among other things ) that was pushing it in the original direction. Inertia ? It takes longer to swing a long pole of the same weight as a short one, given friction to overcome. Takes longer to change direction with the long pole. Leverage is greater with the long pole, yes. These are inherent qualities, right ? I think I know what makes torque. Please correct me if I'm wrong.

Given that we don't go into the nuts and bolts much here, it seems better to gloss over things than write a 5 page explanation. Let's not even go into the variances of compression ratios and valve overlap.

Everything is interdependent. I assume most people can make the connections.

My point is that long stroke engines that don't have sudden output changes ( due to heavy flywheels, etc ) live longer, and usually pollute less due to fewer power strokes in a given period. Good for most manufacturers. They don't change engine speeds very well, though:-(

Carbs ? They are much more limited as to their prime operating range. Most older Euro cars are fluffy ( sputter, low power, foul plugs ) at low revs. Tune them properly and run them in the intended range. Wow ! The best examples ? Mini Coopers, early Astons, Alfa 1750 motors, and just about any Ferrari. It takes specialized tuning ability, frequent tune-ups, and awareness as to gas quality and altitude.

Better ? Not for everyday, or most of us. Just really, really cool on a deserted road or the track, when it's done right.

On the very short stroke F355, Ferrari uses an extra two cats and chambers/exhausts for large throttle openings, high rpm, and sudden liftoff. Complicated and expensive. This eliminates the hang.

Everything is related when it comes to power delivery and the qualities felt in arriving there. I am sorry if I made less than obvious leaps.

April

This explains it better.

What I was thinking was that ultimate possible torque is defined by the force exerted on the piston and the leverage the piston has on the crank. I wasn't thinking about the parasitic losses due to reciprication of the pistons which is where inertia comes in. However, I still say that a heavy flywheel(or a heavy crank) doesn't effect the amount of torque produced since this isn't recipricating, it's just spinning. The heavy fly wheel just means you have to wait longer to get the torque. Heavy pistons and or rods could effect torque.

I think we're mostly saying the same thing. However, it's very nice to hit the gas on a short stroke, light flywheel engine and have it respond instantly.

I probably shouldn't have came down so hard on carbs since I have had multi-carb engines(bikes) that are great when tuned correctly. A Honda V4 is another good example of an engine that's great with well-tuned carbs.

The 1.8T has a motor on the butterfly for setting the throttle stop. Not sure if it's a stepper, looks kind of like a DC motor with a gear reduction.