Audi AAN Engine – Here's What You Should Know About It

In 1991, Audi made a real revolution when they presented their new AAN engine. This was the 2.2-liter gasoline engine that was made for the sports version of the Audi 100. The sedan was pretty popular all over the world, so thousands of these engines were made and sold. Some of them are still alive and allow their owners to feel all the power of the legend of the ninetieth.

Today, we'll tell you more about the AAN turbocharged engine made by Audi between 1991 and 1997 for their sports models. We'll open up some cool facts and secrets about the engine. Also, we'll show you the common problems and the weakest units of the engine so that you could understand if you need it.

Key features and my opinion about the engine

• Production years:1991-1997
• Average lifespan of AAN:180,000-210,000 miles
• Fuel supply type:Bosch Motronic injection
• Power range:230 hp
• Fuel efficiency:bad
• Engine block material:cast iron
• Engine reliability score:high
• The most common problems:issues with low-octane fuel, poor cooling system, hydraulic lifters aren't eternal, ignition is pretty tricky and unreliable.

Stock AAN engine - what should you know about it?

It was presented in 1991 and was used in the S4 and S6 versions of the Audi A100. The company also used this engine in the S2 model but they indexed that engine as ABY, although they were completely the same with some minor and negligible modifications.

The block was made of cast iron while the head was aluminum. The 5-cylinder engine was one of a kind at the moment it was presented in Europe. 5 cylinders and 20 valves form a really unique configuration. But actually, nothing revolutionary is there in the technologies of the engine.

Here's what you should understand about it:

• the stock version of the AAN produced 230 horsepower which is not that bad for a 2.2-liter engine;
• the engine is equipped with a turbocharger, but it's not that big and can easily be tuned to provide the driver with much more power;
• the timing system is driven by the chain but there is also a small belt, so the service is quite complicated and expensive;
• gas mileage is something Audi shouldn't be proud of, you couldn't get more than 16 MPG in the city which is really poor;
• this engine needs good gasoline unlike other engines from the 1990s, you should only use premium gas;
• the injection system is pretty complicated, if you happen to repair it, you should get ready to pay quite a lot of money;
• the KKK K24 turbocharger is now though completely outdated, but you should know it can be changed to something else easily.

This engine is known to be one of the popular project engines. Petrolheads take it for their projects, change turbos, use a different exhaust system, modify the intake, etc. This allows the engine to give much more power and torque.

But unfortunately, finding a really good AAN engine is hard. All of them have high mileage on them and require a lot of attention from the owner. If the engine is broken, you are likely to spend thousands of dollars in your tries to bring it back to life. Parts are expensive and hard to find.

How much power can you get from the AAN engine?

Audi made cool engines back in the 1990s. But not all of them were ideal. The 2.2-liter AAN engine is known to have a lot of positive reviews from those who like tuning engines. Yes, its cast-iron block can handle a lot of power. And we've seen a project with over 770 horsepower from the AAN engine with the stock block and head.

But to get this result, you will need to invest a lot in the engine. If you want to just pay some hundreds of dollars and get more power, then replacing a turbocharger and tuning the ECU are your choices. Be careful with any other improvements as they may cost you very much eventually.

Also, keep in mind that any power over 500 hp will be ruining for the engine. It will not go more than 50K miles after you improve it that way. If you want to tune the old engine with high mileage on it, you should be careful - it may just die immediately and not allow you to feel the real power.

What's the longevity of the AAN engine by Audi?

As a stock engine, this unit will go well over 200,000 miles before you need to invest some money in it. The first bad problems may occur at 230-250 thousand miles. Yes, most of those engines have already hit that milestone, so they are likely to be in their pre-dead condition. So, if you want to buy such an engine for your project car, you should be careful when choosing and checking it.

At 250,000 miles, it will most likely need new pistons, block repair, new rod bearings, new crankshaft and camshafts, new valves and seals, etc. This may be a very expensive repair. Given the engine is old and you are not likely to find many OEM parts on the market, you may be in trouble.

What are the common problems of the Audi AAN engine?

Most of the problems with the AAN engine occur just because it's old and has a lot of miles on it. Other than that, the engine is pretty good and can be used for different projects. We know some guys who modified their AAN engines in the stock Audi 100 S4 models made at the beginning of the 1990s. And they successfully won a lot of races in these cars.

But still, here are some of the most common problems of the AAN engine:

1. Overheating issues

This problem will be especially common for tuned engines with stock radiators. Once some unit in the cooling system fails, the engine immediately overheats. And this may lead to a lot of problems including stuck valves and a dead engine in the end. Sometimes, you will not even be able to repair the engine after severe overheating.

To avoid this, always pay attention to the radiators and thermostat. The cooling system here is pretty simple and doesn't cost a lot to repair. But you should keep an eye on it and repair it before it fails.

2. Ignition coils

The coils will be dead every other 10K miles and this is a problem. You just can't buy them easily in the car parts store because they are pretty rare. Finding a used coil will not solve the problem for a long time. The coils fail very often and your Audi may stand there in the garage for a week or two until you find the needed coil.

There is nothing much you can do to avoid this issue. Just have a couple of spare ignition coils to replace them when they fail again.

3. Timing system maintenance

Audi stated that every 60,000 miles you will need to replace the timing belt and the chain. Of course, it's important to change the coolant pump and the pulleys, too. This may seem like a simple maintenance task but it's hard to find the parts.

When you understand that in 5K miles your AAN needs maintenance, the best idea is to find the parts right there and then. You will not have to wait another week or two while someone will ship you the needed parts.

4. Turbocharger issues

The turbocharger is pretty old and non-technological. It can work up to 150,000 miles but it will fail then. The best idea is to install another turbocharger, but not a stock one. You should investigate what types of turbos are OK for this vehicle and just buy what you really need.

Replacement of the stock turbocharger is the key to every tuning project because the OEM turbo is pretty weak and slow.

5. Hydraulic lifters failure

This is not the major problem of the AAN engine, but you should keep it in mind, too. The lifters may fail at 150K miles and require replacement. We couldn't find any options for high-quality lifters in the US. You can order them from China (low-cost option) or from Europe and be ready to pay quite a lot for lifters and also for shipping.

Repairing the AAN engine - is it expensive?

Yes, repairing and maintaining your AAN engine made by Audi is very expensive. You will not be able to find parts in your local shops. Online research sometimes leaves you with no results. The best idea is to join a club of Audi fans (some forum, for example) and try to find a person who can search for parts in Germany. Also, Chinese parts are possible for the AAN engine but think about the quality.

But regarding labor costs, the engine is not that bad. It's pretty simple in terms of construction, so mechanics won't charge you thousands of dollars. But still, you should find a person who has experience exactly with the AAN engine.