C&C Fuel Injection of Reno, Nevada did an evaluation of the 1998 Audi A8 fuel injector.

The following information was provided by Dave, the owner of C&C Fuel Injection.

The 1998 Audi A8 utilizes an air assist fuel injector. The air assist is in the form of a vacuum line connected to a port on the side of the injector. At idle, manifold vacuum disperses the incoming fuel from the injector nozzle, which results in a cleaner burn, reducing emissions.

C&C was asked to determine the output and spray pattern or the stock 1998 A8 fuel injector and compare it with a 1998 S8 fuel injector. I also aske that C&C Fuel INjection recommend a 24lb/hr fuel injector for higher performance applications.

The diagram C&C Fuel Injection provided shows the specifications for the stock 1998 A8 at the top. Next is a 24 lb/hr Bosch/Ford injector
The third injector is a 1998 Audi S8 injector.

http://pictureposter.audiworld.com/60746/audi_fuel_inj_diagram.jpg

The following pictures are from left to right: a stock 1997-99 A8 air assist fuel injector.
A stock 1997-99 european S8 fuel injector shown with and without the aluminum adaptor necessary to adapt it or other fuel injectors such as the 24lb/hr Ford injector th the US 1997-99 A8 intake manifold.

http://pictureposter.audiworld.com/60746/audi_fuel_inj_.1.jpg

C&C Fuel Injection, Reno, provided the aluminum adptors and o rings

How much could we actually gain if we were bale to increase airflow with an intake and exhaust kit? Would it be noticable? Also, the benefit of the Ford injectors would be that it would probably be significantly cheaper.

The 24lb/hr Ford injector is currently about $40.00 each, new. The S8 injector was approximately $120.00 each, two years ago when the euro was almost i:i to the dollar.

Either injector also needs an adaptor for the A8 intake manifold.

The higher output injector would be of a benefit at higher rpm's if the engine was modified to flow more air. This could be by way of camshaft changes, porting, turbochargung, supercharging, etc.

Obviously, a stock engine would not benefit. Too large an injector will cause idle and low speed running problems. Also emissions and fuel economy will be a problem

European Car recently ran an article on upgrading to 24 lb/hr injectors on a project BMW M-3. If my memory serves me correctly, there was a definate difference with the higher output injector at mid and higher rpms.

The Nov 2004 Car and Driver article on upgrading a BMW E36 M3 substituting the stock 17lb/hr injectors for 24 lb/hr injectors, a new chip, and a different (european version) mass airflow sensor, showed an increase of 14.1 rear wheel horsepower at 5400rpm. The car was also reported to be much snappier in acceleration.

One would probably have to say that the results would not have been as reported if the engine chip had not been modified to work with the european MAF and higher output injectors.