[Dave at Pelican Parts]

I don't know anyone (yet) who has gone to an aftermarket system on a relatively-stock 2.0, so I can't answer you directly. Try me again in 2004, when my 74 2.0 is EXEMPT from smog testing...

However, there are a few things to remember about the D-jet FI system.

First, is uses manifold vaccuum as the primary measurement of how much fuel is needed. This is not hideously innaccurate, but it is not measuring exactly what is needed. To maintain a reasonable mixture, you need a certain mass of fuel that goes with a certain MASS of air. (About a 1:14 ratio.) Therefore, measuring the MASS of air coming into the system will tell you very accurately how much fuel you need.

Second, the D-jet system squirts fuel at two cylinders at a time. One of these cylinders has its intake valve opening at this time, while the other still has 1/2 of an engine revolution to go before its intake valve opens. This can't exactly be great for fuel atomization. Having a system that can squirt the fuel at each cylinder just before or just as its intake valve opens should result in a better burn. More power (probably *very* little!), less emissions.

Third, D-jet operates in an "open-loop" mode. The FI takes a guess at what the correct mixture might be, and delivers that much fuel. Modern FI sytems operate in "closed-loop" mode. The exhaust gases are sampled, and the FI uses that sample to determine if the mixture is too rich or too lean.

Fourth, most aftermarket systems let you tune and program arbitrarily. If you've got access to a dyno and a laptop, you can program the FI to give you the best power at all RPM and throttle settings. You can tune it until you drain your bank account, or until you decide the remaining power gains are too little to bother with, whichever comes first.

Finally, some of the higher-end aftermarket EFI systems also include ingition control. They are real DME systems. Most have inputs for knock sensors, some of them have inputs for one per cylinder and can control timing on a per-cylinder basis. This means that you can have more advance on spark timing, giving you more power. The DME will retard timing if it senses knocking, thus keeping the motor from blowing itself up. And again, this is all very programmable, thus allowing you to eat up copious amounts of dyno time getting the last couple of HP our of your motor.

The short answer: They can do quite a bit, but it'll cost a lot!

--DD