The supercharged engine is what's supposed to be special about the G60, yet that's where the main problems lie. Although the G60 is supposed to go 140 mph, in stock form few will go that fast. In fact few will even keep up with a 16V Scirocco in a drag race. There are various steps to getting all of that advertised 158 bhp and more. Here's where to start:
Fuel Management: With the help of a Haltech fuel/air meter, I found quirks in VW's electronic fuel injection system that would make a true perfectionist throw his/her Corrado away. If there is anything consistent about this Digifant system, it's the fact that the system is inconsistent. I'd always hate the way the G60 would sometimes fly and sometimes disappoint. I'd always thought it was the over enthusiastic knock sensor, but all the time it was the mixture. The Digifant system cranks well and idles well, but just try to make it go fast and watch the mixture go crazy. Fuel enrichment (particularly critical for maximum horsepower in a supercharged engine) always has at least a 2 second delay between flooring the pedal and kicking in. Before it kicks in, the system is often trying to make power at a very lean (15:1) ratio. Sometimes it will only kick in above 4000 rpm, while at other times (particularly when flooring it at low rpm) it will unexpectedly go rich early and stay there. These are the times when the car flies.
Drag racing through the gears is frustrating. First usually doesn't last long enough to ever get enrichment (when it unexpectedly does, the car really takes off), then the shift to second starts the waiting for enrichment all over again. After the two seconds is up, you're coming to the top of second gear, so the enrichment comes too late to help very much. Finally, in third, there is time for the delayed enrichment to kick in, and the car really starts to pull.
I found the stock VW chip to be too lean; even in enrichment mode. Aftermarket chips boost the mixture up to the optimum 12.5:1 ratio, some even more. I tested the Neuspeed, and Autothority stage 1 chips. They were much faster (particularly the Autothority) than even the latest stock VW chip. I tested three different computers (including the latest from VW). They all had these peculiar characteristics; meaning as peculiar as they were, they were actually normal. Unfortunately changing chips does not fix the inconsistent fuel problem. Apparently VW "designed" it into the system.
The Haltech unit, or an oxygen sensor monitoring unit like it, is fantastic for keeping tabs on your fuel system. In fact, I wouldn't try to tune a car without an O2 monitoring unit. Don't try to use it with the existing oxygen sensor though. It must have it's own heated sensor (at least in a VW). It's response is nearly instantaneous, and the information it gives is fascinating. I was able to tweak the fuel injection system for much better power.
Here's what you do: Keep the injectors clean (as well as intake valves and tops of the pistons) with a dose of a good fuel system cleaner like LubroMoly, Techron, or Redline injector and intake valve cleaner. Use it religiously, each time you change your oil. Fuel Deposit build-up will cause pre-ignition pinging, which will cause the knock sensor to pull back timing and eat lots of horsepower.
Replace all O-ring seals on the fuel injectors every 50,000 miles. If you remove the injectors, be careful of the plastic spacers on either side of the O-rings. These get very brittle over the years, but replacements are not available from VW.
Be sure the fuel pressure regulator is working properly. Hook up a hand held vacuum pump to it and make sure it will hold both pressure and vacuum. If the diaphragm leaks at all, it will affect the fuel mixture. These are inexpensive and easy to replace. The same unit fits other Digifant VW's.
Make sure idle CO adjustment is at least on the rich side of spec. VW calls for a CO of 0.7, I found that going richer here made a tremendous improvement in the part throttle acceleration of the car. Careful now, don't be guilty of "tampering". There is a special procedure for checking the CO. The temp sensor must be disconnected after the engine is running. The Bentley manual gives the complete procedure.
Check electrical connections. Hopefully it was a rare thing, but I found a bad wire connecting the electronic injectors to the wiring harness. The red wire was very dark from heat in a section about an inch long. This wire had a resistance of 0.5 ohms. No wiring harness existed in the country at the time, so I cut out the bad section and soldered in a splice. The total load of the injectors is 4 ohm, so a 0.5 ohm wire could make a difference, particularly in cranking. I also sprayed the injector plugs and connectors with Cramolyn, a cleaner - antioxidant designed to make electrical connections work better, to remove oxidation and protect the connectors.
Change the computer chip! You'll find maybe 20 horses right here! The Autothority stage 1 is excellent.
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