Installation advice needed on a 1.8l 20VT VAG engine

[hotrod]

Tuning WI, is still pretty much an experimental process. The rules of thumb will get you in the ball park, but you need to try different things to find out the combination that "your engine" likes.

The Buick GN folks here in the U.S. have for many years used a very simple approach. They simply keep raising the water injection rate until the engine goes flat. The frequently discribe it as the engine sounds "soggy" and has sort of a flutting sound as the WI comes on. That is your clue that you've gone too far. Then you tune for best performance at that injection level, ie play with ignition timing, and air fuel mix. Then you go through the iteration again.

Eventually you will find that the gains get smaller and smaller with each incremental change.

The good news is, you really can't hurt much using this strategy. An internal combustion engine will swallow an impressive amount of water with no injury. During WWII they ran special tests on aircraft WI engines to see what the limits were. They would "drown" the engine -- feeding so much water that they had liquid water pouring out of the exhaust ports, and they were feeding enough water that an engine rated at 2000+ hp was down to 600 hp output. No damage to the engine!

Your only risk is if you tune so the engine absolutely "needs" the WI and you suddenly lose the injection, then you risk damage due to detonation. Only you can determine how far into that region of operation you want to go. On the other hand you can tune it so the WI provides a safety cushion but is not absolutely essential for operation. In that case if the WI fails the engine just runs uncomfortably hot but can survive the experience.

On the mixture -- for over 50 years serious users of WI have used 50/50 mix of methanol and water. That would incline me to start there.

I am currently experimenting with WI mixtures on my car. I started from 50/50 and use it as the reference point for evaluating them. Early tests indicate my car seems to like a little higher alcohol mix.

Larry