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Old 20-11-2004, 04:57 PM
Gelf Gelf is offline
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Join Date: Feb 2004
Location: Astra Coupe Turbo in Wiltshire UK
Posts: 85
Default Pre Turbo Injection - How Much and When to Inject

Purpose of experiment:


Primary:

Determine the ideal amount of water to use and when to inject it.


Secondary:

Compare a single jet / HSV / FIA2 application to a twin jet / HSV / FIA2 application.

The single jet injects once every two revolutions (ingnition stroke on cylinder 3)

The twin jet injects once every revolution (ignition stroke on cylinder 2 and 3)



What are the desired effects of pre turbo WI?

Lower the inlet tract temperature.

Increase the efficiency of the turbo. Lower the turbo exit temps to as close to isothermal compression as possible.

And of course, in cylinder detonation control.


Negative effects of WI

Decreased efficiency of the intercooler, over injecting can saturate the internal surface of the IC, to the extent that it has virtually no effect at all.

What im looking for

Consistantly low turbo exit temps
High IC efficiency
Lower than ambient throttle temps in the summer, but not less than (??) for the winter ((??) not sure what the lowest temp should be yet).
Maximum effect from the east amount of water injected.

Water Injection turned off:




Single Jet set ups at fixed boost trigger @ 12/13 psi:












Twin Jet set ups at fixed boost trigger @ 12/13 psi:














Twin jet set up using 0.4 and 0.5 Triggered @ 4, 7, 10, 13, 14 and 15 psi: I would have used a pair of 0.4, but i dont have a pair yet.















Conclusion:

In my opinion, using a twin jet setup with the smallest jets possible and triggered at 4 psi gave the best results. I want to see 0 psi results.

I know most people say inject as late as possible, but these results would suggest otherwise. Im thinkin that when injecting late, the effects are felt after the event of high boost, too little (or too much) too late. Triggered early on using a system like 2d, the water is metered effectively from low to high rpms, as with the fuel, producing smoother transition in inlet tract temps.

I will continue too experiment now using twin 0.4's for winter and twin 0.5's or 0.6's in the summer.

I will measure differences in performance at different boost points using an accelerometer and post results.

Initiall experiments at 4 psi show no increase in lb - ft and a 2 or 3 drop in bhp, at WOT and 3/4 throttle opening.

Lower exhaust gas temps reduce the maximum turbo rpm's :?, but now the max boost setting can be increased :?
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