[Subscribe to Daily Digest] |
Which means that it only delays or prevents the rise in the charge air created by heat soak in the intercooler. Which means that the intial air charge density will be unaffected under many situations. So the initial maximun torque would not be increased. But the water spray would help maintain that torque while at WOT (wide open throttle).
Before taking such measures, a NG900 or 9-3 that does not have the Viggen IC should go that route first. (It is interesting to see the water spay systems that are in use in Australia, but they do not worry about such things freezing up. If I was in such a warm climate, I would be catching the air conditioner condensate, and feeding that to the reservoir. It might need some filtering, but is it essentually distilled water in many respects.)
For water injection, you need to use a water alchohol mix to prevent freeze up. The water lowers temperatures and acts as an anti dentonant. The alchohol rases the fuel air ratio which also prevents knock. But the cooling only take place at by the creation of vapor, which reduces the air charge. These things are only needed with boost pressures that are quite high. Before doing this there are other things that you need to do to reduce air charge temperatures.
Air charge temperatures are reduced with low restriction intake and exhaust systems. Pressure drops associated with nasty flow transistions need to be corrected if possible. That does include IC upgrades when possible or economical. The Viggen IC is a very afforable upgrade path.
A free flowing exhaust, such as the Saab Sports exhaust, has compound benefits when operating at higher boost levels. Reduced back pressures mean that there is less exhaust gas reversion, which lowers combustion chamber temeratures and allows more air charge to get into the combustion chamber at any given boost pressure. As there is less back pressure, the engine will deliver more shaft HP. The wastegate will be more open for any given on boost situation, this is why the pistons will see less back pressure on the exhaust stroke. And this means lower exhaust temperatures.
Reducing pressure losses on the intake side also means that the turbo compressor works less hard, and works in a more efficient part of the compressor map. The power demand on the exhaust gas turbine is reduced, so the wastegate will be more open for any given on boost condition. So there is less exhaust back pressure, more shaft HP, lower temperatures, reduced exhaust gas reversion. So improvements on the intake side can have a magnified benefit, and an even greater effect on spoolup. But spoolup improvement potential can be lost in a stock configuration, where the designers decided that a sudden increase in power was not a good marketing or liability feature.
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
