Quote:
Originally Posted by Chocoholic005
A DI system is just a way of more fine tuning a engine for fuel quantity. Its not a miricle worker by any means tho. The amounts of pressure this high compression motor will produce combined with a turbo will likely lead to the motor dieseling.
If a certain motor under a certain amount of boost with standard injection started knocking at 9.5:1 CR, Direct Injection might allow the CR to be raised to 10.2 or 10.5:1 without knock occuring, but its not going to help much when you start trying to add any real sort of boost to a 12.5:1 motor.
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Read up on DI -- it's much more than that, and it is really fantastic for tuning boosted engines!
The major problem with high CR pistons is that they tend to hold hot spots along the piston crown, and those hot spots make detonation more likely.
However, the incredibly atomized and precise targeting of fuel capable with DI means you can much more easily quench hot spots, and thus prevent knock.
Remember, running rich is all about cooling the piston with unburnt fuel. With DI you can do that far more precisely and effectively and use a leaner mixture.
Now it is certainly true that if you raise cylinder pressure high enough, something will break, even without detonation -- but that is not really going to much matter for a point or two of compression if the crank or piston rings simply can't handle, say, 30 psi.
I bet it will be possible to push 6-8 psi if not a bit more without undue risk -- and that should net you a nice bump in torque and power.
the big x factor was really tuning, and it sounds like the ECU will be reflashable, which is great!