Quote:
Originally Posted by Marrk
mark', the reason I asked was that I couldn't image placing an injector in the combustion chamber . . . but I guess it's possible.
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Diesels do it... The new common rail diesels inject fuel into the combustion chamber at full compression under loads of up to 50,000 psi. Gasoline engines do it at less than 3,000 psi because Gasoline motors don't use the introduction of fuel to initiate combustion like a diesel does. We still use spark plugs. That is because diesel is a more stable fuel...
Now as far as tuning goes I would like to add another topic for discussion... I'll start with my "hypothesis" as it were... the D-4S system is going to be epic for Ethanol and forced induction here is why...
In my engine, direct injection only, it is very difficult to control fuel delivery under boost at WOT through the mid range. Take a look at the attachments I have include, they deal with Ethanol fueling. Due to ethanol's properties it is difficult for the HPFP of my motor to keep up. The D-S4 engine should be able to take care of any fuel issues because it has secondary port injectors. If the ECU can be unlocked, and a turbo added... the possibilities are quite extraordinary.
On the log pick titled e85logpic2 you see the desired fuel pressure vs. actual in the second row of figures blue (FP Des psi)and orange (FP Rail psi) graph lines. Notice the RPM, 4400, just after at initial tip in on a 3rd gear pull 60-100mph. With the port injection You could run alot more fuel and use Ethanol more effectively. Oh by the way due to the efficiency of airflow, I have to mix my E85 with 91 octane at a ratio of 50/50. I would not be able to feed the motor with even close to enough fuel with straight E85. That is the downfall of direct injection, bigger injectors are big bux and hard to come by. With the port system on here, the extra fuel will just get thrown in, no problem.
On e85logpic1 you can see how, on the same pull, the fuel easily catches up in the upper ranges. This is due in large part to the cam driven HPFP that is used in my car. Other DI systems may or may not run into this problem, just something to think about I guess.