View Single Post
      05-14-2010, 09:07 AM   #20
Major General

Drives: 4 Wheels
Join Date: Aug 2007
Location: Planet Earth!

iTrader: (15)

Originally Posted by Clap135 View Post
It won't show inconsistencies. Think of it this way. On a port injection car, as you know, you can max duty cycles and just spray 100 percent of the time, stroke means nothing as the fuel goes through the intake manifold into the head to cause combustion right? On a DI car, you have a limited time that fuel will get ignited, once combustion in that cylinder completes the rest of the fuel you are spraying on the down stroke, gets blow out the valves which fools you o2 sensors. As far as how to measure a/f ratios, once you starting pushing limits, which you are, you simply can't be sure wtf is going on. Welcome to the wonderful world of direct injection. If you notice, any vw di car that makes huge power, resorts to a di/pi set up for this very reason. You can dump all the fuel you want if pressure doesnt drop, it doesnt mean that this fuel is used for combustion though. I've seen a 70mm ms3 dyno 320who at 27psi PISSING black smoke out the exhaust, af in the 9s. However the car made no power and was about 100-150whp off because it didn't have enough fuel despite the af readings showing stupid rich. I am at work right and this is sort of hard to explain, but ill go more in dept over the weekend if you need more info to grasp the lovely concept of DI.
The thing is my car is continuing to make more horsepower. I have tested this on a dyno and I am not running stupid fat. I am sure all of the higher hp applications will over over to port injection as well, but that is not a solution now. Regardless the point of this discussion still was that we can begin to test the limits of the fuel system. At some point we should see either major inconsistencies or the A/F going leaner and leaner as we reach the limits of the fuel system.

I am not sure when this window gets maxed out, but the next logical step is to alter the "window" of when injectors begin to fire. This can done with flashes only. But like I said, you still made your high 400whp, so you are not there yet, but Im betting its close.
We should be able to find that window regardless.