Reply to thread

Message: [QUOTE="TARM, post: 139576, member: 578"] Chevy, Yes but was that only SOI or was that entire PW? Also was that with the delay factored in or not? I think 28 is safe as well but figure the limit is somewhere close maybe 30 degree max. There are also a number of other issues I will bring up down a bit that I think make all of this and the equip needed if you really want to consistently tune these engines correctly an issue. BB, Yes that is correct you add it in. Did I make a mistake somewhere or mis type something to indicate otherwise? In the end what is improtant to take away is just how small and short the actual real injection event itself is as RPMS increase. The actual spray time that is. Its all well under 2 ms Since Chevy brought up the 28 degree which may even be closer to 30 as a limit if the readings are correct lets roll it out for both 3500 and 4000 rpms with 28 degrees. We will go with a fixed 28° of crank BTDC that is actual no delays accounted for. Not adding anything extra ATDC. Lets also split the injector delay dif and call it 0.65ms to put a single number to it. 3500 rpms works out to 21 degrees of crank for every 1ms so 21°/1ms 28°/21°=1.33ms So actual spray time is a mere 1.33ms@ 3500 RPMs BTDC Now add in the delay 1.33ms+0.65ms=1.98ms Now to convert that to degrees we have to convert the delay as this varies with rpm changes. 21°*0.65ms= 13.65° injector delay. Complete SOI 28°+13.65= 41.65 4000 rpms same deal. It works out to 24° (quick formula rpm to degree/ms (rpm/60000)*360=degrees/ms) Injecting for a total of 28° BTDC 28°/24°=1.16ms Delay 0.65ms 24°*0.65=15.6° delay. Complete SOI 28°+15.6°= 43.6° How do you accurately know any of this and whats going on in the actual engine though. IMO that is why as I see it to effectively and consistently get the best out of these engines to correctly tune them you need: Of course good tuning software, Oscilloscope, CP sensor or system, Load Dyno time along with a host of mechanical gauges to confirm readings if need be. The more I dig into this stuff the more I understand why you simply can not trust anything you see coming out of that ODBII port i.e. the PCM. At least not without knowing what is really going on at the mechanical level to get a proper correlation between the two. As an example: Look at all the issues we have had with the cam position sensor ( CPS) with various models doing this or causing codes on that. What if what the CPS is sending us, a far as data, is not exactly what is going on mechanically? If that's the case then..............????? Is the ICP sensor output really what we would find with a mechanical gauge. Basically what its comes down to is you can not trust anything that comes from the PCM/out the ODBII port at face value. Of course all of this kind stuff has been know by some for years; at least pre '08 based on where I have found it looking for confirmation of things. Its nothing new. [/QUOTE]