Remps wrote:Does case pressure stay more even throughout the run compared to having the fuel screw maxed?
OK, some notes beforehand:
- Time is seen from left to right. Each of the yellow vertical lines is at one half second intervals.
- WHITE: Truck speed in MPH.
- PINK: IP case-pressure.
- ORANGE: Engine RPM.
- PURPLE: Boost (at intake log).
OK. See my colored DOTS at the bottom of the image? Start at the left with the RED DOT . . .
RED Dot: 547.5 seconds.
- Just cruising at 52 MPH.
- At 1632 engine RPM.
- There's 126 PSIG case-pressure.
- There's 3 PSIG boost.
It's at this point that I start mashing the throttle to the floor.
BLUE Dot: 549 seconds.
- I'm up to 54 MPH.
- The engine is up to 2050 RPM.
- The case pressure has dropped to 113 PSIG.
- The boost is up to 10 PSIG.
It's at this point the throttle's on the floor.
GREEN Dot: 550 seconds.
- I'm up to 63 MPH.
- The engine's up to 2659 RPM.
- The case pressure is up to 122 PSIG.
- The boost is up to 36 PSIG.
At this point, the engine RPM have risen thus increasing the IP's shaft speed, thus case-pressure has risen to the point of regulation. The dynamic timing is following that pressure fall and rise.
YELLOW Dot: 551.55 seconds.
- I'm up to 66.8 MPH.
- The engine's up to 2728 RPM.
- The case-pressure is up to 136 PSIG.
- Boost is at 55.5 PSIG @ the head.
It's at this point I have just started backing off the throttle.
Notice how as I let off the throttle, the case pressure jumps (and apparently becomes a little unstable. I think that's the case-pressure regulator bouncing opener and closer). You'll also notice the truck's rate of acceleration kicks up notably (WHITE trace). It's my belief the case-pressure jumping up, is more fully advancing the timing (as compared to the recent droop) resulting in more power to the wheels as is made evident by the uptick in acceleration.
![Image](http://i169.photobucket.com/albums/u237/BuiesCreek847/VE%20Injection%20Pump/fuel-curve_zpsfyqhoull.jpg)
I need to have that full injection event timing advance for the duration of the WOT, in a perfect world.
- It may very well be a thing of adjusting the operating characteristics of the case-pressure regulator.
- May be as simple as dialing-in the IP timing-advance device spring.
- Turning down the fuel seems counter-productive in itself BUT, clearly, backing off a little appears to NET more power wound up.
This data-logging mess certainly invites a lot of consideration.
Shit.
There's a number of way to turn down the fuel if it HAD to be done. In my head, all the voices agree, this is not going to happen.
- Back off main fuel screw.
- Limit WOT via the high-idle screw.
- Raise the POP-pressure of the injectors (lots of fine-print).
Shit.
I think the best avenue to start with is to dial-in the timing advance device spring and its preload.
If I were a high-school boy, I'd be frustrated to the point of giving up as there's no App to do all this mess in a couple of minutes. Damn it!