JasonCzerak
Active member
- Joined
- Aug 10, 2006
- Messages
- 14,823
So, I'm at a loss here. Before I start tossing hard parts at the problem, I'd like get some input.
Right at cruise I have this shudder. The truck is just actually on-off-on-off the throttle so quickly that the truck is almost bouncing up and down.
At 65-70-75mph. Mostly at 70mph, converter locked. 28-29% load. just over 17,500 PSI on the rail, 7-9psi boost. 1850-2000rpm range. 70 is just under 1900rpm.
I've gotten a known good MAP sensor and tossed it in with no change, put my original one back in same difference
Rail gauge bounces around a little, 500 or maybe 1000psi when this is occurring.
Drive pressure will fluctuate down and back up 3-4psi. Some time you can see boost bounce around too
I can manipulate the surge. I can make it worse or better specifically by changing the Rail map in the above mentioned load range. More pressure, say 3% more it's worse, 3-5% less it's almost not there, but somewhat there, you can hear it in the exhaust note.
Running stock software, all is good, I can't feel it. Running the tune JonF and I made last year I can't feel or hear anything.
So one might think it's the tune? ok.. Why? what would would cause an incompatibility? Timing in the cruise range is near stock, duration as well. pressure is completely different, yet when manipulated its changes the outcome. Torque management is is stock or near stock (doesn't matter) in the <50% load range
The stock and year old tune both run just over 17,500 psi and work just fine. The pressure were this current tune would shudder at is 17,500. Naturally the duration and timing maps are completely different. Since I can't data log the FCA I can't confirm but i'd imagine the duty cycle is different between the old and new tunes due to the completely different duration maps.
Where this current tune runs just about shudder free at is 15,000-15,500psi, about 2000psi shy of cleaner running.
So I'm thinking and being suggested to swap FCA's. So finding used one is going to be tricky. Done the MAP sensor swap. Dual CP3 controller is the next logical part to swap.
Any other ideas? Suggestions?
Right at cruise I have this shudder. The truck is just actually on-off-on-off the throttle so quickly that the truck is almost bouncing up and down.
At 65-70-75mph. Mostly at 70mph, converter locked. 28-29% load. just over 17,500 PSI on the rail, 7-9psi boost. 1850-2000rpm range. 70 is just under 1900rpm.
I've gotten a known good MAP sensor and tossed it in with no change, put my original one back in same difference
Rail gauge bounces around a little, 500 or maybe 1000psi when this is occurring.
Drive pressure will fluctuate down and back up 3-4psi. Some time you can see boost bounce around too
I can manipulate the surge. I can make it worse or better specifically by changing the Rail map in the above mentioned load range. More pressure, say 3% more it's worse, 3-5% less it's almost not there, but somewhat there, you can hear it in the exhaust note.
Running stock software, all is good, I can't feel it. Running the tune JonF and I made last year I can't feel or hear anything.
So one might think it's the tune? ok.. Why? what would would cause an incompatibility? Timing in the cruise range is near stock, duration as well. pressure is completely different, yet when manipulated its changes the outcome. Torque management is is stock or near stock (doesn't matter) in the <50% load range
The stock and year old tune both run just over 17,500 psi and work just fine. The pressure were this current tune would shudder at is 17,500. Naturally the duration and timing maps are completely different. Since I can't data log the FCA I can't confirm but i'd imagine the duty cycle is different between the old and new tunes due to the completely different duration maps.
Where this current tune runs just about shudder free at is 15,000-15,500psi, about 2000psi shy of cleaner running.
So I'm thinking and being suggested to swap FCA's. So finding used one is going to be tricky. Done the MAP sensor swap. Dual CP3 controller is the next logical part to swap.
Any other ideas? Suggestions?
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