Bill's chip could be DESIRED'ing more initial advance - dunno why, just yet, but MEASURED must always display DESIRED within 1*, so your MEASURED is no problem - START always gets increased advance, even when ECT is at operating temperature, but will drop off to +8.5* (tuned) as ECT increases
My truck is still running v2.0 with D\M +8.5 and TDCO (selected) -1.5 - Bill upgraded that to v2.1, but the engine seemed to lose some performance, so went back to v2.0 - I've not had experience with further upgrades, as that's about the chronology where I lost primary interest in the 6.5 (CRD is much more interesting\challenging)
Increased timing (advance) moves power development upward into the horsepower band, which is good for hi-performance but reduces low-end power, which is torque: Diesels are low-rpm torque-monsters - gassers (patooie!) are hi-rpm horsepower monsters (well, some of them are, anyway!) - gasoline is a quick-energy fuel, highly inflammable and violent but short-term duration, excellent for hi-rpm - Diesel fuel is a slow-energy fuel, difficult to ignite but increased duration - that means, not a high-rpm fuel in a mechanically-injected system, which the 6.5 got one of: all the fuel is injected in one burst, event-timing determined by IP position and injector pop-pressure - increased advance moves the injection event forward in time, necessary to allow complete burn at higher rpm - too much advance and the fuel is injected before cylinder temps have risen to combustion temperature, which cools the cylinder and delays combustion in a Diesel engine - gassers (you know!) with too much advance, being spark-infested, just ping and rattle and try to sound like a Diesel - too little advance and the injection event continues after cyl pressure has dropped below combustion temperature, the flame goes out with resultant black smoke = reduced torque\power - Diesel fuel combustion duration (slow-burn) and mechanical injection (one burst) are the limiting factors in hi-rpm horsepower development - thus, my concern on the increased low-rpm advance, which would require the IP advanced position to be on the ragged edge of viable injection event timing
Comparing your analog clock\watch to the crankshaft and pistons in your engine, 12 being TDC 0* crankshaft with piston at the top of it's stroke, 6 is BDC 180* crank when piston is at the bottom, 3 (at 90*) being the maximum length of the lever the piston is pushing in order to rotate the crank - maximum torque would be developed at low rpm when maximum cylinder pressure pushes that lever when it is at maximum length in the arc between 2 o'clock and 4 o'clock - that is rather impractical, however, because cylinder pressure (and combustion temperature) drops at a non-linear rate as the piston drops, so we must needs start the injection\combustion event such that max cylinder pressure occurs much earlier at ~15*, which is between 12 (0*) and 1 (30*) - if the injection event is further advanced, max cyl pressure is also advanced, pushing on the lever earlier in the arc when it is even shorter, and as pressure begins falling off much sooner, we get reduced torque
To overcome this we would need more air volume in the cylinder, such that cylinder pressure increases more rapidly, resulting in cylinder temperature increasing more rapidly with point of combustion temperature occuring earlier and cylinder pressure remaining hi much longer = more Boost at lower rpm, which will require more exhaust energy derived from increased BTU (air and fuel) or smaller turbine, either of which increases low-rpm spool-up - 'course the smaller turbine then restricts output power at higher rpm where exhaust energy is normally high - hmmmm..........the GM-X series turbochargers seem to come to mind on reading that, right?
CRD gets around this with very hi pressures (how does 4500psi at idle and 19000psi at 70mph and 22000psi at fwot grab ya?), multiple injection events and variable fuel-rates during each event, beginning combustion with minimal fuel to start the flame, increasing fuel-rate as flame increases, ending event by maintaining flame with reduced fuel volume, thus extending the event and maintaining cylinder pressure passed the mechanically-injected 15* point of diminished return - CRD rules!!!!!!!!
Aside: for you guys that carried a slide rule on your belt, another in your shirt pocket, and kept another under your pillow for intimate emergencies (and you know who you are, Goldsberg and rj!), feel free to chime in with minutes and seconds of an arc and deci-millimeters of fuel rates - no problem - I quickly noticed, during my first seminars, the glassy eyes and sudden loss of attention of some of the attendees when they were being brutally assailed with hard-core theory - best to generalize, addressing the deep stuff only when specifically asked, eh.................
My truck is still running v2.0 with D\M +8.5 and TDCO (selected) -1.5 - Bill upgraded that to v2.1, but the engine seemed to lose some performance, so went back to v2.0 - I've not had experience with further upgrades, as that's about the chronology where I lost primary interest in the 6.5 (CRD is much more interesting\challenging)
Increased timing (advance) moves power development upward into the horsepower band, which is good for hi-performance but reduces low-end power, which is torque: Diesels are low-rpm torque-monsters - gassers (patooie!) are hi-rpm horsepower monsters (well, some of them are, anyway!) - gasoline is a quick-energy fuel, highly inflammable and violent but short-term duration, excellent for hi-rpm - Diesel fuel is a slow-energy fuel, difficult to ignite but increased duration - that means, not a high-rpm fuel in a mechanically-injected system, which the 6.5 got one of: all the fuel is injected in one burst, event-timing determined by IP position and injector pop-pressure - increased advance moves the injection event forward in time, necessary to allow complete burn at higher rpm - too much advance and the fuel is injected before cylinder temps have risen to combustion temperature, which cools the cylinder and delays combustion in a Diesel engine - gassers (you know!) with too much advance, being spark-infested, just ping and rattle and try to sound like a Diesel - too little advance and the injection event continues after cyl pressure has dropped below combustion temperature, the flame goes out with resultant black smoke = reduced torque\power - Diesel fuel combustion duration (slow-burn) and mechanical injection (one burst) are the limiting factors in hi-rpm horsepower development - thus, my concern on the increased low-rpm advance, which would require the IP advanced position to be on the ragged edge of viable injection event timing
Comparing your analog clock\watch to the crankshaft and pistons in your engine, 12 being TDC 0* crankshaft with piston at the top of it's stroke, 6 is BDC 180* crank when piston is at the bottom, 3 (at 90*) being the maximum length of the lever the piston is pushing in order to rotate the crank - maximum torque would be developed at low rpm when maximum cylinder pressure pushes that lever when it is at maximum length in the arc between 2 o'clock and 4 o'clock - that is rather impractical, however, because cylinder pressure (and combustion temperature) drops at a non-linear rate as the piston drops, so we must needs start the injection\combustion event such that max cylinder pressure occurs much earlier at ~15*, which is between 12 (0*) and 1 (30*) - if the injection event is further advanced, max cyl pressure is also advanced, pushing on the lever earlier in the arc when it is even shorter, and as pressure begins falling off much sooner, we get reduced torque
To overcome this we would need more air volume in the cylinder, such that cylinder pressure increases more rapidly, resulting in cylinder temperature increasing more rapidly with point of combustion temperature occuring earlier and cylinder pressure remaining hi much longer = more Boost at lower rpm, which will require more exhaust energy derived from increased BTU (air and fuel) or smaller turbine, either of which increases low-rpm spool-up - 'course the smaller turbine then restricts output power at higher rpm where exhaust energy is normally high - hmmmm..........the GM-X series turbochargers seem to come to mind on reading that, right?
CRD gets around this with very hi pressures (how does 4500psi at idle and 19000psi at 70mph and 22000psi at fwot grab ya?), multiple injection events and variable fuel-rates during each event, beginning combustion with minimal fuel to start the flame, increasing fuel-rate as flame increases, ending event by maintaining flame with reduced fuel volume, thus extending the event and maintaining cylinder pressure passed the mechanically-injected 15* point of diminished return - CRD rules!!!!!!!!
Aside: for you guys that carried a slide rule on your belt, another in your shirt pocket, and kept another under your pillow for intimate emergencies (and you know who you are, Goldsberg and rj!), feel free to chime in with minutes and seconds of an arc and deci-millimeters of fuel rates - no problem - I quickly noticed, during my first seminars, the glassy eyes and sudden loss of attention of some of the attendees when they were being brutally assailed with hard-core theory - best to generalize, addressing the deep stuff only when specifically asked, eh.................
Last edited:
