IDM Mod question
#2
06-01-2009, 07:42 PM
You need the 75k ohm resistor (73.2k is for the 120v IDM). I had a couple, but they are spoken for. Someone may offer one up or you can get them here: Digi-Key - PPC75.0KXCT-ND (Vishay/BC Components - SFR16S0007502FR500) Minimum quantity to order is 5, but they are cheap.
#5
06-01-2009, 10:13 PM
#6
06-02-2009, 02:28 AM
#7
06-02-2009, 05:08 AM
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Before I continue with my long answer read the clip below...
...and note the part about ...when timing is advanced too far combustion pressure soars! A chip tune, the IDM mod, and an HPOP mod each independently advances the injection timing and using these mods with a standard chip tune which has an injection timing curve that doesn't take the mods into account might push the timing advance to the limit and cause excessive CP=Cylinder Pressure! As I'll discuss below the GTP38R mod increases BP which is an additional independent mechanism for increasing CP!
The CP~{(KEg)(Ng)}/{CV} where KEg=kinetic ENERGY of each gas molecule, Ng=Number of gas molecules, and CV=Cylinder Volume. The KEg comes from the fuel's chemical ENERGY that's released during combustion so the KEg depends on the mass and atomization of fuel per injection and the Ng depends on the BP. In words this equation says that the CP is proportional to the total ENERGY density in the cylinder.
1) For a given injection timing increasing the BP and or increasing the mass and atomization of fuel per injection increases the peak value of KEg for a given value of CV and this increases the maximum value of CP.
2) For a given BP and a given mass and atomization of fuel per injection advancing the injection timing causes the peak value of KEg to occur at a smaller value of CV and this increases the maximum value of CP.
The IDM mod and/or an HPOP mod alone or in combination advance the injection timing and increase the mass and atomization of fuel per injection and when these mods are used with a chip that's independently increasing the mass of fuel per injection and advancing the injection timing the potential exists for excessive CP.
I discussed the mechanism by which the IDM mod advances the injection timing in posts #77 & #78 here... https://www.ford-trucks.com/forums/7...it-work-6.html
...A turn on time of 440 us with the IDM mod versus 560 us for a stock IDM is 120 us faster, and thus fuel is injected 120 us sooner. At 3000 RPM this translates to a (120/55.55)=2.16 crankshaft degree advance in injection timing! If an aggressive tune is already pushing the timing advance to the limit, might another 2 degrees added to that eventually lead to disaster? Well, I guess only time will tell as I see that this mod is now going to be widely done by many, and combined with aggressive tunes to boot, in hopes of getting even more HP...