6V92 fast idle - another question

[Iceni John]

What's a good fast idle speed for a 6V92?   The reason I'm asking is because I have to replace the resistors that DDEC uses to bump up the revs for fast idle, but the broken 4300 ohm resistor is a size that's unavailable at my local electronics store  -  they stock plenty of 3900 and 4700 ohms, but nothing in between.   With the non-factory resistors my fast idle was about 1100 RPM.   Just to confuse matters, the smudgy copy of my bus's DDEC schematic shows resistors that give 1200 RPM fast idle which seems too fast, and a MC12's DDEC schematic shows resistors that give only 950 RPM which seems slow.   So, what's the best RPM for it?

Thanks, John

[Bill Gerrie]

My 6V92TA DDECIV fast idles at around 900 rpm. If you need a 4700 resistor you can put two that add up to that in series. Same thing.

[lostagain]

1000 to 1200 is good.

[luvrbus]

900 to 950 rpm is perfect for a DDEC the machinal engine are usually around 1000 rpms because they drop off when the AC is running with the liming speed governor   

[Iceni John]

900 to 950 rpm is perfect for a DDEC the machinal engine are usually around 1000 rpms because they drop off when the AC is running with the liming speed governor

Thank you so much for saying that!   If it was good enough for MCI and for you, then that's what I'll do.   I now just need to find the right resistors (thanks, Bill, for your help with them), then that's another good little job done.

Instead of crimping the resistors straight onto the 916 and 952 wires I instead made a little terminal block for them next to the front junction box.   It's now easy to get to, with no more vibration-prone iffy connections in impossible-to-reach areas.

John

[Bill Gerrie]

Your welcome John. Glad I could find the answer for you. Thanks Cliff for verifying the rpm's for the different engines.