Is it possible to modify the glow plug calibration with the DIY tune? I'm currently running 5V steel plugs with the 5V OEM program, and I'm having trouble starting below 32°F.

I'm fortunate enough to have both 5V and 7V OEM GP programs from GDE, so I can switch back and forth with the programmer. GDE was working on an improved 5V GP calibration (with an instrumented plug) a couple years ago, but I don't believe it was ever released.

I've monitored the voltage to the plugs for both programs and they are quite different, but the voltages are not what you'd expect.

7V Program - 1.5 seconds @ ~5.5V, then 10 seconds @ ~3.5V
5V Program - 1.5 seconds @ ~10V, then 10 seconds @ ~2.0V

The 7V program repeats the brief high voltage (5.5V) on repeat key cycles. The 5V program does not repeat the brief high voltage (10V) on repeat key cycles, unless you wait for a minute or so. I've found the 5V program works best if you start cranking soon after the "Wait-to-Start" lamp goes off, the longer you wait the worse it does.

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2005 Liberty (KJ) CRD Limited - GDE FT ECO-Tune, Custom Trans Tune, Euro TC, 5V Steel GP, Weeks Stage 1&2, ARP Studs
1998 Cherokee (XJ) Classic - 30" Discoverer STT's on 2" Lift, SYE, 8.25 w/Aussie Locker
1984 CJ7 (CJ) - Stock
2011 VW Routan - Wish it had a CRD!
2011 Dodge Durango - HEMI, 4WD, Factory Tow Hook & Skid Plates

If you choose one of the Yeti tunes it will have the 7 volt calibration.

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U.S. Army Retired

We're running 2-year-old Bosch 5V metallic glow plugs with 7V programming on a Yeti Stage 2 tune. Depending on how cold the ambient temperature is, it can take two or three cycles of the ignition before starting in order to get everything up to cranking temperature on our KJ.

Having said that: our first winter weather of the season moved in overnight Sunday and is expected to last through Thursday or Friday. Temperatures are hovering in the 28°F range daytime, dipping down into the teens overnight. On Sunday, I filled up but forgot to add antigel to the tank; the Monday morning start was a real bugger as a result, and this is with an in-tank pump. Added antigel yesterday, topped off the tank again, and drove around for a few miles to make sure the treated fuel had made it to the injectors. Starting was much easier this morning. Just something to consider.

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2005 KJ CRD Limited 4x4:
245/75R16 BFG TA KO2s
OME / Clevis 2.5" Lift
JBA Lifted A-Arms
IRO WJ Short Rear UCA/WWDiesel mount
Skid Row Skidplates
HDS Model 001 Thermostat (190°F)
Suncoast TC
Full Weeks Kit
Bosch 5V glow plugs
Hayden 2986 fan clutch / GM 11-blade fan
Samco / Sasquatch Intake Hoses
Carter in-tank pump
Provent 200
V6 Airbox

I had yeti’s tune with glow plug recalibration 7 volt programming with 5 volt Bosch glow plugs. It worked great for about 18 months then it burned one of my glow plugs out. I replaced it and had yeti recalibrate my tune for 5 volt glow plugs. Everything is working great and yes yeti is the man if you want a awesome tune.