What does IDI mean?
Senior User
Joined: Aug 2012
Posts: 218
Likes: 0
From: Ft. Worth
Guys...Our idi burn about 75% efficient...di's about 68% efficient...yes it is the compression ratios...Now if you set up a simple propane injection on a 6.9 idi you will get closer to 88 to 90 percent efficiency... Imagine one with turbo also...you got a truck that will rival a 7.3 di with turbo...
Posting Guru
Joined: Sep 2008
Posts: 1,840
Likes: 1
From: On the prairie
Where is this number coming from? And efficient in terms of what?
When you consider brake thermal effiency even modern diesels are lucky to hit 40% meaning of all the energy produced from combustion, only 40%(at best) is transmitted to the wheels. Cooling alone accounts for almost 30% and the other 30% is lost to exhaust (these are rough figures and vary by application). There's an awful long ways to go before we even come close to the 73% thermal efficency 'ole Rudolph envisioned.
Laughing Gas
Joined: Mar 2011
Posts: 1,229
Likes: 1
What does your per-mile cost work out to be on a hybrid diesel/propane system? Less than a strictly diesel system? If not, then I'd say "efficiency" is irrelevant.
Mountain Pass
Joined: Jun 2010
Posts: 186
Likes: 0
From: Dunbarton, NH
Ok ... but how many miles do you get per gallon of propane? Propane might make it run more efficiently, but propane's not cheap (over $2/gallon where I live).
What does your per-mile cost work out to be on a hybrid diesel/propane system? Less than a strictly diesel system? If not, then I'd say "efficiency" is irrelevant.
What does your per-mile cost work out to be on a hybrid diesel/propane system? Less than a strictly diesel system? If not, then I'd say "efficiency" is irrelevant.
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
Pretty much the same as diesel, just in gaseous form. Propane is more of a power adder to the diesel, not so much stand alone. Compressed Natural Gas is actually a potential full replacement for diesel.
New User
Joined: Jul 2015
Posts: 1
Likes: 0
it means it's a 10 minute job when an injector goes out haha
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More Turbo
Joined: Feb 2014
Posts: 656
Likes: 1
From: New Braunfels
So I must derail a wee bit and ask why the zf6 swap is rarely done, is it cause its too complicated or no need for a 6th gear?
More Turbo
Joined: Feb 2014
Posts: 656
Likes: 1
From: New Braunfels
I thought the ZF5 already had a granny gear or am I thinking of the uh t-19
Logistics Pro
Joined: Apr 2005
Posts: 4,221
Likes: 17
Neither, the T18 and NP435 are granny lows, ZF and T19 have a 'normal' range synchronized first gear.
More Turbo
Joined: Feb 2014
Posts: 656
Likes: 1
From: New Braunfels
What exactly is a double overdrive? Two over drive gears?
Postmaster
Joined: Dec 2011
Posts: 3,860
Likes: 7
Yup.
So, with the ZF-5, you have a .76 overdrive ratio. So for each .76 rotations of the input shaft, you get 1 rotation of the output shaft.
The problem is that the zf-6 has the same overdrive ratio, so there's no benefit to upgrading -- all it does is shift 2nd lower, shift 3rd lower and add a new 3rd. So instead of 2 gears down low you get three.
To get highway use out of it(which is usually the reason for a transmission swap), you need to change your rear end gearing to 'shift' all the gears higher in the range -- going from a 4.10 to a 3.55 for instance.
At that point, you might as well just slap a Gearvendors Overdrive unit behind your ZF-5 and call it a day: https://www.gearvendors.com/fdrive.html - You can then keep your 4:10 rear end gearing, which is great for towing and torque, and have a highway gear that lets you cruise 60MPH at 1600 RPM... Good for your fuel economy and makes 70MPH cruising smooth and fun instead of a screaming motor.
So, with the ZF-5, you have a .76 overdrive ratio. So for each .76 rotations of the input shaft, you get 1 rotation of the output shaft.
The problem is that the zf-6 has the same overdrive ratio, so there's no benefit to upgrading -- all it does is shift 2nd lower, shift 3rd lower and add a new 3rd. So instead of 2 gears down low you get three.
To get highway use out of it(which is usually the reason for a transmission swap), you need to change your rear end gearing to 'shift' all the gears higher in the range -- going from a 4.10 to a 3.55 for instance.
At that point, you might as well just slap a Gearvendors Overdrive unit behind your ZF-5 and call it a day: https://www.gearvendors.com/fdrive.html - You can then keep your 4:10 rear end gearing, which is great for towing and torque, and have a highway gear that lets you cruise 60MPH at 1600 RPM... Good for your fuel economy and makes 70MPH cruising smooth and fun instead of a screaming motor.
Laughing Gas
Joined: Dec 2013
Posts: 884
Likes: 7
Some folks might find it interesting that the new Kubota mini excavators have idi 4 cylinders. Our good heads help the idi motors get good mileage, they flow better than 6.0 4 valve heads. The ZF6 also has a different speed sensor output and mounting that make it a pain, couple that with the reasons others posted and you might as well find a wide ratio ZF5 that bolts up.