Farmer Rock
just a fella' without a 10mm socket
IDIs make their peak torque at 1400 rpm,and peak hp at 3000 rpm.the cummins make peak torque at around 1600 rpm,and peak hp at 2500.
Rock
Rock
Modify 7.3 idi vs cummins swap
- Thread starter Daniel McCurdy
- Start date
cummins no doubt. even with the big turbo i got you can stab it at 1500 rpm and it will keep you right in the seat.
i think all v8 diesels make peak torque a little higher in the rpm range.
i didnt think the idi torque range was so low. ill have to find my dyno sheet and see when it made the whopping 257 tq lol.
Heres an IDI i ran on the dyno earlier this year, stock pump stock fuel system with just turbo and intercooler upgrades, very broad torque curve with pretty much within 50 tq of peak for 2000 rpms, peal was about 1500 rpms.
Another one, this is an auto truck with a very laggy 088 kit, had to start the run much higher to keep it from downshifting definitely well over 800ft lbs in a manual truck, especially starting the run below 2k rpms.
The inline six cummins may make more torque, but you wont get nearly as broad of a usable rpm range.
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Another one, this is an auto truck with a very laggy 088 kit, had to start the run much higher to keep it from downshifting definitely well over 800ft lbs in a manual truck, especially starting the run below 2k rpms.
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The inline six cummins may make more torque, but you wont get nearly as broad of a usable rpm range.
Daniel McCurdy
Full Access Member
It's interesting that despite the v8 having a 1.4 liter displacement advantage the straight 6 cummins still has better low end torque.
Farmer Rock
just a fella' without a 10mm socket
I always wondered why ford didn't put them in their trucks,or at least offer them as an option.But in a way it's good because that means more dt's for us,while other guys fool around with the less powerful 5.9 cummins
.I am actually trying to buy a dta360 5 speed bus to make a hauler truck out of.They are great engines,and eventually I would like to get a CCLB truck with a blown motor to swap one in.I could never bring myself to tearing out a good IDI from a truck.DTs are some of the best engines ever made if not the best for medium duty applications.Nothing could take the place of IDIs though.
Rock
Its a factor of the engine design, the cummins has very poor head flow compared to the idi, its meant for high velocity and quick cylinder filling, not overall flow or rpm. Also six in a row tends to be very torquey, and you know DI vs IDI too.
Daniel McCurdy
Full Access Member
The dt360 is the superior engine but getting a mechanical fan to fit is the trick. I don't know how strong the front gearcase is but if it's strong enough you could mount a pulley in between the crank and water pump pulley onto the gearcase that would allow the fan to sit low enough to clear the hood. Then you would just have to figure out the length issue witch I'm sure a custom radiator support moving everything forward would solve
ZWilson07
Cowboy
That curve actually looks great. I’d say about perfect for a modern daily driver/do it all type of truck.
What turbo setup was this? Any crazy modifications to fit the intercooler? Would you have any other suggestions to “improve” upon that while still keeping it a dd/do it all type of truck? I figure once you move away from stock pump and injectors, things start to change.
I personally thought my 45k mile stock brick nose with 5 speed and 4.10 gears was more than adequate. Would usually pull around 16-18 mpg depending on how i ran it on the highway. Granted im sure the manual and 4.10 gears helped.
I had an 06 cummins G56 truck as a direct comparison as well and while it certainly wasnt the same, it wasnt as bad as people claim idi’s are.
With a low rpm design and a turbo by default, airflow doesn't need to be superbly efficient. There's always the 24-valve head if more is needed...
Agreed, inlines are torquier than V's (when otherwise equal). V arrangements are normally a packaging compromise. More HP/cubes in a tight space. More challenging to work on. The large V12s at work actually have both the exhaust and intake nested in the 60-degree valley.
DI vs IDI isn't so cut & dry for torque. Very difficult to make apples-to-apples comparisons because engine designs vary so much. DI is where the horsepower is, now that we have electronic fuel systems on everything.
IDIBRONCO
IDIBRONCO
This may have been settled, but the last time I was into the more modern diesels, back in 06/07, there was a huge debate on whether the 12 valve head or the 24 valve head flowed better. 12 big valves vs. 24 little ones. It seemed to be split about 50/50. By driving them empty, the butt dyno said that the 24 valve was as gutless as the 12 valve was stock. I couldn't tell any difference in performance. I was very surprised at this since the 24 valve was so hyped up over the 12 valve.
IDIBRONCO
IDIBRONCO
Plus they don't seen to rev as high either. That can make a big difference depending on how you're driving.
79jasper
Chickenhawk
Not in stock form. Over 3500 or so you will float the valves.
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4400 rpms they will start floating, it takes a lot of manifold pressure for the them to start floating at a lower rpm, the stock engine in the shop truck with the compounds would start floating at 2800 with 50-60 psi boost working against the stock springs
