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post #1 of 15 (permalink) Old 07-22-2017, 07:07 PM Thread Starter
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Why Diesel?

I've been doing ALOT of work on 7.3s as of late and has me scratching my head as to why did Ford ever sell them. Hear me out--I drive a F150 with a 300 with 560k miles only engine work was head gasket at 250k. Till 94 the 300 made only 30 less lb-ft than the 7.3 and while yes the later 7.3 flywheel ratings were higher power to the ground would still be the same (thanks to those bigger tires). For me the transmission is not an issue I run a E4OD so its the same save the planetarys, and a few design revisions.

Can someone enlighten me on the great diesel engine, because all I see is marketing or V8 is better and Bigger is better. To me the 300 is better mpg (22 city and Highway), same power to ground (300 is slightly lower RPM), same transmission and all for a substantially price savings, and the lifetime maintenance is going to be basically the same (IPCs and IPRs are not cheap nor servicing the injectors).

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post #2 of 15 (permalink) Old 07-22-2017, 07:54 PM
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This is more of a apples to oranges question, It's all about application. When I'm pulling my car trailer It's much better to be maintaining highway speed over the raritan bridge then watching a 4.9 downshift 2 gears and tach out to hold 35mph. 525 ft pounds of torque at 1600 rpm is a big help. horsepower isn't everything. The Mack I drive for my night job has 488 Horsepower and 1700 ft pounds of torque with a rev limit of 2100rpm.

Because of the cost of maintenance it's surely not a practical daily driver, but if you need to move something heavy its the way to go.

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post #3 of 15 (permalink) Old 07-22-2017, 07:55 PM
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post #4 of 15 (permalink) Old 07-22-2017, 08:02 PM
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Quote:
Originally Posted by bowez View Post
Can someone enlighten me on the great diesel engine, because all I see is marketing or V8 is better and Bigger is better. To me the 300 is better mpg (22 city and Highway), same power to ground (300 is slightly lower RPM), same transmission and all for a substantially price savings, and the lifetime maintenance is going to be basically the same (IPCs and IPRs are not cheap nor servicing the injectors).
The diesel fuel has lubrication properities that keep the upper half of the cylinder lasting much longer than conventional gasoline engines = the reason why you see much higher mileages from diesel engines.
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post #5 of 15 (permalink) Old 07-22-2017, 09:13 PM
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Quote:
Originally Posted by bowez View Post
I've been doing ALOT of work on 7.3s as of late and has me scratching my head as to why did Ford ever sell them. Hear me out--I drive a F150 with a 300 with 560k miles only engine work was head gasket at 250k. Till 94 the 300 made only 30 less lb-ft than the 7.3 and while yes the later 7.3 flywheel ratings were higher power to the ground would still be the same (thanks to those bigger tires). For me the transmission is not an issue I run a E4OD so its the same save the planetarys, and a few design revisions.

Can someone enlighten me on the great diesel engine, because all I see is marketing or V8 is better and Bigger is better. To me the 300 is better mpg (22 city and Highway), same power to ground (300 is slightly lower RPM), same transmission and all for a substantially price savings, and the lifetime maintenance is going to be basically the same (IPCs and IPRs are not cheap nor servicing the injectors).
I would imagine it's all about the application.

If I were daily driving something, I'd probably want gas as it's generally less expensive to maintain, even though Diesel can get better MPG.

However, if I needed a dedicated vehicle to tow something, such as a race trailer, large trailer, etc, I'd want a diesel because of where it gets it's power, over how much power it has.

As was said above, horsepower isn't everything. The 300 I6 is a great motor, but for pulling power it doesn't compare to a diesel, because the diesel has tons more torque much earlier than a comparable gas engine.

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post #6 of 15 (permalink) Old 07-23-2017, 07:40 AM Thread Starter
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I'm not talking HP I'm comparing the Torque and the 7.3 does make more than the 300 but because of everything being bigger, what actually gets to the ground is effectively the same, as the 300's 300ft-lbs at idle. Remember every inch above stock is a 15% hit in torque and the 300s rolled off with 29" tires and the 7.3s were 31"+ (even the 2wd).

I totally understand the use of big diesel but I just see the small truck diesel as tits on a boar hog. Makes me think Ford killed the 300 to push more people to the more expensive diesel option because the 4.6 and 5.4 were not a good replacement for it. Now the 6.7 is a different story, but does the public really need 900ft-lbs. Like what I read a few months ago if your wanting to do 70mph with a 20,000lb load you need to be looking into a real truck.

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post #7 of 15 (permalink) Old 07-23-2017, 08:02 AM
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Just looking at numbers on paper won't tell you the whole story. Hook up 7000lbs to the back of a truck with the 300-6 and try to tow it through the mountains, then hook the same weight up to a 7.3 and make the same drive if you really want to know the answer. Yes the 300 will physically do it, but it will struggle and will not be able to maintain highway speed up hills, and when you get there, you will be stressed and tired; but with the 7.3 you will barely notice the load is there.

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post #8 of 15 (permalink) Old 07-23-2017, 08:26 AM
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Did I mention pulling my trailer, maintaining speed up hills with an average speed of 80mph getting 17mpg? I've had my hands on quite a few power strokes to the point that I can get the cab off of a super duty in 45 minutes. With that being said, my tow vehicle is a 03 GMC with a duramax that I kept simply because in 20 years I've worked on 3!

A daycab Mack pulling a 53ft trailer gets about 8mpg by the way.

I've owned a pickup with a 5.0, 5.4 and a company truck with a 4.9 and nothing tows like a diesel, but there is a few exceptions. The 6.9-7.3 NA diesel is an absolute dog and I'd rather tow with a rickshaw, same goes for the GM 6.2-6.5 NA.

It's a lot better to underwork a diesel then to overwork a gas engine.
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post #9 of 15 (permalink) Old 07-23-2017, 12:36 PM Thread Starter
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Clint so a 7.3IDI will also out tow a 300, to justify the extra cost?

Basically why did Ford sink money in a diesel--which wasn't theirs--when they had an engine performing just as well if not better and just modernize the 300. I believe the R&D costs spent on the 7.3IDI could have been better spent on the 300, but guess it goes back to the SC's reception--if it anit big and a V8 its no good--the Ecoboost is suffering form the same thought to an extent.

If all else fails get a bigger hammer!

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post #10 of 15 (permalink) Old 07-23-2017, 01:32 PM
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I'm not talking HP I'm comparing the Torque and the 7.3 does make more than the 300 but because of everything being bigger, what actually gets to the ground is effectively the same, as the 300's 300ft-lbs at idle. Remember every inch above stock is a 15% hit in torque and the 300s rolled off with 29" tires and the 7.3s were 31"+ (even the 2wd).

I totally understand the use of big diesel but I just see the small truck diesel as tits on a boar hog. Makes me think Ford killed the 300 to push more people to the more expensive diesel option because the 4.6 and 5.4 were not a good replacement for it. Now the 6.7 is a different story, but does the public really need 900ft-lbs. Like what I read a few months ago if your wanting to do 70mph with a 20,000lb load you need to be looking into a real truck.
Where are you getting these numbers from? while i agree that the 300 is a great engine they just don't make that much power. I believe the Carbureted trucks in the 80's made 223ft-lbs @ 1600 and the fuel injected trucks made around 260ft-lbs @ 2000. that is pretty much staying around 100 ft-lbs under the diesels all the way through the IDI period and that gap grows alot more after the power stroke started. I am in no way a 7.3 fan but they pull much stronger than any 300 ever has.
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post #11 of 15 (permalink) Old 07-23-2017, 03:27 PM
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Clint so a 7.3IDI will also out tow a 300, to justify the extra cost?

Basically why did Ford sink money in a diesel--which wasn't theirs--when they had an engine performing just as well if not better and just modernize the 300. I believe the R&D costs spent on the 7.3IDI could have been better spent on the 300, but guess it goes back to the SC's reception--if it anit big and a V8 its no good--the Ecoboost is suffering form the same thought to an extent.
When you say "performing just as well if not better" do you mean under a tow load? Because I'm going to disagree with you very much there.

As a daily driver, sure, but towing any significant weight? I just can't see it.

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post #12 of 15 (permalink) Old 07-23-2017, 03:54 PM
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It's completely apples and oranges as far as application goes. Bear in mind the 7.3 in no way replaced the 300 I6. A perfectly legitimate argument could be made about the 4.2 V6 and beyond that did directly replace it as being unworthy, but I don't really understand the debate as presented. Why buy a SC when you can get a 4.6 or 5.0 LX?

The market demanded a diesel option, and Ford obliged. Dodge outsourced their Cummins engines as well.

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post #13 of 15 (permalink) Old 07-23-2017, 05:32 PM Thread Starter
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IDI made 330 and looking at the history of the 300 all Ford ever did was change where they quoted it but yes it is just under 300 (which for a base engine why even be concerned with it when most people will buy the 302 ). Which is why I listed the larger tires and power to ground.

Matt, why buy an SC over a 5.0 or 4.6? Considering I have two 93s on 5.0 and one SC I know Ford said here you go we'll give you what you want but offers less performance in every way, unless you want MPG. While I don't knock the 4.6 I like torque which they anit got, I also have a 94 GM, and the only vehicles I have that will blow the tires off are the 300 with 560k on it and my SC (yes the truck is the slowest of the lot but gets the best city MPG).

So while yes I guess the reason is Ford gave the people what they asked for, even if it wasn't the best option out there. Just like now people think the Hemi is more powerful than the Ecoboost because its a big V8--never mind what the power curves show.

Having towed with this truck, well over GVWR, the powertrain is not the weak link. UPS also used them for years, and they were also in dump trucks (some of the more desirable manifolds).

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post #14 of 15 (permalink) Old 07-23-2017, 05:53 PM
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the 7.3 IDI was replaced by the power stroke mid year 1994 and the 4.9 wasn't discontinued until 96 so technically the 4.9 outlived the IDI

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post #15 of 15 (permalink) Old 07-25-2017, 04:31 AM
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One big thing is the capability for more power. I've owned my 7.3 PSD for 6 years now. It's over 300K now. Granted I've done a bunch of work and dumped money into it. I built everything from custom injectors to a twin charged induction setup and I tune it. It's about a fun 400/800trq combo. Power level can be adjusted on the fly with push of a button and I can run thru 15 different calibrations. If I ever build a engine the injectors are about 650hp capable on fuel and much much more with fog. In fact the size of injectors I built have made over 1K hp with spray yet can idle like a factory truck. Also when power goes up or your towing heavy fuel economy is still pretty good. I typically see 17-18 in town and 20 - 21 hwy mpg. Running empty. I am planning to pickup a 17 superduty here in the future.

Also bearing mind beyond displacement the IDI and powerstroke engines don't share much in common. The 7.3 powerstroke was typically rated to see 350K miles before overhaul but many push 500K no sweat with good maintenance. Quite a few 7.3 have been documented to surpass 1 million miles without tear down.
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