7.3 IDI vs. 5.7 Chevy Gasser. IDI a pooch?

[Andrew M. Frankli]

I have a 93 F-350 CC IDI non turbo E4od and a 89 Suburban 1500 5.7 gasser with a 700R4. I had the chance to tow the same 3500 lb. trailer with both vehicles 3 days apart. I am really impressed with the 1/2 ton Suburban. It pulls and accelerates and does everything as good as the IDI EXCEPT stop and get better fuel economy (13=gasser; 15=IDI.) The IDI is a real pooch - not much power. Just noise and smoke when I put my foot into it. The Chevy 350 actually felt significantly more powerful! I did not expect night and day difference, especially since it is a non-turbo IDI, but would have thought the diesel would be a lot more powerful towing than the suburban. Still, the diesel is a nicer tow vehicle - smoother and cheaper and I feel much safer in it with those big 1-ton brakes. Any opinions?? --Andy

 

[dieselviznince]

Maybe your 7.3 is wore out and has way more miles on it than the cheburban, or some to that effect.

 

[kcw12]

Get a 10,000 pound trailer, and tow with the subrabain and the the IDI. Then add 5000 more pounds and repeat process until one breaks.......

 

[Agnem]

What kind of shape is your IDI in? Are you comparing a worn out IDI to a gasser with a good tune up? Most IDI's out there are running retarded pumps and weak IP's because folks don't replace fuel system parts until they break, and they run a LONG time and get weaker with wear. If you don't give your diesel a "tune up" once a year, your short changing yourself. Injectors go bad fast, don't maintain good spray patterns, and IP's retard and drop fuel flow with wear. If you don't pull your injectors every year and get them tested, and have your timing checked and or set and monitor your fuel flow with an EGT gauge, then all your doing is assuming it's 100%, which is probably isn't. That, and gas is gas, where as diesel gets crappier each year they sell it to us.

 

[rthomas]

you need a turbo! also im sure the idi is a good bit heavier than the bowtie. in addition to the trucks in my sig i also have a 98 tahoe 5.7 vortec (255 hp 330tq) when not towing they are about the same power and mileage. however with the boat in tow (3800) the idi spanks the tahoe across the board

 

[oldmisterbill]

At 3500lbs U are just starting to get loaded.The Cheby is'nt even ready to work and the IdI is loafing,more weight will call for the deisels torque and sink the 350.Like Mel said put more weight then Judge .Or as Aric says "nevermind the mule Load the wagon"then we will seperate the diesel from the gasser. 3500 isn't much weight.

 

[riotwarrior]

Are you comparing apples to apples here? No I doubt it...what about gear ratios in the rear ends.....perhaps there is significant difference there too?

As Mel said make sure that diesel is "in Tune" then compare them.

 

[Andrew M. Frankli]

IDI vs Chevy 350

Sorry for not giving more info. Both vehicles have 230,000 miles on them are in excellent condition. I think it is apples and apples as far as a "fair" comparison can be. The Suburban has a 3:55 gear and the IDI is probably a 4:10 Both have new transmissions. I do not know about the injectors or timing of the IDI, however. It could be part of the problem, although the thing starts and runs beautifully. Thanks for the responses! I agree, if I loaded the Suburban more, I think the differences would become more and more apparent. --Andy

 

[Agnem]

I do not know about the injectors or timing of the IDI, however. It could be part of the problem, although the thing starts and runs beautifully.

Exactly my point. That's the reason so many are not putting out the power they are capable of.

 

[Rob94F250]

I own a 95 Suburban 4X2 1500 - 350 TBI (same engine as yours) 3.73 gears 4L60E trans. I bought a Jayco 27BH travel trailer and basically "sized" it for the Suburban - no slides to keep the weight down, etc. It is about 6000# loaded. It pulled it fairly well, but I never had it out to British Columbia in the mountain passes either.

Now I have a 94 F-250 IDI Turbo 4X2 with 4.10s. Granted it is a turbo, but it pulls it much better than the Suburban did. The feel of a 3/4 ton chassis is much better as well. The diesel is a completely different beast. The more weight you tow, the more it just seems to "bear down" and pull.

In general, the biggest thing that will bog you down at highway speeds is the darn wind drag of the trailer, and that seems to really start to take effect at about 50MPH.

As for mileage, the Suburban got 9MPG, while the Ford will get about 12MPG. These are with the larger Canadian gallon, so knock them down by 20% to compare to your numbers.

I usually run at about 55 - 60 MPH in either vehicle with the trailer, but throw a bit of an uphill run at the Suburban, and she is down into 2nd gear with the engine up around 3000 - 3200. They don't recommend OD for the Sub when towing. The Ford I run in OD.

With the elevation you are at (700 feet?), the Turbo would still help on your truck. Mine definitely appreciates the turbo at 4000++ feet of elevation.

As others have said, it is probably well worth looking at the timing on the Ford. Also, the bigger the trailer you tow, the more you should notice the difference between the gas and the diesel.

 

[argve]

used to have a 96 Z71 with a Vortec 5.7L - towed the same boat (4klbs) behind it as I did with The E (non turbo days) and I will say that I made the comment more than once that I wanted the Chevy back to handle the towing duties. In non turbo form she just didn't win any races - fuel econ she shined compared to the 350 gasser. Now fast forward to when we had our TT (9200lbs) I had a buddy move our TT to storage for the winter because the E was down - he had a 97 Tahoe with a 5.7L Vortec - I will say that the E not only handled the weight better but also towed nicer power wise - the vortec was struggling with it. I then seen the total bennies of having a diesel for pulling - after you turbo them it's a totally different ball game.

 

[Andrew M. Frankli]

Final comment...

Thanks for all the opinions; it has been helpful for me to enjoy my IDI. One real difference I didn't mention is that when the Suburban is pulling the Airstream, it is working hard. It is still happy, but it is definitely working. When I pull the trailer with the IDI, I could almost forget I am towing. Actually, the truck seems a little happier when it is pulling; it is smoother riding for sure and when cruising, feels like it could do this forever... The other subjective element is that the Gasser "feels" more responsive because there is power across the rpm range more than the diesel. e.g., when I am cruising at 55 with the gasser, I can put my foot into it, it will downshift and feel like it is pulling harder. The IDI just simply pulls the same almost regardless of throttle position (not really, but relatively so... ) Also, as much as I hate the 700R4 (compared to my old TH-400), the E4OD is even worse. I'm sure that is also part of the subjective comparison. I'm gonna check those injectors (heck - I might as well replace them) and make sure that pump is timed right. Now I'm motivated! Thanks again, folks. --Andy

 

[Diesel JD]

I'm sorry you have the E40DOA..... that can be fixed. A turbo does help make it more driveable and responsive, but it still won't make it a BBL gas V8 or a Cummins/PSD. Glad you enjoy your IDI.... your description matches my experience very much so.

 

[Mr_Roboto]

Same as some of the above replies. With that little weight, the gassers horsepower is still doing the work. Loaded to 20K #, the gasser would fall on its face.

I was loaded today at about 21 - 22K (12K truck plus E350 ambulance) that's where the diesel motor really delivers.