Can someone help me figure this out?

According to the Cat web site, they recommend to speck axle ratios and tire sizes like this:

Cat C13, Multi-torque

80,000 lb GVW
430-hp, 1550/1750 lb-ft
1325 rpm @ 65 mph

Cat C15, Multi-Torque

80,000 lb GVW
435-hp, 1550/1750 lb-ft
1325 rpm @ 65 mph

So, basically both of these engines are OK for full truck loads and will run at the same rpm with the same horse power and same torque...

But why should someone pay more for Cat C15 (I assume it costs more money!) when C13 can do the job cheaper, and it weighs almost 800 lbs less? Both engines are designed to run 1,000,000 mi to overhaul and have 30,000 mi maintenance intervals.

Any ideas?

And another question: 2 fully loaded trucks run with the same load on the same road at the same speed, let's say 65 mph. One has a C13, another C15. Both have the same HP, same Torque, and turn at 1325 rpm at 65 mph... same axle ratios ...

Will fuel mileage be any different?

Thanks to everyone for input on this confusing topic

 

They may say both are good for 1,000,000 miles before an overhaul, but I'm willing to bet the C-15 would outlast the C-13. That is a very low hp setting for the C-15 therefor it isn't working it's self to death, whereas that is about the max for a C-13. Plus, the truck will be worth more at resale time with a C-15 since it can be turned up to 550+ hp.

 

Well, the way you put it, it seems that C-13, would be the better choice! :roll:

If that would be 475-1850 C-15, specsed to run, at the same RPM/speed, there would be benefit of extra power, and torque, and engine is not working that high of % of total power, therefore should last longer... , or you'd simply got some extra, in case you need it...

As of to your second question, i'm pretty much sure, it will be about the same, may be 0.1-.2 gpm difference.

 

Hopefully I don't get flammed for this one but here goes....

Bigger Motors get BETTER fuel economy.

That C-13 will be working it's exhaust pipe off to make those numbers.

The C-15 set that low will barely be working.

Now I drive conservatively with a C-15 rated at 550hp with 4.11 rears and an 18speed and get 7mpg all day and night.

I don't know how much a C-13 costs now a days but the spec sheet in front of me for my new truck (should have it in a week or two) says the C-15 weighs 941 pounds and the line item cost is $12,874

 

Wow! How conservative you are, to get that mileage, at those rears?

Also, didn't want to look at my truck specs sheet, but i believe, you are about 10 grand short, on C-15 price. :wink:

 

Both engines are designed to run 1,000,000 mi to overhaul and have 30,000 mi maintenance intervals.

That's quite a claim

 

Ok! You've got me curious , and i did pull out my specs sheet.

C-15 475 ACERT 475@2100 1850@1200 $9,951 860LB.

That was in 2004, gain some weight and $$$ since than! :sad:

That $$$ number you see, is not represents the whole price of the engine, just an extra, for that particular option.
For example, if you look on your specs sheet, a lot of things(radiator...) is $0. :wink:

 

Well my spec sheet says $12,874, but it also says that the total price of the truck is $186,955, But I did not pay even close to that.

I would love to grab a couple of those $0 radiators :lol:

Lets not forget spec sheets come from dealers, and well, you should not trust dealers.

 

Another thing to consider is what the truck/engine application will be.
If your doing most of your hauling on flat land with lighter loads the smaller engine might be your best option.
Where if your hauling heavy loads in areas with Long grades or in the steep mountains, the extra power of the bigger engine would be the the better option, IMO.
This would also apply to starting and stopping power. The bigger engine will hold the truck back better on grades, and also get a heavy load rolling from a dead stop better, especially if your headed up hill.

 

That engine price is hard to believe. It can easily cost more than that for an in-frame. If that is all they cost, then it would be better to just throw the old engine away and buy a new one to drop in when you need a new engine. :shock: