I am always comparing Ford products to Chevy. Anyway, was wondering about something. Went to MSNcarpoint.com and compared Tahoe to Expedition. Chevy HP was 275 with 290 ft/lbs of torque @ 5200 RPM. Expy was 232 HP with 291 ft/lbs @4750 RPM. Why does Chevy design their engine to produce all that power when the torque is the same? I understand that the average Joe (like me) focuses more on power, and Chevy can brag that the Tahoe has "more horsepower than any other vehicle in its class", but isn't torque the more important number? I am sure Chevy engineers are every bit as knowledgeable as Ford's. So why do they need to create an engine with all that power to get the same torque as the Expy? Is that inefficient? What gives? Thanks in advance.

 

The higher up the RPM scale the max horsepower is, the less use it is. In an ideal situation, max torque and horsepower would be reached at the same RPM, and it would be within the normal driveability band.

One reason I like the 5.4 over the 4.6 is that max torque comes at a relatively leisurely 2500 RPM as opposed to 35 RPM for the 4.6. This means that at typical highway speeds, the 5.4 is pretty close to its max torque range, whereas it will take a downshift in the 4.6 to get into the max torque band.

How often you planning on running your engine up to 5200 RPM?

 

That's only true part of the time. Horsepower is a function of torque, so torque determines horsepower, not the other way around. Torque is the force that moves your truck. Horsepower is the rate at which that force is used. If you had a perfectly flat torque "curve", your max horsepower would occur at redline. Why? Because Horsepower = (Torque x RPM)/5252. The horsepower and torque curves will always cross at 5252 rpm. As long as your torque is increasing or even staying the same as long as you add rpm, your horsepower is increasing. I think the only time your statement might be true is when you are starting to pull your load from a complete stop. Once in motion, give me the higher rpm horsepower any day of the week.
Says who? Again, if your torque curve were perfectly flat, every ascending rpm would pull harder than the one before it. THAT would be an ideal situation, and your peak numbers would occur at opposite ends of the chart. Your peak torque would be reached at idle but any point beyond that you would use the force at a higher rate and you would make more power. I'll elaborate later if I need to.

Back to Eddie's question. There is only 450 rpm difference between the torque peaks of the two engines. However the Chevy produces considerably more horsepower. It appears that this time, chevy made the more efficient motor.

 

You have the right idea. Torque is what pushes you back in the seat. The amount of torque and the length of the torque curve are the keys. HP comes with RPM plain and simple.

A BMW Formula 1 engine produces 850 HP at it's peak of 18,000 rpm. This is done while only producing 248 lb ft of torque at the HP peak.

In this case the Ford has the higher torque output, and maintained a larger percentage of it's torque over a slightly longer curve. It's only the fact that the Chevy curve is higher in the rev range that gives it a HP "advantage".

 

Is that right on the rpm that is max torque--usually an engine reaches max torque at 2000-3000(stock engine)...

Still by these numbers ford reaches its max torque earlier...

Max torque is usually were best fuel mileage is....

My max torque on my diesel is at 1700....

Just imagine 700 ft lbs at 1700rpm....

 

Coolhandluke is correct.

go out and test drive a BMW M3 and you will experience what he is talking about. Probably the flatest curve on the planet! The car pulls like h&ll all the way to redline!

as always just my .02

peace-

 

ALso my dear fellow FORD drivers... Lets remember that most of the time FORD underestimates the power of there vehicles- Simply put... When on a dyno they produce those horsepower figures on the rear wheels- Chevy does not. Their's is produced at the flywheel. Ofcourse if you own a 1999 Cobra it will have a recall for being way underpowered. Something like 205 on the rear wheels if I remember correctly. Kinda sucky for a motor that said 305hp! In anycase Ford has rectified the situation and Most of us are pleased...

 

EddieC,

Both engines have the same torque so they should be able to do the same amount of work. Roughly 290 lbs/ft worth of work. The HP rating is a guage of how fast you can do that work. In theory the Chev should get it done faster. Things get complicated by the loss of power (torque) through the drive train. The differential gear ratio will also determine how fast the work gets done. It is up to you to figure out (guess) how much each respective vehicle puts out to the rear wheels. That is where the power counts not up at the flywheel.

Regards

Jean Marc Chartier

 

IMO for a truck, Ford's approach to having more usable torque @ lower RPM is better than Chevy's higher RPM approach. It gives you more power at a lower RPM.

You are comparing the 4.8 to the 4.6, and in that case, both engines are relatively high RPM motors, and I personally would choose the 4.8 as being the better engine.

5.3 vs. 5.4, however is a different story...
We have a 2wd ext cab 5.3L chevy company truck that I drive time to time. Empty, both are about the same, with the chevy probably being a bit faster overall. With 3-4 people and some stuff in the bed, my truck is a whole lot better to drive. The Ford engine simply doesn't have to rev like the chevy's. It really makes a difference off the line and at highway speeds. Having lots of oomph @ 2-3k revs is a whole lot better than having to turn 4k+ to do the same thing. A guy here at work hates loading up and pulling his trailer w/ his 5.3 suburban, due to the fact that he has to always be reving the motor higher than he would like.

 

The way I've always understood it, big HP numbers are worthless at the low end but help sustain torque up high. In other words one needs more HP to keep the vehicle "pulling" into the higher RPM range. Hence, big HP numbers with peak performance in the high RPM ranges are not very practical unless you need power way up there.

 

While all of the talk physics is valid and so too is the discussion on where the max HP and Torque should be, lets not forget the obvious...

the 5.4 (not sure about 5.3 Chev) does NOT come with a manual tranny. So does the Ford auto tranny even allow the truck to reach 5000 rpm?

While not the same engine, my 4.2 auto has never gone beyond 4500 rpm (even with my beating the heck out of the truck)

 

My little 4.6 has been up to 5000 on a few occasions with the auto - so yes, the tranny will let you get there.

 

tlapan-

are you saying the ford 5.4 puts 260 hp and 345 tq to the rear wheels? I dont think so! several people on this site have stated that a 5.4 should put out about 195 hp at the rear wheels stock. this is comming from guys who have actually dynoed there trucks.
the problem many have seen with the chevys hp numbers is that while on the dyno running the proper way (in third gear) the speed limiter kicks in before the 5.3 gets to its peak, a problem solved simply by using some kind of aftermarket device to remove the speed limiter. there are pleant of chevy owners getting 220 to 230 hp at the rear wheels stock (even if it is at a very high rpm!)

 

These number don't add up

Horsepower = (Torque * RPM) / 5252

Chevy

HP = (290 * 5200) / 5252 = 287 HP

Ford

HP = (291 * 4750) / 5252 = 263 HP

 

The real test is "What do you need the torque and HP for?". For me, pulling a boat... I can pull a 3000+ pound load through hills and valleys spending most of the time in overdrive and not have it shift back and forth all the time.

I have the 5.4L, I have a friend who tows the same with a GMC and never tows without disabling overdrive. This is due to the low end torque advantage of the 5.4L.......... sure high end torque is great if you don't mind burning more gas (high rpm in a lower gear).