I'm sure if we could put my tiny 2.0L 4 in one of these and give it massive 6.xx:1 rear gears it could pull quite a load too. (just not fast).

If your comparing engines, then the mechanical advantage of the drivetrain should be the same. IMHO. doesn't matter to me that the gas engine can rev to 5000, and the diesel only to 3400.

You say thats not fair to the gasser, because it makes it's power at higher RPM's. i say it's not fair to the diesel because the extra gearing multiplies the torque for the gasser. (3.73 vs 4:30)

Wow, ok, just realized that I just got sucked into a big kiddie fight. I'm bigger than this. I know I understand this concept, and don't need this thread.

have not,,,, have too, have not, have too have not, have too

Wake up people.

I'm outta this thread. unsubscribe me......

 

These guys do a good job explaining what I'm trying to say.
Torque vs. Horsepower - Engine Power Delivery Explained - Hot Rod Magazine

Basically it take torque to move the truck. How fast it does this is your hp.

My point is that if you keep increasing the amount of work (i.e. heavier load), at some point the lack of torque will not allow all the hp to be used because the engine can only do so much work (work requiring torque).

This is why empty, a diesel and gas engine with similar hp will be close to the same speed. But when loaded, the diesels ability to do far more work will allow it to use all of it's hp while the gasser will be having to go to high RPM's to convert some of it's hp to torque and hence loosing hp.

Remember the fact that the gasser can hold lower gear and higher RPM at the same speed as a diesel means the gasser is converting more hp to torque. Think the engine is at higher RPM and yet the truck is not moving faster, so the gears are slowing the rotational speed of the engine down to create more torque to do the work, while the hp is suffering at the tires.

 

Unless I'm mistaken, you were posting "hp per liter" and "ft/lbs per liter" as a comparison. It still doesn't make a lot of sense to compare a forced-induction engine to a naturally aspirated engine in terms of displacement. But I do understand what you're trying to do.

 

Horsepower. Due to the higher torque the 6.7 makes much more HP than the 6.2 at low RPM, but the HP is what does it.

 

Torque moves the load, hp is how fast it moves the load.

 

If you mean the following two posts from Sand_Man, I do not see any personal attacks in there. However, you say something like "little johnny acts like a little kid when someone disagrees with him.", and say others are lying? If you do not understand the difference, you should duck out of this thread permanently. Seriously, take a few days off of this thread.

 

Hp only measures how fast it turns, not how powerful it turns.

Again, torque moves cars/trucks, hp moves them faster.

If both trucks/loads are going down the same road at the same speed, both are putting the same hp/tq to the tires. All that low end torque (hp) as you say, means it will climb the hill faster because it has more power. Yes the gasser will down shift a gear or 2 and produce more power and keep up. Remember hp that the engine makes means little, it's the hp and torque put to the tires, as you've pointed out many times. So if the engine produces this in low RPM range or high range means little to the tires doing the actual work. All the tires know is that they see X amount of torque which will allow them to do X amount of work. Again, hp will tell us how fast it can do the work. If there is an excessive amount of torque, it can do the work faster and have more hp.

Think of putting a braker bar on a ratchet. Without the bar you can produce X amount of torque to take off the bolt. Assume the bar double the ratchet length, you can now provide twice the torque and do the job twice as fast. The braker bar allowed you to apply more force (i.e. torque) and get the job down faster (increasing the hp). In this case torque is the limiting factor, similar to the loaded truck scenario.

Now assume the bolt was only finger tight. Will there be a difference when put the bar on the ratchet? Your amount of torque you apply will not change and neither will your hp, because you can not move your arm any faster. In fact placing your arm further out may actually slow down the rate you turn the bolt. In this case hp is the limiting factor, similar to the empty truck scenario.

When you were calculating the tractive force, did you by chance find the units of that? because force is in ft-lb...

 

HP is just torque combined with speed.

HP ... IS ... torque. Period.

I can design an engine that puts out 1000 ft/lbs of torque at 4500RPM, but only puts out 100ft/lbs of torque at 1500RPM where it's needed the most to get loads moving. You have to look at the torque curve overall to get a full understanding of what an engine is capable of. My '01 2-valve V10 puts out 80% of it's peak torque at only 1000RPM, and by 1500RPM is at 85%. According to Ford's torque curve in the brochure, anyway.

One of the reasons for the V10's success is the low-end torque, which for a gas motor was unheard of, at only 415 cubic inches. Found these images, interesting to look at. The V10 one sorta follows the Ford literature, even though it's obviously a non-PI head V10 from 1997-1999.



Taken from the gearvendors site: http://www.gearvendors.com/hrfordhptorque.html

Dodge: http://www.gearvendors.com/hrdodgehptorque.html

Chevy: http://www.gearvendors.com/hrgmhptorque.html

 

Great, someone trying to muddle the issue with facts again

 

Reread your statement, they are are contradicting. You can not say that hp = tq AND say hp = tq/time, you have one or the other, but not both.

I agree 100% with the first one, it is simply another way of stating what I have been saying: Torque moves a car/truck while hp tells you how fast it will do it.

But hp is not torque, it is torque with a time factor added to it.

Anyway, the previous discuss was about how fast a truck and trailer can make it up a hill. We'll specify that we are looking at a 3V V10 and a 6.4 form the same year, that way the hp is similar. If you have just the truck, both gas and diesel are going to be similar because both can apply similar hp to the tire and ground. This can be done by having different rear ends in them-but lets not go to that argument yet. You currently being limited by the amount of hp, basically both the diesel and gas engine are putting the same torque/hp down to the tire.

As you increase the load on the truck, their is more work to be done. As the amount of work increases, the amount of torque required to do the work increases. (In my previous example, the bolt is getting tighter) Which engine can produce more torque to coop with the extra work load? If both have the same tranny, I don't care if you have a 3.55 rear end in the diesel and a 4.30 in the gasser, if the diesel makes twice the torque it will have more torque to put down to the tires. It just can't apply it as fast as the gas engine can with the gearing.

In the 2007 comparison I posted a page ago, I noticed this exact phenomena. The gas and diesels of all 3 brands where similar empty. when they were loaded up, all three gassers suffered more than their diesel counterparts. while the diesels slowed down, the gas engines all slowed down more, even though they were all even when empty.

Using yours and Josh's logic, if the diesel and gas trucks are evenly fast empty, they should still be evenly fast towing, right? Yet this is not the case. The extra torque from the diesel allows the truck to apply more hp through the tire to the ground as the payloads increase.

Here is the page:
http://www.pickuptrucks.com/html/200...out7milan.html
and yes the diesels are 1 ton dually's and the gassers are 3/4 ton SRW, but my point still holds. If a two trucks are evenly fast empty, they should be evenly fast loaded regardless of configuration, according to this logic.

 

I sometimes type too fast and don't realize I left some things out.

What I meant is that in THIS discussion, HP is the same thing as torque. Why? Because an engine never stops rotating. What we are observing can be better explained as HP.

 

Why does the gas engine in the pickuptrucks.com example continue to gain speed (gain on the diesel) while the diesel does not?

 

Yes, but simply saying hp is all that matters does not explain the phenomena of how gas engines slow down more than diesels as the loads increase.

And yes, while the engine never stops rotating, the each power stroke of the engine can be looked at as an individual source of force, even if this is not perceivable by us... but that's just details.

I still stand by the fact that diesels have more torque, and that extra torque appears to help when you start loading down the truck.

 

The diesel's turbo spools up at a certain rate. If you restrict it's crankshaft acceleration (more load), that allows the turbo to spool up to a higher output and the result is more torque.

If you had a big enough naturally aspirated gas motor to have the same torque at the same RPMs (same torque curve) as the diesel, same gearing, same everything, the gasser would actually reach 60MPH first because it wouldn't have to wait for the turbo to spool up.

The "phenomena" you describe is not inherent to gas versus diesel. It's inherent to turbo vs. naturally-aspirated.

 

Yes, but how come we only see the lag when the trucks are loaded down? When they are empty, their is no apparent lag.

Errr.... wait a second.... lag should make the vehicle start slower then come to the same acceleration as the N/A. Yet the data shows the opposite, the diesels are moving faster all the way through the quarter mile. But if lag were a major issue, they should start out slower, then at least hold or gain on the NA.

I just don't see how lag helps the diesel accelerate faster when loaded...

Lets restate my concern. When the comparison test tested the diesel and the gas engines, they showed they had similar quarter mile times for the diesel and gas engines from Ford, the diesel and gas engines from GM, and the diesel and gas engines from Dodge. In other words both Dodges did the quarter mile in about the same time, both Ford did the quarter mile in the same time, and both GM's did the quarter mile in the same time.

When they towed a 10k lb trailer behind them, all the diesels preformed better than their counter part gas engines. So the diesel Dodge beat the gas Dodge, the Diesel Ford beat the gas Ford, and the diesel GM beat the gas GM.

Certainly lag will not make you preform better than a NA when towing, but not when empty.