DMAX boys fighting Gas Wara

[Hohn]

Originally posted by WadePatton

Graph: I'll try to get my curves into electronic format.



F1: some cars make more the 16000 R's -- gotta love that pnuematic valvetrain!



Hohn: While we're into TQ/HP lessons, what are the reasons for the variations in RWTQ we see for a given power level on the 5. 9? Is it in the dyno, the software, the operator, the driver, the mods, or my bet-the engine itself? And which number would tend to be more accurate?



thread hijack underway

Lots of variables, Wade. Too many to list. And we all know that these trucks vary quite a bit in stock tune. Nevermind the HUGE differences between 12v and 24V trucks.



I think the dyno you want depends on what you are looking for. For towing performance, use a load dyno that measures torque and calculates hp. For acceleration, use an intertial dyno, measure hp and caluclate tq. That's what the NASCAR boys do.



You can tell a LOT about an engine just by seeing where in the RPM range the peaks fall, and how high those peaks are. For example, if I have a hopped-up gasser that makes peak tq @ 5200 rpm, I know that it has NO bottom end torque to it. Moreover, that tq# will likely be very close to the HP number.



Me, I want my peak tq rpm to be low in the rpm range, and for the peak HP value to be high in the rpm range. If a bone stock ETH (rated at 245hp) had a flat torque curve all the way to 6500rpm, you would have a 625hp engine!! But it wouldn't necessarily tow any better.



Here's an example to show why HP numbers are misleading: Imagine you have a Pro Stock drag car, which revs to 10K rpm, and produces about 1500hp. Now imagine that the engine was fitted with a ONE TON flywheel! Yes, a gross exaggeration to prove a point. This super-heavy flywheel keeps the engine from revving quickly. Now, take this 1500hp car, and run the 1/4 mile. Guess what, it's SLOW! Now, we have one problem: the number won't add up. We took our dyno-proven 1500hp car to the track, and ended with a pass where our numbers add up to a lot less hp! A high 6-second pass took 15 seconds. By the timeslip, our HP is only 300ish. How did our 1500hp engine only give us a 300hp pass???



The flywheel, obviously. The point here is that HP is a measure of the RATE you can apply FORCE. It's not a measure of the force itself. If the engine revs REALLY slowly, you can't do work (move the car down the track) very fast-- thus you have less POWER. The difference is stored in the flywheel.



BUT, not so fast. We now have all this stored energy in the flywheel. If we were headed uphill, this will help us to maintain momentum up the hill.



Whenever you think POWER-- think time. Torque is FORCE (and distance). Force=Mass*acceleration. So TORQUE causes acceleration? hmm. Yes, it does.



Now this is where it gets confusing because acceleration is a rate, right? like feet/sec^2? Well, don't get ahead of yourself. The F=MA equation basically states that applying a force to something will cause it to accelerate. Doubling that force doubles the rate of acceleration.



Work is what confuses people because it is both linear and rotational. you push a car 10 feet, you've done work. You turn the wheels on that same car until it moves 10 feet, you've done the same work, just in a different way. Work and torque have the same units: distance and force.



Sorry to rehash all this crap that you've all heard before. I guess I'll sum up by saying that HP wind the "paper" argument, Torque wins in the real world.



Justin

 

[Elite1]

Originally posted by curatchko

I have a fueling box and some other mods now that make my 24v pretty healthy, but as you said, my 24 valver was totally gutless when I bought it. I couldn't go over 60-65 mph stock..... and going through overpasses on the freeway would lose me 10 mph... . did all the reflash stuff, took it to cummins, chrysler... . did the whole investigation and it's just a pig stock. Even now when I turn that box off it will not pull my trailer for beans.



The Vortec 454(300 horse, 405 torque) I had never quit pulling, and accelerated very quickly... I could take it through mountains without barely a strain with the trailer... .



Furthermore, a good friend bought an 03 about this time last year and it's a pig too... . couldn't do over 65 pulling his 6k travel trailer!!!! Has a box on it now and it's woken up but again, without the box it's a pig.



These are my only 2 diesel experiences. If it wasn't for TDR I'd gotten rid of this truck a long time ago.



No compaints now cuz I get great mileage and have lots of power. But I am taken back when I see people tell me how great diesels pull... . They don't from the factory!!!



Ain't no way any diesel, Ford GM or Chryser is going to out pull that 8. 1 Big Block chevy, off the show room floor. Just ain't gonna happen.

I noticed you said the suburban had 410 gears and your Ram has 355's that is a big difference. I believe that is what your feeling, it is hard to compare the two. I own a construction business and have several gas and diesel trucks... when you are pulling 10K or more up a steep grade I'll take my 2003' HO against any gasser on the road.

I have a buddy who has the 2001 3/4 ton Duramax, before that he had a 1999 3/4 ton Chevy with the 454. He says there is no comparison in pulling power up hills, the duramax pulls his trailer much easier and cooler than the gasser ever did.

 

[Trizae]

stock 97 12 valve

215 horse

460+/- lbs Torque



add spring kit and fuel plate (and tinker a little here and there)



500 X 3500/5252=333. 21



an 8100 V8 is 340HP and 450? torque



You do the math



not to mentention 5mpg to 15+mpg

 

[Cummins Cowboy]

Ok put a blown 1500hp drag race engine in a truck, then have a n14 cummins with 425hp and 1800plus pounds of torque, hook each truck to 80,000#'s go up a 7% grade, which one will crest the hill first, hint in ain't the gasser, that is if the gasser even makes it before it grenades.

 

[Dane]

I had a 99 Suburban 2500 with the 7. 4 liter, 4l80E trans, and 4. 10 gear before I bought this dodge, and I said the same thing.

You guys forgot one important thing - A 4. 10 geared truck will out pull a 3. 54 geared truck even if it has less HP and/or torque.

 

[hammersley]

Hohn - help????

Just for kicks and giggles - when we look at the comparisson of HP and Torque - isn't the torque output the most important when starting a load - such as a maximum load on a very steep hill? Also, isn't there some internal design characteristics associated with long stroke engines that inheriently allow them to "fight" loosing momentum (like on a long step hill or into a headwind) and also allow larger initial avilability of torque at lower RPM's.

 

[Hohn]

Originally posted by cummins cowboy

Ok put a blown 1500hp drag race engine in a truck, then have a n14 cummins with 425hp and 1800plus pounds of torque, hook each truck to 80,000#'s go up a 7% grade, which one will crest the hill first, hint in ain't the gasser, that is if the gasser even makes it before it grenades.

Not true. Assuming the 1500hp engine could hold together for at least a minute or two, it would get the load there WAY faster. WHY? Well, you can trade the HP for torque.



Remember: HP= torqueXrpm/5252.



So, if we start with 1500hp @10K rpm, then the engine is making 787. 8 lb-ft @ 10K rpm.



Now, gear it down with a 4:1 gear reduction, and you know have 3151. 2 lb-ft on a shaft turning at only 2500rpm! The huge HP number allows you to use gears to get more force, IF you are willing to have the work accomplished more slowly... .



HOHN

 

[Hohn]

Re: Hohn - help????

Originally posted by hammersley

Just for kicks and giggles - when we look at the comparisson of HP and Torque - isn't the torque output the most important when starting a load - such as a maximum load on a very steep hill? Also, isn't there some internal design characteristics associated with long stroke engines that inheriently allow them to "fight" loosing momentum (like on a long step hill or into a headwind) and also allow larger initial avilability of torque at lower RPM's.

You are correct on all accounts. Torque output is the ONLY thing that matters when starting a load. This is because it is FORCE. You are using FORCE to get the load moving.



If you think about it, HP is only significant in that it tells you how quickly you can apply force. Furthermore, high HP values allow you to trade some HP for Torque via gearing.



And yes, design features can favor torque or HP. Almost all diesels are designed for torque, and are thus undersquare (stroke bigger than bore).



Since torque is Force*Distance, it makes sense that a longer stroke will give you more torque... .



Justin

 

[RustyJC]

In fact, if you look at engine specs for large truck applications, one figure they give is "Torque at clutch engagement" - this is an indicator of how easily the engine can get the rig moving from a stop (also depending on gearing and other factors, of course).



Rusty