Jump to content
Posted

I should be hopping on the dyno this weekend (As long as my brother doesn't blow up his 05 first)

Couple of questions: Anyone have any thoughts on which level for a smarty only run? Any thoughts on which level for a smarty + TST run? 

 

And for the fun part! Guessing

Give your guess for: Smarty only and smarty + TST   My sig is up to date!

  • Replies 74
  • Views 9.6k
  • Created
  • Last Reply

Top Posters In This Topic

Posted Images

Featured Replies

  • Author

W&F What was your setup on your 02? I want to get around 600-620 here at elevation. Lots of work to do yet!

  • Author

4th will give you similar hp, but less torque than 5th. I saw a 50 ft/lb drop in tq doing my runs in direct instead of OD, as the turbo doesn't have time to light at the lower rpms in direct.

 

How you load the engine prior to the green light is how good your torque will come off. Personally I get to 1400-1500 rpms and start aplying brake and throttle to get the load/boost up and then let her rip. The total and mid range power is very different than just dropping the hammer.

 

Take a few seconds each run while you prep to ensure the motor it up to operating temp as well.

I'm scared that if the torque comes on too early (With the cold weather I see 10+ psi of boost at 1300rpm) It'll either blow the clutch off or snap the input on the trans.

Thanks for the advice too!

W&F What was your setup on your 02? I want to get around 600-620 here at elevation. Lots of work to do yet!

 

II silver 62 turbo, ATS intake and Exhaust manifolds, BD 155 7 hole injectors, BD TC and VB in otherwise stock auto tranny. Fass HPFP 150 transfer pump, II HRVP44 Edge Comp Hot unlock "Can't remember the version but it was the older one that did better HP / tq #'s than the newer versions, I tried several over the years, kept having the glitch of the comp not wanting to power on when cold or if it did it only lit up a random leds and did not do anythingwhich after about 6 version changes they finally got it" 5x3 & 5x4 ALWAYS did better than 5x5 on the comp by 5-15 hp consistantly. 3.54 gears with 265/75/16 tires most of the time.

For 600+ you will need to get into twins or a 64-66 size turbo or run injectables with a silver 62. 150 injectors should get you there but will be close to max on fuel only. At elevation I would not even consider a bigger single I would go twins hands down no questions asked, even if I were to ever go the route of performance again it would definitely be twins right off the get go.

I'm scared that if the torque comes on too early (With the cold weather I see 10+ psi of boost at 1300rpm) It'll either blow the clutch off or snap the input on the trans.

Thanks for the advice too!

On an inertia dyno you have no worries of that especially if running in 4th. You are already rolling at a fair speed when getting on it hard not like doing a dead stop launch on the street, do not worry about that in this arena especially if you are under 500++hp which you are..............No worries. :cool:  Do it in 4th and 5th if you get the chance just to see the difference it makes in the TQ #'s. :thumb1:

  • Author

I tow with this thing so a single isn't even an option for me. Plus I dropped a good chunk of change on my phatshaft. Plans are for an s475 underneath, water meth, studs, springs, pushrods, and a built 5 speed. We'll see where that gets me. I'll do a 4th and a 5th run if I get a chance!

The only reason I ran in 5th for my most recent dyno tuning was my tires. They are only 75 mph rated, so I didn't want to be taking them to 100+mph at full power.

 

 

 

As for the question on how dyno's measure, their output is horsepower and if you give it a tach signal you can get engine torque.

 

I know there is the whole hp doesn't matter, it's torque vs hp is better debate... but that's what it is. Horsepower is how fast work can be done, and the dyno computer knows how much work it takes to accelerate the drum, the faster the work is done the more hp is made. Without knowing how fast the vehicle engine is spinning only horsepower can be measured.

 

Just like with our rigs, torque is great but it's nothing without horsepower. If you think the hp doesn't matter then hook up to a load and try to climb a big grade at 1600 rpms in 5th and again at 2500 rpm in 5th. On any of the ~00ish and newer rigs the torque should be the same but there is a decent difference in hp. 2500 rpms will pull the hill much easier, and the power requirement is higher with the increased speed. Using the OEM  numbers from my 2005 there is 610 ft/lbs at 1600 which means the motor is making 185hp, and at 2500 there is at least 555 but less than 610 ft/lbs. At 2500 there is at least 264hp being made, and possibly up to 290. That extra 79-105hp is going to make a HUGE difference in towing, even thou the torque is the same.

 

I love torque, but at the end of the day it's useless without hp.

The only reason I ran in 5th for my most recent dyno tuning was my tires. They are only 75 mph rated, so I didn't want to be taking them to 100+mph at full power.

 

 

 

As for the question on how dyno's measure, their output is horsepower and if you give it a tach signal you can get engine torque.

 

I know there is the whole hp doesn't matter, it's torque vs hp is better debate... but that's what it is. Horsepower is how fast work can be done, and the dyno computer knows how much work it takes to accelerate the drum, the faster the work is done the more hp is made. Without knowing how fast the vehicle engine is spinning only horsepower can be measured.

 

Just like with our rigs, torque is great but it's nothing without horsepower. If you think the hp doesn't matter then hook up to a load and try to climb a big grade at 1600 rpms in 5th and again at 2500 rpm in 5th. On any of the ~00ish and newer rigs the torque should be the same but there is a decent difference in hp. 2500 rpms will pull the hill much easier, and the power requirement is higher with the increased speed. Using the OEM  numbers from my 2005 there is 610 ft/lbs at 1600 which means the motor is making 185hp, and at 2500 there is at least 555 but less than 610 ft/lbs. At 2500 there is at least 264hp being made, and possibly up to 290. That extra 79-105hp is going to make a HUGE difference in towing, even thou the torque is the same.

 

I love torque, but at the end of the day it's useless without hp.

 

I agree^^^^^, but where in the power band that both HP and Torque come on are important also....................especially when towing.

The only reason I ran in 5th for my most recent dyno tuning was my tires. They are only 75 mph rated, so I didn't want to be taking them to 100+mph at full power.

 

 

 

As for the question on how dyno's measure, their output is horsepower and if you give it a tach signal you can get engine torque.

 

I know there is the whole hp doesn't matter, it's torque vs hp is better debate... but that's what it is. Horsepower is how fast work can be done, and the dyno computer knows how much work it takes to accelerate the drum, the faster the work is done the more hp is made. Without knowing how fast the vehicle engine is spinning only horsepower can be measured.

 

Just like with our rigs, torque is great but it's nothing without horsepower. If you think the hp doesn't matter then hook up to a load and try to climb a big grade at 1600 rpms in 5th and again at 2500 rpm in 5th. On any of the ~00ish and newer rigs the torque should be the same but there is a decent difference in hp. 2500 rpms will pull the hill much easier, and the power requirement is higher with the increased speed. Using the OEM  numbers from my 2005 there is 610 ft/lbs at 1600 which means the motor is making 185hp, and at 2500 there is at least 555 but less than 610 ft/lbs. At 2500 there is at least 264hp being made, and possibly up to 290. That extra 79-105hp is going to make a HUGE difference in towing, even thou the torque is the same.

 

I love torque, but at the end of the day it's useless without hp.

   Close,  but  not quite.       At the end of the day,   torque is  useless without  SPEED

 

HP  is  nothing but   an equation of  torque versus  speed.      Torque is  measurable,    HP  is    calculated.   always is,  always will be.   HP  is  just  an  answer to  a  simple  algebraic  equation.

 

At the end of the  day,    without   SPEED      torque  is  useless.   You can't  ever, ever, ever  have  SPEED without enough  torque to spin up a   given load.    How  fast it  spins up,    and  maintains,  is torque.   All day long.

 

Look at  a  gas motor,  where  the   torque  falls  flat on it's face  a little more than   halfway up  the  rpm  scale...    and     HP    starts to decline too....     The  only reason   HP  doesn't fall off as  quick as  the torque,  is  the  SPEED  of  the engine.        The  amount  of  twist  is  less,   but  the  speed of  the twist  is  still getting  a lot of work done.  But  not  as  much per hour. 

 

This   may help.   It's  from   my    combustion  engineering   handbook:    HP=(RPM * T) / 5252        would be  torque,  not  time.   

    I've  had this argument  with  a lot of people  ever since   my  high school   physics  days.    Ya  can't rewrite  basic  physics. 

 

:whistle:   edit,  I  took your   numbers  from above, and plugged em in to  the  well known   equation.    ding.  spot on.   Those   cummins  boys  got it  spot on.    Imagine that. 

What  most  don't realize is,  ANY TRANSMISSION   loses   efficiency   in  any  direction  away  from   1:1  ratio.     1st gear  for example,  is  terrible  efficiency.   Does  a fantastic job at increasing torque..   

  When  in   straight through gear  (which mine is  not..  they  go through a counter shaft too)   that is  when  it's  close to 100%  efficiency. 

I'm not talking about    torque multiplication. (which is  what a transmission is,  a  torque multiplier)   I'm  talking about   the  power loss  through  a  very large gear,  and  a  smaller gear.  This too is  a  simple  physics  phenom.

A simple   6:1   gear  is  not  going to  increase torque the full 600%   Closer to  550% 

  One  that is  1:1   will be  much closer to being   100% efficiency.

Edited by rancherman

Well here is what I put down last weekend.

MichaelCampbell_zpsab1d1353.jpg

This was with the Smarty on 6 and the edge comp on 5x5. I basically make out the turbo and I'm now in the market for a replacement turbo... looking to hit somewhere between 550-600hp and about 1200ftlb of torque.

  • Author

Mulcher you should have tried it without the smarty... Would have been interesting to see!

 

550-600 you'll probably need a 64mm and that's laggy. Go twins!

Most Mustang Dynos are load cells but can be used as inertia as well, did you do the runs loaded or just as inertia with no load and simply running up the drum uncorrected? Is your comp hot unlocked or not, Probably could have hit 450 and 1000 with comp alone on 5X4 which has always done better on my runs as well as a lot of others I have seen over the years.

 

My 02 was 560 hp fuel only with silver 62 BD 155 sticks and hot comp and II HRVP44 which only gained me 40 hp over regular SO pump. With this setup and injectables 600 would be easy, silver 62 was a fun turbo.

My old   dynameter was  a simple   water brake.   hook her up to a garden hose.

input shaft  coupled to the engine,   going into a   torque converter  looking  apparatus.    instead of  a  output shaft that  spun,  it was a simple  load bar  hooked to a  'scale'.

To increase  drag,   I simply   screwed down on a  wheel,  which   adjusted the  position of the   fins  in the  'torque converter'..    and   the resulting  drag  was measured  at the  output  side of the  load.

There was 2  gauges.   first one  measured  rpm,  second one was   what was  being read  on the scale.     From that,  it's easy to calculate   HP.

 

 

When we   take a  NV5600's   gear ratio,

1st           5.63

  • 2nd          3.38
  • 3rd           2.04
  • 4th           1.39
  • 5th           1.00
  • 6th            0.73
  • Reverse   5:63

and   attach it to an  engine of  say 800 ft. lbs.   We would expect an  output shaft  torque of   4504  in 1st,  2708 in  2nd,  1632 in  3rd, 1112 in 4th,  800 in  5th,  and   584  in  OD.    (before  gear box  inefficiencies) 

Now,  multiply each of THOSE  by  the rear axle  ratio..   3.54 or  4.11   to get the   actual 'to the ground'    applied  torque...

Minus     the  inefficiencies  of   the  gear box and   right angle  direction change of  the rear axle.  

Theoretically,   It shouldn't  matter  what  gear we are in  when  calculating  HP.   'as long as   gear box  inefficiencies  are  not a  factor'

      Torque to the  ground will   be  much higher in lower gears,  as well as  much slower rpm.  Math is math.

  but  like I said  before,    large gear/small gear    differences   make up  a  huge  part of  the  driveline loss.   Straight through would be best,  but my NV's  aren't  built this way.   5th is  1;1  but  is  running through a countershaft.   It's not ideal,  but   the  gear size  is as close to  'efficient'   as   we  can expect.

We are applying almost  50% more torque to the ground in  5 gear @  2500 rpm,  as  compared to   1600 rpm in  6th.  This is  the only reason it feels  'more powerful'  at   high  engine speeds.   50%  change is  HUGE  on a  butt  dynameter!

and   attach it to an  engine of  say 800 ft. lbs.   We would expect an  output shaft  torque of   4504  in 1st,  2708 in  2nd,  1632 in  3rd, 1112 in 4th,  800 in  5th,  and   584  in  OD.    (before  gear box  inefficiencies) 

Now,  multiply each of THOSE  by  the rear axle  ratio..   3.54 or  4.11   to get the   actual 'to the ground'    applied  torque...

Minus     the  inefficiencies  of   the  gear box and   right angle  direction change of  the rear axle.  

Theoretically,   It shouldn't  matter  what  gear we are in  when  calculating  HP.   'as long as   gear box  inefficiencies  are  not a  factor'

      Torque to the  ground will   be  much higher in lower gears,  as well as  much slower rpm.  Math is math.

  but  like I said  before,    large gear/small gear    differences   make up  a  huge  part of  the  driveline loss.   Straight through would be best,  but my NV's  aren't  built this way.   5th is  1;1  but  is  running through a countershaft.   It's not ideal,  but   the  gear size  is as close to  'efficient'   as   we  can expect.

We are applying almost  50% more torque to the ground in  5 gear @  2500 rpm,  as  compared to   1600 rpm in  6th.  This is  the only reason it feels  'more powerful'  at   high  engine speeds.   50%  change is  HUGE  on a  butt  dynameter!

 

If your talking the 1600 vs 2500 I mentioned earlier then you misread what I typed. It was all in 5th gear, so the ratio's don't matter a lick. The only change is horsepower... which is a single word used to describe torque at speed. In my example the torque to the ground is identical, but the ability to get up the hill is not the same.

 

Some interesting numbers if you run torque to the ground at different gearing options (as you mentioned). Let use 3.42, 3.73, and 4.10. Lets also assume a flat torque curve of 800 ft/lbs. Speed in 60 mph in direct gear. Let's say that the twisting for required to keep the load moving is 1000 ft/bs. The 3.42 truck needs to make the most torque at the engine, 292 ft/lbs followed by the 3.73 at 268 ft/lbs, and finally the 4.10 needs the lowest at 244 ft/lbs. Okay there is your gearing, here is the hp kicker... all 3 engines are making the exact same hp, 118.8119. Why? Horsepower is real, it's the rate that the work is done at and they are all doing it at 60 mph. The work is twisting the tire with a force of 1000 ft/lbs, the speed is 624 rpms (tire size I used).. which is how we get 118hp.

 

I agree you can't argue with physics, but horesepower is real. Given any two of the three, hp/tq/rpms, you can calculate the 3rd. So torque is just as easily calculated. I've been playing with the calculations for a long time, they blow most people away.

 

Torque is useless without horsepower... I know you call it speed, but that's what horsepower is! Horsepower is the rate at which work is done, torque is the amount of work that is done.

 

Inertia dyno's measure horsepower, not torque. The twisting force required is set, so all the varies is the rated of acceleration. That's a horsepower measurement.

 

So a chassis dyno will measure horsepower, but a engine dyno will generally measure torque and use rpms to calculate horsepower. Both are in-fact measurable, it's just a matter of how.

 

Think about the old way horsepower was measured. A vertical lift of 550 lbs 1' in 1 second, that is measuring horsepower not torque. The only variable is speed, just like my 1600 rpm vs 2500 rpm example.. that's a horsepower difference and it will win the hill climb every time.

 

Water-brakes are great ways to measure. The torque measurement on the GE T-700 engine I fly with works on a similar principle of deflection. Torque is easier to measure this way, as there isn't (that I know of) a good way to measure horsepower while the engine is installed and functional.... you can measure hp, just not in this instance. FWIW the engines produce up to a combined 1427hp and 700 ft/lbs of torque to keep the helicopter flying, which can be up to 23K lbs but generally 17-18K. By the time the gearing reduction occurs there can be around 50K ft/lbs to the main rotor :-) My motor makes more than 900 ft/lbs (flywheel) but doesn't have the hp to make it fly, not even close. Turbines are also rated in SHP, not torque. I just happen to know the torque numbers from some GE training.

 

Additionally look at a NV5600 diagram again, it initially appears that 1:1 is on the counter-shaft but it's not. There is a direct link of the input to the ouput in 5th.

 

Here is a good image of a NV5600. There is a 5th gear c/s gear (a), but there in no reciprocal 5th gear. The 5th c/s gear is simply called the 5th gear, but not used for direct drive it's more the c/s input gear. 5th gear is direct and connects at (I) when it's used. The c/s is still spinning but its not transferring any power.

 

I am not sure how the shifting forks of a NV5600 work, but the direction must be reversed on the 5/6 fork. So 5th is fwd on the shifter and fwd on the fork, and 6th is back on the shifter and back on the fork.. otherwise 6th wouldn't engage with a back shifter.

 

NV5600flyer.jpg

Great write up AH64.  The HP torque discussion is a hot button topic for me.

Great write up AH64.  The HP torque discussion is a hot button topic for me.

It's more complex than many people realize, but a fun conversation. Which is what I like about this board, things are fun discussions and not arguments, or bashing.

Lets break out the over-sized boxing gloves for you's guys!!!

 

Great discussion!!

Solving for engine horsepower using the ET method.

horsepower_equation_et_method_horsepower

This method uses the elapsed time needed to complete a quarter mile run. It is used to give an estimate of vehicle(car, truck, motorcycle) engine or motor horsepower. Weight should include the mass of the vehicle, driver and passenger.

 

http://www.ajdesigner.com/phphorsepower/horsepower_equation_et_method_horsepower.php

 

And other options of calculation.

 

http://www.iprocessmart.com/techsmart/formulas.htm

 

http://www.wallaceracing.com/et-hp-mph.php

 

And if you really like details then this is for you.

 

http://www.stealth316.com/2-calc-hp-et-mph.htm

Most Mustang Dynos are load cells but can be used as inertia as well, did you do the runs loaded or just as inertia with no load and simply running up the drum uncorrected? Is your comp hot unlocked or not, Probably could have hit 450 and 1000 with comp alone on 5X4 which has always done better on my runs as well as a lot of others I have seen over the years.

 

My 02 was 560 hp fuel only with silver 62 BD 155 sticks and hot comp and II HRVP44 which only gained me 40 hp over regular SO pump. With this setup and injectables 600 would be easy, silver 62 was a fun turbo.

This Dyno was loaded and they did set the off set. I did do 2 other pulls with just the comp and the best group was what I posted with the smarty and comp :shrug: My comp isn't the hot unlocked version. The tech told me I probably wouldn't get much more HP out of the HE351 and 100hp sticks. He was saying that I was basically out of air flow.

I talked to Alex at Industrial Injection and I think I'm going to get a Phatshaft 62/80 for now then add an S480 to it later.

Yep.   HP IS  real.  It's  a  number on a piece of paper.   I can  see it on paper,  we both can  write it down on a piece of paper!!      (it's  a  simple  answer to  2 basic inputs)        we  can  'see'  horsepower  in   amount of work done,   (pile of  dirt  in  one  hour)   or   who  crosses  the finish line first  in a  timed event...    it's  the  'result'. 

When we  stomp  the accelerator,  it's  torque  we  feel.    we  don't  'feel'  horsepower.    

 

    Ya gotta  have  torque  FIRST.     Torque  makes  speed.   If the load  overcomes  the  torque,  it  cant spin up.   No  way around that.       Without   torque,    there is  no way   an  engine  can   spin up to  speed.      No speed,   No  horsepower.

Again,   Hp  is  just  a  figurative   number   or  quantity   of  the amount  of  work  done   in  a specific  time.         How  do you measure  work?      how heavy the  box is,  and how many boxes   are   moved  per hour.

Same  here.       How much  twist  ( torque)    *how heavy a  box  can be lifted*     and  how  fast  the  twist is *    how  fast the  box can be  moved  from point a to point b*

 

I  love   arguing   this,    cause  it's  been  misinterpreted  for   eons.      Perhaps  if  I wasn't  a  dumbass    'farmer'     It'd  be  easier   to  accept.      

But,   I won't  lose sleep over it.    Thousands  and  thousands  of  mechanical engineers  have paid  a  lot of money   to get  their degrees,  and  they all learn from the same    book  they   read the  first day:   'modern internal combustion engineering  101'.

There isn't a  'dynameter'   ever  built  or used today  that  has  a  'horsepower sensor'      They'll certainly  have    a  horsepower  output reading...     but  the ONLY WAY  THEY CAN  GET THAT  OUTPUT  is  using   SIMPLE   math   from   gathering  torque,  and  speed.      Yep,  your  correct  that  any algebraic  equation can be solved  with 2 inputs,  to derive a  3rd.        we  can  find   T,  we  can  find  HP,  we can  find  rpm.    with any of  the  2.    I learned that in  7 th grade.     

BUT,   when  someone give you a  HP  'number'  as  one of  the 2 inputs,    you gotta remember that  number    was not  from a   sensor.  it  was  already  derived  from  the    torque vs.  speed  equation,  FIRST.

 

Oh    almost  forgot to   add to my   post above,    those  total  'torque to the  ground'  figures!       After  calculating  the  final  axle  ratio  torque  output,    I should've mentioned   that    we need to     re figure  for the height of the tire.

....    Lets  say   our  800  ft lb  motor in    5th  is     going through a   3.54   axle.         Should  then  be   2832   raw  torque   coming out  the end of the axle...   to a distance of  1 foot  from  centerline.    I  forgot to   factor in the   height of  the average tire of  say  31 inches!   (or  15.5  inches  radius)        That will be  a  23%  reduction in  torque right off the bat  from  tire  height.   My bad!  

 

AH,    You're  correct on the   5th gear   part..   Perhaps if they   named  the  ' 5th gear countershaft'    (the  gear that  ties  the input gear to the  CS)  a    different name  (such as  mainshaft to  countershaft gear) ...  I  would've     caught it!    I see now  that   5th is indeed  straight though!

 

which brings me to the last part,   the difference we feel  @ 1600 vs.   2500  in the same gear.  (thanks for clarifying  which gear you were in)         If  cummins'  numbers  are   correct,     theoretically,     the  1600   should  hold  the  rpm   steady  far easier than  the  2500..     Are  you  misinterpreting  the  fact  it's more   difficult  to   ACCELERATE   going up a hill   with  1600  as  the starting point??      

look at it as  TOTAL  engine demand.      1st,  you  need to maintain  speed.  It takes  X amount  to maintain speed.     it's pretty   easy  to see a  truck  in  5th gear  @ 1600 rpm  will be going  a lot slower than  the same truck  already  turning  2500.      So  you have momentum  already  on your side...    and  the resulting   ability to  MAINTAIN   isn't as  taxing  to the  torque output of this  engine.

When you approach the same hill  @ 1600,    you have far less momentum,    and  now  we have  2  needs to be met.   The original  torque to MAINTAIN,  plus  now  we  need  additional torque to replace  the lost  momentum (accelerate)   because the momentum  was never there to help out.       

Maintaining  rpms,  and   accelerating,   are   2 very different   load demands  on an  engine  with finite amount of  torque.

 

I don't have the long grades  you western guys  have,  but I do  have  the loads!      Can you explain  to me  how  I  hit the bottom of the hill  at   2500, in  5th gear,   and  within  1/2 mile up the grade        my rpm is  now  17-1900  and  HOLDING??  why does it  hold there??      It's  called  getting back into the  torque sweet spot.  or  'torque rise'.     when the load  is  greater than  what  5th gear  can hold,   I shift down again..   

If  horsepower  was such  the   savior,  I wouldn't  have lost  the rpm  @  2500  in the first place.       Torque is  the  ONLY thing coming  out the end of the crankshaft.

  • Author

This Dyno was loaded and they did set the off set. I did do 2 other pulls with just the comp and the best group was what I posted with the smarty and comp :shrug: My comp isn't the hot unlocked version. The tech told me I probably wouldn't get much more HP out of the HE351 and 100hp sticks. He was saying that I was basically out of air flow.

I talked to Alex at Industrial Injection and I think I'm going to get a Phatshaft 62/80 for now then add an S480 to it later.

s480!? How much power are you trying to make? You do know a 75 will flow more air that a vp can supply right?

 

 

which brings me to the last part,   the difference we feel  @ 1600 vs.   2500  in the same gear.  (thanks for clarifying  which gear you were in)         If  cummins'  numbers  are   correct,     theoretically,     the  1600   should  hold  the  rpm   steady  far easier than  the  2500..     Are  you  misinterpreting  the  fact  it's more   difficult  to   ACCELERATE   going up a hill   with  1600  as  the starting point??      

look at it as  TOTAL  engine demand.      1st,  you  need to maintain  speed.  It takes  X amount  to maintain speed.     it's pretty   easy  to see a  truck  in  5th gear  @ 1600 rpm  will be going  a lot slower than  the same truck  already  turning  2500.      So  you have momentum  already  on your side...    and  the resulting   ability to  MAINTAIN   isn't as  taxing  to the  torque output of this  engine.

When you approach the same hill  @ 1600,    you have far less momentum,    and  now  we have  2  needs to be met.   The original  torque to MAINTAIN,  plus  now  we  need  additional torque to replace  the lost  momentum (accelerate)   because the momentum  was never there to help out.       

Maintaining  rpms,  and   accelerating,   are   2 very different   load demands  on an  engine  with finite amount of  torque.

 

I don't have the long grades  you western guys  have,  but I do  have  the loads!      Can you explain  to me  how  I  hit the bottom of the hill  at   2500, in  5th gear,   and  within  1/2 mile up the grade        my rpm is  now  17-1900  and  HOLDING??  why does it  hold there??      It's  called  getting back into the  torque sweet spot.  or  'torque rise'.     when the load  is  greater than  what  5th gear  can hold,   I shift down again..   

If  horsepower  was such  the   savior,  I wouldn't  have lost  the rpm  @  2500  in the first place.       Torque is  the  ONLY thing coming  out the end of the crankshaft.

I am talking about maintaining speed, not accelerating.

The reason you settle to 17-1900 rpms is as much about power production, as it is about power requirements. The speed associated with 2500 rpms takes too much power to maintain and you slow down. When you slow down to a 17-1900 rpm your power output is now equal to your power requirement.

Torque rise is real, and I am not pushing that off but your beyond that. It also means you have to lug the engine to get there, which is not reccpmmended.

My example still stands. A truck with a flat torque curve struggles to maintain speed at peak torque of 1600 rpms, but can pull the same grade in the same gear at 2500 rpms without being WOT. There is more parasitic engine drag, and a higher power requirement from the increased speed.. Yet it's easier to maintain speed.

The acceleration difference is from the horsower. Yes the inertia helps, but it still takes an increase in power to accelerate.

Good times.