this explains it better
there is a direct relationship between the two
http://www.dieselplace.com/forum/showthread.php?t=199702
there is a direct relationship between the two
http://www.dieselplace.com/forum/showthread.php?t=199702
TQ vs HP
- Thread starter TQMONSTR
- Start date
k, when drag racing, id be most concerned keeping at peak hp.
the TQ is really funnest and most practical for every day driving
maybe im wrong
Being that its your DD tune you could probably add all those parts with current tuning and be at 600ish orrr you would just retune it as it sits now and likely be in the same ballpark.
on a single charger its possible. on compound chargers, its much more difficult to do.
Just to make sure I understand what your asking,
you want to make more high RPM hp and less lower RPM hp?
...understanding that TQ is just explaining the relationship of hp and rpm
using .... TQ = (hp x 5252)/rpm you can figure out
600hp @ 3500rpm = 900 ft/lbs
and if you wanna stay at or under 1000ft/lbs
max hp @ 3500rpm 666hp
..........@ 3000rpm 571hp
..........@ 2500rpm 476hp
..........@ 2000rpm 380hp
..........@ 1500rpm 285hp
these numbers posted on a dyno sheet would give you a horizontal line for the TQ curve from 1500-3500rpm @ 1000ft/lbs
this also explains why cummins have a bigger difference than the duramax on hp vs tq numbers... cuz their hp comes on at a lower rpm
My understanding of torq changed a lot once I came to understand what it was, hopefully this helps :thumb:
(my apologies if my math is a little off)
The simplest answer to your question is, just spin the engine faster. There is more involved to it of course, but nothing will change without one of the factors (torque, RPM) changing first. HP is dirived from torque and RPM, so in its simplest form if one increases the other will as well. Now, understand, this is all well and good, but the engine needs to be able to support it, high flow intake, bigger turbo, ect ect ect.
Case in point: my truck vs a buddies truck.
My truck, stock fuel system crappy lift pump, efi live, S475 turbo with 1.01 housing and 83mm turbine wheel, max RPM 4500
Buddies truck, stock fuel system, better lift pump, efi live, and a 66mm turbo with a notably smaller turbine housing and wheel, max RPM stock.
My truck made 535 HP and about 800 ish TQ, his truck about 440 and over a thousand torque. Similer trucks with different intake options, mine flowing more up high and his down low, but mine made more HP, his more torque.
Bottom line, if all you want is more HP, just spin faster, but this isnt the best way. LOL!
If the truck makes it's maximum hp at 3300 rpm with a stock turbo how is spinning it to 3800 gonna help? It makes sense to do this with a bigger turbo cause they need to spin faster to move more air which is also why i think the tq is lower. They aren't moving as much air at 2200 rpm as a stock turbo so you get lower tq. This is all just my best guess though.
That is why i say there must be adequate engine modifications. The answer "just spin the engine faster" is in its simplest form. Its left up to you to decide how that is best accomplished.
I'll leave you with an equasion to help you ponder: HP=TQ*RPM/5252
One or the other or both must increase to produce more HP.
The way it makes sense in my head (right or wrong, I duno) is this...
Peak tq is made when the engine is making the most power out of each combustion event. Meaning that at say 2000rpms, where a given engine makes its peak tq, every power stroke is doing the peak amount of work per event. Or to put it a different way... the downward force from the piston on the connecting rod is the greatest at peak tq. Meaning the engine is doing the largest amount of work per revolution at peak tq.
Once the rpms pass peak tq, the overlap of higher rpms means that the same engine load gets distributed over more combustion events, meaning each individual combustion event isnt doing as much work, but as a whole the motor is doing more than it was at peak tq. Which translates to you going faster because you can add more load to the engine due to the higher rpms.
I think of a hypothetical truck & trailer with a manual tranny climbing a grade. You start in 6th gear, say 1800 rpms. Right at or near peak tq. The engine is doing the max amount of work per revolution at this rpm, but you lose speed climbing the grade so you downshift to 5th, say 2200 rpms. The same load distributed over more rpms means you don't lose speed even though you're not at peak tq anymore. Tq is sort of like efficiency to me and hp is basically a product mechanical advantage.
That's why I've always believed that you get the best fuel economy at peak tq because that's where the engine is the most efficient. IMO anyway. Feel free to correct me if I'm wrong.
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Peak tq is made when the engine is making the most power out of each combustion event. Meaning that at say 2000rpms, where a given engine makes its peak tq, every power stroke is doing the peak amount of work per event. Or to put it a different way... the downward force from the piston on the connecting rod is the greatest at peak tq. Meaning the engine is doing the largest amount of work per revolution at peak tq.
Once the rpms pass peak tq, the overlap of higher rpms means that the same engine load gets distributed over more combustion events, meaning each individual combustion event isnt doing as much work, but as a whole the motor is doing more than it was at peak tq. Which translates to you going faster because you can add more load to the engine due to the higher rpms.
I think of a hypothetical truck & trailer with a manual tranny climbing a grade. You start in 6th gear, say 1800 rpms. Right at or near peak tq. The engine is doing the max amount of work per revolution at this rpm, but you lose speed climbing the grade so you downshift to 5th, say 2200 rpms. The same load distributed over more rpms means you don't lose speed even though you're not at peak tq anymore. Tq is sort of like efficiency to me and hp is basically a product mechanical advantage.
That's why I've always believed that you get the best fuel economy at peak tq because that's where the engine is the most efficient. IMO anyway. Feel free to correct me if I'm wrong.
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It depends on how fast the hp falls off past peak. You want to have the truck run where the most power is. So you want the rpm range from one gear to next to have the highest possible average hp number. Or on a graph, you want it to have the largest area under the hp curve. If you get a higher avg hp by revving past peak hp then that's what you want to do.
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If a truck makes 600hp and 1200 ft lbs on a dyno can the same truck be tuned to make 600hp and 1000ft lbs? I have read that on lb7 and lly trucks the rods are good til around 1200 ft lbs. I know some will hold more and some less. I would like to up the hp but keep the tq around 1000. Is this even possible with a stock turbo? I would guess it could be done in the tuning but i don't know.
I always believed if you wanted to keep the torque down you didn't ramp in the fuel until higher up in the rpms. Say the turbo lights at 1700. Instead of running full fuel right there you only command say 75mm. Then as rpm's rise you ramp the mm up.
Pull fuel around peak tq but keep overall fueling the same, maybe bump it up at higher rpm.
Torque without RPM doesn't mean much. What's good is, a healthy amount of torque, and a healthy amount of RPM 
and then you have some real power :thumb:
HP (average HP) is what makes it all happen when your drag racing. Sure, good torque down lower in the rpm band will help it get moving through 1st, but once your beyond that, high peak torque numbers are just good for breaking things.
I tuned my truck for low torque... fueling doesn't start getting interesting until 3k (it's bumped up before that, just nothing crazy). But from 3 to 3800 it makes pretty good power.
If I was pulling heavy loads all day I would be more concerned with torque numbers than I am now...
just my $0.02
and then you have some real power :thumb:HP (average HP) is what makes it all happen when your drag racing. Sure, good torque down lower in the rpm band will help it get moving through 1st, but once your beyond that, high peak torque numbers are just good for breaking things.
I tuned my truck for low torque... fueling doesn't start getting interesting until 3k (it's bumped up before that, just nothing crazy). But from 3 to 3800 it makes pretty good power.
If I was pulling heavy loads all day I would be more concerned with torque numbers than I am now...
just my $0.02
Torque still exist even at peak horsepower, and horsepower is still there at peak torque. If you were to derive the relationship between acceleration and torque mathmatecially I'm sure you would find it as a direct function of horsepower. The fact that you have a dynamic system that exerts a different force through time(rpms) makes the fact of trying to compare torque and HP numbers irrelevant because they are going to change in direct proportion to rpms.
To look at the situation you would have to look at the area under the curve as other people have said. From analyzing units you could look at the area under the curve of a torque vs rpm graph and see the integration of this graph would give you units of power. So if you modified your shifting to make the rpm range maximize this integral within the limits defined by your shift points you would end up with the most power, which has a time component in it unlike torque which directly relates to acceleration witch has a time component also, this time component directly relates to power. Power is say torque*rpms which converts to force*distance/seconds the fact that as power increases with more revolutions for same given amount of seconds due to seconds being in the denomitor of the fraction makes sense that more horsepower yields a shorter time to complete the quarter mile.
There is probably a way to explain this a lot simpiler but the fact is that you can't express the power, torque, or fastness of an engine by looking at a peak number because that only exist at one rpm or one instance in time, so this number is always changing. Therefore you have to look to maximize an area under a time curve. To make it even more simple your torque at peak horsepower (say 400) at 3200rpm, is more effective to what we desire (accelaration racing fastest quarter mile) even though it is not the maximum torque (say 600) at peak horsepower occuring at 1600rpms.
Analogous to this is the fact that with more horsepower I could tow more (move a bigger load through a bigger distance in a shorter amount of time with more horsepower), than with more torque. I put the emphasis on shorter because with more horsepower I will have towed more or the same amount but in a shorter amount of time because horsepower contains a time component in its definition and torque ignors this time component.
To look at the situation you would have to look at the area under the curve as other people have said. From analyzing units you could look at the area under the curve of a torque vs rpm graph and see the integration of this graph would give you units of power. So if you modified your shifting to make the rpm range maximize this integral within the limits defined by your shift points you would end up with the most power, which has a time component in it unlike torque which directly relates to acceleration witch has a time component also, this time component directly relates to power. Power is say torque*rpms which converts to force*distance/seconds the fact that as power increases with more revolutions for same given amount of seconds due to seconds being in the denomitor of the fraction makes sense that more horsepower yields a shorter time to complete the quarter mile.
There is probably a way to explain this a lot simpiler but the fact is that you can't express the power, torque, or fastness of an engine by looking at a peak number because that only exist at one rpm or one instance in time, so this number is always changing. Therefore you have to look to maximize an area under a time curve. To make it even more simple your torque at peak horsepower (say 400) at 3200rpm, is more effective to what we desire (accelaration racing fastest quarter mile) even though it is not the maximum torque (say 600) at peak horsepower occuring at 1600rpms.
Analogous to this is the fact that with more horsepower I could tow more (move a bigger load through a bigger distance in a shorter amount of time with more horsepower), than with more torque. I put the emphasis on shorter because with more horsepower I will have towed more or the same amount but in a shorter amount of time because horsepower contains a time component in its definition and torque ignors this time component.