HP values from Dynos

[Techno97]

I understand a Dyno loads an engine already at a high rpm and takes it down for the different rpm values.
If the engine were instead accelerated up while under a dyno load would this result in different readings?

It was mentioned that for an Outboard engine maximum hp is a deception as the engine needs low end power to get the boat on plane and has no gear box to help it.
While on a Dyno the engine may obtain 400 hp, but if it can't get the boat on plane this value would be useless(deception).

Is there a value more useful than maximum HP or max torque to describe an engines power output?

 

[MaxRaceSoftware]

Techno97...on a SuperFlow SF-901 dyno
you test the engine by accelerating from a lower RPM point
to a higher RPM point ...it gives you torque and HP at
every 100 RPMs between your Lower and Upper RPM points you've setup .

i don't know whose dyno you are using and what type of dyno , but on my dyno if i see a Torque/HP gain the boat
"ALWAYS" goes faster ..better change places where you dyno ?

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[TonyG714]

Larry,
This question belongs in this thread rather than in the other thread where I asked it:

If HP rating is a factored result of Torque, arent' we just chasing squirrel tales if we constantly rate and judge our engines by HP ratings? Or is HP a viable rating as it includes engine momentum from RPM's?

Torque is something I can envision in the ft/lb rating. But I don't understand how HP rating is more beneficial.

Tony

 

[MaxRaceSoftware]

Tony ..... there are these 2 guys ....both have the same exact cars,weights, and components ..except

RacerA says he has 400 lbs/ft torque engine
and RacerB says he has 400 lbs/ft torque engine

then RacerB asks RacerA ,
"RacerA , why is your car faster than mine?"

RacerA says "my engine is 400 lbs torque @ 5000 rpms , and
your engine is 400 lbs torque @ 3000 rpms"

RacerB says"I still don't see a bunch of difference
between our 2 engines ???"

RacerA says "Maybe there is a better way to describe the
performance differences ???"
"How about a new term called HorsePower ???"
" HP = ( Torque * RPM ) / 5252 "

RacerA says " Now lets look at our engines ....
yours is (400*3000)/5252=228.5 HP
and mine is (400*5000)/5252=380.8 HP "

RacerB says "WoW ..now i can really understand the
differences between our two cars"

RacerB says "your engine is 152.3 HP more than mine !!!"

RacerB says "this new HP term is a lot more convienent
to talk about performance with than trying
to multiply torque times RPM in our heads
all the time !!!"







Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[MaxRaceSoftware]

Tony

i'd rather have an 800 HP / 600 lbs. Torque engine

than a

600 HP / 600 lbs. Torque engine

i'll go faster with the 800 HP engine everytime !!!

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[MaxRaceSoftware]

Tony,

i dyno 2 468 cid BBC Boat engines

one has 700 HP and 600 Torque

the other has 600 HP and 600 Torque

1-Why does the 700 HP engine go more MPH in the Boat ????

2-and now the biggest most important question ???
"How come the Boat keeps going faster PAST the peak torque RPM point " ????????????????????????????????????

"Why doesn't the boat just stop accelerating and level-off once the engine hits the peak torque RPM-point ????????????????????????????????

3-How can any engine CONTINUE accelerating past its peak torque RPM-point ?????????????"

Answers ;
1-HorsePower
2-HorsePower , HorsePower
3-HorsePower


HorsePower = ( Torque * RPM ) / 5252

if you have more HP , you have more Torque at that RPM
if you have more Torque at that RPM , you have more HP



Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[TonyG714]

Larry) i'd rather have an 800 HP / 600 lbs. Torque engine than a 600 HP / 600 lbs. Torque engine
i'll go faster with the 800 HP engine everytime !!!

Tony)A 800HP/600lb torque motor would probably have a wide torque curve rather than a peaky/jumpy one or else have torque point in a higher RPM range where the RPM factor can have more of an influence on it's HP rating.?

I guess with your examples what I'm trying to ask is Since horspower figures are a mathmatical result on torque rating, couldn't your 3 answers also be Torque, Torque, Torque????

Also, do your dyno's measure Torque and compute it to HP or is there an actual physical resistance standard to measure HP?

Larry) 2-and now the biggest most important question ???
"How come the Boat keeps going faster PAST the peak torque RPM point " ????????????????????????????????????

Tony) Well, I'd venture to guess that there is ample *torque* past peak torque-rpm point to overcome boat/water friction and aerodynamic drag and still maintain or advance propeller speed. ??

Does the Math of HP*5252/RPM's also equal torque?

Not trying to get under your skin Larry lol, I sent my tornado money on thursday.. just trying to understand better the real world usefullness of HP numbers.

Is one of the goals of engine building to get high HP readings and if so, aren't you just trying to get as high a torque reading as late in RPMs as possible?

Does the engine momentum have something to do with the usefullness of it's power somewhat beyond its simple torque and HP chart rating? Would it be more beneficial to have a peak 600HP rating at 8000 RPM's or at 6000 RPM's?

And what about the fuel efficiency part for regular auto's?

The question guy,
Tony

 

[Techno97]

My Dyno question was answered but this also lead to the thinking that high HP values are always better, they're not. Past a certain point you are heavily into the compromise region and are stealing from something else to get the high HP. This could result in an engine with very high HP readings but unusable in the application.
If you have plenty of high end HP on an outboard (2-cycle) and run a large prop(32&quot the engine may not be able to get the boat on plane.( very low HP at low rpms) There are ways around this but eventually you still require a certain amount of low end power. If a tunnel hull you have to have enough power to fly it. If you don't then the high HP figure is never reached. the 32" prop is there from start to top end.

It's this total power curve that I was wondering about.
Is there some other method for comparing where the power is made and how much is made as a simple number for the whole range?

In the 1st example the 228 hp engine may develop more hp then the 380 hp engine at some point, in this case how would you decide which had more hp for the total range? Not maximum.

 

[MaxRaceSoftware]

I guess with your examples what I'm trying to ask is Since horspower figures are a mathmatical result on torque rating, couldn't your 3 answers also be Torque, Torque, Torque????
=================================================

Torque,Torque,Torque
Tony, thats absolutely correct ..buts its Torque times RPM

HP is just a calculated number , but the car very much responds to this number .
-----------------------

Tony...what i look for on my dyno when dyno testing is the best combination to achieve the greatest "AVERAGE HP"
in the "USEABLE RPM-range" the car will accelerate in

with onboard data logger or computer program, you can
calculate what RPM the car has to launch/leave at and what shift points, and what RPM it will fall back to after shifting, and what RPM it will cross at ....then on the dyno
you try to maximize gains in those ranges to get the most avearge HP possible within these ranges ...

You never go after one big HorsePower number , thats a mistake made by many , ...don't look at that one big HP number, but instead find the combination that makes the most "AVERAGE HP" in the RPM range your application will see down the track

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[MaxRaceSoftware]

More info

i've had one particular SS racer with a Chevy SBC engine
..when he 1st came to the dyno years ago , he made
535 HP and 465 to 470 Torque

thru the years hes come to the dyno many times and has made
a bunch of changes and sometimes we pickup pretty much HP gains but no peak-torque gains , the peak-torque remains basically around 465 to 470 lbs....yet every time , we pickup HP , the car goes faster down the track in the real world !!!

if we loose HP but the peak-torque basically still remains the same, the car always slows down

when i say we are picking up HP i mean AVERAGE HP
and sometimes more peak HP also , but peak torque remains the same, and the car runs faster down the track.

this is just one racer i'm using as an example , but there have been a great number of other racers that have similar results

what i'm trying to say is,
if you want to start talking about torque then you have to really talk about average torque in a certain rpm-range and then likewise talk about average HP in a certain rpm-range
when comparing two engines ..you just can't talk about one peak torque point or one peak HP point and completely judge the performance of an engine from its peak points.

it could have a very narrow peaky torque/hp curve
and nothing else, and would only like a 5 or 6 speed and very light car.

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[MaxRaceSoftware]

In the 1st example the 228 hp engine may develop more hp then the 380 hp engine at some point, in this case how would you decide which had more hp for the total range? Not maximum.
=====================================

i look for the highest average torque and hp output in the rpm-range i needed for the application.

i know what you mean about the boat getting on plane
if the power curve is too high ...the answer would be transmission gears if legal or affordable/practical..if not you usually go to a larger engine so you can make more torque sooner if legal.....
what would happen if you took transmissions away from racers
and made them all run the same tire and a 3.20 rear gear ?
then they would be building very large CID engines with
wide torque/power curves . Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[MaxRaceSoftware]

Would it be more beneficial to have a peak 600HP rating at 8000 RPM's or at 6000 RPM's?
==============================
Thats a good question .

it would be better at 6000 rpms for durability

but in drag racing most classes are structured by weight to cubic inches ,,,then this means you have to build the smallest cid for the class and make the most HP/CID ratio possible ..then this forces you to make as much torque as you can, as high as possible ..if you look at the sucessful trend in dragracing , its been constantly moving HP/Torque curve higher to increase HP/CID ratios

no class i know of has "sucessfully" went in the opposite direction .

i think if you look at all forms of MotorSports you will see the same exact trend in engine building .


Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

 

[carnage]

Re: Techno97
It's this total power curve that I was wondering about.
Is there some other method for comparing where the power is made and how much is made as a simple number for the whole range?

I would suggest that after you determine the useable RPM range that you take a HP graph and determine the area under the HP curve within the RPM range. This will give you a number to compare aginst while tuneing the engine.
This just won't give you a number you can tell your buddies like HP does.

 

[Gearhead47]

In reference to the last question from Techno97, each of you are mostly correct in your analysis. Torque and HP are what we are all looking for, but we need to have them in a usable RPM range.

As per MaxRace, the SuperFlo 901 can measure the power in an accelerated state which correlates more to real life than a steady state dyno. (By the way an accelerated dyno output reading will be lower than a steady state test. The backwards pull may even measure higher values as the engine in tha case is trying to keep the power from coming down, and not measuring the point of accelerating up. This type of pull is only good to measure what happens in a gear change.)

The overall combination of induction system (Intake, Heads, Exhaust, Camshaft) all come into play on where the power is made. In a boat or car the combination then needs to be matched to the converter/clutch, shift and gear combination or prop/impeller on a boat.

For an example, say we have this engine of 800 HP at 7000 RPM which is a peak torque of 600 at 7000 RPM. (The peak HP would even be at some 1000 to 2000 RPM higher.) In a car we would need to set the converter stall over 7000 RPM for peak performance and shift some 300 to 500 RPM over peak HP. If the converter would only stall 4500 in this application, the car would not fall out of a tree as it would take forever for the engine to reach 7000. A jetpump in a jetboat is most effecient in the 5500 to 6500 range. Again the boat may never get to the useful power range of the above example. It has to have enough power to get the engine into the RPM band. (If a jetpump impellar is cut to allow the engine to operate over 7000 RPM, it will then not move enough water to propel the craft)

In these cases, we still desire to achieve the highest amount of torque available, but at a useful RPM. In these cases the induction system components will need to be sized smaller to achieve peak torque in a useful operation range. So, in the example of a jetboat, 600 ft lbs of torque at 6000 RPM (685 HP) WILL run quicker and faster than 600 ft. lbs of torque at 7000 RPM (800 HP)even though the later is of larger HP. It is the overall power we are dealing with in a useful band.

So, in the situation of the prop boat, it may take a number of dyno test to correlate the torque needed to get the boat up and the engine to the power range. In actual use, an engine can accelerate any vehicle from the RPM point of Peak Torque UP quicker than it can accelerate an engine from a lower RPM TO the peak torque RPM. Time of acceleration is time on the track.

This is one reason we always set the converter stalls at a point over peak torque. We want to make sure that in any weather condition, the engine will run from peak torque up.

This info is my opinion and I hope will serve as some help understanding various power curves. Other thoughts?

 

[TonyG714]

Highest torque rating within the desired power curve seems like it is the goal to pursue. If the torque figure is computated as HP it doesn't matter.
For drag racing purposes, getting max torque at a high rpm range seems to be the goal to gain the benefit of engine RPM's
For boating, a midrange seems needed to have enough power down low to get the boat up and still have good cruising and water skier pulling power.

For towing purposes, alot depends on gear ratio and transmission. I just had a 460 motor built. I have 3.55 rear with a ZF-5 speed overdrive transmission. I went with better quality items such as clevite bearings, Keith Black Hyper pistons, some Crane roller rockers and a roller cam chain. Stock heads and stock intake and holly/motocraft 650cfm carb. I left the cam choice up to the engine builder but told him my gearing and my towing purposes. He went with the 260 comp cams Hi energy cam. I've had the truck back about 2 weeks and sometimes I question the cam choice. The motor pulls different than engine I had before. It seems to have more power, but I have to go higher in the RPM range to get it. I maybe should have gone with the RV cam because of my 3.55's. It claims to make power from 800 rpms and up while the 260 cam starts at 1200 RPM's.
However, some of my thoughts were to be able to pull 10,000 lb trailers rather than 7,000 lb trailers.
Since the torque is higher in the RPM range I most likely have more Horsepower, but my question is if Horsepower rating helps pull trailers? Is there any advantage to having a similar torque rating (say 400 ft lbs) at higher RPM's (more horsepower) when it comes to pulling trailers?.
Or does it all come down to gearing?

Tony G

 

[MaxRaceSoftware]

Tony, thanks for the Tornado money !!!
if you email me your address, i'll send you some CDs
with dyno testing videos and pics
-------------------------------------------------------

in my old Chevy Suburban, i had a SBC 406 cid with the
Comp Cams 260HE ...had 3.08 rear gears and Turbo 350
with stock OEM converter ...i used it to pull my dragster trailer and everday use ...the CC260HE cam seemed to work very good in this combo.....later on when i rebuilt
the engine , i put in the CC270 cam, it made 419 HP
at 5500 rpm , but the very low RPM range and towing RPM range was a little worse than the CC260

i never pulled anything like 10,000 lbs , but it seems like the CC260HE with a 460 cid size engine should work pretty good.

check out Ford's ERG-valve operation ?

========================================================
Highest torque rating within the desired power curve seems like it is the goal to pursue. ---TonyG
=========================================================

Tony, you answered your own question .
even when pulling 10,000 Lbs. , it still is highest
"Average" torque within the desired RPM-range

Trans gear ratios and number of gears
and rear gear ratios ..will all mulitply torque
..just have to put together a combo of gear ratios and
useable engine torque/hp curve that works best in your desired RPM-range .

if you don't want to go back to original cam, then you might have to change rear gear ratios to keep engine in new higher RPM-range for a longer period of time
Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

Support Israel - Genesis 12:3