Power-torque

What can you get from these curves, how to read them, are they usefull? Post the one of your car

>What can you get from these curves,
Cancer

>how to read them
The line represents the value of torque or power at a given rpm

> are they useful
Not especially

In general, the flatter the torque curve, the better. Where both peak will tell you where you need to keep the engine at in order to get the most performance out of it. Unless you're driving an autotragic, which in that case, you don't really care about where they peak at all, you just care about how flat the torque curve is.

Horsepower has to take over when torque drops off so that's a good graph. For something that's not a V8 at least.

HP is a function of torque and RPM.

How your car uses them is based on the engine really. Some engines, like a lot of the japanese manufacturers, use low torque engines that rev high to get around lack of torque. The higher the RPM, the higher the HP.

Torque is what does the work, but the longer you can maintain torque and higher you can rev, the more usable power you'll have per gear.

The chart in your post is what a car without variable valve timing would have. Variable valve timing and ignition timing allow your engine to maintain that torque curve and by association have higher HP at the top end. (if I'm not mistaken).

>Torque is what does the work
Torque is a measure of force, HP is a measure of work. You can have a lot of torque but do no work at all.

>Horsepower has to take over when torque drops
>> are they useful
>Not especially

Does anyone on Veeky Forums actually know fucking anything? Torque is (roughly) the raw twisting force generated from the compression cycle at any rpm, and is a measure of how efficiently the engine is creating power at any speed. At peak torque the engine is perfectly happy, airflow is ideal, cam timing is ideal, and there are no notable issues. At higher rpms valve float may begin to pose a problem, the cam timing isn't optimized for that rpm, and you might run into airflow limitations. That's why you see torque drop off near redline, the engine is hitting a wall somewhere and struggling.

Horsepower is a measure of how well each compression cycle is creating power (torque), times the number of compression cycles in a given time. So as you increase in rpm, horsepower increases up until the amount of inneficiency outweighs the increase in number of compression cycles.

Shit I'm a dumbass, you're right. I was trying to remember some of my physics 130, that shit was like 6 years ago.

>HP a function of torque
Correct.
(Torque x RPM/2)/5252= HP

Dynos are rather used an instrument to tune the engine under load. The tuner mainly looks at the graph to reference fueling, timing, wastegate duty cycle, etc. We care more about seeing a positive result in the change we've made rather than squeezing out HP. The more we can create linearity in the curves, the better the engine will run and perform at all loads and RPM

So basically the horsepower has to take over when the torque starts to die. Just like I said.

It doesn't appear you understand what power and torque actually is

The specifics aren't really needed. Only need to know what's a good horsepower and torque curve.

Did you even fucking read what I posted? Horepower can't take over from torque, because they're totally different measurements. Horsepower continues to increase even when torque begins to fall because the number of compression cycles still outweighs the loss of torque. An engine with a perfectly flat torque curve from 0rpm-redline would result in a linear increase in horsepower over that same rpm range. If torque begins dropping, the gain in horsepower will decrease and eventually begin falling because it's just a measure of (Torque x RPM/2)/5252= HP as has already been stated.

Why are you even here? The specifics are what is interesting to mechanically minded people. And you can't know what a "good curve" is because you don't even know what you're looking at you moron.

On the topic of tuning, I have some input.

During tuning my coupe, I learned that having more conservative timing, with perfect AFR, is more desirable than advancing the timing as far as possible. If you advance the timing too much, your engine can experience spark knock. Modern engines typically can detect knock and retard the timing to compensate. If your engine is constantly retarding the timing, that is power left on the table and it's not working as smoothly as it could be.

The more aggressive the tune, the less smooth it felt.

You are correct that a healthy, efficiently running engine is better than one that is high strung and pushed to the absolute limit.

Yeah I don't know about . If airflow was ideal at WOT and peak torque RPM in the engine you would actually have a Volumetric Efficiency of 100% which doesn't exist. Engine load is also a factor at any given RPM and affects airflow significantly. Peak torque going up a hill will have a difference in airflow than going down one.

More anons are focusing on HP and torque here than understanding what a steady state Dyno even does.

Idiot

That's called 'Minimum Best Timing' and gives a great margin of safety for other factors such as heat and fuel detonation.

>Why are you even here

Because I'm the only one that has a car that's dyno'd it.

Fake
Horsepower is a function of torque and, therefor, horsepower and torque are always equal to each other at 5,280 RPM

retard alert

>5280
So close. It's 5252 RPM,

?????

Damn. I should have looked it up before running my mouth. Anyway, op's pic is fake. Why is 5280 in my head?

that's the number of feet in a mile

Haha fuck

as you can see it's kW and Nm so it isn't fake.

Only for retard units.

This isn't my dyno sheet, but it should be pretty close as they are both same engine on stock tune.
On this engine turbo, vvt, and direct injection are used together to make the torque curve as flat and wide as possible. If you look at how the HP increases while the torque stays pretty flat, this makes it feel like the car pushes you back in your seat, but it keeps pushing and pushing all the way to the top of the rev range until you have to shift. That constant push makes the car feel exciting and fast, so that's why manufacturers try to make a curve like that.

That car needs a tune pretty bad. Just to Smooth that power delivery if anything

nigga your shit is too lean

>muh flat torque curves
That's what gears are for you dumb stupid retard

*rich

...

Quick, post the most fucked up dyno sheet youve ever seen

This is true, not the smoothest it could be. Honestly not too bad for a factory tune from 2008 though.
I don't know why theirs is running 10's, mine runs at about 11.5 when I get in to the higher rpm range. I know that is still rich but it isn't that out of the ordinary for a safe tune on a high compression turbo motor.
I am planning on tuning it soon because of the reasons aforementioned, but even being a bit rough it is still a good example for OP.
Another thing I want to add is that this shows compromise between power and smoothness. Mazda wanted to give the car as much shove down low as they could, and in turn made the power delivery a bit rough. After I tune, the peak around 3.5 will be less pronounced so it wont kick you in the ass quite as much, but in turn the curve can be smoothed and made more linear.

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>that power spike
Honestly I think that counts

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Damn. Fucking Chebby trying to make a Turbo 4cyl that basically isn't worth revving over 5k.

Anybody know what pic related means in "seconds"? Is that actually time or does it translate to RPM?

>get in my tubro 4
>have to drive it like a diesel truck where the redline is at 5k
wew

Here's a NA8 Miata dyno I found off Google. Mine is stock other than catless exhaust, and has 230k miles on it.

As you can see, even at WOT 50hp doesn't come until over 3k.

>50hp doesn't come until over 3k
Ehh yes because it's not a powerful engine. At least it has a flat torque curve. Torque is a much better measurement for power than HP imo, ever since learning that HP is just calculated with torque.

HP just tricks stupid people. You can have a diesel truck that makes 800ft-lbs of torque but is only ~200hp and some fag on here will argue that his 210hp Subaru is more "powerful"

Even within your gear its better to have a broader torque band, it means you have to shift less often.

Peaky engines with a narrow torque band means you have shift more, and have more gears.

>Torque is a much better measurement for power than HP imo, ever since learning that HP is just calculated with torque.

I used to think this too, given Hp = (tq * rpm) / 5252. But, there's more to it than that - **Torque is rotational force, Horsepower is rotational WORK.**

Horsepower takes the rotational speed into the equation. More force at higher RPM means more WORK, which roughly translates to rotational ACCELERATION, which translates to you accelerating more quickly.

I should note that I used to do vehicle power testing for a motorcycle manufacturer.

incorrect

Yeah I understand. I guess it does make a difference on the track when every shift is right at redline.

But realistically driving the cars, you can have a 4cyl Honda that makes 170hp, or a 6cyl BMW that makes 170hp and both weight 3000lbs- you're taking the on-ramp and need to pick up speed from 30mph to 60mph, which one is going to feel better?

And that's something you notice a huge difference with when you actually drive the cars, especially passing people on the highway or doing a pull from 60mph to 120mph. One car feels like it has more to give while the the other is struggling.

this is where the dyno curves matter. you say that they both make 170 peak horsepower. when they are accelerating from 30 to 60 mph, which RPM's are their engines at? whichever one makes more torque at any particular RPM also makes more power at that RPM, so saying HP is meaningless except for at the top end is also incorrect

Answer me this, is a 2900lb car with 170bhp and 177lbft tq slow? Manual as well.

What is that a graph of?

Depends on:

-Gear ratios
-Final Drive ratio
-Outer diameter of tire
-Torque and HP at more than just ONE RPM at ONE throttle percentage.

You can calculate optimal shift points for maximum acceleration using a car's torque curve and transmission ratios.

Most likely "fuel used at each RPM by Engine Load segment."

git gud and it wont be a problem

I believe it's this
I pulled it from EcuTek's website so I'm not 100% sure. I just know how to read the data logs and live data from the client side software, I've never used the whole tuning suite.

RPM takes over for torque, in an abstract and not physically accurate sense.

1. You're wrong
2. This isn't "abstract." We live in a world where we can make 150,000,000°F bombs from bombarding atomic nuclei with protons. Understanding how a wheel accelerates is not difficult. It's just impulse, force, rotational momentum, and work.

I mean if you have a lot of RPM you don't need a lot of torque to make horsepower. Just saying it in a non-technical way.

Oh, well then yes, you're right.

Not true entirely true. HP is a function of torque, like I said earlier. Yes, a high revving engine will make HP, but you start to lose efficiency as you rev higher. Valve float, heat (and by association knock), and friction start to become limiting factors. But a nice high torque figure is going to be what decides the upper limit of your HP. That's why some motorcycles can rev up to 18,000 and make 180hp, but only have 80tq. RPM only gets you so far.

post em

fite me

not going to claim i can compete but it's not bad for a gaymobile and a naturally aspirated one at that

For racing, they tend to tune right until knock, then keep a tune either at that point, or retarded just slightly. There are some real power gains from slight knock (only detectable with an in-cylinder pressure sensor), but you play dangerous games with reliability.

This is all well and fine until your peak pressure creeps behind TDC, or your rate of pressure rise is almost vertical - then you should just stop lol.

This?

Pretty much, yeah.

What car?
So whatcha think? I can look up the ratios too? Would this hold a candle to an 86 or Miata at least?

It would destroy an '86 or miat unless it had a tall-ratio 4-sp slushbox.

Some of the later VVTI miats would be a tough race, though.

It's a 5 speed manual. Just to give an idea it revs at 3k at 70mph on highway, really fucking short gears imo for a modern car

For example:
>1994 Mazda Miata MX-5

0-60 mph 8.7 | Quarter mile 16.4

I'm having a hard time finding mk. V 2.5L Golf times, but it's probably in the high-15s if I had to guess.

>shifting 5 times to get across an intersection
>doing 4000rpm down the highway

Yeah no thanks.

Yeah I think it's 15.5 and supposedly 7.5-7.8 depending on source for 0-60. People keep telling me it's a slow POS and I've developed an inferiority complex. Wish it was a 1.8 or 2.0t desu, but this engine is supposed to be more reliable

I've beaten the piss out of a 5-sp beetle w/ the 2.5L. It's not terrible and it sounds okay. There's no reason to think it's a slow POS.

I went from a 19-psi 12.9-sec STi to my '95 miat and I'm fine with its acceleration. Enjoy what you've got.

Also it's a mkVI 2010

True enough man. I test drove a Golf R mkVII and damn you can accelerate in 3rd at 30mph like my car can in 2nd @ 5mph

And you're worried that it wouldn't keep up with a miat or 86? Holy balls bro. hint: go toegay and make love to that sweet beast.
Also,
>>>short gears ftw
My car does around 3k in 6th at 70mph kek

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Yeah, my tuner found the knock threshold real quick. Older VQs have a hard time on the limit because the knock sensors are so sensitive. They tend to knock slightly when the timing is advanced more than 2 degrees and it gets mixed in with false knock.

I ended up running race gas (102 octane at a local drag strip) as an experiment and it only reduced knock by about a 1/3. So 2/3 of the knock ended up being false. Which is craziness. He had to pull the timing some and mess with the full to completely eliminate it. I'm running 12.2 throughout the rev range at WOT now so slightly rich, but the knock is gone.

Haha based, thanks for the encouragement bro, to bad fl has shit roads

Running that rich at load is perfectly normal. Yeah knock sensors are real bitch, especially the early ones.

Example: the camry in 99 had an issue where it would always retard timing despite knock from the factory! Thus you had to run at least 91 octane even though the manual didn't say so. Turned out just to be an overly sensitive knock sensor. 1mz lyfe.

The ones are wayyyy better.

Thing is they aren't even that old, they are from late 2007 if I'm not mistaken. Shit thinks it's knocking straight out of the gate. I don't want to desensitize them (you can set the frequency range in EcuTek) because then it may miss real knock and I'm not tempting fate with reliability.

This was the second revision of the tune and you can see it was pulling timing at the top end, despite running rich also.