Yes, you definitely feel the torques.

They say people buy horsepower but drive torque...

how much for grade A horsepower? I think mine is a little on the lumpy side.

My neighbor has some torques though, maybe when he's on vacation i can take them for a spin.

Torque + gears determine acceleration. Power is speed dependent, but your butt can't feel speed for obvious reasons.
A lot of torque but overall low hp is useless because you can't use a good gear reduction ratio.

That dip is apparent on every N/A Subaru dyno chart you will probably see, its attributed to the intake manifold for the most part:

http://i15.photobucket.com/albums/a3...HEADERDYNO.jpg
http://www.ft86club.com/forums/attac...achmentid=4567

^ thats interesting

I have the same kinda scenario with my EJ251 (1999-2001 2.5RS engine). But its a single cam, non AVCS, oversquared engine.

vs Dual Cam, Dual AVCS, Squared engine.

There is quite a bit of difference between the EJ251 and FA20...

Yet we still see that same awkward dip.

Does the EJ20E and EJ204 and EJ254 see similar output characteristics? What about the FB20 and FB25? Id like to see them next to each other.

I'd like to see how the drop was deleted on the EJ25.

If the dip is manifold related then it is likely acoustics. It could be more that the manifold runner lengths are more similar (at least relative to the dip's rpm), even if the motors aren't.

But I would think that the AVCS could tune around most of it, compared to the older non-AVCS motors.

Hi everyone, new here. This SAE paper from Toyota has a manufacture dyno chart of the 2ZZ-GE if someone would like to overlay the dyno if possible.

That makes me try to visualize what the acoustics are like at the manifolds. Is it the really the length? or could it be the materials? no wait...the intake manifolds on the EJ251 are metal while FA20 are phenolic plastic.

What about the header...yeah very similar. Is it the OEM EL header causing this?

Check this out!
http://www.rs25.com/forums/f5/t48917...o-results.html
^
OBX header and a bit of tuning to smoothen out that dip quite a bit on the EJ25D.

Can I get a repost of the S2000 and BRZ on the same graph?

Maybe they'll do an access port tune for this thing. That would flatten out the rut a little bit at least.

It's the length that matters, because the air will pick up velocity and then as the valve shuts a wave starts to travel in the opposite direction at the speed of sound.

Also transfer from the exhaust negative pulse during overlap.

oOo you and Dim might be right. Im looking at other dyno comparisons of the EJ251 with different headers. Never really paid attention to acoustics until now.

This short OEM EL like this sees that awkward dip at 3000-4000
http://i644.photobucket.com/albums/u...ockHeaders.jpg

This longer OBX EL header smoothens out that 3k-4k dip on some dynos im looking at from other members.
http://i644.photobucket.com/albums/u...sHardware3.jpg

^ Also stock Subaru headers are connected 'wrong' based on firing order (compare with the stock FA20 on the stand). Just made for convenience.

So basically Hp is an enabler of torque? Torque moves you forward and hp determines how long that torque can be applied. Off topic I know. Ill discuss elsewhere.

Basic physics, go to school :P (in jest)

That's what she said.

If you are going to correct us on on a nuance, at least get it right. What you feel technically comes from the seat pushing you forward. Draw a free body diagram of your body when accelerating :D



If a balloon is floating in a car, and the car accelerates, does the balloon go backwards from the acceleration?? This was a junior level physics problem for my mechanics class :popcorn:

Lol Professor Bambbrose. Thank you for this.

It's more on-topic here than the usual threads that power vs torque comes up in. Power -more or less- tells you how quickly you can apply a torque.

Think of a bicycle. You apply a force to the pedal, which turns the crank. That force is applied to the chain, but can also be measured in terms of torque (rotating force) around the bottom bracket.

You can push a pedal hard when it's stopped or rotating slowly. The limit of how hard you can push on the pedal is akin to an engine's torque rating.

How fast you rotate the pedal is akin to an engine's speed.

If you downshift, it takes less force to push the pedal, but now you can pedal faster. The combination of how much force you apply and how quickly you pedal is akin to an engine's power.

If you downshift so that you're pushing half as hard but rotating twice as quickly, you'll deliver the same amount of power and accelerate the same. But if you downshift and can deliver the same force to the pedal twice as quickly, you'll have twice the wheel torque. Even if you push with 25% less force, but pedal twice as fast, you'll accelerate more than before the downshift.

Just like in a car: if you downshift so that you make more power, you make more wheel torque and accelerate more (even if you make less engine torque after the downshift).

It's not a perfect metaphor, but the principle is the same.

I'll see your FBD comment and raise. :D

What I posted is correct: what you feel *comes from* the force at the wheels (there's a reason I didn't write that what you feel *is* the force of the wheels). I originally drafted "What you feel is the seat pushing you, which comes from force at the wheels, which comes from wheel torque." but I decided it was unnecessarily wordy and too douchy to put it that way, so I trimmed it.

Besides, my post wasn't nuanced. This is nuanced: what you feel (unless you drive around topless) is your shirt pushing on you, which comes from the forces transfered from the tires to the wheels through the car to your seat to your clothes to you.

So that's not covered until junior year now? Back in my day, we did that one as a freshman. :D

I'll let someone else answer. Since we're off-topic anyway, here's some extra credit: Explain the differences, if any, for how it works for balloons filled with helium vs air.

Back in oh, 2010, we did that in high school :P
Balloons filled with air have no buoyant force.

Why join the right and left side of the headers together? Could not they be completely seperate?

I thought you was much older because you seem so knowledgeable on how the engine works. Age ain't nothing but a number.

That's about how old I thought he was, because of how much he thinks he knows. ;)

and you're the smartest one here, right?


as for engine and car dynamics theory, they don't teach that in high-school. Direct application of high-school physics to our questions only comes if you pick up extra material and just read up on it independently.

this is a neat little thing to read for those of you with genuine questions

http://phors.locost7.info/files/Beck..._of_Racing.pdf

also, with regards to tuning, here is a good book that talks about fuel injection, it's outdated (most of the cars that use the systems described are disappearing from our roads) But still good theory.

http://www.amazon.ca/Bosch-Fuel-Inje.../dp/0837603005

I had certainly went over the balloon concept earlier, but to actually solve it independently for homework is another story.

I'm actually quite impressed with the group of guys and our knowledge here at ft86. Great minds think alike?? :happy0180:

gotta specify that it's filled with helium


i had to look it up though :)

seriously though, how often does one drive with helium balloons floating in the car, haha

How else would it be floating :D

If you're travelling in a train that goes at the speed of light, and then you start walking toward the head of the train, are you going faster than light?


:lol:

it's all relative

Exactly the opposite. HP is a measure of how "quickly" the torque can be applied.

Think of it this way, torque is a measure of force, but instead of measuring how hard you can push, it measures how hard you can twist.

In a straight line, you've heard that work=force*distance right? What power measures is how fast you can do that work.

Now let's translate that to circular motion...

Work is now torque applied over a certain number of revolutions. So power is torque times revolutions over time. That's why we sometimes say that power is just a number derived from torque.

Imagine two engines with the same peak power, but one with low torque and one with high torque. We'll use perfectly flat torque curves for simplicity. That would mean that the low torque engine needs to rev at higher rpm to produce the same power as the high torque engine.

In theory, these engines placed into the same car could produce identical acceleration if they were geared appropriately. The low torque engine would just need to rev higher. The problem is, people don't like to rev their engines, and manufacturers don't like to gear that way because of cost, mileage and reliability.

And that's why most people think of torque numbers as being responsible for the acceleration that you feel. Because low torque engines aren't geared low enough to produce the same acceleration as high torque engines, and even if they were they might not be able to rev high enough to take advantage of that gearing.

yeah, the fact that there are really smart gear heads in here gives this forum a big edge, interesting character, and more topics.

Even im pushed to learn more, and i haven't been this active on a forum since 02-04 when i had a s14 i was trying to build.

I feel very much like this. I always feel when I high rev a 4banger that the car is in so much pain that something will break and I would be SOL. I hope the FR-S doesn't feel this way but I wonder if flat 4 engines feel buttery smooth like a V8 or I6?

I think he simply meant that 'the more you know, the more you realize you don't know'...I'll be the first to admit this and I've been eating, breathing and sleeping engines for the last seven years...on the engineering level (two of which college/internships and the rest in the field).

The curve looks similar to this http://oetuning.com/blog/wp-content/...o-CA91-600.jpg

(I know there are some big differences between the engines though...)

Yet the TQ on the BRZ engine doesn't seem to drop off, which makes me think there's some room up top.

So some of the exhaust energy can be transferred to other cylinders to assist in scavenging.

:P I'll take that lightheartedly. I have reasonable proficiency with physics, but that's about it, and I think I make that pretty clear when I post about stuff? Everyone has lots to learn afterall, and discussing things is a good way to learn. I get bored a lot and rant on about stuff.

As a general disclaimer, everything I say is based on empirical evidence I have seen and extrapolated using basic mechanics/thermo, I have no actual experience with this stuff, but hopefully that'll change someday soon.

And SUB, 2010 would be the last time I was in a physics class, but not the last time I was in high school. ;)