What they said

 

maybe with a nice set of DUNLOPS you can get 25 hp i think falkens give you a solid 21 Sorry bro had to do it.

 

99.9% of cars have and do advertise BHP not WHP. They measure what the engine delivers, not what is at the wheels.

 

 

(Now that this thread is fully off it's rocker from the first post...)

Can anyone direct me to the thread that shows me how to install a Mazda 3-rotor 20B into the Scion tC? I heard it fits using stock motor mounts and my stock transmission. Also someone said that the Scionspeed stage II that's in the mail bolts right on the 20B and comes with a full bridgeport install for the motor. I'm not a fan of 30mpg on the highway, and I love having to put 2-stroke oil in my gas tank every fillup.

(Any rotor heads in here other than me?)

 

Wheel (aka chassis) dynos are good for one thing: showing gains or losses after establishing a baseline. They offer nothing in the way of what the motor is actually putting to the ground, in a real world setting. Dyno pulls are done in the gear closest to a 1:1 ratio, with no wind resistance, no rolling resistance, where the weight of the car is not a factor, etc, etc.

If a car could actually use every HP that is shown on a dyno, they would all be a great deal faster-- evidenced by how a 100hp motorcycle can go 0-60 in 4 seconds, while a 100hp car takes about 10.

The point I was making is that the broadest point of the tC powerband (ignore the peaks, look at the span) puts down between 120-130hp. The peak HP, at say 65mph in 3rd gear, taking all of the drags into account, is around 130hp.

Penny-ante mods will effect that number negligibly. Think of it as "real world" or "final" horsepower. Big numbers may amaze family and friends, but basic physics will tell us how many horsepower it takes to move X number of pounds over Y distance in Z units of time. To move 3000lbs 1320 feet in 16 seconds takes about 100hp. Extrapolate from that what you will.

 

Here is how I see it. You can't measure the wind resistance on a given day, and say this is true numbers (for wind resistance is a variable, wind can blow from different directions, not from the front of the car to the rear all the time, and not at the same speed all the time). You can't determine the HP of a car accurately by driving it down the road and measuring the distance it took to get it from point A to point B. That would be measuring the speed, not the power. As for there being "no rolling resistance", I could have sworn that I read somewhere that the dyno machine produces a load for you. And that load can be adjusted at certain RPMs. I know it was howstuffworks.com


As far as the weight of the car, I don't see that having anything to do with how much power it puts down to the ground. I see that coming into play when you need to calculate the TIME it takes for you to get to point A from point B. If my capacity to lift a box is 100lbs, and say it takes me 5 mins to carry it to a desk down the hall. Then I trade it for a 20lb box, and it takes me 1 min to carry it down the hall. Just because I'm carring a box that weighs in at 20lb's now, dosen't mean that I still can't lift a 100lb box.

Again, a TIME/WEIGHT equation, not a HP equation. Same HP, but variance in weight produces the variance in time to overcome a certain distance. The fact is they still put down the same hp#'s. A Dyno is designed to get the hp#'s, not tell you how fast you would be able to move from 0-60. That you would have to figure up yourself. Not to mention, on a bike, the operator plays a bigger roll in how fast the bike will go from 0-60. If I weigh in at 300lbs and the bike is 350lbs, then that's a combined weight of 650lbs! of course I'm going to get out run by a guy that weighs in at 140lbs and on the same bike. But does that change our HP #'s and what the dyno said?


It appears you are factoring to many variables into the equation. Dyno is for one thing, and one thing only, get the # of ponnies going through to the ground. Not to measure how far you can travel in a given time with that power. If you can show me a TC putting only 130hp to the ground, then be my guest. If you want to start talking about wind resistance and weight and trying to measure it when it passes point A going at 100mph and calculating the time it takes it to reach point B, and try to tell me it's only putting out 130hp, then I would turn around and strip out the back seat, add some down force and tell you to re-run the test. I beat you will get different results.


Man...All this is hurting my brain... Don't make it more difficult than it already is.

 

I made a post earlier about the base dyno run and then adding an I/H/E. I was wrong about the magazine. It's not SuperStreet, it's the latest Modified mag. Here where the numbers they had.

BASE 139hp 145lb-ft.

ADDED AEM(Now TRD) intake

New #'s 142hp 149lb-ft.

ADDED DC Sports Axel Back exhaust

New #'s 147hp 152lb-ft.

ADDED DC Sports Header

New #'s 154hp 156lb-ft.


So they went from 139whp to 154whp and 145lb-ft to 156lb-ft with an I/H/E upgrade.

 

is the new TRD intake better then say the injen or weapon r?

 

Measuring the time it takes to accellerate to a given speed is not a valid measurement of power in this case. That only works for basic elementary physics problems where acceleration is constant. Acceleration for a car will not be a constant figure due to the power curve. Add to that the VARIABLES of wind resistance, rolling friction, moments of inertia, etc and you have one useless number at the end. The HP measurements spoke of relate to standing dyno runs with as many controlled variables as possible. These numbers can always vary. The purpose of stated HP figures is to give the most accurate measurable figures with as many variables controlled as is possibe. The dyno is the closest we can come to this. If we did it using some of the variables stated, they company would have to advertise "Somewhere between 130 and 150 HP" or something along those lines.

A brake dyno is not used to overstate the HP rating of the vehicle. A brake dyno removes most of the variables that lead to wildly changing measurements, which is why set of brake dynos performed properly will yeild more reliable results.

Wind resistance can change simply by allowing the car to get dirty, or by waxing it. So trying to account for this is not valid in the least for a manufacturer rating. Also, this tells you nothing of the power available at the wheels.

Put it this way.. when you buy a flashlight, do you want to know how much light it produces, or how much light it produces in fog? For that latter, what if you dont ever see fog? What good is the measurement then? Or even worse... how dense was the fog?

 

More than likely not. Then again, I don't have access to a dyno to see how much power I'm putting down with my mods.

 

You guys are missing the most important feature. Who cares what the number is? Isn't the goal to do the time and distance thing? Unless you are building a dyno queen, the concept is, if I make more power on the dyno, my car should be faster.

So really, why would I care about a dyno test, when in fact, I am most interested in solving the time/distance problem?

Why would I care about a dyno test run with fans blowing to simulate airflow for cooling, but certainly not the equal of 100+ mph air over the car's intake, exhaust, and cooling apparati?

Why would I care about a CAI dyno if the car is stationary? What if the location they chose for the intake is a very low pressure region while the car is in motion, but a very high pressure region while the car is stationary with fans blowing on it?

Dynos don't solve the real problem. They only provide a benchmark for others to test against, and I don't even want to get started about the irregularities of inertial dyno testing. I think it's pretty ridiculous that a dyno indicates a power change by just changing air pressure in the tires (as a Dynojet will). That's a whole different post.

 

y is da car so heavy close to 3000 pounds. like hitting the body frame it practically bends.

 

I like this guy more every day.

 

Which is my exact point about why the manufacturer states BHP. That at least removes many of the variables from the equation (not all, but a lot more than a wheel dyno does). A wheel dyno, as you said, is ok for checking for change, but not a small change.

 

Then you need more than just dyno testing. You need to reduce weight wherever you can, you would need to pick the right rim/tire combo, maximize downforce and drag. Not to mention add power to the engine. The adding power to the engine is where the dyno comes in, because obviously more power, means you are going to be reaching the given speed a lot faster than before. But how do you measure that power? Dyno will give you an indication of the benefits of your extra power. For example...

If I have 160hp and I travel from point A to B in 15secs. Then I bump that up to 180hp and I travel the same distance in 14secs. Then I can give a rough guess as to what it will take for me to travel that same distance in say 12secs.

Bottom line...Dyno's are good to have, because they give you an idea of how much faster you can travel from a given point to another point under that power.

 

^^ that is true as long as you take the whole power curve into consideration and integrate over the whole thing in the calculations. A point some forget is that a car will not provide constant accelleration and that making changes to power will also change the power curve. But, as you mentioned, you can get a ballpark estimate as to what you have changed and the result which is all you are really trying to do most of the time.

 

ooh integration... that whole calc 2 thing... simple terms engifinner. (im going for an ME degree so i know what your talkin about at least)

 

indeed...indeed. Then you start adding stuff into the equation like gear ratio changes, LSD modifications...and in turn the ability to adjust that power curve. And try to minimize where you experience the power dips and spikes to try and straighten out that power curve.


See....Playing Need For Speed and Gran Turismo does help people learn about cars...LOL.

 

I call it a symphony. Lots of individual instruments. Lots of possibilities to make music, and lots of possibilities to make nothing but noise.

I've seen enough dyno testing over the years to know that there are many tricks of the trade, including engine dynos that measure torque straight off the flywheel, so it is possible to make LOTS of claims. Great. Does it solve my problem of getting the car from A to B quicker/faster/more efficiently? Maybe yes, maybe no.

It's a symphony. That's why they're called tuners. Because they understand how to make music from what could be nothing but noise.