shiv@vishnu

iTrader: (20)

Delta Dash has a pretty nifty road dyno feature as well. Even our XMAP v3 will have such a road dyno feature. But to imply that road dynos provide inherently controlled and stable variables is a stretch IMHO. Last I checked, not even the tuning Lord himself (whoever that may be-- hey, let's have a evom poll!!!) has direct control over wind.

shiv

MalibuJack

iTrader: (5)

Although I don't have much to add to this thread, and I'm uncertain if this had been mentioned before, but there is a compromise when you road tune, since one of the arguments against it is that you cannot get quantifiable (SP?) data. Which is actually untrue, it really depends on the tools you have access to.

Chassis dyno's are just "Rolling Roads" where their values are calculations based on the speed of their drums, weight, etc.. This information CAN also be calculated on a road tune also, with the same level of accuracy (or should I say innacuracy) as a dyno. As long as you run the same stretch of road when your tuning, odds are the you will produce repeatable numbers (I have software that even does SAE correction so changing environment can also be taken into account)

This doesn't make the dyno worthless in any way.. But all of these things are tools, and just aren't mutually exclusive. A dyno is great to do consistent run to run tests to make quantifiable gains, but most dyno's cannot simulate real world conditions in such a way that you can find that 50% throttle stumble at X RPM, etc.. Dyno numbers do reflect peak values, and some can allow you to do the "Rolling road" testing (I think mustang offers that) and these are better than nothing. But cars live on the street, so ultimately the tuning needs to make it onto the street in the end anyway. (As shiv said though, you don't have control over some variables such as wind, but a dyno doesn't take other things into account that could affect performance either)

Without going into the legalities or safety of "Road tuning" (I guess I'm fortunate to have access to a private road if I need to do extensive testing) But as long as you can aquire data about speed, know the car's weight and how many RPM's the wheels turn per minute, you can calculate HP and Torque on the road since the calculations are no different. But be aware, these are just calculations. The key to a good tune is the Tuner, and his tools.. Period, regardless of the method he uses for tuning. Being methodical and scientific doesn't require a clean room, but it does require the instrumentation.. Accurate Knock detection, Wideband, EGT, comprehensive data logging (able to gather intake temp, coolant temp, Duty Cycle, TPS, etc), and a way to capture ALL of this data somewhere so your not being distracted (and have data to compare and digest with the appropriate analysis tools)

I do agree with both Dave and Shiv on some of their points, but moreso with Dave's comment about the dyno "Tempting" tuners and owners to keep whittling away from your safety margins to get peak "Braggable" numbers. Then I look at these dyno graphs on alot of cars, and they have a spike where they have peak torque, and it subsequently falls off quickly, thats not a good street tune, a good street tune should produce torque early and quickly, and not drop off by much if at all possible. (horsepower numbers are just a calculation of Torque vs speed, therefore the more torque you can produce at higher RPM the more HP you will calculate since the car can keep accelerating)

In the end, NOTHING is truly a precise measure of power.. But in engineering there is a difference between accuracy and precision, being accurate means you can measure your gains, being precise means you can compare them with others... I don't see any precision in any of these methods.

Noize

iTrader: (24)

Have fun in the UK you lucky fricker. Drive a T350C for me; TVR rules all.

shiv@vishnu

iTrader: (20)

That's a reflection on the dyno tuner, not the act of dyno tuning itself.

If you are talking about intertial dynos, then yes, they derive/estimate whp by calculating dv/dt of the big heavy drums of fixed mass. If you are talking about a load bearing dyno, then it's very different as they actually measure wheel hp measuring the force (in kg, lbs,. etc) the speed-controlled rollers put on a load cell (one per axle). It is just like an engine dyno that has been extended to put load on a tires instead of the flywheel. This is the measurement of horsepower (whether it be flywheel or wheel), in its most direct sense, and it cannot be dilluted by argument into meaning anything less than that.

Any further argument is going to be on whether (er weather) dyno conditions can perfectly replicate road conditions which can vary greatly depending vehicle speed, airflow, ramp up rate/gear selection, temperature, humidity, altitude, etc,. Clearly, it can't. But it can come awfully close, most of the time of course.

However, dyno testing is the only kind of hp testing that comes close to holding all variable equal. And in any scientific testing, this is the first requirment. Without it, everything else is just statistical noise to some degree.

In application however, all things held equal, about the only thing separating a dyno test from a real road test is aiflow through the radiator/IC. But judging by the ahem... less-than-scientific testing many do when testing/promoting minor little components such as intercoolers, intakes, etc,., this should be of no concern to the tuning community in general

shiv

MalibuJack

iTrader: (5)

Though I totally agree with you, what you are measuring is torque.

horsepower is a made up number calculated from torque originally intended compare how efficient a machine is over a horse at moving things..

someone decided to create a formula to translate the two after realizing it was easier to measure torque than it was to compare how many horses could drag the same weight the same distance at the same speed..

All joking aside though, I don't think any method is better or worse, I just think the right way to do the job is a little of both, assuming you have access to all the tools.

In reality, we all know in the racing world most tuning is done at the track anyway at least the refining of the tuning.. It should be no different for anyone else looking to produce good power, and drivability (Reliability)

shiv@vishnu

iTrader: (20)

If one is measuring Torque and RPM (with an inductive pick-up or even a simple mph/rpm factor) then one is also measuring HP.

shiv

Dyno4mance

iTrader: (5)

I think this is what Malibu is refering to...Something I found a while back

Force, Work and Time
If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.
In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.
Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.
Everybody else said OK. :-)
For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.
Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.
Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.
OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:

Torque * RPM

Horsepower = ------------

5252

This is not a debatable item. It's the way it's done. Period.
The Case For Torque
Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.
You don't believe all this?
Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)
The Case For Horsepower
OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.
For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).
On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:
6 HP.
Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.
At The Dragstrip
OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-).
A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows:

Engine Peak HP @ RPM Peak Torque @ RPM

------ ------------- -----------------

L98 250 @ 4000 340 @ 3200

LT1 300 @ 5000 340 @ 3600

The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.
First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula:

Horsepower * 5252

Torque = -----------------

RPM

If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point.
On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline.
So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.
Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift.
There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.
A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. OK, so we'd need to have virtually all the moving parts made out of unobtanium :-), and some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me.
If you raced a stock LT1 with this car, they would launch together, but, somewhere around the 60 foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you'd wouldn't be able to see that due to the distance between you as you crossed the line, *still in first gear*, and pulling like crazy.
I've got a computer simulation that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being powershifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph, all in first gear, of course. It doesn't pull any harder, but it sure as hell pulls longer :-). It's also making *900* hp, at 15,000 rpm.
Of course, folks who are knowledgeable about drag racing are now openly snickering, because they've read the preceeding paragraph, and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Of course that's true, but I remind these same folks that any self-respecting engine that propels a Vette into the nines is also making a whole bunch more than 340 foot pounds of torque.
That does bring up another point, though. Essentially, a more "real" Corvette running 135 mph in a quarter mile (maybe a mega big block) might be making 700-800 foot pounds of torque, and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion, but it would also get from here to way over there a bunch quicker.
On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (3.45 is stock) in our fantasy LT1, with slicks and other chassis mods, we'd be in the nines just as easily as the big block would, and thus save face :-). The mechanical advantage of such a nonsensical rear gear would allow our combination to pull just as hard as the big block, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends. :-)
The only modification to the preceeding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a stiff rear gear, and that argument is outside of the scope of this already massive document. Another time, maybe, if you can stand it :-).
At The Bonneville Salt Flats
Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and thus have more effective torque *at the drive wheels*.
Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is *it*. An example, yet again, of the LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear, it will generate some level of torque (340 foot pounds times whatever overall gearing) at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear).
However, if you re-gear the car so it is operating at the power peak (5000 rpm) *at the same car speed*, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed.
Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.
"Modernizing" The 18th Century
OK. For the final-final point (Really. I Promise.), what if we ditched that water wheel, and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but, assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque), and gear it down to a 12 rpm output. Result? We'd have over *131,000* foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to :-).
The Only Thing You Really Need to Know
Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)
Thanks for your time.
Bruce

Eric Lyublinsky

iTrader: (5)

I never used the new g-tech but willing to give it a try . But on a dyno you can tell if the car can run more timing or not by the dips and hills on the TQ curve. I don't think G-tech would be as accurate. Also if you can set me up with a proper wideband 02 A/F with a accurate EGT gauge and G-tech for 400.00 bucks I would really be instreasted to buy that because last time I check a decent wide band 02 is around 400 and change and egt gauges 130, getch at least 200.

But if you got the hook up I'm game!

ShapeGSX

hp is not a made up number. It is no more made up than if you measured acceleration by calculating the derivative of a speed curve.

hp is the rate at which you are doing work, just as acceleration is the rate at which your speed is increasing.

ShapeGSX

I soldered my techedge wideband kit together. It cost me $180 total including the sensor.

I wouldn't use an EGT at all, nor a gtech. The techedge wideband kit will take a type-k thermocouple as a datalogable input, though. 3 of them, in fact. And RPM, and 3 other 0-5V sensor inputs as well.

MalibuJack

iTrader: (5)

I don't know that there is really a good method of testing some things, as you said alot of these product tests are not scientific and usually don't offer much gains.. The intake and filter mods are a good example since I have also seen they don't offer any real gains and only end up causing problems..

Eric Lyublinsky

iTrader: (5)

ya but I don't want to do that

MalibuJack

iTrader: (5)

I meant it more figuratively than literally..

MalibuJack

iTrader: (5)

Dyno4mance's post actually says most of what I was eluding to.. I guess I come from an old school engineering background where these relationships are alot more obvious to me.. Should be more obvious to anyone who gets their *** handed to them at the top-end by a car that you would otherwise be able to beat in the quarter, other factors notwithstanding.

Its not that horsepower isn't a valid measure of power, its just that torque tells a better story of how quick and fast a car is.. Thats why some of these cars seem to make relatively low torque compared to their horsepower numbers, the difference is they can maintain that torque where other combinations would fall off quickly, and therefore a much lower HP number.. IN theory both cars could make exactly the same peak torque numbers.

Oh well, This is going pretty off topic, other than it being a good lesson in HOW things work and that the tools you use to measure your gains aren't going to matter much as long as its consistent and repeatable.. for the most part for what we do, they are..

TURBODAWG

iTrader: (54)

As Dyno4mance said in his argument. You can't measure HP. You can however measure torque and derive from the formula HP if you have an RPM feedback.

Work/Energy can be measured easily. Power is something that must be derived from a time based derivative.

Brian