deezo

iTrader: (3)

There was a discussion yesterday about drafting in highway racing and a few people on the board seem to think that drafting doesn't work until your over 100mph. People, this is your chance to tell me what you think about the effect of the atmosphere plays on the Maxima at any speed.

Russ wants me to prove him wrong in his statement that drafting only work from 100mph on up. Besides drafting at lower speeds myself, here is my other proof:

Different vehicles come in different shapes and sizes(we all know this) and all have a different drag coefficient. I know and believe that drag from the atmosphere occurs at any speed. At low speeds (under 30mph), the drag is not enough to cause real resistance so it wouldn't make sense to draft someone at that low of a speed because your low end TQ and some HP play the role getting the car moving. Getting up into the higher speeds (40mph and up), your aerodynamics starts to come into play (where in a stock Maxima, HP will start to diminish). Stick you hand out of the window at 40mph and you will see that there is a great resistance for the car to push itself through.

Do you believe that a drafting for buses or trucks start at 100mph also? Negative. This is why you'll notice truckers get into convoys (whether small or large) to conserve fuel. The truckers cut the atmosphere for each other to become more efficient. Althought newer truck are more aerodynamic, they are still big vehicles and need all of the efficiency they can get. If the Maxima was shaped like a block, it would have so much drag and would need to draft at a lower speed to be efficient.

All in all, you can't compare full blown race cars to Maxima when drafting because the racers are far more aerodynamic than Maximas. So for a more aerodynamic car, drafting would play more of a role at higher speeds than it would for a Maxima. The same can be said for trucks, buses, and lets throw in motorcycles for that matter. Maxima's do not need to hit 100mph before drafting will start to work for it.

Chinkzilla

I personally agree with you, except the hp vs tq thing which is a whole other discussion.

But there is a simple test to settle this. You and another friend with a maxima, assuming you have similar or no mods, take a road trip. Fill up at the beginning, then one of you draft the other. After a reasonable distance, pull over for snacks and see who has more gas left over.

2DMax

iTrader: (2)

I agree, I don't think you have to do 100+ to benefit from drafting on the highway. I think anything that can part the air in front of you will benefit you, as long as you are not left in a turbulant wake.

Ramius83

I totally agree with you.....

Dave B

You can't compare the drag of a semi to the drag of a Maxima. At lower speeds, the semi will be more affected by drag simply because it has far more frontal area, high center of gravity, and poor overall shape. The drag at 40mph is very minimal and I doubt it could even be measured accurately. It's generally accepted that at around 80-90mph is when drag starts to take a real toll on a passenger car/truck.

Sticking your hand out the window is meaningless. Usually when people stick their hand out the window, they use the palm of their hand. This isn't an accurate representation because the frontal area of your hand compared to it's size is HUGE. Try turning your hand so that it's horizontal and tell me what the drag feels like. Also, the front window of a car is a very turbulent area anyways so wind resistance will feel more dramatic.

I think people are blowing this whole drafting thing out of proportion too. First off, you need to be right on the bumper of a car to get effective drafting (ie watch NASCAR). If you're too far back, you'll get caught in turbulent air. Secondly, the burst of power you get from the drafting only lasts a few seconds when attempt to pass your opponent. After that burst of passing power, you're back into the drag. Drafting isn't gonna let you close in a 6 car lead like in Emax's run against the BMW.



Dave

deezo

iTrader: (3)

Dave, you don't know what you're talking about and if you understood what I was saying is that you can't compare a race car drafting to highway drafting. I comparing the 2 types of vehicles (car vs truck or bus) because every vehicle is different. Stop trying to make an argument out of everything and get the facts straight. Again, you don't know what you're talking about.

When I get more time, I'll explain it to you again.

2ndMAX

I once took a trip in my dads Expedition (equipped with a nose mask) from NY to PA. At speeds between above 60 mph I'd notice that the mask would wisk around and flap like crazy. But when travelling two car lenghts behind another vehicle the mask stop flapping around. How much difference drafting at a 2 car length distance makes is obviusly very small. And I was driving an Expedition which has plenty frontal area. But if you were on a race track I'd say that a run from 60 mph+ down a straight away with a car lenght between you and the leader would produce enough draft to close up on him. Of course there are many variables and other factors that will always have someone doubting your theory. But you're right! A reduction of wind/air resistance is always welcome. Just look at the underbody of the G35, think they did that just for kicks???? They did it to cut down on air resistance, which is similar (not the same!) to the effect of drafting another car.

Good luck with the haters, they're probably coming for us both right now.

dmBK

iTrader: (3)

I think Dave has valid points - unless you're sitting on the bumper of the car in front of you, you're in turbulent air. And unless you're going over 100mph, there is no point in drafting. I think the air resistance is geometrically proportional to your speed, so if you were going 120, you'd encounter much, much more resistance than going 90mph.

deezo

iTrader: (3)

Well think of it like this, when you are driving over 100mph, it takes longer for your car to accelerate to 140mph. Why??? There is enormous drag/resistance being created by you car moving through the atmosphere and your front bumper is feeling the blunt of this. Now say your around the maxima point of your HP range in RPM's, your car is losing the capability to continue accelerating at the same rate as you would from 0-60 or 30-70. The TQ gets you moving and when the TQ drops the HP takes over. MY Toyota pickup is a good example for this because on very windy days, I couldn't get the thing over 75 (no lie) and it wasn't very aerodynamic.

deezo

iTrader: (3)

That's not true. Drag coefficients is proportional to the cars shape.

Dave B

No. The faster you go, the more the drag takes a toll on the car. The CF remains constant, but the faster you go, more air is being displaced further in front of the car. The more you displace the air, the more the energy that is involved. Things don't move without energy. Get it? Those "smoke" slip stream devices they use to test a car's aerodynamics are moving at speeds well over 90mph. There's a reason for that.


Dave

deezo

iTrader: (3)

So why is it different for different vehicles? Relook at what your typing here Dave. I just said that the DC is proportional to the cars shape. The point I am making is that drag is different for different vehicles and you don't need to drive 100mph in a Maxima to enable drafting.

wdave

It's really pretty simple - drafting will reduce wind drag at any speed for almost any vehicle, how much is the variable. The Max has a pretty low CD so the change isn't that big. The size of the wake you're following has an effect too - a truck makes a much bigger hole than a Miata. There's no magic speed where it helps or not, it just matters whether it will make a measurable difference.

Dave B

No one is arguing the advantage of the CF of drag. The question is when does drag become a real factor in performance. The slicker the shape, the better the car feels at high speed. The G35 has very little drag which gives it good feed back at higher speeds. The reason Infiniti did the underbody work was mostly to reduce lift at high speeds and to reduce noise. At 70mph, you wouldn't know the difference between a G35 with the underbody work or one without.

Years back, MT did a test of convertibles running the 1/4 mile with their tops down. The Trans Am (LT1) auto convertible ran a 14.5@98 with the top down. With the top up it ran a 14.4@99. The drag with the top down was over .6 and with the top up it was slightly over .3 (something like .33). That kind of difference in drag is very significant. They also timed the run from 0-120mph and the top-up TA accelerated harder with much of the drop in time occuring after 100mph. See what we're getting at? Only at higher speeds does drag really come into play.

Here's another one.

Ford Lightning SVT 385hp/450tq, huge drag (probably over .55), 5000lb
C5 350hp/350tq, .31 drag, 3200lbs, automatic

Lightning 1/4 13.8@101mph
C5 auto 1/4 13.5@104mph

Even with significantly worse CF and a worse power to weight ratio, the Lightning is nearly toe to toe with the C5 in the 1/4. After 90mph is when the C5 says goodbye.

Yet another example: Sport Bikes
Sport bikes have huge power to weight ratios which would lead one to believe that they pocess huge topends. Truth is, they don't. They can rip up the 1/4mile in 10-11 seconds, but their topend is typically limited to around 160mph due to drag. A sport bike's drag is huge because of their massive frontal area. Only a few bikes have broken the 180mph barrier (Hybusa, ZX12, Blackhawk) and that's because of their massive displacement.


Dave

PhatGuy

Isn't "a few seconds" a world of difference at any speed?

Dave B

Not when you're talking about cars with the same CF and power to weight. All it's going to allow you to do is have enough power to overtake your opponent.....if you do it right.


Dave

Rob'sAE

I have to agree, that when looking from a standpoint of efficency there is the possibilty for great gains. From a standpoint of performance, in a Maxima there is not enought speed or Tq/Hp to make a really big difference. Take for example, if you were to ride behind a semi about 1 car length back, (DO NOT DO THIS UNLESS YOU WANT TO REPAINT YOUR HOOD AFTER THE TRIP) and stayed behind him doing 60-65 Mph for say 1 full tank of gas I guarantee that you would get considerably better gas mileage than if you were cruising by your self, or even in front of the semi. It's not that it lowers rpm's on your engine for any given speed, but it takes less gas to keep a given rpm because almost half of your air friction is removed. (front air friction is RESISTANCE, rear air friction is DRAG.) In NASCAR being 2 inches off of someone's bumber not only helps remove your frontal air friction, but removes the drag off of the other car. In racing they have a saying that "2 cars can go faster than 1", and with good point. The car in front takes the chore of RESISTANCE and the one in the back takes the chore of the DRAG. So as far as perfomance goes, in our Maxima's there is little to be gained at any speed, but as far as efficiency goes there is the possibility for great gains, (depends on how big the vehicle in front of you is and how close you feel like riding behind him(which in turn depends on how often you like to repaint)).

This is my 2 cents, more like a dollar twenty, but that is what I know for fact, things i have tested in mine and other cars and things i have read and witnessed.

dmBK

iTrader: (3)

if we're talking about the same car, wouldn't the effort required to push it from 110 to 120 would be greater than pushing it from 60 to 70?

PhatGuy

Emax's car has more power than a north american e36 M3
(although he was not drafting in this case)

Jeff92se

iTrader: (82)

I remember when my bro had an old Fiat convert. We had the top down and were traveling at about 60mph. He decided to get right up behind a semi(ie..less than one car length) I stuck my hand up over the windshield and there was NO wind. I could hardly feel anything at all. My brother also mentioned that he had to get off the "gas" in order not to run into the back of the semi. This is an extreme case w/ the semi but it shows what's possible at only 60pmh or so.

Also I would think the faster you travel, the futher back you can be behind the front car in order for drafting to be effective. Also there are swimmers that "draft" behind each other to save energy. Again a different case(water vs air) but the speeds are only about 5 mph also.

«§»Craig B«§»

iTrader: (5)

just a note:
3rd gen SE Maxima has a drag coefficient of .32 (more aerodynamic than a Ferarri Testarossa - .33)

Frank Fontaine

There's one thing you gotta remember when you talk about this stuff. The drag is the frontal area times the cd. You can have a super low cd on a tractor trailer but the frontal area is so massive that the drag is still huge. The opposite is an airplane which has arelatively small frontal area--it resembles a pencil.

deezo

iTrader: (3)

Definitely. So when your close to redline (in the Maximas case), you're not able to accelerate as fast as you would from 60 to 70.

deezo

iTrader: (3)

I didn't want to throw airplanes into this because they are a different beast all together.

Dave B

Until someone posts a 14.0@100mph, I'm gonna say the M3 still has the upper hand. A US-spec M3 makes 205-210rwhp, which is more than a stock 2k2 Maxima 6 speed. The M3 lightweight went 13.7. M3 has no topend? My ***.

Dave

Dave B

If I remember correctly, water is a little more dense than air Apples to oranges.


Dave

Jeff92se

iTrader: (82)

Your ability to restate the obvious is legendary But then again, the swimmers are only going 2-3 mph.

MAX2000JP

I agree. Plus most of the times we have seen for the 2k2 Maxima are in Winter. I guarantee people will have a very hard time beating DMB's(or whoever has the record)time in the summer, when the ambient temperature is hot and humid.

Nismo87SE

I should know hehe. When I was driving my moms 90 DX civic I would draft newer civics and I4 accords and pull on them in 4th gear. I remember one time where I was racing a 92-95 civic DX too. He pulled a car on me from 1st to 3rd and had to get over into my lane. I estimate that when he got in front of me there was about 1/2 a car between us. Once in 4th gear I started to pull on him, it was funny to see his face when I flew right around him. We both stopped at around 100-105 on the speedo (which is really around 97-99mph). So from 80-100mph I basically regained 1.5cars then pulled another car on him once we let off. I did the samething to a 98+ I4 accord sedan, although there were 4 people in it. The car had rims, bodykit and exhaust, my mom's 90 civic is bone stock with 190k miles and 5spd. We started the roll on at 60mph where he slowly walked me by a car to 80, but I jumped right behind him to draft. Then I started to catch him and executed "The pass". I saw his jaw drop when he seen the DX on the back along with the rusty muffler. That time I went from 1.5 cars behind to 1.5 cars ahead. I drafted a prelude Si once in the SE-R which wasn't neccessary (I already pulled him in a previous run). But this time I left it in 4th gear at 60 got behind him and went around quickly. Also my ranger won't go over 100mph without drafting too

mzmtg

iTrader: (11)

Let me relate a little more personal experince with low speed drafting.

My father and I used to go bicycling together all the time. I was usually behind someewhat because he's in much better shape than I am. Anyway. When we would go down hill, he would get in a tuck position to minimize drag and maximize speed. I could get in right behind him, untucked, and still have to hit the brakes to keep from running into the back of him.

This was all at speeds less than 45mph. I would acutally feel myself accelerate when I got into his draft.

Drafting works. It's efficacy is proportional speed.

deezo

iTrader: (3)

Now if there was any such thing as "Power to Shape Ratio" for calculating minimum draft speeds, this would also be a good example. Bikes are not really aerodynoamic at all because of all the open space for air to get caught up into. I used to ride a lot and when I'd ride on windy days, it would kill me.

So, this proves that drafting speed is different for different vehicles because of its shape and ability to cut through the atmosphere.

OriginalMadMax

Nature is highly efficient at design and has had a lot longer to work on it than car companies. Look at birds - millions of years of evolution - pretty streamlined and efficient, and they migrate in those V patterns because drafting allows aerodynamic efficiency. They don't do any 100mph on those long flights, either.

dmbmaxima2k2

iTrader: (1)

ya i think it will be too. i just hope for a 14.0 on april 3rd and that i can hold the record for the best part of the season.

Chinkzilla

Drafting works in speed skating!

anyway, my disagreement on the hp vs. tq issue was in regards to the fact that hp and torque are really measurements of the same thing: The energy output of the car. Hp is work done, as in rpm/s/s, and tq is potential energy, as in how much kinetic force the engine is outputting. Both forces work on a car no matter WHAT speed your car is going. It's true, that tq has a greater correlation to acceleration, because it's job is to overcome inertia, and hp has a greater correlation to top speed because it's job is to...well.. move faster.

But this is where it all ties in, drag/resistance, are forces that work negatively vs. tq/hp. Obviously, the faster you are going, then the more drag is at work and the more your engine has to work. However, that also means that this equation does not start at a set number like 90mph. I think what ppl are saying is that it has no noticable effect till a certain speed. Race cars and street cars can not be compared in a direct fashion. This is because race cars have a MUCH lower coefficient of drag than street cars. Therefore the speed at which drag starts to have a "noticable" effect, which is subjective anyhow, is much higher for race cars. Possibly around 90 mph? For a street car it would be much lower. For a human? Even lower. Take for example speed skaters.

Reduce drag by drafting, and essentially your engine is "gaining" back horsepower. Sorta like your favorite mod Dave, the UDP. And hell, that's only 3-4 lbs reduction in rotational weight, and look how much that does.

Badaxxima

Rob's_AE- Efficiency and Performance go hand in hand, do something to increase an engine's efficiency (reduce parasitic losses, promote the combustion process in any way) and you improve it's performance. If you reduce the amount of throttle necessary to maintain 100mph, then you have that much throttle left once you hit 100mph, leaving the potential for more speed.

Deezo, Chinkzilla- You guys are confusing torque with low-end power. A car accelerates to match it's torque curve, when people talk about helping top-end power, they are actually referring to the torque curve at higher RPM. F=MA, Force = Mass X Acceleration. Torque is force (multiplied by a lever or numerical gear ratio); divide that my the mass of the car (weight divided by acceleration of gravity) and you get an object's rate of acceleration. Torque is NOT work. Yes it has the same units, but you can produce torque without doing any real work. You can try to loosen a bolt for hours, but if it doesn't move, you haven't done any work (force X distance applied). Acceleration is created ONLY by torque. Horsepower is a convoluted way of looking at torque. Torque is created every rotation. Horsepower at any RPM is torque X any given RPM / 5252. Horsepower is a measure of how often an engine can create torque. When you increase peak hp, you are actually boosting the top-end torque curve. If you don't believe me: Torque vs. HP

I drafted again on the way home yesterday from Indy to Louisville. I stayed within 2 cars at less than 100mph of a QX4 for 20miles, a minivan for 5 miles, a dually pickup for 8 miles and a black Expedition for 30 miles. I usually consume 5.5 gallons between Indy and Louisville. This time I only used 3 gallons. So kiss it.

Dave B

No way. All 2k2s run low 14s stock, regardless of weather j/k Yeah, wait until the weather warms up. The 2k2 guys are gonna realize how quickly those cast intake manifolds will heat up and kill thier power. I doubt we'll see any record come May.


Dave

dmbmaxima2k2

iTrader: (1)

that's why i bring lots of ice in a bag, they dont' get THAT hot compared to my 95 but they do get some heat. ICE ICE BABY.

OriginalMadMax

Another good reason to keep the car clean and waxed. Airlines calculate how much $$$ they save on their fuel budget by doing this to their planes.

deezo

iTrader: (3)

I'm not confusing anything. TQ gets the car moving and when the TQ starts to diminish, HP takes over.

Dave B

Ummmm....not really. Acceleration is related to torque. The longer the motor can sustain torque, the longer the motor will accelerate in each gear. These are crudely simple examples, but they do show that torque is what is truely responsible for acceleration (HP just a measurement determined from peak torque).

Examples:

Take a GM Vortec turbo diesel. It puts out 300hp and 520ft/lb tq. Big numbers, yes, but the torque starts out right off idle (1100rpms) and then falls off hard after 3300rpms. The HP curve peaks quickly and falls off fast by 3800rpms. What ends up happening is the truck accelerates hard right off the line, but quickly runs out of gear. Therefore the truck has very short powerbands which necessitates lots of shifting to stay in the power and ultimately no topend acceleration.

Now take the 4th gen Maxima. The curve torque stays relatively flat (within 10fwtq +/-) from 2000rpms all the way to 5800rpms. What this means in that the powerband is far more linear, useable, and lasts much longer than the diesel's.

By simply looking at the peak power (tq vs hp) you can roughly determine how the motor is going to accelerate (not factoring in vehicle weight and gearing). A car that posts 350hp/350tq (C5 Vette) means it has a extremely linear power delivery, flat torque, "power everywhere" and excellent topend performance. Now take a car that posts 240hp/280tq (Grand Prix GTP) means it is strong off the line and in the lower revs, but can't sustain strong acceleration up top. Finally take a car that posts 240hp and 130tq (Honda S2000) means this car is lethargic off the line, very weak in the low revs (no torque), but once the torque curve begins to rise then level out and the hp begins to build, the car accelerates very strongly and can run hard up top has long it can stay in the power band.


Dave