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Old 1st January 2005, 02:35   #76
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...drag race depends alot on the launch, but it also depends on how much you know about your car. Every car has its own launching method. All you need to do is experiment with your car like in an deserted empty strip wid no stop lights n yea not cops aroundd...find the rpm range that your engine has the most power. drive with it n shift at different RPM's until you find it... after that its just all a matter of engine power AND shifting correctly... a bad shift can really screw you...Drag racing is definitely hard on your car, but to become consistent in your driving, you will have to sacrifice some hard-earned cash for tires..
its important dat u kno how to launch your car ...depends on the drive wheels (front-wheel-drive, rear-wheel drive or all-wheel-drive). ..mostly front wheel drivers for desi cars ..drive wheels make a big difference in the way your car launches. Most front-wheel-drive cars lose traction and spin the front wheels more easily because the sudden acceleration transfers weight off of the front wheels toward the rear...i used to launch using less throttle than you would with a rear-wheel-drive, to avoid excessive wheelspin, and then you gradually apply more throttle as you gain traction...front-driver with a limited-slip differential, like the Acura Integra reduces torque steer so you don't pull left or right under full throttle ..
After your now-perfect launch, just keep the steering wheel straight, shift just before the tach hits redline, and floor it after every shift....speed shifting worked best mi car .. simplest of all .. hit the clutch ..keep ur gas pedal down and shift up and release the clutch ... and make it fastt ..
another way is double clutching .. move stick from 5th gear to neutral
drop clutch in neutral thn rev engine from say like 2800 rpm [when u were in 5th gear] to 5800 rpm [exact rpm u kno u will be in while going 160 in 3rd gear]
press clutch in and shift into 3rd gear..double clutching is slower than conventional speed shifting, but allows for faster accleeration while retaining roughly the same speed... dont double shift twice in a row .. its gud for rolling highway drags , works gud for say a vtec engine though ..wid gud top end ..

my question is .. how does a slipstream feel ? i tailed gated at high speeds .. i never felt mi car suck up ...whn i passed or got close to the car i kno for sure it was just the cars power propelling me. wot speeds r we talking about to get a gud draft from the car in front of u in order to pass /..for a sport coupe ? and at what distance does one enter the slipstream ?
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Old 1st January 2005, 02:54   #77
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my question is .. how does a slipstream feel ?
I guess you'll have to hit serious speeds for that to happen. Works best when you're following a car that's as fast as your car.

Shan2nu
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Old 1st January 2005, 03:03   #78
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Originally Posted by Shan2nu
I guess you'll have to hit serious speeds for that to happen. Works best when you're following a car that's as fast as your car.

Shan2nu
i think i was tailing at 160 or 170 ks max ..
or maybe one can feel the speed gain whn ur engine cant push ur car faster on top end dats whn u save the gas n let the car in front pull u at the same speed n u lift a bit off the throttle to maintain the same speed till u find a passing oppurtunity and i come out the slipstream n speed away ..u may need to even downshift coz the engine speed will fall whn u r in the slipstream ..

ur back home early eh ? how was the new year bash ? i still have a while till it turns mid nite in atlantic time ..
cheers bro ..
ahppy new year ..
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Old 4th January 2005, 17:56   #79
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Shan2nu: "my question is .. how does a slipstream feel ? "

The answers to your question & a general comment on this thread :

Slipstreaming.
As somebody who's done this for years, slipstreaming is quite fun, though dangerous where I've done it - on the highways.

I've done it best behind trucks doing between 70-90 km/h - you follow up real close, say 5-8 ft from his rear end, match speeds, (drop down a gear or 2 if you like) & then when the time's right, simply shoot past.

The reason I say truck / bus, is because it displaces a large volume of air when it moves (drag). This drag creates a partial vaccuum behind the vehicle which sucks you in at 5 - 8 feet. You thus cruise behind the larger vehicle, pulled along in part by his engine & the vaccuum. Therefore, this can be done at lower speeds as opposed to the Formula / racing / passenger cars which have much lower coefficients of drag (Cd) & need a higher speed to create the vaccuum neccessary to drag another vehicle. One thing that's fun is that if you have a vehicle with lower torque / power output ahead of you, the driver will feel the effects of you hanging on his ass & piling on. It would also reduce his mileage & degrade his engine response whilst you're back there.

Rev-matched Gear Changes.
As somebody who drives nowadays because he has to (although have been on the wheel since I was 11), the advantages of rev-matched gear changes are many.

Picture this - After a long tiring days work, from Fort to Pali Hill, you're stuck in traffic more often than not. You change gears about 400 times from 1st to 2nd to neutral, with maybe a 3rd thrown in if you're lucky & 4th if it's your birthday You curse the traffic system & swear your next vehicle's gonna be an automatic. Out of khunnass, you kick your cluch more than you depress it. If you could have the advantages of a manual with a clutchless shifting, your left leg would not look like Maradonna's whilst your right leg remains like Bart Simpsons'.

This is why almost every major automobile manufacturer has marketed & sold a Tiptronic style transmission or is planning to do so. Now unless you can talk to Porshe AG to modify your 13 yr old Maruti 1000 transmission, I suggest you start rev-matching. This also works wonders for your image with your passengers, who ask the inevitable question : "boss, gaadi kharaab nahin hota". The correct & simple reply to this is "Nahin". If done correctly, you're doing yourself & your car a favour.

Gotta go now, more later.

Ciao!
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Old 4th January 2005, 18:14   #80
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Haha, behind a truck eh? I do that but, only if i wanna save fuel. LOL

On an expressway, where sudden braking is rare, you can try that, it'll enhance your FE by a lot. But make sure you choose a gear that will let the revvs drop to below 2500-3000 rpm.

Slipstream is worthwhile especially when you need to overtake a competitor who has a similar car with similar power and acceleration. I don't need slip stream to overtake a M800 but if i'm against another Vtec or a slightly faster car. i will need to use this to keep up or overtake.

Even in NASCAR, saving fuel is one off the reasons why a car uses another car's slipstream, doing so, he can travel that many more laps than the guy in front.

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Old 4th January 2005, 18:18   #81
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"boss, gaadi kharaab nahin hota".
haha, that reminds me. The other day i was taking my friend in my car. I was revvmatch when he suddenly looked at me and asked. Does you gearbox or clutch have a problem.

I asked him why he thought so. He said "Then why is it that you're missing gears very often". LOL

If you listen closely, it does sound like that, people standing outside (unaware of revvmatching) must be thinking "boy!! that car won't make it home with all that miss shifting"

Shan2nu

Last edited by Shan2nu : 4th January 2005 at 18:22.
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Old 6th January 2005, 14:37   #82
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Quote:
Originally Posted by Shan2nu
haha, that reminds me. The other day i was taking my friend in my car. I was revvmatch when he suddenly looked at me and asked. Does you gearbox or clutch have a problem.

I asked him why he thought so. He said "Then why is it that you're missing gears very often". LOL

If you listen closely, it does sound like that, people standing outside (unaware of revvmatching) must be thinking "boy!! that car won't make it home with all that miss shifting"

Shan2nu
I hate to break this to you, but IMO if you're rev-matching & there's any noise at all from your gearbox or any jerks to your drivetrain, you're not doing it correctly, & shall shortly end up with either your gear lever in your hand or your gearbox on the road!

We can meet-up sometime next week & I'll show you how I do it. Maybe you're right, maybe I am. Say Carter Road, eveningish if you're free at the time.

Ciao!
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Old 6th January 2005, 16:03   #83
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Therefore, this can be done at lower speeds as opposed to the Formula / racing / passenger cars which have much lower coefficients of drag (Cd) & need a higher speed to create the vaccuum neccessary to drag another vehicle.
Just to clear up something, a Formula car - i.e. an open wheel racer, has a HUGE amount of drag created, somewhere in the region of about 0.85 or so which is far more than a typical family sedan which would be around .29-.30

Quote:
One thing that's fun is that if you have a vehicle with lower torque / power output ahead of you, the driver will feel the effects of you hanging on his ass & piling on. It would also reduce his mileage & degrade his engine response whilst you're back there.
Thats a new one on me! Could you explain your reasoning for this? As far as my readings go, the lead car is not affected. It can't be! Once the air is past his car, it will not have any effect whatsoever on his vehicle.

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Haha, behind a truck eh? I do that but, only if i wanna save fuel. LOL

On an expressway, where sudden braking is rare, you can try that, it'll enhance your FE by a lot. But make sure you choose a gear that will let the revvs drop to below 2500-3000 rpm.
Thats probably the worst thing you can do on regular roads/highways. In a race, you can be sure that the guy in front is not gonna brake in a place you don't expect him too, but out on the open road, you neve know what the guy in front of you is gonna do. Being India, this is an even more acute problem where there is zero road sense in 99% of the drivers.

In order to get any advantage from slipstreaming, you have to be right on the tail of the lead car. Max. 1 foot away.! Doing that on our roads is a sure-fire way to an early grave as you will have no warning or time to react is the guy has to brake for a passing dog or a huge pothole suddenly!

Rt
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Old 6th January 2005, 17:26   #84
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Quote:
Originally Posted by rtech
Just to clear up something, a Formula car - i.e. an open wheel racer, has a HUGE amount of drag created, somewhere in the region of about 0.85 or so which is far more than a typical family sedan which would be around .29-.30

True. A typical family sedan's around 0.3 - 0.5, roughly half that of a Formula car. That's why I mentioned a truck / bus.


Quote:
Originally Posted by rtech
Thats a new one on me! Could you explain your reasoning for this? As far as my readings go, the lead car is not affected. It can't be! Once the air is past his car, it will not have any effect whatsoever on his vehicle.

I beg to differ. A higher rate of drag is created with someone immediately behind, as the car is pulling it's own weight as well as the partial weight of the vehicle behind due to the partial vaccuum.


Quote:
Originally Posted by rtech
Thats probably the worst thing you can do on regular roads/highways. In a race, you can be sure that the guy in front is not gonna brake in a place you don't expect him too, but out on the open road, you neve know what the guy in front of you is gonna do. Being India, this is an even more acute problem where there is zero road sense in 99% of the drivers.

In order to get any advantage from slipstreaming, you have to be right on the tail of the lead car. Max. 1 foot away.! Doing that on our roads is a sure-fire way to an early grave as you will have no warning or time to react is the guy has to brake for a passing dog or a huge pothole suddenly!

Which is why I said a truck - their rates of braking are much lower that those of a car, & combined by their higher coefficients of drag, slipstreaming can be achieved with a greater distance between the two vehicles & at a substantially lower speed than it would with two similar sized vehicles. It may also be arguably safer behind a truck due to these very reasons.

Ciao!
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Old 6th January 2005, 17:45   #85
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I beg to differ. A higher rate of drag is created with someone immediately behind, as the car is pulling it's own weight as well as the partial weight of the vehicle behind due to the partial vaccuum.
Hey elf, I think you are taking the term "pulling" a bit too literally. The car in front is not really "pulling" the other car along. It is essentially creating a hole in the air which reduces the force exerted on the 2nd car, which in turn allows the 2nd car to achieve a higher top speed. To explain it better than I ever could, read this:

This slipstream effect works in the following way. As a single car races around a track, it creates a "bubble" of high-density air in front of it and a bubble of low-density air behind. The difference in the pressure between these two air pockets creates drag, the force that impedes motion. This drag force limits the top speed the car can attain. But if a second car pulls up behind the first, the slipstreams created by the the two merge so that the first car losses its aft bubble and the second car loses its front bubble. This effect reduces the drag force each car experiences and both are able to travel slightly faster.

So you see, the car in cfront does not slow down, but also gains a bit from this, however nopt as much as what is gained by the 2nd car. Read
Quote:
this
http://www.aerospaceweb.org/question/aerodynamics/q0092.shtml


Quote:
Which is why I said a truck - their rates of braking are much lower that those of a car, & combined by their higher coefficients of drag, slipstreaming can be achieved with a greater distance between the two vehicles & at a substantially lower speed than it would with two similar sized vehicles. It may also be arguably safer behind a truck due to these very reasons.
If you think your reflexes are fast enough that you can take avoiding action while essentially driving blind behind a truck, god be with you! I don't know what else to say to your statement that it would be safer behind a truck!

Rt
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Old 6th January 2005, 19:04   #86
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I hate to break this to you, but IMO if you're rev-matching & there's any noise at all from your gearbox or any jerks to your drivetrain, you're not doing it correctly,
It's not from either. It's the blipping of the throttle that made him say so.

Quote:
I beg to differ. A higher rate of drag is created with someone immediately behind, as the car is pulling it's own weight as well as the partial weight of the vehicle behind due to the partial vaccuum.
Ah i dunno about that. i don't think the lead car is gonna be affected by this. Even if you don't have a car on your tail, there will still be vaccuum created behind you.

At 300+kmph an F1 car need not be right behind the lead car. He can be a few meters away and still feel no resistance.

Quote:
Which is why I said a truck - their rates of braking are much lower that those of a car, & combined by their higher coefficients of drag, slipstreaming can be achieved with a greater distance between the two vehicles & at a substantially lower speed than it would with two similar sized vehicles. It may also be arguably safer behind a truck due to these very reasons.
It's never safe to do it, even behind a truck. I was just giving a therotical example. But if you wanna test it on an open road, provided you've informed the truck driver, then yeah it'll do wonder for your FE.

But not something you should do on our roads.

Shan2nu

Last edited by Shan2nu : 6th January 2005 at 19:05.
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Old 6th January 2005, 21:39   #87
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Quote:
Originally Posted by rtech

This slipstream effect works in the following way. As a single car races around a track, it creates a "bubble" of high-density air in front of it and a bubble of low-density air behind. The difference in the pressure between these two air pockets creates drag, the force that impedes motion. This drag force limits the top speed the car can attain. But if a second car pulls up behind the first, the slipstreams created by the the two merge so that the first car losses its aft bubble and the second car loses its front bubble. This effect reduces the drag force each car experiences and both are able to travel slightly faster.

Rt
This looks more logical to me. For the front car, there will be a high pressure on the frontal surface, but it will have lesser vaccum behind due to following car. This becomes kind of better aerodynamic shape for front car (similar to aircraft wing). So, front car will be benefited. In following car, the frontal pressure will be lesser and hence it will also move faster. Both form together to become an aerodynamic entity dividing the drag force in between them.
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Old 6th January 2005, 21:59   #88
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I completely agree with all of Rtech's points.

Slipstreaming is only a useful concept on the racetrack.
On the roads, especially indian roads, you are asking for trouble, and if you try it on a truck you are more likely to be beheaded than anything else. (although i agree with the concept of the truack providing a lager "vaccum/slipstream".

Another thing to keep in mind is that when you are following a large vehicle at high speeds, you think you are enjoying the slipstream, but you are also getting less air to your engine, especially in terms of cooling, you will notice the temp guage go up a bit after a while.

cya
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Old 7th January 2005, 14:55   #89
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Another thing to keep in mind is that when you are following a large vehicle at high speeds, you think you are enjoying the slipstream, but you are also getting less air to your engine, especially in terms of cooling, you will notice the temp guage go up a bit after a while.
That's true if you're rpm is high. But if you're cruising at around 1500 rpm (which is stightly above your idling speed, the radiator fan should be sufficient to cool the engine off.

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Old 8th January 2005, 13:33   #90
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Too many points! Do you guys ever meet up in person, or is this the only mode of communication?

Am asking, coz would be nice to yakk about this face to face so all clarifications / issues can be resolved (if not globally, at least amongst us ).

Ciao!
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