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shcao Forums Junkie Location: Melbourne Registered: November 2002	Re: ae86 vs ae82??? Sat, 31 January 2004 01:37 Just browsing through the technical articles of none other than the toymods homepage, I found this excellent piece on different drive layouts written by bill Sherwood. I'm assuming that it is for low speed applications (as stock ae86s, ae82s, etc. are below 100 hp). So here it is. Thanks Bill. Bill Sherwood Generalised stuff FWD Drivetrain losses are about 17% - 22% at an educated guess. A rough weight distribution of 55/60% front to 45/40% rear. The complete car will weigh roughly 30kg - 40kg less than a RWD, and about 60kg - 80kg less than a 4WD. RWD Drivetrain losses are about 24% - 30% at an educated guess. A rough weigh distribution of about 48/53% front to 52/47% rear. 4WD Drivetrain losses are about 35% - 40% odd. A rough weight distribution of about 48/53% front to 52/47% rear, though this tend to be less important. Torque split front/rear is a significant factor in handling. Low power (up to 100hp) FWD Straight line This will be the fastest car as although it has the least traction out of the three it doesn't have enough power to really smoke the tyres badly. It'll also have the most power at the wheels as it has the least losses. Top speed Also the highest due to the least losses. Braking Not allowing for engine braking assist, FWD will be the worst due to the most forward weight distribution, thus reducing the braking ability of the rear wheels. Allowing for engine braking assist, it'll also be quite good and nearly as good as the 4WD. Stability Almost equal with 4WD due to the forward weight distribution. "Flight of the lead-tipped arrow" is the way to describe it, as the car that has the most weight up the front will have the pendulum effect to keep the car going straight. (big generalisation, I know, but it'll do for the moment) Cornering In theory the slowest, but in practice not a heck of a lot of difference between all the types. It's tough to describe without any diagrams but when a car - of any type of drive - is cornering on the limit then all four tyres will be slipping at about a 7° (roughly) angle to the road. This is a result of a thing called the 'traction circle', which I won't get into at the moment, but what it means is that in a stable situation with the car very near the limit of the tyres, if you add power in a FWD then the available lateral traction of the front tyres will be exceeded and so the car will start to understeer. The more power you add, regardless of the steering wheel angle, the more the car will understeer. This effect varies with the speed of the car naturally, with it being greatest at high speed. At very slow speeds the front tyres tend to dominate and still pull the front around anyway. It's also why the front end of a FWD tucks back in when you lift off the throttle. (as well as weight transfer with deceleration) And again this is a generalisation, not taking into account the modern clever active LSD's, suspension geometry, etc. They have a significant effect on the way a FWD behaves, and for example with the superb active LSD that the Honda Integra Type R has it can alter the torque of the left and right front wheels to give the outside wheel the most torque, hence the more power you use the more it goes to the most heavily loaded wheel, which of course has little chance of spinning and so cause understeer. Ease of set-up Probably not a great deal different to the other types, though to get the best it requires careful balance of the front and rear spring rates, and also F/R anti-roll bars. There can be a wide difference between wheel rates front to rear to get a good handling car. Effect of total weight The most affected of the three types, as it has the greatest effect of the weight on the front wheels. Lighter is always better. Cost By far the cheapest of the lot to produce, and this, along with the inherant stability of the low power FWD make it the main choice of manufacturers. If they want to make a 'sporty' version of the car, all they usually do is add some sort of LSD to the front (viscous, active, etc) and that generally tunes out most of the nasties from them. They also have the most room inside, which naturally the manufacturers and public like. RWD Straight line Second fastest of course, though about equal in the initial jump off the line with the 4WD. Top speed Second fastest again. Braking They have the most rearward weight distribution, so they will pull up the best as the weight transfers to the front under heavy braking. If the driver doesn't match engine revs when downchanging though, the rear will lose grip when the clutch is let out and so the rearward weight will work against the car making the corner facing in the right direction. Stability Worst of the three due to the majority of the mass being rearwards. (on some cars) A good driver actually turns this into an advantage, as it allows better control of the car when on the limit in corners, and also for direction changes between corners. Cornering Probably a little better than FWD due to the slip angle on the rears increasing at the limit when adding more power, thus making the car oversteer a little. In theory, a touch of oversteer is the fastest way through a corner but it may not always be the case in practice, as the cars (all types) that tend to oversteer also tend to have that amount of oversteer vary with speed. Ease of set-up A lot of variable again, but there is usually a wide variation that can be used quite successfully. The variation between front and rear wheel rates is usually a lot less than FWD, and perhaps much the same as 4WD's. This is one reason why RWD's also tend to wear down the front and rear tyres more evenly than a FWD. Effect of total weight Fairly insensitive, to a point. Lighter is always better. Cost Second most expensive to produce. Depending on the rear suspension, they may have a fair bit of boot space taken up (like the AE-86) to allow the diff housing the move around. There's also a tailshaft tunnel. 4WD Straight line The slowest of all due to the highest losses in the drivetrain. Maybe the fastest off the line because there's zero wheelspin, but this also infers that the engine tends to bog down. Good drivers can slip the clutch just the right amount to keep the engine spinning. (not good for the clutch though!) Top speed For obvious reasons, the slowest. Braking Roughly in between the FWD and RWD, but as it's darn near impossible to have all four wheels lock up if the clutch is let out at the wrong time it makes them quite safe and stable. Stability Again, when corning at the limit of the tyres if you add power the traction limit will be exceeded. In the 4WD's case though, they all tend to start to let go at the same time and so the car will tend to four wheel drift a little. However, it does depend on the torque split front/rear, but in most of the lower powered 4WD's they usually have a 50/50 split. For reasons that I'll explain later though, that tends to make the car understeer more ... Ease of set-up Probably tending to be more like the FWD in terms of difficulty, but with more like RWD rates, etc. Effect of total weight Quite insensitive. Lighter is always better. Cost Due to having components of FWD and RWD, they naturally tend to cost the most to make. Summary - low power Depending a lot on what you want the car for. Public FWD wins every time. Club work Whatever you prefer. I learned to drive in a RWD, and I find it very difficult to drive FWD's quickly. They can be driven very quickly indeed, but it does seem to require a touch more skill to do so. Left foot braking to stabilise the car and control the car is often needed. 4WD's tend to behave more like FWD's, and so you've come off a FWD then you'll be better off than a RWD driver. In motorkhana's, FWD's are very hard to beat indeed. Racing FWD or RWD, again take your pick as you have to trade off between power at the wheels and cornering power and braking ability. Since low power cars tend to do better with even a slight amount of extra power, FWD would seem to be best here. This is only the low HP section. Be sure to check out the rest of the article. Rock on. [Updated on: Sat, 31 January 2004 01:37] [Report message to a moderator]

	Subject	Poster	Date
	ae86 vs ae82???	SLY16V	Wed, 17 December 2003 13:36
	Re: ae86 vs ae82???	oldcorollas	Wed, 17 December 2003 14:12
	Re: ae86 vs ae82???	SXer	Thu, 18 December 2003 02:31
	Re: ae86 vs ae82???	Chris Davey	Thu, 18 December 2003 03:06
	Re: ae86 vs ae82???	SLY16V	Thu, 18 December 2003 06:29
	Re: ae86 vs ae82???	shcao	Thu, 18 December 2003 06:46
	Re: ae86 vs ae82???	SLY16V	Thu, 18 December 2003 06:57
	Re: ae86 vs ae82???	Classique71	Thu, 18 December 2003 07:33
	Re: ae86 vs ae82???	SLY16V	Thu, 18 December 2003 09:00
	Re: ae86 vs ae82???	Classique71	Thu, 18 December 2003 09:49
	Re: ae86 vs ae82???	Hirogen	Mon, 22 December 2003 02:11
	Re: ae86 vs ae82???	4AGE	Tue, 23 December 2003 08:48
	Re: ae86 vs ae82???	4AGE	Thu, 18 December 2003 10:26
	Re: ae86 vs ae82???	shcao	Thu, 18 December 2003 12:15
	Re: ae86 vs ae82???	DrExTc	Thu, 18 December 2003 13:49
	Re: ae86 vs ae82???	shinybluesteel	Thu, 18 December 2003 22:47
	Re: ae86 vs ae82???	DrExTc	Fri, 19 December 2003 15:55
	Re: ae86 vs ae82???	SLY16V	Fri, 19 December 2003 05:05
	Re: ae86 vs ae82???	shcao	Fri, 19 December 2003 06:17
	Re: ae86 vs ae82???	SLY16V	Fri, 19 December 2003 09:17
	Re: ae86 vs ae82???	furbypimp	Fri, 19 December 2003 13:14
	Re: ae86 vs ae82???	dimmy77_03	Sat, 20 December 2003 03:25
	Re: ae86 vs ae82???	DrExTc	Sat, 20 December 2003 03:27
	Re: ae86 vs ae82???	gianttomato	Sat, 20 December 2003 03:31
	Re: ae86 vs ae82???	DrExTc	Sat, 20 December 2003 14:36
	Re: ae86 vs ae82???	shcao	Sat, 20 December 2003 15:25
	Re: ae86 vs ae82???	CRAB-86	Sat, 20 December 2003 15:45
	Re: ae86 vs ae82???	SLY16V	Sat, 20 December 2003 09:39
	Re: ae86 vs ae82???	Ozzie	Sat, 20 December 2003 11:55
	Re: ae86 vs ae82???	SLY16V	Sat, 20 December 2003 12:28
	Re: ae86 vs ae82???	Shraka	Sat, 20 December 2003 16:38
	Re: ae86 vs ae82???	Sprinter-Saurus	Sat, 20 December 2003 23:08
	Re: ae86 vs ae82???	shcao	Sun, 21 December 2003 03:36
	Re: ae86 vs ae82???	Sprinter-Saurus	Tue, 23 December 2003 13:52
	Re: ae86 vs ae82???	SLY16V	Sun, 21 December 2003 05:28
	Re: ae86 vs ae82???	ae86drift	Sun, 21 December 2003 07:01
	Re: ae86 vs ae82???	Classique71	Sun, 21 December 2003 07:28
	Re: ae86 vs ae82???	ae86drift	Sun, 21 December 2003 12:49
	Re: ae86 vs ae82???	SLY16V	Sun, 21 December 2003 12:30
	Re: ae86 vs ae82???	shcao	Sun, 21 December 2003 12:47
	Re: ae86 vs ae82???	Classique71	Mon, 22 December 2003 01:48
	Re: ae86 vs ae82???	ae86drift	Mon, 22 December 2003 02:08
	Re: ae86 vs ae82???	SLY16V	Mon, 22 December 2003 08:34
	Re: ae86 vs ae82???	shcao	Mon, 22 December 2003 12:22
	Re: ae86 vs ae82???	shcao	Mon, 22 December 2003 12:23
	Re: ae86 vs ae82???	SLY16V	Mon, 22 December 2003 16:39
	Re: ae86 vs ae82???	SLY16V	Mon, 22 December 2003 16:44
	Re: ae86 vs ae82???	shcao	Tue, 23 December 2003 06:25
	Re: ae86 vs ae82???	SLY16V	Wed, 24 December 2003 06:38
	Re: ae86 vs ae82???	GZE-STYLE	Fri, 26 December 2003 05:22
	Re: ae86 vs ae82???	shcao	Sat, 31 January 2004 01:37
	Re: ae86 vs ae82???	rthy	Sat, 31 January 2004 11:35
	Re: ae86 vs ae82???	John K	Sun, 01 February 2004 00:59
	Re: ae86 vs ae82???	wraith	Sun, 01 February 2004 16:03
	Re: ae86 vs ae82???	SLY16V	Tue, 30 December 2003 02:12
	Re: ae86 vs ae82???	rthy	Fri, 30 January 2004 06:44
	Re: ae86 vs ae82???	shcao	Fri, 30 January 2004 07:17
	Re: ae86 vs ae82???	rthy	Fri, 30 January 2004 07:22
	Re: ae86 vs ae82???	sweetcheeks7284	Sat, 31 January 2004 00:39
	Re: ae86 vs ae82???	Apophis	Mon, 02 February 2004 02:18
	Re: ae86 vs ae82???	Johnny	Tue, 03 February 2004 02:02

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