Honda Develops World
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Thai
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Interesting. The Honda system does not have a center differential (4runner has Torsen center diff).
Honda system: (from my understanding)
- It is mostly front-wheel drive bias...that is, most of the time, the front to rear torque ratio is 70:30. When accelerating, more torque is electronically transferred to rear (30:70).
- This concept is very similar to Acura MDX's AWD system...very similar!
- The real NEW technology here is the rear differential in electronically shifting torque left and right based on handling properties.
- Basically, the rear differential is like a limited-slip differential.
In cornering, the inside wheels spin faster than the outside wheels. At severe cornering g's, the inside wheel may lift off the ground and spin freely in the air. (Let's concentrate only on the rear wheels.) In a car with an OPEN differential (no traction control either), the inside wheel STEALS a lot of power from the engine because it's slipping or spinning in the air...torque goes to wheel with the least amount of resistance (aka slipping/spinning wheel). Thus, your car bogs down in corning (aka loses speed) because your engine power is being wasted by the spinning inside wheel.
(BTW, this one problem is why none of the Mercedes AMG cars are as effective as true-high-perf cars in cornering...they all have open differentials. Only new '05 models have all-speed traction control, which is inferior in action to a true LSD or Honda's system, especially in a sports car.)
A limited slip differential (LSD) is in sports car to prevent such a thing from happening. Torsen is the most famous rear diff LSD available (seen on Miatas, Lexus IS300, etc.). LSD, thru gearing, slows down the slipping/spinning inner wheel so that the outside wheel can get more power. More power to the outside wheel mean more tractive acceleration (remember the outside wheel is the one that is pressed against the pavement in cornering)...thus, more speed in exiting a corner. In addition, because the outside wheel is getting more power, you have enhanced steering feel (a feeling of neutral handling, instead of understeer) and cornering ability. Torsen LSD usually canNOT send 100% of torque to the outside wheel...probably only about 25-50%. So, Torsen has it's limitations.
The Honda system does a similar job...except that it's all electronic working on clutch-packs. So, in the event of cornering, the electronic brain will distribute power according to slippage and steering wheel angle (among other factors). I would assume that this is a faster-acting system and more accurate to the driver's intent. Because it's electronic, it does not suffer from Torsen's limited torque distribution...that is, Honda system can send 100% of torque to one rear wheel if needed. This would further enhance steering feel (neutral handling characteristics) and cornering power.
My BMW M3 has a M-variable LSD, which can send 100% of power to one rear wheel. The difference is that BMW system is based on hydraulics and clutch packs...no electronic brain.
The 4runner's system is different. Since handling prowess is not it's forte, i don't think you guys would miss anything. Anyway, in the 4runner, the spinning inside wheel would be slowed down by traction control if at low speed or VSC if at high speed. VSC does a similar job by counteracting understeer or oversteer...but it does so ONLY if you drift off course. Honda system is for sports cars and apparently works independent of stability control system.
Hope this explains things...and not confused anyone more!
Honda system: (from my understanding)
- It is mostly front-wheel drive bias...that is, most of the time, the front to rear torque ratio is 70:30. When accelerating, more torque is electronically transferred to rear (30:70).
- This concept is very similar to Acura MDX's AWD system...very similar!
- The real NEW technology here is the rear differential in electronically shifting torque left and right based on handling properties.
- Basically, the rear differential is like a limited-slip differential.
In cornering, the inside wheels spin faster than the outside wheels. At severe cornering g's, the inside wheel may lift off the ground and spin freely in the air. (Let's concentrate only on the rear wheels.) In a car with an OPEN differential (no traction control either), the inside wheel STEALS a lot of power from the engine because it's slipping or spinning in the air...torque goes to wheel with the least amount of resistance (aka slipping/spinning wheel). Thus, your car bogs down in corning (aka loses speed) because your engine power is being wasted by the spinning inside wheel.
(BTW, this one problem is why none of the Mercedes AMG cars are as effective as true-high-perf cars in cornering...they all have open differentials. Only new '05 models have all-speed traction control, which is inferior in action to a true LSD or Honda's system, especially in a sports car.)
A limited slip differential (LSD) is in sports car to prevent such a thing from happening. Torsen is the most famous rear diff LSD available (seen on Miatas, Lexus IS300, etc.). LSD, thru gearing, slows down the slipping/spinning inner wheel so that the outside wheel can get more power. More power to the outside wheel mean more tractive acceleration (remember the outside wheel is the one that is pressed against the pavement in cornering)...thus, more speed in exiting a corner. In addition, because the outside wheel is getting more power, you have enhanced steering feel (a feeling of neutral handling, instead of understeer) and cornering ability. Torsen LSD usually canNOT send 100% of torque to the outside wheel...probably only about 25-50%. So, Torsen has it's limitations.
The Honda system does a similar job...except that it's all electronic working on clutch-packs. So, in the event of cornering, the electronic brain will distribute power according to slippage and steering wheel angle (among other factors). I would assume that this is a faster-acting system and more accurate to the driver's intent. Because it's electronic, it does not suffer from Torsen's limited torque distribution...that is, Honda system can send 100% of torque to one rear wheel if needed. This would further enhance steering feel (neutral handling characteristics) and cornering power.
My BMW M3 has a M-variable LSD, which can send 100% of power to one rear wheel. The difference is that BMW system is based on hydraulics and clutch packs...no electronic brain.
The 4runner's system is different. Since handling prowess is not it's forte, i don't think you guys would miss anything. Anyway, in the 4runner, the spinning inside wheel would be slowed down by traction control if at low speed or VSC if at high speed. VSC does a similar job by counteracting understeer or oversteer...but it does so ONLY if you drift off course. Honda system is for sports cars and apparently works independent of stability control system.
Hope this explains things...and not confused anyone more!