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Discussion Starter #1
is it true that the AWD system on the E's only kicks in when you are going slower than 30km? or so?

or does it kick in at whatever speed?
 

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The 4WD system is purely mechanical and has no speed sensor.

Operation is dependent on a difference in rotational speed between the front and back wheels.

Do a search for "Real Time 4WD" for the full explanation. It'd also on Honda's Element website.
 

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Discussion Starter #4
i thought so but i have heard people saying if your going faster than ___ than it will not work...
i am aware of of it works; just not if there was a speed sensor...
 

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Under what circumstances might the front wheels spin faster than the rear ones - when going 30 mph? A patch of ice? By the time the rear ones get power, wouldn't they also be on the ice (and the front beyond it)?

It is hard to imagine a full blown power shift, such as one you can produce while doing donuts in a snowy parking lot, while going 30 mph.

Small amounts of front wheel spin might produce a partial closure of the 4WD clutch pack, and a small amount of power to the rear wheels. I believe the new Elements have a added cam mechanism that reacts more quickly than the hydraulic one, and transmits something like 10% power to the rear wheels. If so, that is more likely to act at these faster speeds.

Why do you want to know?

In 6 years of ownership, I have never been in a situation where I thought the 4WD was acting while traveling at 30 mph or more.
 

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Discussion Starter #6
no its just that i am new to this whole thing.
i am used to 4x4 or awd being on always.. so if i am in slippery conditons and i stomp it or take a turn; all 4 wheels are working...
it makes me think.. do i want something that has a awd that kicks in once needed.... or get something with awd working always.
 

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What do you mean by 'awd working always'?

Yes there versions that send power to all the wheels all the time. Usually they have open differentials all around, so all wheels get the same torque. You do understand the difference between torque and power, don't you?

Honda has a version that can shift torque when the car is turning, I believe it can apply 15% to each of the front, and 70% to the outside rear.

Others have some sort of viscous clutch that tightens up when there is a big enough difference in speed between front and rear wheels, forcing them to turn at the same speed, rather than same torque.

The key point with the Element is that by default, all power is going to the front. The rear only get power if the front are spinning faster. It is easiest to detect this when driving on snow or ice at slow speeds. Whether it happens at higher speeds I don't know.

I don't think of the AWD as a means of giving me super handling at higher speeds. I drive as though it was a FWD, with the AWD (or RT4WD) as backup, in case I get stuck. If I hit slippery spots at 30mph, I'm not going to floor it or try fancy manuvers just to see if I can trigger rear power.

Keep in mind that if the rear wheels become the driving wheels, the car can flip, so to speak, into over steering mode. If the front tires are spinning due to loss of traction, then they also loose directional control. In an empty parking lot, you can have fun creating a RWD car like spin, or something approaching drifting. But you don't want to do that in traffic, or on a narrow mountain road.
 

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is it true that the AWD system on the E's only kicks in when you are going slower than 30km? or so? or does it kick in at whatever speed?
From the explanation at Honda's site and the reapir manual, the Element's AWD system is purely mechanical. All it responds to is a difference in rotational speed between the front and rear wheels, sensed by fluid pressure. There is no indication whether the pumps in the rear differentials are linear or non-linear, so it is possible that a different speed difference is needed at high speed to make it engage, but I suspect not.

It's not the same as the Accord "super" system that also responds to differences in rotational speeds between wheels on the same axle to feed more power to the outside wheel during a turn.
 

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what about driving with snow chains on?

so while driving in snow wouldn't putting snow chains on the front tires create a slight differential in size and therefore speed between the front and rear tires (making them spin slightly slower than the rear)? is the RT4WD system simply activated when it senses any differential in speed between the front and rear (slower or faster), or is it only activated when a front tire is spinning faster than the rear tires?

so is it possible then that the RT4WD system could stay continuously activated while driving in snow with chains on the front tires if indeed "All it responds to is a difference in rotational speed between the front and rear wheels..." (psschmied) and overheat the hydraulic system as has been mentioned in another thread ("Real" 4WD - #30)?
 

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RT4WD responds only to the front spinning faster than the rear. And at least one description mentions requiring at least a 2% difference. It also works in reverse - again, if the front wheels spin.

If the rear pump (driven by the center shaft of the rear differential) turns faster, the oil just flows through a bypass circuit, and doesn't activate the clutch. But it is hard to think of a situation in which the rear wheels could turn faster than the front ones.

Some writeups say it does not work when the brakes are applied. As best I can tell, that is just a consequence of the normal brake bias. Front brakes are applied harder than the rear ones. So when you stomp on the brakes, the front wheels normally slow down faster than the rear ones. If fact if it is slippery, and you don't have ABS, the front ones may lockup if you apply the brakes too hard. When you brake, it is hard to spin the front ones faster than the rear.
 

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so while driving in snow wouldn't putting snow chains on the front tires create a slight differential in size and therefore speed between the front and rear tires (making them spin slightly slower than the rear)?
That would be a moot point because you should never drive a vehicle with chains on the front tires only. You can put a single set on the back or you can put a set each on the front AND the back.

I think Honda recommends those cable chains only on an E and those don't make any appreciable difference in the tire diameter. For that matter, I don't think that link chains do either.
 

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Your owner's manual (at least my 2003 one) specifies front tires for 'chains'. And yes it does say cables, not chains, but the issue is clearance, not tire diameter.

With chains (generically speaking) the front tires will spin less, which means less activation of the AWD.

I haven't seen this in any Honda literature, but logically, if you need to put different size tires on an Element, put the smaller one(s) in the rear. Smaller diameter means higher rpms. Faster spin on the rear should not activate AWD. It might make a difference when using the smaller compact spare. But - Honda does not say anything about preferentially putting the spare on the rear.
 

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snow chains on front tires activating RT4WD system?

ok - i'm confused... my question regards putting snow chains on the front tires while driving on hard packed snow or ice and whether that would make the front tires seem 'bigger' to the Element's tire sensors and trigger the RT4WD system making the RT4WD be 'on' for as long as the snow chains are on (i.e. continuously) and perhaps overheating it... i'm getting contradictory statements from two apparently knowledgeable sources - paulj and EXwSCnose... :confused:

according to paulj the RT4WD will only be activated when the front wheels are spinning faster than the rear tires:

"RT4WD responds only to the front spinning faster than the rear. And at least one description mentions requiring at least a 2% difference." -paulj

but according to EXwSCnose (Chris) the RT4WD system will also activate when the front tires are spinning slower - as perhaps when snow chains are on:

"Any speed differential (V rotational) between the front and rear will want to engage the system. The shop manual describes a by-pass orfice so that accumulated minor differential amount is bled off and does not result in engagement. I would use chains only to get out of a mess and would not drive for any extended time with chains. If you have driven with chains you know that they track poorly, can damage your vehicle, are hard on the suspension...

There is no mention in the shop manual where the engagement threshold is, or for how long the 4WD condition remains after the engagement. (The chief mechanic at Honda World couldn't answer the question either.) From toiling around the desert very lightly I found the system to be engaging quickly (<10 degree of rotational wheel slip) and never felt the release....

The RT4WD stystem works on the 'double pump principle' where any speed differential will activate the clutch, and will want to drive the other output shaft at the same speed. The RT4WD vehicle cannot be towed with a wrecker for that reason, it needs to be flat-bedded." -EXwSCnose

perhaps one or more of our esteemed, and supremely knowedgeable immoderators - such as spdrcr5, MikeQBF, Sheniferous, T Mac, dancetiludrop, Genom, BigTzElement, ramblerdan and/or lizzurd - could chime in on this issue with their Elemental Wisdom...
 

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and how would you know if the RT4WD system was 'on' while driving 20 mph in 2nd gear with chains on the front tires in hard packed snow?
 

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I am relying mostly on memory from reading the HONDA dual pump document, which originally was posted on QuebecCRV. I have a pdf of it, and I believe someone (Ramblerdan?) still has it available on line.

That is quite clear that there is a bypass circuit when the rear pump is pumping faster.

As to engagement time, that document has a graph of a typical engagement period, produced by acceleration spin of the front wheels. The transfer of power is quite brief. Once you are moving, with front and both wheels spinning at the same rate, power to the rear quits.

This document is for the CRV from around 2002, so it does not include the cam feature on newer CRVs and Elements.

As to the towing case, my reasoning is that if the front are rolling on the ground, and the rear free to spin, they will spin via the RT4WD mechanism. If they were fixed (in the lifting cradle) there would tension in the system. If the rear are rolling, and front off the ground, RT4WD oil would take the bypass circuit, without activating the clutch. The consequences might not be bad, though the oil might still heatup.

Also, keep in mind that there is a thermal bypass, that prevents the clutch from engaging if the oil heats up. Some have reported that happening when playing on sand dunes or on long icy hill climbs. It may also account for the apparent non-engagement of the rear wheels when some people have gotten stuck in mud holes.

The bypass might also activate when towed in the wrong way. If I suspected my Element was towed the wrong way, a rear diff oil change would be first on my agenda.

There's also an 'over pressure' bypass. If the pressure difference between front and rear pumps is too high, this activates. Most likely this would happen if you let the rpms get really high while stuck.
 

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and how would you know if the RT4WD system was 'on' while driving 20 mph in 2nd gear with chains on the front tires in hard packed snow?
you don't know by any cue.

I think you are adding things to the vehicle which don't exist. There are no sensors which engage or disengage the awd system, its strictly hydrostatic psi, and temperature (for overheat). On normal dry pavement not accounting for turning corners or backing up, the system is running with equal psi both pumps are spinning the same speed. The piston which engages the clutch for the awd is not applying psi to it(its open). As either one of those pumps changes the psi that they deliver it allows the valve for the AWD to close there by allowing psi from the pumps to close the clutch for the AWD and locking it up. This will of course restore the pumps to the same speed and the system will open the valve and allow it to bleed off psi. 10 seconds has been mentioned in the past for checking the time frame for engagement so I would imagine it takes around that long to come out of awd once the equilibrium has been restored. Most AWD systems only remain in for a few seconds, hydraulic, electronic or friction. This is not to be confused with 4wd systems that lock all the axles in via a transfer case.
Also I use the term psi, it could equally just be flow in this case but that I am not sure of. Psi is required to close the clutch packs together, but psi(or resistance to flow) is a by product of hydraulics and is typically not wanted in excess in a system were you are normally just pumping in a circuit to prevent heat build up.

To answer your question about chains, no more then likely not as long as you are not spinning the front tires, which of course is bad with chains of any type. I am sure there is a practical speed at which the pumps don't function well enough to close the piston I would say below 2-3 MPH. However if you spin the tires at a stand still ala stuck in a snow bank, the AWD will engage and provide power to the rear tires as the front pump should have gained enough psi to close the packs up. chains don't increase your OD of the tire great enough to make a difference in speed front to rear. I would assume that you may get some engagement from the clunking that they do, but that is were the thermal switch would come in and bypass the system if the fluid gets too hot. If I were in that position my self I would put on chain sets on all fours, if only two I would go 1 front and 1 rear opposite the front and only far enough to get me out. This would mimic a spare tire allowing the differantials to spin freely. I think you need a vehicle with 4wd ability if you are planning on long term usage of chains.

Also this system will engage while backing up, and turning corners quickly or sharply.

does this help?
Chris
 

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paulj

I drive a tow truck,

The RT4WD system can be flat towed all four on the ground.

If you tow from the rear, rear wheels in the air, vehicle in neutral the system tends not to engage. Its not reccomended by the manufactuer so we don't.

If you tow from the front, front wheels in the air, vehicle in neutral the system will engage the but the front wheels are not coupled. That is an emergency short distance tow. I think the diff causes problems in the tranny.

If you tow from the front, front wheels in the air, vehicle in park as most FWD vehicles are towed, you will get about 6 feet. You could keep going and burn things up.

If I have time tonight I will double check for you, if you would like.

chris
 

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new RT4WD cam feature

Paul, thanks for the very detailed reply... it sounds like running chains in snow won't harm anything...

and so the new RT4WD cam feature is definitely on the new Elements (just 2009?) and not just the new CRVs? and does it just mainly activate the RT4WD quicker?
 
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