awd monster mini project

[sailerbill]

thanks for that pete
its all new stuff to me but i have a lot of faith in mick im sure we will adjust as we go

 

[mickvonmin]

i may be wrong but surely on such a gearbox/system the fd in the gearbox controls the roatation of all 3 drive shafts equally therefor the rear diff will always make the rears turn the same as the front no matter what the final drive ratio. I think this point is now moot anyway after i used the online gearing calculator and realised the gearing is pretty identical to the way its geared now in 2wd.

the general advice here seems to be dont do it, but the thing is, the question was how best should we go about it. i think we may have been made to think about a few different aspects of design that we hadn't thought about before so i'm ready to go, thanks for the help, updates i'm sure will be posted in due course.

 

[stevieturbo]

i may be wrong but surely on such a gearbox/system the fd in the gearbox controls the roatation of all 3 drive shafts equally therefor the rear diff will always make the rears turn the same as the front no matter what the final drive ratio. I think this point is now moot anyway after i used the online gearing calculator and realised the gearing is pretty identical to the way its geared now in 2wd.

the general advice here seems to be dont do it, but the thing is, the question was how best should we go about it. i think we may have been made to think about a few different aspects of design that we hadn't thought about before so i'm ready to go, thanks for the help, updates i'm sure will be posted in due course.

I'm afraid if that's your understanding of how a 4wd system works, maybe this vehicle should stay 2wd.

Front and rear diff ratios MUST match unless the centre diff does not use a 1:1 ratio.

As for overall gearing, I'd nearly be looking to see a final drive in the mid 3.x region, and no higher than 4.0.

I know I used a 3.1 in my mini with 13" wheels, and even with a straight cut set which had a tall 1st gear, and obviously 4th a 1:1, it could really have done with another gear. A shorter diff wouldnt have been practical as then 4th would have been useless offering no top end at all and even less traction in 1-3

Tall gearing is good when it comes to traction....and mine had very little below 100mph lol.

 

[mickvonmin]

centre diff? i think you may be the one who needs to research into this subject, that is awd rather than 4wd. the pinion turns the diff at the crown wheel, the diff directly turns the driveshafts and prop, say the prop turns 3 times faster than the drive shafts the rear diff will have to have a 1 to 3 ratio no matter what final drive is up front, and whats the final drive in an a series gearbox got to do with it when the individual gear ratios ie 1st to 4th will not be the same and the final drive is merely a multiplier of these ratios. come on stevie, stop hatin.

 

[mickvonmin]

MX5 is 4x100
Mini is 4x101.8 (4")

sorry bill the whole deal is off. lol

 

[PeteMoore]

Having read up briefly on the CRV system, it doesn't look like it is going to do what you want it to do.
Primarily a fwd system with a max bias of 50% to the rear wheels.
I don't think this would yeild the handling and grip results you are looking for. You are also still going to have to deal with both ends running open diffs, and with that in mind, absolutely zero improvement over the current setup. When she spins up, it will then bias to the rear slightly, but still allow the front with the shorter shaft or least grip to continue to spin.

They don't run a centre diff, just a viscous coupling off the crownwheel to drive the rears. I'm not sure what to suggest in terms of drivetrain which will allow a fulltime 4WD system that would permit you to bias to the rear as required.

I think early EVO stuff would be the most cost effective way, but you will no longer be running Honda power unless you make an adapter plate for the Honda engine to mate to the EVO box, however, you will then get the turbo, gearbox, transfer box, shafts, rear diff and the spares are plentiful and relatively cheap plus there is loads of room for upgrade as time goes by.

 

[Nigelo]

Flip, and I thought sticking the rear m3 subframe into my car was enough hassle.

If this project has been done before then id want to be in direct contact with whoever did it and have a long detailed convo.

Looking forward to updates!

 

[mickvonmin]

the rearr diff can be locked, dont as yet know how, and there is a frame available but is over a grand.
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i dont know how to embed

 

[PeteMoore]

I think early EVO stuff would be the most cost effective way, but you will no longer be running Honda power unless you make an adapter plate for the Honda engine to mate to the EVO box, however, you will then get the turbo, gearbox, transfer box, shafts, rear diff and the spares are plentiful and relatively cheap plus there is loads of room for upgrade as time goes by.

I'll pull my own post apart before some smartarse does.

The B-series with adapter plate won't work due to the counter-clockwise engine rotation, so scrap that idea.

Mick - I understand the rear diff can be locked, you could use blocks but essentially you may aswell weld it as it does the same job, unfortunately this will no doubt cause poor handling when power is sent to the rear.

As for getting it to run full time 4wd, im not sure what is required at the viscous coupling/diff/clutch affair to allow it to be giving a constant delivery of power as opposed to dipping in and out as front traction comes and goes. Although judging by your video, someone has managed it and seemingly done so quite well. Have you tried contacting those guys, or read up on the CRV running gear to see how you can adapt it to suit your needs.

EDIT: having read a bit more, it seems the multi-plate clutch that is engaged/disengaged to allow for 4wd is actually in the rear diff carrier,

For most of the time, only the HR-V’s front wheels are driven; it’s only when they begin to lose grip that the Dual Pump system starts to send power to the rear wheels. This is achieved by a hydraulic torque-split system, consisting of a conventional front-wheel drive arrangement, complete with transfer case, a propeller shaft running the length of the vehicle and a Dual Pump system integrated with the rear differential. This is the heart of the system and comprises two hydraulic pumps, one driven by the front wheels via the prop shaft, the other by the rear wheels via the rear differential.
During normal levels of grip the front and rear wheels, and their respective pumps, turn at the same speed; hydraulic pressure circulates between the two pumps, but no pressure is generated. If the front wheels begin to lose traction and start to spin faster than those at the rear, the two pumps turn at different rates; hydraulic pressure proportional to the difference in their speeds is generated, which in turn opens a valve body and activates a mechanical, multi-plate clutch.
This clutch then connects the front prop shaft to the rear diff, which feeds precisely the correct amount of torque to the rear wheels to re-establish overall traction. The more the front wheels slip, the greater the torque fed to the rear wheels.
The Dual Pump arrangement weighs less than a conventional four-wheel drive system and demands little maintenance – just a fluid change at 72,000 miles and thereafter every 36,000 miles. Further advantage of this design is that it automatically disengages under braking, thereby allowing the ABS to operate.

So logically, it should work exactly as you need it anyway, however, I would say with a little bodgery, you could remove the pumps and have the clutch permanently engaged, then your main weakness will be in the transfer case where the drive is sent to the rear.

I guess a good advatage to this is that you could run a second master cylinder off the hydraulic handbrake which disengages the rear clutch allowing you to properly upset the car prior to throwing the boot back into it for some 4 wheel smoke machine action

I am sure you have probably already read all that, but perhaps thinking on how to modify the clutches or the pumps to achieve your goal would be a good starting point if the HRV/CRV stuff is already purchased.

 

[stevieturbo]

centre diff? i think you may be the one who needs to research into this subject, that is awd rather than 4wd. the pinion turns the diff at the crown wheel, the diff directly turns the driveshafts and prop, say the prop turns 3 times faster than the drive shafts the rear diff will have to have a 1 to 3 ratio no matter what final drive is up front, and whats the final drive in an a series gearbox got to do with it when the individual gear ratios ie 1st to 4th will not be the same and the final drive is merely a multiplier of these ratios. come on stevie, stop hatin.

The final drive front and rear MUST match. You cannot ignore simple maths. If you do, you'll have each axle trying to turn different speeds which will completely **** everything up.

And in any 4wd system ( call it whatever you want, because "all" wheel drive is still 4wd, unless you dont have 4 wheels )

The centre diff in this case is in the rear diff housing. If you were to change the front final drive, suddenly the propshaft/front axle would be turning at a much different speed relative to the rear wheels, and in no time at all the centre diff would be destroyed.

If you think this is hating, work away. This is trying to give you advise. Ignore at your peril.

 

[stevieturbo]

Couple of useful threads

http://www.utahhondas.net/index.php/topic,1074.0.html

http://honda-tech.com/showthread.php?t=1708933

 

[stevieturbo]

And taken from links in the first thread

http://townhall-talk.edmunds.com/WebX?14@@.ef229e9/9

http://townhall-talk.edmunds.com/WebX?14@@.ef229e9/10

Worth reading the first thread too ( utahhondas ) about how the standard system works. It seems it's pretty bad in terms of handling as the centre diff takes a few seconds to lock up, so the car will behave as fwd for the most part, during any hard cornering until there is a difference in F/R axle speeds causing the viscous coupling to start to lock up engaging the 4wd properly and applying more drive to the rear. I'm sure it will still be an improvement over straight fwd under most circumstances though.

 

[Coog]

Not that it's any use, but an open centre diff can and will run different ratio's front to rear all day long. The CRV system doesn't look like it'll run different ratios well though as it's not truely 'open' unless you plan to modify it. I also don't think the CRV uses a viscous coupler.

 

[stevieturbo]

Not that it's any use, but an open centre diff can and will run different ratio's front to rear all day long. The CRV system doesn't look like it'll run different ratios well though as it's not truely 'open' unless you plan to modify it. I also don't think the CRV uses a viscous coupler.

The info anywhere Ive seen suggest it is basically a VC unit, although they can also apply hydraulic pressure to force a lock up. It is absolutely not an open diff, and F/R axle ratio's MUST match otherwise severe damage will occur.

 

[mickvonmin]

i havnt even looked underneath the crv but still, my understanding is that the driveshafts and propshaft will always turn at the same relative speeds (say 3 to 1 for arguments sake) no matter what the final drive is in the gearbox is as all 3 are turned directly by the rotation of the front diff (everytime the diff rotates once the prop will rotate thrice), the final drive is what determines the speed of rotation of this diff in relation to engine speed, it can not change the relative speeds of driveshafts to propshaft and this would be the only reason you would have to change the rear diff ratio. the rear diff will then turn the 3 prop rotations back into 1.

i knew that the rear diff was hydraulically operated but we were always going to just lock it somehow to avoid the lag between front slippage and rear engagement, 4wd rather than awd so i like the idea of a handbrake style operation for 4wd pete where it can be on or off, although in fantasy land 4wd with the option of rwd would be perfect, good work, what you think bill?

cant be arsed clicking on the links, i'd rather just open up the crv running gear and look at it, probably take about the same amount of time, plus, people talk *****.

 

[PeteMoore]

I'm loving the idea of disengaging the rear clutch to allow for some happy handle operation

If the system is hydraulically operated, then a simple restriction in the return line to the front pump could allow the system to do all the work you need without major rework and also allow it to operate as designed aswell. As for removing the fwd to allow for rwd operation, i honestly dont think thats possible due to the fact you are relying on a predominantly FWD box. a 50/50 split is about the best you can hope for.

As for final drives. You will have to use the standard CRV stuff, the final drive in the front (4.0:1 for example) will turn the front wheels once for every 4 input rotations from the box. The output to the prop will be 1:1 from the input, meaning the rear diff should also be 4.0:1. As such, the rear diff must match that of the front to prevent undue stress and wear.

Without going and hunting through the honda forums Im not sure this next idea would work. But if the box is running a normal B-series final drive and diff, then you could use a DC2 or EK9 LSD which will obviously allow for better turn in and control at the front, but you would want an LSD in the rear to allow you to power over the turn in and allow for controlled sliding, im not sure if one of these can be obtained, although Gripper LSD's seem to suit a massive range of diffs, so that could be your option for the rear end if needs be.

To begin with, i would stick with the standard CRV drivetrain and see how it turns out, then modify the pumps and hydraulic system after some testing to see if you can get it to act how you want. If not, then it would be time to tear it apart and modify to suit. Modifying the hydraulic system could be the best way of obtaining the permanent 4wd you are looking for

EDIT: Just read, you are able to weld the "real time unit" to provide a locked rwd system with the front shafts removed, as you will still have a permanent drive to the rear with the prop being driven from the crown wheel on the front diff. But she will still have an open diff, so no circles.

Apparently using anything other than Honda Dual Fluid II will result in the dual pump system failing in a very short space of time.

From what I can find it is a 5.06:1 FD in the CRV, you could run a 4.7:1 in the b-series box from MFactory which would then allow you to run an S2000 VLSD rear end, allowing more diff options at the back.

 

[mickvonmin]

the final drive is no longer an issue due to the gearing calculations and graphs i uploaded but i really do want to get to the bottom of the confusion over front and rear ratios, i think it wil require a diagram , thats bills expertise so i'll get him up to speed so that he can draw it up, a picture is worth 1000 words an-all. i'll give it 1 more go before bed. the diff turns the propshaft and driveshafts directly through it own rotation, say 3 to 1. the final drive rotates the diff at at ratio of engine speed. regardless of the actual final drive ratio, the front shafts will always turn 3 times slower than the prop meaning the rear diff will always have to be 3 to 1.
really hope i'm not digging a big hole here but my engineering techniques learned at queens tell me im right for a change.

 

[PeteMoore]

No your logic is right

But the prop directly links the crown wheel at the front, to the crown wheel at the rear. Those crown wheels need to have the same number of teeth and along with their pinion gears, provide the same ratio which is where I believe the confusion is coming from. If you remain on the standard CRV stuff then you won't have a problem with that, should you change to an LSD in the front for grip and decide to change to a different FD whilst you are there to assist in acceleration you will have to also change the rear crownwheel and pinion to match the front.

your 3:1 idea only takes those two items into account, the following should explain providing all 4 wheels are getting the same power

4:1 in the front 4:1 rear - all 4 turn the same speed
5:1 in the front 4:1 rear - front wheels will be accelerating quicker causing binding in the 4wd system
4:1 in the front 5:1 rear - rear wheels will be accelerating quicker causing binding in the 4wd system

the input (ie the 4) is the input to the diff from the main shaft of the box in the front diff and the input from the propshaft to the rear diff
the output (ie the 1) being the number of times the wheels turns after that power has been through the diff and turned 90 degrees

So I see what Stevie is trying to push you to acknowledge.

EDIT: Sorry, not trying to teach you to suck eggs, just dont fancy another 4 pages of arguements

 

[mickvonmin]

right, but it is not the fd crown wheel on the diff that powers the prop, a separate crown wheel on the diff turns the prop so if we change the fd crownwheel we dont touch this propshaft crownwheel.

 

[PeteMoore]

this is the rear diff

only one crownwheel - powered by the prop shaft via the realtime unit which is the series of clutches just below the awd part of the watermark

and you can see in this one, the prop is ran off the crownwheel via the transfer box on the back of the engine

 

[Paul RS]

Not up on this new-fangled selective 4wd shiznit, but the front section of the rear diff looks almost like a clutch to me? As in it'll either engage drive or it wont, there's no ratio change there?

right, but it is not the fd crown wheel on the diff that powers the prop, a separate crown wheel on the diff turns the prop so if we change the fd crownwheel we dont touch this propshaft crownwheel.

I'd imagine that if there is another 'CWP' it's going to be in the transfer case and not the rear diff. That's what you'd need to change if you plan to run different front/rear ratios.

 

[PeteMoore]

I'd imagine that if there is another 'CWP' it's going to be in the transfer case and not the rear diff. That's what you'd need to change if you plan to run different front/rear ratios.

2 CWP's - thats it - both shown in the pics above, both joined by a solid shaft, therefore they have to be the same ratio

 

[Paul RS]

So easiest route - Install Cosworth engine and use Sierra running gear

 

[mickvonmin]

the idea of optional 4wd would be dependant on what bill wants to do with it, cant see it being toggled while going round a corner or **** like that , just maybe 2wd for street driving and 4wd for the track or strip if we decide to weld the rear diff. and wont actually be on the handbrake lever ofcourse rather another lever and master cylinder.

my last word on changing rear diff ratio to match a change of final drive:
if we wanted to change the final drive, which we dont btw, we would be changing part number 3, its part number 1 that turns the prop, it is probably identical in size to the rear diff crownwheel as the cwp ratios have to be the same at either end of the prop, regardless of what final drive we have. over and out.

 

[Paul RS]

the idea of optional 4wd would be dependant on what bill wants to do with it, cant see it being toggled while going round a corner or **** like that , just maybe 2wd for street driving and 4wd for the track or strip if we decide to weld the rear diff. and wont actually be on the handbrake lever ofcourse rather another lever and master cylinder.

Why go to the bother of fitting 4wd if you aren't going to use it all the time?