zzrpowerd-locost
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 posted on 5/12/05 at 01:32 PM |
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Bias for 4wd
On a 4w system what is best?
Equal front/rear drive
More front than rear
More rear than front
Just pening ideas for twin engine 4wd design  
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froggy
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| posted on 5/12/05 at 01:42 PM |
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thought about this myself the stumbling block is getting both motors to drive one transmission before drive is split front to rear otherwise
mechanically front and rear drive have no link and would swap ends without warning
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NS Dev
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| posted on 5/12/05 at 01:46 PM |
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I think (personally) that the ford/ff developments system, with 66/33 torque split (66% rear) is about spot on. Any more to the front and understeer
starts to set in with a vengeance.
Any track dayers on here will confirm that as they merrily drive round the outside of terminally understeering tyre slaughtering subaru imprezas!!
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MikeR
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| posted on 5/12/05 at 01:50 PM |
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of course - if you're not used to rear wheel drive, want to pootle aroudn the roads ..... more front wheel drive is what you're used to
and has less chance of swapping the ends on a wet roundabout.
(sorry, NS Dev just wanted to put the other side forward from someone who drives a fwd car  )
Depends what you want the car to do, what youre used to and where you'll be using it.
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Howlor
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| posted on 5/12/05 at 01:50 PM |
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Why not go for full 'bling' and have an active centre diff so you can control the split?!
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froggy
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| posted on 5/12/05 at 02:00 PM |
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yep im with nsdev on this one ,im hoping that the 60/30 split still let my car behave pretty much as a two wheel drive but give me more control in the
wet. after driving a customers westie in the rain which is an experience i dont want to repeat! im still not sure if by leaving the lsd in the front
diff on mine will cause it to understeer, no-one has offered an opinion yet
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Howlor
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| posted on 5/12/05 at 02:02 PM |
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Froggy, what type of LSD do you have in the front diff?
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froggy
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| posted on 5/12/05 at 02:08 PM |
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viscous its a 7" sierra same as my rear diff but with 3.15 gearsets, i think that il have to try it and see, its been done before but dax used a
6.5 open front diff on their quadra but my engine is a loooong way back ,my rear prop is 11" long and the gearstick is where the box meets the
bellhousing
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Howlor
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| posted on 5/12/05 at 02:10 PM |
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If you end up with too much under steer is it possible with a viscous unit just to use a different lube grade to give less/no LSD function?
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froggy
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| posted on 5/12/05 at 02:14 PM |
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cheers for that ,all a bit academic really as like a true petrolhaed ive started another project before finishing the last one
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NS Dev
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| posted on 5/12/05 at 02:45 PM |
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quote:
Originally posted by Howlor
If you end up with too much under steer is it possible with a viscous unit just to use a different lube grade to give less/no LSD function?
No, because the lube that you can get at is not the lsd fluid, that is contained within the lsd itself, not the outer casing.
The "fluid" is pretty trick stuff, totally unlike any oil you have come across! It is a fluid which solidifies under compression but
liquifies in tension. Make up a paste mix of cornflour and water and you'll get something similar, though I wouldn't try and use it in a
diff!!
You won't want an LSD on the front in any car used on tarmac. Useful on loose going but on tarmac you'll never need it.
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Howlor
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| posted on 5/12/05 at 02:50 PM |
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I'll try the cornflour and water later and report my findings. Very interesting you learn something new everyday especially on here!
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andyd
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| posted on 5/12/05 at 03:06 PM |
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quote:
Originally posted by NS Dev
Any track dayers on here will confirm that as they merrily drive round the outside of terminally understeering tyre slaughtering subaru imprezas!!
Surely that's the last place you'd want to be... around the outside! They'll run into you!
Andy
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JAG
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| posted on 5/12/05 at 03:15 PM |
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quote:
I'll try the cornflour and water later and report my findings
Proper Custard contains cornflour and behaves exactly the same.
I was watching a TV program called "Brainiacs" (one of the digital channels on freeview - can't remember which) were they do lots of
silly experiments.
They filled an outdoor swimming pool with custard and then the presenter walked across it and didn't sink
As soon as he stood still for a couple of seconds he began to sink. It took three people to pull him out because of the way the fluid behaves - a bit
like sinking sand. If you stay still you sink - if you struggle it holds and won't let go
These fluids are called non-Newtonian i.e they don't behave in the manner described by Newton.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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andkilde
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| posted on 5/12/05 at 03:22 PM |
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quote:
Originally posted by NS Dev
quote:
Originally posted by Howlor
If you end up with too much under steer is it possible with a viscous unit just to use a different lube grade to give less/no LSD function?
No, because the lube that you can get at is not the lsd fluid, that is contained within the lsd itself, not the outer casing.
The "fluid" is pretty trick stuff...
The fluid inside the LSD units is available -- industrially it is used in hydrostatic drives and Caterpillar sell a number of different grades. The
rally boys over here install fill plugs in the diffs and play with the different rheopectic oils.
Cheers, Ted
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andrew morrall
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| posted on 6/12/05 at 04:32 AM |
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CCC Twin BEC
CCC had an article on a twin engine BEC a couple of years ago. Can't remember the details of the setup.
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froggy
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| posted on 6/12/05 at 11:15 AM |
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i think they are a brilliant marketing exercise but they are all about straight line speed i followed a twin engined golf on a track day and it looked
about as stable as my reliant van on thity year old cross ply,s
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zzrpowerd-locost
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| posted on 6/12/05 at 12:08 PM |
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quote:
Originally posted by froggy
i think they are a brilliant marketing exercise but they are all about straight line speed i followed a twin engined golf on a track day and it looked
about as stable as my reliant van on thity year old cross ply,s
Thats cos they are 50/50 splipt on power!
BTW if anyone has seen a burgandy mk2 golf with 20v with turbo AND superchanger, spaceframed front end or a Black mk2 golf with rear mounted
supercharged VR6 on the show scene, I did and the Oil cooler and brake circuits on them Oh and supplied the silicon hose
Used to work for a hydraulic company, got all the motorsport jobs
[Edited on 6-12-05 by zzrpowerd-locost]
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zzrpowerd-locost
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| posted on 6/12/05 at 12:15 PM |
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20v super turbo
 
Rescued attachment swaprk1.jpg
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zzrpowerd-locost
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| posted on 6/12/05 at 12:16 PM |
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Supercharged VR6 mid mount
 
Rescued attachment swapvr1.jpg
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MikeRJ
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| posted on 6/12/05 at 01:57 PM |
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Surely the ideal split will depend a great deal on weight distribution and the kind of surface you are driving on?
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NS Dev
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| posted on 6/12/05 at 02:02 PM |
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exactly, which is why in the "ideal" world you want an adjustable torque split.
I know I can't afford that though, well, not in a package that will work in a locost anyway. The nearest compromise is the one that Harry
Ferguson/FFD came up with years ago and Ford have used since, the 70/30 or thereabouts split.
It's a compromise that works in most conditions. A touch understeery in really dry grippy conditions and a tad oversteery in really slippy going
but basically sound.........i.e. it works!
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NS Dev
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| posted on 6/12/05 at 02:04 PM |
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quote:
Originally posted by andyd
quote:
Originally posted by NS Dev
Any track dayers on here will confirm that as they merrily drive round the outside of terminally understeering tyre slaughtering subaru imprezas!!
Surely that's the last place you'd want to be... around the outside! They'll run into you!
Heh Heh!!! True, True, ok nip round the inside then, shouldn't be too tricky, you'd have plenty of time to make your mind up with
most of em!
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froggy
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| posted on 6/12/05 at 03:01 PM |
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there is an article in next months ppc about twin engined kits .to get back to original thread i thought that the idea was to use two bike engines one
driving the front one driving the rear, iirc volkswagen did something with a sirroco very early eighties. dont think it was a success though. twin
engined 4wd with torque split front to rear (deep pockets reqiured)
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NS Dev
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| posted on 6/12/05 at 03:13 PM |
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2 seperate engines driving opposing ends of a car is a nightmare. I would NEVER consider it.
It is an engineering BODGE of the very highest order. Great at the pub, and in a straight line, totally and utterly useless for anything else.
What I think would be interesting is a mid engined car with 2 bike engines either "piggyback" or side by side driving the rear wheels,
just as they use in class 10 autograss cars.
There are a lot of twin engined minis/mini pickups around in autograss and on the road. This setup but with some nice bodywork and 2 seats would be
good fun, and with weight over the driving wheels would actually grip and go quite nicely.
The transverse rear-mid engine setup is very quick in a straight line, but can be made to turn in nicely too. If you look at a lot of grasstrack cars
now (I know the setups are VERY different to tarmac but the principle of maintaining good wheel to "road" contact all the time is exactly
the same) they have the transverse engines mounted BEHIND the rear axle line!!
That is NOT the setup for tarmac....or driving with the steering wheels pointing the "right" way for that matter, but 50-50 ish weight
distribution is not tricky with the rear-mid engined setup.
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