RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 10, 2012 21:26:52 GMT
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Are you set on using an inline engine for originality? An interesting idea me and a friend discussed a while ago would be the use of a Honda 4wd box and running gear on a non-Honda engine, to give the correct drive direction for a rear mounted engine. This with something like a Duratec V6 could make a nice set-up, but it would involve running the box backwards, so I'm not sure how the lubrication and thrust bearings would hold up, the Honda set-up is most likely biased to the front, so would become rear biased in this set-up. The trouble is it would put the engine in the rather non-original transverse layout.
Sounds like an interesting project, I'll be curious to see how this comes along.
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Oct 10, 2012 21:43:43 GMT
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Sierra 4x4 gearbox Front diff is very similar to the skyline jobbie posted up - bolted to one side of the sump, and driveshaft passes through the sump And the front/rear bias could possibly be sorted by rearranging the gears and bits inside the transfer case section
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You're like a crazy backyard genius!
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I'm not sure about the Sierra setup, but the GT-R centre diff has a variable torque bias front-to-rear, which is controlled electronically. In the GT-R, the factory computer varies it automatically, but you can get aftermarket controllers to set it at 50:50 or whatever ratio you desire. I couldn't say for sure how long a GT-R front diff will last if used in the rear at 50:50 torque split, but you are proposing to use it in a lighter car with less power, so that should certainly help.
As others have said, if you weren't trying to replicate the 6R4 layout, then RWD would be a lot easier and could probably handle the power of a naturally aspirated 3 litre V6 quite well. If you were willing to further compromise and use a transverse layout, then you could just throw in the complete engine and transaxle from any modern V6 front-wheel-drive car, be it a Mondeo, Vectra or whatever. That would save you a lot of money and driveline headaches, and the car would still be an absolute beast with that layout, it would be like a retro version of a Renaultsport Clio V6.
It will be exciting to see this project progress.
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froggy
Posted a lot
Posts: 1,099
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I've got a couple of v6 4x4 boxes that I won't be using and an adaptor plate that converts the v6 ford box to the Saab b234 turbo engine There was a 6r4 rep that used rx8 running gear then converted to Saab engine so it will fit in the front
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stealthstylz
Club Retro Rides Member
Posts: 14,855
Club RR Member Number: 174
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I keep looking at the suggestions wondering where you're planning on sitting. A full size RWD gearbox wont fit between the engine and the front seats, unless you run the tailshaft between the seats and the transfer box next to your legs. You'd probably be able to change gear using the standard shifter with the pattern drawn on backwards.
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Personally I'd go with a standard K Series engine and subframe at the front with a MGF subframe and matching K Series engine at the rear :-)
Paul H
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Oct 11, 2012 18:44:36 GMT
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I'm not going for a twin engine setup, i just don't like the idea of it... That and i used to work for an engine reconditioning company.. The K series engine was our bread and butter, awful engine.
As for where I'm going to sit, bear in mind the engine will be right at the back, the bulk of the gearbox will be behind the drivers seat and it will sit low in the frame, the transfer box location will be the biggest issue.
At this stage I need to get some parts and work out where it's all going to go, at absolute worst i reckon the engine will be a touch higher than i wanted it to be to accommodate the t box and rear diff, but we will see..
I'll post some pics when I get the bits and start putting it together, at this stage it's just a shell and a bodykit so nothing worth posting.
That pic of the skyline front diff helps..
As for the MT75 gearbox, I was planning to use one opriginally, but the thing that killed this idea was the drive to the front shaft, it's a chain driven transfer, I can't see it holding up when driving the rear diff, so I'd need a gearbox with the front and rear driven from the offset transfer... Then there are the issue's with the diff's being driven the wrong way for the cut of the gears, before taking direction into account..
There are 50:50 transfers available for the MT75 box but they're as rare as poor quality wobbly children's play pony poo
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 11, 2012 21:13:25 GMT
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I think the gearbox length might be a bit of an issue if you want the thing to go around corners. If you look at the original 6r4 set-up, the rear diff is actually rearward of the first cylinders, making the engine technically mid-mounted rather than rear, with the weight in a pretty sensible place, I fear to get a full length normal gearbox in there you're going to have to end up with your engine mounted half in the rear bumper, with all its weight hanging out the arse end of the car behind the axle.
This is a bit of a crazy idea, but what about mounting the box at the front of the car? Have the engine in the back, with the clutch, flywheel and bell-housing, and this driving an initial driveshaft going past your seat where space is tight, then mount the gearbox (minus its bell-housing) where it normally would be in a FR layout car next to your legs, with the transfer box and front diff under the bonnet, and then the rear driveshaft going back down the tunnel to the rear. OK it means you end up with a lot of driveshaft length, but the weight distribution and cockpit space would be much better, and you might even get-away with no front prop at all.
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Last Edit: Oct 11, 2012 21:14:43 GMT by RobinJI
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froggy
Posted a lot
Posts: 1,099
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Oct 11, 2012 21:52:19 GMT
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Mulled this one over with the lads at work today and we couldn't think of anything apart from evo running gear transverse mounted with a step down from the rear transfer which converts the rotation so you could run a rear diff at the front flipped over to run the correct way . A 230hp jag v6 with 25% loss through the 4wd doesn't sound like much of a performance car to me especially with the weight you will end up hauling round 1100 kg + I would have thought , sort of Sti /evo power to weight figures
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Last Edit: Oct 11, 2012 21:55:14 GMT by froggy
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 11, 2012 22:04:39 GMT
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I think we may have all missed a beautifully simple solution:
What gearbox has an a pair of 50:50 split outputs that are inline with the engines rotation, offset to one side enough to clear the sump/crank and as short/compact as possible?
Any FWD gearbox where the engine's originally transversely mounted.
I really can't think of a reason you cant just use a transverse V6 from any of countless FWD V6 cars, still on the original box, turn it 90deg so the engine's inline with the box in front of it, then use what was the left driveshaft to drive the front diff and the right driveshaft to drive the rear diff (unless you used a Honda engine/box). You'd have to flip both the front and rear diffs, but the box is the perfect layout, short, offset outputs to clear the bottom end, and 50:50 split, plus it'll probably come already attached to any of the many cheep donor engines.
Edit, OK, scrap that, I just thought of a rather large issue, the FWD box is outputting at the correct wheel speed, then you'd be putting the drive through a pair of diffs with a large reduction, so you'd end up with a much too slow wheel speed, curse word. Ah well, it would have been nice if it had worked! Anyone know of any 1:1 ratio diffs
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Last Edit: Oct 11, 2012 22:07:21 GMT by RobinJI
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Oct 11, 2012 22:45:13 GMT
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How about connecting the FWD box to a chain drive that counter effect the FWD diff ratio? From chain drive you could go straight to the front and rear diff. Similiar to this:
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Click picture for more
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Oct 11, 2012 22:46:21 GMT
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Yeah I thought of that a while ago until I realised that diff ratio's were generally somewhere between 4:1 and 3:1... As far as 230 bhp being far from a performance car goes, yeah you're right, BUT.... getting more power out of a jag v6 engine is going to be the easy bit of the project. For starters i'll be happy if I can make it work, then worry about tuning the engine.
I don't see how the gearbox will end up halfway out of the back bumper with a rear wheel drive gearbox and transfer box, the S type box is relatively short for a start, and the transfer box is a fairly compact unit, I can orient it as I want... they made a similar setup work in a real 6r4, so why wouldn't it work in a replica? The driveshafts to the remote transfer can be as long or as short as I want, I could even bolt the remote transfer directly to the back of the gearbox if I wanted to, rubber coupling between the two just in case of minute misalignment, It would probably only be a few inches longer than a real 6r4 box....
Another thing worth remembering is that it's a remote transfer box, I can fit it where I want, I can fut it near the front if that's the only place there's room for it...
Either that or mount the diff under the sump rather than to one side of it, then the driveshafts can run under the engine to the back diff, which would sit under the sump (Which would beed to be near enough flat) Yeah it'd be higher up that I wanted, but it's always an option..
I'll find a way to fit it all in, and eventually it'll end up making decent power, but i'm well aware of what decent power costs, it ends up being an expensive carry on, so I don't want to go down that route until everything else is in and working. My intention is to build a 'fast' engine when it's essentially finished from a spare engine.
I think i've sorted out in my head how i'm going to do this, just need a few paydays and some time to get things bought and get the project rolling....
It's always interesting to hear the different solutions people come up with for this kind of thing... !
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Oct 11, 2012 22:49:29 GMT
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ettorebugatti, that would create major weight distribution problems, not to mention the issue of finding a chain that can handle the power and torque, then the one off parts to make it all work....
I want to put the engine in the same place as the original, not so much for authenticity, more for the challenge of making it work... Some people think i'm nuts for that, I'm the kind of person who does things just because I want to, and this is one of those things.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 11, 2012 23:32:46 GMT
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A quick google suggests that the rear diffs from a Golf Syncro (mk2/3) have nearly a 1:1 ratio (20:21), so a pair of them and a normal FWD gearbox could potentially work. If they're not strong enough then the later haldex systems used in S3/TT's/R32s are ~1:1.5 ratio, so with a long (diesel?) gearbox could give a very usable ratio spread.
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stealthstylz
Club Retro Rides Member
Posts: 14,855
Club RR Member Number: 174
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Oct 12, 2012 17:52:51 GMT
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What about a Renault 21 or VW Passat gearbox? It'd make the car mid engined rather than rear and you might end up with the transfer case on show at the back but it'd probably handle a lot better. The 21 Quadra gearbox possibly has a flange on the tailshaft that could be adapted to mount the transfer box. Those Jag/Duratec engines are ridiculously heavy to say they're all ally, a lot heavier than a Rover V8.
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,715
Club RR Member Number: 34
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Oct 12, 2012 18:22:52 GMT
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i like robins idea best- normal engine and box mounted sideways with haldex diffs, gear ratios woudnt be far off and could be compensated with tyre size seeing as youve got huge box arches to fill anyway. plus much simpler, with no flipping gears and stuff that can only cause trouble. KISS.
id agree the engine choice really doesnt seem the best though. most transverse fwd 4 pots are better out of the box than the jag will ever be. vw 20vT, vauxhall redtop or even their v6, duratec, SR20, etc. etc. all come with huge tuning backup too.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 12, 2012 19:40:49 GMT
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Yeah, I think haldex diffs would be fine ratio wise, I've seen a few 6r4 replicas running 17" wheels with decent sized tyres, so the rolling radius would be around the same as most V6 powered donor cars, and given how long geared most modern cars are you'd probably want to reduce the gearing a bit anyway. Most quick moderns seem to be geared with 6th being capable of over 200mph, where as you're probably going to want to top out at around 140, if not less, so a 1.5:1 reduction would actually be about right.
If you're really worried about originality (which you seem to be) then you'll be wanting a quad-cam V6, preferably aluminium, in which case the Ford/Jag V6 seems a sensible choice really. Especially if you did use the layout I suggested, as an ST24 donor will be pretty cheap and come with a nice 6 speed box bolted up. They're clearly capable when tuned too, look at what Nobel have managed from them!
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Oct 14, 2012 12:47:53 GMT
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don't get me wrong i'm not trying to build a 6r4 copy, but I do want the engine in the right place or as near as possible and 4wd, I'm not worried about this idea being a bit of an over complication of what could be a relatively simple project, I just want to see if I can get it to work.
I'm sticking with the Jag engine idea at the moment, 4 pots are missing the poing completely, transverse mount is missing the point completely.
I don't want to go down the route of 1:1 diffs, i've looked into this before, the golf diffs just arent strong enough. A 1.5:1 diff woulf give a 33% speed reduction, which is quite significant....! But it is food for thought....
I'm still with the rear drive and transfer box idea, I think I can make it fit. worst comes to the worst it all won't fit and I'll have some parts to sell before a re-think, but should at least try.
I think the rear diff's going to have to sit next to the engine with the shaft running through the sump, not ideal I know but it kinda makes sense, means thee front shaft will also be offset but they were in the standard 6r4 anyway, so there must be a way to make it work.
As for the jag engine not being suitable, the AJ series are very strong engines, Noble twin turbo'd one and had it up to about 450bhp!
Does anyone know what the manual S-type rear diff ratios are? The auto's are 3.31, i'm thinking skyline diffs but they're 4.something... (4.36?)
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Oct 14, 2012 12:51:43 GMT
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Thinking about it.,... Robins idea with thee haldex system and diesel gearbox is actually not a bad shout... Are you sure they're 1.5:1???
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Oct 14, 2012 13:41:14 GMT
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27/17 iirc, but that's going off 'forum info' I think I'd want to check it out a bit more before spending any money, but it's definitely a possibility.
I think you might even be ok with a petrol box to be honest. Like I said, a lot of modern petrols use really long gearing for comfortable motorway cruising, especially v6 saloons, it's common for 200+mph geared speeds, while I expect you'd be absolutely fine with the ~125 a 1.5:1 reduction would give you, in fact if you want it to be quick then it'll help a lot to bring the ratios down to give a sensible geared top speed.
Like I say, it'd need some looking into a fair bit more, but I think in your shoes I'd definitely be investigating the idea.
I know with my mini when I decided on a Passat engine my first thought was 'I'll need a diesel box to correct for the small wheels', but when I actually looked into it the difference in intended use actually more than made up for it anyway, because even a petrol Passat's so long geared it'd give me more than enough high end for a track car.
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Last Edit: Oct 14, 2012 13:43:17 GMT by RobinJI
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