colimp66
|
| posted on 6/10/15 at 08:59 AM |
|
|
Bike engined Imp using MX-5 diff
Hi,
New to the forum and building a Hillman Imp with a bike engine in the rear like a standard Imp.
I have a MX-5 rear diff that I plant to turn upside down and then turn 180 degrees so it drives the wheels the proper way. The engine will sit in the
same position as the original Imp engine with the output shaft connected to the diff with a BMW propshaft donut.
Does anyone have any experience of these diffs and should I look out for any issues that could occur fitting the diff this way.
Any help or advise for this configuration will be appreciated.
Cheers
Col
[Edited on 6/10/15 by colimp66]
|
|
|
|
|
colimp66
|
| posted on 6/10/15 at 09:12 AM |
|
|
This is how the car is sitting at the moment with all the bodywork and welding more or less complete which was quite substantial. New inner and outer
sills, all four corners and wheel arches done inside and out among a load of other metalwork that was required. I have fibreglass doors, bonnet and
engine cover to be fitted and there will be polycarbonate windows to keep the weight down.
Cheers
Col.
|
|
|
40inches
|
| posted on 6/10/15 at 09:23 AM |
|
|
Imp Paul is doing something similar http://www.locostbuilders.co.uk/members/imp%20paul/
|
|
|
colimp66
|
| posted on 6/10/15 at 09:30 AM |
|
|
Cheers,
I have already taken quite an interest in that build and it is a bit further advanced than I am capable of with the spaceframe chassis that he is
building. Very impressive!!. 
Col.
|
|
|
britishtrident
|
| posted on 6/10/15 at 10:24 AM |
|
|
Few enough Imps left --- restore it properly with an Imp engine.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
steve m
|
| posted on 6/10/15 at 10:32 AM |
|
|
^^^^ +1
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
|
|
|
colimp66
|
| posted on 6/10/15 at 11:43 AM |
|
|
quote:
Originally posted by britishtrident
Few enough Imps left --- restore it properly with an Imp engine.
Yes, you are correct in saying that about how many Imps are left and I appreciate what you are saying.
I still have the standard Imp/gearbox all 39BHP of it in the shed and if I stumble across a few thousand pounds to get good power out of the standard
engine instead of going down the bike engine route it will be considered.
Before I start cutting the body about for the bike engine though I will have to see if what I have will work and will be making up a subframe for the
engine and diff first which I am in the process of doing at the moment.
That is why I have the initial post up was to ask opinions on the MX-5 diff for this application.
Cheers
Col.
|
|
|
T66
|
| posted on 6/10/15 at 01:24 PM |
|
|
Colin I had the engine dilemma a while back, kit car owners aren't fans of blackbird engines but auto grass guys used them extensively.
You make build choices with the facts & means you have at the time. And a blackbird engine is considerably easier on the pocket than a ZX10/12 , I
very nearly bought a complete spare recently for £200.
My engine lies across the chassis and drives via a Quiafe Powertec, this was more luck than planning as it was originally a Range Rover BW transfer
case taking the drive from a sprocket cup welded to a splined input shaft. However the box was fitted but then replaced with the Quaife , so while we
never saw it work, there's still nobody able to say it wouldn't of.
My engine is supercharged so the extra weight wasn't going to worry me that much, but yours in stock form the big weight of the RR box may be
too much for you too stomach.
We did plan to use a Quaife chain diff but then with only 9" between sprocket centres, it may of been less, the chain was going to be a pain in
the arse. If you have a look in my photos here, there might be something to help you out.
Do you intend mounting your engine across the chassis or parallel ?
[Edited on 6/10/15 by T66]
|
|
|
colimp66
|
| posted on 6/10/15 at 01:45 PM |
|
|
Cheers T66,
I have a good browse through your thread a good whilst ago(I should revisit it now) and I must say I was mighty impressed with the quality of the
build.
I don't want to use a chain drive and intend running the engine inline with the body so the gearbox output will bolt upto the diff through a
rubber drive donut to take the shock of the gear change away from the bike engine gearbox. Be near enough in the same position as a standard Imp motor
so parallel with the chassis rails as I don't want to take up the rear seat area space although it wil only have two seats. This is why the MX-5
diff will be rotated 180 degrees and turned upside down so the drive from the engine will move it forwards.
The weight of the car is an understandable concern. I do have fibreglass doors, bonnet, engine cover and will be running poly windows in it as well as
having the interior stripped to the bone.
I am guessing the weight will be under 700kgs possibly close to 650kg hopefully as a standard Imp is just over 700kgs from what I have read..
Cheers
Col.
|
|
|
T66
|
| posted on 6/10/15 at 02:05 PM |
|
|
Ns_dev on here built my chassis, and are very gifted builders - Nat & Cal.
Nat was very pro the Blackbird engine when mine came up for sale, and I am happy I listened. You have a lot more wheelbase than my Fiat so your plan
should be a runner, again this setup was discussed with Nat/Cal at the time, as they had seen it used before.
From memory I think it's the balance shafts that gets the oil starvation problem, mine are removed.
If there's anything I can pass on or help you with give me a shout, if I can remember whatever it is your welcome too it....
Ivan
[Edited on 6/10/15 by T66]
|
|
|
colimp66
|
| posted on 6/10/15 at 02:39 PM |
|
|
Cheers Ivan,
I appreciate the advice and encouragement.
Regarding the balance shafts that have been removed from your engine is there any downside to them being removed? Extra vibration etc?.
This has crossed my mind to do to my engine as after reading various posts regarding the Blackbird engine and the thought of these contributing to
engine failure I was assuming the best thing to do would be remove that element of possible failure as well as baffling the sump as a minimum
precaution.
Thoughts would be good.
Cheers
Col.
|
|
|
T66
|
| posted on 6/10/15 at 03:19 PM |
|
|
Col,
Mines not been running yet, but it had been previously and was good for 330bhp on the dyno. I don't know what work would be involved in
permanent removal of the balance shafts, there is a US drag bike forum I used for my research, if I can recall it I will let you have it.
Up to my tits in various things all which seem to overlap or be unable to finish due to many different reasons, but I'm progressing bit by
bit.
Andy Bates is very well read on Honda engines, and has a sump mod for the cbr1000. You might want to have a look at his website for sump ideas....
[Edited on 6/10/15 by T66]
|
|
|
Ugg10
|
| posted on 6/10/15 at 03:22 PM |
|
|
Have you looked into diff ratios and wheel sizes ?
The MX5 is a 4.1/4.4 ratio IIRC, typical bike engine kit cars try and run around a 3.1 diff if possible, remembering that the bike engine has a
reduction in primary drive before it gets to the main/rear sprocket (equivalent to the car diff) which shortens the actual ratio in the gearbox
effectively. The MX5 diff will give you mighty acceleration but will run into the rev limiter in top gear at around 100mph (quick guess but
calculators are about).
[Edited on 6/10/15 by Ugg10]
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
|
|
|
colimp66
|
| posted on 6/10/15 at 05:24 PM |
|
|
quote:
Originally posted by Ugg10
Have you looked into diff ratios and wheel sizes ?
The MX5 is a 4.1/4.4 ratio IIRC, typical bike engine kit cars try and run around a 3.1 diff if possible, remembering that the bike engine has a
reduction in primary drive before it gets to the main/rear sprocket (equivalent to the car diff) which shortens the actual ratio in the gearbox
effectively. The MX5 diff will give you mighty acceleration but will run into the rev limiter in top gear at around 100mph (quick guess but
calculators are about).
[Edited on 6/10/15 by Ugg10]
The answer to the question above is a no regarding the ratio of the diff, that's why I have posted on here to see if the guys like yourself can
give me advice on if the MX-5 diff is a good call or not to be using. Should I look for something used more widely for this application ke a Sierra
diff for instance as I would assume they are better serviced for changing the ratios if and when required. ??
Wheel size will be 185/60x13 possibly 205 if the gearing is way low for the 185 tyre. 100mph wil still be a far higher speed than an Imp but I
don't want it to be screaming its bits of at that speed on my private track of course.
Is there other ratios available for a MX-5 diff I guess is a good question or should I just get another diff before going further with this one?
Cheers
Col.
|
|
|
Ugg10
|
| posted on 6/10/15 at 05:42 PM |
|
|
Info on mx5 diff ratios here.http://www.miata.net/garage/KnowYourCar/S8_Gears.html
Some of the bike boys use freelander diffs which are 3.21 I think.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
|
|
|
colimp66
|
| posted on 6/10/15 at 05:58 PM |
|
|
Thank you.
I will check that out and appreciate the alternative idea of the Freelander diff.
Col.
|
|
|
blue2cv
|
| posted on 7/10/15 at 07:08 AM |
|
|
I have a westfield shallow sump on mine, pics in archive, also too many other things going on to progress grrr
|
|
|
colimp66
|
| posted on 7/10/15 at 11:17 AM |
|
|
Your 2CV so far looks interesting and a lot of work been done to get to the subframe chassis stage. That will surprise a few folk once it is done I am
sure.
Had a look at various sites last night regarding the MX-5 diff and it looks like it will be the 4.1 diff as only a few models vary from this and I am
pretty sure it isn't an Australian one I have. Anyway I would be good to have mad acceleration upto 100mph, realistically I doubt I would need
to go faster.
Took a photo of how the diff is at the moment after me giving a good going over with the grinder/cutting disc to remove some unwanted weight. The
metal sheet is me making up a template so I could weld up a subframe to bolt to the chassis.
Cheers
Col.
[Edited on 7/10/15 by colimp66]
|
|
|
Ugg10
|
| posted on 7/10/15 at 12:46 PM |
|
|
Just an example of the gearing effect for bikes
Using a 2001 929 RR Fireblade (popular bike engine for kits) as an example (max power at 11k) with 185/60/13 tyres (diam 552mm/21.9" ) (from
willthey fit.com)
Gears are -
primary 1.52
Gear, gearbox ratio, ratio taking into account the primary gearing
1st 2.69 4.09
2nd 1.93 2.94
3rd 1.60 2.43
4th 1.40 2.13
5th 1.29 1.96
6th 1.19 1.81
final 2.63
Using Subarugears.com (Ratios page)
max speed in gear at 11k is (diff ratio 4.1, [3.2], (2.63)) -
1st 43 [55] (67)
2nd 59 [76] (93)
3rd 72 [92] (112)
4th 82 [105] (128)
5th 89 [114] (139)
6th 97 [124] (151)
Cruise at 70mph in top is 8k [6.2k] (4.3k)
Hopefully this will give you an idea as to the effect and how it may limit what the car can be used for.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
|
|
|
russbost
|
| posted on 7/10/15 at 04:14 PM |
|
|
Interesting project, I would just add my two penn'orth re the gearing.
If you use the 4.1 diff that's going to be fine if you have no intention of doing any great mileage especially on motorways etc with the car,
acceleration will certainly be manic, particularly with the 13" wheels, but to a large extent I think you may find first gear almost
redundant!
I have my Furore (using the ZZR1400 engine) running on a chain drive, but the effective diff ratio is 3.28 (14 teeth to 46), but I'm also
running MUCH bigger wheels/tyres with approx 20% greater diameter. That gives me a cruise speed of around 70mph at 4750rpm, I reckon you're
going to be doing around 7,000rpm at 70mph, which is going to get VERY VERY wearing if you have any sizeable amount of miles to do on motorway or dual
carriageway - just something to bear in mind b4 committing to a diff ratio you can't easily change later
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
sam919
|
| posted on 7/10/15 at 10:09 PM |
|
|
Are we not missing the fact that in order to run it in the opposite direction, the CWP needs to go in reverse?
I'm not sure of any rear engine car that drives trough a transmission into a prop then a diff, 911/Beetles etc all have a gearbox and diff unit
together. You might be limiting your options with the layout of the engine vs diff suitability.
If you could build a transfer box with a two gears next to each other, the output shaft from the box running onto to the same size gear which would
then go onto the prop and diff you'd have reversed the drive to favour the diff rotation.
Two pinion gears could be used set on bearings in a solid frame, they would be strong enough.
|
|
|
blue2cv
|
| posted on 8/10/15 at 08:25 AM |
|
|
My chain drive diff is a Nova Racing one, billet casings, would you not be better going similar route
|
|
|
colimp66
|
| posted on 8/10/15 at 08:40 AM |
|
|
quote:
Originally posted by blue2cv
My chain drive diff is a Nova Racing one, billet casings, would you not be better going similar route
To use a chain drive diff I would have to put the engine midships and have it sitting where the rear seat would be originally. I am not keen on that
configuration and with using a standard diff there's one thing less to think about or go wrong. Putting the engine where the original used to be
will hopefully offer similar handling traits I am hoping of the original car.
Sam919.
There won't be much of a prop to be honest as the output shaft form the bike engine will be more or less bolted to the diff. Upside down and
turned 180 degrees to allow it to push the car forward in the normal manner. Trial tested on the bench.
With the diff being upside down I need to weld up the vent on the top of the diff as that is now at the bottom and make a new one, trans/diff oil will
be filled before fitting to the car.
Russbost
Good points and I am already looking at alternative ratios for a possible diff change.
Ugg10
Thank you for taking the time to look at the ratios and top speeds etc. Much appreciated
Cheers
Col.
[Edited on 8/10/15 by colimp66]
|
|
|
Ugg10
|
| posted on 8/10/15 at 10:40 AM |
|
|
Just a thought on the engine front - how about something like the Aprilia RSVR twin engine, pretty compact 140hp with decent torque, and dry sumped so
no problems with baffles and think about that vtwin sound -
Guess you have seen this - http://www.locostbuilders.co.uk/photos.php?action=gal&user=imp%20paul
ZX12 engine and what looks like a sierra diff.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
|
|
|
