Blairm
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| posted on 18/4/05 at 09:23 AM |
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Mid vs Rear
Hi Guys,
Greatings from Down Under
Being enjoying your part of the forum for a we while now. Just finishing off my standard seven type projet and thinking of the next.
Think a rear engine vehicle may well be worth consideration.
I have a hankering for a rear engined (north south layout) rather than a mid mount, but I am not sure if this is a sensible idea. A MR2 based car
would seem far easier and from the debates I have read, there will not be to much in it handling/perfomance wise. Any comments?
We did have Audi 100's over here (manuals where probably like hens teeth new, but now I may have to buy a lotto ticket) and kenedy Engineering
in the US seem to do adapters for many different motors.
A Lexus V8 would be Nice , but a Late modem toyota 3SGTE could produce all the horsepower I could ever cope with.
One big question I have not really got my head around from teh research to date is shifter for the Audi Transaxle? I am assuming it will be model 016
(again assuming I could source one).
Can any one point me to where I can get some info on this?
Cheers Blair
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stevebubs
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| posted on 18/4/05 at 09:52 AM |
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quote:
Originally posted by Blairm
Hi Guys,
Greatings from Down Under
Being enjoying your part of the forum for a we while now. Just finishing off my standard seven type projet and thinking of the next.
Think a rear engine vehicle may well be worth consideration.
I have a hankering for a rear engined (north south layout) rather than a mid mount, but I am not sure if this is a sensible idea. A MR2 based car
would seem far easier and from the debates I have read, there will not be to much in it handling/perfomance wise. Any comments?
We did have Audi 100's over here (manuals where probably like hens teeth new, but now I may have to buy a lotto ticket) and kenedy Engineering
in the US seem to do adapters for many different motors.
A Lexus V8 would be Nice , but a Late modem toyota 3SGTE could produce all the horsepower I could ever cope with.
One big question I have not really got my head around from teh research to date is shifter for the Audi Transaxle? I am assuming it will be model 016
(again assuming I could source one).
Can any one point me to where I can get some info on this?
Cheers Blair
Are you sure you mean rear-engined?
Rear engined means the engine is behind the rear axle, e.g. Porshe 911, Beetle.
Mid engined is between the axles, e.g. MR2, Elise
Orientation (N-S vs E-W) is irrelevant but E-W in a middie means the car wheelbase doesn't need to be as long
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Blairm
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| posted on 18/4/05 at 09:57 AM |
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Thanks,
Now I understand the difference. Seems its always a bit late at night when read these things. Maybe best think about such things earlier in the day
So I guess we are definitly talking about about a Mid engine car. But would I be better trying a transverse or Norh south.
Cheers Blair
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smart51
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| posted on 18/4/05 at 10:05 AM |
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transverse mid engines are most popular. You can take the engine, transmission and from axle from a FWD car and bolt it to the back of your
project.
longitudinal mid engine layouts are usually reserved for V12 engines, like ferraris, because they are too long to fit across the car.
Rear engines are a bad idea. It was a popular spectator sport in the '80s - to watch fat stock brokers drive their porsche 911s up trees on
tight urban corners. Once you lose the back of a rear engined car you really lose it.
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v8kid
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| posted on 18/4/05 at 10:51 AM |
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Blair,
It's easier to have a traverse engine mid layout 'cos there are loads of front drive engine/gearboxes available to install. There are
problems however in getting the center of gravity low enough - look on this forum for threads - there have been some ingenious proposals to overcome
these limitations.
My opinion, although others will hotly contest it, is that mid engine layout is only worthwhile if you are competition minded or you have a few
hundred horsepower to get on the road. A front engined car can be much smoother for the road, simpler to build and have as good or better handling.
Horses for cources.
Cheers
David
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kb58
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| posted on 18/4/05 at 04:15 PM |
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About the center of gravity, it all depends on what size wheels/tires you use. In my case I used 13" wheels for the Mini; there's
4.5" clearance below the pan. Perfect. There's nothing that could be done to lower the engine further, regardless of configuration.
OTOH if you use 18" wheels, yes a FWD setup will have either a higher CG or axles that aren't straight.
I politely disagree about front-engine car's having a smoother ride. With the engine right behind the driver, the increased sprung-to-unsprung
weight ratio at the rear will give a smoother ride, IMHO.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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turbo time
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| posted on 18/4/05 at 05:47 PM |
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In terms of weighing a North/South versus an East/West layout, 2 major concerns come to (my) mind.
Ignoring price, availability, etc. and just looking at the concept of each, I would lean towards a North/South layout for two reasons:
#1: IMO, it makes the whole process of designing/fabricating your rear suspension simpler, if only because the engine is not something that must be
designed around.
#2: Weight distribution. While it's absolutely possible to get 50/50 weight distribution with an East/West configuration, it certainly is
simpler to have the engine farther forward, and well inside the wheelbase of the car.
Now, like I said, I ignored pricing, availability, etc.. As it does seem that coming up with a North/South engine and gearbox combo generally costs
more (the kennedy adaptor plate, building the audi box to take the power, etc..)
Although one idea that I have always been a fan of was a turbo H-4 subaru powerplant, as it would sit nicely inside the wheelbase, and have that very
low CG. (Not to mention that boxer engines make me drool.)
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MazdaJim
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| posted on 18/4/05 at 06:18 PM |
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Just another thought to take into consideration:
In an East/West configuration you have more freedom of driver placement. The N/S layout forces you to place the seat(s) further forward unless you
use a short motor like the Subaru H-4 or 2-rotor Wankel. IIRC (no, I wasn't there) the pre-war Auto-Union V-16 grand-prix cars were very
difficult to drive; even Nuvolari had a hard time telling when the car was getting away from him, as he was sitting so far forward.
Yes, I realize most exotic cars these days have long numerously-cylindered N/S engines so I'm proabably talking out of my butt.
[Edited on 18/4/05 by MazdaJim]
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kb58
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| posted on 19/4/05 at 04:23 AM |
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I'm not upto date on the Subaru transaxle/engine layout. To use it in one of "our" cars, with it behind the seat, do you use the
engine and tranny as-is and cover the hole that would've had the driveshaft in it?
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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RallyHarry
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| posted on 19/4/05 at 12:24 PM |
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Yes, and the shifter is rod-linked and not cable ( at least the Impreza)
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kb58
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| posted on 19/4/05 at 01:58 PM |
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Huh, the rod linkage could either be a blessing or a curse depending exactly where it is...
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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imull
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| posted on 30/4/05 at 06:31 PM |
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Rear engined cars dont have to be dangerous. My 998cc rear engined car took the fight to Roger Clarks works escort on the Manx on its comp debut! It
is meant to handle like a dream in the lanes too (one day i will finish it ) More often than not the accidents are caused by aforementioned people
having more cash than ability...
Depending on budget and dimensions of car that you are thinking of, it might be worth looking into V6 lumps mated to a modern transaxle. QED in the UK
are now tuning the Rover KV6 to over 300bhp for around 7K and can easily be mated to a transaxle.
One of the nicest middy car I have ever seen had a Cossie V624V lump mated to a Hewland transaxle. THe guy reckoned it cost about 8K by the time he
had had it tuned and turbo'd
AFAIK, they also have licence to cast their own blocks etc so supply should not be too much of an issue.
[Edited on 30/4/05 by imull]
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