20 replies to this topic

[Indigo]

Hi All, Is there a forum that focuses on rear engined Mini's?

I have a Twini, with problems with air flow around the rear engine.

The engine area pressurises and forces hot air into the cabin via small gaps in the engine cover, including up the C channels.

The boot lid is propped open, and I thought low pressure behind the car would suck the air out.  

Next is to remove the lir completely.

Any ideas or other forums out there?

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•  ReymondFeb09 010.jpg   57.97K   3 downloads

[Spider]

You might find some inspiration in one of the threads in here;-

 

https://www.theminif...ne-conversions/

 

 

The boot lid on the one's Copper built had big cut out and mesh fitted (sorry, I can't see you've done this);-

 

 

As well as big cut out's in the rear quarter with similar treatment.

 

[Lplus]

You might find some inspiration in one of the threads in here;-

 

https://www.theminif...ne-conversions/

 

 

The boot lid on the one's Copper built had big cut out and mesh fitted (sorry, I can't see you've done this);-

 

 

As well as big cut out's in the rear quarter with similar treatment.

That one also has the rear side windows replaced by perspex with air scoop intakes to the rear engine bay.

[sledgehammer]

Hi

 

Could you incorporate scoops into the rear arches ?

 

also a lot of the heat will be the exhaust / manifold

I wonder if ceramic coating / wrap would help  

is the gearbox underside open , I assume so ?

 

best of luck

[Ethel]

Z cars put lots of engines in the rear of Mini bodies.

 

No matter how low the pressure is behind the boot, it won't suck air out unless it can get in elsewhere.

 

 

How do you know it's pressurising? There'll be a fair amount of radiated heat & it looks like your cabin will collect much of it.

 

You could put together a simple U tube manometer, with some lengths of hose to sniff the areas of interest. There's likely some cheap RasPi or Arduino projects you could co-opt too.

[DeadSquare]

I think that you may be in the wrong part of the world.

 

Before Global Warming, there was a Scandinavian lady in the 60s, who had one with two 1100 engines that didn't work when the snow melted.

[stuart bowes]

No 1st hand experience myself but would it not be possible to have a sort of upside 'chimney' in the boot floor such that as you drive along, heat is sucked out from underneath? Or even with an electric fan for stationary times

Just thinking of ways that don't affect the visible styling.. if that's not a concern for you then as above. Most rear engine cars I've seen tend to have intakes either in the rear windows or rear quarters presumably for this very reason.

Personally I don't think I'd want big holes cut in the boot door but if that's what Cooper did and it makes the thing look 'original' I suppose it wouldn't be the end of the world

Edited by stuart bowes, 13 July 2024 - 11:36 AM.

[Indigo]

Thanks for the responses and ideas to my pressure / cooling issues in the rear engine compartment.

 

 Gauge.jpg   49.92K   0 downloads

 

Gave the manometer idea a go. Mounted one end on the dash and the other end in the rear engine compartment, by the clutch end of the rocker cover.

Couple of obviouse issues, level changed with the level of the car, and also as the speed / momentum of the car changed.

Found a quiet section of road and did a few repeat runs at low speed and then 90 kph.

The boot is held open about 40mm, and there is a large cutout behind the number plate flap.

Confirmed the compartment is pressurising at speed, fluid moves about 10mm on the gauge, so 20mm of water pressure.  This is subjective due to the above issues, but there was a consistent theame.

Did a few more runs with the boot lid removed.

Still gets pressure in there but no where near as much, and engine temp appears to be slightly less.

Now to modify the boot lid and hold it open about 200mm.  Test again and then maybe larger vents in the lower section of the boot lid.

[Ethel]

Runs in opposite directions and/or taking a reference reading with the car stopped at a good spot to take speed readings might help. It's never going to be NASA standard, but it's still useful if it shows what's better or worse. The most meaningful test point will be either side of the radiator core. You could  add a venturi to try & sense gas velocity, like a carburettor does.

[DeadSquare]

Ernie Unger tried very hard to run the engine in the Unipower GT with the standard radiator in the back, but never managed to keep the engine cool and had to retain the expensive front mounted radiator with twin electric fans.

 

As a Post Script:-  In almost stationary London Traffic with the engine mostly ticking over, my Unipower boiled unless I kept stopping the engine and revving it when I restarted, until I installed an additional electric water pump in the hose just before the radiator.

[Indigo]

Ernie Unger tried very hard to run the engine in the Unipower GT with the standard radiator in the back, but never managed to keep the engine cool and had to retain the expensive front mounted radiator with twin electric fans.

 

As a Post Script:-  In almost stationary London Traffic with the engine mostly ticking over, my Unipower boiled unless I kept stopping the engine and revving it when I restarted, until I installed an additional electric water pump in the hose just before the radiator.

 Just for my clarification, the electric pump is between the thermostat housing and top radiator inlet?  Primarily there to give you high water flow at idle?

[DeadSquare]

 

Ernie Unger tried very hard to run the engine in the Unipower GT with the standard radiator in the back, but never managed to keep the engine cool and had to retain the expensive front mounted radiator with twin electric fans.

 

As a Post Script:-  In almost stationary London Traffic with the engine mostly ticking over, my Unipower boiled unless I kept stopping the engine and revving it when I restarted, until I installed an additional electric water pump in the hose just before the radiator.

 Just for my clarification, the electric pump is between the thermostat housing and top radiator inlet?  Primarily there to give you high water flow at idle?

 

You are correct.

 

But. --- My radiator is cross-flow at the front of the car and the bore friction in six feet of 1 inch pipe there and 7 and half feet return was, I thought, too much for the Mini water pump.

 

The pump, mounted at the front of the car, came from a Washing-machine and the catalogue listed the electric motor as "Heater motor for Aston Martin".

 

For added clarification, if needed, there is no standard radiator or fan on my engine.

Edited by DeadSquare, 27 July 2024 - 05:05 PM.

[84 City E]

Just reading this thread out of interest, as i have little knowledge of rear or twin engined minis. Does lead me to a question though, what's the reason to do it?

 

I'm thinking the obvious of centre of mass is better and some folks prefer rear or even all wheel drive (if two engines)

but

Its obviously a lot of work, is it worth the extra work to have a little more grip/handling etc

 

I'm not getting at anyone or anything asking these questions, just curious

[stuart bowes]

I guess it's swings and roundabouts really isn't it, obviously it doubles your power, but then you have the added complications of tuning them both the same, working out some sort of gear change linkage and so on

 

from what I read, the AWD / lack of centre diff tended to work itself out simply by the fact that you'd just lose grip on one wheel / set of wheels until things were balanced out (although I can't recall if they were talking about tarmac or rally gravel stages ..)

 

obviously you also add a lot of weight though as well as power, presumably you lose the use of your back seats, cooling is an issue as per this thread, 

 

I'd love to have a go in one at least once just to see how it handles..

 

I seem to recall Cooper had issues with that himself when he had a serious crash off a roundabout somewhere near Guildford ?  Or am I remembering that wrong (or read it wrong anyway, was before my time..)

 

this is all just stuff i've heard or read though I don't have 1st hand experience

 

sometimes things are done just because you can, and why not lol

Edited by stuart bowes, 31 July 2024 - 02:01 PM.

[KTS]

Just reading this thread out of interest, as i have little knowledge of rear or twin engined minis. Does lead me to a question though, what's the reason to do it?

 

I'm thinking the obvious of centre of mass is better and some folks prefer rear or even all wheel drive (if two engines)

but

Its obviously a lot of work, is it worth the extra work to have a little more grip/handling etc

 

I'm not getting at anyone or anything asking these questions, just curious

 

i think the original concept came out of the development program of the moke

 

https://www.aronline...ini-beats-snow/