The Triumph Dolomite Club - Discussion Forum

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PostPosted: Sat Jul 14, 2018 9:38 am 
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From cold, with the bonnet open, the front carb dashpot is cold (obviously), till engine warmed up
but as soon as the electric fan kicks in, the heat from the radiator is directed onto the
front dashpot, which starts to get warm, and this is with the bonnet open in a mild
temperature.

Leaving the engine idling for 5 minutes and it is still the same, closing the bonnet
results in front carb and rear carb and dashpot heating up, (5 mins, ran out of time).
This is a very interesting subject, that I have been following closely. The hot air from the radiator can't be hotter than the engine but if it is mixing with heat from the exhaust manifold within the engine bay then it could be. The actual under-bonnet air currents are a bit of an unknown so there could be some interesting air currents swirling around the exhaust and over to the carbs. I would insulate the manifold, with a good quality bandage or get it ceramic coated. I did wrap my old 1850 exhaust and it made a massive difference to the under bonnet temp and made it run better too.

Does the electric fan rotate in the same direction as the belt driven one? With the electric fan pulling through the rad, does it pull so that it swirls the air in an anti-clockwise direction (when viewed from front of car)- i.e. from exhaust over the cam cover to the carbs?

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PostPosted: Sat Jul 14, 2018 12:40 pm 
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Time for a bucket of dry ice and suitable lighting, take a video if you're going to do it. :)


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PostPosted: Sat Jul 14, 2018 12:49 pm 
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Quote:
Quote:
From cold, with the bonnet open, the front carb dashpot is cold (obviously), till engine warmed up
but as soon as the electric fan kicks in, the heat from the radiator is directed onto the
front dashpot, which starts to get warm, and this is with the bonnet open in a mild
temperature.

Leaving the engine idling for 5 minutes and it is still the same, closing the bonnet
results in front carb and rear carb and dashpot heating up, (5 mins, ran out of time).
This is a very interesting subject, that I have been following closely. The hot air from the radiator can't be hotter than the engine but if it is mixing with heat from the exhaust manifold within the engine bay then it could be. The actual under-bonnet air currents are a bit of an unknown so there could be some interesting air currents swirling around the exhaust and over to the carbs. I would insulate the manifold, with a good quality bandage or get it ceramic coated. I did wrap my old 1850 exhaust and it made a massive difference to the under bonnet temp and made it run better too.

Does the electric fan rotate in the same direction as the belt driven one? With the electric fan pulling through the rad, does it pull so that it swirls the air in an anti-clockwise direction (when viewed from front of car)- i.e. from exhaust over the cam cover to the carbs?
It is interesting how much heat is there, the fan rotates clockwise when standing in front of the car, and instantly heats up the front float as soon as it cuts in.

I will put the louvred bonnet on, but the way the fan is directing the flow with the bonnet open, I can only imagine 4x worse when shut.

Getting the manifold ceramic coated is something I am going to do, namely because the rusted look is annoying, just need to choose a colour :lol: :wink:
also need a manifold to send off, taking off the one on the car is not an option at the moment.

Also got the temp gauge to go down a bit by changing the coolant today, most likely a bad mix ratio.

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Construed as a public service, self preservation in reality.


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PostPosted: Sat Jul 14, 2018 12:52 pm 
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Quote:
Time for a bucket of dry ice and suitable lighting, take a video if you're going to do it. :)
Less messy to put a fog machine in, activated in the car, should clear the traffic and with a louvred bonnet a red arrow
style drive by :D

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PostPosted: Sat Jul 14, 2018 5:43 pm 
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Think about airflow when you are driving along. Air is forced through the radiator into the underbonnet area (assume bonnet closed) around the engine till it meets the brick wall which is the bulkhead. Now this gonna stop the air in its tracks and a better fan doesn't help much (although it will help ENGINE cooling by speeding flow through the radiator) So the only way this semi stalled air can go is DOWN and back through the tunnel and under the body. Since everybody KNOWS that hot air rises, the inevitable conclusion is that a pool of very hot air is going to collect at the top whilst the cooler (relatively) air escapes below as best it can. There is very little swirl pattern from a fan as every part of it is working the same and in any case, if you are moving, the air coming in the front will overpower fan created eddies.

Now add a set of louvres into the equation, the louvres allow some of the hottest and highest pressure air to escape upwards which helps with engine bay air throughput, is aerodynamically better for the car (less "brick wall" effect from the bulkhead) stops the pool of superheated air forming round the carbs which causes vaporisation and puts more air OVER the car rather than under it, which helps steering and straight line stability at speed. Now none of these effects are massive, but as the supermarket ad says, "Every little helps!"

Steve

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2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Sun Jul 15, 2018 5:22 am 
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Cheers Mart, Ive been thinking of getting some for ages now and with the heat we have at the mo it makes sense

Tony
Quote:
I actually found the link to the vents:-

http://www.body-kit.co.uk/product.php/1 ... 1109df1216

They were only about £16 each when I bought mine. I think I got mine off Ebay though iirc.

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PostPosted: Sun Jul 15, 2018 8:48 pm 
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Put the louvred bonnet on today.

From cold startup nothing, but as soon as the temp gets to quarter the passenger side louvre emits warm air from the exhaust manifold.

Once up to norm half temp the fan cuts in and the driver side louvre emits heat.

So they are working, however front float chamber still being heated by fan, also all else in the same line.


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On the motorway no one can hear me sing!
Construed as a public service, self preservation in reality.
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PostPosted: Sun Jul 15, 2018 9:48 pm 
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Those louvres are back to front! They have been fitted to work as intake, not exit!

Which will work when the car is stationary, but not when it's moving!

Plus, they need a bit more material removing from the vertical faces of the vents to increase flow!

Looking at the underside of the bonnet, there is room for another pair in the rear sections too!

Steve

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2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Mon Jul 16, 2018 8:30 am 
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Thanks Steve,

Been looking at the louvres since fitting the bonnet, and kept getting a feeling somethings not right, but carried on telling
myself I'm too picky.

Turning them around is no problem, as the paint has already come off the edges and they are silconed in.
Done one this morning, no probs.

Have to do something about the colour.

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On the motorway no one can hear me sing!
Construed as a public service, self preservation in reality.


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PostPosted: Mon Jul 16, 2018 9:15 am 
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A psychological imbalance :throb: but could be a carb cooling and efficiency gain:

Have the louvre on the carb side set up for inbound air flow and the exhaust side of the bonnet outbound air flow.

It would make me wince every time I looked at the bonnet though!

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PostPosted: Sat Sep 08, 2018 8:26 am 
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Not done much since I came back from holiday/suffering break.

The dolly batt had gone flat, rather than stick it on charge again, (it would charge, does everytime)
went for a new one, slightly wider, but a couple of mm narrower, with a bit more cold crank amperage,
and a range up.

One day I will replace the positive lead and tidy up the cabling.


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On the motorway no one can hear me sing!
Construed as a public service, self preservation in reality.
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PostPosted: Sun Oct 07, 2018 10:32 pm 
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RBRR completed !

And home now, time to :snooze:

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On the motorway no one can hear me sing!
Construed as a public service, self preservation in reality.


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