The Triumph Dolomite Club - Discussion Forum

Yes, it helps with cooling.

I must admit it doesn't go out in the rain much, but when I have been caught in a down pour there have been no problems.

sprint95m wrote: ↑Tue Jul 10, 2018 2:16 pm Is it a good idea to have water dripping from the louvres onto the engine?



Ian.

One of the reasons I have not fitted the other bonnet, especially as my car stands outdoors,
but I think a motorised sliding flap can be fitted.

Ps. Not worried too much about the water, more concerened with cleaning off water stains from
the polished inlet manifold

It won't be problem when driving as air pressure will force the water in the other direction. When stood still, it won't be a problem so long as you don't get louvres cut directly above the distributor!

You should not underestimate just how much air pressure accumulates under a bonnet. My first experience was a long time ago, but it left a massive impression which has stayed wth me to this day.

A mate had a Vitesse 2l MkI convertible with a ruck of Triumphtune goodies on it and a GRP front that persistently unlatched itself at speed! The rear edge of the unlatched bonnet would get lifted half way up the screen by air pressure underneath at 80mph though it never got any higher as pressure equalized. Now we (of course) fitted some bonnet pins to secure the front, but it was this malady that made me think of louvering the rear edge to let some of the pressure get out. And it really seemed to work! The car ran cooler, it seemed a tad quicker at v-max and slightly more stable at speed and it really did stop frost forming on the screen while you were driving on icy mornings (the Herald/Vitesse heater being generally about as much use as a chocolate teapot, this was welcome)

Steve

PS, Don't Tony Burd's louvres look the mutts nuts? Cooler than a polar bears dangly bits!

Probably a ridiculous not thought through idea but the Mini radiator just came into mind, more to the point louvres venting into the wheel arch as a more discreet method?

Galileo wrote: ↑Tue Jul 10, 2018 11:09 pm Probably a ridiculous not thought through idea but the Mini radiator just came into mind, more to the point louvres venting into the wheel arch as a more discreet method?

Lotta turbulence in a wheel arch, the air might not go where you want it to! I did think of cutting 2 large round holes in the flitches behind the front leg turrets then ducting air from there to some louvres in the wings behind the wheel arches. This WOULD work! I remember my old GT6II had louvres here and if you put your hand out the window at speed on a hot day it would almost take the skin off! But doing the bonnet, which is a large, flat, easily removed panel, just seemed a lot easier! Besides, why on earth would you want to HIDE your expensive and cool looking louvres?

To be fair, in a few weeks the weather will break and everyone will stop worrying about this - till next summer!

Steve

When it's really hot I have this fan in front of my car.

If it's fans and louvres I don't thonk many will beat this:

GTS290N wrote: ↑Wed Jul 11, 2018 10:21 pm If it's fans and louvres I don't thonk many will beat this:

I'm blown away by that

How much of the hot under bonnet temperature is due to heat from the exhaust manifold?




Ian.

Been doing some more checking this morning,

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).

Agreed the manifold on the other side does not help, but I do not remember this with
the viscous fan.

Will check again in a day or two, with a quick shield made up to be held under the float
chamber screw, wide enough to deflect the heat 'somewhere' rather than directly on.

Mahesh wrote: ↑Thu Jul 12, 2018 9:37 am Been doing some more checking this morning,

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).

Agreed the manifold on the other side does not help, but I do not remember this with
the viscous fan.

Will check again in a day or two, with a quick shield made up to be held under the float
chamber screw, wide enough to deflect the heat 'somewhere' rather than directly on.

So you have the evidence, once the bonnet is shut, it doesn't matter how good the fan is, the heat can't escape!

Try fitting your louvred bonnet and see just how much hot air escapes through the louvres when the fan is running! I'm betting it will be enough for a barbeque!

Theory says that after the first scalding blast when the fan cuts in, the air emerging from the louvres SHOULD actually cool down as you're increasing the throughput of cold air through the rad and engine bay by giving it somewhere to go (since hot air rises) This is why my preferred place for the louvres is as near the back of the engine bay as possible, ie the highest point, but a double set like Tony's can't hurt as then some hot air can also escape BEFORE it gets to the carbs! Also, the more louvres, the better the airflow!

Of course, if you go the EFi route, you will no longer NEED to worry about vaporisation, get saving, i'm itching to try the Jenvey kit!

Steve

[/quote]

So you have the evidence, once the bonnet is shut, it doesn't matter how good the fan is, the heat can't escape!

Try fitting your louvred bonnet and see just how much hot air escapes through the louvres when the fan is running! I'm betting it will be enough for a barbeque!

Theory says that after the first scalding blast when the fan cuts in, the air emerging from the louvres SHOULD actually cool down as you're increasing the throughput of cold air through the rad and engine bay by giving it somewhere to go (since hot air rises) This is why my preferred place for the louvres is as near the back of the engine bay as possible, ie the highest point, but a double set like Tony's can't hurt as then some hot air can also escape BEFORE it gets to the carbs! Also, the more louvres, the better the airflow!

Of course, if you go the EFi route, you will no longer NEED to worry about vaporisation, get saving, i'm itching to try the Jenvey kit!

Steve
[/quote]

Yep, the louvred bonnet will go on this weekend, (even though it is mimosa), the Jenvey kit has to wait till next year unfortunately and dependent on
getting a weber inlet manifold cheap enough, (which would have to be sent for polishing, can't go back to the dull look .

Tony's louvres are too nice.

Mahesh wrote: ↑Thu Jul 12, 2018 9:37 am 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?

Time for a bucket of dry ice and suitable lighting, take a video if you're going to do it.