Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Bonnet Slats

I have 29 top on each side and 8 indies on each side - according to my son who counted them for me.

...we believe you. Millions wouldn't

All mine are outies. My air intake takes air from the side lovre area and the tube from filter housing goes across and stops just short of the louvres. Under bonnet heat can rise a bit and I wonder if innies would force cooler air to the inlet tube?
The new roadsters seem to have this.
Mine is a 2002 plus 8 and you can feel warm air coming out of the louvres - top and side- when stopped after a run, even more so when the fan runs.I wonder if inserts could be put on the intake side louvres to convert them to innies and how effective they would be?

Conversion to innies? - has me thinking. The bonnets are symmetrical, and formed by rolling. If you have all outies, you could remove the bonnets, flip them over, roll them the other way, switch the catches from the (new) inside to the outside, and hey presto - now you have 29 top and 12 side louvres on each side, all innies.

Well yes you could, but it would be like wearing your jumper inside out, because the bonnets have a turnover edge.........

On the subject of innies, there's a clip somewhere on YouTube where someone has done airflow testing with those tassel things attached, and the sides of the bonnet is very turbulent air. The S1 Roadster apparently produces more power without the bonnet on that side, because it draws air through the innies, which restrict flow. Later Roadsters draw air from the cowl area, but the best place is the high pressure area in front of the screen, where the heater takes its air. So the last few louvres take air in at speed even though you would expect them to exhale.

That inside-out edge turnover could be covered with neoprene, Dave, perhaps?

The S1 roadster has an intake box sealed against the inside of onee bank of innies, doesn't it? For cars without intake boxes located there, what is the purpose of the side louvres at all? Indeed most of the side or top louvres would tend to let air out, reducing the pressure in the underbonnet area, and so reducing air flow into an airbox fitted there e.g. in the cowl above the rad. Perhaps the reduced louvres on my 4/4 are the better design after all...

...So I surmise that the louvres are a hangover from the days of inefficient radiator designs when passive cooling was the prime consideration, not optimal induction airflow for maximum power and efficiency as now. As such they have become a styling device, rather than being functional. Anyway the whole under-engine area is open to the air.

Hmmm............ a neoprene fix......

I think you're right and that it's primarily styling nowadays, although Plus 8's run hot and owners often space out the rear bonnet corners using those special extension kits. You need a few louvres at the back on top for heater air, but the remainder probably don't matter.

hmmm... now I found lots of 'innies' on the inside of my bonnet, should they be counted too?

Only if you drive with the bonnets open...