LAT 79 bonnet - does it work?

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marinerblueuk
Posts: 45
Joined: Fri Jan 27, 2012 7:44 pm

LAT 79 bonnet - does it work?

Post by marinerblueuk » Fri Oct 26, 2012 4:13 pm

Although the LAT 79 bonnet looks good is there any evidence that it helps keep the engine bay any cooler? Do the vents at the rear of the bonnet allow heat to escape? Does it only work at speed or does it allow heat to escape once you've stopped?
I'd be interested to know if anyone has noticed any difference after fitting one.

Tomaselli
Posts: 942
Joined: Fri Sep 30, 2005 2:03 pm
Location: Cheshire, North West England

Post by Tomaselli » Fri Oct 26, 2012 10:02 pm

It does, but it shouldn't be your first choice for cooling the engine bay in a Tiger. Factory stock cars (I know not that many left) are able to maintain their cool.

I'd start with looking at your existing cooling, perhaps at the usual prime suspect; radiator. Have it re-cored with modern internals?

On my stock Tiger, I pull the bonnet open whilst on the run allowing for a gap between bonnet and body, and this certainly helps cooling, and yes you are right the air efficiency in the engine bay is only when you are on the move, I'm lucky as a gentle pull on the bonnet open latch allows for the bonnet to prise open without fully opening, so I can travel at speed getting fresh air in the engine bay without the bonnet lifting at speeds.

I am over the winter arranging for my rad to be recored which hopefully will cure my overheating issues which have appeared the last couple of years, I think there is sludge in the fins of the radiator - am still running the original block. There must be 50 years of rust in them waterjackets :roll: I'll also be fitting a filter in the top hose when I am done to capture any rubbish before it goes in the new rad.

LAT 79 bonnets are readily availble as reproduction, but are plastic :shock:

Finally, in answering your Q, yes the LAT bonnet did make a noticeable after I fitted one, the difference being as as you are allowing more airflow at speed.

Tomaselli
Posts: 942
Joined: Fri Sep 30, 2005 2:03 pm
Location: Cheshire, North West England

Post by Tomaselli » Fri Oct 26, 2012 10:04 pm

Needless to say, there are lots of other issues with keeping a cat cool not just radiator and airflow :D

garyv8tiger
Posts: 650
Joined: Sun Dec 30, 2007 10:57 am

Post by garyv8tiger » Sat Oct 27, 2012 8:06 pm

and all this from the man who has 2 tigers that overheat :mrgreen:

something worth mentioning the alloy rads from the specialists are not as good as there made out to be there ok but there are much better available .i have a recored stock one that is more efficent .

marinerblueuk
Posts: 45
Joined: Fri Jan 27, 2012 7:44 pm

Post by marinerblueuk » Mon Oct 29, 2012 10:49 am

Thanks for the information. My Tiger doesn't overheat when moving and so far just about copes with sitting idling after a run with the electric fan but the engine bay does seem to get incredibly hot (do the tubular headers produce more heat than the original cast iron manifolds?) and I can sometimes hear coolant bubbling after I've stopped (afterboil?).
I guess that fitting an electric water pump that could keep water circulating would be a solution but I thought that if you can get more hot air out in the first place that would be better

B9471845
Posts: 125
Joined: Fri Sep 30, 2005 11:32 am

Post by B9471845 » Mon Oct 29, 2012 7:09 pm

I raced my car for a while with a steel bonnet remodelled with the scoop and vents, think that is the LAT79 one?

Proof of its cooling efficiency was the fact that the vents were too hot to touch after a race. The rest of the bonnet would be merely warm. I still have it if someone wants to buy it.

My car is now FIA standard which doesn't allow the LAT bonnetstyle so I have a standard item permanently propped up, with the air gap at the back filled with foam. Now the tops of the wings are hot after a race instead.

Popping the bonnet open above ~30mph is counter-productive, the high pressure region in front of the windscreen forces air into the engine bay, reducing flow through the radiator. This method only works in traffic.

Try taping lengths of string to the rear of your propped-up bonnet and accelerate.

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