Yes Or No? To Cutting Out The 'fake' Moulded Vents On Bonnet?

[Onliest Smeg David]

OK then...

What does the collective think about cutting out vents where the pre shaped ones are on top of a Westie bonnet?

My cars got a 1.8 Zetec, and I've not noticed any overheating issues or difficulty starting when engine hot.

[greenandmean]

Don't bother, they look sh1te. :no: Look like what they are cuts in fibreglass not at all appealling like louvres in an alloy bonnet. :down:

[Bananaman]

I'd look at your cooling system if i were you!!!

[Mid life crisis]

IMHO as your car draws air from under an enclosed bonnet, any dissipation of heat can't do any harm.

Worked for me on my car

If you click the link to the Speed Series and have a look at Stu's championship winning car, well you decide

[Cleggy the Spyder Man]

if you have not noticed any overheating issues why do you want to do it?

I have a stonking great hole in the top od my bonnet - good for watching heat haze

No reason why not to cut them out TBH if you fancy something to while away the hours - just make sure you round off the edges or you will be inviting Mr CrazyCrack around to visit

[pistonbroke]

I think they were added initially to give some rigidity to the bonnet as its pretty lightly made , This helps stop it vibrating and hence fatigue of the fiberglass which could develop stress cracks over time

iyswim

[Norman Verona]

I found, by testing with coloured smoke, that over 60 mph the louvres on a Caterham bonnet stopped emitting heat as the air pressure on the bonnet was greater than the under bonnet pressure.

If this is correct and the only exit for air under the bonnet is down the transmission tunnel (the same pressure situation appears to be true underneath) then we have a so much pressure under the bonnet the air is building up in front of the rad and the throughput of air is restricted to the speed of exit down the tunnel - not a lot.

I have raised the rear lip of my bonnet to create a NACA duct. It appeared to work well but after a serious overheating in a traffic jam I cut a big hole over the carbs. I think the end result is to destroy the suction effect from the duct and not get any heat out of the new hole over 60 mph.

I have been toying with the idea of covering the bottom of the engine and creating a duct by the bell housing.

However in the current weather it's going to be a waste of time!

[SteveD]

i would look at the real reasons you are having issues , cutting hole sin your bonnet will not cure the problem

at the end of the day there are hiundreds of cars running around like yours without issues

[peterg]

he's not having any issues..... sounds like it'd be purely cosmetic - personally I wouln't bother

I've not noticed any overheating issues or difficulty starting when engine hot

[Cleggy the Spyder Man]

if you all read his first post again - he has not had any overheating issues

[Cleggy the Spyder Man]

oh Pete beat me to it

[SteveD]

even less reason to do it than

[Dave Eastwood (Gadgetman) - Club Chairman]

Unfortunately, doing it for aesthetic reasons is probably going to be the least successful, without a bit of work.

I've seen a few done now, presumably for heat management reasons, as all the ones that have had the vertical-ish bit of the slot, (as opposed to the one sloping back up towards the windscreen/aeroscreen) have looked awful. The GRP is just too flexible and the minute the full width slots are cut, the heat of the engine bay and the flex in the bonnet you get when it's clipped down, tends to cause the slots to open up very unevenly. They end up looking like they've been. Ut out by a blind donkey.

It's possible though, if you could glass supporting metal framework in behind the grills to support the remaining grp, or perhaps bond mesh in so that again, it provided support for the remaining slats, that you could get it to keep its shape.

Alternatively, what I have seen done a few times that keeps the slats shape better, is to cut each slot out as three openings with a fiveish cm gap left before you cout the next slot. The remaining slats still move a little, but because each "slot" is now actually three openings, non of the individual openings is too long,

[s2rrr]

I think the photos from MLC look tidy. If the airflow at speed does'nt come out of those slots then they will only be useful when standing or travelling slowly or when no air flow encourages warming up, so could be useful. For that reason they may work. On a topical front, water can get in when stopped or travelling slowly and the fuseboxes/battery are generally around that area and would need some protection.

Just a couple of uneducated thoughts to consider.

Bob

[stephenh]

If you go out at all in the wet, wont you run the risk of rain water all over the plugs and plug leads, if you cut holes in the top of the bonnet?