Hybrid_From_Hell Posted August 10, 2014 Share Posted August 10, 2014 The EWP pump has made a HUGE difference to the 5.2. (More on this later on the build up thread), but when off roading with the underneath blocked the heat / hot air striggles to get out have thought for a long time about Bonnet holes a la : So, for those that have experience, pros and cons ? Steve F (Off Road Toad) says he thought they worked and also stopped the inside steaming up so much when wading, but would like a few more views before Mr Holesay has a party Thoughts please ? n Quote Link to comment Share on other sites More sharing options...
mad_pete Posted August 10, 2014 Share Posted August 10, 2014 I'd heard mixed things which makes me think maybe there is a thread somewhere perhaps, but how can cutting holes in things not work? Quote Link to comment Share on other sites More sharing options...
squaddiefox Posted August 10, 2014 Share Posted August 10, 2014 Look at jezza when they were in the jungle! Quote Link to comment Share on other sites More sharing options...
pat_pending Posted August 10, 2014 Share Posted August 10, 2014 Stick a block of wood under the front to hold the bonnet open a few inches and put a ratchet strap over it. That should tell you if venting the engine bay is likely to make any difference. You could get really technical and use a thermocouple to measure before and after temp's within the engine bay. I have a multimeter with a themrocouple that works well and cost about £30 in Maplin, so it's easy to do. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted August 10, 2014 Share Posted August 10, 2014 What you put and where very much depends on what speed you need it to function , as high pressure areas eg on wingtops when moving will stop any vents in that area from working as you would expect , eg forcing air in rather than extracting out , like wise at rear of bonnet . In some cases a rear facing vent might work whereas a front facing would not . Size of mesh can also have quite a large effect . There was quite a bit of interest in this subject in Australia (surprised!) as with the V8 in a defender the footwells and seatbase get so hot that you get burned on contact . HTSH Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 10, 2014 Share Posted August 10, 2014 I'm sure there was a thread on here a few years ago that said the bonnet holes as shown were ineffective when driving fast and caused the under bonnet temperature to increase. Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 10, 2014 Share Posted August 10, 2014 Here Nige, have a read of this post ... by you ... 6 years ago http://forums.lr4x4.com/index.php?showtopic=32380&p=314914 Quote Link to comment Share on other sites More sharing options...
ToyRoverlander Posted August 10, 2014 Share Posted August 10, 2014 Here's an interesting way to determine where holes will be effective : http://www.oman4x4.com/hoodvents.htm Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted August 10, 2014 Share Posted August 10, 2014 I did exactly that when my 90 was a V8 - and it made sod all difference. Now the same bonnet is on my TDi and it has made a difference...even more noise :-) Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted August 10, 2014 Share Posted August 10, 2014 I just fitted a couple of small rubber feet under my bonnet on the 80" to clear the radiator cap which is was rubbing sligthly, but during my many testdrives today I could clearly see a difference in the temp. A couple of other series in my club have done this mod too, because of heat issues (they run elec fans, i run stock S3) and they both say it does help heaps. So possibly a better mod? Atleast it is easier to reverse Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 10, 2014 Author Share Posted August 10, 2014 Here's an interesting way to determine where holes will be effective : http://www.oman4x4.com/hoodvents.htm And THAT is absolutely brilliant, have printed of to read in the bath later ....now...all you have to do is to get that image out of your mind .... Quote Link to comment Share on other sites More sharing options...
Team Idris Posted August 10, 2014 Share Posted August 10, 2014 We probably had the biggest problem of anyone for a while, as so many folk went to injection or Diesel before winch challenge got going? But It really caused us some heart ache with fuel boiling! The biggest cause of heat is the exhaust manifolds, which are less bad on a four bangers, as air can go up one side and down the other. On the V8 they are both pushing up like hot air balloons. I didn't think I could pull more air than they could generate, so we went for a blower fan to keep the carbs cool. But if you have a front rad I think a bonnet fan pulling air out would be good in a mud hole. Either way up, we arn't talking some little 2" holes here. If you need to dump all that rad air out through the top it's BIG hole time Quote Link to comment Share on other sites More sharing options...
Team Idris Posted August 10, 2014 Share Posted August 10, 2014 Have you considered a bigger gearbox tunnel? Sometimes you just need to give the air an easy escape route? And what about a bonnet with the back edge cut off? There's a funny reverse vortex thing going on infront of the windscreen above 25mph. It might suck air out? It was quite a shocker as I watched my frost blanket start moving along the bonnet to the front Quote Link to comment Share on other sites More sharing options...
SPendrey Posted August 10, 2014 Share Posted August 10, 2014 Oh dear, my first look at it (and without reading a thing) made me think he's installed a sunroof on his bonnet! A second look showed me otherwise, but the shininess (which I'm not used to) and what appears to be a handle of some sort made me think sunroof. Perhaps an electric sunroof is the right idea? Then you can turn it on/off when needed? Quote Link to comment Share on other sites More sharing options...
tacr2man Posted August 10, 2014 Share Posted August 10, 2014 If its just underbonnet temp you want to drop rather than actual running temp then getting unheated airflow increase will do the trick , eg as they did to a small extent on the TD5 with the little air intakes on the front wings , although it needs to get pretty high before you have to have a refrigerated heat exchanger on the fuel line like in the XJS V12 ! Quote Link to comment Share on other sites More sharing options...
ToyRoverlander Posted August 10, 2014 Share Posted August 10, 2014 And THAT is absolutely brilliant, have printed of to read in the bath later ....now...all you have to do is to get that image out of your mind .... The shower, or the bathtub are excellent places to come up with the best solutions to problems or issues one might have. Plenty of times it has worked for me I bookmarked that site ages ago when looking for info on venting the engine compartment. In summer I could hardly keep my foot on the clutch or brake pedal as it got really hot (exhaust just behind the bulkhead). The exhaust has been rerouted but I thought that those louvred panels on the side of the wings might be a good idea too, behind the front wheels. Gives the air that gets 'trapped' in those corners a place to escape. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted August 10, 2014 Share Posted August 10, 2014 Being the; Hybrid from hell, it should have 6R4 style wings on it with those big vents ! Quote Link to comment Share on other sites More sharing options...
zim Posted August 10, 2014 Share Posted August 10, 2014 Quote Link to comment Share on other sites More sharing options...
Jon White Posted August 11, 2014 Share Posted August 11, 2014 Just polish up those rocker covers and take the bonnet off hot rod style! Or have you still got that fugly wedding cake affair you could weld to the bonnet again? Lmao...... Jon Quote Link to comment Share on other sites More sharing options...
mad_pete Posted August 11, 2014 Share Posted August 11, 2014 Ceramic coating the exhaust manifolds stop it getting so hot in first place ? Quote Link to comment Share on other sites More sharing options...
Daan Posted August 11, 2014 Share Posted August 11, 2014 Ceramic coating the exhaust manifolds stop it getting so hot in first place ? Thats a good call. I run a lhd s3 rh wing, and a rhd s3 lh wing, so have the vent holes in both of them (no heater installed). That works, but the change that worked best for this problem is to remove the inner wheelarches, if you haven't done so already. The trouble with anything in bonnet is that it serves to end up in the cabin when the venting flaps are open, so I have always tried to avoid it. Quote Link to comment Share on other sites More sharing options...
smallfry Posted August 12, 2014 Share Posted August 12, 2014 In line with Daan, I used a 200 Tdi LH wing and a 300Tdi RH wing with just the "intake" plastic grilles installed with nothing behind them. Making them vent grilles instead. With the 3.5 Efi fitted at the time, the electric fan hardly ever came on. Even in traffic. Quote Link to comment Share on other sites More sharing options...
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