[alien]

Hey all - im sick of my extreme under-bonnet temps... it gets too dam hot to lift the bonnet in summer and the heat even melted a fuse! (the fuse wasnt blown but the plastic melted).

i DO NOT want a bonnet scoop, and whatever i do i want to do myself... i have a drill, angle grinder with cutting and grinding discs, a socket set, screwdriver set, pliers and most importantly to some, a hammer =P

i was thinking of drilling 8 or so holes at the top of the 'speed hump' in the bonnet, then using something round and 'V' shaped to smash into the hole to kind of countersink it, so it looked cleaner... what else is do-able though that will let the hot air out and not stand out like dogs balls???

[royce]

the fuse melted cause it has more than 20 amps running through it full time, go google commodore fusebox for comparisons, for under bonnet to be that hot the oil in the sump would boil and the airbox would melt

your holes are also in a high pressure area, so when moving will do nothing

if you want to improve venting, give a clear path to the vents in teh bonnet, move your batteries and whatever else is in teh way

[alien]

the passengers side is well clear and breathable - but the snorkel on the drivers side as well as battery wont let the drivers side vent work properly.

the fuse that melted was a 15A to the thermo fan - but theyre cheap fuses off ebay... hmm

fuse aside though, the bonnet does get SUPER hot - where is a good spot to add more venting??? I would have thought in the speed hump, perhaps near to the firewall would be good as the air is forced through the front and against the firewall - so adding holes at the back of the bonnet would let that air out?

[royce]

insulate teh bonnet

[89_tintop]

you could always do what sliders do and raise the back part of the bonnet up to allow the hot air to escape..

as royce said about the fuse it is not from under bonnet temps but from high amperage runnung through it.. it is usually cause by a poor contact between the fuse and the fuse holder connections.

[buzbox]

I'd get some fibreglass cosworth style bonnet vents and face them rearwards so it sucks out the hot air as apposed to forcing air in. I had them on my FJ20t bluebird and it looked good and worked very well..



A cheap trick is to put a few washers under the bonnet mounts to raise it, but side on it looks a bit dicky witht he rear higher than the front

[alien]

what if i took the lip off the back of the bonnet so where it joins the cowl is open a few mm?

dunno about those vents - i cant help but think theyll get full of leaves etc... lol i spose anything would, but yeh.

[PJ.zook]

Which would you prefer, picking a couple of leafs out every few weekends, or melting shit under your bonnet?

[alien]

leaves =) definitely leaves!

still not sure on locating any venting i do add though... the extractors give off a crapload of heat, and the engine sits only 50mm from the actual bonnet so i assumed up high and toward the back would be best?

[royce]

Insulate the extractors too

[alex]

royce wrote:

Insulate the extractors too

x2

[klaery]

Raising the back part on of the bonnet doesn't really help (at least not with most performance orientated cars, not sure about zooks). In most cars air flow is generally designed to travel through the front and then under the car. Raising the back of the bonnet (or cutting holes etc) actually disrupts this flow and can work to raise under bonnet temps.

[alien]

really? i was thinking because theres so much air going under the car it was creating a whirlpool effect under the bonnet, rather than if i were lower down the air creating a vacuum under the bonnet?

as for insulating pipes - doesnt this usually lead to the pipes rusting out more?

maybe i need to devise a talcum powder delivery system so i can drive along and work out where the air is actually going.. lol

[royce]

fronts of cars are a high pressure area, rear of bonnets are high pressure, underneath is low pressure because of this (take your bonnet off and blast up the highway, will run hotter) so air runs through pretty well, your engine being close to teh bonnet will heat it up but doesnt mean underneath is too hot, some cars you open the bonnet just normal driving and you cant stand near it

[alien]

mmm i dunno - the engine temp goes up when im crawling etc as well as if i go at or above 105km/hr for an extended amount of time... thermo fan solves the crawling temp issue but i can only assume that the venting under the bonnet is the cause, as even on a 40 degree day if i drive above 20km/r up to 100km/hr the temp is fine.

[royce]

do you have an engine fan?

[klaery]

Yep as Royce says usually doesn't help and in fact makes things worse. My brother and I both have/had turbo toys and did the tool drifter thing and put spaces under the back of his sprinter bonnet only to have heating problems. Lesson learnt by both of us

[alien]

yeh still have the engine fan =)

[BJPK]

its an engine its going to get hot. do you know how an internal combustion engine produces power??? as said insulate the extractors if concernd either heat wrap them or fab up a shield. why would they rust more? any trapped moisture would just burn off.

[alien]

BJPK wrote:

why would they rust more? any trapped moisture would just burn off.

good point.

[atari4x4]

royce wrote:

insulate teh bonnet

royce wrote:

Insulate the extractors too

problem solvered...

[alien]

haha yeah i'll give the tape a shot for sure...

i always heard tape caused the pipes to crack etc - assuming it was due to trapping moisture (not thinking of heat drying it out, der) - but just did a quick search on wrapping in tape and it appears the generally accepted opinion is that the tape keeps the heat in great, but this makes the pipes brittle through the extra heat theyre taking?

Is this only in the performance engine world or is tape really going to severely shorten the life of the extractors?

[royce]

how much awesome super power heat do you reckon a 1.6 can generate

[alien]

can't say i ever measured it or would have the gear to do so =) still, a valid question given its a clear concern to many people...

how many of you are running taped pipes? =)

[royce]

ran for ages on old pipes on my mini, no drama

on a street car how often are you running at full power?
reckon the heat cycle and nasty shit corroding them inside out will be worse than a higher steel heat

[alex]

alien wrote:

can't say i ever measured it or would have the gear to do so =) still, a valid question given its a clear concern to many people...

how many of you are running taped pipes? =)

i am there is some pics in here

http://www.auszookers.com/index.php?nam ... &start=390

they are awsome i can put my hands on the extractors for a bout 5 sec till it starts burning

[alien]

ahhh yep =)

ok cool - so, supercrap to get the tape or should i be looking at a certain brand/type???

[Che]

What about hotrod style venting, but on the bonnet? That'd allow pretty good airflow... dunno if it's a DIY job tho

[alex]

alien wrote:

ahhh yep =)

ok cool - so, supercrap to get the tape or should i be looking at a certain brand/type???

no go to queensland diesel spares it cheap there

[klaery]

The cracking due to extra heat you have heard of would most probably be on stainless piping. Stainless does not handle heat cycles like mild steel does. That is why stainless turbo manifolds always have to be very thick steel and even then eventually fail anyway. Also wrapping does hasten corrosion though in my experience it isn't something to really worry about. Have you considered ceramic coating? I have no experience with this but if you are really worried it may suit your application.