Intercooler -------------

frank

Club Member
I read raised bonnets are trash since the base of the windscreen is high pressure
aye, the heater blows hot air while cruising eh, even with the fan switched off
i have the rubber seal removed under the back of the bonnet, for ventilation while stationary tho :)
 
Well it works for me. Pressure or not that's the direction of air flow so its created a vacuum... vacuum = suction.. suction = less hot air
Pressure differential might work in your favour still depending on the pressure at the front grill
 

frank

Club Member
i think the airflow at the back of the engine is very poor personally, the bonnet gets very hot on a summers day, and the heat from the sump and that water pipe just rises up through the inlet mani in traffic

dsc06145sj.jpg
 
Pressure differential might work in your favour still depending on the pressure at the front grill
There's no real route in for air as my rad blocks the whole front end.. I'll see if I have a pic somewhere.
The rear how ever is 1.2m x 50mm(or there abouts) open hole :)
Maybe I'm a special case
 
There's no real route in for air as my rad blocks the whole front end.. I'll see if I have a pic somewhere.
The rear how ever is 1.2m x 50mm(or there abouts) open hole :)
Maybe I'm a special case
I'm hoping your radiator is a good place for air to flow in through ;)
 

pollyp

Club Member
a Phenolic material like PTFE works best at insulating the manifold from the hot end, especially on track or in traffic, (perhaps also with stainless bolts to further reduce conduction) but 4 stacks of gaskets is better than 1 eh.

even after a track blast, my manifold with spacer is always stone cold :)

I have a very raised rear bonnet and it's surprising how much hot air flows out of it.

at high speed, I've not tested what the airflows doing considering the high pressure through grills and low pressure going underneath (I'll need to stick some wool along the raised bonnet soon).

but when stationary after a hot run or in traffic, alot of heat builds up very rapidly in that engine bay and having an open top is better than trapping it all in.

the opening at the bonnet rear may not be best sue to higher pressure as skymera says but the front top side of the bonnet may have a lower pressure (after the air strikes the blunt frontal face and goes up over the bonnet curve).
like those cosworth front bonnet vents
 
Before anyone says it... cadwell last year at an assumed 120-130mph (speedo only reads to 100) the bonnet didn't flinch
Its not going to come flying off :)
 

pollyp

Club Member
i think the airflow at the back of the engine is very poor personally, the bonnet gets very hot on a summers day, and the heat from the sump and that water pipe just rises up through the inlet mani in traffic

View attachment 31287

also remember the inlet mani always has a vast amount of cooling air flowing through it.
the temp of the inlet mani is the net result of heat input (from engine block, coolant heated TB and other heat radiation) VS heat dissipation into cooler sources (inlet air)

since the heat dissipation end is pretty much unchanged, reducing the heat input end will give the cooling air a better chance of bringing the manifold temp closer to ambient and so less heat transferred into the air stream itself.
 

pollyp

Club Member
I had a pyrometer? somewhere that could tell us the temps of certain spots during runs out

I've got them infrared thermometers but thinking a thermal camera would show the whole picture of heat distribution and would be fascinating
 
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