Engine bay cooling

[jungle]

I've been doing a lot of looking into this with Trotty and some convos with Steve et al.

That’s where I am at the moment, if you can afford it then ceramic coat all the things.

So what exactly are you trying to achieve here. Yes I understand what you said, however you do not mention what temps- you talking inlet, underbonnet, water temps etc etc?

1. What is your current under bonnet temp.
2. How much cooler do you think all these things will actually achieve 5,10 degrees?
3. From the above answer, what do you expect to gain.

All I see is a lot of work that will, in all likelihood, result in you not seeing any quantifiable gains. I wish you luck, however if you're after a performance gain, I think you'll be disappointed.

 

[kevin]

i agree that there will be no or little performance increase, however, everything you find on these forums is that its best to install larger coolers (radiators) for the transmission, the intercooler,... so when you are able to get the overall under bonnet temp down this will result in cooling all the other components down a couple degrees as well, and from how i am looking at it, every small gain is good and will result in an overall better performance and lifespan of those components.

 

[jungle]

i agree that there will be no or little performance increase, however, everything you find on these forums is that its best to install larger coolers (radiators) for the transmission, the intercooler,... so when you are able to get the overall under bonnet temp down this will result in cooling all the other components down a couple degrees as well, and from how i am looking at it, every small gain is good and will result in an overall better performance and lifespan of those components.

Bigger isn't necessarily better. More efficient is better. However there are many cheap intercoolers on the market now days in the standard-ish 600 x 300 x 75 mil size.
If you are serious about flow, you'd pay the money and buy and ARE into cooler which maximises Efficiency flow and cooling. These however are expensive much more expensive than buying a cheap 200,300 $400 intercooler off eBay.
Is it worth it probably not for a streetcar. A track car or similar, definitely then.
As an example I run a RE radiator in my track car that's no bigger than my intercooler. And I never had any issues with water temps.

Oil coolers are a different matter there are not many matrix available on the market so fitting biggest one is generally better for oil cooling.

A few degrees in the big scheme of things really gonna make zero difference for component life performance etc etc

However I do applaud you for trying and Applaud you for trying to do the best you can with what you've got.

 

[slickd1]

expecting an intake intake manifold temperature drop of at least 50F, so 30C, consider the fact that air travelling through the intake manifold is compressed and spread out so travelling slowly, which means it will more efficiently transfer heat. Not trying to cool the air down after compression (intercooler), trying to avoid heating on the way in and our intake manifolds are ideal for it, they run crazy hot.

added bonus of heat shielding exhaust is more air speed at the turbos, and less work the cooling system does to remove heat that should have gone out the exhaust

If there’s a measurable improvement on a cold day, then this is very likely to have at least some effect.

totally agree that bigger isn't necessarily better, the bigger the volume of air post turbo, the more lag

 

[Schneider]

Few interesting things to comment on here. As Jungle said, what temperatures are you expecting to change and by how much?
I take it intake air temperature is your first concern.
Judging by your comments, how long do you really think the air is in the pipes for? I done the maths once for a front mounted GTi-R. Intake to valve was maybe 2.0 seconds with a laggy setup. It would be interesting to see how you actually measure the intake air temperature drop too. Our only air temperature measurement is from the MAF. Are you willing to insert a probe into the intake manifold?

· Insulate the intake from the radiator (lots of radiant heat here, and conductive heat through the intake itself. The airbox acts as a spacer, and flow also slows as it hits the larger volume box)

Seriously doubt you will see any benefit from this. Plastic and air are both poor thermal conductors. Air won't be moving slow enough to heat up significantly over ambient. Highest intake air temp I have seen was 50oC sitting in traffic on a 34oC day. Parramatta road traffic at that for near an hour... That is still below the 58oC timing trim in the ECU. Remembering post MAF temp's are not seen by the ECU.

· Remove the coolant loop through the throttle body (we’re literally running hot coolant through the throttle body, Trotty mentioned that there is a wax pellet and this allows us to have a higher idle when cold, so you may loose this function) but need to confirm with both kinds of throttle body.

ClubVR4 guys have been doing this for years. First comment they all make after doing this, they can touch the intake manifold after a drive without getting burnt. Might be something there, but again air will be moving pretty fast through it assuming WOT - remembering air is a poor thermal conductor.

· Include at least one phenolic spacer in the gasket setup leading to the intake manifold (The intake manifold is large, has a big surface area, slow, dense airflow sits above the block and rear exhaust manifold getting radiant heat from them both, it also is a very effective heat sync through the stock steel ‘highly conductive’ gasket sucking heat from the entire block and distributing it to the intake air)

Same as above.

· Heat shield the underside of the intake manifold

And again as above. Diminishing returns really.

· Needless to say, big intercooler.

Jungle sums this up best. Bigger does not mean better. Efficiency and flow is what you are after. That comment doesn't just consider IAT but also the airflow to the radiator and the rest of the engine bay. Bigger (thickness being the major concern) means reduced flow and cooling for our engines.

Then we go to underbonnet temperatures?

· Insulate the exhaust manifolds, dumps, and the top section of the downpipes. (best cheap way to do this is to remove the heat shields, give them a paint, #baybling, use the cheap exhaust wrap and with a lot of fiddling as neatly as possible wrap the crap out of it all, each exhaust manifold tube separately with no gaps, and follow down around the turbos as far as you can down the front pipe, do it in sections and use steel cable ties so it’s still easy to pull bits off if you have to. Be careful you don’t interrupt the operation of your waste gate actuator. Replace the stock heat shields over the wrap.)

Keep stock heat shields - agree. Adding some extra heat shielding over the turbines might be useful if you try and shield the turbos from the heads. As you pointed out ceramic coating would be more useful on the exhaust piping. Exhaust wraps remain controversial in that lifespan of the parts is typically reduced. Rust and the prolonged heat the wraps bring might be worth thinking about. You'd probably want to clean up and repaint any part you intend to wrap.

· Vented bonnet in the negatively pressurised area in the centre front of the bonnet.

Logical. Could just add that the vent design is as important. I’ve seen a few vents which could also act as intake scoops once moving.

· A full under tray will provide initially less cooling, but greater downforce, venting the rear of the under tray creates another negative pressure port for the engine bay increasing intercooler flow and pulling some more hot air down and out of the engine bay.

Really depends on how you define full undertray. Sealing off the bottom of the engine bay with a couple well thought out vents could work – but is high risk. Competition style trays would suffice though – tray to the edge of the front bumper or tray to the front axle.
I still think you should really let go of this ‘downforce’ idea. I feel you are just setting yourself up for failure, expecting improved grip. Eliminating lift and creating downforce are two different things. Any force created needs to be transferred to the chassis for it to be useable. Most people will end up mounting a tray in a similar manner to the OE product – attached mostly to the front bumper and splash guards. That’s the last place you would want a downwards force applied considering how many guys only have a few bolts left holding their bumper in place.
The point of the undertray is to smooth flow under the vehicle. Smoothed flow will help draw air from the edge or vents of the tray – depending on the location. It’s the turbulent mess that can cause problems. Yes – when stationary an undertray may help make thinks a little more toasty.

· Fix the front bar, to fit the Jap numberplates we have a large section of the centre of the front bar blocked off (more prominent in the PFL), get a slimline numberplate, mount it up on the bumper, cut out the block of plastic behind the existing plate, you’ll need to replace the grille with something that flows at least as well as stock (which is quite good) so if it’s the aluminium universal anodised stuff then make sure it’s a very open weave version.

Kind of surprised that ducting has not been mentioned at any point. So much air is wasted with both the PFL and FL front bars – FL I would say is far worse. Creating the right guides and sealing areas between the intercooler and radiator could be more useful than the other mods you have suggested. All fluids prefer a path of least resistance. Think which is easier; going through a heat exchanger or the gaps alongside it.
The benefits of ducting would be amplified with the use of a well vented bonnet and undertray set up. Just take some time to think about where/how you want to route the airflow.

Give it all a try. Some parts may work better than others, but don't go expecting miracles.

 

[slickd1]

Few interesting things to comment on here. As Jungle said, what temperatures are you expecting to change and by how much?
I take it intake air temperature is your first concern.
Judging by your comments, how long do you really think the air is in the pipes for? I done the maths once for a front mounted GTi-R. Intake to valve was maybe 2.0 seconds with a laggy setup. It would be interesting to see how you actually measure the intake air temperature drop too. Our only air temperature measurement is from the MAF. Are you willing to insert a probe into the intake manifold?

Am getting a temperature monitoring setup sorted, but ATM will only be able to do up to 200C

2 second resident time (the one you calculated for the GTR) in the intake side pre-turbo sounds about right at 700cfm.

Seriously doubt you will see any benefit from this. Plastic and air are both poor thermal conductors. Air won't be moving slow enough to heat up significantly over ambient. Highest intake air temp I have seen was 50oC sitting in traffic on a 34oC day. Parramatta road traffic at that for near an hour... That is still below the 58oC timing trim in the ECU. Remembering post MAF temp's are not seen by the ECU.

fair point, to be honest the biggest difference will be at low revs, with not much airflow, not expecting a measurable difference from this, it just seems best practice seeing as its so easy and cheap to do

ClubVR4 guys have been doing this for years. First comment they all make after doing this, they can touch the intake manifold after a drive without getting burnt. Might be something there, but again air will be moving pretty fast through it assuming WOT - remembering air is a poor thermal conductor.

@ 40 degrees C, running 15 psi the air density is double that of the ambient temperature external air (.144 lb/ft3 instead of.078 lb/ft3) so already the effective air speed for that specified volume is halved, the cross section area of the intake manifold is approximately 0.1m2 with an average flow path length of 0.3m (to make things simple), so a manifold volume of 0.3 m3, with an air flow at maximum throttle of 700CFM or 1189m3/hour, that gives a resident time within the manifold of 4 seconds at full throttle, with an inner surface area for heat transfer of approximately 0.7 m2.

Thermal conductivity of aluminium is so high (205 W/mK) that it is basically infinite as far as transfer to air goes, the limiting factor is the thermal conductivity of the air itself. The fact that the air is compressed and cooled (increased density) effects its thermal conductivity, effectively doubling it compared to what it would be at atmospheric pressure. admittedly its still not much, but it should have a measurable effect.

Same as above.

And again as above. Diminishing returns really.

Jungle sums this up best. Bigger does not mean better. Efficiency and flow is what you are after. That comment doesn't just consider IAT but also the airflow to the radiator and the rest of the engine bay. Bigger (thickness being the major concern) means reduced flow and cooling for our engines.

Fully aware that a more efficient intercooler is better, but the most cost effective way to do this is just to go a big, tube and fin as long as its got a decent fin density

Then we go to underbonnet temperatures?

Keep stock heat shields - agree. Adding some extra heat shielding over the turbines might be useful if you try and shield the turbos from the heads. As you pointed out ceramic coating would be more useful on the exhaust piping. Exhaust wraps remain controversial in that lifespan of the parts is typically reduced. Rust and the prolonged heat the wraps bring might be worth thinking about. You'd probably want to clean up and repaint any part you intend to wrap.

great point! will have to chuck on some rust converter and protective paint before the wrap!

Logical. Could just add that the vent design is as important. I’ve seen a few vents which could also act as intake scoops once moving.

yeah definitely, there's a small low pressure area in the bonnet, and just cutting holes willy nilly won't help, easiest way is just to mirror an evo

Really depends on how you define full undertray. Sealing off the bottom of the engine bay with a couple well thought out vents could work – but is high risk. Competition style trays would suffice though – tray to the edge of the front bumper or tray to the front axle.
I still think you should really let go of this ‘downforce’ idea. I feel you are just setting yourself up for failure, expecting improved grip. Eliminating lift and creating downforce are two different things. Any force created needs to be transferred to the chassis for it to be useable. Most people will end up mounting a tray in a similar manner to the OE product – attached mostly to the front bumper and splash guards. That’s the last place you would want a downwards force applied considering how many guys only have a few bolts left holding their bumper in place.
The point of the undertray is to smooth flow under the vehicle. Smoothed flow will help draw air from the edge or vents of the tray – depending on the location. It’s the turbulent mess that can cause problems. Yes – when stationary an undertray may help make thinks a little more toasty.

totally disagree, effectively reducing lift and increasing down-force are exactly the same thing, and the transfer of the energy to the chassis doesn't have to occur through the undertray itself for that method to be effective, the entire base of the car transfers the downforce by the reduced pressure underneath the rear of the car as it moves forwards. imagine a 1 psi drop in under car pressure, theres over 7,000 square inches under the car! ...however you are right in that practically achieving this is not really possible on a car that rides as high as ours does, and having excessive rake just introduces extra turbulence as air gets dragged in from the sides :-(

Kind of surprised that ducting has not been mentioned at any point. So much air is wasted with both the PFL and FL front bars – FL I would say is far worse. Creating the right guides and sealing areas between the intercooler and radiator could be more useful than the other mods you have suggested. All fluids prefer a path of least resistance. Think which is easier; going through a heat exchanger or the gaps alongside it.
The benefits of ducting would be amplified with the use of a well vented bonnet and undertray set up. Just take some time to think about where/how you want to route the airflow.

Give it all a try. Some parts may work better than others, but don't go expecting miracles.

to true! its too easy to fall into the trap of thinking air has a decent amount of inertia to push it through the radiator and intercooler, might have to think about better ducting too... new ideas!!!! sweeeet!

PS I reckon this conversation is getting epic

 

[slickd1]

Haha, whoops! Manifold volume and cross section is wrong, soo, 0.03, not 0.3m3, reducing resident time to... 0.4 seconds :-P

 

[trotty]

I thought 4 seconds was a bit long. Lol.
Best temp reducing mod yet was removing the rear rubber strip
At the windscreen and bonnet contact. Gives a solid 20mm gap along the back of the bonnet. Cruising speeds
I'm getting 14deg variance in engine bay vs ambient outside temp. A solid 5-6 degrees over stock. And I've found with under tray bonnet temps are reasonably the same at cruise but rises very quick
At standstill

 

[slickd1]

I'm wary of removing sealing at the base of the windscreen because it should increase engine bay pressure, and lift if you don't have an under-tray, and reduce cross intercooler flow. Where's the temperature probe mounted? that's pretty good.

 

[trotty]

Probe is mounted on the ic
Pipe after the top
Y pipe. So where the overflow bottle is.

 

[Schneider]

0.4s really isn't a lot a time. Temperature and pressure don't have the same effect on thermal conductivity. Air would probably still be of the order 0.03 W/Km. Convection along the boundary layer will be present, but the majority of the air volume won't take part in any cooling of the manifold. This comment actually best explains how one should treat their intake pipes. Thermal barriers should be used on the internal surface if possible with a means to aid thermal convection on the external surface.

Part throttle heating is considered a good thing. That's how you improve fuel atomisation and allow the car to run leaner than normal. Nothing wrong with that under cruise conditions where you might only use 15kW.


Something you might be missing is the intake manifold currently acting as a heatsink for the heads. Again could be considered good and bad. Hotter engines burn more efficiently but removing the heatsink and coolant loop may aid radiator efficiency. Not to mention using an insulating gasket will change the height/location of any mounting points.


Not saying you will cut into a bonnet at random. I've seen some of the evo vent transplants. Some are executed terribly with too little leading edge lip and others being drawn larger than necessary - both width and trailing edge. Just meant think about the air flowing over the vent. You want it to act almost like an air curtain, otherwise it may fall straight back into the engine bay. The evo vents typically have a plate placed underneath the physical slot to guide air and minimise the chances of reversion. Monster bonnet vents appear to be the better executed aftermarket option.


A digression but I guess I am not being clear enough on the undertray comments. Yes lift and downforce are the same force, downforce is just a nice way of saying negative lift. What I have been trying to say is eliminating lift and creating negative lift should be considered as differing objectives. Eliminating lift is about providing a neutral feel to the car; you shouldn't notice a change in handling as the car picks up speed. If lift is present (be it positive or negative) the dynamics of the vehicle could change significantly as conditions change. The theory you use rely's on the airflow staying fairly smooth across a body. Both rake and the rough underbody of our vehicles will allow for a drop in the velocity profile soon after the air leaves the last smooth surface. Turbulent air as it hits the underbody, air spilling out the side of the car or spilling in cuts into the velocity profile giving possible sites of stagnation. The highest section of 'suction' will occur where flow is smooth - in this case the undertray.

This isn't about how you perceive things or how much you know or understand, but how others may read this. If a person knows nothing about aerodynamics and you say an item helps create 'downforce' - what do you think is the first image or thought that springs into their mind?


Daniel, you'd need to check the pressure differences to see if you are drawing air out or sucking it into the rear of the engine bay whilst driving. I don't think anyone has checked how much of a parachute effect the engine bay plays in our cars. If you are drawing air out, you may actually be messing up the way the aircon system draws air into the vehicle.

 

[slickd1]

freaking loving this convo, learning so much.


I had never thought about the rough underside of the vehicle creating drag and turbulence reducing velocity, therefore decreasing the vacuum effect. I imagine it would actually create lift/positive pressure under the car at higher speeds. I might look into the rest of the underside of the vehicle and how I can reduce drag there without sacrificing weight.


Yeah, I had my hopes dashed when I saw it was 0.4, not 4 seconds, and I imagine that the drag within the intake manifold would reduce heat transfer efficiency. Though it could also do the opposite by creating vortices within those tubes, I'd really like to see how air behaves in the intake manifold.


With the intake manifold acting as a heat sync for the heads, I’m wondering whether this is a good, or a bad thing. I was expecting lowering the heat of the manifold to reduce the intake temperature and increase air density, but it may be that having a heat sync to increase the thermal mass of the heads is a good thing.


When you say part throttle heating improving atomisation, is that heating of the fuel or air? I thought we wanted cold air in the cylinder to increase density. Does warming the fuel on the way in increase atomisation efficiency? Or are we only talking at low throttle, where we already have enough air in the cylinder to provide the requested power for the stroke. And does the fuel need to be atomised, or vaporised, increased temperature would definitely increase vaporisation/volatilisation, but potentially not atomisation. (In English “fuel turning into a vapour”, potentially not “fineness of the fuel mist from the injectors”)


“Hotter engines burn more efficiently” Really? Cool, I might need to do a little research into this and the reasons why as I’m pretty new to this mechanical/internal combustion engine thing. I have a reasonable grasp of science, but some of the specifics that are considered common knowledge in the car community I won’t have heard yet. I assume that removing the coolant loop from the throttle body should aid the intake manifolds effectiveness as a heat sink as well as increasing the radiators efficiency. Does the engine just reach optimum temperature and then get kept there by the cooling system?


I’ve already cut into the bonnet with some understanding, and used a venting style similar to the monster bonnet to maintain the original steel sub-frame. (Ours would cover up an evo style vent). I just used a $70 second hand bonnet, then stencilled it and cut it with a dremmel and cutting disc.


I may have sneaky access to 6 remote data-loggers at work which we can use to log temperature and pressure at different locations, we could then graph the pressure results (even within the intake). Then after modifications like new intake scoops etc, we can have a comparable starting point to measure the difference. These are meant for environmental logging of groundwater wells, so can deal with a bit of pressure, but likely not much above 100 degrees C. hopefully they are not effected too much by inertia, not sure what type of pressure sensor it is.


Also need to remember that the 0.4 seconds resident time in the intake manifold is at full throttle (700CFM) I’m not sure what the flow is at idle, or low throttle. But I assume this would drastically increase residence time of air in the intake manifold. I wonder if this would lead to efficiency benefits during normal low throttle use.

 

[MattF]

I thought 4 seconds was a bit long. Lol.
Best temp reducing mod yet was removing the rear rubber strip
At the windscreen and bonnet contact. Gives a solid 20mm gap along the back of the bonnet. Cruising speeds
I'm getting 14deg variance in engine bay vs ambient outside temp. A solid 5-6 degrees over stock. And I've found with under tray bonnet temps are reasonably the same at cruise but rises very quick
At standstill

Was just going to say that. Did this to my last few cars just for the hell of it.

 

[SLY-031]

Daniel, you'd need to check the pressure differences to see if you are drawing air out or sucking it into the rear of the engine bay whilst driving. I don't think anyone has checked how much of a parachute effect the engine bay plays in our cars. If you are drawing air out, you may actually be messing up the way the aircon system draws air into the vehicle.

THIS.

 

[stirlz]

anyone up for a monster bonnet group buy??

has anyone made contact with speedfactory lately? I emailed a couple of weeks ago and nothing.

How's this coming along ? I'm keen depending on price

 

[SLY-031]

THIS.

@trotty that wasn't specific at you either(your name being mentioned in the quoted text), was trying to highlight it to everyone

 

[trotty]

@trotty that wasn't specific at you either(your name being mentioned in the quoted text), was trying to highlight it to everyone

All good

 

[lateshow]

I have relocated my battery to boot and have this big filter now in the same place. I know that i need to design and manufacture a heat shield. Would someone like to comment on the matter....Which way to go? Does standard battery shield help at all? MAF temps are much higher than with standard intake.

 

[AKKO]

Enclosed with extra air feeds are probably the way to go unless you can plumb it lower...

Also are your running a MAF adapter of sorts?

 

[lateshow]

I have a little hole in my hood on top of the filter. We just fabricated a matching plate for MAF and then sealed it.