Underbonet & Intake temps

[whatthe?]

the HSV intake (can't remember which model) had a long thin intake that sat above the radiator to get the air you mention... as long as you don't want that air to actually pass thru the radiator, you may as well use it for intake.

I believe that would be the the VS Clubsport/GTS. I had one, although I was dubious about how much air could actually get in through that little thin opening it seemed to work very well in summer

[RWDboy]

Another thing I've seen done to improve under-bonnet ventiliation is to put spacers between the bonnet and hinges. Supposedly the vacuum generated at the base of the windcreen while the car's moving sucks out the hot air or something? Has anyone tried this? A customer at work also suggested running a bit of sheet metal over the top of the radiator to duct the air that gets between under the front of the bonnet down toward the intake? What else have you guys tried?

As oldcorollas said, the base of the windscreen is a high pressure area - not really a good spot for a heat extraction vent - it will work (as there is high pressure hot air underneath the bonnet) but not as well as it could elsewhere. The lowest pressure area is usually about 1/3 of the way up from the front of the bonnet.

Well designed vents are great as are the undertrays extending back under the engine from the base of the radiator which is designed to force more air through the "radiators"

I doubt the under-trays will work particularly well in all cases, simply because it will add resistance to the path of the air flow through the radiator... if you add resistance to that path, then you'll find the air will simply try to go around the radiator altogether.

AndyTTR -> although it may seem like the intake manifold gets 'really hot' i doubt that it will cause a *huge* increase in intake temperature. You could try coating the manifold, and you could also try putting an insulating material between the manifold and the rocker covers (as i'm assuming the manifold is some kind of aluminium, which is a fan-diddly-tastic heat conductor from what i recall).

whatthe? -> The front of the bonnet has quite high air pressure when the car is moving, even through a very small air opening it won't have much trouble breathing.

[petespipes]

I have read properly conducted scientific type tests which prove the effectiveness of the under engine trays.I got the link from Southo to an online mag with the articles but cant recall title.similiar to autospeed.Anyway the tests were well conducted and conclusive.They definitetly help with heat.They also assist with keeping road muck out of your electricals etc in wet conditions.

[Rodger]

Guys,

After reading through the thread again. I'd like to add my observations and comments.

As I see it:

It is the layout of the intake for this motor that is the primary factor in the heat problem and hence the resulting increase in the intake air temp and sluggish response when stationary or moving slowly. I bet once out on the open road again the performance returns as air can move around the enginebay to drop the temps.

From the photo of Alchemist's enginebay I see that the intake plenum and throttle body sit directly over the top of the engine, effectivly the highest point in the enginebay.

Just above it, is a bonnet covered with a nice thick insulating blanket.

The extractors are wrapped and at any normal road speed they would contribute little to the heat build up or to any heating of the intake.

When the car is stationary all the hot air is trapped in this enginebay under the bonnet, so heatsoak into the intake system is inevitable.

All of the coatings suggested, I believe, will only help when the car is moving and good air is flowing through the intake system as the coatings are used to slow the transfer of heat into the moving air but not fully insulate it.

A ceramic coffee cup is a good example of this. Keep the water hot in the cup and eventually the outside and handle become as hot as the water.

A good well designed Cold air induction system indeed helps as already discussed by lowering the intake air temps, but again it only works effectively when the car is moving at reasonable speeds. At idle the air moving through the intake is slow and can easily pick up the heat from the surounding metal.

A plate of metal or of an insulating material such as bakerlite will reduce the radiated heat and any hot air from flowing directly onto the the intake system but again, when the car stands still all the hot air will convect/flow up to the top of the motor where the intake plenum sits.

I believe the first step to acheive lower underbonett temperatures and hence reduce the intake temps is to remove the insulating sound deadener from the bonnet. This will allow the heat to soak into the bonnet metal and then be absorbed into the outside air by convection through it. It will also give a few more millimeters for air to move over and around the top of the motor.

A second step solution that I see, to reduce the intake air temps is to change the arrangement of the intake system.
Move the throttle body and plenum off the top of the motor and down to the passenger side. Then plumb the filter in from the passenger side front.

If at any time Alchemist decides to turbo the motor then this intake move will be of benifit as with a turbo the underbonnet temps will be even higher at the original point at the top of the motor.

Anyway I have spent my two cents worth.

Regards

Rodger

[takai]

My 2c worth now, The under engine trays are good, they pressurise the engine bay, and not only keep muck out but direct airflow quite considerably.

The bonnet insulation does have a lot to do with keeping internal temps up, sure without it you might notice some cracking of the paint on a highmount turbo, but that can easily be solved. If you do have cracking in a certain area, sand it back to bare metal and put a layer of POR15 onto the section then paint your normal colour over the top. Certainly worked for an engine bay fire, and thats far hotter than a turbo.

[Camryman]

That begs the question now of how the factory set up was originally and if the same factory car would have the same issues?

[Alchemist]

Hi Guys,

Wow, this thread has really generated some input. Unfortunately the 2JZ was always designed as a TT engine, and really everything is setup for it that was, it's unfortunate that the N/A variant has the intake right ontop of the exhaust, but that's just the way it is....

While ITB's would be nice pulling in the colder air from the other side of the motor, but the time I got a decent set of those I may as well have bought a half cut and gone TT.

So, what's happening, On Monday Tuesday I am getting fitted.

A heatshield with a bakerlite(or some heat absorbing material on the underside) made from staineless, not sure what thickness, but quite thick over the extractors. I am then replacing the intake piping(from steel) with 3" aluminium mandrel bends down to the front of the car much closer to behind the headlights than where the pod currently is. I'm ordering the factory CAI that sits ontop of the radiator and pushes air into the airbox, and I'm having an airbox made to shield the filter, plus getting a new filter element, should all be sorted out over the next couple of weeks. I'll post some pics when it's all done. I'll also report back if it makes any difference (hope so...), but I've got a mate helping me put it all together so it should be quite tidy...

On the bonet insulation, well, I quite like my bonet paint looking tidy, and that shield helps keep it that way, yes it keeps the engine bay hotter, but worth it in my opinion. Supra bonets are aluminium anyway so they disperse heat quite well.

One more edit...yes while the factory setup would have been ideal, this car came with the HKS filter when I bought it and none of the factory gear, all the custom stuff I'm getting done still works out cheaper than buying the factory seutp, and with the extractors I have now you cant fit half of the piping in anyway...

[Andrew162]

Fascinating topic guys.. I tried addressing this issue both when my car was stock and when the GT-Four guts got dropped in. Even in stock form the poor old RAV4 generated quite a bit of heat. I got a couple of EL-model Ford XR-6 vents fitted initially to relieve a bit of the high under-bonnet temps, and it did have some effect (while it was still a stock 3S-FE).


Damn that was a while ago...

Then in an effort to get a touch more torque the obligatory intake roar and some cooler inlet temps, I had some gadgets made up to replace the (rather pissy) stock intake box.


This was a pretty tidy little setup.

I decided to try and get more air into the K&N filter with a few designs, but the one that won out at the time was this...


I'm just glad that this plan worked out the way I wanted it to, so the pipe sat just behind the headlight and ran cleanly through to the air filter and buffetted by the heatshield. This setup worked damn well. The sprung-neoprene 3" piping was pretty cheap too.


I couldn't have done it right without removing this odd contraption which I've been told is a type of resonator to filter out stock intake noise.. it filled up the cavity in the bumper.

After the GT-Four guts were fitted, the heatshield no longer had use in the engine bay as the intake pipe was positioned differently (now fitted to the turbo) and was an awkward fit to the heatshield. Now I also had to consider the top-mount intercooler as well, because it generated a shitload of heat as well. Then it was decided to put in a vent directly above the intercooler, similar to the way the GT-Four's had, but getting my hands on one of these proved difficult. Got an S15 Silvia vent painted and put on, minus the sheet-metal that sat above the bonnet-bracing.
Unfortunately I can't use the duct I made in the bumper anymore, as the water-air intercooler pump sits there now. I'd have to relocate it several inches along the bumper to make it effective again.



This now relieves a lot of the heat generated by the intercooler, as well as the 3S-GTE being a bloody hot engine too. I wanted to try to keep the splash guards under the engine, but I had to lose one of these for the purpose of putting in 3" stainless exhaust piping.


As the engine bay is now, more or less... (minus the camel). Even in winter you can see heat haze rising from the vent, so it's doing it's job well.

BTW I've been told by a few sources that the spacer-under-the-hood idea (at the windscreen-end) to relieve more hot air isn't a great idea... mostly because it's somewhat illegal too. They like to reckon that in the unlikely event that you have a front-on smash at some ridiculous speed, that the hood would most likely detach from it's hinges and go straight through the windscreen and act as a guillotine. Who knows...

[Alchemist]

A vented CF bonet would also be nice, but at $900 or so, not budget friendly...

[RWDboy]

I have read properly conducted scientific type tests which prove the effectiveness of the under engine trays.I got the link from Southo to an online mag with the articles but cant recall title.similiar to autospeed.Anyway the tests were well conducted and conclusive.They definitetly help with heat.They also assist with keeping road muck out of your electricals etc in wet conditions.

Oh yeah - they can be efficient, but only if designed properly, just like heat extraction vents and bonnet scoops can be efficient. I would say that ideally you'd want the undertray to extend from the front of the front bar, to the radiator, and then further back as far towards the rear of the engine bay as possible, and preferably have inner wheel arch guards as well.

Every car will be slightly different of course, depending what you can fit and where and how practical it will be.

[Rodger]

Camryman,

The Japanese would be thinking of the cooler and very cold weather that the majority of the market these cars are sold to. That is Japan, Europe and Nth America.

The Californians probably experience the same problems as Alchemist and us do here in Oz with the higher temps.

The placement of the intake plenum on the Supra would not be a problem where temperatures dont get above 30 degrees C very often and in winter would actually help warm up the engine.

Rodger

[roadsailing]

I did some measuring with a thermocouple reader recently, i stick the wire junction in the centre of my air inlet pipe, then installed the pd filter back on over the top.

this is on a 4AGE sprinter, with a no name filter which is not enclosed at all, but i have relocated my radiator overflow and washer bottles to get a bit more room.

my inlet temperatures got up to around 55-60 degrees celcius on a cool morning, around 20 degrees ambient while sitting in traffic for a few minutes. when i took off, temperature would drop about 10 degrees by the time i got to 60, then roughly another ten a few minutes after that.

reason enough for me to enclose it, i will measure the temps again when i have done so.

[Alchemist]

Camryman,

The Japanese would be thinking of the cooler and very cold weather that the majority of the market these cars are sold to. That is Japan, Europe and Nth America.

The Californians probably experience the same problems as Alchemist and us do here in Oz with the higher temps.

The placement of the intake plenum on the Supra would not be a problem where temperatures dont get above 30 degrees C very often and in winter would actually help warm up the engine.

Rodger

Yup totally agree, as noted earlier the engine coolant actually passes through teh T/B to aid in warming it up, just have to undo Toyotas engineering

Also I've had heatshield fitted, and car is still quite responsive after 2 hours of driving in hot weather, so that's a big plus , once I get the pod boxed in the next few weeks should be perfect. Will post some pics soon...

[Rodger]

Alchemist

Good to read that intake temps are coming under control.

Look forward to the pics.

Good also to see Shinybluesteel able to do some research and record some actual numbers. Good data.

Regards

Rodger

[mic*]

With the ambient temperature ~23 degrees it measured ~22 (?) when the car was moving

This is called wind chill factor.

Coating extractors will keep heat out in the first place as has been said. Its the way to go. What hasn been mentioned is that what you trap in is better for your tubine wheel spooling up too. Its a two-fold gain.