Air flow - Engine Bay

[Otterav]

Tapage,
What I was referring to was a "larger cooling capacity", ie more rows, and possibly thicker core if you cannot enlarge the length and width. I would suggest a thicker 4 row rad. I went to the triple pass 4 row desert cooler option on the US radiator. My new radiator fits into my original shell on the FJ/BJ mutation. Also make sure the air is being pulled through the without any leaks around the fan shroud, I use silicone rubber and closed cell weatherstrip to seal the fan shroud to the radiator. A very small area opening will cause a pressure drop on the engine side of the radiator and cause a loss of cooling airflow. Also check your fan clutch, if its not locking up at temp your cooling will be compromised.

 

[canucksafari]

There is a trade off with more rows to a point, as it reduces the airflow. The guys in the patrol forum were debating this. In the end, the "popular opinion" seemed to think a thicker core would be the way to ensure better cooling without going to a wider rad. That and fitting two large electric fans off of a Commodore car. As Eric says, ensuring all the air is pulled through the rad and not from around it should also help.

 

[Otterav]

There is a trade off with more rows to a point, as it reduces the airflow. The guys in the patrol forum were debating this. In the end, the "popular opinion" seemed to think a thicker core would be the way to ensure better cooling without going to a wider rad. That and fitting two large electric fans off of a Commodore car. As Eric says, ensuring all the air is pulled through the rad and not from around it should also help.

Indeed, the thicker/more rows is a compromise, the thinnest, widest, highest radiator is the best option. When the air goes past the first row of tubes it is heated X amount, and each successive row is seeing higher temp cooling air, reducing efficiency, but when underhood real estate is limited adding rows is the only option. The triple pass option makes a lot of sense too, since the coolant spends 70% more time in the radiator it has more time exposed to cooling air.
Hola
eric

 

[Dougal]

Not sure Id remove the thermo.

I think you should try a new one. With no thermo or a bad thermo - the water doesnt spend enough time in the radiator to cool off. Works fine around town, but on the highway or under load (like offroad) it will build too much heat.

It's not that water travels too fast, as faster moving water transfers heat better.
But more that many cooling systems need the restriction of the thermostat to get water flowing in the right direction. Sometimes removing them will cause localised overheating.

 

[roscoFJ73]

It's not that water travels too fast, as faster moving water transfers heat better.
But more that many cooling systems need the restriction of the thermostat to get water flowing in the right direction. Sometimes removing them will cause localised overheating.

Yes,without a t/stat ,the water pump is like an outbord motor in a swimming pool,lots of splashing but not much circulative flow.
If you place the outboard motor in a pipe,then you get flow

The t/stat also pressurises the water and helps eliminate cavitation in the pump rotor

 

[Talos]

Hi.

Had a very similar problem with my 3L-t hilux, it had a body lift so I had to lower the rad down, do you have body lift?

another thing I did was I opened up the fan clutch, cleaned out the gunk in there (silicone?) and filled the thing up with glue (sikaflex), temps improved ALOT after the clutch (a new one was like $300 at toyota)

 

[Tapage]

Hi all and thanks for all coments .. unluky this weekend my mom's come to visit and left no time to do some test in Tencha ..

She had no BL and yes .. I thought have enought space for one more row in the rad ( made it more thick ) but it means go with a custom 5 rows rad .. ( yes .. already have a 4 row rad ).

The test that I would do soon it's simple block the hood scoop air flow .. and see what happens ( sure the intercooler gotta run without air flow ) ..

The other option would " stuck " the fan clutch for a test ..

 

[Cañonero]

Sorry for bringing this thread back to life after so long, but this is very interesting.

Did you solve your heat problem blocking the hood vent?

Thank you

 

[Tapage]

wou ... pretty old thread.

At the end I'm still have cooling issues in Tencha .. maybe less frequent or less important .. I end with a new 4 rad .. and new Fan clutch .. it seems to doing better but still not the complete solution.

I'm in the process to get a engine oil cooler that I will run before my turbo and maybe help with the turbo oil cooling and in the same line the engine temp ..

 

[Cañonero]

And do you think the hood scoop is the culprit of your overheating problems, as it was suggested before?

I've seen a friend's new 120 series Land Cruiser with a top mounted intercooler without a hood bonnet, it has a channel under de bonnet that runs the air from the front to the top, and, when it gets to the intercooler, everything is incredibly good sealed and routed to make the air go only through the intercooler, but not directly through the engine bay.

Could there be a good reason to do that?

 

[Tapage]

Honestly at this point I'm not sure .. if I was open the hood and use the scoop without the turbo or playing with my IP fuel rate .. I can make a better conclusion .. but right now I'm not.

But I need to pint that isin't a oveheating problem at all .. ( well actually depends on opinions and concepts ) I can use Tencha as DD withour problems ..

Can drive she for 6 hours at 100km/h without problems .. it will start up the temp just when I start pushing she hard ..

 

[lshobie]

Is your turbo cooled from the radiator?

I use the new toyota HZJ79 radiator - aluminum and apparently very good for cooling.

I also agree that your engine compartment is pressurized from the top, try putting some side vents in - like the hood vents on the old 40 series. I remember wheeling the old 40's and the heat just pours out those hood vents.

When did this problem first start? As soon as the intercooler and scoop were installed? If so then that is your problem for sure. Go with the water/air intercooler - mine gets installed next week!

 

[Tapage]

When did this problem first start? As soon as the intercooler and scoop were installed? If so then that is your problem for sure. Go with the water/air intercooler - mine gets installed next week!

actually not .. but there is long time ago since I start tweaking up my diesel .. and I do my turbo and intercooler with hood scoop all at the same time ..

 

[Cañonero]

Why not trying to seal the hood scoop to the borders of the intercooler like in the Patrol picture you just posted?.

I may be wrong but I suspect that if you force all the air throught the intercooler, its fins would slow down the air minimizing the presurizing effect.

 

[Tapage]

Why not trying to seal the hood scoop to the borders of the intercooler like in the Patrol picture you just posted?.

I may be wrong but I suspect that if you force all the air throught the intercooler, its fins would slow down the air minimizing the presurizing effect.

You are right .. I just haven't take ( make ) the time to do it .. was involved in the office, tranny swap, axle swap and my next project, my hydro assist in Tencha .. but I need to ..

 

[Bozza]

And do you think the hood scoop is the culprit of your overheating problems, as it was suggested before?

I've seen a friend's new 120 series Land Cruiser with a top mounted intercooler without a hood bonnet, it has a channel under de bonnet that runs the air from the front to the top, and, when it gets to the intercooler, everything is incredibly good sealed and routed to make the air go only through the intercooler, but not directly through the engine bay.

Could there be a good reason to do that?

Probably not with this issue because air is still coming into the engine compartment, regardless of the route it takes to get in there. The issue here sounds like competing air flow. Air is assisted through the front grill by the lower pressure inside the closed body of the vehicle when it is moving...the lower pressure helps suck the air in. When you force air in via another route, like a bonnet scoop, you 'up' the air pressure in the engine compartment and you end up relying on the power of the radiator fan only to take air through the front. The set up can be more forgiving when you have induction happening in there (like a nozzle type air filter ala K&N) taking air out of the same space--or, as has been suggested by some Australians, you 'space' the hinge of the bonnet up near the windscreen to create a quicker escape route for the air flowing out.

All aftermarket intercooler set ups are a a compromise but you are not always sacrificing the same thing in a top-mount v front mount set up. Front mount nay-sayers often focus on the theories of contant pressure (the longer routing of a front mount eating up pressure and adversely effecting flow and causing 'lag') while the top-mount nay-sayers focus on the theories of contant temperature (you just can't pull as much heat out with a core sitting atop the furnace, so the shorter route is a false economy). But I would say that, in this case, you are seeing a different factor associated with the aftermarket top-mount. The engine compartment has a limited volumetric air capacity and if you shove a whole lot of air down through a scoop you have to be slowing down the volume of air coming through the front and through the radiator. Whether the vehicle is (already) quite near its cooling effiency limit will dictate whether this becomes an issue for you or not.

I think the cheapest experiment now may be spacers in the bonnet hinges, opening up a small gap under the windscreen. See if it assists air throughput.

 

[Dougal]

Probably not with this issue because air is still coming into the engine compartment, regardless of the route it takes to get in there. The issue here sounds like competing air flow. Air is assisted through the front grill by the lower pressure inside the closed body of the vehicle when it is moving...the lower pressure helps suck the air in. When you force air in via another route, like a bonnet scoop, you 'up' the air pressure in the engine compartment and you end up relying on the power of the radiator fan only to take air through the front. The set up can be more forgiving when you have induction happening in there (like a nozzle type air filter ala K&N) taking air out of the same space--or, as has been suggested by some Australians, you 'space' the hinge of the bonnet up near the windscreen to create a quicker escape route for the air flowing out.

All aftermarket intercooler set ups are a a compromise but you are not always sacrificing the same thing in a top-mount v front mount set up. Front mount nay-sayers often focus on the theories of contant pressure (the longer routing of a front mount eating up pressure and adversely effecting flow and causing 'lag') while the top-mount nay-sayers focus on the theories of contant temperature (you just can't pull as much heat out with a core sitting atop the furnace, so the shorter route is a false economy). But I would say that, in this case, you are seeing a different factor associated with the aftermarket top-mount. The engine compartment has a limited volumetric air capacity and if you shove a whole lot of air down through a scoop you have to be slowing down the volume of air coming through the front and through the radiator. Whether the vehicle is (already) quite near its cooling effiency limit will dictate whether this becomes an issue for you or not.

I think the cheapest experiment now may be spacers in the bonnet hinges, opening up a small gap under the windscreen. See if it assists air throughput.

The low pressure area under the vehicle extracts air faster than any hood scoop can bring it in. So that's not the problem.

Spacing the hinges up will not help airflow when moving (pretty sure that's a high pressure area when moving), but it will help the engine bay cool when stationary. Of course so will the hood scoop (aka chimney).

IMO overheating problems solving should start with the cooling system and the amount of heat being fed into it. More power from your engine results in a higher cooling load. Don't expect the stock system to cope.

 

[Bozza]

The low pressure area under the vehicle extracts air faster than any hood scoop can bring it in. So that's not the problem.

You miss the point. It's not about how it gets out but where it gets in.

Spacing the hinges up will not help airflow when moving (pretty sure that's a high pressure area when moving), but it will help the engine bay cool when stationary. Of course so will the hood scoop (aka chimney).

I disagree. It will assist only when moving. But, might not assist cooling even then. You have to understand that the temeratures around the engine and the temperatures in the engine (that the radiator is trying to take out) are not in the same league. Taking charged air out of the engine compartment doesn't help at all unless the replacement air flows through the radiator. My suggestion here is to experiment with an alternate escape for the air coming in then out through the intercooler core. If more air comes through the hood than the grill, and goes straight down and out through the bottom, it can baffle (like an air curtain) flow coming through the front.

IMO overheating problems solving should start with the cooling system and the amount of heat being fed into it. More power from your engine results in a higher cooling load. Don't expect the stock system to cope.

Agreed.

 

[Dougal]

You miss the point. It's not about how it gets out but where it gets in.

A bonnet scoop is not going to stop air getting in through the grill and radiator. It won't make the slightest of difference.

I disagree. It will assist only when moving. But, might not assist cooling even then. You have to understand that the temeratures around the engine and the temperatures in the engine (that the radiator is trying to take out) are not in the same league. Taking charged air out of the engine compartment doesn't help at all unless the replacement air flows through the radiator. My suggestion here is to experiment with an alternate escape for the air coming in then out through the intercooler core. If more air comes through the hood than the grill, and goes straight down and out through the bottom, it can baffle (like an air curtain) flow coming through the front.

Which part of higher pressure against the windscreen don't you get?
When moving you have more air pressure in front of the windscreen than you do in the engine bay. So you cannot remove air from the engine bay by packing up the hinges.

I suggest some background reading in fluid flow. Particularly stagnation pressures.

 

[gerg]

Lost of 1/4 mile racer guys use reverse hood scoops to take advantage of the downflow of air created by the windshield when the vehicle is moving. I personally find it offensive, but that is just me.
g