An idea for added airflow in 1FZ engine

[PDoyle]

Heat rises. holes in the hood won't do it. The biggest under the hood heat problem is at idle.
Move the battery and install a flex fan pusher to draw/push the heat down under the engine... My .02... Attached website for flex-a-lite fans. Many choices...

http://www.flex-a-lite.com/auto/html/auxiliary-electric.html

 

[Aharon]

Below is a link on the Porsche Forums detailing an external water spray system that is used primarily on the track.

http://forums.pelicanparts.com/showthread.php?threadid=150982&highlight=rubbermaid

 

[sleeoffroad]

So, where does it go? I've seen the one you did with them in the cargo area, thought I'd seen one someone was trying putting it along the frame rail under the truck - where else could you relocate?

We have put them in the back with drawer systems, also under the truck in a custom box where the spare tire used to be.

 

[SUMOTOY]

do you think that removing the rear seal causes hot air to be drawn into the cowl vents and makes the AC work harder to cool?

I do. The barrier of high pressure from the windshield is what causes you to feel pressure out of the vents at speed when the climate control is off. Very little speed = pressure at vents.


Scott Justusson

 

[SUMOTOY]

Heat rises. holes in the hood won't do it. The biggest under the hood heat problem is at idle.
Move the battery and install a flex fan pusher to draw/push the heat down under the engine... My .02... Attached website for flex-a-lite fans. Many choices...

http://www.flex-a-lite.com/auto/html/auxiliary-electric.html

But heat rises. Holes in the hood will do it. If it's radiant heat it will when the truck is off becuase heat rises, if it's convection heat airflow will follow from a high pressure zone to a low pressure zone. The most effective convection airflow is that which would also follow the most effective radiant airflow.

The radiator fan creates high pressure in the engine bay. It needs a way out. If you use hood vents on a low pressure zone on the hood high pressure heat will find it's way out. Trying to force it down means you are using a fan to redirect where air naturally wants to flow. Which means exactly that you are spending energy to redirect, making the mod less effective than a hoood vent.

Here's what I did to one of my turbo cars. Radiator is located on the DS of the motor. I removed the inner high beams and directed air at the radiator at the DS. On the PS I removed the inner high beams and directed air between the exhaust manifold and intake manifold (non crossflow head design). When I added the hood vents, the heat and pressure out of them was incredible. 100f over ambient and yarn sticks almost straight up at 50mph.

I also did vents on my 4R turbo with the same results in pic 2. Pic 3 is a set of powder coated Z34 hood vents and my projected placement. Notice on all three designs, I went outbound of the HVAC intake.

Scott Justusson

 

[SUMOTOY]

I planned on using straight distilled water & switch in-dash to use only intermittently. I'll see how it works.. is blue wash fluid better in some way?

thru my brief research, I found trucks in afghanistan often spray water on the radiator during a hillclimb or other high-stress event to stop overheating. Low tech but shows the power of vaporizing water to take away heat!

It works better in really dry environs, less so in humid environs. The blue washer fluid contains achohol as an antifreeze agent, which increases the effectiveness of the evaporative heat exchange.

Good luck with it, I'm sure it will work, but hood vents will probably do the same thing with passive involvement. IMO, it's not the radiator effectiveness that's the problem, it's the exchanged air has no place to go.

SJ

 

[alia176]

I have placed a request for the loan of an OBD II scanner on my club web site. Then I can take some real data and see if I am making it worse or better. I will also remove the rear seal and see what that does. I can temp remove the washer bottle and see what that does. I'll create a new thread once I get it and post the results. Lots of great info here, I guess I need data specific to my truck.

Ken,

Are you sure you want to do this? As Sumo stated already, you WILL suck in engine heat through the vents, in his case, it was smoke! When the a/c is on, you'll simply suck in hot air out of the engine bay and try to cool it down; thus creating more work for your A/C system!

Empirical data has proven this method to be effective at cooling down the underhood temps but NOT at keeping the occupants free of smoke/under hood smell/fumes/etc. Unless you find a way to keep the seal intact directly in front of the vent holes to prevent the intake of fumes.

And what's with an EE not having his own OBD-II software?

Ali

 

[SUMOTOY]

Ken,

Are you sure you want to do this? As Sumo stated already, you WILL suck in engine heat through the vents, in his case, it was smoke! When the a/c is on, you'll simply suck in hot air out of the engine bay and try to cool it down; thus creating more work for your A/C system!

Empirical data has proven this method to be effective at cooling down the underhood temps but NOT at keeping the occupants free of smoke/under hood smell/fumes/etc. Unless you find a way to keep the seal intact directly in front of the vent holes to prevent the intake of fumes.

And what's with an EE not having his own OBD-II software?

Ali

Here's exactly what happens... When you are at high speed, the high pressure of the windshield will act as a barrier from most of that heat going down the HVAC.

When you get slow enough, the high pressure barrier is gone, and your HVAC blower motor now creates a low pressure zone at those intake vents near the windshield. High pressure created by the radiator fan blows the hot air out behind that seal, right into the low pressure zone of the HVAC intake vents.

If you are lucky, you have a very tightly sealed motor, and it doesn't create a 'stink' in the cabin (literally and figuratively speaking). Regardless, if you are putting high heat down into the HVAC system, you are offsetting radiator/condenser efficiency for exchanger efficiency of your A/C.

It's an easy mod, but I tend to put new seals on firewall rims, not remove them for 'better' airflow into the cabin.

Scott Justusson

 

[SUMOTOY]

I'll also share as a tech/safety steward at several track events, I see a firewall seal eliminated or a rear hood raise up (same thing in my book), I try to explain nicely the safety concern I have regarding it.

Romer, your engine may not be smoking now, but driving 60mph or even 25mph, an underhood catastrophic event can be deadly. Driver visibly impaired (understatement), vaporized antifreeze is a poison (PHH), vaporized oil is a poison, vaporized freon is deadly.

I watched scenario 1 at a track event a few years ago. Ever since, in any track event I organize, you remove the firewall seal, you don't drive. I'm advocating that rule for some club track events as well.

You can do this for testing. If it proves worthy, put hood vents outside the HVAC line of fire. I don't just preach this, I've cut lots of holes in hoods over the years, never once in the line of HVAC vents.

Soapbox off

Scott Justusson
'94 FZJ80

 

[citadel]

Scott,

when are you gonna give us some knowledge on hood vents?

 

[SUMOTOY]

Scott,
when are you gonna give us some knowledge on hood vents?

I'm still recovering from the Aux fan posts... Hey, ck out post 85, that's where I plan on putting them. Ebay has those z34 hood vents all the time. Anyone else can certainly beat me to the punch.

Several here already have actually, though I suspect they are all grinning at the debate, and feel no need to post any data.

I'll get there in Part IV. Glad we have the interest.

SJ

 

[PDoyle]

I'm still recovering from the Aux fan posts... Hey, ck out post 85, that's where I plan on putting them. Ebay has those z34 hood vents all the time. Anyone else can certainly beat me to the punch.

Several here already have actually, though I suspect they are all grinning at the debate, and feel no need to post any data.

I'll get there in Part III. Glad we have the interest.

SJ

I just hate even the thought of cutting holes in my $15k truck hood.

 

[SUMOTOY]

I just hate even the thought of cutting holes in my $15k truck hood.

I hate the thought of having my 80 overheat because air can't get out from underneath the hood. I hate the thought that my intake air temps are 100f over ambient *before* my supercharger starts heating it.

Rover SC's didn't like that idea either. They cut holes in the sides of the fenders instead.

Scott Justusson

 

[landtank]

I would still like to see a number in degrees of what unexceptable hood temps are. My initial thought on the vents was to increase air flow for better cooling. I've now accomplished this through the clutch mod. So the logical next step for me is to identify a need for vents, which I'm trying to establish. My first readings where 144* which considering the engine is at 180*, this doesn't seem to bad to me but I really don't know.

 

[PDoyle]

I was gonna mention Toyota engineers already hashing this out during the design process of the 80's. But,I recall the earlier trucks (like pictured earlier in the thread ) paint pealing on the hood because of the heat raise under the hood. I don't have a supercharger. Sometimes I wish I did but...

 

[SUMOTOY]

I was gonna mention Toyota engineers already hashing this out during the design process of the 80's. But,I recall the earlier trucks (like pictured earlier in the thread ) paint pealing on the hood because of the heat raise under the hood. I don't have a supercharger. Sometimes I wish I did but...

That's my 4R actually. Those vents are mounted just about perfectly above the turbo, and just forward of the brake master and other DS obstructions. Rick, you need to measure the PS of your truck.

Scott Justusson

 

[landtank]

I can't help thinking that a weak fan clutch in stop and go traffic won't help keep the air flow going and allow the engine compartment to get hot.

I know that now there is a lot more air movement under the hood after my clutch mod at idle.

 

[landtank]

That's my 4R actually. Rick, you need to measure the PS of your truck.

Scott Justusson

I will today, but what is an unexceptable temp under there?

 

[SUMOTOY]

I would still like to see a number in degrees of what unexceptable hood temps are. My initial thought on the vents was to increase air flow for better cooling. I've now accomplished this through the clutch mod. So the logical next step for me is to identify a need for vents, which I'm trying to establish. My first readings where 144* which considering the engine is at 180*, this doesn't seem to bad to me but I really don't know.

Better cooling of what Rick? You have increased the airflow through the radiator at lower rpm's. That's a frst step. I'd suggest a measure of the airbox pre and post mod, and a measure of the firewall on the PS pre and post mod.

My data shows increases in both, with just a small 10in condenser cooling fan installed. This indicates to me, that the radiator exchange is good, but the heat management is not. You have increased the pressure in a marginal low pressure zone (post radiator fan).

Heat management theory would say, you need to chase the heat downstream. If the heat exchange in the radiator is high, but heat coming into the engine is more, the efficiency of your mod decreases. And/or if you increase the pressure on the engine side of the radiator, your efficiency gain is less than if you have a corresponding decrease in pressure in the engine bay.

My goal is to get heat out efficiently into a low pressure zone on the hood. This will increase the efficiency of radiator heat exchange, because it lowers the pressure behind a given fan/given clutch. You have possibly addressed 1/2 the equation. I went after dash vents A/C efficiency myself. I found it increased airbox temps.

Scott Justusson

 

[SUMOTOY]

I will today, but what is an unexceptable temp under there?

+1f over ambient?

I think we should look at it from the perspective of what's optimal. Ideal temps (100% thermally efficient) would indicate that the sum of the heat management mods results in ambient temps in the engine bay.

We know that's not possible. However, a 50% thermally efficient passive mod would be very acceptable (and pretty easy to attain IME). We need more data before we can establish that. With 95 ambient I have 165f at the firewall at idle, and 200 at the airbox.

(165-95) *.50 = 35f drop at the firewall
(200-95) *.50 = 52f drop at the airbox

My goal will be going after the airbox temps, since I know decreasing low pressure will decrease temps elsewhere. My main concern and target is air density pre supercharger being the highest. So I will target something higher than 50% at the airbox.

Make sense?

Scott Justusson