ABC'S of 80's Cooling Part IV - Hood Vents

[SUMOTOY]

Photoman's underhood pic reposted

Here's the pic Photoman took of the underhood of his truck showing the bracing you are dealing with. Which specifically I chose not to, and my total install time is 2 hours. My vents are mounted as far back in the 'V' just outbound of the diagnal brace where Photoman has his vents mounted

I'll also make note that in 'Da Hood' thread from a couple years ago, LandTank has a good post about flow (in all caps), he might want to reread

Scott Justusson
FZJ80 Supercharged and vented hood

 

[LandCrusher'70]

I thought about using these: E46 M3 Vent. Maybe in the fenders?
They even come with a template for cutting.

 

[SUMOTOY]

I thought about using these: E46 M3 Vent. Maybe in the fenders?
They even come with a template for cutting.

Those will work LC, I also thought about the ones I mounted in the hood going there as well, they fit no problem. My concern was how much trapped heat those would pick up, since the venting hole in the far corners of the engine bay were pretty low. Certainly a great mod at ram air speeds.

The LR SC uses those massive gills back there, as do several of the big rigs. Certainly can't hurt, but I'd guess the hood vents would be more beneficial in terms of placement. And don't forget you will get a log of grief from the swimmers in this forum!

Good price too!

Scott Justusson

 

[beaufort-fj60]

here are some others... http://www.oman4x4.com/hoodventinstall.htm

waggoneer used these on his 62 with the merc

 

[LandCrusher'70]

Those will work LC, I also thought about the ones I mounted in the hood going there as well, they fit no problem. My concern was how much trapped heat those would pick up, since the venting hole in the far corners of the engine bay were pretty low. Certainly a great mod at ram air speeds.

The LR SC uses those massive gills back there, as do several of the big rigs. Certainly can't hurt, but I'd guess the hood vents would be more beneficial in terms of placement. And don't forget you will get a log of grief from the swimmers in this forum!

Good price too!

Scott Justusson

They sure look sharp. I'd delete the M3 though.

The vent wouldn't be that much lower (if at all) than the intake in the fender. Water gets in there either way, with or without a vent.

They would probably look good in the hood also. Maybe I'll pick up a pair and play with the location a bit before actually cutting.

 

[landtank]

LandTank has a good post about flow (in all caps), he might want to reread

That was an old post and just pointed out the need for air flow to cool. Back then it was ASSUMED that the factory would have engineered the truck with optimum cooling. However, we now know that the fan clutch has been crippled from the factory and that greater air flow can be acheived easily without cutting holes in the hood.

Back then it was the SC'd vehicles that had the heat issues. This is prior to RavenTai's work with the temp guage BTW. And even now it looks like a SC'd truck might need hood louvers in addition to changes to the clutch to control idling temps.

 

[SUMOTOY]

That was an old post and just pointed out the need for air flow to cool. Back then it was ASSUMED that the factory would have engineered the truck with optimum cooling. However, we now know that the fan clutch has been crippled from the factory and that greater air flow can be acheived easily without cutting holes in the hood.

Trapped heat hasn't really changed though Rick. Trapped heat is the problem. You can push harder, but that doesn't necessarily solve the problem. Adding more hot flow to the underhood river, doesn't mean the fluid will go where the trapped heat is, or that there will be less engine bay heat. In fact, most likely the opposite. I data logged and confirmed this in my measures of aux fan on/off vs engine bay temp measures.

Some data with vents installed:
87 ambient temp
A/C running
Aux Fan running
Heat soak cycle time at idle 15-20 minutes

Temp at(of) airbox 133F
Temp at Firewall = 116PS/118 DS

Given the air filter temps TRU measured are my outside airbox temps, I suspect the vent over the airbox does a great deal of good things.

Back then it was the SC'd vehicles that had the heat issues. This is prior to RavenTai's work with the temp guage BTW. And even now it looks like a SC'd truck might need hood louvers in addition to changes to the clutch to control idling temps.

Could be unique to the SC, though several folks seem to have the problem of low A/C performance with the stock truck at idle. You can address the high pressure zone, the low pressure zone, or better yet, focus on the ratio to optimize heat escape.

If you increase the high pressure by moving more air, it's even more critical to make more pressure zones for it's release. Your exact comments about flow in that post.

My subjective evaluation confirms my measures, A/C performance is better, restart hot rough idle is gone (biggest noticeable difference) and my truck has better tip in throttle response. None of which accompianied my 10kcst fluid swap.

Rick, not sure why you are so against this mod. If it does release more heat, why not do it? Why not do the aux fan? Why not take out the shroud?

IME, each of these steps confirms quite a few common heat management issues in many automotive and truck applications. Extreme envirionment doesn't have to include the SC. We've identified Sand, hard off road, slow offroading, high ambient, towing and long hill climbs as extreme heat environments. Hood vents is a good way to address them all, without compromising the good toyota gave us from the factory.

Scott Justusson
'94 FZJ80 Supercharged

 

[landtank]

Rick, not sure why you are so against this mod. If it does release more heat, why not do it? Why not do the aux fan? Why not take out the shroud?

I'm not against doing them if there is a need to. I don't see the need right now. I'm not one to mod something just for the sake of making a change. And if I have an issue I'll start with the least invasive change and then step up from there until the issue is resolved.

If to get the AC temps a few degrees cooler at idle I have to add an aux fan and cut holes in my hood then I'm not going to do it.

However if the truck is running hot and the only way to get the temps down is to cut those same holes, then that is what I'll have to do.

My engine temps are under control and while the AC had a charge it worked just fine. All this in some of the hottest weather on record here in New England while towing a trailer. About as bad as it gets for me.

 

[SUMOTOY]

I'm not against doing them if there is a need to. I don't see the need right now. I'm not one to mod something just for the sake of making a change. And if I have an issue I'll start with the least invasive change and then step up from there until the issue is resolved.

If to get the AC temps a few degrees cooler at idle I have to add an aux fan and cut holes in my hood then I'm not going to do it.

However if the truck is running hot and the only way to get the temps down is to cut those same holes, then that is what I'll have to do.

My engine temps are under control and while the AC had a charge it worked just fine. All this in some of the hottest weather on record here in New England while towing a trailer. About as bad as it gets for me.

A strategy. I'd advocate that you may want to take some measures Rick. Get a IR temp gun. What you can do is add performance by releasing trapped heat, specifically the heat exchange release that you've added by fluid changes in the fan.

What we can do with this data is significant. We can take airbox temps (intake air temps) and relate them directly to performance. We can increase convection efficiency by adding vents, and we can have better hot start characteristics than what Mr. T delivered from the factory.

What *if* removing the shroud increases heat exchange performance? Maybe that a fluid change might not be necessary? What *if* adding an aux fan increased the cooling efficiency of the A/C? What *if* releasing trapped air decreases intake air temps significantly enough to measure HP gains?

My goal is to try things differently than the factory to optimize 1fefz heat management. I did the 10kcst thing within a couple weeks of owning the truck. Before the SC, before the clipped blades. Then moved on to the Aux Fan, then moved on to the hood vents. My plan is to move on to electric fans too. Why all this trouble?

Because I believe what toyota gave us in 1980's technology can be improved, in theory and application. I'm not a purist, I'm a performance guy. Not only in the racing sense, but in the evaluation of heat management modifications that have sound theory and application. My focus is to be able to run my truck at 100C, using electric fans, hood vents, and heat management goals to stick it there in the widest of operating parameters. There's nothing bad in it. In fact, quite the contrary, only good, if you believe the engineers.

Why? Because 100C temps are the standard in terms of measureable performance parameters in wear and fuel mileage. Double dipping the benefit.

Rick, your methodology on the fan thermo was good. Your old posts claiming 'first suggestion' on venting hoods was sound. I hope you appreciate the folks that are actually taking on the practical applications of an aux fan, optimizing it's trigger device, dropping in hood vents and even electric fans. Delete the shroud, take measures, clip the blades take measures. All done with objective/subjective measures and evaluations.

I appreciate you believing that what you have is fine for you. Because it appears to be. I believe what we have from the factory is good, and it can be better. In this particular vent mod, the objective/subjective gains are so great, there is no doubt in my mind, that this road will be followed by a lot of folks here. The nice thing about it is that your well documented fluid swap in the fan, only helps in reaped benefits.





Scott Justusson
'94 FZJ80 Supercharged

 

[landtank]

Scott, by all means, optomize your ass off.

All I want is exceptable cooling, which I didn't feel I had. If I start to see hot running temps again I'll have to look into it again, but for now it's running just fine.

The thing I don't quite understand is you keep posting that 210*F is what you want the engne to run at so it will boil moisture out of the oil properly. Now you're constanly looking to increase the cooling of the engine through optomization. This seems couter intuitive since the more you increase your cooling the easier it will be for the engine to maintain the thermostat set point of 180*F. Which according to you will cause issues.

 

[Walking Eagle]

One word: Safety

In my shop, I do it on race cars and actually cut out the bracing for the additional weight savings. For street cars it compromises the front end crash engineering characteristics. Hoods are designed to fold up, not guillatine the occupants of the vehicle. My concern with cutting braces is in a front end impact, the hood will most likely sever at the cut brace and potentially do bad things afterwords. More specifically, it just won't do what it was designed to do, whatever that means...

The back of the hood should catch, and then the hood folds in half - on most cars.

At the very least, if you cut out the braces, and you can ignore how it may effect the way the hood deforms in a crash, chances are it's going to pop up and down while driving, cause now there isn't anything keeping that big flat piece of sheetmetal from doing that. More you cut out more it will move on ya'.

 

[Waggoner5]

Use an inside trim ring to allow the hood to be sandwich the vent to the ring. I made some out of aluminum and molded them to fit the contour of the hood. Safety was not my concern, it was more for aesthetics allowing the hood liner to be pulled tight against the hood. I noticed 0, zip, nada, temp difference at the IAT sensor. I did see a reduction in under hood temps but not enough to make much difference. Oh well they look good. I know you guys are tiered of looking at the engine in one of my trucks but this shot shows the ring and fitment.
G

 

[cruiserdan]

How the hell does one get tired of looking at that motor?

There's lots of 500 inch Merc's in cars.............

 

[Waggoner5]

I think I saw your avitars hand move...

 

[cruiserdan]

I think I saw your avitars hand move...

Beer goggles?

 

[concretejungle]

what a pink-taco motor....

 

[Tools R Us]

Ok, my hood scoop story. I have molded composite scoops, vents, ducts, etc. for many cars and airplanes, have the tools, air saws, nibblers, grinders, etc. and have no problem cutting up sheet metal or composite to install them if I thought it was significantly beneficial. Small vents are aerodynamic devices, they work well when properly designed and placed to take advantage of airflow and pressure differences. When there is little airflow over them, like when wheeling, they deliver very little flow, so if your cooling system is designed to cool properly with full load at low speed they are mostly useless.

My last rig was a 4runner and wheeled with and worked on a bunch of them. The second gen 3.slows are very tight under the hood, if anything in the Toyota offroad world is going to "block" or "trap" airflow it would be these, the 80 is a wind tunnel in comparison. But the 3.slow trucks still manage to cool well.

A buddy had a problem that we attributed to heat soak and the racer in me suggested hood vents. Him and his buddy thought it was a good idea and come up with some Nissan Z car vents. They had some of the slots molded mostly closed, so we took the die grinder to them, ported them for max flow and installed them. With the motors running, heat come out of them and they looked cool, so mission accomplished!

We hit the trail and the first observation was that at the speed that we cruised forest service roads, the heat from them hit the driver in the face when the window was down. The hot air hit the windshield, went around the A pillar just above the mirror and in the open window. His buddy had a valve cover leak that seeped onto the exhaust and was getting that in the face, whining about affixation. So by the end of the day both trucks were taped up.

We did some more playing with them and found that some hot air came out of them. When the motor was turned off there was a slight improvement in cool down time. Did a bunch of runs taped and open and found that we couldn't measure any difference in anything that mattered. In the end we made a pair of aluminum block off plates and I had to hear him whine about getting wax out of those silly vents until he sold the truck, like it was my fault or something!

There are good reasons that most vehicles are designed to exhaust hot air underneath. First is safety, to protect you from fumes, etc. Second is for passenger comfort, it's much easier to insolate the bottom side if the vehicle, than the top with all of the openings. If you look closely at stock hood vents you will see that a lot of them are just for show, ether they are molded with very small openings and/or they have "drip trays" that restrict flow big time.

 

[SUMOTOY]

Hood vent stories

Wagoneer
Did you measure any results, do the yarn test to make sure you were in a low pressure zone? IME, hood vents on the high part of the hood are in high pressure zones, so their effectiveness at speed will be minimal. One of the reasons Mr. T puts hood scoops on the rise of the hood, it's a high pressure zone. However, during low speed crawling they should allow heat to exit them. In your specific case, you have a very open engine bay, so I'd venture to say "improvement" might be negligible

TRU:
I have yet to put hood vents in a vehicle that don't do what they are designed to do. The *key* is to make sure you have a low pressure zone for install to get forced convection at speed. The biggest mistake (and I see a couple here) is to put vents in a high pressure zone. In just about every 'raised' hood, low pressure zones will be found on the low part of the hood. IME with hood vents, using the proper low pressure zones, they have quite noticeable and measureable results. All stories aside, as mounted in my 80, the difference is measureable AND noticeable.

I won't attempt to explain 'other' chassis stories. I can certainly look at W5 and Photoman's installs, and have concerns specific to high pressure zones at speed. They can help with underhood temps in low speed situations, but no data was presented to support or discount that. What I can and have done, is identified high trapped heat in my engine bay, and addressed it systematically, and with accepted theory and practice. It appears to contradict TRU and W5 experiences. What's the difference between theirs and mine?

What I can do, is take measures of *my* 80, with the vents installed as pictured. As is my modus in all vehicles, I used yarn to confirm the low pressure zone at speed, and also is my modus, mounted the vents outbound of the HVAC intake vents. And as I expected, I got very similar results to a variety of other automotive applications in terms of measureable difference, and noticeable difference. So much so, the only mod with more noticeable difference, was the additon of the supercharger itself.

Hardly preaching, only a well seasoned tweekster with a lot of hood vent application experience, identifying method and results of a heat management option in extreme environment. All opinions to the contrary so noted.

Scott Justusson
FZJ80 Suprercharged

 

[SUMOTOY]

Scott, by all means, optomize your ass off.

All I want is exceptable cooling, which I didn't feel I had. If I start to see hot running temps again I'll have to look into it again, but for now it's running just fine.

The thing I don't quite understand is you keep posting that 210*F is what you want the engne to run at so it will boil moisture out of the oil properly. Now you're constanly looking to increase the cooling of the engine through optomization. This seems couter intuitive since the more you increase your cooling the easier it will be for the engine to maintain the thermostat set point of 180*F. Which according to you will cause issues.

LT:
Again, get the IR temp gun, and measure underhood temps. I did before and after, and got exactly what *I* was looking for, a *massive* reduction in airbox temps. As I established in ABC IV my primary concern is intake air temps affecting my compressor efficiency of the supercharger. I haven't measured my 'air filter' temps yet, but I certainly can expect a drop even closer to ambient, if I've turned the oven temp down by 70F. This isn't just a SC problem either, high intake air temps is the same as running a stock 80 at high altitude.

210F engine temp is also my goal, and it's very simple to get there, the hard part is maintaining it. As I've already indicated, it's my intention to ditch the mechanical fan (Part V) in favor of dual electrics. We know that a engine temp probe will take care of the 210 part. In the meantime, what I can do is test a bunch of misconceptions in opinion on this very forum.

The fan shroud is the first one. A lot of misconceptions about it. And all the opinions and theoretical postulations on it, it takes 5 minutes to take it off, and give it a try. In fact, one of the times you guys are squeezing silicone into your VC, try *not* mounting the shroud back up. I read Christos post over a year ago about tossing it in the garbage, and with the aid of 10kcst fluid, just did removal without wrenches. And at speed, it appears to give better heat exchange without compromising low speed cooling. You don't have to believe me, it's 5 minutes.

I clipped the blades, I run with a plethora of cores missing from my rad, I run the green coolant. There are posts here from many, you can't do that in the summer! I did with a supercharger and 24 foot trailer.

What I am targetting is better heat management Rick. 10kcst I did a long time ago. I propose that mod will cause problems under lockup at high rpm. IME, not opinion.

Rick *you* claim to be the first to propose hood vents 2 years ago on this forum. Hey, I agree, and did them. And had measurable results. And until I put in the electric fans, it's a measureable and noticeable difference in how my truck runs.

So I'm the guinea pig to 80 BS. I have done things systematically, measured them, and not at all lost sight of my ultimate goal, better effective heat management. It's not counter intuitive, it's exactly how I planned out my ABC's threads, and is exactly following the goals I established for my machine before I even took possession of my truck.

I expect to catch a lot of crap for it all too. I'm sure you'll excuse me for just plunking away at my truck, reporting up my mods from SC to hood vents. And quite possibly bucking a few welll seasoned broncos on this forum in the process.

Scott Justusson
QSHIPQ Performance Tuning
94 FZJ80 Supercharged

 

[Dusty]

I dont get all this IR gun stuff. The temp needs to be tested from under the hood with the hood down and I dont see the value of reading the temp at the vent. Here are the temps I want to compare

1. How does the water temp change with vents or any other mods. This is the temp that lets me know what the motor is doing. If we dont have a good water temp gauge our data is almost useless in my opinion. So we need to do the oe temp gauge mod or put in an aftermarket one

2. How does the intake charge temp change with mods. so we need a prope in the intake or a good OBD reader for the 95-97 machines.

I have done testing of my oil cooler (pre-turbo) with digital probes in oil pan and water temp and the mod made negligable diff.

I have had a 12" haden electric pusher fan on my truck for 2 weeks now and it makes no diff in digital water temps and I cant feel any change in the ac parked in the heat