An idea for added airflow in 1FZ engine

[fzj80kidpen]

hmmm,
So any holes in the hood will vent out even if it looks like a scoop

 

[SUMOTOY]

hmmm,
So any holes in the hood will vent out even if it looks like a scoop

No. Normally the low pressure zones are vents, high pressure zones are scoops. As a rule of thumb, you need to get above the airflow boundary of a low pressure zone to find high pressure. That's usually at a min 3in level. However, it's pretty easy to identify where a scoop should be placed, just as it is a vent. Yarn taped to the hood.

Scott Justusson

 

[alkaline747trio]

All this low pressure high pressure stuff has me a little confused. Are we trying to create a vacuum or positive pressure under the hood.

 

[landtank]

What we want to do is locate a low pressure area on top of the hood that corresponds to a heat trapped area under the hood. Then when we cut a hole in the hood the low pressure outsde will vacuum the heat up from the inside.

Provided we are moving.

 

[alkaline747trio]

And where Sumo has his vents resting on his hood seems to be the best place decided on yet?

Also, concerning the hood spacers, what about fabbing something to block the flow of engine exhaust to the HVAC system? Or just keeping the air on recirculate?

 

[FirstToy]

you can test airflow over the hood w/ pieces of yarn or wet your hood and look at the water bead patterns. It changes a bit w/ speed. Lowest pressure, the yarn will stick straight up.
check out the link I posted to oman4x4.com

I saw a clever Jeep use the rear window vents from a 100 series on the hood! Looked pretty decent I must say.

removing the seal- man, I think all the doom and gloom is overkill. jmho.

landtank, thanks for posting your temp results. saw that thread

 

[SUMOTOY]

removing the seal- man, I think all the doom and gloom is overkill. jmho.

See Turbocruisers post 192 in blue fan clutch mod.

The seal is there for a reason. You want to remove it, the risks are pretty clear. If you want to take those risks in a test fine. If you want to take those risks with just you in the truck fine. Assuming those known risks with others in the truck with you, or others driving around isn't fine.

My thoughts on this are pretty clear, it's assuming risk. One no production automobile manufacturer assumes for good reason. Not sure why even testing venting is necessary. It's documented so many places as BTDT. It's not a question if it will do any good, it's just where it will do the most.

SJ

 

[SWCruiser]

Scott,
Are you definately going to install the Z34 vents? I think those would look asthetically perfect on our vehicles.

 

[Tools R Us]

OK, I will play took a little trip today, about 24 mile each way with about 5 miles on each end town traffic the balance in town highway. Moved the probe to the same location above the master cylinder that Rick used. The highest recorded was 158F near the end of the run, the only time I had to sit through two lights in heavy traffic. When moving and on the highway it fluctuated between a low of 136F and high of 147F depending on speed and load. Ambient 99-101F full sun, A/C set to CC vent temp 48-52F.

For the return trip moved the probe to the air box, stuck it between the pleats of the air filter. It fluctuated between a low of 128F and high of 139F. Made a quick stop ~5 min, to get another probe on the way back, the box heat soaked to 155F during the stop and quickly returned to 138F by the time I turned it off at the shop, about a mile in traffic. Ambient 102-106F full sun, A/C set to CC vent temp, didn't note.

I see no reason for concern with these numbers, in fact lower than I expected. The new probe is going at the fan output to get a baseline, as this is the main contributor and dominates underhood air temps.

 

[FirstToy]

Tools,
that sounds great. It is way lower than I expected as well. did you wedge your temp gauge down between the firewall and engine? That's the only other area I was interested in.

 

[Tools R Us]

Tools,
that sounds great. It is way lower than I expected as well. did you wedge your temp gauge down between the firewall and engine? That's the only other area I was interested in.

Not yet, but with two I can hit more spots sooner.

 

[SUMOTOY]

OK, I will play took a little trip today, about 24 mile each way with about 5 miles on each end town traffic the balance in town highway. Moved the probe to the same location above the master cylinder that Rick used. The highest recorded was 158F near the end of the run, the only time I had to sit through two lights in heavy traffic. When moving and on the highway it fluctuated between a low of 136F and high of 147F depending on speed and load. Ambient 99-101F full sun, A/C set to CC vent temp 48-52F.

For the return trip moved the probe to the air box, stuck it between the pleats of the air filter. It fluctuated between a low of 128F and high of 139F. Made a quick stop ~5 min, to get another probe on the way back, the box heat soaked to 155F during the stop and quickly returned to 138F by the time I turned it off at the shop, about a mile in traffic. Ambient 102-106F full sun, A/C set to CC vent temp, didn't note.

I see no reason for concern with these numbers, in fact lower than I expected. The new probe is going at the fan output to get a baseline, as this is the main contributor and dominates underhood air temps.

Good data Kevin. Now, let's take those numbers and work with them a bit, in an effort to show how density affects performance, then maybe the need for vents. This is a preamble to Part IV of my ABC thread, but the data is quite convenient. Thanks for nabbing it *in* the airfilter. A good other measure would be airfilter to box as a relation for those not so probe equipped.

We know from Ideal Gas Law Theory that D=P/R*T, so air density drops as a function of temperature increase (pressure constant), or as a function of pressure decrease (temperature constant). They are directly related. Let's assume Kevin to be at sea level (1000 mbar = 1 atmosphere = 14.7psi). Convert the 138F to 59C and the 104F ambient temp (rounded) to 40C. First, let's see the reduction in pressure due to temp. This chart is handy to compare percent loss of air density due to temperature.

http://www.ce.utexas.edu/prof/kinnas/319LAB/Book/CH1/PROPS/densgif.html

So, if we follow 59C on the density curve we get a value of 1.05 and at 40C we get a value of 1.15 a difference of 9% in air density going from 40C temps to 59C temps.

We also know that if temperature is a constant, but pressure decreases, we also lose density. The rule of thumb for altitude is a decrease of 3% air density for every 1000ft in altitude (temperature constant). So, to compare Kevin's measured air temps vs air density to altitude, an airbox temp measure of 138 (vs 104 ambient) 9% decrease in air density would be equivelent to running his truck at 3000ft.

An airbox measured temp of 155 (vs 104 ambient) is 12% decrease in density or equivelent to 4000ft.
And an airbox measured temp of 176 (vs 104 ambient) is a 15% decrease in density or equvelent to 5000ft.

What does all this mean? Well, if those airfilter temps get high enough, you might as well drive your truck in Denver! I compared altitude because those that have brought trucks into denver know they get doggy. This is also a good way to understand how cold air makes your truck feel peppier, because you have increased the intake density. This is also the logic and reasoning behind 'cold air intake' mods.

The bottom line. If we can reduce airbox temps by vents, shielding, ducting, or airflow improvements, we can increasse the performance of our trucks. The closer we get to ambient temps in the airbox, the closer we are to 'actual' altitude vs effective altitude.

Scott Justusson
94 FZJ 80 at 1000mb but living in steamboat with my measured temps!

 

[Tools R Us]

Last night the trip home 14 miles mostly in town highway, only took one look, most of the way there at 70 mph, radiator fan output, 131F, air box 102F, Ambient 89F, 11PM dark, A/C set to CC vent temp 48F.

Same trip on the way in this morning, radiator fan output, low of 126F and high of 137F depending on speed and load., air box 102-109F, Ambient 89-90F, 7PAM overcast, A/C set to CC vent temp 48-51F. Had to wait a few minutes on a train a couple of blocks from the end of the trip, radiator fan output 158F, air box 122F.

Most "cold air intakes" are designed to look good and remove $$ from your pocket and add them to theirs, bling! The one that LXextreme is so fond of posting pictures of would pull fan output air and not filter nearly as well, so a down grade as far as performance goes.

The factory cyclone air cleaner is setup deals very well with debris, has very big filter area and it looks like the air intake is well placed when taking offroad water, debris and performance compromises into account. A snorkel would be a good upgrade, well documented to reduce the dust load and water in the air cleaner and will pull cooler air. Next time that I am out with a snorkel truck, will have to put a probe in it and compare them on the same trail. I bet the biggest difference will be seen on low speed wheeling where the engine compartment heat soaks.

 

[SUMOTOY]

Last night the trip home 14 miles mostly in town highway, only took one look, most of the way there at 70 mph, radiator fan output, 131F, air box 102F, Ambient 89F, 11PM dark, A/C set to CC vent temp 48F.

Same trip on the way in this morning, radiator fan output, low of 126F and high of 137F depending on speed and load., air box 102-109F, Ambient 89-90F, 7PAM overcast, A/C set to CC vent temp 48-51F. Had to wait a few minutes on a train a couple of blocks from the end of the trip, radiator fan output 158F, air box 122F.

Most "cold air intakes" are designed to look good and remove $$ from your pocket and add them to theirs, bling! The one that LXextreme is so fond of posting pictures of would pull fan output air and not filter nearly as well, so a down grade as far as performance goes.

The factory cyclone air cleaner is setup deals very well with debris, has very big filter area and it looks like the air intake is well placed when taking offroad water, debris and performance compromises into account. A snorkel would be a good upgrade, well documented to reduce the dust load and water in the air cleaner and will pull cooler air. Next time that I am out with a snorkel truck, will have to put a probe in it and compare them on the same trail. I bet the biggest difference will be seen on low speed wheeling where the engine compartment heat soaks.

Completelly agree that most 'cold air intakes' hinder performance. I also suspect that those with forced induction will see greater temps, hence greater gains from getting airbox temps down.

I'm not a fan of snorkels, and am a big fan of the airbox and stock snorkel itself, save it's mounted on the wrong side of the motor. No question heat soak will be a problem at low speeds, another reason to address it. I also suspect that since heat soak also appears to happen at high load conditions, this temp/density phenom happens at the worst times.

The problem I see with snorkels is more from a negative pressure standpoint. Not as critical in a stock truck, but massively critical in a forced induction truck. Increasing negative pressure at the turbo/SC decreases compressor efficiency. The same effect as altitude, if Pinlet <Patmospheric, compressor works harder to make the same boost. More heat generated, less charge air density.

There can be no question however that any reductions in airbox temps will yeild performance gains based on Density. The question is which is most efficient and practical at getting ambient into the airbox. Another in the ABC's experiments I suspect.

I will go on record Kevin, that I won't remove the stock airbox, and most likely won't remove the stock snorkel to it. I like big swirling unrestricted coffee cans, never been a cone filter guy.

Dan, with a snorkel AND a supercharger, you would be the next logical one to post some airbox data.

Scott Justusson

 

[sleeoffroad]

Just another data point. I removed the shroud from the ShortBus in Moab last year and tossed it in the dumpster. I was tired of hitting the bottom of it and transhing the radiator.

Also trimmed all the little tips of the front of the fan so that it is further away from the radiator.

Have been running without a shroud for 2 years. Just recently did 1100 miles, probably about 900 of that on dirt/highway at highway speeds. Truck never ran hot, in fact, might be my imagination, but the needle seems to be lower than before with the shroud. Stock temp guage.

 

[SUMOTOY]

Just another data point. I removed the shroud from the ShortBus in Moab last year and tossed it in the dumpster. I was tired of hitting the bottom of it and transhing the radiator.

Also trimmed all the little tips of the front of the fan so that it is further away from the radiator.

Have been running without a shroud for 2 years. Just recently did 1100 miles, probably about 900 of that on dirt/highway at highway speeds. Truck never ran hot, in fact, might be my imagination, but the needle seems to be lower than before with the shroud. Stock temp guage.

Christo
My experience as well. Though I, er, removed the shroud without the aid of wrenches.

After augering the radiator with a slightly clipped fan again with no shroud, and measuring the aero flex interference, I believe that shroud has a lot of vortex turbulence in it, and is really designed to keep one's fingers out of the spinning blades. Something you glove test guys ignore anyhow.

SJ

 

[Rusty Phillips]

The factory cyclone air cleaner is setup deals very well with debris, has very big filter area and it looks like the air intake is well placed when taking offroad water, debris and performance compromises into account. A snorkel would be a good upgrade, well documented to reduce the dust load and water in the air cleaner and will pull cooler air. Next time that I am out with a snorkel truck, will have to put a probe in it and compare them on the same trail. I bet the biggest difference will be seen on low speed wheeling where the engine compartment heat soaks.

Those temps were in the air filter itself - right?

so if there was a significant heat transfer to the intake air thru the 3 gallon metal bucket the filter sits in, or the rubber hose that runs over the top of the exhaust manifold (or even in the large aluminum intake manifold) then the air temps that the engine gets are even higher - right?

is there some way to get your probe into the intake manifold itself?

if so, and if you happen to insulate the intake system (filter can, hose, and manifold) and recheck the temps - I would gladly buy you a beer the next time you are in South Carolina.

oh, and by the way - you are the man!!

 

[Romer]

Hell, why not take the shroud off and see if what they are saying is true.

 

[tech_dog]

One other reference point to consider is tests with PC temperatures that show case fans that blow IN to the PC actually increase temperatures. In practice, case exhaust fans work much better.

With the amount of air that's being sent into a turbulent frenzy by the engine fan, how much difference can the little vent cutouts actually make? I would also think that the turbulence in the engine bay would almost completely overwhelm the subtle force of the hot air trying to get higher.

If that's the case, anything that increases air flow out of the bay would have the most benifit, even if it was down low. This could be a shaped cowling under the vehicle that would create a low pressure point, or it could be an electric fan blowing down.

I've got a dual battery and currently have no overheating issues, but like this topic. I've got 3 wireless thermometers with remote read-out, and I'm going to stash them in a few areas, high and low, of the engine bay and get some readings.

 

[Rusty Phillips]

One other reference point to consider is tests with PC temperatures that show case fans that blow IN to the PC actually increase temperatures. In practice, case exhaust fans work much better.

mount a fan underneath your hood (mount the fan to the hood itself) pushing the air UP thru the new vent ??