Forcing Air into the Engine Compartment, Engine Cooling ??? Options

[Highland]

I'm guessing it's been tried, but is there a downside to forcing fresh oncoming air into the engine compartment? I've read that removing the rain tray does not help cooling which tells me the 2 engine compartment side vents are more than adequate to feed the centrifugal cooling fan; so perhaps increasing engine compartment air pressure and reducing relative air temperature would help.

So don't laugh too hard at the pictures (IMG:style_emoticons/default/av-943.gif) It's a first pass attempt.

I did a couple of runs on my normal joy ride and am qualitatively seeing about a 5 to 10 degree head temp reduction and quicker cooling to normal temps after an uphill grade. Also cruising at 65mph in 5th I'm seeing about a 10 degree reduction in steady state temperature. I have a big hole in the back due to a 3D print problem and my duct tape keeps on flying loose so not getting full duct air. I just have a VDO head temp gauge on #3 plug. As many of you know the VDO has 50 degree hash marks; so not real accurate reads.

So is it correct that head temps are not affected by outside air temp, that's an oil temp thing?

Has anyone tried this? The stock grating is still in place. Can I be doing any harm?

[wonkipop]

Read these 914 aerodynamics papers:

good stuff mr. b. you have some good gear/research you have accumulated.

air flow along flanks of 914 confirms vw thinking on the old type 3.
the long louvre vents on rear guard flanks of those were into plenums that then fully seal ducted cooling air and induction air into the engine. they never had any tin-ware separating lower engine from upper engine. just a separated ducted cooling intake.

you want to keep your cooling air intake as far from your heated air exhaust as possible in everyday conditions of stop start go slow traffic. i reckon porsche got it right for the 914 as an everyday car (except when it comes to something like death valley/and or/australia). fortunately you don't get caught in traffic jams in death valley?

(IMG:style_emoticons/default/beerchug.gif)

as an aside, 917s just had a dirty big hole in the top and the fan sucked it straight in.
and they were going at 230mph. no ram tube etc for cooling. they might have been trying to ram induction air in later on.

[nein14]

What about these on a quarter with GT flares

[Mikey914]

I'm interested. We could thermoform some ducts that could be easily installed and removed without damage to the body. As noted in the aerodynamic studies there is a backward flow of air on the deck. Ducting to the sides would allow for cool air to displace stagnated air at a much faster rate. This should help with cooler Temp air supplied to the intake and fan housing. Resulting in a higher air density and cooler air over the head and cylinder fins.

As another member noted the aerodynamic quiet spot just past the firewall needs to be broken up. The air deflectors do this quite well. We added tip vortex generators to maximize the efficiency.

These are a pretty simple add to any car.
https://914rubber.com/floor-pan-air-deflector-for-914

We include the hardware too.

The LE spoilers also help.

[Superhawk996]

Read these 914 aerodynamics papers:

There is a flaw in that paper. It is physically impossible for a significant amount of air to flow upward on a stock car.

The papers are very cool - thanks to @jeffbowlsby for sharing them. I have not run across these before.

With respect to which way air flows, that is a limitation of the modeling. No effort appears to have been made to account for the flow into engine compartment induced by the crankshaft fan and I don’t think I saw sufficient model detail to account for actual underbody geometry and the underbody air deflectors on OEM. Focus of the paper real was on determination of Coefficient of drag. I may have glossed it too quicky and will re read later.

Overall I guess I’m still confused by the OP purpose of wanting more air flow on a strrret car. If it is in trying to make an air-cooled engine run at the same oil or head temps as a water pumper, then it’s just tilting at windmills. Air cooled engines simply run hotter due to the cooling dynamics involved.

If his car has some sort of overheating problem, it would be wise to find root cause of that rather than trying to re-engineer the air flow. But I applaud the experiments!

[mlindner]

Mikey, just installed your air deflectors on my 6 GT Tribute, very nice product and easy install. Also having good engine tin and rubber seals to body keeping lower engine heat out and all top cool air coming in going over cylinder/heads. Best, Mark

[Literati914]

Seems to me that the main heat issues (on a street driven 914) is when stopped at lights, traffic jams, stop-go traffic - ON HOT DAYS. As was mentioned, that heat really builds up under there. So the scoops to me wouldn’t be as important. Getting heat out from the underside of the tin might be nice though… what about some small fan arrangements under there that help to expel some of that heat? Maybe programmed to run off the oil temp sensor? And/or some modern type of heat shielding between the exchangers and engine? Just my thoughts on the subject, ymmv.


.

[914werke]

What are you trying to accomplish? Reducing head temps by adding/forcing cool air to the top of the engine (presumably to feed the impeller fan)?

I’m confused by the OP purpose of wanting more air flow on a street car. If it is in trying to make an air-cooled engine run at the same oil or head temps as a water pumper, then it’s just tilting at windmills. If his car has some sort of overheating problem, it would be wise to find root cause of that rather than trying to re-engineer the air flow.

(IMG:style_emoticons/default/popcorn[1].gif)

[Literati914]

As to what I'm trying to accomplish: Just trying to find another way of improving our cars. I actually don't have an engine temperature problem,

Did y’all miss the above statement? Nothing wrong with trying to improve the situation right?


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[914sgofast2]

Anyone tried gluing strips of yard to the top and sides of targa area where the low pressure spots are located so a scoop or spoiler could be used to direct air into the engine grill?

[JeffBowlsby]

Next question? Thse are al found on my 914 Classic site under Vintage Photos.

[914_teener]

Next question? Thse are al found on my 914 Classic site under Vintage Photos.

Wow..never seen these before. Just goes to show you that they knew what they were doing when they originally designed the body in white car.

When I first read the title of this thread...I don't think you want "higher pressures" in front of the fan. Like Mark said...you want lower pressure as this is a forward curved scroll fan. If turbulence is created around those tips, the fan becomes less efficient at doing this. Thiink of an airplane wing here. You might get cooler air but I seriously doubt you will get cooler engine temperatures by doing that as fan efficiency will be sacraficed. This is why the deflectors are there at the end of the body pan.

I had a side project where I was going to use exothermic paint on the cylinder bores and heads where the tips and exposed surfaces of the fins were not. I was also going to insulate the HE's exteriors and use exothermic on the tubes. My thought was to gain the difference in the exhaust and make the HE's more efficient and gain heat at the same time. Sold everything to Rob -Beat Navy and I think he went a different route with his car.

I think as designed the car does pretty well disapating heat. I used to drive mine over 100 degress often and never had any issues. I did run without the rain tray though during the Summer becuase of idling in traffic.

[BeatNavy]

My thought was to gain the difference in the exhaust and make the HE's more efficient and gain heat at the same time. Sold everything to Rob -Beat Navy and I think he went a different route with his car.

Hey Rob!

I put an external ceramic coating on those HE's and have been meaning to put them on my ride. I don't know whether the welding repairs or ceramic coating cause a fitment issue, but I could never get them to seat on my heads. Just wouldn't go over the head studs, so rather than fighting it I just kept using my SS HE's.

Just before I recently dropped my engine (to fix a failing oil pump (IMG:style_emoticons/default/dry.gif) ) I gave them another test fit. I aggressively ran a rat tail file thought the ears, and I think I finally have them so they'll work. I'm excited to see how they work and if the ceramic coating reduces heat transfer directly under the car in any appreciable way. Should get them on this week.

I agree with Literati914. My car's head temps are great, even when not moving. But my car's oil temps really spike without significant air movement under the car on hot days. I feel like the oil "cooler" is just cooking the oil over the HE's.

[914werke]

I'm excited to see how they work and if the ceramic coating reduces heat transfer directly under the car in any appreciable way.

It does. (IMG:style_emoticons/default/shades.gif) I did the same thing some 10 or more yrs ago with a NEW set of SSi's. It both reduced the the under car temps...some, & noise associated with the thinner construction SSI's but also DRAMATICALLY increased cabin heat production to the point even with the best sealing I could muster Id get some radiant bleed through the tubes into the cabin when off/closed.

[BeatNavy]

I'm excited to see how they work and if the ceramic coating reduces heat transfer directly under the car in any appreciable way.

It does. (IMG:style_emoticons/default/shades.gif) I did the same thing some 10 or more yrs ago with a NEW set of SSi's. It both reduced the the under car temps...some, & noise associated with the thinner construction SSI's but also DRAMATICALLY increased cabin heat production to the point even with the best sealing I could muster Id get some radiant bleed through the tubes into the cabin when off/closed.

Sweet, good stuff Rich. Except the part about putting heat in the cabin when you don’t want it! (IMG:style_emoticons/default/biggrin.gif)

I’ll follow up with my observations at some point.

[914_teener]

My thought was to gain the difference in the exhaust and make the HE's more efficient and gain heat at the same time. Sold everything to Rob -Beat Navy and I think he went a different route with his car.

Hey Rob!

I put an external ceramic coating on those HE's and have been meaning to put them on my ride. I don't know whether the welding repairs or ceramic coating cause a fitment issue, but I could never get them to seat on my heads. Just wouldn't go over the head studs, so rather than fighting it I just kept using my SS HE's.

Just before I recently dropped my engine (to fix a failing oil pump (IMG:style_emoticons/default/dry.gif) ) I gave them another test fit. I aggressively ran a rat tail file thought the ears, and I think I finally have them so they'll work. I'm excited to see how they work and if the ceramic coating reduces heat transfer directly under the car in any appreciable way. Should get them on this week.

I agree with Literati914. My car's head temps are great, even when not moving. But my car's oil temps really spike without significant air movement under the car on hot days. I feel like the oil "cooler" is just cooking the oil over the HE's.

Hey Rob:

Hopefully not a thread de-rail....but good to know you are still doing it and hope to collect on that beer...hopefully Springtime. I'll send ya a PM if I and when I make an East Coast tour. Love to see you new engine set up.

The idea was to exothermicaly coat the inside and outisde of the exhaust tube and insulate (ceramic coat) the outside of the stock HE's shells. Like insulating your house you would get better thermal scavaging in the cylinders and while at the same time getting less heating in the engine bay during hot weather....and maybe better heating from the stock set up. Don't know but that was the thought.

[wonkipop]

a detail i used to notice about vw type 3s was the difference between air grille intakes on a notch versus a fastback. the fastback had them on the flanks and shared its rear guards with the squareback. it would have made mass production economic sense to also share the rear guard set up for the notch but they didn't.
it must not have been aerodynamically good for the inflow into air intakes on the flanks.

the 914 is similar to the notch in a way. its a blunter rear to the cabin turret.




there was no difference in the rear profile rake of a 4 door 411/412 or a 2 door fastback.
somehow that rake must have better suited intake vents on the rear deck lid.
it is interesting where they position those vents on the various cars dependent on rear profile.

having said that, a 911 is a fastback shape and has the intakes on the lid, so the type 3 fastback is a bit of a mystery to me.

they didn't have any choice with the squarebacks, no other place but the flanks.

[djway]

I'm guessing it's been tried, but is there a downside to forcing fresh oncoming air into the engine compartment? I've read that removing the rain tray does not help cooling which tells me the 2 engine compartment side vents are more than adequate to feed the centrifugal cooling fan; so perhaps increasing engine compartment air pressure and reducing relative air temperature would help.

So don't laugh too hard at the pictures (IMG:style_emoticons/default/av-943.gif) It's a first pass attempt.

I did a couple of runs on my normal joy ride and am qualitatively seeing about a 5 to 10 degree head temp reduction and quicker cooling to normal temps after an uphill grade. Also cruising at 65mph in 5th I'm seeing about a 10 degree reduction in steady state temperature. I have a big hole in the back due to a 3D print problem and my duct tape keeps on flying loose so not getting full duct air. I just have a VDO head temp gauge on #3 plug. As many of you know the VDO has 50 degree hash marks; so not real accurate reads.

So is it correct that head temps are not affected by outside air temp, that's an oil temp thing?

Has anyone tried this? The stock grating is still in place. Can I be doing any harm?

I have contemplated the same thing for my T4 powered Notchback. Low pressure zone behind the rear window is the location for the air inlets. Think 70's F1 for inspiration (IMG:style_emoticons/default/smile.gif)

[Shivers]

Seems to have good air flow on the rocker and they come in fiberglass. Could pick up some cool air with a scoop and think brake cooling ducts. That size from each side would bring in some air with out over pressurizing the engine bay. (someone mentioned fan issues) Maybe like this: Red is exposed, blue is inside with start collar and orange is the flex tube to a small collar added to let air into the engine bay. (IMG:style_emoticons/default/confused24.gif)

[Jamie]

Seems to have good air flow on the rocker and they come in fiberglass. Could pick up some cool air with a scoop and think brake cooling ducts. That size from each side would bring in some air with out over pressurizing the engine bay. (someone mentioned fan issues) Maybe like this: Red is exposed, blue is inside with start collar and orange is the flex tube to a small collar added to let air into the engine bay. (IMG:style_emoticons/default/confused24.gif)

Works well on a Cayman!

[Mikey914]

Honestly,
The best cooling is probably obtained by increasing oil quantity. The 72 I bought out of Reno used to carry a canoe on top and drive up to Tahoe. It has an external oil cooler mounted behind the trans axle. Good for 2 more quarts of oil+ cooling.