Engine air intake locations Options

[Charles Freeborn]

My car has a downdraft fan and lowered roofline that AJRS was building in the 9o's.
When I installed a CHT I realized that it needed more airflow to the cooling fan. Methinks I'll add some scoop(s) to the equation to see if I can get the head temps down.
So, location, location, location. Three images below. Where will the optimum pickup location be? I've seen a webpage done by a professor who used his AX 914 as a model and did some computer and water tank tests, but I can't read the squiggly lines well enough to tell where the best place to locate scoop(s) is. What I've come up with so far:
Store bought scoops - of the kind one sees on hoods. Kinda cute, fiberglasss, would punch 4" holes through the sail panels, move other stuff out of the way and plumb to a plenum that seals to the top of the fan housing.


Build a lexan scoop / plenum (clear so I can see through it with rearview) and catch the airflow at the trailing edge of the roof. Opening would be roughly 2.5" x 12" to match fan opening (11" round fan)


Build a lexan scoop / plenum that catches air at the leading edge of the roof, would probably run through the interior of the car and out through the rear window opening. This seems the most obtrusive to the driver ergonomics, distraction, etc.



I suppose one more option would be to do a sort of hybrid of the two roof top collectors and have it punch down through the roof just in front of the rear hoop. I've seen one (also an AJRS car) done that way. It too had the raked windshield and lowered roofline as mine does.

What say ye? where is the optimal pressure on a 914?

BTW, I've worked with plenty of Lexan, have all the tools, so fab isn't an issue.

Thanks.

[brant]

Ajrs built at least 6!pr more with the lexan scoop in the roof. Through the rear window. It worked well

[Charles Freeborn]

Ajrs built at least 6!pr more with the lexan scoop in the roof. Through the rear window. It worked well

I've only seen a sort of vague photo of one (Yellow car) that was outfitted with one. Any idea where one could get a better look?

[URY914]

You can see the scope here.

[stownsen914]

The farther forward on the car you put a scoop, the better. Especially on a no-so-aerodynamic car like a 914, air gets dirtier as it passes over the car and gets harder to capture unless the scoop protrudes above the car (to poke through the air boundary layer).

Another idea - headlight bucket to a tube that runs through the cockpit. More work, but may be more likely to be vintage legal (SCCA allowed this from the 1980s or so I believe).

I have a front hood NACA similar to the above on my 914, but I stuck it right in the middle of the hood. Very effective. I run at CHT and can quickly see a 50-75 degree temp increase on cool down laps once I slow from cooldown laps speed to paddock speed. I assume due to the scoop. (On a 911 motor.) Pic below. Note the intake scoop over the engine bay area. I don't have a good way to measure the effectiveness of that one, but I have to imagine it gets cool air to the engine. None of this is likely vintage legal though.

[Charles Freeborn]

Many thanks all. The #13 pics are heartbreaking. Hopefully it was resurrected. That is a different car than the one I saw - and the over-the-roof scoop would be fine for my local club racing (ICSCC) and maybe the local vintage (SOVREN) but probably not the others (SCCA & SVRA). I'm not terribly worried about that just yet - this and probably next year will primarily be ICSCC.
The yellow car I was referring to is this one:
(IMG:http://www.914world.com/bbs2/uploads/post-47-1517426922.jpg)

This arrangement would probably get past the vintage tech purists (?) and in a pinch could be arranged such that the car could still be run with the roof off. I should probably say right here I have no delusions of podium glory. I'm strictly in this for fun so chasing hundredths of a second are not my goal.

The current headlight buckets are removed and have intakes for cabin air. I'm not crazy about that install so I'd gladly re-work. Ducting would be interesting, but do-able. I'm more inclined to stick to some sort of roof or sail panel scoops. I'll continue to ponder and when I do mock something up I'll post here for comments.

My last thought is that the current Spal fan is rated at around 1000CFM. There is another fan of the same diameter that pulls 1300 so that could net a 30% increase right there. Not sure if it would fit the housing, but as I said, I'm not afraid of fab work.
Many thanks again.

[Jake Raby]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.


This post has been edited by Jake Raby: May 23 2021, 03:44 PM

[Charles Freeborn]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.

Yeah, not helping. This discussion is about intake design and placement.

[Jake Raby]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.

Yeah, not helping. This discussion is about intake design and placement.

Looks like your design is targeting forced air into the engine bay, which would increase those pressures that we conversed about.

I'd consider the old SCCA Production class trick that we referred to as "the stove pipe". We used it in FP with a stock cooling system with great results, some of the stock fans only had 8 impeller blades left in place, forced air did the rest from the left front headlight bucket area, through the cabin, and into the firewall. We were tempted to try running no fan at all, but never did.

The only time I have made the electric fan work was in AX on a Supervee, and once running M1 alcohol.

[SirAndy]

I'd consider the old SCCA Production class trick that we referred to as "the stove pipe". We used it in FP with a stock cooling system with great results, some of the stock fans only had 8 impeller blades left in place, forced air did the rest from the left front headlight bucket area, through the cabin, and into the firewall.

Rich Bontempi's FP 914 has the same "stove pipe" setup, from the front through the cabin and firewall and straight into the cooling fan.
(IMG:style_emoticons/default/driving.gif)

[GregAmy]

That was a common mod for Prod 914s when they were ppular (re: competitive).

@ChrisFoley

[Jake Raby]

That was a common mod for Prod 914s when they were ppular (re: competitive).

@ChrisFoley

At some point when racing these cars you finally understand that the faster the car goes, the more load the engine sees, and the higher the demand for airflow is. At some point the carbs start fighting the cooling fan for air, especially if you are making real power.

The stovepipe trick is a great way to partition cooling system air from inlet air, solving a lot of these problems.

[Charles Freeborn]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.

Yeah, not helping. This discussion is about intake design and placement.

Looks like your design is targeting forced air into the engine bay,

The only time I have made the electric fan work was in AX on a Supervee, and once running M1 alcohol.

Wrong again. First paragraph of my first post. "plumb to a plenum that seals to the top of the fan housing". Yes, I know, it will have to have some resilience to allow for engine movement and vibration.

So far, of all the designs I've seen the roof top solution on #19 is the most elegant and least likely to attract the attention of scruitineers. I'll work that one up a bit.
As for classes yes, probably FP (or here it's FIP - improved production as my interior is stripped out), possibly VP1 and with ICSCC here in the Northwest there is a SPU class that is for 2.0 and under cars and has little to no restrictions. I haven't read the fine print of the rules but simply put you bring a dyno sheet, they weigh the car and handicap accordingly. It's a pretty fun class. There's a MR2 a pal of mine runs that is downright ingenious in many ways. The only problem is they often group (depending on field size) with SPO which goes all the way up to ground pounders. When you're in an 1800 lb car and a 600+ hp V8 goes by you kinda come to jesus, or whomever you beg mercy.. but I digress..

[ChrisFoley]

Something like this is extremely effective and, if done properly, is perfectly legal in SCCA and in vintage.

[Charles Freeborn]

[quote name='ChrisFoley' date='May 24 2021, 10:18 AM' post='2918182']
Something like this is extremely effective and, if done properly, is perfectly legal in SCCA and in vintage.

Yep, that would give it a nice cool gulp of air. I am planning to use those lower light openings as air intake (currently blocked), but was going to split between brake cooling and cabin air. I was planning on installing LED lights in the same location as the original headlights, but the use of those will be so minimal they could be in the turn signal spaces and continue to use headlight openings for cabin air. That would free up the lower light opening space.
Currently my brake duct intake is molded into the front splitter, but for vintage that will probably have to go, so utilizing existing openings is going to be the order of the day.

I'll have to snap some pics - recovering from a surgery at the moment so mobility impaired for another week or so.

PS, Chris, I desperately want one of your cable throttle systems. Just need to find the scratch. Care to trade anything?

[ChrisFoley]

PS, Chris, I desperately want one of your cable throttle systems. Just need to find the scratch. Care to trade anything?

There's only one thing I'm interested in trading for these days - aged Bordeaux. (IMG:style_emoticons/default/biggrin.gif)

[Charles Freeborn]

PS, Chris, I desperately want one of your cable throttle systems. Just need to find the scratch. Care to trade anything?

There's only one thing I'm interested in trading for these days - aged Bordeaux. (IMG:style_emoticons/default/biggrin.gif)

Mmmmm Bordeaux.... I have family with a house in that region of France. Mornac-Sur-Seudre. Gorgeous country and fabulous wines. If you can find it try a Pineau aperitif some time. Nectar of the gods. Don't have any of that to trade but I could make a nice case to hold it. I've also built some wine racks, including one that emulates the Eiffel Tower.

[URY914]

You gotta get it up in the clean air. (IMG:style_emoticons/default/biggrin.gif)

[stownsen914]

One thing to consider as you design your intake / scoop is that it's very difficult to get a true ram air effect with a scoop. Most of the power you get from an intake scoop is because you're getting cool air to the engine intake. Cool air makes measurably more power than the hot air the engine would otherwise be sucking in. You may do just as well feeding a good supply of cool air to the engine bay via the headlight / stove pipe arrangement. And let the fan and intake sort out how much air they need.

[914 Ranch]

My interest in this intake is cold Air. It's pretty far in left field and I have no idea if it will have any ram effect. Oh and I didn't want to make a hole in the targa bar.