Cold air intake

hmmm...my '79 has the rain tray removed & replaced with expanded aluminum (mesh) & I think the original intent was just that draft...from under the car & OUT of the engine cover
 
Sorry to Mike if this is getting off topic, but it is related.

Chris, I had the same thought...let the hot air escape upward. After all, hot air rises. So at a stand-still it will travel upward out the engine cover. But when the car is moving there might be other air-flow factors at play, as I'll suggest.

I'm wondering if the area above the engine lid might not be as much of a low-pressure "draw" as we think (when the car is moving). It stands to reason (and has been demonstrated several ways) that the air spirals as it crosses over the top, creating a counter-rotation from back-to-front over the engine lid. One example of this has been found if the lid's latch is left undone the lid will lift, suggesting a 'low pressure' draw. However it might just be the reversed direction of air flow pushing the lid up, not low pressure sucking it up. Could the circulating air above the lid actually create a high pressure area?

One reason I ask the question is Carl's comment above; when the dizzy access cover was left off there was significant air pressure pushing into the cockpit. If the area above the engine lid was a low-pressure one, then you would think air will be sucked from the cockpit back into the engine bay.

Another possible example is the lack of cool air (from above the lid) going into Mike's cold-air intake. This indicated that the hot air in the engine bay was not being drawn up and out (as a low-pressure above would do), but allowed to remain pushed inside. If there is a moderate high-pressure above the engine bay, and a moderate high-pressure below the bay (coming from the under-carriage and/or the side ducts), then the hot air in the bay would remain stagnant and trapped. This would explain the lack of success with several attempts to cool the engine bay through various methods.

I don't recall anyone actually testing this directly, by measuring the air pressure above the engine lid and/or below the engine bay. For that matter, although its been demonstrated the air moves from back-to-front above it, I'm not sure we've proven that the direction of air flow goes from bottom-to-top or vice-versa (when the car is moving). The speed of travel will have a significant impact on this. So the air moving from bottom-to-top when the car is stopped (as Huss found with his heat-soak and vent fan) could be the quite different of when the car is moving; and the speed where that direction of air movement changes (if it does) could make a difference. It may change directions several times at various speeds. This could cause very different results depending on the typical use of the car (typical traveling speeds).
 
View attachment 11768 Didn’t work. Appearently the hood sucks more air then fresh air blows in.

Since it seems pertinent to this thread, I will offer my evaluations derived from the info I have from airflow studies I have done on similar cars, including my Mk1 MR2, which is very similar to the X1/9.

The X1/9's designers followed period established practices for the X1/9's aero management. Air flowing into the front radiator exits underneath the front end (quite obviously). This is standard practice for most front mounted radiators regardless of engine location. For most any front engine design the air passes through the grill and radiator and is exhausted under the front end. This creates a high pressure area under the front suspension which increases with speed. Redirecting the remaining air over or around the front by the use of an air-dam improves radiator flow by reducing the additional airflow under the car. Newer designs, like the 997+ generation Porsche 911s vent the front radiators through either the front wheelwells or through the hood, or both in the case of the 911. This has great effect on front downforce by eliminating most of the high pressure under the front axle and is why the FAZA cars (and many since) exhaust the radiator through the hood.

Its important to note that Fiat included a number of panels to close off the underside of the engine compartment from the road below. This is contrary to front engine layouts where airflow through the radiator is exhausted out the bottom of the engine bay. The panels blocking off the airflow was done to reduce the air from being drawn from under the car up through the engine compartment and exhausted through the engine lid. For the X, the vertical rear window creates a low pressure zone over the engine cover as air flowing over the roof creates a void there. The vented engine cover then exhausts the air flow into the engine compartment via the vented lid. The primary source of airflow into the engine compartment is through the side scoops. The purpose is to provide fresh clean air instead of hot dirty air from under the car.

In reference to the quoted text above, any attempt to draw air through the engine lid only recycles the air from the engine compartment back into the intake as the heated engine compartment air tumbles between the engine compartment and the flow over the roof. Given that, the only source of fresh clean air is from the side scoops. Exactly where the FI system's OE canister intake is located.

When developing my '80 model DSP racecar I tried several version of a cold air intake. I data logged the intake air temp and found that none of my attempts were very productive. I did build an airbox that sealed the intake trumpets to a feed from the side scoop but the restriction was such that there was no net gain and I removed it.

The FAZA style snorkel is the simplest source of cold air for the engine intake but requires it be plumbed directly into the intake.

I too have noticed the significant flow of hot air from through the distributor panel into the cockpit. Its pretty standard that the cockpit has a lower pressure than the airflow around it. Therefore its more likely the air from the distributor panel is due to the lower pressure in the cockpit than any excessively high pressure in the engine bay.
 
Great info Steve. One thing I had not considered was that all of the 'splash' guards/air panels under both of my X's were removed prior to my ownership. So I was considering the bottom to be open.

The pressure above the lid does not seem to be a big enough gradient from the pressure within the bay to make much difference in air movement (as Huss demonstrated). So it seems doing something to alter those pressures would help.
Given the restrictive amount of air available from the side ducts, it seems there isn't a lot of movement up and out of the bay through the lid. In another thread we discussed opening up the passageways and enlarging the side scoops to facilitate more air flow into the bay, from the sides. This might be one of the better modifications to make.

Have you played with the idea of opening up the panel between the engine bay and the trunk, as well as the rear panel to vent hot air out the back?
 
Great info Steve. One thing I had not considered was that all of the 'splash' guards/air panels under both of my X's were removed prior to my ownership. So I was considering the bottom to be open.

The pressure above the lid does not seem to be a big enough gradient from the pressure within the bay to make much difference in air movement (as Huss demonstrated). So it seems doing something to alter those pressures would help.
Given the restrictive amount of air available from the side ducts, it seems there isn't a lot of movement up and out of the bay through the lid. In another thread we discussed opening up the passageways and enlarging the side scoops to facilitate more air flow into the bay, from the sides. This might be one of the better modifications to make.

Have you played with the idea of opening up the panel between the engine bay and the trunk, as well as the rear panel to vent hot air out the back?
I once made a scoup under the car to direct more air from under the car into the motorcompartment made a huge difference for the temperature for as long as you’re moving. Although the air has (partly) past the rad, it must be much cooler than the air in the compartment itself. dustier also. I have the impression that the sidescoups hardly work. This weekend i will do some temperature measuring in different places.
 
The low pressure area above the engine cover is intended to draw air through the engine lid vents. Removing the rain tray would improve flow and because a lower engine bay pressure would help draw air in through the side vents that would help overall. On more than one road racing car I have cut away any restrictions in the side vents.

Have you played with the idea of opening up the panel between the engine bay and the trunk, as well as the rear panel to vent hot air out the back?

Remember, air flows from areas of high pressure to low pressure. So removing the rear bulkhead would only improve evacuating the hot engine compartment if doing so provided a path to a lower pressure area. This is why many rear or mid engine cars have a vented rear bodywork. The area immediately behind the car is an area of low pressure and venting it directly through the rear panel (the area of the license plate between the tail lights) would do that. Simply opening the engine bay to the rear truck doesn't provide a flow path.

I did help a friend build a very interesting X1/9 that had the entire rear (taillight) panel vented. We also removed the rear engine compartment fire wall and the rear trunk floor. You could stand behind the car and see the header through the venting. It worked really well. Especially with the rather large rear spoiler that was fitted. If the car hit a patch of dust you could see it flow right out through the vents and up behind the rear spoiler.
 
if I'm reading all that correctly (which I may not be, since i'm multi-tasking), my '79 might be a hot mess of thermodynamic theories being tested, perhaps with a cumulative nil sum. I do have a home-made (light wood w/ epoxy) snorkle I could fit to an engine cover.

EDIT...reading Steve's comment above...maybe slightly less of a hot mess than I thought.
 
I once made a scoup under the car to direct more air from under the car into the motorcompartment made a huge difference for the temperature for as long as you’re moving. Although the air has (partly) past the rad, it must be much cooler than the air in the compartment itself. dustier also. I have the impression that the sidescoups hardly work. This weekend i will do some temperature measuring in different places.

Many years ago, before I had much knowledge of aerodynamics, a friend and I were driving out X1/9s home form a weekend autocross. We were on an interstate highway cruising at probably 65 mph. On the mostly empty highway we traded positions multiple times and I had the chance to watch the behavior of the water spray around the car. The spray from exiting the front tires flowed out of the front fenders and down the side of the car. I could clearly see a significant amount of spray enter the side scoop. It was interesting to watch and I drove along beside the other car observing this.

Looking back it was clear that, at speed, the scoops work quite well. That also fits with the flow studies I did on my Toyota MR2 which has a similar scoop but only on the right side of the car.
 
All very useful information. Albeit overwhelming. What I’m getting is that the best source of “cold air” will flow from the side scoops. Now, the factory box does draw air directly from the side scoop but isn’t “open” like you’d see a typical cone filter “cold air intake” setup. What I’m really after is the sound that you get with the open filter cause let’s face it, the stock engine is no beast and a little bit of extra “cold air” will hardly add hp. Now, mind you, on my other vehicles that I’ve put cold air systems on I’ve noticed increased throttle response....
 
venting it directly through the rear panel (the area of the license plate between the tail lights) would do that
That is what I meant by "open up the rear panel"...the tail-light panel. Same as you described on your friend's X, opening the pathway from the engine bay directly out the rear of the car. This makes a lot of sense. Combine it with opened-up side ducts and you should see significant engine bay temp reduction.
 
What I’m really after is the sound that you get with the open filter
Mike, thanks for reminding us of this...guess we got a bit carried away with air-flow discussions.

Perhaps you could combine the ideas above; use a open air box (to allow the intake sound you desire), and mount it next to the side scoop where it will get the most amount of cooler air. As you say, cool intake air isn't going to give the X a 1000 HP boost, but it will be better than a hot air intake (which would happen with a open air box located within the confinement of the engine bay).
 
Need to look for Hussein’s pic of his cone airfilter hanging out of the side of his car through the vent.
 
Need to look for Hussein’s pic of his cone airfilter hanging out of the side of his car through the vent.

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Just stick a cone filter on the Air flap meter & add a funnel from the side scoop/vent to the underside of the filter & call it a day :D

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It also sounds like the typical rusted out floors in the two rear side pouches (where the jack is on the passenger side) are performing a good source of hot air venting if the rear firewall is removed.
 
you could always tape 2 in long pieces of string on the engine lid and side scoops. With a passenger or Go-Pro you could see how the air effects those strings.
 
That would be the definitive way to determine air flow around the engine compartment. I did this about 15 years ago on one of my Xs but of course don't remember the results and did not write them down.
 
Update! I found a cone filter and fitted it to the intake via the original elbow and some exhaust adapters welded together to step from 2.5” to 3”. Phase 2 will be an upgrade to the piping on the other side.
 

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