Air hose from exhaust to intake?

[Chapap]

This all happens before the air filter, so should be before any sensors? Its currently a super shoddy, back yard fix, so I’ll describe what I see and not assume anything. I have a 2” household vacuum cleaner hose coming from the exhaust manifold heat shield and spliced to what looks to be an oem air duct that connects to the intake snorkel between the grill and the air filter. What is this? Also on this section of intake snorkel is what looks to be an oem sensor of some kind that has a vacuum line sized tube coming out of it. I don’t know where this tube terminates. It’s routed up under the air box.

 

[Dirtman]

This all happens before the air filter, so should be before any sensors? Its currently a super shoddy, back yard fix, so I’ll describe what I see and not assume anything. I have a 2” household vacuum cleaner hose coming from the exhaust manifold heat shield and spliced to what looks to be an oem air duct that connects to the intake snorkel between the grill and the air filter. What is this? Also on this section of intake snorkel is what looks to be an oem sensor of some kind that has a vacuum line sized tube coming out of it. I don’t know where this tube terminates. It’s routed up under the air box.

It's the intake air pre-heater system. Feel free to chuck it all in the trash as it's a utterly useless feature for someone in Florida. The vacuum line part is for the solenoid flapper gizmo that opens and closes it to allow the hot exhaust air in.

 

[RonD]

+1 ^^^

Its actually part of the Emission systems so if you have to have inspections keep it intact

Fuel injected Rangers all have Cold Air Intakes(CAI)
There is an air tube from the rad support to the air filter box to pull in cooler air from behind the grill
On the tube is a vacuum controlled valve for the "pre-heater"
On the exhaust manifold are two metal shields bolted together making a "chamber" of sorts around the exhaust manifold
To connect the metal shields and the pre-heater valve a flexible hose is used, it looks like drier duct but made of metal
Google: pre-heater duct

You will see it

The emissions part
A cold engine has higher emissions that a warmed up engine, so the faster an engine warms up the better it can pass emissions testing, all new vehicles have to pass a cold engine idle test

On the top of the air cleaner box is a dual vacuum hose hook up, one hose goes to pre-heater valve, the other hose to the engine(vacuum source)
This dual hose unit is a A/CL BI MET, Air Cleaner Bi-Metallic Valve
Doesn't need power, when its cold the valve is open and when you start the cold engine the pre-heater valve opens a flap and air from around the exhaust manifold is pulled into the air filter box
Warm air within 20-30seconds
This warmer air will allow engine to warm up faster, the colder it is outside the faster the engine will warm up, so it can cut warm up time by 5 minutes if outside temp is 40degF
This warmer air also heats up the A/CL BI MET valve so it will close and engine goes back to using the Cold Air Intake for better power

Yes, in Florida its probably not a big deal to want the heater working ASAP, but as you go farther North the faster the engine heats up the better


These pre-heaters are kind of hidden away with fuel injection
With carburetors they were "in your face" ducts, lol
And yes people in the south often never put them back on if they were remove to do work on the engine
picture here: https://shop.broncograveyard.com/images/carb_preheater_hose_5.jpg

You see the duct and the A/CL BI MET valve

 

[Dirtman]

I always question how much they actually really accomplished in the first place considering car makers have long since abandoned the whole idea even in colder climates.

 

[RonD]

Haven't looked that close at 2018+ engines but they still have to pass cold start emissions tests
The above system actually worked quite well and was cheap and simple
No electrical parts and uses waste heat

On turbo engines you get instant heat from the compression of the air, on N/A they would have to have something, even electric heaters

 

[Chapap]

Ah very interesting. I know my 94 Explorer and 03 Grand Marquis didn’t have this. I’ve never heard of this either. Seems like I would have run into this system before.

 

[Ranger850]

I had this on my 88 Nissan HB. It definitely worked, but I removed ALL the emissions from that truck along with the "pre-heater". As @Dirtman mentioned, useless in Florida.

 

[rubydist]

I've been in Florida when it was cold enough to freeze throttle plates.

 

[19Walt93]

I always question how much they actually really accomplished in the first place considering car makers have long since abandoned the whole idea even in colder climates.

On carbureted vehicles run in sub zero weather those hot air tubes made a huge difference. If the air cleaner vacuum motor failed or if the tube was missing the car ran like crap. The ice cold air would cause the gas to drop out of suspension in the intake and liquid fuel doesn't burn. A 78-80 Fiesta with a bad vacuum motor wouldn't go 50 mph and the cat would glow red from ingesting gasoline. Not to mention the amount of gasoline that ended up diluting the oil. On a vehicle driven in warm areas the preheater amounts to nothing because the air cleaner temp sensor wouldn't even open the snorkel flapper.

 

[Chapap]

Over the past few years, i was lucky to see frost on the ground during the extreme cold snaps. I’ll get around to messing with this eventually. Might see if the junk yard has the appropriate parts to fix it, but for now I’ll just not look at it. It might even be working a bit.

 

[sgtsandman]

As mentioned above, the preheater helps with fuel suspension and helps prevent carburetor icing in certain situations. Down draft carburetors have less of an issue with this than up draft ones but it can be an issue. Down draft (mounted on top of the engine) has the heat from the engine rising up to keep the carburetor warm but that only comes into effect after the engine gets to a certain temperature. Before that, the pre-heater comes into play. Up draft was not a common thing on vehicles (carburetor under the engine) and is more of an aircraft thing but it has been done. Rangers and Ranger based vehicles never had it.

In any case, it’s probably not critical in FL most of the time but there would be times where keeping it installed and functional would be helpful. Whether you keep it or ditch it would be a personal call.

 

[Chapap]

Also note that I have EFI. It seems most of yall are specifying carbureted… so it’s even less critical?

 

[sgtsandman]

What kind of EFI? If it’s throttle body, the hose might still be needed. Port and direct injection mostly eliminate the need for it. Those two is where you see the IAC and depending on the design, coolant lines running to the throttle body to do the pre-heating instead.

 

[Chapap]

What kind of EFI?

It’s port injection.

 

[Ranger850]

I've been in Florida when it was cold enough to freeze throttle plates.

2018 IDK if it was cold enough to freeze throttle plates, but it does get below freezing temps here from time to time.