Air hose from exhaust to intake?

[sgtsandman]

At the throttle plate or wherever there is a drop in pressure (and thus a drop in temperature), ice can build up can happen in temps as high as 70 degrees if the conditions are right. Note the CAN and not WILL. It all depends on a lot of factors, temp, humidity, dew point, etc, etc.

 

[Dirtman]

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.

This was kinda my point. Modern vehicles don't have carbs so it's not needed. Neither my 2000 2.5 of 2009 2.3 have one. And I've never seen one on any new cars. EFI puts the fuel in well past the throttle plate and modern cars are starting to go to direct injection so the fuel never even sees the air outside of the cylinder.

 

[sgtsandman]

It’s port injection.

The the only potential area of concern is the throttle plate in the throttle body then. Both of my Honda CR-Vs (1999 and 2001) and my 1998 Ford Ranger had coolant lines running to the throttle body instead of a hot air valve. My 2011 has neither but the housing is plastic instead of metal. It does have an IAC and the EGR is close, if not right on, the throttle body. So, preheating may not be necessary. I haven't worked on the 2019 enough to say what it has beyond direct injection.

My knowledge is mainly from the operational and mechanic's understanding and point of view. So I may be missing or misunderstanding something. I think what I'm saying is pretty sound but one great thing about this forum, is that someone who knows better, will come along and correct any errors.

 

[RonD]

Again, this is an Emissions device, also helps engine to warm up faster

All gasoline engines need to be Choked on cold start, that means a rich fuel mix and high idle(so they warm up faster)
Doesn't matter if its a carb, port injection or direct injection, cold gasoline doesn't ignite easily, it needs to be a vapor, 30% vapor to get good ignition from a spark plug
Compression heats it up but not enough if the gasoline is cold, if gasoline in the fuel rail is 10% vapor when released in cold engine then choke adds 3 times more gasoline to get the 30% needed for engine to fire
If incoming air is warm then less Choke can be used, as gasoline vapor % increases

So Choking causes higher emissions AND Cats are cold so double whammy on pollution

Best way to lower emissions is to get engine up above 140degF(coolant temp) ASAP
This warms up gasoline in the fuel rail and allows computer to go into Closed Loop sooner, least pollution
Its all about the heat and the vapor % of gasoline

 

[Chapap]

Does egr have anything to do with heating intake air, or is it solely to reduce combustion temp?

 

[Roert42]

I don't think it does either. The EGR shouldn't open until the engine is warmed up, and only when running at certain rpms/throttle position. I assume hot exhaust gas is not going to have a cooling effect on the engine cylinder. Purely to reduce emissions.

 

[Dirtman]

I assume hot exhaust gas is not going to have a cooling effect on the engine cylinder. Purely to reduce emissions.

That's how it reduces emissions, by lowering cylinder temps.

 

[Chapap]

I don't think it does either. The EGR shouldn't open until the engine is warmed up, and only when running at certain rpms/throttle position. I assume hot exhaust gas is not going to have a cooling effect on the engine cylinder. Purely to reduce emissions.

I was thinking the egr (whenever it’s supposed to kick in) reduces O2, making the burn cooler. Perhaps somewhat mimicking a variable compression type thing

 

[Roert42]

That's how it reduces emissions, by lowering cylinder temps.

I was under the impression that it reduced emissions by cycling unburned fuel back into the engine.

 

[Dirtman]

I was under the impression that it reduced emissions by cycling unburned fuel back into the engine.

It cycles burnt air back into the cylinder which has less oxygen. Less oxygen means the boom boom is lower and therefore cools the cylinder to reduce NOX emissions.

 

[Roert42]

It cycles burnt air back into the cylinder which has less oxygen. Less oxygen means the boom boom is lower and therefore cools the cylinder to reduce NOX emissions.

 

[Chapap]

I was under the impression that it reduced emissions by cycling unburned fuel back into the engine.

I’ve read that that’s a complete myth. I do know that the more modern you get in car design, you get dual acting and triple acting cats. The more advanced ones need super specific exhaust makeups. It basically has to be lean and rich at the same time and some other things. Egr has a lot to do with that. That’s why I wonder if my old system that doesn’t even have a downstream O2 sensor really does much.

 

[RonD]

NOx is a toxic gas produced in engines when cylinder temps get high

When you accelerate or cruise along at highway speeds, computer has to run a Richer fuel mix, this burns faster and hotter, i.e. when you go up a long grade or haul a heavy load you may notice your dash temp gauge goes up a bit, that's from the Rich fuel mix needed
And the faster and hotter burning causes a spike in NOx

Inserting exhaust gases slows down the faster burning rich fuel mix, so lowers NOx production by lowering cylinder temps, as said
Re-burning the exhaust doesn't make it less polluting, it is what it is, exhaust, the Cats do re-burn it to reduce pollutants

So as said, the EGR system is only active after engine is warmed up and then only used when computer must run a richer faster burning fuel mix, so not used at idle or lower cruising speeds

 

[Dirtman]

I’ve read that that’s a complete myth. I do know that the more modern you get in car design, you get dual acting and triple acting cats. The more advanced ones need super specific exhaust makeups. It basically has to be lean and rich at the same time and some other things. Egr has a lot to do with that. That’s why I wonder if my old system that doesn’t even have a downstream O2 sensor really does much.

Yes it still does plenty. The downstream O2 sensor was required in OBD2 to see if the catalytic converter is doing its job. Basically just a warning system to replace the cat. More modern cars have used the downstream O2 sensor Input to fine tune the fuel trims but that's neither here nor there... The EGR is a separate system from this designed to perform a different task. EGR cools the cylinder, Cats burn up anything leaving the cylinder.

 

[rubydist]

The tube that directs warm air off the exhaust manifold into the carb has nothing to do with emissions. It is purely there to prevent carb icing. When I lived in MN (where it seems its below 40F half the year) if that device was not working properly, the throttle plate would ice up and the engine would not idle. So, you come to a traffic light and the engine dies. When I fixed that, then the throttle icing magically went away. Many vehicles had that type of intake air warming system long before the feds started worrying about emissions.