TPH Required?

[RRoller123]

I am thinking of removing my Throttle Plate heater. The only real reason being that it slightly hits the underside of the hood and causes damage to the hood lining. The engine sits that close up top. It would simplify the configuration under there too, which is a slight added benefit. The hoses could be rerouted and used with a quick fill T for the cooling system.

So the big question is, do I really need this in Massachusetts? I drive in very cold weather here, (up until the first day that the roads get salted, typically November, but this has not happened yet this year), and very hot, humid weather in the Summer.

Second question, but secondary: Since we spend a lot of time trying to get cold air to the Intake Plenum, isn't the TPH counterproductive in this regard? It heats up the TP tremendously, to the point that it can't be touched after the car is warmed up. Doesn't make sense from a performance standpoint to have this. Is the risk of condensation inside the TP that high that we need this device?

Oh, and Happy New Year to all of us out there in forum land!! Couldn't survive without this great place!

Pete

[spider2081]

To see if it effects the cold performance you could connect the hoses together bypassing the heater,
I removed the throttle body on my 81 and installed on from an 80 with out the heater casting. I can't say I notice a difference. I just don't know what the coldest temp is I have driven in. Pretty sure its in the high 30's though.

[BEEK]

the tph was designed to thaw a frozen throttle plate. where condensation could freeze and stick the throttle plate closed after sitting over night. I have never seen this happen. But manufacturer testing obviously showed them that it was a possibility. The early EFI cars had a grey metal one that looked like it was an add on opposed to the later type which was cast into the housing and used 4 bolts/nuts to secure it

[So Cal Mark]

frozen throttle plate? Reality is that during warmup, intake icing can occur. I've never seen it on an FI car but I've experienced it on a carbed vehicle here in sunny So Cal. Every car produced with FI had coolant routed through the throttle housing. Warming the intake air helps driveability and lowers emissions substantially especially during warmup. Automakers have always struggled to lower emissions prior to the engine getting to operating temperature. Emission testing on new vehicles starts the minute the engine is started, so warmup is a critical time to reduce emissions

[bobplyler]

Reality is that during warmup, intake icing can occur.

It can occur when there is high vacuum (which causes cooling of the incoming air), and high humidity. That's why
small airplanes with carbs have carb heaters. When descending, the throttle is backed WAY off, and
under high humidity, ice can form in the carb. Not a good situation.

[RRoller123]

"frozen throttle plate? Reality is that during warmup, intake icing can occur. I've never seen it on an FI car but I've experienced it on a carbed vehicle here in sunny So Cal. Every car produced with FI had coolant routed through the throttle housing. Warming the intake air helps driveability and lowers emissions substantially especially during warmup. Automakers have always struggled to lower emissions prior to the engine getting to operating temperature. Emission testing on new vehicles starts the minute the engine is started, so warmup is a critical time to reduce emissions"

But during warmup, the TPH is cold, just like the coolant. It doesn't heat up any faster than the coolant and the rest of the engine heats up, since there is no secondary source of power to heat it (like there is with the AAV). So this explanation doesn't make sense to me. And once the engine is warm, we all are seemingly always trying to get cold air into the Intake, ducting it from the front of the car, etc. So basically this little gadget works against that.

[RRoller123]

This is taken directly from Wiki on Carb Heat: (generally supports the idea that the TPH is not needed on a multi-injector FI engine.)

Operation

Icing occurs when the atmospheric air contains significant levels of water vapor; as the air is drawn into the engine through a carburetor it is cooled sufficiently to cause that vapor to condense out and freeze on the butterfly valve. This cooling has two causes: the air pressure drops due to the expansion caused by engine suction and the increase in speed through the butterfly valve (in part-throttle operation) which drops the air temperature; and the liquid gasoline being introduced into the airstream must evaporate, and the heat of evaporation is extracted from the airstream, cooling it. The temperature in the carburetor can drop below the freezing point of water, and if the air is humid, ice can form inside the carburetor. As the ice builds up, less air can pass through the carburetor, causing a drop in power and, in severe cases, the engine will eventually stall.

Temperature drops of 20°C (36°F) or more are often encountered within the carburetor, so ice can build up even when the outside air temperature is well above freezing. Perhaps surprisingly, cold winter weather is less prone to icing, since cold air contains much less moisture. A warm day with high humidity is considered the most likely scenario for carburetor icing. Since there is less air acceleration through the carburetor at full-throttle operation, icing is usually not a problem then.

Carburetor heat uses hot air drawn from the heat exchanger or heat stove (a metal plate around the exhaust manifold) to raise the temperature in the venturi section high enough to prevent or remove any ice buildup. Because hot air is less dense than cold air, engine power will drop when carburetor heat is used.

Engines equipped with fuel injection do not require carb heat as they are not as prone to icing - the gasoline is injected as a steady stream just upstream of the intake valve, so evaporation occurs as the fuel/air mixture is being drawn into the cylinder, where metal temperatures are higher. The exception is monopoint or TBI injection systems which spray fuel onto the throttle plate.

Some multipoint injection engines route engine coolant through the throttle body to prevent ice buildup during prolonged idling. This prevents ice from forming around the throttle plate but does not draw large amounts of hot air into the engine as carburetor heat does.

[BEEK]

actually mark that is exactly why they were added. i went to all the factory training classes in Jacksonville when i was employed by FIAT back in the day. The instructor explained the entire process as well as the warranty campaign where we had to retrofit cars that did not come with those parts from the factory. Hence the bolted on grey units versus the cast in parts. That was the reason for the retrofit. i am not arguing the intake temperatures and icing in the intake etc. just why FIAT did it. or at least thats how the factory explained it to us.

[RRoller123]

Just for historical reference, my FI car was mfg 01-80, and has the early "prototype" TPH, in brass formed plate (not cast), all soldered seams. Was probably grey at one point. I painted it black after repairing a seam leak last year. I am of the mind to remove it, but will give it some more thought. It is a potential point of recurrent failure, especially since the seams are soldered.

Pete

[DieselSpider]

Found it more of a necessity at higher elevations when driving in the White Mountains in the Fall when it was damp out such as early morning and in the evening. Cars would choke out and you'd find the intakes filled with frost. The heat plenum from the exhaust manifold takes care of that on most cars along with the routing of coolant around the throttle body. The plenum systems really only come into play when its cold out on a well designed system and go into bypass mode when its warm so I would hope a well thought out electric heater would have a thermostat on it to shut it down when not needed.

There was a time when they would install cone shaped screens below the throttle plates to enhance fuel economy by better atomization of the fuel charge on carbureted engines and those would make intake icing much worse.

[RRoller123]

Diesel: The experience that you describe of iced up intakes after driving early morning/late evening, high elevation, etc. in the White Mountains; Was that in a carbureted car or FI car?

Pete

[DieselSpider]

Diesel: The experience that you describe of iced up intakes after driving early morning/late evening, high elevation, etc. in the White Mountains; Was that in a carbureted car or FI car?

Pete

Both but mostly when the preheat tube from the exhaust manifold was broken or had been removed to install headers, custom air intake, etc.

[timinator]

The engine runs best at very near the same combustion A/F, hot or cold. The fuel must be in vapor form to burn. The confusion over "needs to be richer when it is cold" is because when the engine is cold a larger mass quantity of fuel is required because only a small percentage of the total mass can evaporate in the small time between the fuel entering the intake manifold and the combustion event.

At some particular temperature the cold engine may require 200% mass quantity of fuel as the hot engine because only 50% evaporates in the time available between injection (or discharging from the carb) and combustion. The remaining 50% passes through unburned. Of course, the percentage of liquid fuel which evaporates varies with the temperature.

Adding heat at the throttle plate and adjusting mixture with the ECU works at all ambient temperature. I agree with Mark that emissions are the first concern of all car manufacturers. If it does something for icing all the better.