Heated throttle Body......Why

[Andrew_Ennis]

if you have read the engine manual then you will know the throttle body is heated off the water system. My question is, why is the throttle body heated??
Heating will heat the inlet air (ok very slightly) as it passes through the throttle body. I can only think that during very cold weather the pressure drop across the plate could cause icing!!! leading to a sticking throttle.
My next thought is the MAT sensor on elanscan seams to indicate the inlet air temp is usually high, arround water temp ie 70°C ish. But this is due to the MAT being metal and couducting the heat from the throttle heating. When got to WOT quickly it takes a few seconds for the MAT to accuratly measure the air temp.
I wonder if this leads to a reduction in performance, as the mixture calculation will use MAT, as well as MAP, Water temp etc.

I think the thottle body for most of the time could be by passed, or connected into the heater matrix circuit, so it is heated during cold weather.

Has anyone bypassed the throttle body heating circuit?

[F1 LOTUS]

I believe Bosch have recently developed a plastic throttle body that does not require heating and reduced intake air temperature was listed as one of the advantages
Given the location of the Elans throttle body I would be a bit surprised if icing ever became an issue and I will probably bypass mine if / when I ever get into tweaking my car.
Related to this I think Dave_M was going to fit an insulating 'spacer' between the head and intake manifold, so he should certainly be looking into not heating the throttle

[Doug]

well you could put a bypass on the throttle body and see if it makes a difference.

maybe it was done for emissions purposes

so then is the warmed throttle body warming or cooling the intake charge is the first thing to know . . .

[Dave M]

Yes, I have bypassed the TB with the coolant lines. I simply ran a piece of hose between the feed/return and capped off the TB openings. I haven't driven in sub-zero temps, but have noticed no difference in the way the engine runs. Since the change was made with the addition of a new turbo, I was never able to isolate any change in power.

And as Brian mentioned, I will also be isolating the intake from the head. I should have pics in a few more weeks when I get my engine back.

[Andrew_Ennis]

I agree that icing will not be an issue. I wonder during the extreme temp testing done during development, it was required in siberia. Hence no use now!!

Also, by closing the throttle body cooling, you will increase the cooling flow to the turbo, now this has to be a good thing to preserve oil condition.

[ESM]

Hhhhmmm take a look at this

[Doug]

Hhhhmmm take a look at this

good, sound reasoning.

[Doc Fizzix]

Ah yes! My favoret subject comes into play again, physics strikes again!

[ESM]

I thought his point about the rate of air and the small size of the throttle body were compelling - not much air temperature increase will occur when the throttle is open wide.

I didn't find the reasoning behind the above ambient icing as convincing. First he says air is being moved in conditions of vacuum (you what?), then he says the air will rob the throttle body of heat - well yes but only down to the temperature of the incoming air. It seems more likely that the cooling that caused the designers concern is simply evaporative cooling from the fuel downstream (see here). In the Elan's engine, being multipoint injected, the injectors are quite a long way off so you wouldn't have thought it would be a big issue. However, there may be a window of conditions where icing could occur without the TB heating.

I wouldn't remove this coolant feed to the throttle body myself without a damn good understanding of why its there and the envelope of conditions where its needed. This goes double when the benefit of its removal appear marginal. It might be very difficult to get the thing to ice up but it only has to happen once.

[Andrew_Ennis]

Alan,
These were my thoughts, you will get some JT (Joules Thomson) effect through the throttle body as you are expanding air from 1bar (atmospheric) to a partial vacuum. But to cause freesing in the spring summer conditions we see in the UK!! This is why i was thinking of possibly putting it on the heater circuit, ie you use the heater in cold weather. I will have to look at my Thermodynamics notes and do some maths.
My main purpose was to improve Turbo cooling rather than a 0.2% power increase.

[ESM]

Oops yes I drifted off your original question a bit there.

I agree the JT effect would induce some cooling, especially at low throttle openings, but after reading the link above where its described as 'insignificant' I thought it probably wasn't a big deal in this situation - I don't have any more evidence to neglect it than that though.. Patching into the heater coolant feed is an interesting idea - I see the coolant flow to the heater matrix is stopped when full cold is selected on the cabin control so it could work. I'm not so clear how this would help with turbo cooling, except that they're both fed from the thermostat housing - do you think it has a significant effect?

[Dave M]

Interesting theory... When I removed mine, it was more for a "clean up the engine bay" effect rather than a desire to gain power. I was already removing the turbo coolant lines (as the T3 is oil cooled), so the others came out, too. Could it be detremental? Reading the above, possibly. Though in years of driving in widely varying conditions, I've never even had a hint of the throttle sticking.

[ESM]

The air temperatures at the intake tend to be reasonable because the turbo does provide warmish air in spite of the charge cooler (I suppose the heated throttle body might be a hang-over from the normally aspirated version of the engine) and the plenum gets pretty hot as well. The only evidence we have to go on is from ElanScan logs and I've not seen any with sub-zero temperatures (or even close) but I haven't specifically logged under conditions where it is likely to occur either.

I feel it is a low risk but since the consequences could be pretty severe I'm reluctant to advise it.

[Dave M]

I'd like to get some sub-zero intake temps. Just think of the power increase!