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Discussion Starter #1 (Edited)
So this weekend I went to clean my IAC Valve/Throttle Body. Unfortunately I wasn't able to do it in the morning so I went to lunch and when I came back the darn thing was so hot I couldn't barely touch it without burning my finger. How would it ever be possible to get cool air into the engine with this thing so damn hot... It's like a big heat sink. That got me wondering why it got so hot int he first place. Could it be that it's just a very hot engine bay? I mean the engine cover was just as hot!

Anyway, I noticed two hoses going from the engine coolant outlet to the throttle body. Why is this? (yes I am a noob!) It turns out the coolant is meant to warm the throttle body so they don't freeze over during winters. Well, for those such as myself living in a region with a warm climate year round, it's overkill. I found some forum posts on the RAV4 forum that you can safely bypass the coolant. And so I did. It was very easy and took about 5 minutes to do with a 3/8-3/8 union fitting I picked up at Home Depot for $2.65.

Anyway, before I installed it needed a baseline measurement, and after a 30 minute drive the throttle body was just over 150 degrees (151 °F to be precise, measured right at the top of the throttle body using an infrared tool about an inch away.)

Below is my install photo. The only problem I ran into was a little bit of antifreeze got on my hand. But nothing really squirted out, I made sure to pull off the hoses nice and slow while pulling it off with the hose pointed the hose upward. No need to pinch the hoses or anything. As soon as air enters the hose it flows back down into the engine.



I literally just got to work just now (after a 30 minute drive), and took a measurement -- 107°F. That's a 44 degree difference! The throttle body was only luke warm to the touch. NICE!!!

I haven't felt the difference yet but I've only commuted once with the car.. I believe the real payoff will be there as I know coolant temps can reach upwards of 200°F. And with this hack, your throttle body will still be luke warm.


Anyway this is a great little hack I thought I would share with you guys.
 

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Good job, Scott!

I presume this is easier to work on with the radium CAI, since the stock airbox blocks off most of the area? Sorry bro...haven't had time to look into my evora engine bay area.
 

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Good info. The Elise/Exige have this same "water cooled" throttle body. I wondered why it was there. No I wonder if I can just cap off ports coming from the head... hmm..
 

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Discussion Starter #5
Good job, Scott!

I presume this is easier to work on with the radium CAI, since the stock airbox blocks off most of the area? Sorry bro...haven't had time to look into my evora engine bay area.
I'm pretty sure the stock air box won't prohibit you from reaching these hoses, as they are off to the side.
 

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Discussion Starter #6 (Edited)
Good info. The Elise/Exige have this same "water cooled" throttle body. I wondered why it was there. No I wonder if I can just cap off ports coming from the head... hmm..
I thought about this also. I'm pretty sure the coolant flow is passive however I played it safe and just did it the way others did it. Joining the hoses is easier to reach right up top anyway.

@Doug--thanks for the tip, I thought about this also. I don't have any caps lying around, so a bit of duck tape will have to do until I pick up a pair.
 

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Don't get too excited about feeling a difference. The intake air passes over some other warm things before it gets to the combustion chamber. :)

At 4000rpm, 100 liters of air are passing through that TB every second. Any air temperature increase from the coolant circulating through will be vanishingly small.

What about the hp increase from my CAI, you ask? Well, in my opinion, "cold-air intake" is something of a misnomer. The benefits you get from that item have a lot more to do with removing restrictions (intake tube muffling, curves in the intake, and of course filtration) than with the temperature of the air.

Just my two cents.
 

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...but if the EPA thinks it is necessary to reduce emissions...I would think the temp increase is significant.

I'm interested. Do other makes have the same fix?

Checking around, this same mod is debated on the LS1 forums, et al.

There seem to be observably cooler engine bay temperatures, if not hp gains.
 

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...but if the EPA thinks it is necessary to reduce emissions...I would think the temp increase is significant.
"Carburetor icing" is not something that goes on a gearhead's birthday cake. :) A heated TB has nothing to do with emissions. Get a humid 40-degree morning and you'll find out what it's for.

Do some math on the heat transfer, you'll see that the temp increase can't be significant. And make sure your math is not as sloppy as mine-- I was calculating for a 3ltr engine, whoopsie.

Not trying to make a big deal out of it, honest. Just saying, don't go expecting any hp gains from this, except the placebo kind. (Which are good enough for me, so I'm happy with my Larini.)
 

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Thanks Scott for the writeup - I will be doing this mod myself soon. However, like WoH said, methinks it won't make any kind of noticeable difference. I thermal wrapped my Radium tubing and thermal block plate for the hell of it - not expecting any consistent drop in IAT's. I was right - no appreciable drop, but, like this, it was a cheap project. And, most importantly, I can add it to my
mod list :D
 

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I think the coolant goes throttle body for precise idle control during warm up. It's like automatic choke, when the engine cold the ecu open up throttle butterfly to allow rpm a little higher and prevent stall.

But if you bypassed it, and no problem starting engine in the am, you must be the lucky Californian :)
 

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Am I the only one confused on how this could have anything to do with helping idle or emissions when the engine is cold?

If the engine is cold, so is the coolant, and this would benefit nothing. To me, the idea of it helping emissions of a hot engine on a cold day makes more sense. The coolant would heat the intake air causing a more efficient combustion and helping emissions.

...but that's just me thinking thoughts.
 

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The auto industry is spending lots of money trying to figure out how to get you motor up to operating temp as QUICK as possible. This is just one link in the chain.

Its not a new idea. My 73 Datsun 260Z had the same thing. Datsun routed coolant through the twin Hitachi SU carbs.
 

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Discussion Starter #16
It's not surprising this is generating lots of opinions. Nonetheless I welcome intelligent discussion :)

Here is some additional perspective...While perhaps a very hot throttle body might not have a significant direct impact to the temperature of the air passing through it, I would assert that the elimination the heat sink effect can indeed result in cooler intake air, given a significant portion of that air is being pulled from the engine bay (given how small the compartment is, and how small the side vent is). At high RPMs, MASSIVE amounts of air is required and most certainly not all of it is coming in from the tiny side vent (which is why they have to add scoops on motorsports versions of our cars). And with the heat shield compartmentalizing the air around the intake filter to just 1/4th of the overall space in the engine bay, a vacuum is created and subsequently air is pulled through the gaps in the heat shield. Less hot air in the engine bay compartment=cooler intake air. BTW, it so happens the least least restrictive gap in the heat shield happens to be right where the CAI routes through, and next to it is that is throttle body.

Anyway what would be really interesting to see are some actually measurements of air temps rather than just theories like the one I presented. I think this data is readily available via the ODB-II interface.
 

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intake temps

intake temps are available in real time. a simple solution for those with iPhones is to install the Go Point app (GoPoint app | GoPoint), pair the supplied bluetooth obdII port scanner to the phone and select the readouts.

the topic is of interest to me as i've installed the radium on an S. however, i had trouble with the heat shield and could not use it....my temporary solution was to reinstall the factory air intake tubing and bend it around so it points toward the rear bumper. i then fitted the K&N cone filter into that tubing, for a sort of poor mans 1964 Ford Fairlane Thunderbolt ram air effect. the car is in storage at the moment, but will get readings at some point. on a supercharged car, the intake temp is of additional interest. while i can appreciate vertical clearance probably precluded the integrated IC option for the Harrop, i've wondered if a small Snow methanol injection wouldn't be a good idea for these cars, particularly in warm climates.
 

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Didn't anybody see the word "icing". This helps avoid that from happening in the winter. This "mod" is silly at best folks.
 

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Sure it's silly, but so is owning a tiny plastic and aluminum car. I think a greater (though still miniscule) advantage is to pull the hoses out and cap the ports. Adding 2-3 lbs of lightness through removing the hose and extra coolant. Cost per pound, that's a better investment that most mods people do.
 

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I have iced up Del'Orto carbs in Houston. All it takes is cool (not cold) humid air.
 
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