What happens in the winter months when you do this?
Common mod in the EVO VIII/IX world. Never made a spit of notable difference performance wise on the butt dyno but common sense says it should work. Though I'm not sure I've ever seen a back to back Dyno or VD graph. Nor has anyone actually measured what the heated coolant through the TB actually = as far as effecting charge temps to my knowledge.
As for winter, In the northeast it gets pretty damn cold and I have never had an issue with coolant lines to TB rerouted in the Evo. No throttle sticking or anything
it does make sense ,but i dont expect anything greater then 3hp to be honest.
Anything you can do to reduce IATs has a positive benefit, regardless of how small it may seem.
This was something done in the world of the Pontiac Grand Prixs too. Both the throttle body and supercharger had engine coolant running through them. When you went with an IC the supercharger coolant passages were blocked but for the Throttle body, we usually blocked it off with a .5" thick throttle body spacer.
What people get confused with is thinking mods like this add performance. They don't. What they really do is give you the performance the car should have had to begin with. You need to understand how your ECM works to understand how these mods benefit you.
Your ECM is constantly reading air temperature to determine how hot the air charge coming into the engine is. If the air charge is too hot, the ECM is going to pull timing to try and prevent detonation...or knock. IF the ECM doesn't pull enough timing and detonation does occur, the knock sensors will pick this up, report it to the ECM, and it will further pull timing. For those that may not know it (and in VERY simple terms), less timing means less performance.
The whole reason we have an intercooler and we get so focused on intake air temps is to try and get those intake temps post turbo as close to the ambient air temperature as we can (since this is as low as you can get with an air to air IC system. Air to water can get lower than ambient when using an icebox but that's not a practical everyday item anyway).
Our coolant temps run at 200 degrees. That is FAR higher than ambient. Having coolant at that temperature running through the throttle body will warm up the throttle body to that temperature and will also allow it to transfer heat to the incoming air charge thus raising it's temperature as well. This is bad.
How bad? On my Grand Prix I was seeing 1-1.5 degrees of knock retard on one of my early setups. That was taking away up to 5 degrees of timing! Taking away that much timing slows you down. May not seem like a lot, but it is. (Note I had the ability to add timing too and adding 2 degrees of timing to my daily driver 91 octane tune required the use of race gas to give you some idea of how big 5 degrees could be.) Adding in a throttle body spacer that cut off coolant flow to the throttle body eliminated this 1-1.5 degrees of knock retard.
Did I feel it? Ehhh...kinda. Was it a huge change? No. But I DID get back a bit of performance (and you could see it on my 1/4 mile time slips) and I knew my engine was safe from damage due to knock. While it isn't a HUGE change, every little bit helps and for something this simple, why wouldn't you do it?
