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Intake manifold Coolant Hose

2035 Views 8 Replies 4 Participants Last post by  Chris6
I heard of this in honda's and Nissans, I am really not too knowledgable or I don't even know what to look up to find this. It heats up something so when cold starts are easy, But it also heats up the manifold. Its a hose. I sound like such a tool. soo can someone help me?

Or we don't even have this on our 1st gens?

Just tell me if I am being too vague
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search for the cooling system diagram. it will answer your question :tup:
It appears to be the BAC valve, I Will go look it up
OK Bypass Air Circuit valve. That helps cold starts. Is it possible to remove it? And re-attach this to the other end.
I have heard this done on other cars. Except I don't have my car with me so I can't look on one.
I probably won't do this but just a thought. For now my car doesn't need help with cold starts.
It heats up something so when cold starts are easy, But it also heats up the manifold. Its a hose.
I think you may be referring to two different items here.

There is the BAC which adjusts the cars idle depending on coolant temperature(cold coolant means high idle and when the engine/coolant warms up the idle lowers to 750rpms or so). On removing the coolant line..Id suggest not to do this. I have had a faulty BAC before and without it functioning properly it seems the ECU figures that the engine is cold all the time and defaults to a high idle setting all of the time(like 2000rpms).

On the 90-92 cars there is a coolant jacket that was added to the throttle body. In cold climates sometimes there can be frosting on the throttle butterflies which can make for a sticky throttle. The coolant jacket was added to warm the plates so this would not happen. This is separate from the coolant that runs to the BAC. Its interesting to note that there are plenty of 88-89s that are in cold climates and without the coolant jacket on the TB but its rare to hear of this phenomena occurring...maybe in the arctic?

Removal of the line is something that owners of other cars that have a similar setup have done. The assumption is that the coolant heats the surrounding area and adds to heat soak of the intake manifold. A cool intake manifold and cool air is always better for that extra bit of power. Its my guess (could be wrong about this) that the intake air is rushing in so fast that there is little heat transfer from the intake manifold anyway, so removal of the line for the coolant jacket isnt worth that much. Something....but not that much.

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Wow someone either knows a lot or has done his homework. Either way kudos to you. So I won't even think about removing that line. Actually now that i think about it, I read something about controlling the idle in Haynes. Didn't think that it was refeering to this piece.

My engine idles around 2.2 then after a minute, down to 1.7 and after 5 goes to .8. That IS normal right?
yea thats normal, and yes gavin is very informative!
you might want to click on the little
down on the left side of his post to leave some karma for him.
(not enough people use this button)

and Gavin, I agree with all you said, and the little extra heat that would be there from the coolant, is very minimal, vs. all the heat around the manifold in the first place.

I don't think it would do anything with the idle though, as long as the BAC was still there and hooked up. I know yours was idleing high, but i'm sure this was just due to the unit not functioning properly.

Either way, I don't see a gain in removing the line either, unless strictly a 1/4 mile car, that your ''iceing" inbetween runs........
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I suppose the heat introduced to the TB could be worse on some other cars with this setup and really have an effect(I seem to vaguely recall something like this done to camarobirds?). Ive never took a thermometer to the MX6 to see what the real difference was, but I really suspect that its not "that" bad overall.

When I was having issue with my BAC I never did pull the plug on the unit to see if it would idle better or worse, so who knows. You may be right on that one as I was pretty busy with just getting it fixed. Still, I dont see much value in pulling the BAC out of the loop especially when keeping the stock ECU.

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Yes I know about karma...

And I recall I read this on a Honda tuning site. You know how they will do anything to their spivics if its a cheap fix or mod. IDk if their BAC or form of one controlled the idle. But at least I learned something new about the F2 today.
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