[Lear35A]

Three hoses go into the top of the throttle body. The larger center one is is removed with the D1R supercharger kit. The two smaller ones can be eliminated if you don't want your inlet air heated by coolant.

Last night I found some plastic caps at Ace Hardware that look to be a great way to block these off. I used a hot air gun to warm them up and worked them on to the connectors on the TB. They are a nice and tight fit, and I think finish off this mod nicely. I think they cost $.23 each.

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[flash]

just make sure you put a clamp on the center one or it will pop off of there.

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[Fox944]

I plugged these holes up on my N/A 968. Common modification amongst Honda Tuners also.

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[flash]

yeah - not a big deal on N/A. needs to be sealed nicely on boosted cars

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[Fox944]

nop, especially not on a street car....but I would def recommend sealing them up if you track the car....especially on hot days.

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[flash]

be advised, on N/A, if you have to smog your car in the winter, capping off the pre-heater may cause it to fail. that is there for emissions, to optimize combustion temps, and prevent the "freezing" effect cold air can have when rushing in. it needs to be warmer for clean emissions.



centrifugally supercharged cars don't really have to worry about this, as the heated air from the supercharger would take care of that.

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[Fox944]

yes, agreed. My car wouldn't have passed emissions in NYC either way. That said....outside of NYC (within New York State), OBD1 cars only require a safety inspection...so smog doesn't apply. You can pretty much run no cats...and as long as all your lights work, brakes/tires check out and there is no check engine light on...you are good to go. I still ran a Cat on my car however.

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[Cloud9...68]

This is good info - thanks. What does the center one do on a N/A car? And if I remove the end ones, I assume I have to plug wherever the other end of these hoses go.

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[Lear35A]

I only posted this for aesthetic advice, not technical. The center grey cap is a shrink fit on there and very tight, but since it does see the boosted SC pressure, I will clamp it as well.

As far as the coolant hoses that go in and out of the TB, I intend to interconnect them with a barbed fitting (which I don't have yet). I wanted get rid of those hoses completely, but they may provide a needed flow out of the back of the head. I just don't know, so I'll err on the side of caution unless someone has some hard data that this flow isn't needed.

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[Fox944]

I had the two coolant lines interconnected as well...so the coolant is still flowing, just not through the TB. The Center is an air hose.

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[flash]

lear - no worries - just wanted to make sure it didn't pop off, and you vent your boost to atmosphere.



re: interconnect - yup - i did the same thing.



caps look great though.

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[Cloud9...68]

So you just literally connect the two coolant hoses to each other, allowing coolant to flow out of one and into the other? OK, that makes sense, plus it makes it easy to put them back onto the throttle body at emissions testing time.



It looks like the coolant flows continuously through the throttle body at all times, even after the engine is fully warmed up (I don't see any evidence of a normally-open thermostat, in other words). This seems crazy - why on earth would you want to heat the air entering the intake manifold?



So, how many horsepower does eliminating this throttle body heating buy? At least 50, right? <img src="/forum/images/smilies/968/tongue.png" class="smilie" alt="" />

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[Cloud9...68]

This thread made me think of something - to me, like to most 968 owners, I'm sure, the collection of vacuum and cooling hoses running through our engine bays is a major mystery. It's good to finally underestand what the two end ones going into the threttle body do. So, I was wondering, does anybody have a diagram of all the hoses in the engine bay, with a description of what each one does, and where they're connected? Lance, is this what you told me you have access to? It would be very informative to see what the purpose of all these hoses is. Knowledge is power, after all (just wish it was HORSEpower...)

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[Lear35A]

Not that easy to put hoses back on the TB at emissions time. You'd have to drain down some coolant or at least pinch off both hoses well. Otherwise you'll have a big mess.



I have sloppily drawn diagrams of all the hose routings, but they're too crude to help anybody else. I need to motivate myself to do this right sometime. Not making any promises.

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[DaveN]

I'm going to do this as well when I reassemble my engine. As an obscure reference for the oldies maybe we could get Arlo Guthrie to do a 968 version of Alice's Restaurant with pictures and circles and arrows on the back explaining what each hose does?

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[flash]

roflmao - i remember the song - been to the restaurant

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