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Hose between throttle bodies


thumper
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My vacuum ports were pluged with a bolt. My 996 Ducati had a hose between the throttle bodies and the setups are simular.

Is this correct to have a hose between um or plug it?

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I think most of the US models came with a T-hose between the throttle bodies. The third line of the T connected to the canister to re-process the evaporated or spilled fuel (thus reducing emission).

But most of those canisters seem to "fall off."  I just capped the fittings, rather than remove them and plug with a bolt. That way I can remove the caps when I want to balance the TBs.

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3 hours ago, thumper said:

10 4 thanks that canister fell off long ago

So I will run a hose between the throttle bodies.

Thanks Scud

You can but you need to block it with something or just remove it and put a bolt in the manifolds to blank them off.

Phil

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I've seen them with a straight hose between the TBs (no T). Also seen the T cut short and blocked off. Also seen bolts threaded in, and simple caps on the fittings where the hose would go. 

The key is not to allow any air into the head unless it goes through the TB. This is also the reason they run so poorly when there are cracks in the rubber boots betweem TB and head.

@Thumper - if you're going to run a hose, that must mean you have the screw-in fittings to replace the plug bolts.

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Yes I do. I have been switching the bolts out to do the TB adjustment.

Just wondering what is the better way to go, will one effect the cough more than the other.

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I like mine capped, but probably no discernible difference if there is a tube between them. I can see no good reason to connect them unless you find that convenient.

I did learn that simple rubber vacuum caps dry out, loosen, and crack over time. Switching to tight fitting silicone caps seems proper.

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There is no advantage to running a line between the two throttlebodies. The factory does that when they need to connect the two throttlebodies to the EVAP system. If the EVAP system "fell off" there is no longer a reason to connect the two throttlebodies. Nothing bad will happen if you do run a line between the two throttlebodies, but it doesn't help either. Do whichever is more convenient to you. I think directly capping off the ports at the throttlebodies is more convenient, but if you find a tube between the ports is more convenient do that.

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FWIW.  I removed the evap can T-hoses and capped the manifold ports with high temp vacuum caps bought from McMaster-Carr.  The problem with the caps is that every so often a cap would blow off during cold start cranking.  To prevent the cap from blowing off I cinched the outside diameter of the cap with small gauge ss lock wire.  Then over time I noticed the high temp caps discoloring from heat, I eventually removed the caps, manifold nipples and replaced nipples with screws & fiber sealing washers....it's been fine since.

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The only time I've seen a cap blow off (or once, tore the cap's tip open) was from throttle body imbalance . . .

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On 7/21/2022 at 11:10 AM, docc said:

The only time I've seen a cap blow off (or once, tore the cap's tip open) was from throttle body imbalance . . .

I'll check the balance but I don't have driveability issues like when I got the bike and the TB's were way out of sync.  Anyway, give me a few days.

Update: OK, I couldn't wait, I ran out to the garage, put the SyncPro on the Lemans, it's all good!  TB's are balanced at idle and fluid columns rise in sync as throttled up (to 4k rpm).:thumbsup:

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  • 1 month later...
5 hours ago, KenBlake said:

Using a bolt seems like the cleanest option. You can always remove them and insert brass fittings when it comes time to balance the TBs. 

I did that until the aluminum threads of the manifold came out with the bolt one time. I'm certain this had something to do with the shaved ape that was turned the wrenches . . . :blush:

Then it was back to the brass fittings with caps.

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