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Time to solve the plumbing mystery. The "bypass" circuit you describe is the idle control system coolant pathway. It's the same path on both the 91-94 and 95-05 NSXs, but it covers different components between the two versions.On the 91-94 NSX models, the engine uses three components to manage the air intake and idle system: the FITV (fast idle valve); the EACV (electronic air valve) and the throttle body. For reliable operation in cold weather conditions, hot coolant is tapped right off of the rear head coolant exit pipe and passed through all of these components. It follows the following path: FITV --> EACV --> Throttle Body --> Water Jacket. You can see the pathway below.[ATTACH=full]198643[/ATTACH]On the 95-05 NSX models, the DBW throttle body eliminates the need for the FITV and the EACV since the throttle plate now controls idle. Thus, the hot coolant goes from the rear head directly to the throttle body and then exits into the water jacket. The "connection in between" those two hoses in your photo is the throttle body, which is not between the hoses, but after them. [ATTACH=full]198645[/ATTACH][ATTACH=full]198644[/ATTACH]
Time to solve the plumbing mystery. The "bypass" circuit you describe is the idle control system coolant pathway. It's the same path on both the 91-94 and 95-05 NSXs, but it covers different components between the two versions.
On the 91-94 NSX models, the engine uses three components to manage the air intake and idle system: the FITV (fast idle valve); the EACV (electronic air valve) and the throttle body. For reliable operation in cold weather conditions, hot coolant is tapped right off of the rear head coolant exit pipe and passed through all of these components. It follows the following path: FITV --> EACV --> Throttle Body --> Water Jacket. You can see the pathway below.
[ATTACH=full]198643[/ATTACH]
On the 95-05 NSX models, the DBW throttle body eliminates the need for the FITV and the EACV since the throttle plate now controls idle. Thus, the hot coolant goes from the rear head directly to the throttle body and then exits into the water jacket. The "connection in between" those two hoses in your photo is the throttle body, which is not between the hoses, but after them.
[ATTACH=full]198645[/ATTACH]
[ATTACH=full]198644[/ATTACH]
