[idealer]

Originally Posted by forzasteve

The Corvette post has one of the issues that I see with retrofitting something that relies on vacuum for operation ... and that is the issue about variable vacuum levels. As the Corvette guy made note of ... open the throttle and engine vacuum declines or even entirely disappears, close the throttle and it builds up.

The Mild2Wild kit for retrofitting the NPP exhaust to a Camaro is another Rube Goldberg modification. As it comes in their packaging, it does not provide a means to stabilize the variance in vacuum and it uses long lengths of rubber tubing and the way it suggests to tap into a vacuum would have you believe that nothing could go wrong.

First, just so you know, the variance in vacuum that is present can be problematic when you are trying to control the exhaust bypass valves on your car. You don't want them opening and closing with just the mere application of throttle position. That is just plan bad implementation. If you are thinking of retrofitting an NPP exhaust to your car and retaining the vacuum actuation, there are five things you should consider.

1. Recommend you do not run long lengths of rubber tubing from the engine bay back to the rear of the car. Rubber deteriorates over time and this method of routing vacuum may lead to vacuum leaks. Recommend you run a long length of solid metal tubing ... just as the factory does. This will not cost much but it will be a bit more difficult to install vs. rubber tubing. There is a reason why factory uses metal tubing to route vacuum over long lengths.
2. Be careful how you tap into your vacuum source, (typically the engine manifold or by tee-ing off an existing vacuum tube in the engine bay). I would avoid drilling holes in the intake manifold. I think better to tap into an existing vacuum line. Read Idealer's post above.
3. Somewhere back where you intend to use the vacuum to control the exhaust bypass valves, install a small vacuum accumulator. The Camaro with the NPP system has a small plastic canister right close the vacuum solenoid valve. The use of a vacuum accumulator will provide a stable source of vacuum to eliminate the variance that is caused by opening and closing throttle. You should be able to purchase a plastic accumulator for a few bucks. Should not be big expense.
4. Put a one-way check valve on the inlet side of the vacuum accumulator so when you open the throttle it does not cause loss of vacuum in the accumulator. Again, very inexpensive.
5. Use a solenoid valve to control the vacuum to the bypass valves actuators. You can get a solenoid valve for about $20 or so. You do not need to have remote transmitter. You can control the solenoid much more efficiently with simple on/off switch mounted in the cockpit. Since you going to the trouble of doing all the rest of this, just go ahead and get a simple on/off switch to control the solenoid. Just provide a +12V to the positive side of the solenoid and fuse protect that. Then route a single wire from the ground side of the solenoid coil to one of the contacts on the switch and then ground the other contact of the switch. This eliminates the risk of a short circuit at the switch and do not need to fuse protect the wire going to the switch.

It really is critical that you take the time and effort to ensure that you do not do something to increase the risk of a vacuum leak. Your engine fuel management and emissions controls rely very heavily on vacuum and putting something in place that may cause a leak can cause problems that could be difficult to diagnose. Better to do it right the first time rather doing it over.

Oh, one last thing. Document what you are doing. You may want to return to stock and it would be really a nice gesture for a future owner to know what you have done.

Regards,


Steve

Very good advice, which is why my neighbors will have to deal with the always open valves for now.