Ever since I put the custom manifold on my vg30 it makes this strange suction noise. It's a loud noise and can be heard inside of the car at low speeds. The lower the pressure the stronger the noise, it goes away when the throttle is depressed. The noise can be heard exactly above the velocity stacks, and sounds even for both sides of the manifold. I've checked for pressure leaks, fixed some small leaks but the noise is still there. And even if it were another leak it doesn't make sense as it sounds equal to both sides. The engine doesn't run very well at idle but that's more due to the very low compression it makes. The loud tap is a valve lifter, at 4 and 8 seconds when I hold the camera above the manifolds you can hear the suction noise. In the last few seconds after shut down it's the only noise you hear bleeding away; http://www.youtube.com/watch?v=L_Ffk9b5T2s&feature=youtu.be WTH is it? Going to the dyno tomorrow need the manifold to be OK. Thanks for any suggestions Rutger
sounds like the air getting sucked through the idle circuit. would explain why it goes away as soon as the throttle is opened.
This might sound weird, but use length of "garden hose" tube, with one end to your ear and use the other end to move around the engine bay. The sucking noise will get louder to your hearing when you get close to the location of the leak.
Or spray C.R.C / RP7 type stuff around the manifold until the noise changes. If it changes noise that's the area it's sucking it in. Cheers Dave
I've already done a full pressure on the entire upper manifold, and it held 1.0 bar boost with only marginal non-affecting leakage. I've sprayed brake cleaner over everything without change in idle. The only thing I can think of causing a leak would be the injector seals. But then the noise would not come from the area above the velocity stacks but from somewhere down below. Could it be the decrease in wall thickness and shape of the manifold causing the noise?
