So I'm running a 11' MCS on a custom tune running about 20 lbs of boost. I uprated the diverter valve with the Alta spring which was working fine for about 3 months(3k miles?). Right now the car scales up to boost, but when it gets up to about 5k it scales down to about 16 and i'll shift and regain 20lbs in the lower revs. Is this my DV just not keeping up even with the alta spring? or a possible leak somewhere else? Oroginally the car held 20lbs all the way up the rev range and im just not sure what would cause the loss of boost. No CELs or other problems with the car.

 

Who did your custom tune?

 

Speedriven. I have a local installer/dealer.

 

Sounds like you have a boost leak somewhere. Have any work done recently?

 

Not anything specifically with the vacumn or boost lines. I'm gonna have the lines double checked. I've just heard problems with the stock diverter being plastic so that was my first assumption

 

Usually the problem with the DV is the rubber diaphragm will get a tear in it and you wont be able to get much power beyond 4k. I changed my DV to the GFB DV+ to avoid that kind of issue.

Also, sometimes the intake manifold gaskets leak. Or if you have an oil catch can, that can be a source for vacuum leaks.

 

Update on what's going on the car is still losing boost but now there is a clacking noise, like a shutter. Not sure if it's from DV but I think it is. Anyone know of any noises the DV can make?

 

Havent you checked the diverter valve yet? Until you actually check the DV we can't eliminate it as a possible cause, sometimes the spring gets stuck crooked inside the diverter valve and can cause boost leaks.