Could a 7psi spring and 20psi mbc setting cause boost spikes?

[Hiitman]

My wastegate has a 7psi spring and I want to run 23-25psi through my mbc. Could having such a low psi spring and such a higher boost cause boost spikes?

 

[JusMX141]

Not likely. The boost pressure never reaches the actuator until it passes through the MBC.

Does it spike quickly just before the wastegate opens? It could be a result of where the MBC is hooked into the piping.

For example, if you Tee your MBC into the BOV line, the boost source is the intake manifold. The turbo's boost must travel from the compressor, all the way through the intercooler piping, into the intake manifold, then into the vacuum line for the BOV before it can be limited by the MBC and then finally reach the wastegate actuator.

All of the cars I work on get their boost right at the compressor housing or in the intercooler piping close to the turbo at a source separate from all other devices. It only operates the MBC and the wastegate actuator.

 

[Hiitman]

I've got it T'd off the compressor housing. My sbr turbo comes pre-tapped. It goes from there to the mbc to the lower nipple on the wg. I shortened my vac lines by about 2 feet. The mbc was mounted over by the intake filter and now its mounted on one of the fan mounts. I also ordered a forge motorsport bov to replace my 1g because I was told they can only hold about 18psi. I'll see if that helps once it gets here on Monday.

 

[JusMX141]

Forge makes a great BOV- I've installed two of them on customer's Evo's. They do require different springs for tuning, however....for example, the spring that comes standard in the Forge Evo BOV is rated up to 15psi; which is less than an Evo's stock boost pressure.

If you had crushed your 1G BOV and/or done the Dodge Garage Mod, it would've held higher boost just fine.