Can someone explain to me like I'm 12 how the boost control works on the common centri kits? Mine has an ECS Novi 1500 kit but I imagine many of them work very similarly.

I understand the boost pressure is regulated by the blow-off valve, it has a spring inside that is adjusted (somehow) to offer more resistance to opening.

Where my brain goes into derp mode is when I consider the hose going from my throttle body / Intake to the blow-off valve. This would create a vacuum under low boost / partial throttle? And have feedback pressure when under wide open with boost, helping to keep the BOV shut? Wouldn't this create a feedback loop where the more pressure in the intake the more pressure the BOV will hold and overboost the engine? Clearly I'm misunderstanding something here 😵‍💫

 

On centri setups, the BOV does not regulate boost. Nor does it on turbo builds.

The BOV doesn’t respond to “how much boost,” it responds to the difference between manifold pressure and charge pipe pressure.

Boost will be determined by a few different factors on centri builds; pulley combo, engine/exhaust air flow etc.

 

I understand the charger will produce more or less boost depending on the factors mentioned. But if the BOV only purges pressure when there is a difference between manifold and charge pipe, would that mean at wide open throttle the charger is allowed to dump 100% of all available boost into the engine? Until the driver slams the throttle shut. In other words, there is no boost control?

On turbo cars I've owned in the past the boost is mostly regulated through wastegate actuators.

 

Yes sir that's correct. There's ways to control boost but you'd need a wastegate as stated which generally arent used on supercharger builds. Smooth Boost controller has a setup to help manage boost, for both PD blowers and centri. It'll bleed off boost at tuned levels to help manage traction etc.

 

So that also explains the restrictor plate in the airbox! Thanks , it's making sense to me now.

 

Using something to limit the maximum boost level so you can run a smaller pulley is great! It allows you to get into boost sooner and at the same time, protect your engine if you are running a SBE or your driveline is not built.

I did this with my car and it is awesome. I am able to run a smaller pulley so the boost comes in sooner. i.e. at lower RPM, so I get the benefit of boost sooner. I have a run of the mill manual boost controller plumbed into the boost reference line between the intake manifold and the Blow Off Valve. I ran my SBE LS3 at 750 WHP for four years like that.

I just had a new engine with forged internals put in the car and am working through teething problems and getting the tune right so I have the boost limited to a little less than 6 PSI. When I am ready to turn it up I can simply twist the **** on the boost controller a bit. I did make a jig so I can set the boost level the boost controller opens at while it is off the car which I used to set the initial level.

The boost level will be the setting of the boost controller plus the spring in the Blow Off Valve.

I am using a Hallman boost controller and a TurboSmart Race Port Blow Off Valve.




Using a restrictor plate to limit boost is pants on head stupid.

Compared to using a manual boost controller;

1. It is not 'adjustable'. You have to change the plate to get more or less boost.
2. It is not precise. You have no idea how much boost you will actually get until you run with the new plate.
3. It increases IAT's.
4. It increases parasitic loss. The supercharger will require more engine power for any given boost level.
5. It increases the likelyhood of belt slip.

 

Well I didn't to put too much shade over a technique some shops are using with their kits, but yes several of your points ran through my head.

Eventually I'd like to switch to some form of boost controller as you said. Having the perfect amount of boost at a much earlier RPM just makes more sense.