i want to run one on my SOS kit i just bought


i am going to run a 3 inch pulley and want to limit the boost to 15-16 psi

has anyone had any experience with these?

i messaged someone who has ran one and they said it didn't do a thing for them

i want to make sure it will work and hold boost and not let it pass 16 psi



anyone with any info or experience with these please chime in

 

I suggest you see how much boost you make before proceeding.

You may not be making what you think.

Just an FYI, there is more than one way to decrease the top end boost.

It is possible to decrease boost and at the same time increase horsepower and torque.

You do this by making the engine more efficient under boost.

Decreasing the cam overlap in conjunction with a supercharger will do just that.

IMHO, It's less expensive to change the cam timing than to purchase and install a silly unreliable and probably uncontrollable release valve.

 

That's a good point. Here are the ways I can think of to reduce the boost pressure building up inside the engine:

Things you can do to make the engine more efficient:
- Cam changes, as Sideways noted above.
- Intake Manifold changes - aftermarket manifolds can flow more air, thus making more power and reducing the boost building up.
- Exhaust changes (header, TP, cat-back, cut-out) - same thing, flow more air, reduce boost buildup, make more power.

Things you can do to limit the boost reaching the engine:
- Boost Limiter Valve - to blow off excess boost.
- Restrictor Plate - to physically limit how much air can enter the supercharger.

There are some other threads floating around with details about the restrictor plate. It's 100% reliable, works every time - but you'll see the torque curve drop off steeply once you reach the cfm limit of the restrictor. HP and cfm are mathematically linked, so HP will stay flat, but torque will drop because the engine requires more air to make the same torque as rpm's rise. Thus with a fixed limit to the airflow, torque drops as rpm increases. Not a big deal if you set it up to happen close to redline, but probably not fun if it happens in the midrange.

What I mean is, if you use a restrictor plate to limit boost from 16psi to 15psi, it'll be a nice solution and you'll barely feel the difference when it happens. But if you try to limit a 16psi setup to 12psi or 10psi, the car could feel like it hit a wall in the midrange.

The BLV, by contrast, should theoretically just blow off the excess boost. S2000Shifter's seemed to work nicely, but I wasn't able to get enough dyno time to get mine to work before I sold the kit.

 

I plan on using one. Many other cars use them with great success. I am hoping to run 18-19 psi and bleed off over 14 psi I believe. I don't see why it wouldn't work.

 

Or you can always run a wastegate like turbo guys. Also Evans tuning said anything done to improve on the exhaust side will not make boost pressure go down but you will make more power at that psi. Only intake side of the motor will reduce what psi you make.

 

Limiting boost to 16 psi means the valve is only going to be in operation for the last hundred rpm, kind of pointless in my opinion.

 

Ive done this. I have an 18psi pulley but limit it to 12psi using a restrictor 'plate'. The idea being I have 12psi without WMI for trackdays and then an unrestricted meth tune for drag/street racing

I looked into the pressure relief valve but decided it would be too noisy for my liking. So the restrictor plate was the one for me. Some rumours that these might create an IAT increase but i havent found that. I can give you the dimensions of my restrictor, it made 350whp.


http://www.flickr.com/photos/61873555@N06/6340639475/

 

Dimensions would be great, as well as install info.

I toyed around with the idea a little bit by adding couplers inside the intake. I was able to knock down the AFR a point at redline.

 

Yes wastegates would be a better method that a boost limiting valve, if you do some searches on the net quite a few people have applied them successfully. The key is that you have a good boost controller as most of them will not be sufficient for good modulation. If you have an AEM, HalTech or other higher end standalone the feedback loops, temperature trims……. should be sufficient for fairly precise control.

As for the exhaust that is not true at all. Here is a way to think about it, the supercharger is just a pump and for any given flow it can produce XXX PSI, the higher the flow the lower the PSI and vise versa. So if you remove restriction from the discharge of the supercharger to the tailpipe it will increase flow and lower the pressure. Without out going into too much detail, as Sideways mentioned overlap plays a very key role, reduce the overlap, reduce the duration of the boost blowing through to the open cylinder. So, since we know we are pushing CFM right through the cylinder, by lowering the exhaust back pressure, increasing the CFM and lowering the boost. I have seen a header decrease the boost in a supercharged car as much as 3PSI (V8) and I am sure you will find MANY examples out there.