View Full Version : Product Release - Nizpro Boost Control Valve

15-03-10, 07:30 PM

15-03-10, 07:57 PM
Have a read of what Simon from Nizpro (the guru behind all of this) has to say. It is a very interesting read.

If you trace back thru some of my history you will find around 10 to 15 years ago I was not a big fan of waste gates controlling boost and there were a number of reasons for this.

1. The largest waste gates were only 45mm
2. They were large and hard to physically fit in the engine bay
3. It was difficult to position them in the exhaust manifold to maximise flow
4. They would still allow over boost if the turbo was very good

During this time I made a very simply over boost vent valve that was located on the compressor side of the turbo outlet. Either side of the intercooler worked well, however the hot side allowed a tiny bit of creep about 0.5 psi and if you located it on the cold side of the cooler the boost was super stable but you wasted the cold air the intercooler made. This would relieve the extra boost that was not needed even if the waste gate was unable to cope with, capping boost levels. Friends of mine dubbed it the Simey valve and I used them at stages to completely control boost pressure and deleted the waste gate altogether. It also stopped Nissan rb30 engines dumping conrods on the ground, sounds familiar

The problem doing it all with the valve however once turbos became better and better was higher back pressure than if the boost was controlled with a waste gate. Over the years waste gates started to improve and started getting bigger on the inside now 60mm and smaller on the outside, so they are now easier to fit. But it still remains that fitting them in a good flow position is difficult and you can still see over boost with super big flow turbos at low boost pressures. What do I mean with that last comment? Hence drag cars in the US can run two 60mm gates.

Think of two different applications.

1. 2 litre 4 cylinder 800 hp engine running 40 psi boost and having 25 psi exhaust backpressure
2. 8 litre 8 cylinder 800 hp engine running 10 psi of boost and 5 psi backpressure

Same power but example 1 has a 25 psi pressure differential between the one side of the waste gate and where it verts to atmosphere. So open the waste gate and the gas has plenty of force to escape, so boost control is easier and normally works well

In example two you have 5 psi differential so the exhaust gas just keeps going thru the turbine and making boost, you have poor control and normal over boost occurs. We see this in XR6T’s and that why you do turbine mods.

So at last we have the next generation of simey valve. It fits onto the intercooler piping and can be adjusted to different boost levels, they are billet alloy and super simple to adjust.

It also gives protection if the waste gate jams or the actuator hose come off or while tuning. This is the turbo safety valve everyone should have. It’s the valve you don’t need until its too late.