M90 Pressure relief valve

[Kev]

I was talking to my boss today about the M90 I have bought and the manifold kit etc from Richwoods. We got talking about how much boost it would run and he asked what the pressure relief valve was set at. I sort of gave a silly look and he realised I had no idea. He use to race years ago and said if the engine has a big backfire and no pressure relief valve fitted, you can blow the supercharger or manifold off as the expanding gases can not escape through the supercharger. I'm not talking about the bypass valve here, so whats your thoughts. I can not recall anyone mentioning it and nothing found with a search.

Ta, Kevin

 

[striker]

It's been around before over here but I cannot find the thread, it had a pretty awfull piccie of an SC comming through the bonnet of a dragcar.

I seriously doubt that will ever happen in a none insanity installation.

Lots of cars running like this without problems,

grtz Thomas

 

[stevechumo]

I was talking to my boss today about the M90 I have bought and the manifold kit etc from Richwoods. We got talking about how much boost it would run and he asked what the pressure relief valve was set at. I sort of gave a silly look and he realised I had no idea. He use to race years ago and said if the engine has a big backfire and no pressure relief valve fitted, you can blow the supercharger or manifold off as the expanding gases can not escape through the supercharger. I'm not talking about the bypass valve here, so whats your thoughts. I can not recall anyone mentioning it and nothing found with a search.

Ta, Kevin

I haven't heard about the M90 can cause that. The worst that I heard of is it got the gearing broken. From what I heard, the M90 can max out at 9 psi and that shouldn't blow it off. For the valve, as long as it's there, you should be ok. It's because when you let off the gas, it will open up and release the excessive immediately. After you fit the M90, you can test it out. I wouldn't care about it too much. Just set it in the middle and you're fine.

 

[Cobber]

Some do and some don't it depends on what it came off. GM / Pontiac etc have an internal relief when fitted to the OEM application. Ford T bird does not.
For our application don't worry about it.
On the picture below the relief valve is under the plate with PCV on it.

The top plate on the Richwood Manifold is not ported through so it is not used anyway.

 

[Deuce]

Kev, A pop-off valve is required when using a toothed (Gilmer type) drive belt as used on dragsters. This is because the belt cannot slip allowing pressure relief through the blower. An M90 with a ribbed drive belt can slip if a backfire occurs, reducing the chance of damage.

 

[Kev]

Cheers everyone. Thanks for your knowledge and the info.

Kev