Making m90 run quieter?

skillton

Registered User
My friend is using an m90 from a supercoupe on his truck. It's reallly loud. When he ran it @9psi, it was even louder, it sounded like a sports bike almost. Now he's running 5psi, and it's still very loud. He's getting hasseled by the cops on a daily basis, so he had to take the belt off of the charger for daily driving.
Is there any way to quiet them down? From what I rememeber the're not as loud on the supercoupes, especially at low rpm/idle. His is for some reason. It's in a Toyota Tacoma truck, and he had to mount it on the body(I think where his old airbox was), using solid motor mounts. Also the belt he's using is thinner than the pulley by about 1/3".
Do you guys know why it could be so loud? I was thinking it could be belt slippage, but not sure if it would cause it to be this loud. Is there any type of siliencers, or a way to make it more quiet?
 
Tell him to use the stock silencer from the Tocoma on the inlet of the SC. Is he using the bypass valve? Is the TB on the inlet of the supercharger? That (TB) will make the largest difference.

Jeff
 
Which one is "these". The Supercoupe or the Tacoma?

The supercoupe is supercharged from the factory. For the Tacoma it's a dealer installed option.

Jeff
 
skillton said:
He's getting hasseled by the cops on a daily basis, so he had to take the belt off of the charger for daily driving.

Why do I think it isn't the supercharger itself that attracts attention?

Anyway, I'll bet that part of the reason it's so loud is that there isn't a part-throttle bypass. That in itself will increase noise substantially.
 
Parker Dean said:
Why do I think it isn't the supercharger itself that attracts attention?

Anyway, I'll bet that part of the reason it's so loud is that there isn't a part-throttle bypass. That in itself will increase noise substantially.
He took the belt off it because he was getting hasseled only because of the supercharger.
He's putting on a dump valve, it's the same/similar to a bypass valve right?
 
J57ltr said:
Tell him to use the stock silencer from the Tocoma on the inlet of the SC. Is he using the bypass valve? Is the TB on the inlet of the supercharger? That (TB) will make the largest difference.

Jeff
TB is on the intake manifold, in the stock location.
I told him there has to be some kind of silenecer for it... We're gonna look for one from a stock tacoma.
 
Moving the TB to the inlet of the SC will make a larger difference than a silencer. Also the bypass valve, you can try one off of a Saab 900 or 9000 both use a Bosch valve.

Jeff
 
J57ltr said:
Moving the TB to the inlet of the SC will make a larger difference than a silencer. Also the bypass valve, you can try one off of a Saab 900 or 9000 both use a Bosch valve.

Jeff
He already has a dump valve, we just need to install it. as for the TB, not sure if we can do that, but I'll have a look @ it tonite and see how hard it would be to relocate the TB.
 
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skillton said:
He took the belt off it because he was getting hasseled only because of the supercharger.
He's putting on a dump valve, it's the same/similar to a bypass valve right?

Uh huh.

I don't think a dump valve is quite the same thing. Where exactly is the throttle plate, before or after the blower? For quietest operation, the throttle would need to be before the supercharger, and also a bypass valve so that air can get to the engine without having to go through the supercharger. If what you're calling a dump valve is what I'm thinking of, it would only increase noise by adding in the hiss of compressed air.

The thing about positive dsplacement blowers like the Eaton is they move a lot of air at low speeds, unlike a centrifugal or a turbo (which is just another form of centrifugal supercharging). So the game becomes reducing the amount of air the superchager can get at part throttle.
 
Parker Dean said:
Uh huh.

I don't think a dump valve is quite the same thing. Where exactly is the throttle plate, before or after the blower? For quietest operation, the throttle would need to be before the supercharger, and also a bypass valve so that air can get to the engine without having to go through the supercharger. If what you're calling a dump valve is what I'm thinking of, it would only increase noise by adding in the hiss of compressed air.

The thing about positive dsplacement blowers like the Eaton is they move a lot of air at low speeds, unlike a centrifugal or a turbo (which is just another form of centrifugal supercharging). So the game becomes reducing the amount of air the superchager can get at part throttle.
Hmm, it might be a by-pass valve that he got. He just got it on friday, and I only had a short chat with him... maybe I mis-understood.
Anyway, the TB is still on the intake manifold, in it's stock location. The m90 is mounted on the body of the car, where the stock airbox used to be. There's a pipe with a cone filter going to it, then there's a pipe that goes straight to the throttle body.
 
Well, that is why it is so loud. It is not supposed to be installed before the TB. It's supposed to be installed after the TB. If you have it installed in front of the TB, then the supercharger is running full tilt all the time. That is why it is so loud.

Most likely the whole system will need some re-engineering to make it run properly (ie. safely).
 
XR7 Dave said:
Well, that is why it is so loud. It is not supposed to be installed before the TB. It's supposed to be installed after the TB. If you have it installed in front of the TB, then the supercharger is running full tilt all the time. That is why it is so loud.

Most likely the whole system will need some re-engineering to make it run properly (ie. safely).
Alright, I guess we'll try to find a way to mount it before the supercharger. It will be pretty difficult tho.
What if we installed a bypass valve like this one:
eaton_bypass_valve.jpg

at the inlet of the supercharger? It should be closed under light throttle, and open under heavy/wide open throttle.
 
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Just the opposite open at light throttle and closed at open thrrottle(heavy load)

What engine is this? 3.4L? If so the factory kit takes place of the upper intake runners. The TB is mounted before the SC. It's also that way on the other kits as well.

Jeff
 
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skillton said:
Hmm, it might be a by-pass valve that he got. He just got it on friday, and I only had a short chat with him... maybe I mis-understood.
Anyway, the TB is still on the intake manifold, in it's stock location. The m90 is mounted on the body of the car, where the stock airbox used to be. There's a pipe with a cone filter going to it, then there's a pipe that goes straight to the throttle body.

Yep, that's about what I figured. As Dave mentioned it'll need re-engineering to put the throttle body over where the air filter is. Then that bypass valve that was pictured would need to be installed such that it allows air to flow from the pipe between where the air filter is now and the pipe leading to the engine. This valve is connected to manifold vacuum and is open at part/closed throttle and closes under acceleration so that all the air goes through the supercharger under acceleration. Set up in this manner the supercharger should be as quiet as one in a 'Bird with a CAI.
 
This is completely on glue, if you had the m-90 in front of the throttle body, I would second Dave's motion to rip it all apart and start over.
 
Since we have NO idea of WHERE in this country you are located ('cause people just REFUSE to put that in their header info) then I can only assume that MANNY either built this for him or put him up to it.

Take it to the strip and see how it does!

'bird
 
We will be re-locating the TB before the m90. It will be on the intake pipe now, between the MAF sensor and the m90. We already made a flange for the TB outlet. We're also going to remove the butterfly from the orignal TB(using an extra one before the m90) that's still on the intake manifold, and we're gonna plug up the holes on it so there's not vacuum/boost leaks.
It should all be done tomorrow, we just need to find a slightly longer throttle cable. I'll let you guys know how it went, and take some pics of the setup.
Thanks for all the help.
 
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