1UZ Legacy. Supercharger will not boost over 3.5psi Help.

[V8MX5]

Im stumped.
Customers car in at work. Supercharger will not go over 3.5psi

Specs are as follows.

Stock LS400 series 1, 1uz engine with stock headers.

Megasquirt ECU with RX8 injectors and wasted spark ignition set up.

TBS "the blower shop" Billet 671 Supercharger.

Running a 30 tooth crank pulley and 38 tooth top pulley.

AEM water/methanol injection system.

Twin 4 barrel carburetors above blower (used as throttle bodies only)



Using calculations provided to us by the supplier and various references from the manufacturer we should be producing between 8 to 12 psi.


The most we can get is 3.5psi.
The vehicle was dynoed last week with 260hp at the wheels.


Any help or ideas would be appreciated.
We are at a loss as to whats wrong.

 

[V8MX5]

Picture showing intake manifold during the fabrication process.
And bottom picture after we got it running.

 

[cribbj]

Is it running with a bypass valve? If so, I'd check to see if it's leaking.

 

[V8MX5]

Does not run a bypass valve.

 

[Jef]

The stock headers will be restricting the flow of the engine and limiting boost. Also check if the mufflers and cats are not blocked

 

[stevechumo]

Does the manifold plate restrict the flow evenly? It looks like it blocks/separates the front and rear ports.

 

[American Locomotive]

If you're 100% sure there are no boost leaks, than there are only 3 possible causes:
1. Throttles too restrictive/not opening up fully
2. You're just not spinning the blower fast enough
3. The blower is bad and leaks too much past the rotors

 

[ivan129]

That's an awful big blower to be only pushing 8 - 12lb. I have a M112 on my 1UZ and I get 12lb no problems but the intake air temps are off the planet. Do you have after market cams? If they are aftermarket NA cams then you maybe loosing boost during overlap. Blower cams usually have a wider lobe centre and much less overlap. I found this out the hard way. Cams for a 1UZ are not cheap.