How much exhaust back pressure for TRD supercharger?

To skip all the reading below, how much backpressure should a supercharged engine have under full throttle?

I have been trying to track down a power loss problem on my 03 Tacoma with a supercharger for several months now. Nothing I have tried has helped. Feels like I am towing a boat anchor up hills. Requires much more boost than usual to drive. Feels like I am fighting the truck to get it too accelerate. Engine is also running a little hot and drinking fuel. I have changed plugs, air filter, wires, fuel filter, fuel pump, injectors, MAF, cleaned throttle body, run sea foam, timing belt, dynamic tensioner, s/c belt, nose cone, bypass actuator, cleaned bypass valve. No engine codes. Only definite problem that I can find is that bypass valve closes slower than normal when throttle is applied. It takes a sec or two instead of being instant. It also doesn't close completely accept under full throttle and a couple of secs.

Mechanic on Expo recommended getting catalytic converter checked. They said it was fine. Several more months and more money and still have the problem. Take to said mechanic and he says he got 12 psi on his gauge under load while driving around. Take it to muffler shop to get cats replaced. They double check and can only get 5psi under full throttle on lift. Hold off on replacement.

Mechanic insists that he got more and tells me to drive it while monitoring pressure. Make little part to mount into 02 sensor hole with fitting. Drive around with buddy holding gauge inside cab. Only a couple of lbs with normal driving but it pegs out at 10psi (my gauge max) under full throttle at high rpm.

I know normal for a N/A vehicle is around 4-5psi under load. Should a supercharger engine have that much more backpressure? Hoping to get this truck running right and considering gutting the cats to see if this is my problem. Don't want to waste them if I don't have too.

Btw, I have driven the truck around with just straight headers but couldn't tell a perfromance difference. Didn't let the computer reset so I am not sure if that would affect it.

 

Forgot to add, it is a 3.4L.

And before any one freaks out about gutting the cats. It is only temporary to check before having to drop a chunk of change on a new exhaust system. I don't wanna hurt poor Mother Earth.

Also don't wanna start another debate on back pressure vs no back pressure as far as performance. I am just looking for someone that knows about the numbers or has knowledge of a supercharger increasing backpressure significantly or not.

Thanks, gentlemen!

 

Thanks for all of the replies! Lol.

Gutted the cats, have 6psi max now. Truck runs a lot better. Figured someone might find this useful down the road.

 

Thanks for the feedback. Ive been looking into a high flow exhaust myself with cats and everything.

 

Im not a Hippie Treehugger so Im definately not gonna flame you for gutting the cats lol.You want close to no backpressure while running a Supercharger.If a Converter is partially clogged that will kill the performance of any blown motor.A clean high flow Converter wont hurt the performance that much.My tacoma isn't Blown but my 92 Coupe Mustang is and is pushing over 500+ to the rear wheels.I have been down this "supercharger" road many years now.

 

Any tips on your temporary o2 bung turned boost gauge setup? I have a TRD boost gauge, and AEM wideband (sensor hard to get to) and am very curious what my back-pressure is. Would be cool to run a quick temp setup to use my boost gauge to tell me what that is.

 

I didn't use my s/c boost gauge. I used a vacuum/pressure gauge that I bought at Advance Autoparts. I made a little fitting using a piece is sheet metal, a threaded elbow, and the o2 sensor gasket as a template. Hook the gauge into 6ft of vacuum hose and into fitting that fits into the slot for the front 02 sensor. With 6ft you could have it inside the cab so you could look at it by yourself.

 

Good Info, Any updates? I know my cat converter is dying and will have to replace it soon and will be looking for something OEM or high flow but being in California will make it hard to find something decent.