TRD supercharger only making 4-5psi?

[djskorch]

So ive had my SC kit on for about 2 months and love it. Truck is much faster and almost identical to the ones i can find on youtube however....

I bought a Godspeed boost gauge new off a buddy and was only reading around 4-5 psi. I though ok its a cheap gauge and is just reading off a little.

Last night I bought an Autometer phantom series and low and behold, still only 4-5 psi. vacume is 15 at idle and 20 when "cruising down in gear".

Any thoughts as to why im 2ish psi below what should be stock?

 

[djskorch]

And yes, i did use the correct TRD throttle body gasket.

 

[BigFishAllDay]

You've got the 1st gen S/C right?

My first suspects would be:

1. S/C belt is slipping on the S/C pulley

2. Bypass valve is leaking

 

[djskorch]

You've got the 1st gen S/C right?

My first suspects would be:

1. S/C belt is slipping on the S/C pulley

2. Bypass valve is leaking

Yep I have the 1st gen.

I have never heard the belt squeal like it is slipping. It was a brand new belt when I put the SC on.

I just messed with the bypass valve by wiring it completly shut and got 0psi under full throttle(forgot how lumbering the truck feels without boost haha)and wired it fully open and still right about 4.5-4.8psi.

 

[BigFishAllDay]

RE the belt:

The fact that you can't hear it, does not mean it is not slipping. And although it's a new belt, you may not have the tension set properly.

(Assuming you are running the old style plate tensioner w/the fixed pulley) you'll need to check the belt tension with a tension meter. If you don't have one, you can eyeball the tension and just keep an eye out for black dust forming on the nose cone (which would indicate belt slippage). If you are running the dynamic tensioner, what kind of mileage is on it? The dynamic tensioners do lose their tensioning strength over time.

RE the bypass valve:

I don't think you're looking at the right part. The bypass valve is not electronic, so it cannot be "wired" to stay open or closed. It is a vacuum actuated part that responds to intake manifold pressure/vacuum.

Also, on the bypass valve... full shut = full boost, full open = zero boost.

Bypass valve:

 

[djskorch]

RE the belt:

The fact that you can't hear it, does not mean it is not slipping. And although it's a new belt, you may not have the tension set properly.

(Assuming you are running the old style plate tensioner w/the fixed pulley) you'll need to check the belt tension with a tension meter. If you don't have one, you can eyeball the tension and just keep an eye out for black dust forming on the nose cone (which would indicate belt slippage). If you are running the dynamic tensioner, what kind of mileage is on it? The dynamic tensioners do lose their tensioning strength over time.

RE the bypass valve:

I don't think you're looking at the right part. The bypass valve is not electronic, so it cannot be "wired" to stay open or closed. It is a vacuum actuated part that responds to intake manifold pressure/vacuum.

Also, on the bypass valve... full shut = full boost, full open = zero boost.

Bypass valve:

View attachment 60539

lol yes i know what the bypass valve is. i didnt mean "wired electronicly" i ment wired the pushrod on the actuator so it was either fully opeb or fully closed.

no black "dust" around the nosecone. old style tensioner and tension is similar to other pullys

sorry abouy mistakes im on my phone typing this.

 

[BigFishAllDay]

Here's the thing.... There is the potential that the sealing surface on that bypass valve either has wear, or machining irregularities, that prevent it from completely sealing. This will create a boost leak and will bleed off your boost pressure.

Your "wiring" test does not exclude that as a possible cause of your issue.

How man miles on the S/C since you installed? That dust takes a while to build up. You say tension is similar, which to me reads: you eyeballed it.

So basically, you haven't ruled out either of the two causes I suggested.

If you're one of those paranoid types that always thinks it's the worst possible problem... how's this? The rotors in your S/C could be worn to the point that the gap between them prevents them from developing the standard boost pressures. In this case you'd need new rotors/a rebuild on your S/C.

Start by eliminating the easy stuff. Check your belt tension. Check the bypass valve to make sure it's sealing properly.

EDIT: Check out this link for a good read on ALL the various causes of low boost on a S/C. It's good info for current and prospective owners of TRD S/C setups.

"Low Boost Causes & Cures" > http://kennebell.net/KBWebsite/Common/pdfs/LowBoostCausesAndCures.pdf

 

[that$pit]

Not to be a thread hijacked, but speaking of SC rebuild, where do i find the parts?, Toyota?, and with the supercharger on it, I have to put it back together before driving, I can't (shouldnt) drive without nose cone put in, correct?

 

[IanB]

Not to be a thread hijacked, but speaking of SC rebuild, where do i find the parts?, Toyota?, and with the supercharger on it, I have to put it back together before driving, I can't (shouldnt) drive without nose cone put in, correct?

I believe they are Eaton M62 units, you should be able to get rebuild parts from Eaton directly.

 

[djskorch]

Thank you for the input and link BFAD. I will look into both of those.