Is 14 PSI of boost low for a TO4B ?
 

I finally got my fuel system up to par and can now crank up the boost. My turbo is a TO4B with a P-trim wheel (can't remember A/R ratios right now) but with my wastegate line unplugged I'm only getting 14 PSI. Should that size turbo make more boost than that ?

really depends on your compressor wheel size not your turbine wheel.

What gear?


But why are you running around without the wastegate line hooked up?

just my imagiantion. or it will run the boost,that your wastegate spring is,since its not hooked up to a boost controller???

It sounds like it is just running off the wastegate spring...

Something is wrong.
Either you have a big restriction in the system, or your turbo is bad.


-Ted

That's in 4th gear, I have the line pulled trying to get the wastegate not to open, it's a Tial 38mm gate with a small green spring which is about 7 PSI. According to Tial the spring is your minimum boost pressure, but I'm with you guys who say it sounds like I'm pushing the spring open. So do I need a stiffer WG spring ? I seem to get a different answer from everbody that I call.

Is there two nipples on the wastegate? Have you tried attaching to both?

yes there is, and yes I tried both of them and no difference between the 2. A Tial dealer told me that for a manual boost controller it should be on the port on the side of the WG.

Here's how you eliminate the problem of the valve actually opening on sheer spring pressure...
Connect a vacuum hose from the side fitting to the top fitting.
If you don't get higher boost, something else is wrong.



-Ted

Ok I try that this weekend and see what happens.

it should make WAYYYY more boost than that if its a shut wastegate. I'd be extremely careful testing it though, if it all the sudden starts boosting like it should you're going to grenade the engine. another thing to consider is any exhaust/manifold/turbo/wastegate leaks. make sure all the exhaust is going through the turbo or the open wastegate, none leaking between flanges.

Oh I will be very careful watching the boost guage to make sure I don't overboost it. The only small leak I have is a real small flutter right at the V-band clamp, but once it comes up off idle I think the exhaust passes it to quickly to really leak anymore. At least that what it sounds like cause the exhaust leak sound goes away. I'll have the car up in the air tonight to pull the downpipe and try to seal that v-band flange as well as put in a stiffer WG spring that I got my hands on last night.

Well I was able to get the v-band clamp and flange to seal a little better but not perfect. I did put in the stronger Tial spring and that made a difference for sure, not sure how much yet but before I'd get 14PSI in 4th gear and last night I hit 15 PSI in 2nd gear and then got my foot out of it cause I need to turn my fuel up some more. Thanks for the input guys.