As some of you may know, my turbo was hitting the factory overboost almost instantly (by 3500 RPM) in 3rd and 4th (and would most likely do the same in 5th if I had enough road and big enough gonads to keep my foot in it).

When I bought my car the sensor was just grounded out, and the car was running super rich, but thats another story.

After doing some research and asking some questions (thanks Criag), we pulled the Tial off and hooked up a guage and tried opening the WG with compressed air. Well, lets just say it wouldn't open very easily. So once the WG was carefully put in a press (since we weren't sure what kind of spring was in it) it was taken apart. Thanks to Steven and his son at Poudre Sports Car for putting my car on the lift and doing all of this for free.

There was a large green spring and a small red one in there. After doing some searching, the green is .8 bar, and the red .3 bar, so my car had a total of 1.1 bar springs in it. That easily explanined the overboost I was hitting.

Once we took the .3 bar one out, and re-installed the WG, we hooked up a temporary boost gauge and tooke the car for a spin. It ran great, the gauge went to 15 psi, and it would peg it extremely quickly, but you could hear the wastegate opening.

As help for anyone else that buys a car a Tial, I have posted a chart that breaks out the colors of each spring.

Bill

 

Wouldn't that still be overboost?

.8 bar spring and you are saying you are seeing 1.05 bar on the gauge.

Please elaborate.

Ryan

 

It is borderline. From everything I have read, the overboost solenoid kicks in between 1.1 and 1.4 bar.

I think I am seeing the higher boost due to the B&B headers and .8 bar spring. I am going to move the verboost sensor from the intercooler to off the intake (similar to what a fellow rennlister did not too long ago).

I also have a .7 bar spring come from IA, so I might go ahead and install that too.

I have done some runs in the car, and it hasn't cut out, so thats better.

Is that what you were asking?

Bill

 

Why don't you just use a softer (or original) spring and install a manual ($30) or electronic ($150) boost controller? That way you can increment or decrement the boost level finely until you get a level you want - and no taking the wastegate apart to add or remove springs.

I don't understand the obsession with changing springs on these cars when a $30 device does the same job and is much easier to alter?

 

I like the idea of sticking with a specific spring rate and tuning it on dyno with matching AFR's/CO; this way no one can crank up the boost and lean the engine out...

 

Drew summed it up perfectly.

 

But you would do that anyway with a boost controller; you just have much less work to do (and chance of snapping bolts!) than taking the wastegate apart.. you can also turn it down if you get bad fuel, summer heatwave, overboost during a cold-snap, running problems etc.