I've been having some problems with a particular 38mm wastegate (boost creep to be exact) and before I send it back to see if its malfunctioning, I wanted to see how it actually works so I can better understand the problem at hand. During my quest, I found a discrepancy that might help explain the issue.

At idle / normal driving / below the intended psi, the wastegate stays shut as pictured:



Now, once the desired boost level is obtained, the wastegate opens to allow the excess exhaust gases go out the dumptube and finally to the atmosphere / exhaust depending on the design of your system. However, when checking the fully open position, I came to the realization that the wastgate valve only opens approximately half way of the 38mm deisnged dumptube flange; it doesn't take an engineering degree for me to see that the design (if this is what was intended) is poorly designed at best (I bet most WGs on the market are like this). Now I understand it is hard to get the valve open all the way, but using ~50% of the opening seems like its just asking for creep issues if the exhaust gases require more then ~19mm of opening.



With some further investigation I see that there is a lock washer thing that is preventing the valve from opening any more. I looked through the instructions and it is one of the parts that is in the correct place. Why not just remove it to get a few more mm's of valve travel?:





If this is all the case, it seems that the biggest reason for getting a larger wastegate is not the diameter of the wastegate (although I guess that plays a role) but rather the TRAVEL DISTANCE of the internal valve.


Would someone like to share some ideas?

 

Dude that thing is toast.

Hook it up to an air compressor, the valve should open all the way.

At least it does on my Tial 44

Is that a tial?

 

Thats the thing, with the lock washer in place, it physically cannot open all the way.

Why would they have the lock washer there to prevent full movement of the valve???


This is not a tial.

 

Sorry then I do not know, I do however know that mine opens all the way

 

valve diameter and travel distance of the valve are dependent upon each other. A smaller diameter valve will have to have more travel than a larger diameter valve to be able to handle the same amount of air. The larger diameter valve would not need to travel as much as a smaller valve to handle the same amount of air. Pretty sure this is how it is, let me know if this makes sense! Same idea as a BOV.

 

how did you get it to open up that far in the pics?

 

Yeah I understand but why doesn't the valve open all the way in the first place? It seems like a lot of wasted space / marketing gimmic saying the hole is 38mm but if the valve doesn't travel the whole 38mm why even bother?

 

I removed the spring so I could easily push up to see maximum valve lift.

Otherwise, it would be a combination of the pressure differential and the force of the exhaust gases on the valve that would open the valve.

 

is the 38mm measurement the inlet (valve side) or outlet, or both?

I don't think the valve needs to open fully to make use of the xxmm size opening.

 

Its 38mm for both inlet and outlet. I also see what your saying but the wastegate is basically a giant 90 degree elbow and because of that, it seems the larger the valve is open, the more total flow it could handle.

By only allowing the valve to open ~19mm out of a total of 38mm, it seems the 38mm is just a advertising gimmic the same as even though crank horsepower is 300, the actual used horsepower is just 250 (for example).

I personally think the WG could flow so much better if allowed to open all the way but again I didn't design this.