Boost control theory

[good2win22]

i have some ideas about the exhaust gas drive pressure through the waste gate hole on the turbine side and wanted to bounce them off you smart guys.


When the compression is increased in the cylinder does this correlate to higher exhaust pressure/volume? 


If so, would the waste gate hole size on the turbine housing need to be enlarged for the higher pressure/volume of air moving thru the turbine housing to be able to control the boost?


The reason I am posing these questions is that I have not been able to get the boost on my car below 20 psi with this 6262 and precision .63 housing.  The waste gate hole has not been opened up. I put a stock actuator on it this evening and was still unable to get below 20 psi boost.

[Steve Wood]

Increased compression creates a hotter exhaust gas which in turn creates a larger volume trying to escape thru the wastegate.

Seems like some of the smart guys advocate hole a little over 0.90"...maybe 0.96"?  Drop Brad a note and I think  he can quote Patrick from PTE on the exact size.

It's really a complex situation because the exhaust wheel/design controls the amount of back pressure holding the exhaust flow back in the engine and that has an affect on boost control as well.

Shape of the wastegate hole (thinking of the radiusing, if any, on the back side) has an affect as well.

I am not surprised to find that you are having problems getting it under 20 psi and of course, if you are running an HD actuator, it is not going under 18 without finagling a lot.

[good2win22]

After some thought, talking to Brad and Bison, me and the daughter sat down to do some algebra. I needed to figure out how to open the waste gate hole by 30%. Not as simple as you think and because the internal gate opens in an arc that plays into it as well. Now I understand why the external gates are so more precise with boost control.  I enjoyed the talk with Bison.  He talks my kind of language. Precise, to the point and technical.  All the stuff I needed to know


Anyway, pulled off the turbine housing and opened it up to 1.1" and radiused the inside like working the bowl area on head.  Put it back together with the stock non adjustable actuator and went for a test run.  Made a high gear pull and boost settled at 13.7.  Now I can work my way up and tune at my comfort level.  A little piece of mind

[motorhead]

Orientation and orifice size have a huge impact on flow and control.  You did the best you could without running an external WG. 

I just got a sample of the lastest calculations I need to master in order to become a "Laser Safety Specialist" last night - it is no wonder I was tossing and turning in bed for countless hours (brain wouldn't shut down).

[TexasT]

Did you take any pix of your handiwork? Are you using a large waste gate puck? Did you have to ofset the hole any to keep the hole under the puck?

[TexasT]

Orientation and orifice size have a huge impact on flow and control.  You did the best you could without running an external WG. 

I just got a sample of the latest calculations I need to master in order to become a "Laser Safety Specialist" last night - it is no wonder I was tossing and turning in bed for countless hours (brain wouldn't shut down).

It is just numbers. They equal out in equations. Just have to do the operations in the correct order and correctly . My dear aunt sally or something along those lines. Please excuse my dear aunt sally

Please. Parentheses
Excuse. Exponents
My        multiplication s
Dear.    division
Aunt.    addition
Sally.    subtraction

[Steve Wood]

LOL

[good2win22]

Did you take any pix of your handiwork? Are you using a large waste gate puck? Did you have to ofset the hole any to keep the hole under the puck?

No pics of the handiwork. I am using a large puck. Yes, had off set the hole to keep it under the puck

[daveismissing]

calculations I need to master in order to become a "Laser Safety Specialist" l

Sea Bass?