Measuring stock exhaust restriction

[FWombat]

Originally Posted by VR-4ever

^Thank you.

I wasn't saying you were going for that look at all.... just replying to Chris.

I know; I was just joking. I guess my humor didn't translate well to print.

- Brian

[twiceblown]

i was looking at the differences in pressures prior to and following the turbine. If you take a look at the differential pressure, the stock exhaust shows a difference of 31psi between the header and the O2 housing (across the turbine), and the 3" exhaust shows a difference of 28psi at 7K RPM. Now, that is 31 and 28PSI pushing AGAINST the wastegate flapper! Can someone tell me how the wastegate flapper does not open at pressure differences like this if the wastegate actuator is set to 6# or slightly more depending upon # of washers or preload (perhaps mechanical advantage of the actuator- flapper size vs. diaphragm size?)?

Also, FWombat, do you have data for the 3K and below range? I'm curious to see how much variation occurs in the lower RPMs that leads to such a decrease in boost threshold or increase spool with the 3" exhaust (we've all felt the changes). Currently, at 4K, stock pressure drop across the turbine is 11.5psi and the 3" is 11.25psi. So, from those #s, i wouldn't think that any turbo that would spool at 4K or below would see any difference in boost threshold (though the practicality of this obviously is different). Am i missing something?

Damon

[mjannusch]

What boost pressure was the car making when you made those measurements?

[twiceblown]

I think he said 15psi holding 13 to redline. With those increases in differntial pressures pre and post turbine, i'm guessing that his wastegate is being forced open causing the drop in boost pressure. a log of how the boost solenoid is doing could show that, couldn't it?

[Multiades]

Originally Posted by twiceblown

i was looking at the differences in pressures prior to and following the turbine. If you take a look at the differential pressure, the stock exhaust shows a difference of 31psi between the header and the O2 housing (across the turbine), and the 3" exhaust shows a difference of 28psi at 7K RPM. Now, that is 31 and 28PSI pushing AGAINST the wastegate flapper! Can someone tell me how the wastegate flapper does not open at pressure differences like this if the wastegate actuator is set to 6# or slightly more depending upon # of washers or preload (perhaps mechanical advantage of the actuator- flapper size vs. diaphragm size?)?

That's probably about 1.4sq in of flapper area * 30psi = 42lb on the actuator rod. The diaphragm opens when you put maybe 7psi on it. The area of the diaphragm is about 2.25", or about 4 sq in. If the spring opens at 7psi, that's about 28# (7*4) that the diaphragm must exert against the spring to open. Soooo 42lb is very likely to push it open.

The above example is with his Bullseye 38mm wastegate flappers (which might have 34mm of exposed diameter). Stock TD05 flappers have about 0.8 square inches of area, while mine (34mm TRE) probably have closer to 1.1 sq in. These cases would yield 24# and 33# respectiveliy on the arm at 30psi across the turbine.

Sounds to me like a good case for upgraded wastegate actuators with STOCK TD05 flappers!

[doctorstupid]

Originally Posted by Multiades

That's probably about 1.4sq in of flapper area * 30psi = 42lb on the actuator rod. The diaphragm opens when you put maybe 7psi on it. The area of the diaphragm is about 2.25", or about 4 sq in. If the spring opens at 7psi, that's about 28# (7*4) that the diaphragm must exert against the spring to open. Soooo 42lb is very likely to push it open.

The above example is with his Bullseye 38mm wastegate flappers (which might have 34mm of exposed diameter). Stock TD05 flappers have about 0.8 square inches of area, while mine (34mm TRE) probably have closer to 1.1 sq in. These cases would yield 24# and 33# respectiveliy on the arm at 30psi across the turbine.

Sounds to me like a good case for upgraded wastegate actuators with STOCK TD05 flappers!

I know that TEC has dual port wastegate actuators. one nipple is used to hold it shut with boost before desired boost is reached, then the boost controller flips the ports so that port is no longer pressurized and pressurizes the other port which pushes the valve open. I do not know who makes them, and I've only had the pleasure of seeing them once, on a local 15G car. Currently TEC is closed for business for a death in the family, when they reopen you had better beleive I'll be in there getting some for my TD05's.

As for pushing the valve open prematurely, ABSOLUTELY! I've seen it myself while somebody else revved the engine at WOT to redline. Keeping it shut tightly could do wonders for reducing lag

[Multiades]

Originally Posted by doctorstupid

I know that TEC has dual port wastegate actuators. one nipple is used to hold it shut with boost before desired boost is reached, then the boost controller flips the ports so that port is no longer pressurized and pressurizes the other port which pushes the valve open. I do not know who makes them, and I've only had the pleasure of seeing them once, on a local 15G car. Currently TEC is closed for business for a death in the family, when they reopen you had better beleive I'll be in there getting some for my TD05's.

As for pushing the valve open prematurely, ABSOLUTELY! I've seen it myself while somebody else revved the engine at WOT to redline. Keeping it shut tightly could do wonders for reducing lag

THEY MAKE THEM FOR TD05s?!?

-Chris

[twiceblown]

okay, Chris, so with the #s you supplied for flapper and diaphragm area, i come up with:

flapper diameter / diaphragm diam / Flap Area / Diaphragm Area / Stock Actuator Spring Pressure / Turbine Housing PSI / Flap PSI / Diap PSI / Ideal Actuator Spring Pressure

34.00 57.00 1.41 3.96 7.00 30.00 42.23 27.70 10.67
38.00 57.00 1.76 3.96 7.00 30.00 52.76 27.70 13.33

For the two sized flappers assuming that there's a 7psi spring in there, Chris should upgrade the spring rate to 10.67PSI and Brian should upgrade to 13.33PSI for ideal considitions (equilibrium between intake manifold pressure * diaphragm area vs. flapper area * turbine pressure). NOTE: this is assumed to be with the same setup as FWombat.

Anyone have the sizes of the flapper and diameter of diaphragm of the TD04 stuff? I'm curious for what i need. I know 9# springs are much better than stock 6#ers, but i'd dying to know what would be ideal.
Damon

[doctorstupid]

Originally Posted by Multiades

THEY MAKE THEM FOR TD05s?!?

-Chris

I sure think so, in fact I beleive the ones I saw were modified TD05 flappers made to fit on TD04s. Not sure on that, but I'm sure they could be modified. Hell, they might be for Garrett turbos, but they can be made to work, i'd be willing to bet on it

[twiceblown]

i figure that if exhaust pressure is directly related to intake pressure, then increasing boost from 1bar (2bar absolute) to 1.5bar (2.5bar absolute) [25% more exhaus] then manifold pressures at 22psi would be approximately 40PSI. That means that according to the above measurements,

34mm flapper would require 14.2psi spring
38mm flapper would require 17.8psi spring!!!

All just to provide enough seat pressure to keep the flapper closed while boosting!!!