WG tests

[soxnail]

Yah, I was only referring to the rise in exhaust pressure at the last part of the graph without a rise in the turbine output. As the exhaust pressure is still going up, it probably means that the WG did not open yet....
Sox

[nize]

that could also be the back pressure caused by the restriction in the turbine itself.

[soxnail]

So the car is growing sensors like weed...
Results of the last run with MAP, Compressor outlet to inter-cooler, cross pipe to turbine inlet and turbine outlet to the exhaust all being monitored.
Points of interest:
-Boost as seen in the Manifold goes to about 12 psi and holds pretty steady till I got off the gas.
-Compressor outlet pressure to inter cooler at the banjo bolt showed that the the plumbing eats up about 2 psi.
-Back pressure in the exhaust was as high as 3.5 psi, that surprised me, I expected my exhaust to flow more freely.
-Pressure at the turbine inlet as seen in the cross over pipe got up as high as 45 psi, seems excessive to me ??
I have not done the ratios yet as I am still trying to figure out which formula to use.
The one for pressure ratio to calculate the turbo charger is pretty straight forward, but the the expansion ratio for the turbine and the efficiency for the turbo out (boost) vs. pressure at the turbine inlet is more involved.
Any words of wisdom would be appreciated.
Thanks Sox.

[soxnail]

No words of wisdom ???
Does any one have any data on back pressure in the exhaust ?
3.5 psi seems pretty high.
Thx Sox

[nize]

i'm not sure anyone has extensively measured the turbo back pressure and exhaust pressure but i do recall what was important was the boost vs. back pressure ratio. it looks like you have around 3:1 ratio which does seem a bit high but not excessive.

[soxnail]

Thanks Nize,
I am wondering how much of th 45 + psi I see in the Hot side inlet is due to the 3.5 psi on the outlet of the turbo.
The turbo spins freely and there is no play in the turbine spindle.
No damage that I can see in the compressor wheel. It should be good for 15+ psi (K26 #6) original.
Interesting side note I am in Crested Butte CO. It takes 4 psi on the boost before the car's gauge shows 1 bar. I am at 11000 ft.
Thx Sox

[soxnail]

So further on this...
Putting the 3 inch exhaust fixed the back pressure in the exhaust issues, it is negligible now. Also my back pressure at the turbo went down. The ratio now stays at 1.5 or so.
Couple of interesting observations.
When I test with just the spring (10psi) and no control from the boost controller allowing the exhaust to push open the WG I got the following. The y axis is KPA and the x is 100ms each. Notice the exhaust back pressure and the boost are almost 1:1. the range is 3k rpm to 5k.



The second pic shows the same as above but with the boost controller always allowing full boost pressure to the top of the WG, so it should be spring + the boost holding the gate. The net gain is about 1.3 psi, but the back pressure goes up quite a bit. Also the boost peaks at about the same spot.



Finally the last one is with the boost controller modulating the WG at a15hz PWM. There does not seem to be any obvious difference.



So as the turbo should be able to produce more boost than 11psi or so it is showing I think either the gate is leaking (but then why the increase in back pressure with no increase in boost ?) or the turbo is petering out ?
Will try to close off the WG manually and try VERY BRIEFLY to see if I get more boost.
Sox

[nize]

maybe your BOV is leaking boost? time to get a billet aluminum BOV! arr! arr!

[nize]

by the way, i'm glad the 3" exhaust fixed your original backpressure issue. did you figure out if the original exhaust was collapsed on the inside?

[soxnail]

Originally Posted by nize

by the way, i'm glad the 3" exhaust fixed your original backpressure issue. did you figure out if the original exhaust was collapsed on the inside?

It was not collapsed, but had some serious dents that restricted it.
Sox

[soxnail]

Originally Posted by nize

maybe your BOV is leaking boost? time to get a billet aluminum BOV! arr! arr!

Yup already use one
The issue was the ICV, so will post on that old thread.
Sox

[nize]

FYI i've reversed the billet BOV orientation (boost enters on bottom, releases through side) so that spring + boost pressure holds it shut, so in case the control line fails it will always open.

[Molton]

Pressure-ratio between turbine-inlet and intake-manifold boost-pressure is not direct or linear. At low-RPM and low boost-levels, ratio will be < 2:1. At high-RPM and high-boost, it will be > 2:1. Also varies by turbine-size with larger TurboS K26/8 turbos operating at lower ratios than K26/6.

[soxnail]

Originally Posted by Molton

Pressure-ratio between turbine-inlet and intake-manifold boost-pressure is not direct or linear. At low-RPM and low boost-levels, ratio will be < 2:1. At high-RPM and high-boost, it will be > 2:1. Also varies by turbine-size with larger TurboS K26/8 turbos operating at lower ratios than K26/6.

Yup I see that..
Thanks Sox