333pg333

He writes from the heart and he has no teeth and I think this comes out in his posts.

333pg333

Yeah but you can make Apple pie from Chokos don't you know...

333pg333

I used the Tial 38 and it jammed shut on the track. Car boosted to 2.1 bar and should have blown up. Somehow it didn't. Switched to the LR one and had no probs even though it doesn't have so many fans on this board.

Duke

I found him!!

Spidey944

LOL! ^^^

TurboTommy

The smaller the hotside, the less of an efficient flow machine it becomes. The turbo will spool and turn quicker, but it takes more and more exhaust energy to do so. Therefore less exhaust needs to go through the wastegate (I know it's a little counter- intuitive). Also, higher back pressure will force exhaust easier through a relatively smaller wastegate valve. So, a larger hotside (especially with lower boost applications) needs larger wastegates so that the exhaust can find an easier path than the nice high flowing turbine (because if it has an easy time going through the turbine, boost creep will result).

ritzblitz

Although it is pretty confusing how you wrote it, I'm pretty sure that theory is correct. I don't believe backpressure is the correct term for what you are describing though, that part was confusing to me.

Less Boost = Larger Wastegate. Why? Because more exhaust has to be diverted around the turbine wheel to prevent boost creep or overboost of the turbo.

More Boost = Smaller Wastegate. Why? Because more exhaust has to spool the turbine wheel to create the high boost pressure, therefore, less exhaust has to exit the wastegate.

Hope this makes sense.

TurboTommy

There's exhaust pressure between the exhaust valve and the turbine. Anything in between these two points sees this pressure. I think the right term is Turbine Inlet Pressure. Most people just say back pressure.

DrZ1

I had a conversation w/ Tim(SFR) today, not so much on the great debate here. But what would be best for me on a 350-400 hp motor in track car. He stated the 46mm are heavier built and more applicable to the track and higher boost lvls where as 38mm better for street. Did not spend much time debating the diffences. I ordered a 46 for the track.

Steve

333pg333

So you're saying that with a higher boost application we should use a smaller wastegate and visa versa? I don't think I've heard this before.

gt37vgt

thanks for all the kind words so tommy seems to be saying that the smaller hot A/R needs more pressure to say on the boil than the big ones so you there for "waste" less pressure . I think perhaps one could get buy with small on small but there would be no disadvantage of a big WG unless inadequate spring pressure giving creep. After all is is a fast acting closed loop control circuit the valve oscillates like crazy its not realy to small until it's at full duty and boost is running away.
any how i have bodies to depose of .
And Pat i do have teeth I made them myself from old Del West titanium valve stems

ritzblitz

Heres a link with some information and graphs.

http://www.fftec.com/WastegateSizing.html

gt37vgt

a good link and kind of shoots down tommies theory but i can imagine how a small AR would require bigger pressure differential across the hot side housing to maintain boost .

pk951

My Swiss has some good prices on WG

http://us.europartsetc.com/inventory...01&category=76

Duke

Yes that is totally correct.
You need the largest wastegate when you have high cr, big displacement and low boost.

To run high boost pressure on a small engine you need to send a larger percentage of the available exhaust gases to the turbo - hence less gases need to flow through the wastegate.