Thread: Waste Gate

Originally Posted by clean32

Come on guys im being serious here. if I have a .32 AR sitting in front of a .65 AR, I need some way of getting the large volume of gas around the .32AR very important, more so if the .65 waste gate ever opens, I don’t want massive over run and a small shrapnel producing device under the bonnet, the ,32AR waste gate gives only 1.34 cm2 I need in total about 4.5 cm2

0.32 is a tiny exhaust housing. I have a 0.36 around here somewhere, originally off a Nissan CD20T.
So you're running a compound turbo setup and want to bleed enough exhaust around the little one? Small turbos in a compound setup are often similar size to a single turbo on the same engine. So you're winding the snot out of a small diesel?

I don't think you'll need a particularly big wastegate (doesn't a turbo that small already have an interna?) as the volume flow through the little turbine will be much smaller due to the higher pressure. Wastegating the little one could be counter-productive unless you're also bypassing the small compressor on the other side.

Unless I'm barking up the completely wrong tree.

Originally Posted by catch-22

I have never known a wastegate to be measured in A/R....

suring waste gates in AR

sheesh, I am not measuring waste gates in AR, I am measuring turbos in AR cool end, I measuring waste gate in cm2 because that’s how much of a HOLE I have calculated that I need.

And as this was a bit of an oversight originally on my part, with the turbos ordered. Even the yank boards id it as a problem, but then they just push more in and under fuel to keep the pressure and EGT down.

now Im curious.....

you running your twin turbos in series or parallel?

OK...I had to read your post a couple of times to kinda get it...

Can you explain your setup a little more please? Are you running twins?

Originally Posted by Dougal

0.32 is a tiny exhaust housing. I have a 0.36 around here somewhere, originally off a Nissan CD20T.
So you're running a compound turbo setup and want to bleed enough exhaust around the little one? Small turbos in a compound setup are often similar size to a single turbo on the same engine. So you're winding the snot out of a small diesel?

I don't think you'll need a particularly big wastegate (doesn't a turbo that small already have an interna?) as the volume flow through the little turbine will be much smaller due to the higher pressure. Wastegating the little one could be counter-productive unless you're also bypassing the small compressor on the other side.

Unless I'm barking up the completely wrong tree.

My high pressure turbo (BorgWarner K16) is larger than the stock single turbo. It has a 5.35 cm^2 turbine housing.

I don't believe it should be significantly smaller than the stock single. And it should still provide higher boost at lower revs than the single turbo.

The low pressure turbo (BorgWarner K27.2) has a 12.5 cm^2 housing.

The wastegate on the high pressure turbine discharges into the inlet of the low pressure turbine (along with the exhaust from the HP turbine).

I was not intending to also bypass the HP compressor.

Originally Posted by clean32

yes but big ugly and vent, i realy need to bypass back into the dump pipe,

what you have posted looks like a over boost thingy.

That example is on a larger engine than I expect to see in most Land Rovers.

I believe it is an external waste gate.

Originally Posted by Bush65

My high pressure turbo (BorgWarner K16) is larger than the stock single turbo. It has a 5.35 cm^2 turbine housing.

I don't believe it should be significantly smaller than the stock single. And it should still provide higher boost at lower revs than the single turbo.

The low pressure turbo (BorgWarner K27.2) has a 12.5 cm^2 housing.

The wastegate on the high pressure turbine discharges into the inlet of the low pressure turbine (along with the exhaust from the HP turbine).

I was not intending to also bypass the HP compressor.

Do you know the wheel sizes in your BW compound setup? The wheel radius and the housing A/R ratio gives you an equivalent area at the wheel tips which seems as close to a universal turbo sizing number as I've found.

Is the wastegate on the smaller turbo sensing total boost or the boost from the larger turbo?

There are some setups which start to bypass the small turbo as the larger one picks up. A wastegated little turbo gets part way there but they're bypassing the compressor too.
This one bears the same name (R2S) as yours, but the function varies.
.

Originally Posted by Dougal

Do you know the wheel sizes in your BW compound setup? The wheel radius and the housing A/R ratio gives you an equivalent area at the wheel tips which seems as close to a universal turbo sizing number as I've found.

Is the wastegate on the smaller turbo sensing total boost or the boost from the larger turbo?

There are some setups which start to bypass the small turbo as the larger one picks up. A wastegated little turbo gets part way there but they're bypassing the compressor too.
This one bears the same name (R2S) as yours, but the function varies.
.

I will try an explain it.

Think back over previous posts here, to get EGT down, you back of the fuel or push in more cold air. OR as EGT and EGP is caused by back pressure at the turbo housing, the easiest way is to just dump some of this gas, but once you start to do this it limits the air you can pump. OR you fit a bigger housing which we know will lift the RPM before there is boost. simple really


So small turbo working at max, second larger turbo spools up, but now the second larger turbo has a problem, it cant get rid of any more hot gas than the down the line small turbo can, this is the limiting factor. So as you said you need to start to bypass the smaller turbo.

Another thing to remember and is forgotten often, I will try to explain it another way. WW!! war movies, the spitfire is flying along, spots the Nazi, tally ho wing over into a dive. Cant do that in a jet though, no propeller. even if the prop is spinning at max revs it will act like a air brake if the plane is diving faster than the bite X rpm of the prop, a little different with a centafugal, but if the cool side spins to fast or the air gets to soft( hot) the flow will delaminate off the back face of the blades, interfering with the front of the next blade. LOL a bit like a Harvard at full tip RPM.

Any way at some point in the rev range I have calculated that I will need to dump hot gas, 2250rpm