Thread: Yada yada, more dynos.

whoops miss-red your CR thought you were runnin the same as the other VE-T...

GT3071RWG 56.5mm turbine T25 flange in a .86AR flows 24lbs corrected turbine gas flow.


GT3076r 60mm turbine T3 flange in a .82AR flows about 23lbs.


It looks like the smaller T25 style GT3071r would definitely have less backpressure. The turbine is also smaller on this varient of the 3071r. It is a smaller 56.5mm turbine in the same 84 trim as the GT3076R 60mm.

Even with the larger turbine, the .82 still doesn't flow what the smaller GT3071r internally wastegated .86 does.

I would just love to see what this housing flows, but I have the feeling it is going to be about 15-18.

Now, I also know that the divided housing will help prevent reversion, which is why I figured it would work really well. But the backpressure from the housing just feels like it is not responding really well. Now that the log is gone, the standard cams can be used, but they still don't want to make power. The VE cams hit hard when the ex hits, so does that mean there is more exhaust restriction?

The .78 if it really flows like .39 (like a very respected DSM guy is telling me) it would really choke the engine. The great spool comes at a very steep price, but you could just say "F* the twin scroll" and get a 2871r or something that just spools better. There is only half as much gas that has to pass through each scroll, but here's where it gets a little confusing. You could have a turbo with 4 scrolls, but if each pulse had to go through a hole smaller than the exhaust port it would create a loss of power right? That's what I am thinking is going on. Since the gas doesn't flow through the turbine all at once, but goes in pulses, each pulse basically goes through a hole the size of a dime in the volute. Each pulse goes through its own .39 housing. Does that make sense at all?
Maybe it just needs 30psi of boost eh? Race gas and tons of timing. That should make good power

no prob. I could have gotten 8:1 compression pistons for all I know. All I do know is the dish on these things was huge. You could eat chunky soup out of them lol. I have some pics of the pistons if you guys wanna see.

OOOH! OOOOH! Here's a .78 divided housing from a GT3271. You can see that it flows about 20lbs, but it is also using a 64mm 73 trim trim turbine. The larger turbine still can't make up the difference from the loss of flow from the divided housing, but you would gain a bit from reversion loss. But at only 20lbs of flow, it STILL flows less than the T2 flanged GT2871r with the .86ar open housing. Even with a 10mm larger turbine wheel!



The disco potato will flow better than the setup I have now, but the compressor is smaller and can only move about 360hp. I have to try opening the exhaust up, I think it will really wake the car up!

Increasing Volumetric efficiency can make a turbo spool faster, by basically making the engine breath better. If the engine performs like a bigger version of itself, it can help to lower lag, and boost onset. I have thought about doing something really stupid and getting a 1.06 undivided housing. From one extreme to the next. I wonder how laggy the 1.06 would be compared to a .82.

Of course, higher compression engines would have a higher VE to start, and would spool a 1.06 housing much faster than my crappy 8.5:1 motor will. The difference in spool is only 2-300rpm from a .63 to a .82, so maybe it wouldn't be so bad? Maybe it won't even hit full boost lol!

I could put some 9.3:1 pistons in, use water injection like JP and make 500whp on 16psi. But that seems like a fantasy. I could rev the snot out of it too! Like 9000 to 9500rpm! Even with the .78 I need more revs, so it may benefit me to just go for it. I wonder how slow a 1.06ar on a 60mm turbine would spool... couldn't be quite as bad as a GT35r, but would be close huh?

The floe of a Turbine wheel will not be defined by its inducer/major but the exducer, you can work it out from the trim.

you are comparing an 84 trim, to a 90 trim to a 73trim therefore the size of the major is useless.

regardless of trim, even if it had a larger trim wheel it still wouldn't flow what the smaller inducer wheel would. A larger trim will generally flow more, but it isn't the only factor.

I know it isn't comparing apples to apples, but it is very close. The exducer is within 2-3mm (just a guess) , yet flows A LOT less than the .86. It is just barely more than the .64 T2 housing.

The divided housings will basically flow around where the smaller size AR would. A .78 will flow like a .48, a 1.06 divided will flow like a .63-.82. Maybe a little more than the .63, but less than the .82. The boundary layer on the divided housings is another restriction, also the rough casting. But the fact is, they flow less. Higher backpressure.

I could take the T3 flange and weld a T4 flange on there. They make a 1.06 T31 housing in a T4 footprint.

GT2871r 53.8mm 76 trim. Flows 21lbs in the .86 open T2.
GT3271r 64mm 73 trim.46mm inducer. Flows about 20lbs/min. in the .78 divided.

Someone car to calculate the turbine size so we can see how much flow is affected? Need exducer info.

I do find it amusing that you think your turbine housing is too small. a 60mm 84trim GT30 style turbine wheel in a .82 T3 GT style 3" outlet turbine housing will safely support about 575whp.

You can even caluculate this with the turbine maps based off of "X" engine displacement, VE, and then also by the map of the compressor wheel you are using.

Most people still incorrectly read compressor maps and the only idea they have to relate them into actual useable data is just the max flow of the comp wheel.

If you are going to blame your turbine wheel/ housing into being too small then you should do some research into actually how to calculate how much HP your current setup can support, as well as how much flow you need to reach your HP goals. You should also roughly be able to map out the different turbine housing sizes to find the difference in spool they will have.

It is not all just about how much you can flow through the turbine housing/wheel, its also about how efficiently the exhaust gasses transfer their heat energy to the turbine wheel to creat the power needed to make the wheel spin, and continue spinning at X rpm to creat X air flow. the .86 T2 90 trim 56.5mm wheel may flow more on paper, but it does make less power and spool slower than a .63 T3 in MOST applications.

It really seems like you need to find out for certain what your backpressure is dude. Without that there's no certainty over what's causing the issue.