nemsin

iTrader: (19)

Sierra Sierra, Nemo Racing, Tilton Interiors, and SVA Evos all chose to go with TS turbos. I just don't buy the SS "for lower back pressure and higher top end" rational.

03whitegsr

iTrader: (8)

From experience on a 2.2L GT42R car, 1.01 vs. 1.15 A/R on the dyno, you almost couldn't tell the difference between them on spool, the 1.15 just made more up top (20-30 WHP).

On the street though, it was VERY noticeable on transient response.
Dynos don't always tell the whole story.

URQaudiguy

Well, if there was a open scroll 1.05 or 1.45, they might. But there isn't, so you are stuck with an anemic .83A/R gasket spitting t3 frame if you want open in the bigger sizes. Huge fail on treadstone to make their open hotside a .85 as well.

altrix99

If you look at the graph, peak torque and subsequent power calculations are very similar. Its basically in the same point on that particular graph EXCEPT under 3.3kish. After that, its basically a wash until right before 5k where the .85ar open scroll just keeps holding more torque. I understand what you're getting at but boost recovery up in the peak torque and beyond area is not as important as volumetric efficiency as you just simply make more power per psi with the larger housing and recovery time will not be great enough to pull away...


If you look at the STI graph, again, its not all about top end... Look at the boost graph, they are only separated by 100rpm's @ 20psi... by 3.3k, the .85ar housing has caught up...


Agreed


Again, look at the boost graph. You have to realize that you are comparing a smaller twin scroll housing to a larger open scroll housing on a very light turbine wheel. Still, the boost curve is very similar. Look at the inherent waviness of the twin scroll boost curve. This tells you that it is struggling with backpressure as boost tumbles...

I'm realizing why the 7163 aren't offered with a slightly smaller A/R open scroll housing (.72ar or so). I think it would embarrass this twin scroll housing everywhere..

Construct

iTrader: (4)

I don't know why you're still arguing against the twin scroll setup for certain applications.

That's not the point. I don't care if peak boost is only 100RPMs apart. I do care that I have an extra 50 ft/lbs of torque down low, which is a huge gain.

Trust me, I realize all of that. But I don't think you realize that you can't directly compare twin scroll and open scroll aspect ratios. And I don't think you realize that the huge real-world spool advantages we're talking about aren't going to show up when comparing dyno plots that start at 2K. Transient response is key here, and we have no shortage of real-world experience, race teams, and so forth to emphasize why twin scroll is advantageous in some scenarios, despite the added backpressure up top for this turbo.



If you really believe that the twin scroll EFRs and the lack of small aspect ratio open scroll housings (which, like I said can't be compared directly to twin scroll aspect ratios) is some sort of Borg Warner conspiracy, then this debate is completely hopeless.

altrix99

Didnt know this was an argument.... I thought this was a technical discussion on a technical forum...

I'm just talking about the 7163 twin scroll vs the 7163 open scroll. I'm not making blanket statements about other turbos and housings...

I understand that most of your racing is done in two gears which makes mountains out of mole hills but in all fairness, this guy was actually competing with a 550hp turbo with a .85ar open scroll housing that actually worked to a degree...

URQaudiguy

Again, you are using the VTV technology as a way to cheat physics. Delete QSV from your vocabulary, as it is really a misleading term that sells the technology short. It tells half the story best case. If a turbo is surging on a rediculously small A/R, then no, you can not VTV it to get even more spool. The beauty of the VTV technology is they will be able to make large t4 hotsides that pick up 10-15% more power on any given setup while still retaining the ability to get the A/R down to the surge line. What this means in real life is redonkulous powerbands that extend 4000 rpm or better instead of they typical 3500 most turbos operate at being pushed. You can use the flap position just as you can use a wastegate to vary shaft speed. In other words, you can ride the surge line all the way up, and still have the cake up top with the big A/R. Like I mentioned previously, it would be insane if BW would put out a 50:50 T/S housing like a 1.30 A/R 7163 housing. Then you could sit pretty at .65A/R coming up on boost(which doesn't surge on anything I have tried it on) then swap over to an insane 1.30 A/R which would likely put the 7163 into the 600whp range on a dynojet. The 9180 and 8374 also are out of surge on the 2.2L mule I have with the .92A/R at 65%(.59A/R). IT would be wicked to have a 9180 50/50 housing with a 1.45A/R as that would be .72A/R on spool up. It would spool around 4500 on a 2.2L and have legs to rev to 9000 for a 4500 rpm powerband.

If you know what you are doing and understand internal combustion engine, it is not difficult to tune a valve. Ultimately you are not controlling MAP, you are trying to control EMAP. Once you grasp that concept, it is easy to PID control the valve and get seamless control of the valve, regardless of altitude, temperature, etc.

On most engines, once EMAP:MAP ratios exceed 1:1, they stop making power on pump gas, and get into knock. E85 or octane can sort of cheat above that ratio, but it is with diminishing returns. If you are not monitoring EMAP on the dyno or in car( assume you aren't if you are playing with a .64 6758), I'd recommend it. It will tell the complete story and make you wish for a way to get more A/R once up on boost and extend the powerband further with more timing. Aka more power.

URQaudiguy

ALso, going down in A/R on the 7163 would be a mega fail. I like the 7163 a lot on e85 or race, but it does not make significant power on the 6758 with identical housings. Most of that is because the 63 MFT is the largest turbine that could fit in the b1 housings. I would love to see the 7163 on a 64mm 7064 turbine with a .92 or 1.05 T4 housing on it. On high VE motors where it could keep under the shallow map in lower PR, it would probably be loads of fun and push the 7163's 60lb/min further than it has done now in a .85 or .80 respectively.

altrix99

Using a larger housing with the valve would make a whole lot of sense in this case. I do get the tech but fuzzy on the components that are being worked with. I used the TDI example because its the closest thing to what you are doing but its inherently very different because of the kind of combustion pressures and load that it produces in a very narrow power band compared to a gasoline motor. Also, you cannot tune for boost and vac per sey as everything that requires vac in a diesel is provided by a pump and it doesnt go into positive pressure so the reference signals are a bit weird...

Anyhow, it would be interesting to see how this tech all shakes out in the end..

nemsin

iTrader: (19)

Here is the BW patent for the VTV housing for those with the technical acumen to make sense of it. http://www.google.com/patents/WO2014099329A1?cl=en

URQaudiguy

It is also significant to add that we have tested the valves on Garrett and Precision turbos as well. It still works on those turbines, but they do not see nearly the deltas that the EFR turbos do. I think most of this is that the EFR turbine was designed to be a twin scroll first, and a mono scroll as an after thought. The Garrett turbine was designed as a monoscroll and most twin scroll housings are repurposed diesel applications.

Typical deltas on spool achievable on b1 series with the QSV device is around 600rpm and about 500 for the MFT 63mm(not surprising, as its efficiency is not shining on low rpm). On larger b2 series stuff, most of them see 800-1000 rpm gains in spool. A HTA3582r on a valve with a 1.06 housing is about 400 rpm gain for reference. The b2 stuff with a functional valve is insane. We can outspool a non valved 8374 on a .92 housing with 9180 .92 housing with a valve pretty easily. Cake and eating right there.

altrix99

I disagree. You say that the .80ar is a TRUE .80ar but it doesnt seem to flow like one to me. I, not so secretly, am in the camp that it is choking out the 63 turbine. I think the .72ar is actually a bit larger in volume when produced in the same frame. It def is a step down from the .85ar. I have no reservations about using the twin scroll housing but bolts/studs and gaskets for the long haul on an alloy housing can be problematic...

URQaudiguy

A/R is A/R. It is just a ratio of area. BWTS engineers didn't look at the divider on the focal and say "lets just include that in the ratio". No, they took it out and ended up with .05 less area in respect to ratio.

What you are experiencing is "wetting" losses, the frictional losses in energy associated with putting 2L worth of thermal and pressurized energy into a small area where wetting losses would be significant. A TS housing has literally twice the wall area for gas to get slowed on, and lose efficiency. If you aren't T/S or aren't using a valve, it is dumb to use a T/S housing unless you absolutely need the A/R and a mono scroll isn't available.

So yes, it is correct to say a mono scroll .80A/R makes more power than a twin sroll .80 with the same turbo is accurate, but the A/R is not different. That's like calling a slow horse a cow because it runs slower than the rest of the horses. It is still a horse.

If you were to monitor back pressure, you would see nearly identical EMAP with both a .85 and a .80, but the thermal energy would be wasted in heating up a turbine housing, slowing down velocity and ultimately not driving a turbine.

altrix99

Yes, in effect, we must account for wetting losses when designing anything with boundaries/walls. If you have twice the areas where flow is compromised then you're effectively decreasing flow area exponentially. So, theoretically, it further supports the idea that a middle of the road open scroll would be advantageous in this particular application. Back in the day, twin scroll housings were measured and produced in specific a/r's that included the wall.

nemsin

iTrader: (19)

I foresee a VTV 8374 being the go to evo turbo. Hopefully, BW releases these soon.