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Here is graph to show .85 6758 Mono Scroll vs a VTV 7163 functioning properly. These were same day tests, same engine, etc. The effective A/R of a VTV J housing would be .52 closed and .80A/R open and variable on the flip over point that happens in a span of about 600rpm or so, typically the 600 rpm between spool deltas.
Be sure to note the boost pressures between the two turbos too, not completely apples to apples if gawking at overall, the 7163 was peaking at about 34psi, the 6758 at 36psi. Both out of their sweet spots. On better VE engines where you can keep the pressure ratios lower, they make loads more power(we make 550whp on the Audi TTRS 2.5TFSI with the same style manifold, dyno, fuel, but can keep it at ~24-25psi)
Look at how the torque and HP ramps on teh 7163 on the onset. It isn't a standard ramp and hold, you can see the A/R being varied and the engine responding accordingly. It does ramp a lot faster with the smaller A/R, aka transient is unreal. Imagine how it feels on the street if you have ever been in a 6758 car I can dig up data showing the 7163 held at .52A/R to redline, but it isn't pretty. If it made 430whp, I'd be surprised. You can kind of guess if you look at the 7163 line as to what the hp and torque would look like if it continued.
Thanks for the data. Looks very interesting. I think you missed my point, although maybe I should just keep making counterpoints so we can shake out as much info out of you as possible...
What you are showing us is a variable housing not a twin scroll. Twin scroll volutes at any given time is pulsed by two cylinders while you are pulsing the entire housing in open and closed form with the entire motor. Boost onset in this case would be vastly different then a twin scroll and using the a/r of one volute pulsed by two cylinders at a time... You cannot present that as its not a direct comparison as its a completely separate technology
Thanks for the data. Looks very interesting. I think you missed my point, although maybe I should just keep making counterpoints so we can shake out as much info out of you as possible...
What you are showing us is a variable housing not a twin scroll. Twin scroll volutes at any given time is pulsed by two cylinders while you are pulsing the entire housing in open and closed form with the entire motor. Boost onset in this case would be vastly different then a twin scroll and using the a/r of one volute pulsed by two cylinders at a time... You cannot present that as its not a direct comparison as its a completely separate technology
It is a variable TS twin scroll, but yes, it is on a odd cylinder engine that does not divide into pulses. So yes, the delta between "open" and "closed" on the valve position may be slightly better with better turbine efficiency on a true divided TS setup.
That said, dumping a collective engine exhaust energy into the leading volute of a TS housing is maximizing turbine torque at low shaft speed. Pulse may be more "efficient" but my hunch is that gross exhaust energy at that focal point is going to destroy a TS divided with the VTV device from BWTS where it acts like a TS once open. At that point, the pulse energy (as discussed in this thread) is a mute point.
The real world MS to TS deltas I have seen in life all point to what we have discussed in the last few pages. A TS housing's wetting losses make them hard to make equivalent power as an identical A/R monoscroll. They do scavenge exhaust energy better due to pulsing and thus spool better, but if they are upsized in A/R to make the same topend power, the better spool gains are lost.
Thus a VTV device that maximizes low rpm torque on the turbine but still has A/R legs will be the cake and feast. I am going to test this concept soon on a divided 4 cylinder setup, but sadly it will be with parts not available to the public. Rest assured though, BWTS's EFR team listens, they are passionate and they want to help. It is one of the reasons the EFR lineup is so fun.
Not exactly ignoring. The clowns over at ATPTURBO and garrett themselves dont tell the public this. I'm glad someone hinted this to me so I've since changed my housing from a 1.x to a .84iirc niresist t3.
Originally Posted by 03whitegsr
Also...there is something people seem to be ignoring. A/R is a ratio. Two housings can have the same A/R but be VERY different on flow area. This was the point of T3 and T4 as originally, the T4 had a bigger "R" then T3 so the same A/R meant it had a bigger area then the T3 housing. This has kind of gone out the window in the last few years though. The new Garrett T3 TS housings for example use a larger "R" then the "International T3" divided housings used in the past. It appears Garrett basically stuffed the biggest flow area possible that matched up to the T3 divided inlet size. As such, despite having the T3 name, they flow considerably better than older T3 divided housings. Not quiet T4 size...but definitely bigger.
Absolutely there is additional boundary wall effects. That's largely why the recommendation in the SAE papers is 60% and not 50% for spool and 90% not 100% for power. That is the empirical data results shown in a real world testing. That is the impact of the divider.
As for the chart, I can't comment as I have no idea what either of you have and different cars/motors/setups/tunes will behave very differently.
Yes, I have tested this several times. Large turbos, small turbos, manuals and autos.
I think Garrett was on point in that paper. Now if they would only get their turbine wheels sized right to the compressor wheel
out of curiosity (and so i can learn), why do you want a bigger a/r?
The a/r that's available now for the TS 7163 is choking the turbo at high flow. Most of the recent posts are discussing the pros and cons of a/r size for TS. I still favor a TS with a larger a/r than I do a single scroll. I don't think all the advantage of transient response for TS is lost by upsizing the a/r.
As URQaudiguy said, the ultimate win-win is a TS with large a/r and the quick-spool valve (if it can be made to work seamlessly and reliably).
Since BW is integrating the QSV why hasn't there been any aftermarket testing for people with older TS manifolds/turbines but with an intermediate flapper QSV installed?
Originally Posted by mrfred
The a/r that's available now for the TS 7163 is choking the turbo at high flow. Most of the recent posts are discussing the pros and cons of a/r size for TS. I still favor a TS with a larger a/r than I do a single scroll. I don't think all the advantage of transient response for TS is lost by upsizing the a/r.
As URQaudiguy said, the ultimate win-win is a TS with large a/r and the quick-spool valve (if it can be made to work seamlessly and reliably).
Since BW is integrating the QSV why hasn't there been any aftermarket testing for people with older TS manifolds/turbines but with an intermediate flapper QSV installed?
Its not publically available yet. Sounds like only a few shops are getting it to test. And its not necessarily a simple swap. The additional actuator to control the QSV takes up space that may not be available for manifolds that work with the current TS turbos. Another issue is that a controller is needed for the QSV.
The a/r that's available now for the TS 7163 is choking the turbo at high flow. Most of the recent posts are discussing the pros and cons of a/r size for TS. I still favor a TS with a larger a/r than I do a single scroll. I don't think all the advantage of transient response for TS is lost by upsizing the a/r.
As URQaudiguy said, the ultimate win-win is a TS with large a/r and the quick-spool valve (if it can be made to work seamlessly and reliably).
gotcha. was trying to follow everything URQaudiguy is posting, but some of it is over my head. i sort of made the assumption based on dynos of the 7163 i found that the a/r wasnt bad.
Yes, I have tested this several times. Large turbos, small turbos, manuals and autos.
I think Garrett was on point in that paper. Now if they would only get their turbine wheels sized right to the compressor wheel
They have turbos that are well matched for single scroll stuff. Some of the best matched setups aren't very popular though as it's not the biggest compressor option in that family (GT3071R vs GT3076R for example).
I honestly don't think any of GT series turbines under the GT40 were ever intended for twin scroll housings. As such, almost all of them go for maximum flow and a small tip diameter in an effort to improve response while keeping the turbo external footprint as compact as possible. With TS, you can add some mass to the tip of the wheel to pick up efficiency and the TS will make up for the added inertia.
Some clean sheet turbines built around TS housings would be awesome at this point from Garrett.
i think the qsv will be a bit of a challenge to safely implement. the first time it sticks in the quick spool position will probably be doom for the turbo and perhaps the motor unless there is a turbo speed sensor failsafe.
i think the qsv will be a bit of a challenge to safely implement. the first time it sticks in the quick spool position will probably be doom for the turbo and perhaps the motor unless there is a turbo speed sensor failsafe.
I can dig up data showing the 7163 held at .52A/R to redline, but it isn't pretty. If it made 430whp, I'd be surprised. You can kind of guess if you look at the 7163 line as to what the hp and torque would look like if it continued.
