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Old 03-28-2011, 12:34 AM   #851
seanathanq83
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thats awsome, so faster spool, that would be nice, kinda thought it would make more power because of the less restrictive turbine but i guess not, either way if in reality it was only 7% and only gaines 150rpms spool i think it would be great, but with all this, really makes it look like even with the larger exhaust wheel the 8374 would be a much better fit on these 2.5 since you just run so far off the chart, or maybe if someone comes out with a few mm bigger compressor wheel to keep the efficiency up more in the higher rpms, this turbo would really not do good if you were taking it to 8000-8500
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Old 03-28-2011, 01:32 PM   #852
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Quote:
Originally Posted by LittleBlueGT View Post
So I did some more MB work. I played with EGT (pre-turbo, not post head) and turbine efficiency to get it to match the graphs that Jeff showed us...




As you can see, if it did affect turbine efficiency by 15% in the spool-up area, it would make a pretty big difference in boost threshold, like 500+ rpm. It will be interesting when we actually see one installed and working.
well done!!!
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Old 03-28-2011, 01:50 PM   #853
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We will see how a twinscroll 1.06 7570 journal bearing Borg does in the next month or so. It may not be an efr, but it will be curious to see how it does against its single scroll successor.
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Old 03-28-2011, 02:17 PM   #854
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Originally Posted by Full-Race Geoff View Post
well done!!!
Geoff, if your kit does this at the 15% level I'm sold...
if it performs at the 10% level, I'm probably sold too...lol.

then I'll have to convince the wife...lol

-Russ
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Old 03-28-2011, 02:21 PM   #855
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Originally Posted by LittleBlueGT View Post
As you can see, if it did affect turbine efficiency by 15% in the spool-up area, it would make a pretty big difference in boost threshold, like 500+ rpm.

It will be interesting when we actually see one installed and working.
I'm hoping that you were fishing for a response on that one.

I don't work for a turbo company but I've been studying every research and scientific paper I can find about twinscroll since I heard about these turbos in Fall '10. Based on everything I've read, I believe that the "spool-up area" affected by TS (and not open turbine housings) is primarily at pressure ratios less than 1.8 and shaft speeds less than 100,000 rpm. Basically the 10-15% gains are in the 5-10psi spool-up range and not at 15psi, 25psi, or 35psi. Otherwise, as you've correctly noted with your graph, people would have very large EFR turbos spooling off idle.

To sit back and take a reality check, if we think about my idea that the primary gain of TS is sub-1.8PR and sub-100K shaft speed - doesn't that agree with the feeling of livelier street boost and smoother more linear boost ramp as compared to same sized open T3?

Matt
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Old 03-28-2011, 02:49 PM   #856
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Quote:
Originally Posted by crashtke
We will see how a twinscroll 1.06 7570 journal bearing Borg does in the next month or so. It may not be an efr, but it will be curious to see how it does against its single scroll successor.
I will have my 7670 1.0ar on in about two weeks hopefully, just got word the kit will be done by monday
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Old 03-28-2011, 04:15 PM   #857
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Quote:
Originally Posted by nucci View Post
I'm hoping that you were fishing for a response on that one.

I don't work for a turbo company but I've been studying every research and scientific paper I can find about twinscroll since I heard about these turbos in Fall '10. Based on everything I've read, I believe that the "spool-up area" affected by TS (and not open turbine housings) is primarily at pressure ratios less than 1.8 and shaft speeds less than 100,000 rpm. Basically the 10-15% gains are in the 5-10psi spool-up range and not at 15psi, 25psi, or 35psi. Otherwise, as you've correctly noted with your graph, people would have very large EFR turbos spooling off idle.

To sit back and take a reality check, if we think about my idea that the primary gain of TS is sub-1.8PR and sub-100K shaft speed - doesn't that agree with the feeling of livelier street boost and smoother more linear boost ramp as compared to same sized open T3?

Matt
I am always fishing, something I catch something good.

What you say sounds realistic, and if that is the case, I would guess we could see something like this:



Which would still be pretty good IMO, as this is a bigger a/r housing, so should allow for more top-end. If there was an .83 TS housing the boost threshold gains would be even more.
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Old 03-28-2011, 10:11 PM   #858
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^^^ It all depends how the A/R is measured. You said the 0.92 A/R Twinscroll housing is larger and should be less restrictive. I have my doubts on that unless the A/R is measured properly taking into account the divider wall inside the turbine housing. I think the 1.05 A/R Twinscroll housing would probably allow for the same topend flow as the 0.83 A/R Singlescroll but testing will confirm it

Anyways thumbs up for your efforts to get a more realistic image of possible spool of the TS turbos on the Subaru. I definitely hope it works out as well as it shows on the graphs!

Cheers,

Jasper Kopinga
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Old 03-28-2011, 10:25 PM   #859
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BTW. Regarding the comment about efficiency. This may be a bit controversial but has anybody ever thought of putting a restrictor on the intake of the compressor housing to boost the P/R of the turbo at THE SAME manifold pressure to get into a higher efficiency island as well as even more flow capability in some cases??

To me it seems the EFRs are kick arse at high P/R which is normally not possible but when making a restrictor you can boost P/R for a given manifold pressure. Ofcourse you do not want it to become too restrictive to limit horsepower and to be honest the best way would be to have ANOTHER fully mappable DBW throttle body on the compressor housing intake Eh, hang on...... Turbo F1 cars had that....and for a reason You can keep the turbo in it's sweet spot.

Cheers,

Jasper.
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Old 03-28-2011, 11:08 PM   #860
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Keep in mind that output heat is a function of PR * efficiency. So if PR goes up, efficiency would have to increase by at least as much as the PR increase, just to keep output temperatures constant. If the PR increases more than the efficiency does, output temperature will increase.
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Old 03-29-2011, 06:55 AM   #861
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Quote:
Originally Posted by jkopinga
^^^ It all depends how the A/R is measured. You said the 0.92 A/R Twinscroll housing is larger and should be less restrictive. I have my doubts on that unless the A/R is measured properly taking into account the divider wall inside the turbine housing. I think the 1.05 A/R Twinscroll housing would probably allow for the same topend flow as the 0.83 A/R Singlescroll but testing will confirm it


Cheers,

Jasper Kopinga
CS Racing
Taiwan.
Then there is no point in it being twin scroll. The whole idea is that it maintains the spool of a smaller housing with the flow capacity of a much larger housing.... I don't think bw is as dumb as you think they are. The ts housings are both sized so they should both out spool and gain top end on the single scroll versions of the same turbo.
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Old 03-29-2011, 08:01 AM   #862
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Quote:
Originally Posted by jkopinga View Post
BTW. Regarding the comment about efficiency. This may be a bit controversial but has anybody ever thought of putting a restrictor on the intake of the compressor housing to boost the P/R of the turbo at THE SAME manifold pressure to get into a higher efficiency island as well as even more flow capability in some cases??

To me it seems the EFRs are kick arse at high P/R which is normally not possible but when making a restrictor you can boost P/R for a given manifold pressure. Ofcourse you do not want it to become too restrictive to limit horsepower and to be honest the best way would be to have ANOTHER fully mappable DBW throttle body on the compressor housing intake Eh, hang on...... Turbo F1 cars had that....and for a reason You can keep the turbo in it's sweet spot.

Cheers,

Jasper.
I fail to see the point of artificially increasing the pressure ratio. Adding a restrictor to the inlet is completely counterintuitive to me. Seems to me that you would be simply adding heat and pumping losses for nothing. Standard convention is that you want zero restriction on the inlet.

From my memory, F1 cars did have the throttle before the turbo, but it was the main throttle. I'm sure there were VE gains from having the throttle pre turbo vs post turbo. It wasn't like there was another throttle on the intake manifold.
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Old 03-29-2011, 08:15 AM   #863
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Quote:
Originally Posted by thefoos View Post
I fail to see the point of artificially increasing the pressure ratio. Adding a restrictor to the inlet is completely counterintuitive to me. Seems to me that you would be simply adding heat and pumping losses for nothing. Standard convention is that you want zero restriction on the inlet.

From my memory, F1 cars did have the throttle before the turbo, but it was the main throttle. I'm sure there were VE gains from having the throttle pre turbo vs post turbo. It wasn't like there was another throttle on the intake manifold.
From a quick search it seams the F1 cars had a TB before the turbo to reduce drag on the compressor when off throttle, making for less lag. There were conflicting comments on whether the F1 cars had a single TB before the turbo or 2 TB's, with a secondary before the turbo and a primary after. I suspect the design was different in different years and teams. They also had other differences like no wastegates and primitive blow-off control methods, and they were running higher boosts so without more understanding of the engineering I don't feel like I can say whether a similar setup would help the typical subaru setup. I'm sure there's a bunch more tricks that could be done with the turbo plumbing, but some one needs to show that the solutions are cost effective and easily implementable to be worth it to the general community.
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Old 03-29-2011, 08:56 AM   #864
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didn't they also run a higher boost from the turbo than they fed the engine? IE example boost to 100 psi, go through relatively small intercooler to drop temps, then expand to say 80 psi and have end result of much cooler than ambient air going into engine.
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Old 03-29-2011, 09:11 AM   #865
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Quote:
Originally Posted by nucci View Post
Based on everything I've read, I believe that the "spool-up area" affected by TS (and not open turbine housings) is primarily at pressure ratios less than 1.8 and shaft speeds less than 100,000 rpm. Basically the 10-15% gains are in the 5-10psi spool-up range and not at 15psi, 25psi, or 35psi. Otherwise, as you've correctly noted with your graph, people would have very large EFR turbos spooling off idle.

To sit back and take a reality check, if we think about my idea that the primary gain of TS is sub-1.8PR and sub-100K shaft speed - doesn't that agree with the feeling of livelier street boost and smoother more linear boost ramp as compared to same sized open T3?

Matt
That ^^ does seem to correspond with my own observations from running a DOM3 with small 8cm² housing against the current TS 84-75 with HUGE T4 turbine in comparison. boost threshold (no boost to small positive boost) is still about the same on a small 2,2 ltr, but full boost is still 500 rpm later!

However, because of the less restrictive turbine, it does give more power at the same boost level and can keep high boost all the way to redline, whereas the small turbine'd 30R could not even hold 24 psi to redline.

Personally I am still amazed that such a large turbo (the 84mm wheel is ~ 72 lbs) gives such great drivebility. I hold TS largely responsible for that
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Old 03-29-2011, 09:14 AM   #866
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Quote:
Originally Posted by sumfoo1 View Post
Then there is no point in it being twin scroll. The whole idea is that it maintains the spool of a smaller housing with the flow capacity of a much larger housing.... I don't think bw is as dumb as you think they are. The ts housings are both sized so they should both out spool and gain top end on the single scroll versions of the same turbo.
It's no secret that old school twin-scroll turbine housing are actually smaller in the TS configuration than the single scroll type for the same listed A/R due due the area taken up by the divider wall. The new SS thinwall housing should help minimize that difference though.
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Old 03-29-2011, 10:20 AM   #867
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Originally Posted by jdchmiel View Post
didn't they also run a higher boost from the turbo than they fed the engine? IE example boost to 100 psi, go through relatively small intercooler to drop temps, then expand to say 80 psi and have end result of much cooler than ambient air going into engine.
Those F1 engines did run extremely high PR's. I don't remember any published figures, but increasing PR ultimately is the only way to increase power, assuming all the other VE/rpm tricks have been exhausted. It was on the order of 80-100 psi. Thats the only way to get 1000hp/liter that I know of
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Old 03-29-2011, 11:07 AM   #868
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Old F1 cars ran dual TB's as a way to regulate turbo response and in the roll of a semi-bov. The vacuum formed across the compressor allowed for higher wheelspeed (vacuum equals no molecules to force into and out of the compressor)...however having dealt with this in FSAE, I wonder how their compressor oil seals liked it. We had oil sucking issues with TB -> restrictor -> compressor.

the primary TB's kept throttle response up and the secondary/turbo TB was more of a boost response tool.
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Old 03-29-2011, 11:07 AM   #869
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Old F1 cars ran dual TB's as a way to regulate turbo response and in the roll of a semi-bov. The vacuum formed across the compressor allowed for higher wheelspeed (vacuum equals no molecules to force into and out of the compressor)...however having dealt with this in FSAE, I wonder how their compressor oil seals liked it. We had oil sucking issues with TB -> restrictor -> compressor.

the primary TB's kept throttle response up and the secondary/turbo TB was more of a boost response tool.
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Old 03-29-2011, 04:55 PM   #870
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carbon seals - used when a TB or a carb is in front of the turbo.
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Old 03-29-2011, 07:11 PM   #871
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Originally Posted by ozzimark View Post
Jeff, did you log EGT just before the turbine during the dyno runs? If not, could you do another "cold" and "hot" run where you do? The difference in spool in those two cases is rather large, and it's making me think that the design of the EFR turbine is very sensitive to changes caused by the cooling of the exhaust gas over the very long up-pipe that subarus typically run.
Call me lazy, but the day i put in the sensors (one for gauge and one for ECPro) i didn't want to remove the uppipe so i put them in the header. So i don't have the EGT changes at the inlet of the turbo, but this weekend i will test it with our laser temp gun and see the changes. For sure this effects spool up and on the road i would guess the headers run a little hotter than the dyno. Also on the road they are up to full temp after one run.
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Old 03-29-2011, 08:45 PM   #872
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Lazy!

Just kidding, I really appreciate all the work you've done so far! I think you're onto something with the temps being higher on the road than when doing a dyno run; If true, it would really help explain the difference in feel between the 7670 and the GTX3076R on the street, when the former is "slower" on the dyno.
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Old 03-29-2011, 09:37 PM   #873
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^ yeah i just dont see that.....300 rpm slower on the dyno...yet faster on the street.

if thats true....then my road tunes should take off as people should swear off dynos since there would be no point if dyno pulls dont represent the street in any way.
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Old 03-30-2011, 02:00 AM   #874
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It depends on whether the car is loaded before the dyno run and/or road tune run. Steady state driving will keep the EGTs up, while a dyno run without some time to build EGTs will not build EGTs to the same temp. But 300 RPMS is a stretch
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Old 03-31-2011, 01:47 PM   #875
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it stopped raining there yet? i need some logs!
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