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Came across a small paper on variable volute tongues today while researching about turbine housing designs. Seems good in theory being able to increase the a/r at the tongue section to help reduce emp at high rpm. Not sure how good it performs as it's only changing the a/r at the very end of the volute where the rest of it remains the same. Also thinking it might cause a fair bit of unwanted turbulence introducing all that extra flow back into the start volute. Got me thinking about the terms volute and scroll, are they the same thing? I find some papers refer to it as scroll and others volute.

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SUI GENERIS UTE
GQ Ute 1990 Silvertop
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Discussion Starter #22
Have a look at Blaylock switchblade turbo's same concept with a tail to wrap the wheel. They do work but they can have issues with EMP or flow issues so they usually have to have a larger A/R to compensate or a different turbine wheel to flow a bit more. A twin scroll with a divider flap (Quick Spool) can do a better job in my opinion. More effective A/R change for the volume flowed.

https://switchbladeturbo.com/how-it-works/
 

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Is the last two pics with the black housing still a twin scroll? Couldn't quite see inside clearly enough from the pics, I can see exactly how it works for twin scroll by effectively halving the A/R increasing the velocity and harnessing a stronger concentration of exhaust pulses when operating at lower engine rpm/lower volume but can't see how that works on a single scroll with just having a flap at the throat? Although depending how far in the flap goes in and how much of the scroll it closes off i'm sure it'll still increase the velocity a bit which may have a positive effect but it would still open back up to the original A/R before flowing through the turbine so who knows. I just like the pondering random stuff like this lol.

Thanks, I checked out the switchblade website. Very interesting although they only seem to be doing it on the larger applications with huge turbos for plant and heavy transport. I'm guessing their design is a bit too hard to scale down to fit the smaller passenger vehicle sizes, either that or there just isn't the market as their is better options.
 

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SUI GENERIS UTE
GQ Ute 1990 Silvertop
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Discussion Starter #24
The second set of pic is my test housing and its a .78 a/r twin scroll. Even with .78a/r it still needs a wastegate to control boost on a TD. The blaylock system uses a very larger housing so no wastegate but uses the blade to concentrate velocity onto the blades controlling boost levels. There is electronics to control the switchblade otherwise you get massive surge on deceleration on boost only control. This was a issue in the early days of the product. They do make them for cummins and ford, i believe there is one for a duramax. The toeing community do seem to use them but difficult to get many owner reviews on the product. I can only assume its really a bit difficult to set up for modified engines but seems to work very well on std fuelling. Considering there is a lot of upgraded VNT systems now days for these engines its probably not a lot better in its total performance seen by the customer. I did get them to price a S200SX BW using their housing. It was double the price of the original turbo purchase price at the time. Also they suggested the housing size would be too large for the 4.2 litre not allowing enough blade movement.
 

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Even with .78a/r it still needs a wastegate to control boost on a TD.
This is the one thing that I probably think about most often lately. It just seem silly and inefficient to be wasting all that exhaust gas out the gate, I guess they got the name spot on with "WASTEgate".
 

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SUI GENERIS UTE
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Discussion Starter #26
Yes you are right with effective efficiencies. But we are not using a fixed rpm engine so we need adjust-ability for all rpm conditions and load- fueling. Remembering on our street 4x4 we are rarely getting power up to where the gate is open and bleeding off exhaust gas so most of the time we are using all the energy in the gas possible for a turbo.
 

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Remembering on our street 4x4 we are rarely getting power up to where the gate is open and bleeding off exhaust gas so most of the time we are using all the energy in the gas possible for a turbo.
LOL that hasn't been the case for me lately! I've generally been staying in the 2-4000rpm range as of late since someone decided it would be a good idea to design a product that actually still works in that area and now i'm craving more of this having max power at max rpm idea. I've still got a bit to do in terms of testing a few ideas I have and setup changes but my current thinking is I'd be more than happy to shift peak boost 3-400rpm later to get power even more linear closer to redline. I did an experiment where I ran the gate slightly cracked open which gave me this slower boost rise and I really liked the way the power came on so linear and seem to hold on much closer to redline. I did this test before I had my EMP gauge connected so can't confirm but I have a feeling my high rpm EMP:IMP would have dropped a few points with the feeling I was getting up top with the extra gate travel I was getting. I plan to revisit this test again soon to confirm. I'm not doing this trying to achieve big numbers or anything like that, actual power figures are the least of my concerns. It's just i'm really enjoying the way the linear power delivery drives and it matches my driving style for how I like to drive my car on weekends.
 

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SUI GENERIS UTE
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Discussion Starter #28
Well as you know you didn't like the fast spooling turbo compared to your current version. I can appreciate why. Obviously we can design in that aspect but its not what most people thing they want. I like to rev these types of diesels so its more how i like it because it gives wider effective power rpm range that feels stronger, and it is a faster feeling car.
 

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Just seen these pop up on a facebook page which caught my attention. I didn't realise people were doing split blade 5+5/6+6 turbine wheels. Pretty common to see it on comp wheels now but never seen it on turbines?
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We did machine a turbine wheel like this many years ago, effectively 6+6, great top end, not so good for drive.
 

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Though as much, still an interesting concept though which is why it caught my eye. Interested about the machining side of it, what machine did you use to cut every second blade shorter? Never really thought about how people experiment and get mods done to there turbines before. You hear quite often people saying they clipped there turbine but how are they doing this, at home with a grinder, can local machine shops do this easily or do they get sent away to specific businesses who specialize in this work?
 

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Though as much, still an interesting concept though which is why it caught my eye. Interested about the machining side of it, what machine did you use to cut every second blade shorter? Never really thought about how people experiment and get mods done to there turbines before. You hear quite often people saying they clipped there turbine but how are they doing this, at home with a grinder, can local machine shops do this easily or do they get sent away to specific businesses who specialize in this work?
Oh man, home grown turbo mods 🤕, easy enough to clip but you need specialised gear to re balance, I'm sure you have seen the damage an out of balance comp or turbine wheel can do. And then that re balance has to be done in the correct position or movement during heat expansion can become an issue. Interesting question though look forward to answers.
 

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Machining was pretty agricultural, and getting a perfect balance was impossible, but we got it close enough for testing purposes.
And I have clipped many a turbine with a variety of things and re balanced them when testing, ran many a test turbo that isn't balanced either, most of them done lots of km and possibly hundreds of dyno pulls at speeds up to 180k+ rpm without issue.
Certainly not what I would recommend however.
Totally different thing when you are looking for a change vs looking for it to survive for many many thousand of km.
 

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Saw this video when I googled turbine clipping and couldn't help but think backyard version would be turbine shaft in cordless drill held up to bunnings bench grinder!

clipping.JPG
 

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I have used a tool post grinder like that, get pretty cool sparks off a TiAl turbine wheel too, thought I would be fancy since I had a fancy turbine wheel.
Hmmmm, from memory the TiAl turbine wheel and compressor wheel was some 20-25g lighter than a traditional 713 turbine wheel by itself, the thing had some awesome transient response.
I have a 4" grinder setup that goes in the tool post on the lathe also, I have even just free handed it on the belt sander, free handed it with a flapper disc in the grinder LOL.
 

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SUI GENERIS UTE
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Discussion Starter #36
I have used a tool post grinder like that, get pretty cool sparks off a TiAl turbine wheel too, thought I would be fancy since I had a fancy turbine wheel.
Hmmmm, from memory the TiAl turbine wheel and compressor wheel was some 20-25g lighter than a traditional 713 turbine wheel by itself, the thing had some awesome transient response.
I have a 4" grinder setup that goes in the tool post on the lathe also, I have even just free handed it on the belt sander, free handed it with a flapper disc in the grinder LOL.
Bloody Redneck :):)
 

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Currently reading a study about ways to reduce turbine weight but still maintaining wheel strength helping to reduce centrifugal stresses and inertia.

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Anyone ran or tested having an external gate plumbed off the turbine housing before? Doesn't look great in terms of flow going through scroll into the turbine but honestly have no idea. Started googling it after the thought popped into my head and was surprised to see so many examples of it been done before so I guess it can't be that bad?

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