Twin Turbos vs Single Turbos

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Sergeant
Free Vendor
Dec 7, 2016
420
#1
Its at this point when you realize just how thankful you are that you don't have to put all that twin garbage back on.
Obviously many have dumped that "twin garbage" and went the ST route, but what you may not know is that we've ALSO seen those who dump the twin garbage to go ST and then dump the ST to come back to the aforementioned twin garbage! In short there is a demographic who has seen it all but still prefer the twins enough to take the full circle, thus the twins certainly seem to have their place.

Rob
 
Aug 1, 2017
357
#2
Obviously many have dumped that "twin garbage" and went the ST route, but what you may not know is that we've ALSO seen those who dump the twin garbage to go ST and then dump the ST to come back to the aforementioned twin garbage! In short there is a demographic who has seen it all but still prefer the twins enough to take the full circle, thus the twins certainly seem to have their place.

Rob
Rob, have you ever driven a 650whp+ single turbo N54? I'm just curious.

I know your business revolves around upgraded twins, but I've had them both and prefer the ST by far. The lag I was worried about isn't really there. I'm happy with my decision to go single, but can understand there might be people that prefer otherwise. All depends on the goals for the car.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#3
Rob, have you ever driven a 650whp+ single turbo N54? I'm just curious.

I know your business revolves around upgraded twins, but I've had them both and prefer the ST by far. The lag I was worried about isn't really there. I'm happy with my decision to go single, but can understand there might be people that prefer otherwise. All depends on the goals for the car.
Personally have not driven one but I'm sure it would be a blast, I'd not be opposed to it all!

Also obviously I do agree that we are in the twin business, but we also recommend ST's to potential customers daily. It really all depends on their goals, if they say "I want 650+rwhp daily" we say "Buy a ST". This has been our response for many years now, so it is as simple as that. Then they either go buy a competitive vendors twin turbos who promises a higher capability or they simply take our friendly advice and go straight to the ST. With that being understood the last post was not intended to contain any hidden agenda or attempt to knock ST's; but more so shed some light in regard's to the ole "garbage twins" comment.

Keep in mind things like Smokey and Rattly twins, etc; all very common posts. Understandable since they outnumber ST's thousands upon thousands to one in the real world, and yeah sure there have been some growing pains throughout the years customizing them as upgrades as well. However things like smokey ST's, burnt O2's weekly, fried wiring harnesses, melted valve covers, or just annoying drivability (over the longer term to some demographic) not so much discussed; albeit very real nonetheless based on feedback we have received.

Rest assured there are surely pros and cons to everything and/or at other times it could simply be that tastes have changed. As with anything it is going to be different strokes for different folks but over the past 8 years I've personally had countless conversations with countless amounts of N54 enthusiasts and as such comes living through their experiences. And with that what was stated is certainly what we have heard on many occasions. Guys like yourself even, loved their ST at first, but then came back around as THEY (not you per se) began to miss some of the things the twins just did better. It happens.

Rob
 
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doublespaces

Administrator
Oct 18, 2016
6,684
AZ
#4
Obviously many have dumped that "twin garbage" and went the ST route, but what you may not know is that we've ALSO seen those who dump the twin garbage to go ST and then dump the ST to come back to the aforementioned twin garbage! In short there is a demographic who has seen it all but still prefer the twins enough to take the full circle, thus the twins certainly seem to have their place.

Rob
By garbage, I'm mostly referring to people putting the stock components back in.
 

doublespaces

Administrator
Oct 18, 2016
6,684
AZ
#6
The OEM BMW turbos have a higher failure rate than the aftermarket twins?

Filippo
Not so much the contrast from hybrids, but compared to a single turbo you've got wastegate rattle, rear inlet pipe, smoking issues, obnoxiously tight oil drains, higher failure rate than aftermarket singles, collapsing, melting, cut/beatup inlets and of course the opportunity of having to do it all again.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#7
Not so much the contrast from hybrids, but compared to a single turbo you've got wastegate rattle, rear inlet pipe, smoking issues, obnoxiously tight oil drains, higher failure rate than aftermarket singles, collapsing, melting, cut/beatup inlets and of course the opportunity of having to do it all again.
That is the thing there are going to be problems no matter what you do, there is always going to be someone somewhere with something. Best bet is that if you do not want problems, nearly ever, then go pick up a new Camry and then don't touch it. Kidding aside some of this stuff can be eliminated by what products are actually being purchased, for example we never seem to have any reports about ripped up or melted silicone but it seems to be perceived to be the case based on feedback of other products thought to be made similarly. Also consider that FOUR points of the quoted argument above is on point with this example, lol. Anyway surely the time will come, but it has not yet, or possibly no one seems to even care enough to email us about it over literally YEARS (and tons) of shipments.

Regarding the ST problems you just do not read about it online. Perhaps it is because the consumer seems to accept the problems rather than pouring it all over the forums, as it is not as sensational or heard by any household name with a presence. Or it could simply be because there is nothing Precision, Garrett, Borg Warner, or Comp Turbo is going to do for the failures by posting about it online. Or perhaps it is because they have a top mount and are not as worried about the labor, which is a valid argument 100%. Either way so many issues never discussed but it doesn't mean they are not there. But WE hear about it often, even this morning someone had their smokey precision ripped apart sending pics and it is nothing new. As we sell lots of a la carte adapters, such as oil drain fittings and pcv setups; we get a TON of inquiries- and the problems that are thought to be void are actually way more than one would think.

Rob
 
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Sergeant
Free Vendor
Dec 7, 2016
420
#8
The OEM BMW turbos have a higher failure rate than the aftermarket twins?

Filippo
The OEM BMW turbos are pretty solid- you have to keep in mind the scale of usage here as well. Doesn't mean we haven't heard our fair share of war stories, but as stated above "there will always be someone, somewhere, with something". The key to having any of these things last (OEM BMW or Hybrid) is by utilizing the right components and doing a very precise build/balance- and this takes cutting edge equipment that some do not have currently (or didn't always have) and willing to take the time to do it right as well (difficult to find with outsourcing/mass production). Obviously tasteful supporting mods and reasonable usage (not totally abusive) are more factors.

Rob
 
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doublespaces

Administrator
Oct 18, 2016
6,684
AZ
#9
Regarding the ST problems you just do not read about it online. Perhaps it is because the consumer seems to accept the problems rather than pouring it all over the forums, as it is not as sensational or heard by any household name with a presence. Or it could simply be because there is nothing Precision, Garrett, Borg Warner, or Comp Turbo is going to do for the failures by posting about it online. So many issues never discussed but it doesn't mean they are not there. But WE hear about it often, even this morning someone had their smokey precision ripped apart sending pics and it is nothing new. As we sell lots of a la carte adapters, fittings, pcv setups, so we get a TON of inquiries- and the problems that are thought to be void of are actually way more than one would think.

Rob
I don't pretend there aren't failures, but even if all build qualities were equal, the chances of a twin turbo, stock or hybrid being used on the outside edge of the compressor map tends to be greater based on what I've seen. I don't know anyone personally who has had their garret or borgwarner turbos fail on an N54. That doesn't mean much, other than the fact that I don't know many people. I do however know multiple people who have had their hybrids and stock turbos fail. Heck, I think everyone has had stock turbo problems to some degree. I have an 800whp capable turbo and I intend to use it for 600-650whp for my daily usage.

Now, on the part about single turbos having problems, that I can certainly agree with. Particularly top mounts kits and their heat issues. I tried to buy one of those ER CF engine covers the other day, and nope..The thing is melted by the exhaust turbine housing. I've seen AC lines melted, windshield washer necks, etc.

I can also say that a lot of the problems single turbo people encountered over the last several years are simply platform development related. There is also the cost differential that has to be considered. Single cars are usually down for much longer, tuning is more complicated as the boostbox is a newish thing which has gone under several revisions itself. So I hear ya, there are pros and cons. But the chances of me having to take my single turbo out while making 700whp are lower than if I was running the same setup on whatever twin options can do the same. This is certainly just my opinion and am open to debate the topic :)
 
Nov 18, 2017
764
#10
Obviously many have dumped that "twin garbage" and went the ST route, but what you may not know is that we've ALSO seen those who dump the twin garbage to go ST and then dump the ST to come back to the aforementioned twin garbage! In short there is a demographic who has seen it all but still prefer the twins enough to take the full circle, thus the twins certainly seem to have their place.

Rob
Ive not seen one
 

doublespaces

Administrator
Oct 18, 2016
6,684
AZ
#11
They exist, I know of one person in particular, but that was partially due to budgeting but they did not like the delayed power curve. That lacking low end has been partially resolved however.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#12
Seen online? Or online combined with a couple guys you may know with ST's? If so then probably most in those categories haven't "seen one" either. But rest assured if you'd had a business phone number that is open to the entire platform every week for about 8 years straight, you would have "seen quite a few". Some go back to twins, others sell the car and get another one with twins thereafter too; same outcome. As stated above some just begin to hate them for the heat and more-so drivability, while some others absolutely love them. We recommend them to many pending on their power goals but there is nothing that is all around perfect for every enthusiast out there.
 
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Oct 17, 2017
235
#13
Lag on ST is there because some of the guys uses oversized turbo that cant be driven past the surge line until 4-5k rpm. You get the same thing if you shoved two oversized twins.

With a twin scroll manifold, a single turbo lags just as little as a twin setup with the same flow rate.

Oh, does anyone know what's A/R ratio and compressor efficiency on these hybrid stock frames? Oh wait, nvm, because no one knows, including the guys who have been selling them for years.

Anyway, besides budget and emission reasons, there just no good reasons to stay with "twin garbage", especially at the power level people are chasing these days. And get off the forums if you are that easily triggered by people's choice of words.
 

doublespaces

Administrator
Oct 18, 2016
6,684
AZ
#14
Lag on ST is there because some of the guys uses oversized turbo that cant be driven past the surge line until 4-5k rpm. You get the same thing if you shoved two oversized twins.

With a twin scroll manifold, a single turbo lags just as little as a twin setup with the same flow rate.

Oh, does anyone know what's A/R ratio and compressor efficiency on these hybrid stock frames? Oh wait, nvm, because no one knows, including the guys who have been selling them for years.

Anyway, besides budget and emission reasons, there just no good reasons to stay with "twin garbage", especially at the power level people are chasing these days. And get off the forums if you are that easily triggered by people's choice of words.
I don't think he's triggered, just wanted to address some stuff, thats no biggie.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#15
Lag on ST is there because some of the guys uses oversized turbo that cant be driven past the surge line until 4-5k rpm. You get the same thing if you shoved two oversized twins.

With a twin scroll manifold, a single turbo lags just as little as a twin setup with the same flow rate.

Oh, does anyone know what's A/R ratio and compressor efficiency on these hybrid stock frames? Oh wait, nvm, because no one knows, including the guys who have been selling them for years.

Anyway, besides budget and emission reasons, there just no good reasons to stay with "twin garbage", especially at the power level people are chasing these days. And get off the forums if you are that easily triggered by people's choice of words.
Hmmm. All of the N54 twins all have an Area of ~4.9cm while the Radius' of all of them are ~4.5cm. So A/R is about 1.08. The A/R "language" is however relative to frame sizes so it makes it very hard to differentiate when all you know is the final ratio (and not the specific A and R to achieve the ratio). So even though the N54 Twins A/R ratio seems like it should flow a ton the ratio is based on a small frame size so it really doesn't. In conclusion we know the smaller "A/R's" are great for response and poor for bigger power (which many can appreciate); while those with larger "A/R's" are great for bigger power and poor for response (which many can also appreciate). But you knew all of that, of course, which is why you're such a good valuable asset to any forum.

Rob
 
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Oct 17, 2017
235
#16
Hmmm. All of the N54 twins all have an Area of ~4.9cm while the Radius' of all of them are ~4.5cm. So A/R is about 1.08. The A/R is relative to frame sizes so it makes it very hard to differentiate when all you know is the final ratio; and not the specific A and R to achieve the ratio... so even though the N54 A/R ratio seems like it should flow a ton the ratio is based on a small frame size so it really doesn't. But you knew all of that, of course, which is why you're such a good valuable asset to any forum.

Rob
That's stock housing, anyone with a ruler and a grinder can cut it open and measure that.

I am talking about area of the modified turbine housing after all the milling. Why don't you show us a picture?

Hey what about the compressor efficiency? Care to address that?

Anyway... I get it you want to sell your stuff, but arguing with everyone and everywhere about the merits of your twins isn't gonna win you any customer.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#17
That's stock housing, anyone with a ruler and a grinder can cut it open and measure that.

I am talking about area of the modified turbine housing after all the milling. Why don't you show us a picture?
I'd prefer you figure out what you are talking about, try starting here and understanding what A/R is...
https://www.turbobygarrett.com/turbobygarrett/turbine_housing_AR_and_housing_sizing

The dumbed down version for you is that milling the housing is not changing the A/R. It is however changing the turbine wheel bore diameter, contour, and very often the diffuser area (and of course the WHEEL). This of course can increase the flow greatly through the housing but not by means of changing the A/R. As described above for you that is done by changing the housing frame size (Radius) and/or by increasing the housings entry size (Area).

Rob
 
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Oct 17, 2017
235
#18
I'd prefer you figure out what you are talking about, try starting here and understanding what A/R is...
https://www.turbobygarrett.com/turbobygarrett/turbine_housing_AR_and_housing_sizing

The dumbed down version for you is that milling the housing is not changing the A/R. It is however changing the turbine wheel bore diameter, contour, and very often the diffuser area. This of course can increase the flow but not by means of changing the A/R, as described above for you that is done by changing the frame of the housing size and/or by increasing the actual A size of the area.

Rob
So you are saying you don't mill out any inlet area in order to fit a much bigger turbine? Because of you lose tons of area (A part of the A/R ratio FYI) if you do.

I find that hard to believe given how small and tightly fitting the stock housing is. Happy to be proven wrong if you have an actual picture to show.

Still says nothing about the compressor efficiency, which is the biggest concern with any of these modified twin.
 

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Sergeant
Free Vendor
Dec 7, 2016
420
#19
So you are saying you don't mill out any inlet area in order to fit a much bigger turbine? I find that hard to believe given how small and tightly fitting the stock housing is. Happy to be proven wrong if you have an actual picture to show.

Still says nothing about the compressor efficiency, which is the biggest concern with any of these modified twin.
Ok so what I am hearing is that if I put in enough hours with you that someday you may have some clue of what you are talking about, and then can MAYBE actually speak intelligently enough to be a more successful troll? We all know it will never be your intention to be anything greater than that, despite having gone out of my way to give you some insight.:confused:

OP sorry about the thread- it's gotten way out of whack and it was a gem.
 
Oct 17, 2017
235
#20
Ok so what I am hearing is that if I put in enough hours with you that someday you may have some clue of what you are talking about, and then can MAYBE actually speak intelligently enough to be a more successful troll? Ok bud I'll get right on that one...:confused:

OP sorry about the thread- it's gotten way out of whack and it was a gem.
You mill out the turbine housing to fit the bigger turbine blades, correct?

So please explain to me, how can you mill out the turbine housing, without milling into the exhaust channel that directs the exhaust from the manifold onto the turbine blade?

Sure you might not be changing the cross sectional area of the inlet (as it really depends on where you are measuring that), but you are still narrowing down the exhaust channel within the turbine housing if you want to fit a wheel with bigger inducer diameter. And given how much of the turbine housing are being milled out on these high flow hybrids, I just don't see how that isn't a valid concern.

Anyway, I am sure you know exactly what I am talking about. And I am sure you understand the limitations of the reusing these stock housings for high power/high flow application but just don't want to admit them publicly.

So please save the personal attack and smart ass comments for Tony when he gets kicked off bummerboost again. I can assure you will have a lot more fun when dealing with someone of your level again.
 
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