Collecting Data On N54 Twin Turbo Mileage and Reliability

HanSolo71

New Member
Jun 1, 2017
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I'm seeing lots of anecdotal evidence and vendor arguing online about who has the most reliable upgraded twin turbo setup. I want to try to collect some actual information on reliability by looking at manufactures and how many miles people have put on each companies turbos.

Please let me know if I missed a manufacture who you have had a good experience with and I will try to add them.


Here is the Google Form I'm collecting the data with.
 

SlowE93

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Jul 2, 2017
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I dont believe mileage is a good way to determine longevity of the twins. I think its more the way the car is driven as well as psi being pushed. You could have 20k miles going WOT and target boost of 10 psi and im sure MOST twins would be fine. Now 1k miles and pushing 28 psi and WOT pulls daily would be another story.
 

fmorelli

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I'm curious how you figure this data collection will help you?

Many of these vendors have a variety of models and versions over the years. They've also evolved everything from suppliers to assembly. Unless you are buying old turbos, you are likely buying their current version. Those that have versions, almost universally have made improvements that are fed in part by reliability observations from larger field use.

Another factor to consider - mileage is a universal number, but just because it is easy to measure doesn't mean that it is an effective measure (to @SlowE93 's comment). This is the folly of metrics: what I can measure tells me what I need to know. Installation, use, tuning, and state of the car's engine components all factor into longevity.

The small sample size you will collect will not factor out the above statement across vendors.

Filippo
 
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Torgus

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Neat idea, I don't think the questions etc. are going to help at all. Like from your charts you can't see when they failed and by what vendor as far as I can see. Also, anyone could falsify the results.

I agree mileage is not everything. There are many variables that makes this hard.

Just go with whatever vendor you trust for twin upgrades, or get a single.
 

HanSolo71

New Member
Jun 1, 2017
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I'm looking for trends through numbers. And on the backend it makes a spreadsheet I can sort and in a few weeks once I stop getting answers I'll make some charts that make more sense. I'm hoping by having lots of answers outliers can be found and removed and we can get a good idea of various vendors reliability. Further research can be done if we find something of interest for example to see if a vendor with a high failure rate may have corrected the issues by looking at purchase times.

As for vendors, because I don't want to collect emails for privacy reasons I can only force login so each vote requires a real Google Account. I can't make sure people can't cheat it but I want to value peoples privacy. Information is still information though and I'm just trying to help the community have a better decision making process than "Who you trust".

What does it hurt to try to gather more information unless people have something to hide.

Also helping people who value reliability over pure power decide if upgraded turbo kits are for them. OEM may be worth it if reliability is your number one concern I want to help those people have some numbers to work with.
 
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SlowE93

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I'm looking for trends through numbers. And on the backend it makes a spreadsheet I can sort and in a few weeks once I stop getting answers I'll make some charts that make more sense. I'm hoping by having lots of answers outliers can be found and removed and we can get a good idea of various vendors reliability. Further research can be done if we find something of interest for example to see if a vendor with a high failure rate may have corrected the issues by looking at purchase times.

As for vendors, because I don't want to collect emails for privacy reasons I can only force login so each vote requires a real Google Account. I can't make sure people can't cheat it but I want to value peoples privacy. Information is still information though and I'm just trying to help the community have a better decision making process than "Who you trust".

What does it hurt to try to gather more information unless people have something to hide.

Also helping people who value reliability over pure power decide if upgraded turbo kits are for them. OEM may be worth it if reliability is your number one concern I want to help those people have some numbers to work with.
OEM is far from reliable. Stock boost levels and BMW was still replacing units. Now asking for input in your post, OEM should not even be an option for higher boost levels.
 

iminhell1

Sergeant
Jun 17, 2018
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OEM is far from reliable. Stock boost levels and BMW was still replacing units. Now asking for input in your post, OEM should not even be an option for higher boost levels.



Well I'm at 133,000 on factory stock twins.
Summer tune is around 24psi, E50.
Winter is only 13psi, E50.
Made 130 drag passes last year (2018)
Made 160 drag passes (2017)
Made 80 drag passes (2016)

Bought car (stock) with 46,000.

And I don't have a racing off season. I try to race year round, currently ice racing weather.
 

SlowE93

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Jul 2, 2017
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Well I'm at 133,000 on factory stock twins.
Summer tune is around 24psi, E50.
Winter is only 13psi, E50.
Made 130 drag passes last year (2018)
Made 160 drag passes (2017)
Made 80 drag passes (2016)

Bought car (stock) with 46,000.

And I don't have a racing off season. I try to race year round, currently ice racing weather.
Thats great. But why did BMW extend the period to replace stock turbos ????? Just like they did for hpfp and other parts. Cool it worked out for you.
 

Asbjorn

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Mar 10, 2018
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Z4 N54 DCT
I'm seeing lots of anecdotal evidence and vendor arguing online about who has the most reliable upgraded twin turbo setup. I want to try to collect some actual information on reliability by looking at manufactures and how many miles people have put on each companies turbos.

Please let me know if I missed a manufacture who you have had a good experience with and I will try to add them.


Here is the Google Form I'm collecting the data with.

Please understand that you are not buying from manufacturers as such, but engineering and sourcing companies. These vendors may switch between part manufacturers as they feel necessary. You need to judge a vendor based on their ability to do engineering, sourcing and quality control. As an example, they should be able to explain why they have chosen a given wheel material over the other, as this is a known quality concern with upgraded twins. Then the next question could be how they know they got the quality they selected and so on.

Now as a vendor, you can try to push the boundaries, or stick with what works. If all you sell is OEM twins with upgraded waste gates, then I am sure you will quickly become the most reliable brand out there. On the other hand, sometimes you need to make mistakes to learn from them. A vendor that has made more mistakes earlier, may actually become the best one later.
 
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PaulKendall

Specialist
Nov 12, 2016
63
16
0
Omaha NE
I think this is an awesome way to allow people to see an average length of life time/ mileage different companies customers are getting from the turbo offerings. It could also be a useful tool to see repeat customers.
 

Torgus

Major
Nov 6, 2016
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Please understand that you are not buying from manufacturers as such, but engineering and sourcing companies. These vendors may switch between part manufacturers as they feel necessary. You need to judge a vendor based on their ability to do engineering, sourcing and quality control. As an example, they should be able to explain why they have chosen a given wheel material over the other, as this is a known quality concern with upgraded twins. Then the next question could be how they know they got the quality they selected and so on.

Now as a vendor, you can try to push the boundaries, or stick with what works. If all you sell is OEM twins with upgraded waste gates, then I am sure you will quickly become the most reliable brand out there. On the other hand, sometimes you need to make mistakes to learn from them. A vendor that has made more mistakes earlier, may actually become the best one later.

Or you know do some actual R&D, reliability testing, and beta testing etc. before selling turbos with wheels that disintegrate etc.

Using your argument that it is good to make mistakes is only party true. It's good if you make mistakes, learn from them, and then release a product that works well incorporating what you have learned, that is part of bringing a product to the market. It is significantly worse to make mistakes publicly aka using your customers as guinea pigs. If making mistakes made vendors better Frankenturbo must be the most reliable twins on the planet ;)
 

MoreBoost

Sergeant
Jul 27, 2017
334
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335i
I dont believe mileage is a good way to determine longevity of the twins. I think its more the way the car is driven as well as psi being pushed. You could have 20k miles going WOT and target boost of 10 psi and im sure MOST twins would be fine. Now 1k miles and pushing 28 psi and WOT pulls daily would be another story.

100% correct.
 

Asbjorn

Lieutenant
Mar 10, 2018
811
552
0
European, based in China
Ride
Z4 N54 DCT
Or you know do some actual R&D, reliability testing, and beta testing etc. before selling turbos with wheels that disintegrate etc.

Using your argument that it is good to make mistakes is only party true. It's good if you make mistakes, learn from them, and then release a product that works well incorporating what you have learned, that is part of bringing a product to the market. It is significantly worse to make mistakes publicly aka using your customers as guinea pigs. If making mistakes made vendors better Frankenturbo must be the most reliable twins on the planet ;)

Right, and even the best R&D, reliability and beta testing won't help if a sub-supplier suddenly decides to cheapen out on production quality after the first batch has been approved. This is where you need great quality control instead, and that has very little to do with otherwise being a good turbo designer.

This is why we need to judge twin turbo vendors as engineering and sourcing houses, not as manufacturers.
 

Xm-n54

Private
May 8, 2017
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2008 BMW 335xi
I think this certainly can help. Mileage would be a very good way to measure how reliable turbos are, granted there are a ton of different variables. However, anyone purchasing turbos besides OE can certainly say they will be pushing higher boost levels. This can expose some data that can be helpful. But just like mentioned up above, it wont be any good unless you get a very large sample size.
 

fmorelli

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I think this certainly can help. Mileage would be a very good way to measure how reliable turbos are, granted there are a ton of different variables.
I'm not sure how to parse this sentence. How is measuring one metric "very good" in the face of "a ton of different variables"? Dependent variables? Correlation vs causation?

Filippo
 
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Xm-n54

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May 8, 2017
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I'm not sure how to parse this sentence. How is measuring one metric "very good" in the face of a "ton of different variables"? Dependent variables? Correlation vs causation?

Filippo
Because all turbo manufacturers will have these different variables present. It puts them on the same playing field. As I said further down, almost all aftermarket turbo options will be tailored for performance levels. If the sample pool shows that "Vendor X" turbos only lasted roughly 5-10k miles with different different variables, and "Vendor Y" turbos lasted 20-30k miles, with different variables at play, I would then say, Vendor Y has better turbos. Would you say that is fair to say?
 

Seaneezy

Corporal
Mar 12, 2018
130
34
0
Ride
e90 LCI 335i
RB Stage 2 (Early gen super rb stealths), installed @ 40k miles.

Was at a 24 psi tune, lowered it to 21psi for daily driving at 60k miles and they are still running strong. Makes my car sound like a charged cummins. No rattle, had some leaks from my inlets (thanks MMP). No JB4, pretty aggressive driving. @ 91k miles
 

fmorelli

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Would you say that is fair to say?
Scientifically I would say it is highly misleading. Let's ignore the ton of different variables and look for a relationship to mileage because that's easy to measure. Don't mean this in any offensive way. It's pretty basic testing - if there are a ton of variables that go into cause, measuring one variable and coming to conclusions is as good as guessing. Actually guessing may be better. Correlation - that is, mileage to a turbo's inherent longevity, is not causation - that is, that mileage (wear) demonstrated the turbo's longevity. That would be a logical fallacy. I've provided an example below - I know it is tongue and cheek, but it makes the point.

Filippo

niccage.png
 
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