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M2 Technical Topics > N55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > Upgraded Turbo Owners Roll Call

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      10-10-2019, 12:08 AM   #23
SeanWRT
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There're many parts that can fail to high boost. The open deck is not one of them. Instead it's the last thing to worry about with just any platform. N54 is making north of 1000 and the deck is fine. With N55, I'll say (or conclude) that the turbo is by far the weakest point (that can cause a major fail).

N55 has so limited turbo options because of 1) hot half and manifold in one piece design, and 2) a bottom mounted turbo layout.

There is no hybrid turbo that makes power and runs reliably at above 20psi (middle and upper range). Doing so in long term you're pretty much committed to killing your turbine with the ridiculously high exhaust manifold pressure and EGT. And that's even for the best scenario assuming everything else is done right.

As a good example, one of my n55 buddy just broke his turbine, after 35000km (22k miles) on PS2. There was a short length of time years ago he's running 22psi on meth. But most of time, just logging different pump gas maps from 14-18psi. Other times, used a daily commuter.

He's one of luckier ones, because of his rich tuning knowledge of this platform and 'did everything else right'.

Every platform sees its limit one way or another but people believe what they want and push beyond it. In N55's case, especially with the M2, the limitation is just much closer to stock power than many think.

That being said, everyone has different criteria and priorities, in the end, whatever makes the owner happy matters.

I'll participate OP's questionnaire, but have only one thing to say - Seeing 430whp with STG2 hybrid on pump gas, I already think it's too much power for a N55.

Pardon my broken English:
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      10-10-2019, 02:35 AM   #24
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So the issue was that he wasn't running upgraded HPFP?
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      10-10-2019, 04:54 AM   #25
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Good input as always SeanWRT

How far would you push the Dinan turbo before it’s out of its efficiency zone and generating too much heat?

I’ll likely upgrade the HPFP so I can reliably run E30-50, and get a dyno tune to go with it, before upgrading the turbo to something larger than the Dinan.

Although, I’m already generating too much heat on 90F+ track days and have to start driving the car easier after 10 laps to bring oil & coolant temps back down. Would a larger turbo really have much impact in reducing heat in the 18-20psi range?

Thanks!

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      10-10-2019, 05:18 AM   #26
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Sean,
What are we seeing in that photo? Oil blow by on the compressor?
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      10-10-2019, 05:56 AM   #27
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Quote:
Originally Posted by Yellowflash21 View Post
So the issue was that he wasn't running upgraded HPFP?
Irrelevant.

Quote:
Originally Posted by ZM2 View Post
Good input as always SeanWRT

How far would you push the Dinan turbo before it's out of its efficiency zone and generating too much heat?

I'll likely upgrade the HPFP so I can reliably run E30-50, and get a dyno tune to go with it, before upgrading the turbo to something larger than the Dinan.

Although, I'm already generating too much heat on 90F+ track days and have to start driving the car easier after 10 laps to bring oil & coolant temps back down. Would a larger turbo really have much impact in reducing heat in the 18-20psi range?

Thanks!
The heat you're seeing with your car is at the cold end where compressor is working inefficiently hence more heat, reflected by IAT.

The failure I was talking about is from the hot end, where manifold/turbine housing is very restrictive and makes more back pressure and heat than turbine can take.

Larger turbine normally allows for less backpressure. But it's impossible to quantify the reliability (life circle / psi). Even if there was a probe there (in fact there is not), extensive testing is required but no one from aftermarket does that.

I don't know about the reliability at 18~20psi with STG2, but I'm sure you'd be happy with such a setup (E30+HPFP+PS2). However, 18~20psi is a tricky boost level. On one end, pump gas can't keep up. On the other, Ethanol and meth can support more. Very few really stays there, because reliability isn't normally one of the priorities when he/she is already there.

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Originally Posted by Natek View Post
Sean,
What are we seeing in that photo? Oil blow by on the compressor?
What you're seeing is the turbine breaking to stress fatigue. Pressure and Heat combined are what stresses it.
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      10-10-2019, 06:49 AM   #28
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Quote:
Originally Posted by SeanWRT View Post
The heat you're seeing with your car is at the cold end where compressor is working inefficiently hence more heat, reflected by IAT.
Understood. So, does switching to a PS2 reduce heat that much vs Dinan? And, do I not just end up generating as much heat (albeit, with more power), if I up the boost with a PS2?

The other consideration is lag during daily stop & go driving. Thereís only a tiny bit more lag than stock with the Dinan turbo, but Iím guessing itís pretty noticeable with the PS2.
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      10-10-2019, 07:49 AM   #29
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Quote:
Originally Posted by ZM2 View Post
Understood. So, does switching to a PS2 reduce heat that much vs Dinan? And, do I not just end up generating as much heat (albeit, with more power), if I up the boost with a PS2?

The other consideration is lag during daily stop & go driving. Thereís only a tiny bit more lag than stock with the Dinan turbo, but Iím guessing itís pretty noticeable with the PS2.

I never noticed any lag with the Dinan turbo until I went to a larger intercooler. I currently have stock tune and expect lag to be gone once tuned.
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      10-10-2019, 08:01 AM   #30
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Quote:
Originally Posted by cecaa850 View Post
I never noticed any lag with the Dinan turbo until I went to a larger intercooler. I currently have stock tune and expect lag to be gone once tuned.
Let’s just say (for better and worse) I tend to pick up on little things more than most ppl. Coming from NA and supercharged cars, I thought the stock M2 had a ton of lag. Compared to other turbo cars, maybe not.

But there’s a tiny bit more lag vs stock with the Dinan turbo and I’m guessing it’s fairly noticeable with the PS2. Looking for feedback tho.
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      10-10-2019, 08:35 AM   #31
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Quote:
Originally Posted by ZM2 View Post
Understood. So, does switching to a PS2 reduce heat that much vs Dinan? And, do I not just end up generating as much heat (albeit, with more power), if I up the boost with a PS2?

The other consideration is lag during daily stop & go driving. There's only a tiny bit more lag than stock with the Dinan turbo, but I'm guessing it's pretty noticeable with the PS2.
Making same boost especially high boost, PS2 will reduce heat from Dinan on both cold and hot end with less shaft speed and backpressure.

Dinan turbo is virtually no more lag from stock. That I 100% confirm, from road testing, datalog and dyno sheet (see attached 4th gear pull on dyno, same day). That being said, stock turbo is a bit lag in the first place like you said.

PS2 has noticeably more lag everywhere, even on the fly. Also evidenced from log, it shows a 800~1000rpm lag from stock tested on 3rd gear. This is one of those things in life, all about give and take.

At the end of day, what's the point of having a bigger turbo? The lag - you get it on every tap of throttle, the power - how much more of it do you need in return? Once you're clear, you know if it's worth it.

Personally I'd go as far as octane supports (pump gas in my case) and pick the fastest spooling turbo for it.
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      10-10-2019, 11:52 AM   #32
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Thanks SeanWRT

I’d love to add more power for some of my track battles with friends that have 600-700hp on other platforms, but sounds like I’ll just have to rely on the M2’s agility and my driving skills to keep up with them, as I definitely do not want to add lag.

Now the question is simply if upgrading the HPFP and getting an E30-50 dyno tune would be worth it. Sounds like maybe not much more power than BM3 Stg 2 E30 5.8 and more heat if I plan to stick with the Dinan turbo.

Sorry if this thread jacked some, but inevitably these points would come up in discussion.
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