[jturboawd]

Just wanted to share my experience. I daily my car map 7 on e70-e85. I get on her about 1 time a day on average. Car is at 74K miles, 8k into a ps2. last 2k i have been loosing small amounts of coolant to a mysterious unknown place. This started with a cracked expansion tank line, then a cracked tank itself. Prior to tank failure I would run 25psi on a regular basis. after this I turned down the boost to 20. Things where ok for a while, but i would still look coolant. As this increased I went ahead and tested my coolant system. This made the issue worse. Yesterday the car would not start or run right. Pulled my plugs and found #6 dripping wet.

So after much research I purchased a used engine and will be installing a speedtech turbo kit. My PS2 and port injection will be for sale soon. I plan on moving back to meth. I have seen more of the n55 head gasket threads during research. I would not call it common though. I will also be selling my long block. All is good minus head gasket, would be great for a build. I personally think high boost + higher timing + excessive drive pressure may have lead to excessive cylinder pressures. I think using the pump timing map and lower drive pressures will allow more power with the same cylinder pressure and keep the engine less stressed. I know many would argue those points, but this is the route I am taking. Ill provide picks, etc, when time comes.

[Abear]

That sucks to hear man. Seems like its gonna work out for you though, bigger turbo and all, haha.

Why are you gonna go back to meth though? PI will help keep the engine healthier since it distributes the extra fuel more evenly. Although, you could be going with a direct port meth and that would too I suppose. I just hated having to fill my meth tank all the time, plus if you run out unexpectedly you cant go fast .

Good luck with your new build though, and thanks for the heads up on the heads!

[Weehe]

I'm confused on why a bad head gasket means you should replace the whole engine. Isn't the gasket $300, bolts $50 and you can buy the timing tool kit for $300 to DIY.

[JETmn]

Agree, a head gasket isn't that big of a deal. I would just replace that. Please keep us posted on the speedtech results as I am looking at the kit also, but will probably go PS2 since it is my daily.

[Newguy123]

Crappy.... But as others said why swap the motor with another stock used one? How long do you let your car warm up in the morning before romping on it?

[jturboawd]

Was thinking about building it anyways. It's my daily and I did not want to mess around with having to do things more than one time. If I stay with the platform then I'll build this block in the mean time.

Car was always taken care of. This stuff just happens sometimes. Wanted to add this to the forums as a data point.

[Pure Turbos]

Michael,

Your car melted a turbine wheel, and now you blew a headgasket. Maybe you had a lean cylinder or lean bank the whole time? Or some other running condition. I would consider some diagnosis before running high boost on your next motor. All 6 cylinders are averaged into 1 AFR value on N55. So it would not be obvious if you had an issue. Maybe have the injectors tested before the next motor. Food for thought.

[jturboawd]

I am not Michael and did not melt a turbine wheel? Car ran like a beast. Logs were solid. Plugs typically read the same across cylinder. I have a theory on bank variation using stock manifold but time will tell.

[jturboawd]

I am on the fence between staying e85 or meth. If I go meth it will be with Steve's new meth port with added nozzle on cp. Alternatively I might stay pi e85 and add some meth.

[Pure Turbos]

Originally Posted by jturboawd

I am not Michael and did not melt a turbine wheel? Car ran like a beast. Logs were solid. Plugs typically read the same across cylinder. I have a theory on bank variation using stock manifold but time will tell.

Ah ok, sorry. Got you confused with someone else. Good luck.

[houtan]

Sucks. But, Still not following your logic on swapping the motor. Seems replacing the head gasket is much less labor. You may want to build a motor? Great, you have the used one right there ready to tear down. Anyway, good luck.

[jturboawd]

If we are starting to see turbine blades fail I would imagine that has something to do with having a huge Drive pressure ratio

I would not say it's much to do with the drive pressure ratio as to do with having very high drive pressure. Pure puts dual seals on their shafts and I'm sure this helps the reliability with the really high drive pressure.

[jturboawd]

If the gaskets been jetting into the cylinder there is a moderate probability that there's some surface damage to either the head or the block. Since this is my daily driver and 5 600 Wheel Horse is my long-term goal then a new long block ensures these interfaces are in good condition as well as gives me a lower mileage drivetrain. If I get tired of the 7670 that comes with the speedtech kit and I will build the short block and start over.

[Cory S]

Drive pressure ratio?? Terminology check.

[Newguy123]

Originally Posted by jturboawd

If we are starting to see turbine blades fail I would imagine that has something to do with having a huge Drive pressure ratio

I would not say it's much to do with the drive pressure ratio as to do with having very high drive pressure. Pure puts dual seals on their shafts and I'm sure this helps the reliability with the really high drive pressure.

A melted turbine wheel usually is from a restriction in the exhaust that creates excess heat. Like a failed c a t that melts together and creates a ton of extra heat. Bye bye turbo

[jturboawd]

Drive pressure is pre turbine exhaust pressure, more common in diesel speak

[Cory S]

Have you actually pulled the cylinder head yet?

[jturboawd]

Nope, borescope wet plug and steam cleaned cylinder. I'll pull head later or sell as is.

[Stoolz]

So the back pressure on the tank and tank line caused them to crack? Damn bud that sux. I have the same car and run the same boost. Pi going on today, might have to rethink my 30psi goals.

[NorCalN55]

Originally Posted by Newguy123

A melted turbine wheel usually is from a restriction in the exhaust that creates excess heat. Like a failed c a t that melts together and creates a ton of extra heat. Bye bye turbo

That was my car and happened 2 years ago. I pulled the hi flo c a t and it was fine. Perhaps a combination of the c a t and my secondary c a t as I am xi. I still have my head gasket though

[HydroStream6]

Has anyone taken pre-turbo pressure measurements with the PS2 at this level? I'd be interested to see backpressure vs boost pressure. We know the N55 turbofold is restrictive but the PS2 turbine is much larger than stock. Is any machine work done to the turbofold other than boring for turbine fitment?

[jturboawd]

Turbofold is untouched, just larger turbine prep machining in cast section. Min restriction is rear bank, I think to spool based on bmws pulse design. Typically on a twin scroll bmw would split the runners based on pulse timing, since this is a inline 6 using a split clam turbofold they stayed with a front and back bank. To get better spool and turbo efficency the volutes from the front and bank banks are different. The rear is more restrictive, but overall I feel the n55 is much more restrictive then the n54 set up. Everyone talks about why the n55 is weaker, but nobody has considered loss of 've due to this.

[houtan]

Originally Posted by HydroStream6

Has anyone taken pre-turbo pressure measurements with the PS2 at this level? I'd be interested to see backpressure vs boost pressure. We know the N55 turbofold is restrictive but the PS2 turbine is much larger than stock. Is any machine work done to the turbofold other than boring for turbine fitment?

Please share your data indicating the turbofold is a restriction.

[jturboawd]

It's all posted on the speedtech thread

[Peter @ Pure]

I think long time ago Rob (RB) posted pictures of a cut-up N55 stock PWG manifold.
It shows the 2 runners from the manifold to the turbo.