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Old 02-17-2010, 08:20 PM   #21
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Quote:
Originally Posted by Sparetire View Post
This. Often you will see a 250 degree diff in pre and post turbine temp with a restrictive housing, sometimes even more. If you have 1600 post-turbine, then I gurantee you that you are in heat-death land by quite a bit.
Without a doubt. I've been trying to find do not exceed TIT specs for auto turbos; so far all I've come across is one Suby WRX DNE of 1,625 TIT. I can't fathom why anyone would waste the time and effort to install an EGT probe in the TOT position, even on a diesel.
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Old 02-17-2010, 08:48 PM   #22
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Rob, let me preface this by admitting I have no clue about this issue. That said; I've told you before that I have my EGT sensor about 6 inches down on the downpipe. I see average temps of 1250 in my gauge and these drop to around 1100 to 1150 when I use the WI. I've tried it both squirting and without back to back and those are the results I always get.

It seems to me you're on the right track about your IWG. FWIW, I have an external one dumping back to the exhaust further down stream.
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Old 02-17-2010, 08:50 PM   #23
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If you guys are directed at me- my probe is about an inch from my turbine inlet and that's a long ways away from the cylinder head thanks to the long tube header. My original point was to gain some insight on whether or not my internal wastegate might be contributing to the temps. I know the smaller turbine AR doesn't help with the large compressor.
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Old 02-17-2010, 10:16 PM   #24
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Quote:
Originally Posted by m2cupcar View Post
If you guys are directed at me- my probe is about an inch from my turbine inlet and that's a long ways away from the cylinder head thanks to the long tube header. My original point was to gain some insight on whether or not my internal wastegate might be contributing to the temps. I know the smaller turbine AR doesn't help with the large compressor.
Whoops, threads tend to get hijacked quickly around here. As I noted above, I think your probe is properly positioned to measure TIT, but you probably need to do some testing to see if your high **** are IWG induced:

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Originally Posted by sn95 View Post
I'm suggesting a safe approach to validate your EGT gauage is working properly. By starting at a lower power setting w/the wastegate completely shut you can safely globally add/subtract fuel (while at constant load) to determine Peak EGT (and corresponding AFR) and then add fuel from there. Your EGT/TIT gauge should show peak and rich of peak values by doing this. You then have the option of upping boost until the wastegate opens and seeing if you get the same results. If you test methodically like this, you have a better chance of determining if your IG is causing elevated TIT temps or if you simply have a malfunctioning EGT probe/gauge.
As you already know, retarding timing also raises TIT so there is somewhat of balancing act when tuning a pump gas, turbocharged car at high boost levels; too much boost raises the knock level and retarding timing to stave off knock raises EGT/TIT. Sustained **** in the 1,600+ F are going to fry most turbos, so you probably want to keep TIT below that figure.
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Old 02-18-2010, 05:12 PM   #25
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m2cupcar, do you have pics of the carnage?

BTW an EGT probe in the collector is the right approach, since the bulk temperature is higher there than at one of the exhaust ports.

Side note: acceptable turbine inlet temps vary. It depends on the turbo. Virtually any OEM gasoline turbo car made in the past ~ 8 years or so will support 950 C, with some that do 1050 C. 1050 C is becoming the norm.

950 C = 1742 F
1050 C = 1922 F

However, a diesel turbine housing like the one you're running was not intended to live at the (higher) EGTs of a gasoline engine. It will creep and distort, oxidize, crack and generally turn grumpy. But I'm curious about what your wheel looks like.
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Old 02-18-2010, 07:29 PM   #26
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i have run maybe 30 trackday events since i purchsed my turbo na from my buddy. many of them were high-speed tracks with alot of wot time. all the while my egt's were 1550-1600deg.f

while i don't doubt your turbo could have been damaged by those egt's. i do think there's other possible causes. sounds like you had a mix of parts and work done to that turbo. i've seen turbos come apart from not being balanced, or small turbine/big compressor puts alot of stress on the shaft and wheels. one thing i do know, punching it on the street, even consecutively, is nothing like 20mins. on a road course. basically it shouldn't have happened unless your turbo was already sick.
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Old 02-18-2010, 08:15 PM   #27
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Pic of wheel below. When I first saw it I was sure something went through it - blades looked bent at the tears. But then I found some pics recently that had similar damage claiming to be from extreme EGTs.

I used this turbo in my original "Mercedes" turbine housing for simplicity since the downpipe was built around it. What I didn't do was measure the turbine wheel - which was a stage2. My turbine housing was a stage3 - well almost. As near as I can tell the housing was overbored to fit a turbine wheel that had some wear on the blades. I figured this all out when I got the new Garrett only to find that the stage3 turbine wheel wouldn't quite fit into the housing. So I was running a stage2 turbine wheel in an almost stage3 turbine housing (bore) when it failed. That's about the entire history of that turbo.

Never saw over 1600f. I can't verify the exact origins of the turbine housing. I thought I had the typical ford 5 bolt until I bought a ford flange and it didn't fit. I asked around and somebody said they had the exact same housing and it was an OE Garrett housing from a diesel Mercedes. It hasn't shown any signs of failing. There were no obvious signs that it interfered with the wheel (understandable given the smaller wheel in the larger bore). I couldn't find anything in the exhaust (from the cat to the head) that looked like it went through/by/into the wheel. At that point the cause was left unanswered. I got a new Garrett t3/t4 (using the same turbine housing) and have put as many hours on this one without issue.



Here's shot showing the extra tolerance of the stage2 wheel in the larger bore:

Last edited by m2cupcar; 02-18-2010 at 08:32 PM.
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Old 02-18-2010, 11:53 PM   #28
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That's foreign object damage.

An over-temped wheel looks like the blade tips were pulled and stretched like taffy, and little bits of the wheel turn molten and fly off radially. The bent-backward blade tips indicate ingestion of something heavier and slower than the blade tips.
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Old 02-19-2010, 09:46 AM   #29
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That's good to know... I think. Though I gotta say that it's bizarre I never found what it was. I took the entire exhaust apart and never found anything but the little shards of blade... they all collected in the entry of the cat.

Those EGTs you listed- are those temps that Garrett regards as "expected"?

Your comment on the diesel EGTs has got me thinking about all the guys using the Holsets on their cars, but I suppose those turbos are so large on the turbine side that the EGTs wouldn't be too high with reasonable tuning.
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Old 02-19-2010, 01:50 PM   #30
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Quote:
Originally Posted by m2cupcar View Post

Those EGTs you listed- are those temps that Garrett regards as "expected"?
Those 1,850-1,922F rated current gen auto turbos may be overkill for your application. The latest OEM turbo motors (GM Ecotech 2.0L, BMW 335i turbo) are designed to run at stoich/peak EGT at light boost (not WOT). They have direct injection into the combustion chamber and combustion chambers that are optimized for this type of operation. You don't have direct injection and can't safely run your motor at stoich/peak EGT with any significant amount of boost. Peak power is always rich/cooler of EGT, so you don't really need the extra temp rating if you have tuned properly. I also suspect that the current generation of budget priced Chinachargers and replacement turbine wheels lack the advanced metallurgy to survive at 1,900F.
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Old 02-19-2010, 02:04 PM   #31
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Originally Posted by m2cupcar View Post
Those EGTs you listed- are those temps that Garrett regards as "expected"?
Yes. Routine, normal, sustained, etc, and will live for ~150k miles like this. But again those values are for modern gasoline turbos that are on cars that attempt to eke out fuel economy by running as lean as possible.

Quote:
Your comment on the diesel EGTs has got me thinking about all the guys using the Holsets on their cars, but I suppose those turbos are so large on the turbine side that the EGTs wouldn't be too high with reasonable tuning.
That and a squirt here and there isn't enough to really saturate things to where the housing feels the pinch. The truth is that most guys drive like candy asses and never expose the turbine to elevated temps for prolonged periods.
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Old 02-19-2010, 09:39 PM   #32
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A diesel engine may have to run at 1200-1300 degrees for minutes or hours.....

What I always found interesting was that Cummins rated thier EGT's post turbo. I guess since they knew what the entire setup was they had the EGT's post turbo. Most big trucks are this way. Most are rated in the 800-900 F range.
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