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08-03-2020, 12:14 AM
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#1
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Name: RacinNdrummin
Title: In-directly Ignored
Status: Not Here
Join Date: Sep 2012
Location: Maple Valley, WA
Member`s Gallery
Posts: 97
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Turbo Wheel speed, Turbo sizing, and piping volume
So the case at hand is not by any means "extreme", but it does have me a bit stumped considering the circumstances.
I have been working with a customer that has a rather eclectic build, and while being fairly mild, the standard sizing procedures I use, have resulted in two turbo failures, with two different engines. The first being on the original engine, corrected by a turbine housing change. The original turbo/engine had a bark on the top end which resulted in the first failure. I replaced the unit, and recommended the next size turbine housing. It was great after that.
The customer wanted a new engine, which I was chosen to build, and it included an upgraded cam, and a bit more fuel.
Fast forward a couple months....
I have personally visited the customer, helped tune in the vehicle, all the vitals are excellent, boost/drive is as good as it gets. The same turbo setup from the other engine now barks like it did before the turbine housing change on the last one. That indicates more exhaust flow through the system, but ratios are still in check, I witnessed it with my own eyes (1:1-1.1:1, and he sees sub drive ratios at altitude 10-12k ft), everything about the vehicle is great, but it's eating turbos.
His setup has a ton of volume, the turbo probably has 12 feet of 2.5" exhaust pipe feeding it, and 6-8 feet of 3" charge pipe post IC feeding the manifold.
My theory is that the excess volume in the system is causing the turbo to overspeed (especially at 5-12k elevation) and it's a matter of the turbo not being big enough.
This rig runs and performs beautifully, but it's eating turbos at elevation, despite vitals being excellent. My recommendation was to get a bigger unit on it for wheel speed sake, but keep a similar turbine housing A/R.
I appreciate any info guys, thanks.
Sent from my moto g(7) power using Tapatalk
__________________
1989 Bronco- 7.3 IDI/ZF swap (401whp/835wtq@40psi untuned, H4H 2015)
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08-03-2020, 11:11 AM
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#2
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Name: Leiffi
Title: Too Much Time
Status: Not Here
Join Date: Jan 2013
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Posts: 1,381
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Piping volume does not cause overspeed but there is more pressurized air flowing backwards when compressor surges, so it might make more damage.
Change to smaller compressor wheel, problem solved.
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08-04-2020, 08:06 PM
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#3
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Name: 56cummins
Title: Too Much Time
Status: Not Here
Join Date: Mar 2014
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Posts: 733
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What discplacement? What are the turbo specs?
__________________
95 cummins
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08-04-2020, 08:40 PM
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#4
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Name: Snedge
Title: Comp Diesel Sponsor
Status: Not Here
Join Date: Sep 2006
Location: Western Pa.
Member`s Gallery
Posts: 18,832
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Fukk. It's like a math problem with nothing but x's.
So... I have no choice but to assume the answer is 42.
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08-04-2020, 10:08 PM
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#5
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Name: J-Pipes
Title: Too Much Time
Status: Not Here
Join Date: Jan 2012
Location: Ohio
Member`s Gallery
Posts: 4,560
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I know nothing about turbocharger systems, but why not through my thought out there! Now I could be wrong on my understanding of the situation but, you said a bark on top end, so when in a high rpm/high boost situation? And you referenced lots of intake/exhaust plumbing. My guess is maybe a blow-off valve is needed to relieve the pressure that's in the extended piping when the throttle is dumped, and its not going through the engine anymore, that its in effect backing up at the turbo? Again, I'm likely horribly wrong, but hey, even a broken clock is right twice a day, always a chance of being lucky!
Sent from my SM-G975U using Tapatalk
__________________
2000 Dodge ext cab short bed, 6spd.
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08-05-2020, 12:42 PM
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#6
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Name: Ram12vcummins
Title: Too Much Time
Status: Not Here
Join Date: Mar 2015
Member`s Gallery
Posts: 1,659
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Quote:
Originally Posted by J-Pipes
I know nothing about turbocharger systems, but why not through my thought out there! Now I could be wrong on my understanding of the situation but, you said a bark on top end, so when in a high rpm/high boost situation? And you referenced lots of intake/exhaust plumbing. My guess is maybe a blow-off valve is needed to relieve the pressure that's in the extended piping when the throttle is dumped, and its not going through the engine anymore, that its in effect backing up at the turbo? Again, I'm likely horribly wrong, but hey, even a broken clock is right twice a day, always a chance of being lucky!
Sent from my SM-G975U using Tapatalk
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That’ll snap a shaft in half eventually I’d assume. If I’m not careful on my series 60, it’ll give a good bark if I let off fast. Not a good sound.
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