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Why would they lean out the A/F? How far do they lean it out? If anything, I would have thought anti-lag would have been the temperature culprit. But then, the anti-lag is only for a few seconds at a time and the goal isn't to see how much flame shoots out the exhaust.
Lot of tuners like to target around 12.0 A/F. Evos and STIs use to run 10.0 or richer from the factory. Hell, S2k runs 11.0 stock and it's NA. And some like to crank up boost, but then it knocks so they retard timing and that causes EGTs to skyrocket. Among other bad habits. And I recently saw a Garrett turbo come off a twin turbo lambo that was using anti-lag and it was showing initial signs of turbine overtemp.
Lot of tuners like to target around 12.0 A/F. Evos and STIs use to run 10.0 or richer from the factory. Hell, S2k runs 11.0 stock and it's NA. And some like to crank up boost, but then it knocks so they retard timing and that causes EGTs to skyrocket. Among other bad habits. And I recently saw a Garrett turbo come off a twin turbo lambo that was using anti-lag and it was showing initial signs of turbine overtemp.
Anti-lag can generate very high EGTs, especially if kept on too long or poorly configured.
What have overheated regular turbos looked like and what caused them to overheat? Turbos are on many and an ever increasing number of production cars these days from 1L Ford Fiestas to 1.5L Accords and Civics the GT-Rs, Porsches, and AMGs. Are any of them running Mar-M turbos? Aren't some running TiAl? Don't Porsche's have TiAl turbine wheels?
Anti-lag can generate very high EGTs, especially if kept on too long or poorly configured.
What have overheated regular turbos looked like and what caused them to overheat? Turbos are on many and an ever increasing number of production cars these days from 1L Ford Fiestas to 1.5L Accords and Civics the GT-Rs, Porsches, and AMGs. Are any of them running Mar-M turbos? Aren't some running TiAl? Don't Porsche's have TiAl turbine wheels?
Typically the high performance version of a car will get the MarM turbine wheel. For example, the BMW 4.4L V8s used in the non-M cars (so 4xx hp) get inconel turbine wheels. The higher power 4.4L V8s used in the M5/M6 which are 5xxh-6xx hp get MarM. The 310hp Mustang Ecoboost gets inconel, the 350hp Focus RS gets MarM.
I don't know if the current Porsche Panamera uses TiAl, but they did in 2011/2012 and Porsche had to put a stop sale on the car because the turbine wheels were breaking off resulting in turbo oil fires. I think MHI turbos. https://flatsixes.com/cars/porsche-p...bos-fire-risk/
The current Ferrari 488 uses TiAl on its IHI turbos along with ball bearing and abradable coating on the compressor housing. The Ferreri Challenge 488s are melting the turbine wheels however, but Ferrari won't own up to it.
Oh, to add some more info, an overtemped turbine wheel basically looks like a sawzall was taken to the blade inducer.
I found this good paper from MHI from 2008 on turbine wheel and turbine housing materials for 1050C capable turbos and it has a couple pics of overtemped turbine wheel. https://www.mhi.co.jp/technology/rev...53/e453001.pdf
I had the BW paper. It really focuses on housings and the issue was (it was from 2000) that lean mixtures from fuel economy configurations were raising exhaust temps. The second MHI paper was dealing with high temps from the high compression ratios enabled from direct injections heat of vaporization reducing temps: "However, due to the cooling effect of the vaporization heat of the fuel spray that suppresses knocking, the direct-injection engine can maintain a compression ratio comparable to that of the naturally aspirated engine. However, this raises the turbine inlet pressure and increases the load on the turbocharger." The paper they reference is from BMW and SAE paywall protected (a person could purchase a car for what SAE would charge for cited papers).
TiAl is also used for valves, including exhaust valves and piston pins (pre-Brawn Honda claimed 200rpm from TiAl piston pins). In addition to the 2019 Ferrari 488, GM uses Ti Al for the Cadillac CT6's twin turbo, an engine with widespread use and long warranties. Old joke: Why didn't the engineer get married? They calculated with a 50% failure rate they couldn't afford the warranty costs.
Abradable coatings on compress housings? Do you have papers and vendors on that? Abradable coatings are making a presence on piston skirts. Nearly becoming standard on some JE Pistons I've been led to believe. GM used it on the LS9 rotors and I've seen it advertised for rotors. How does it hold up on compressor housings? Has it also been used on oil pumps especially dry sump scavenge stages?
Back to turbine...Koenigsegg has an interesting take on the turbine housing. Instead of using variable vanes or parallel scrolls, it uses a twisted inned and outer volute with a quick spool like diverter flap to create a monotube on demand, presumably to reduce residual gas.
From BW's original EFR technical guide: "We investigated the use of an abradable coating on the compressor cover and got mixed results. Sometimes it yielded an efficiency and boost pressure gain but other times it did not. It also had mixed effects during the startup and cut-in process; effects that are all in need of
further study. This feature will be continued to be evaluated by the BW team and might be released at a future date either on EFR or Airwerks products, or perhaps both."
Should note, that at the beginning of the BW turbo catalog a lot of current racing applications are listed including endurance prototypes, indy, time attack, drift, drag, etc.
Just to confuse this more (attempt at humor), apparently, ZrO2 abradables are used aircraft turbine hot sections to 1350C. Haven't found a turbocharger use...yet...but it isn't hard to image its use in F1.
Oh, to add some more info, an overtemped turbine wheel basically looks like a sawzall was taken to the blade inducer.
I found this good paper from MHI from 2008 on turbine wheel and turbine housing materials for 1050C capable turbos and it has a couple pics of overtemped turbine wheel. https://www.mhi.co.jp/technology/rev...53/e453001.pdf
Abradable coatings on compress housings? Do you have papers and vendors on that? Abradable coatings are making a presence on piston skirts. Nearly becoming standard on some JE Pistons I've been led to believe. GM used it on the LS9 rotors and I've seen it advertised for rotors. How does it hold up on compressor housings? Has it also been used on oil pumps especially dry sump scavenge stages?
Back to turbine...Koenigsegg has an interesting take on the turbine housing. Instead of using variable vanes or parallel scrolls, it uses a twisted inned and outer volute with a quick spool like diverter flap to create a monotube on demand, presumably to reduce residual gas.
I'm pretty meh on that design. I see a whole lot of surface area, so lots of flow surface friction. Plus, I can see that wall not holding up well to thermal cycling and cracking. The old 2007 Acura RDX 2.3L turbo had a variable A/R turbine housing. Inner and outer volutes with a flapper.
Abradable coatings on compressor side are well known now. I checked out a VW Golf R turbo a month ago and it has abradable on the compressor. The trick is the coating has to bond well to the compressor housing but be soft enough to be worn away by the compressor wheel without damaging the wheel. The turbine side is more complicated because of the high EGTs.
07-24-2018, 10:35 PM
