6cm 7cm 8cm exhaust housing comparison.

[94awdcoupe]

sat for over an hour staring at these three housings. when I came to the conclusion there is no way this 8cm housing is actually 8cm. it just looked like a much bigger jump in area than you can see between the 6cm and 7cm housings. honestly its really hard to see where they added volume going to 7cm. but just looking at the 8cm it looked huge. you could clearly see there was far more area above the wheel. so i sat and thought some more how i could show you this without spending a huge amount of time. this is what i came up with. i will let the pictures do the talking. but in short my opinion is its at least 9cm.

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[JusMX141]

Which one are you calling the 8cm2 housing? I only see a 6cm2 housing and two 7cm2 housings in your first pic....the 6cm2 is on the far right ("060" below inlet flange- should have 78-11020 on it somewhere), the middle is a standard 7cm2 housing ("070" below inlet flange, should have 78-11830 on it somewhere), and the far left is an Evo III-spec 7cm2 housing which would have 78-13700 cast around the wheel radius if it's a Genuine MHI housing....and your example doesn't appear to be a MHI housing, which may be the reason for the difference in scroll/volute size.

8cm2 housings are stamped "080" with the part number 78-12050 around the wheel radius and would have a 52mm inlet like a 6cm2 housing unless it's ported.

http://www.dsmtuners.com/threads/turbo-housing-id-help-needed.394644/

 

[94awdcoupe]

the coated housings are genuine MHI 6cm and 7cm housings. the last uncoated housing is what i call the 8cm housing. its not a genuine MHI housing. some sell it as 7cm and others 8cm. it has a "a/r .70 " stamp on the housing. no other markings. heck .70 a/r is pretty accurate if you ask me. if you go by the scale :
Turbine Conversion:

Mitsu = Garrett
6cm2 = .41 a/r
7cm2 = .49 a/r
8cm2 = .57 a/r
9cm2 = .65 a/r
10cm2 = .73 a/r
11cm2 = .81 a/r
12cm2 = .89 a/r

 

[JusMX141]

The ".70 a/r" is a Chinese misinterpretation of the "070" tag from a MHI housing. Every Chinese/eBay 16G in existence has ".70 a/r" on the turbine housing.

 

[94awdcoupe]

I would believe that if they were copies of the 7cm. but they are clearly not. they are FAR bigger than 7cm. that was the purpose of this thread if you havent figured that out yet.

 

[serviceguy]

I always believed that the size of the exhaust housing was determined by the area in cm2 of the housing inlet at the flange. Is that not the case?

 

[GST with PSI]

I would believe that if they were copies of the 7cm. but they are clearly not. they are FAR bigger than 7cm. that was the purpose of this thread if you havent figured that out yet.

If it's truly a .70 a/r housing, it's far bigger than a real 8cm housing as well. No wonder you're always claiming the "8cm" housing is so laggy. Have you been using that knockoff .70 a/r housing thinking it's actual a true 8cm housing? If so, that explains why you think the 8cm housing is a lag monster.

 

[donniekak]

If it's truly a .70 a/r housing, it's far bigger than a real 8cm housing as well. No wonder you're always claiming the "8cm" housing is so laggy. Have you been using that knockoff .70 a/r housing thinking it's actual a true 8cm housing? If so, that explains why you think the 8cm housing is a lag monster.

Going from a fp 8cm housing to a mhi 7cm housing on my hta red was a conservative 500rpm difference in spool.

Also, measuring the volume of the volute gives you a cm^3 volume. The cm^2 measurement used is most likely the actual area open to the turbine inducer on the inside of the volute.

 

[GST with PSI]

Going from a fp 8cm housing to a mhi 7cm housing on my hta red was a conservative 500rpm difference in spool.

What (if any) drop off did you see up top with the smaller housing?

 

[donniekak]

What (if any) drop off did you see up top with the smaller housing?

I had to up the boost a few psi to get the same flow. It performed awesome on a 2.3 auto setup.

 

[bastarddsm]

The smallest cross sectional area in the housing is all the matters. Next up is the area of the wheel outlet. The bigger that is the more it expands going into the wheel and possibly does more work.

 

[94awdcoupe]

If it's truly a .70 a/r housing, it's far bigger than a real 8cm housing as well. No wonder you're always claiming the "8cm" housing is so laggy. Have you been using that knockoff .70 a/r housing thinking it's actual a true 8cm housing? If so, that explains why you think the 8cm housing is a lag monster.

i have never even seen this .70 housing till a few weeks ago. I have not ever run one . i have a shelf full of good 6cm and 7cm housing to last me a lifetime. I have driven the greddy 18g with 8cm housing and 5h turbine. it was a nice pump gas turbo. but it was noticeably laggier than a 16g. I have also rebuilt a greddy 18g using a 6cm housing and 6h turbine wheel. The turbo kicked but on a 2.0. felt like a 16g on steriods. spooled like one but didnt lay down after 6500 like 16g does. to memory the funnest pump gas turbo I have run on a 2.0 and light car. (was an evo 1) that turbo sucked in debree and chipped the compressor wheel. I replaced the wheel and cover with 20g because i didnt have another 18g wheel. major disappointment. didnt pull any harder and was about 250 rpm laggier. still a fun turbo but I sorely missed the 18g compressor.

like donnie, 10 years ago there were handful of people that reported switching to the 7cm for the red. they were all happy reports. no one switched back to the 8cm.

 

[94awdcoupe]

I always believed that the size of the exhaust housing was determined by the area in cm2 of the housing inlet at the flange. Is that not the case?

the inlet is not really part of the equation. the a/r is the ratio of the radius of the wheel to area above the wheel. how exactly the numbers are calculated i have no idea. it isnt as simple as having 7cm of space over the wheel. what I do know is a 7cm housing has more area above the wheel than a 6cm housing. i also know when you machine a housing for a larger turbine wheel the housing a/r gets smaller since you made "r" bigger. so a 7cm housing bored for larger 6h turbine would no longer have a true 7cm rating. it would calculate smaller maybe closer to 6cm.

 

[serviceguy]

the inlet is not really part of the equation. the a/r is the ratio of the radius of the wheel to area above the wheel. how exactly the numbers are calculated i have no idea. it isnt as simple as having 7cm of space over the wheel. what I do know is a 7cm housing has more area above the wheel than a 6cm housing. i also know when you machine a housing for a larger turbine wheel the housing a/r gets smaller since you made "r" bigger. so a 7cm housing bored for larger 6h turbine would no longer have a true 7cm rating. it would calculate smaller maybe closer to 6cm.

That makes sense, but I was specifically referring to MHI housing denomination.

 

[bastarddsm]

the inlet is not really part of the equation. the a/r is the ratio of the radius of the wheel to area above the wheel. how exactly the numbers are calculated i have no idea. it isnt as simple as having 7cm of space over the wheel. what I do know is a 7cm housing has more area above the wheel than a 6cm housing. i also know when you machine a housing for a larger turbine wheel the housing a/r gets smaller since you made "r" bigger. so a 7cm housing bored for larger 6h turbine would no longer have a true 7cm rating. it would calculate smaller maybe closer to 6cm.

Not exactly, Mitsubishi housings measure nozzle throat area. The area of the throat is right when it lets the gas enter the wheel is where and that is where it's 6 or 7cm If you measure the area there it will be really close to 6 or 7cm. Now by cutting it for a bigger wheel your moving the throat up in the nozzle, and getting a bigger area. I've verified this on Mitsubishi and holset housings.

Now the a/r. The R is basically meaningless. In a series of housings the R is almost always a constant, and just the area changes. https://books.google.com/books?id=SvG0gq4DxecC&lpg=PA112&ots=-HYApP924h&dq=turbine housing housing nozzle area&pg=PA112#v=onepage&q=turbine housing housing nozzle area&f=false The R really has a minimal effect on the gas flows entrance into the wheel. The nozzle area directly effects the swallowing capacity of the turbine.

 

[94awdcoupe]

I always believed that the size of the exhaust housing was determined by the area in cm2 of the housing inlet at the flange. Is that not the case?

the inlet is not really part of the equation. the a/r is the ratio of the radius of the wheel to area above the wheel. how exactly the numbers are calculated i have no idea. it isnt as simple as having 7cm of space over the wheel. what I do know is a 7cm housing has more area above the wheel than a 6cm housing. i also know when you machine a housing for a larger turbine wheel the housing a/r gets smaller since you made "r" bigger. so a 7cm housing bored for larger 6h turbine would no longer have a true 7cm rating. it would calculate smaller maybe closer to 6cm.

Not exactly, Mitsubishi housings measure nozzle throat area. The area of the throat is right when it lets the gas enter the wheel is where and that is where it's 6 or 7cm If you measure the area there it will be really close to 6 or 7cm. Now by cutting it for a bigger wheel your moving the throat up in the nozzle, and getting a bigger area. I've verified this on Mitsubishi and holset housings.

Now the a/r. The R is basically meaningless. In a series of housings the R is almost always a constant, and just the area changes. https://books.google.com/books?id=SvG0gq4DxecC&lpg=PA112&ots=-HYApP924h&dq=turbine housing housing nozzle area&pg=PA112#v=onepage&q=turbine housing housing nozzle area&f=false The R really has a minimal effect on the gas flows entrance into the wheel. The nozzle area directly effects the swallowing capacity of the turbine.

I disagree with what you say. this picture better describes how a/r is calculated. changing the wheel size to a larger "R" most definitely changes the a/r. and that a/r gets smaller.
http://www.enginebasics.com/Advanced Engine Tuning/AR turbo ratio explained.html

 

[bastarddsm]

No. The A/R is defined by the housing. It is the ratio of the volute/nozzle area divided by the distance from the centroid of the flow area to the center of the turbine wheel. When you cut it for a bigger wheel you do not change either. You only minorly open up the throat if you cut for a larger inducer and remove some tongue. A/R only describes the housing, not the wheel.

That being said, changing the wheel size most defiantly has a much larger effect on the flow/efficiency that just changing the R.

 

[donniekak]

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[JusMX141]

I'd like to know where the Chinese ".70" housings are making up this volumetric gain if the radius is remaining constant within the series. The 8cm2 MHI housings are noticeably larger than a 7cm2 MHI housing in the physical width of the scroll from the outside, and the exhaust flow enters at less of an angle than both the 6cm2 and 7cm2 MHI housings.

That being said, I'd like to see such a comparison done which also includes the MHI 8cm2 housing as well as the Bullseye housing with it's advertised .55 a/r, yet the BEP housing has a much lower mounting position of the turbo and wider volute.

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...and to make matters even more-confusing, the ".63"-advertised PTE bolt-on housing mounts the turbo in a near-stock location (not lower like the BEP housing), doesn't have the wide/centered volute, and is widely-known to flow like absolute dogshit to the point of melting the inducer tips off of turbines on turbos with large rotating assemblies like the 6152. So how could a housing with a larger claimed a/r flow so poorly unless they just pulled the numbers out of the sky?

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So in reality the .55 Bullseye housing is probably closer to .63 and the .63 PTE housing is probably closer to .48.

 

[94awdcoupe]

the a/r of the housing is a function of the wheel size that housing was made for.

.63 on left .82 on the right

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[94awdcoupe]

anyone know how long these china .70 housings last? I dont see any design flaws really. looks like a really nice housing. better question anyone know of anyone who had a 7cm 16g or 68 and switched to this china housing with no other changes?

 

[JusMX141]

They're not great.

I had one erode completely-away right underneath the wastegate hole on a car that was used strictly for endurance races...I assume because the wastegate was open a lot. There was a hole eroded in the housing into the wastegate port which was bigger than the wastegate hole itself.

Might last forever on a daily driver, but if you're pushing it a high-nickel MHI housing is the way to go.

the a/r of the housing is a function of the wheel size that housing was made for.

So the BEP DSM housing would have a floating a/r being that it was used on turbines as small as TD05H and as large as 76/68mm on S300 turbos...and so would PTE bolt-on housings which go from TA34/T327 wheels up to 62mm T350 turbines.

 

[94awdcoupe]

the ceramic coating I use coats the whole housing inside and out. very certain it lowers operating temp of base metal. in effect makes housing last FAR longer without cracking. another benefit is studs no longer micro weld so stripped threads and broke studs becomes thing of the past. havent run a turbo in last ten years without it.

 

[bastarddsm]

tack weld the WG arm bushing in place.