What makes the factory IHI turbo so "bad"?

[great white]

One word.

"Restriction."

One photo.

Have a great weekend everyone!

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Hmm, very interesting pic.

Haven't seen it that way yet.

You really have to wonder why they cast it that way. It would be harder and more expensive to "pinch" it like that than just "rounding it down"...

 

[buddy]

Its a common practice on tight bends. You need to see it from the other aspect to understand. the cobra head widens but flattens to maintain the flow space at a tight radius. The ATT is able to achieve the smooth radius because it sits more foreward which is why it doesnt line up with the intake.

 

[Slim Shady]

Its a common practice on tight bends. You need to see it from the other aspect to understand. the cobra head widens but flattens to maintain the flow space at a tight radius. The ATT is able to achieve the smooth radius because it sits more foreward which is why it doesnt line up with the intake.

That is only partly true, the ATT only sits .5 of an inch further forward, from the centerline on the compressor side than the gm 8. The turbine side is bigger so it actually occupies more area on the opposite side of the turbine housing than the gm 8 does. (not by much) however the gm has that bend for a reason that I can't explain. The radius was made smooth with the gm 8 so I don't know why gm did that.

 

[JiFaire]

The 'cobra head' bend mainains the circumference, but not the XC area, which drops from a circular form to an ellipsoid... ergo, the flowspace is diminished. That's why we use mandrel-bent pipes when we can.

 

[buddy]

Thats not necessarily true. The head can have a larger circumference, its wider but flattened. To match a 3" pipe the elipse would just have to be 4" wide and 2.25" deep to get a 10.2" circumference vs the 9.4" circumference of the 3" pipe.

Or 4.5" wide and 2" deep

 

[buddy]

That is only partly true, the ATT only sits .5 of an inch further forward, from the centerline on the compressor side than the gm 8. The turbine side is bigger so it actually occupies more area on the opposite side of the turbine housing than the gm 8 does. (not by much) however the gm has that bend for a reason that I can't explain. The radius was made smooth with the gm 8 so I don't know why gm did that.

The GM6-8 appears to have moved the elbow forward by shortening the turbine housing and putting the wastegate lever in the elbow. The Gm4 has a longer housing that the wastegate swings in with that tighter bend elbow. Im sure the smooth bend is better, just that the cobra head isnt terrible.

 

[JiFaire]

The GM6-8 appears to have moved the elbow forward by shortening the turbine housing and putting the wastegate lever in the elbow. The Gm4 has a longer housing that the wastegate swings in with that tighter bend elbow. Im sure the smooth bend is better, just that the cobra head isnt terrible.

Isn't that bend the biggest physical aspect change between a GM4 and GM8?

 

[iamdave0887]

Isn't that bend the biggest physical aspect change between a GM4 and GM8?

My GM5 has the exact same bend and wastegate in the elbow as a GM8. Only difference I can see from the outside is that the GM8's wastegate arm sits about an inch further out compared to the GM5, It sits on what looks to be a spacer. There's a sizeable difference between the GM5 and the GM8, even though they look identical from the outside, again save for the height of the wastegate arm. Not sure why. Maybe one of you turbo guys know. That stuff gives me a headache. ):h