T4 Turbing housing AR question

[xpertsoldier]

Just looking for some information.. What A/R are you folks running on your turbos? I see the HX40 and the BEP housing is only like a .55 if I am not mistaken. Is anyone running a .70 or a .81. Just looking for some info as far as spooling differences and top end. I have both those housing and looking to put on a T67 shortly and looking for options.

Also isn't a .55 for a HX40 kind of small? Or is a .55 on a HX not the same as a .55 on a T4?

 

[LandSpeed-DSM]

Well, it's a bit more complicated than that.

For example, you can't compare A/R between a T3 GT28 and a T3 GT35 housing directly. Just like you can't compare A/R for a Bolt-on housing to a T3 housing, open or divided. Similarly with Open/Divided T3 to Open/Divided T4 or T6.

The "A/R" ratio is to be used for comparing housings of the same flange and style that fit on the same turbine wheel.

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So If you had .69, .82 and .96A/R Open T3 housings for a GT3582R you could compare them directly. Then if you had .58 .62, 1.01 and 1.22A/R T4 Divided for the same 3582R, you could compare those directly to one another.

To compare between the Open T3 and Divided T4 would be much less direct. On the same wheel, a .96A/R Open T3 is going to be "smaller" than a .96A/R Open T4

Comparing Open T3 to Divided T3 for the same turbo can be tricky as well.

Garrett will say that when going from Open to Divided in the same flange style, you would want to select a divided housing 166% "larger" than your open housing for spool concerns. Often spool will improve and it will make more power.

Many people find this counter-intuitive. I have had results that back it up, and so have many reputable groups in the DSM community.

So in the case of a .69A/R Open T3, the equivalent Divided T3 housing would be 1.15A/R. A Divided T4 would be yet "bigger." But not necessarily laggier, and will make more power/psi if the compressor is not already maxed out.

Further yet, as different manufacturers make and measure their housings differently you can't directly compare Borg Warner, Garrett and PTE A/R figures to each other. Or convert nozzle area in cm^2 as listed by Holset and MHI to A/R and compare those directly to the other manufacturers without making assumptions.

Where a manufacturer takes the nozzle area and centroid is not standardized.

Hope that helps.