A/R question

[03FatBoy]

Just a general question... I have a TE44 and the compressor housing is marked AR .60. Most I have seen or heard about are .63 what is the difference, and what is desireable, or makes it desireable? Always learning here!

Thanks

 

[RUQWKNF]

Compressor covers, just like turbine housings, have their own A/R number.
The TO4E style or E series compressor cover (3" inlet, 2" discharge) have a .60 A/R rating.

TO4E cover.

When you hear these numbers, .63 A/R and .85 A/R thrown around, typically people are referring to the turbine housings A/R number. See this turbine housing pic below.

THB Buick .63 A/R turbine housing.

Typically, the higher the A/R number on the turbine housing, the more stall requirements for spool up. As well as having a higher rpm power band. 95% of street driven Turbo Buicks are happy running the .63 A/R turbine housings. It's when you throw on heads and a cam, that the .85 A/R housing is recommended.

With regards to A/R numbers on the compressor covers, the 3 style covers that we offer for the Buicks, have their own A/R numbers.

E cover = .60 A/R
S cover = .70 A/R
H cover = .75 A/R

The main differences when it comes to compressor cover A/Rs, is mainly to do with charge temps at high boost levels. EX: a Billet 6765 turbo with an E cover, run at 30psi, is going to have a lot higher charge temp vs the same turbo with an H cover. This difference in charge temps at this level, could be worth 10-15hp. But irregardless of extra hp, I would much rather have the cooler charge temps, than have to tax the intercooler that much more.
Hope this helps a little.

Patrick

 

[03FatBoy]

Thanks, Patrick, very informative. My GN is more of a crusing/hobby car than any kind of race car... so at this point, the outlet temperature is not much of an issue I assume.

 

[1chance]

great info, that simplify things