I'm still a little confused when it comes to the differences in Garrett GT40's and GT40R's. Here is how I understand it:

GT40
- 82mm exducer/50-trim = ~58mm inducer (most efficient from 9-28psi and capable of flowing enough air for around 450bhp within peak efficiency)
- 88mm exducer/54-trim = ~65mm inducer (most efficient from 8-20psi and capable of flowing enough air for around 450bhp within peak efficiency)

GT40R
- 88mm exducer/52-trim = ~64mm inducer (couldn't find a compressor map...?)
- (Does this turbo even exist?) assuming 88mm exducer/56-trim = ~66mm inducer (most efficient up to 25psi and capable of flowing enough air for around 550bhp within peak efficiency)

To figure out the inducer, I'm just going by this formula (which is supplies by Garrett themselves): inducer(sq)/exducer(sq)x100=trim

However, I read that forum member "MFilippello" measured his GT40R inducer out to 61.83mm... How would that work out...? Assuming this IS a GT40R with an 88mm exducer, it would calculate out to be a 50-trim to be the nearest... This sounds wierd. Perhaps measurement in-accuracy?

Anyone with any answers?

 

Why dont you give ATP a call? They seemed very helpful when I spoke to them.

 

I guess this post doesn't help much but they do not list a GT40R in Garrett's catalog:
http://www.turbobygarrett.com/turbob.../downloads.jsp

Or at Precision Turbo
http://www.precisionturbo.net/turboc...tegory_id=3023

BTW Garrett's designations may mean that it's the same as a GT40 with just a BB center section...
http://www.limitengineering.com/GTmodelcode.pdf

Try A-spec, they're always helpful.

 

Actually my measurement was from the tip of one blade to the tip of the bade oppsosite. The problem is that the two blades are not exactly 180 deg from each other. This means my measurement is a little low. I went out and remeasured to compensate, and come close to 63.5. I measured from the tip of one blade to the opposite side of the nut. I then doubled this number and subtracted the width of the nut. Using this technique, I come up with 63.4mm.

Mike

 

sk8world - I don't think they would like it if I bothered them just to answer my questions. I was just curious, and thought maybe there was a better way to explain the lower numbers at around 15psi for the GT40R's...

GQMRacerX7 - I actually compiled most of my info from those links. Yes, the GT40R is just the BB version of the GT40... However, the GT40R comes with different sized inducer than the GT40.

MFilippello - That sounds more like it... However, I wonder why there are no compressor maps released for this trim GT40R. ATP has a compressor map for a 56-trim GT40R, which I've never even heard of... so perhaps they meant to label that map for the 52-trim...?