You can see the exhaust housing is enlarged by nearly .4" in diameter. The enlarged surface area is 1.4 times as much.

Couldnt measure the cold side but you can see where they had to machine the volute for clearances for the impeller.

Anyone have a 20g turbo they can take pics of? Would like to see what the other differences would be.

 

http://www.ztechz.net/id1.html

some turbo information, confusing me though. Thought the 20g kits were 10cm^2 but the greddy documents show the hr kit as 8cm^2

going to order 2 greddy 11900141 gaskets for the exhaust.

 

Measured the inlet port.

OD was 3.152
Sidewall thickness was .52
So id is 3.152 - 2*.52 = 2.112

 

Looks like the A/R is different between the different turbos but maybe its an illusion given they are rotated. I don't know if a larger wheel with lower A/R is a good trade off for a higher A/R and smaller wheel (if that is what they've done to maintain spool while increasing top end), especially with an external WG and/or a tubular manifold. For a log manifold it might reduce EBP and make it a worthwhile tradeoff. Here's some data I've collected:

 

My aam down pipes are just a tad over 50mm at the inlet...not liking all the dimension mismatches.

 

That does not mean the A/R is larger or smaller. The A/R is not measured by the size of the exhaust outlet but at the throat of the exhaust inlet. There is a larger turbine wheel in the turbo with larger exhaust outlet.

 

^ yah - i know I was just eyeballing it - just guessing on a different radius and assuming the same inlet - now that I look at it again, I think the A/R is the same as it looks like the markings on the turbine are identical. Cux, could measure it directly to find the A/R. Looks like the data I got from that same link for the table is incorrect or the upgraded 20g is different than the OEM 20g because that direct measurement for the turbine exducer is larger than it should be. The 18g is spot on.

 

http://www.myturbodiesel.com/1000q/t...tm#A/R%20ratio

a good read.

 

I will see about measuring the AR but it should not have changed since the housings are the same, just machined on the inlet and outlet.