When A/R data can be misleading
Turbo Mini Forums

I was trying to plot the turbine map for the 998 with the R5 GT turbo over the weekend. What better things are there to do?

Anyway I have the data for the R5GT T2 turbine as 0.35 A/R and 58 trim.

So, I thought, find a turbine map for a turbine of the same spec on the Garret site and use that. One of the GT1544 models is just that, so easy-peasy.

I plotted the data and it just did not look right at all. Boost should have been all in by about 2500rpm or so. I'm getting around 4000rpm with my set up.

So a bit more investigation revealed that the GT1544 has a 42.2 turbine inducer, wheras the R5GT T2 has a 53mm inducer.

Same A/R, same trim but a very different animal. the R5GT T2 has much higher flow and less restrictive.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Well, I know there are also two very different turbine wheels for the R5GT turbochargers - both with the 0.35 turbine housings.

I also remember seeing two tip heights for the R5 turbo's - although I didn't think anything of it at the time..

I do remember changing one T2 for another and being suprised how it seemed to spool up slower. Later on, Fab sorted me out a T2 built with the 0.48 turbine, and it was a flyer; spooled up really quickly.


Lots of strangeness...

Edited by turbodave16v on 8th Nov, 2010.

Hang on - you said 1544 - isn't the 1548 the modern version of the traditional 'T2' ??? I've got one knocking around somewhere if you want me to measure the tip heights or whatever...

The GT1548 is dimensionally similar to the T2, but that is where the similarity ends. It has a 60 trim compressor whereas the R5GT T2 is a 48 trim and the turbine is also a 72 trim compared to a 58 on the T2.

The data for the GT1548 is readily available.

It does say on the garrett website that you should not compare A/R ratios across different framesizes of turbo.

http://www.turbobygarrett.com/turbobygarre...r/acronyms.html

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Having had a 1548 and a 1544 in my grotty mits and comparing to a T2 - the 1548 is definately the more akin to the old-school unit. The 1544 looked more like an IHI than a Garrett. The compressor housing is physically smaller by what felt like a lot as well. I haven't seen my maps for a while, but I recall the 1548 map bore more of a resemblence to the T2 series units than the 1544 as well.

Edited by turbodave16v on 8th Nov, 2010.