Xr6 Gt35r

[KamikazeR33]

gonna keep an eye on this thread myself as im waiting to c how my t04e with 0.5 a/r comp cover n 1.00 a/r rear housing goes on my rb30det. on the stocker rb25 it hit 1 bar at 3500.... interesting...

im thinkin upgrading the housing to a .6 or 7 n maybe the front wheel also... wat u guys think? the goal for it is 350rwkws, anything more is a bonus

[Warpspeed]

id say wheel sizes are more important than ar's

<{POST_SNAPBACK}>

Quite right, but the trouble is knowing what wheel sizes actually mean.

Look at a 40 year old design of exhaust turbine wheel like a T3. It is shaped like a biscuit, large diameter and skinny around the peripheral edge with the vanes aggressively swirled at the outlet.

Compare that to a more recent ball bearing turbine like a GT25 which is more cylindrical in shape. It looks more like the paddle wheel off a riverboat. Smaller diameter with straighter vanes and a much bigger outlet area. The trim numbers are much higher. The old wheels are like 40 trim to 60 trim, the new ones more like 65 to 90 trim.

Trim is the ratio of areas of wheel outside diameter to eye diameter.

The old skinny wheels had higher tip speeds requiring smaller a/r housings. The flow range was less and they are more difficult to match to different engines. The wheels were heavier too.

New wheels flow much more and have a broader flow range, less rotational inertia, and are much more efficient.

A T3 has a bigger turbine wheel than a T25 (or a T20). The T3 is even bigger outside diameter than a GT25, but the GT25 turbine is a MUCH higher flow turbine than a T3. So actual wheel diameter is not a very good guide to flow when comparing old turbos to the newer ones.

If you want to work out wheel trim and you know the eye diameter (say 41mm) and the wheel outside diameter (say 53mm).

41 x 41 = 1681

53 x 53 = 2809

1681/2809 = 0.598 that would be called a 60 trim wheel (59.8 actually)

So you can see a 40 trim wheel is pretty skinny and a 90 trim wheel is going to be pretty fat. There is no way you could compare them just by overall diameter, but that is what Garrett does. A GT28 is a hell of a lot different to a T28.

[discopotato03]

Some of that is right and some a bit controversial .

You can't really separate the turbine and housing and say one is more important than the other , they are a matching pair working together .

The whole GT28BB is better than T3 thing is because the light weight high speed rotating assembly can move the same or more gas wth less exhaust energy and restriction while being more compact . The ball bearings have less drag losses , particularly at low shaft speeds , but far better shaft support and longer life .

Compressor trims for the GT wheels are mostly between 48 and 56 and turbines 62 and 90 . 76 to 84 seems to be the sweet spot .

Garrett list 6 six bladed 60mm T3 compressors from 35 to 60 trim . There are so many variations in what people loosely call T3 turbines that its not funny .

Its safe to say that GT BB turbos are generally wider range devices but if badly speced or sized don't expect top shelf results .

[discopotato03]

KamikaziR33 I do remember one Jurasic turbo that seemed to work on an RB30ET . It used a split pulsed (twin entry) T3 flanged 1.00 ARR T4 housing/Ptrim turbine . The compressor was a 60-1 in its native cover and back plate . The word was it tore up the pavement at 10 lbs boost . The std exhaust manifold had a fitting welded to it and a 42mm external gate .

The single cam motor used a stage 3 camshaft and idled like a chaff cutter .

This was about 6 or 7 years ago .