Turbo Sizing

(Originally posted some time prior to 2001 and originally posted on the mailing list sometime in the late 90’s)

This article was posted to Nissan SE-R mailing list by Rob Cadle.  This information is a bit dated but the thought process is still sound.  
OEM:

S13 SR20DET:

  • T-25, 60 trim 56mm BCI-1 compressor, 53.8mm 62 trim
  • T-25 turbine, .64 A/R turbine housing. Journal bearings.

S14 SR20DET:

  • T-28, 60 trim 60 mm BCI-1 compressor in T-04B housing, 62 trim 53.8mm T-25 turbine. .64 A/R turbine housing. Ball bearing center section.

S15 SR20DET:

  • Same as S14, but with Inco turbine wheel (instead of GMR), cast divider wall between turbine discharge and wastegate.

Pulsar GTi-R:

  • T-28, 60 trim 60 mm BCI-1 compressor in standard T-3 housing. 79 trim 53.8mm Inco T-250 turbine wheel .86 A/R turbine housing. Journal bearings.

BB SR20DET:

  • T-25. Basically, the same as the S13 Silvia.

HKS:

GT2510:

  • T-28, 63 trim 60 mm BCI-1 compressor in T-04B housing.  62 trim 53.8mm T-25 turbine. .64 A/R turbine housing.  Ball bearing center section.

GT2530:

  • T-28, 63 trim 60 mm BCI-1 compressor in T-04B housing.  76 trim 53.8mm NS-111 turbine. .64 A/R turbine housing. Ball bearing center section.

GT2540:

  • 46 trim 76.2mm BCI-8 compressor in T-04E housing. 76 trim 53.8mm NS111 turbine. .64 A/R turbine housing. Ball bearing center section.

GT2835:

  • I believe that the following is the spec for this, but I could be wrong:  48,52, or 56 trim 71mm BCI-18C compressor in T-04E housing.  84 or 90 trim UHP turbine cut down from 60mm to 56.5 mm  .64 or .86 A/R turbine housing. BB center section.

GT3037:

  • 48,52, or 56 trim 76.2mm BCI-18C compressor in T-04E housing.  84 trim 60mm UHP turbine. .61, .73, .89, and 1.06 A/R turbine housing. Ball bearing center section.

Turbonetics:

Super 60 T-3:

  • This could be about anything, but is usually a 65 trim 60mm BCI-1 compressor wheel in either a standard T-3 or a T-04B compressor housing, with a 62 trim 58.x mm T-3 turbine wheel in a .49 A/R turbine housing.

Stage 3 T3/T-04E hybrid turbo:

  • 40-60 trim 76mm BCI-4 or BCI-8 compressor wheel in T-04E housing. 76 trim 65 mm T31 turbine in .49-.82 A/R housing.

Stage 5 T3/T-04E hybrid turbo:

  • 40-60 trim 76mm BCI-4 or BCI-8 compressor wheel in T-04E housing. 76 trim 72 mm T350 turbine in .63 or .82 A/R housing.

Now, my opinions:

Stock:

The T-25 seems to be OK up to around 1 bar of boost with a 3″ exhaust and no
cat. This can support about 240 whp with no cat. With a cat, I would run
no more than 10-12 psi. Expect about 220 whp.

The S14 T-28 spools really nice, but has the same tiny turbine as the T-25.
It can’t support much more hp. I’d say 240-260 or so wheel hp max. You can
get more power by running more boost, buy you do so at the risk of breaking
things.

GTi-R T-28 is a really good turbo. I think that it is better if you lose
the T-3 compressor housing and get a housing off of the S14. This is a big
improvement. With the T-04B compressor housing, the GTi-R turbo can support
about 16 psi and 280+ wheel hp. Makes pretty good boost by 3500 RPM, too.

HKS:

GT2510 is expensive and only has marginally better performance than the
Bluebird and S13/14 standard turbos. Yes, it has better transient response
because it is ball bearing, but it’s not like a stock journal bearing T25 is
a spool dog. I would personally buy something else first. I don’t think
you will be able to measure any improvement over a standard S14 turbo with
this one, and it costs a *LOT* more.

GT2530: This is a pretty good turbo, but I don’t understand why HKS won’t
offer it with the larger .86 A/R turbine housing. This with the larger
turbine housing will outperform a GTi-R turbo. This should be good for 300
whp and good response from 3000 RPM on up.

GT2540: IMO, this turbo is a big piece of shit. This is my opinion as I
haven’t tried one. But, looking at the maps, it looks like a pile of shit.
I have heard anecdotal evidence from people I respect that it works pretty
well, but I wouldn’t put one my car and find out. There is too big of a
size mismatch between the 53.8mm turbine and the 76mm compressor. Also, it
is insane to run a .64A/R on the turbine given the flow capacity of the
compressor. This turbine and this compressor are both really good on their
own, but they are worthless together. Total mismatch. Save your money.

GT2835: If this turbo is actually what I described above (check to make sure
before you buy), this should be a pretty good turbo. Get the 56 trim
compressor wheel and the 90 trim turbine wheel with a .86 A/R turbine
housing. This should make good boost by 3500 RPM and should support 375-400
or so wheel hp.

GT3037: This is the mother load of turbos. Get the 52 trim compressor and
.73 A/R turbine housing for good street ability and ~400-425 or so whp. Get
the 56 trim compressor and .89 A/R turbine housing is you can live with a
little more lag and want ~475+ hp.

Turbonetics:

Straight T3 is an OK 2.0L turbo. Gets good boost about 3k RPM, will make
about 250-275 whp. Cost and installation is the same as other, larger
turbos, though, so I’d just rather go bigger and take 500 RPM later
response.

Stage 3 T3/T04E hybrid. Get the 50 trim compressor wheel, and only the 50
trim compressor wheel. Get the .63 A/R turbine housing for boost response
by 3500 RPM. This will support about 320 whp. Get the .82 A/R turbine
housing is you can live with full boost ~800 RPM later. This will support
~400 whp.

Stage 5 T3/T-04E hybrid. Only run the .82 A/R turbine housing. If you want
less lag, get a smaller wheel. Run the 60 trim compressor wheel. Don’t run
a 60-1 wheel (shit) or the smaller trim T-04E wheels. This turbo will
support about 475-525 whp (don’t know on the top end–we haven’t maxed one
out yet!). Expect soggy boost response below 4500-5000 RPM.

As an aside, many of the HKS turbos are available from INCON for
significantly less money. They are also a little more flexible about
housing configuration. The guys at INCON disagree with me typically when it
comes to matching on small displacement motors. In fact, many people do. You
can take or leave my advice. Please don’t contact me and say “person x at
company y told me the turbo you spec’d is no good and this other one is
better”. I have heard it all before. Those turbos are what I recommend,
and you can either listen to me or listen to them. I don’t want to play a
game of ‘he said/she said’.

Rob