Turbo upgrade options for the e15et

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Turbo upgrade options for the e15et

Post by angel » Sun Aug 20, 2006 6:01 pm

Turbo upgrades for the E15ET

The E15ET came out stock with a t2 turbo. Early models where oil cooled only, whereas the later models where water cooled and high mounted.

There are a few options when upgrading the standard turbo, here are some of the most common ones.

T25 Which came off the Ca18det engines.
T25g Was found on the redtop and s13 blacktop SR20 engines
T28 or T28BB Came out on the S14 and S15 SR20, s14a and s15 japspec engines had the ball bearing units.

The T25 is probably the most common upgrade, it is the smallest of the three with a exhaust housing AR of 0.49 and a compressor housing of 0.48, it spools quick and provides a good amount of boost and response for a standard engine. Usually see full boost between 2500 and 3000rpm.

The T25g is bigger than the T25 with an exhaust of 0.62 and a compressor housing of 0.80. This turbo provides a lot more high end power and is considered a good upgrade for a mildly worked engine. However due to the larger compressor size this turbo is more laggy seeing full boost from 3000 to 3500rpm depending on mods, and may not be desired for someone who wants a quick response.

The T28 or T28BB even bigger yet, with an exhaust housing of 0.64 and a compressor housing of 0.60. This turbo is recommended for the more highly modified engine. Expect to see full boost at around 3800 to 4200 depending on mods and boost (ball bearing unit). I would presume the non BB unit would hit full boost a little later. (have not tested a bush bearing T28, so I can’t fully comment.)

So will these turbo’s bolt straight on?

Well all these turbo’s have the same base flange, (T2 flange) and will bolt straight up to the standard exhaust manifold. However these turbo’s have a different exhaust flange. Instead of the 4 bolt pattern on the T2’s they have a 5 bolt pattern.
This will require a different dump pipe, also a larger one is warranted to allow for the extra flow of the bigger turbo’s.
If money is an issue, a temporary fix is to use the standard dump pipe, it will fit and seal the turbo, however only 3 of the bolts are able to be bolted up. Probably not the best thing to do, but it does work.

The water lines will bolt straight in, as well as the oil line, however it may require a bit of bending, or an easier option if you have the money is a braided line.

There is also the factor of the inlet of the turbo . The t2’s have a inlet pipe off the compressor housing, which a silicon hose can be used to join either another pipe or AFM or pod filter. The turbo’s above do not have this, instead they have a 2 bolt flange. So a pipe with a 2 bolt flange may have to be source or made to bolt to the compressor housing. I believe that most of the T25’s came out with a similar set up as the T2’s, therefore it will not require this 2 bolt flange, and will be set up just like the t2. Something to be considered when making the decision to upgrade.

This is the t2 inlet pipe
This is the t25 inlet pipe. Notie how similar they are

This is the t25g inlet, notice the 2 bolt flange
t25gdraw.jpg (23.28 KiB) Viewed 12 times

The t28 inlet, same as the t25g, 2 bolt flange.
Also the outlet of the compressor housing on the T2’s has no flange, so a silicon house is able to be put straight on, whereas the T25g, T28 and most of the t25’s have a triangle flange at the end of the outlet. This will require you to source a triangular based snout to bolt onto it, so you may once again use silicon hose. Alternatively other people have machined off the flange.

Notice 3 bolt flange
Standard t2 outlet, no flange

One other thing is that the turbo will require rotating so that the oil inlet lines up to the standard position, and the compressor housing outlet lines up to the pipe leading to the throttle body (i.e. the original T2 position). It is not a difficult task, you just loosen all the bolts from the cartridge to the exhaust housing, and give it a tap a with a mallet or similar, WD40 is most likely required.

Bolts in exhaust housing that need loosening

To rotate the compressor housing, get some cir clip pliers and clap down on the cir clip that holds the compressor housing on, then rotate the housing, then release the cir clip once it’s in the desired position.

Circlip is in this slot
A good place to visit is www.nissansilvia.com check their classifieds as they usually have heaps of t25’s and other turbo’s for sale. Expect to pay $150-$250 for a second hand t25 or t25g, around $400-$500 for a t28 and around $500-$700 or more for a good nick t28BB

Article by

Angel Chercoles
Last edited by angel on Mon Aug 28, 2006 8:36 pm, edited 3 times in total.


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