Upgrading the Sunbird 2.0 T-25 turbo....

[Chas Wiggins]

Are there any bigger/better direct replacement turbochargers for this engine? (the LT4)

For example, will a T3/T4 hybrid bolt directly up to this engine swapped into a Lanos?

[GsiTurbo]

Without changing the manifold, or creating a custom conversion plate, T3-series turbocharger will not bolt on directly onto the stock exhaust manifold. Another option is to cut-off the factory T25 flange and weld in the T3 flange.

Direct replacement would be T28-series turbocharger, like this one.

I will post a pic of a T25-to-T3 flange in a couple of days when I get back home.

Cheers!

[PrecisionBoost]

Hey that GT28RS was just in this months Sport Compact Car.... it's the famous "Disco Potato" turbo thay they loved so much.

They said this was one of the best turbos they have ever used in the 1.8L to 2.2L range.

They said it made more power than the smaller turbos but yet it managed to spool up 1000 RPM before most of them!

They used the GT28RS when it was still in it's design stages at Garrett and it made huge power gains.

Me want a "disco potato"

[daewooluvr]

haha yeah I remember that article about the disco potato

[2 liter turbo]

I'm running a Grand Prix 3.1 turbo on my Sunbird. They're also known as the MacLaren Grand Prix and were made in 1989 and 1990. It's pretty much a bolt on swap, is rated at 36 lbs per min as opposed to the stock T-25's 27 lbs per min and the AR is .80/.63. No quarter miles times yet as the track is closed till spring. It sure feels faster!
Tony

[PrecisionBoost]

Did the Turbo Grand Prix use a T28 or a T25/T28 hybrid?

[GsiTurbo]

Did the Turbo Grand Prix use a T28 or a T25/T28 hybrid?

If I recall properly, it is using same turbo as C20GET, ie Garrett T25.

[2 liter turbo]

To be perfectly honest I'm not sure what the difference is between a T-25 and a T-28. I bought the rebuild kit from Limit Engineering and at one point I believe they referred to it as a T-28 but it could have been a slip of the tongue. Physically it looks just like my old T-25 but the housings are about 1/4" larger in and out. The turbine wheel is identical to the 2.0's T-25 but the compressor wheel is about a 1/2" taller. I think it's a little wider too but I'd have to go and check my notes.
Tony

[daewooluvr]

the T-25 can be rebuilt to be a T-28, that's why.

[2 liter turbo]

But what's the actual difference between a T-25 and a T-28?

[daewooluvr]

But what's the actual difference between a T-25 and a T-28?

From what I'm told the T28 is a better flowing more efficient turbo. It spools at the same rpm as the T25 but gives more boost throughout the RPM range. Look up T25 vs T28, I'm sure you'll find something.

[PrecisionBoost]

The T28 has larger compressor and turbine wheels than the T25.

The T28 should make more boost but your mass air flow (lbs/min) has to be high enough to drop it into an efficent area on the compressor maps.

I don't think the 2.0L will have any problem at all with the T28, infact it's better suited to the engine than the T25 which was only designed for 7-9 psi of boost.

So if you want to run 12psi or more you either need a T28 or a T28/T25 hybrid.

GsiTurbo has a nice example of a modified T25, maybe he will post some pictures.

[2 liter turbo]

So since my turbine wheel is the same size as the one in my T-25 but since the compressor wheel and the housings are larger the GP turbo should be a T-25/T-28 hybrid right? That makes sense. Lag doesn't seem any worse but the mid range swell is definitely greater.
Tony

[toofreds]

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[daewooluvr]

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