Stupid newbie turbo question

[Siberian]

Explain to me why a bigger turbo makes more power?

I take it if I just replace the T25 with a T28, and leave everything else stock (no MBC), I won't notice any power increase?

Is a bigger turbo a Good Thing simply because it can efficiently flow more air, thus you can use an MBC and achieve higher boost without frying the turbo or heating the air too much?

Point being, the bigger turbo doesn't increase power by itself - it just lets you run more boost, and THAT makes the power?

In other words, would a T25 and a T28 set to 12 psi make the same exact hp? But a T25 and T28 set to 21 psi would be different, because the T25 just can't make the much pressure without shredding itself and heating the air too much?

And I keep reading about the "Big" T28... are there variations?

 

[midnght]

Originally posted by Siberian
1. Explain to me why a bigger turbo makes more power?

2. I take it if I just replace the T25 with a T28, and leave everything else stock (no MBC), I won't notice any power increase?

3. Is a bigger turbo a Good Thing simply because it can efficiently flow more air, thus you can use an MBC and achieve higher boost without frying the turbo or heating the air too much?

4. Point being, the bigger turbo doesn't increase power by itself - it just lets you run more boost, and THAT makes the power?

5. In other words, would a T25 and a T28 set to 12 psi make the same exact hp?

6. But a T25 and T28 set to 21 psi would be different, because the T25 just can't make the much pressure without shredding itself and heating the air too much?

7. And I keep reading about the "Big" T28... are there variations?

In order from 1-7 ( I numbered them for ease of answering )

1. You explained it to yourself in #4

2. Yes you would notice an increase. It has to do with the cfm it flows. The t28 flows more air at the same psi level. Example ONLY:
T25 at 12 psi 190whp
T28 at 12 psi 200whp

3. Simply, YES but you can't just flow more air without more fuel, better way to control it then the stock ECU, Exhaust to get the extra out of the car. Hence the need to upgrade things to run a bigger turbo.

4. If you say it like this, "Point being, the bigger turbo does increase power by itself - it lets you run more boost, and THAT makes the power." And combine that with my answer for Number 3 and you answer yourself.

5. No (see #2)

6. Yes and NO, see # 2 for the air flow at 20psi+ and the T25 won't just shred itself. I have personally run it at 20psi for 4 months and it was still good when I put the 20g on. But it is a good way of putting it. Heated air will partially come from an inadequate (sp) Intercooler (another upgrade)

7. Yes, there are several variations to EVERY turbo out there.

 

[midnght]

Is the t28 the turbo you are going to get for your upgrade path?

 

[Siberian]

Originally posted by midnght
3. Simply, YES but you can't just flow more air without more fuel, better way to control it then the stock ECU, Exhaust to get the extra out of the car. Hence the need to upgrade things to run a bigger turbo.

Thanks for the detailed answers!

I'm only looking to go to around 250 - 275 hp, and I love the idea that the T28 supposedly just bolts on, so that seems the way for me to go.

Will I need to upgrade the injectors, fuel pump, controller, etc. with a T28 to reach that lowly<g> goal?

Said another way, how far can I go with a T28 and otherwise stock equipment? Or can't I?

And is it really true that I can just remove the T25 and bolt in the T28 with no adapters, rerouting things, etc.?

 

[midnght]

Originally posted by Siberian
Thanks for the detailed answers!

1. Will I need to upgrade the injectors, fuel pump, controller, etc. with a T28 to reach that lowly<g> goal?

2. Said another way, how far can I go with a T28 and otherwise stock equipment? Or can't I?

3. And is it really true that I can just remove the T25 and bolt in the T28 with no adapters, rerouting things, etc.?

1. I would, just to make sure everything is safe and sound. You will hit fuel cut with the T28, many go with a set of 550's and sell the stock ones. With that you need to control it with maybe just an s-afc (version 1). All of this and it should come to about $400 or less if you buy used. These items are ok to get used. I know it is a low goal to you, but those numbers in the whp state are more around 290-310 at the flywheel. Just do some searching to get a good exhaust CHEAP.

2. People hit fuel cut at about 16psi or more on the t28. Keep it at a low number and you will be safe until you get the upgrades.

3. Again, yes and no, you can just replace the full turbo but once you take the t25 off you will want to replace some things like washers maybe and all the gaskets. Just call any dsm shop and tell them your plan and they will hook you straight up. Rerouting/adapters are not required.



If you want a good upgrade path for a T28 just say and I will give you a quick rundown.

 

[midnght]

Originally posted by Siberian
I'm only looking to go to around 250 - 275 hp, and I love the idea that the T28 supposedly just bolts on, so that seems the way for me to go.

My 20g was a "BOLT-ON".