8 psi t25 vs 8 psi t4

[duveeka24det]

I have been reading alot of threads and in one conversation someone said that 8 psi on a t25 is nothing like 8 psi on a t4... My question is if i had two turbo engines everything is the same on them except the turbo's.. One with a nice size turbo and one with a larger one but, both pushing the same psi.. Would one have more hp then the other one...R would i just have one faster because it spools faster?

[maxstillen]

The answer to that question is the bigger the better. With 8psi on those turbos, the t25 will start spooling quicker but once the bigger turbo kicks in it's like the t25 is boostin at 8psi and the t4 is boostin 10-12 psi.

[duveeka24det]

OH alright I hear ya, but I dont understand why...I'm just going to take ur advice and run with it... Im going to use the t3/t4.Ok one more question would the t3/t4 be harder on my engine then the t3 even under the same psi?

[hannibal]

Its simple really. The T25 is smaller than a T4, so even at the same boost pressure, the T4 is moving a larger volume of air. More air means more power.

[WDRacing]

It's not so much the volume of the air being moved, but the temperature of the air itself once it's compressed. This is an example only because I have no idea what the real rpms would be, but here goes.

The T4 compressor would only have to spin at 20,000 rpm to make 8 psi of boost where the T25 would have to spin at 35,000 rpm. So the efficiency of the compressor for the T25 has reached it's maximum where the T4 is just starting it's day. As an example, the older Porsche's used bigger turbo's because they had no room for an intercooler. By using the bigger turbo, they had more lag, but the compressed air charge was cool enough to not require an intercooler. So they accepted the lag but were able to create more power in the end.

It's all about how much work is required for something to move something else. That's just general physics though.

The T3/TO4 is a far better turbo then the T25.

WD

[duveeka24det]

Thank u ... Very well explained....I know what a t3/t4 is but what is a t3/t04... what does the o stand for?

[WDRacing]

T4, TO4 and TO4 with any letter after the 4 are the same. The TO4E or TO4S is simply the most correct form of expressing what you have.

WD

[boznuttz]

Turbos come in many different trims, and A/Rs. Not all T3/T4s are the same.

Read up on this and you will have many of your questions answered:

zerothread?id=226512

[ZiG]

8 psi is pretty much out of the efficiency range of a t25. Once you get into high rpm, the thing won't be able to flow enough air to maintain that pressure, and your boost will drop. I can set my t25 KA to any boost I like, but after about 5500 RPM it drops to as low as 6 psi.

[duveeka24det]

I just randomly picked two different size turbo's so someone could explain this to me...The two turbo's im chosing from is a t3 and t3/t4..

[maxstillen]

If you want more mid to high end power, then go with the T3\T4. U will like it better.