So conclusion..............
If I'll get TSI kit with t-25 turbo (non ic) 30% gains
t-28 turbo (non ic) much better gains???

 

Hey boe, 5psi=5psi. I don't know where your reading your boost from, but I am talking about what you read in the manifold. Pressure is pressure. If more air is going in you will have a higher pressure. I hate to sound like a d*ck, but I got over 10 yrs tuning and if you believe that a bigger turbo can "sneek" more air in without being read as boost, then I got a bottle of nitrous for ya.

 

5psi on the manifold is not exactly what your looking at... the ability to maintain the flow rate is more important... especialy as rpms increase. If you have 5psi flowing 200cfm and then you take a compressor pushing 5psi but flowing 350cfm you are maintaining a higher supply charge of air going into each cylinder. In essense you car cramming more air faster into the cylinder at the same pressure. This means you'll need more fuel... more fuel more air eqautes to more power if combusted efficiently(ie: no preignition/detonation).

Again i'm not here to argue but you are not thinking the right way in terms of the boost and flow rates. There is a difference between static pressure and flowing pressures. The only thing staying constant in the car is the volume of the cylinders. If you change the flow rate without changing psi you are increasing the volume of air into that cylinder... thus you'll need more fuel and you'll make more power.

There is a breaking point on this as well... as the turbine will reach a state where it is preheating the boost so high that the intercooler can't bring it within range for good combustion... this is where the compressors efficiency comes into play.

For your 5 psi= 5psi theory... take a T-25 set at 5 psi and tune the car... then throw a 20G on the car and set it at 5 psi without changing the fuel for the car. KABOOOOOOOOM goes your engine as the 20G will flow about 3 times the cfm that your T-25 does thus cramming more air per cubic inch into the cylinder at the same pressure.

School is out just kidding but seriously if you have 10 years experience on this then you would not have made your comment as its totally wrong.

 

Yes and no... you will have slightly better gains down low. You will suffer some spool loss of about 200rpms but where the T-28 will dominate is when you start getting into double digit boost. Then you'll start coming into the T-25's max efficiency are where you'll barely be using the T-28. Now that is an overstatement but i think you see my point. The gains will be better with the T-28 and if you want to push further later on the T-28 will allow you more room to grow than the T-25.

Like i said if your looking for low boost and don't want to be super stupid fast later on... T-25 is fine. If you're looking for more boost later and want the title of most stupid fast lancer on the block then get the T-28 or source out a different turbo that has the same flanges.(20G-25G-etc...)

 

I fully understand what your saying Boe, I'm talking about what you'd see on a boost guage. If there's more cfm going in, then it will be noticed in the vacumm system as more boost. With both of these turbos (T-25, T-28) heat will not be an issue untill you start pushing 15 psi as there efficiencies are both at least that high. Now if your talking 5 psi inside of the compressor, then your totally right. A bigger or better flowing area will definately have more cfm to create the same amount of pressure, once its in the motor it will be read as higher boost.

 

Please test that theory on your own car... like i said t into the manifold and read 5psi on a T-25 setup... then just swap the 20G on there and without fuel mods/tuning it differently and run 5psi on the same gauge. When she blow... and she will... let us know how 5psi at the compessor isn't different than 5psi at the manifold and why the cfm at the compressor is different than the cfm at the manifold.

Seriously this isn't a big deal its a proven fact... what your saying is wrong.

This should add to this... on the rally car for RRM we swapped the Big 16G out for the 25G turbo. We were running the Big 16G at about 24psi... when we put in the 25G we started at 10psi and got here up to 16-17psi before running out of fuel. Why did i have to run less boost on the 25G than the Big 16G if, what your saying, 5psi is 5psi.

I should have been running 24psi in the 25G right?? There is no difference right??

The difference is in the amount of air that it is flowing at the same pressure. Flowing 300cfm at 5psi is different than flowing 700cfm at 5psi on a bigger compressor. Its a difference of volume not pressure. Pressure is remaining constant and the volume is changing. Eventually you'll out flow the manifold/piping/head and increasing the turbo size will have a negitive effect. But using a T-25 on this car is in no way taxing this cars volumetric limits. The turbo itself has to work harder to keep up more than anything. The Big T-28 works less hard to provide the same volume. The 20G is hitting a limit on this motor.

Maybe i'm missing your idea/point here for that i'm sorry... but to say 5psi is 5psi is wrong and can/has been proven many times.

 

So should I really get T-28 instead of T-25 or it doesn't really matter with the boost I will be using?

 

T-25 = quicker spool, less potential power

T-28 = SLIGHTLY slower spool, higher potential power

Thats the basics right there its been covered by boe time and time and time again, go with what you feel will work best for you. Personally the Big T-28 works great for me and i do mostly city driving, but to each his own.

 

OK THX a lot, I'll go with T-25 since low boost is the way for me.

 

There you go! Hope, in all this madness, the decision wasn't that hard?

Good luck with your kit... T-25's are easy to find so maybe see if you can get a cheaper kit (less turbo) and source your own. I've been able to find several for around 200 bucks and most for under that. Ebay and local turbo shops are the places to look. Also Eclipse forums.