SameerP

So XR4Tic commented that his 2.0 flows as much air at 5600rpm as my T28 1.8 does at 7000rpm.

Now im assuming this is a product of two things; more displacement and a larger turbo.

My question is is there a formula or methodology to determine displacement flow, etc?

Put another way, put my T28 on a built 2.0 like XR4Tic's and i would see spool up at what rpm, and hit the T28's limit at what rpm?

I see how companies say a GT-25 good for 350hp, or a T28 good for 350hp...so is the reason a T28 or GT-25 is too small for the 2.0'ers because they are shooting for 400hp and beyond?

Cheers,
Sameer

Audiboy

your liters of air is approximately your displacement assuming 100% filing. Note with turbo, you get 200% filing or so.

SMOKINA4TURBO

maps will show the airflow the turbo will move and at what efficiency and how fast you got to spin it also.

For instance, I am going for big power, 400+. Right now I got a temporary turbo on the car. It is basically a 300 hp turbo. On the dyno at 10 psi for instance 200hp, crank the boost up to 15 psi and it puts down 275whp. Crank it up to 20 psi and it makes 300whp...wtf gives. These numbers are a little off but just the general idea of what goes on also. At 20 psi the turbo becomes a hot air dryer and is at like 55% efficiency, righ at a bar of boost its at like 75% range which is in the zone.

Point is you can have a big bad 2.0 but the turbo is still the bread and butter and will dictate the main characteristics of how the engine will perform.
Im a little off topic with this one but oh well:-)

JAFO

if it is a geometric progression. i came out at 7083 or so.

SameerP

Mind giving me an example, are you just looking at the A/R or trim of the turbo?

For example:
T25 housing with choice of .64 A/R or .86 A/R
53mm wheel in a 79 trim.

The above is a complete description which can tell you enough?


Cheers,
Sameer

Audi2ptzero

he has a T28 on a built 2 liter. The bad thing is that the T28 will have the hp max out at 5500 rpms just running 19psi, if you run more then that for boost the tq/hp peaks will just come sooner in the rpms.

xr4tic

Displacement alone is worth 12% more airflow at the same boost levels (1780cc vs. 2008cc)

The rest is in compressor efficiency. The higher efficiency leads to cooler air at the same boost levels, so there is more air mass

There are formulas to determine mass air flow, but you need to indicate RPM, displacement, volumetric effeciency, turbo effeciency, and air temp.

Not only does the 2.0 take in more air, it exhaust more air, so theoretically, it can spool a turbo quicker.

Unfortunately, Garret hasn't released the compressor maps for the T28 or the GT series.