Thread: 4BD1T Turbo Sizing and Performance Prediction.

OK, so put my boost gauge on the exhaust manifold, was spinning off the clock through gear changes, 30+psi, just like watching a tacho.
At 100k with very light throttle it would sit on around 10psi, bit of an incline and it would boost up to 15psi.
Does this help?

Originally Posted by Vern

OK, so put my boost gauge on the exhaust manifold, was spinning off the clock through gear changes, 30+psi, just like watching a tacho.
At 100k with very light throttle it would sit on around 10psi, bit of an incline and it would boost up to 15psi.
Does this help?

Sort of need boost at the same time to compare.
But 100km/h is where it should be.

Ok, so now what? Is that it? Is this turbo no good above 15psi with this engine? Too much back pressure?

Originally Posted by Vern

Ok, so now what? Is that it? Is this turbo no good above 15psi with this engine? Too much back pressure?

The turbo itself is proven good on these engines. The measurements are trying to pin-point other problems to see why you don't have the power you should. I'm really interested in the wastegate settings.
I can't remember what boost you are running right now.

This turbo at full load should produce drive pressure higher than boost till between 2000-2500rpm. Where the drive pressure will keep climbing with rpm.
As load drops and EGT falls the drive pressure rises for the same boost.

So 10psi boost at cruise, 15psi drive pressure is good.
20psi full load 2000rpm, up to 20psi drive is good.
20psi full load 3000rpm could be 25+psi.
20psi accelerating from cold could be almost 40psi drive and still normal.

Lower is of course better. Provided you've got the boost you need.

Drive pressure tells us how hard the turbine is working. If drive pressure is higher than expected then the turbo is either sucking or blowing against some restriction.

Oh ok. Now what about where I am taking my boost reading from? At the moment its direct of the compressor housing, later today I am going to move it to just before the intake manifold. IF I can find the bits, I will do both

Oh running around 22psi

Originally Posted by Vern

Oh ok. Now what about where I am taking my boost reading from? At the moment its direct of the compressor housing, later today I am going to move it to just before the intake manifold. IF I can find the bits, I will do both

Both would be excellent. To see if your intercooler is a bottle-neck. But you've bypassed the IC before with no real change. So it probably isn't.

Exactly, but if I can't do both, where is the most accurate place, my thoughts are after the intercooler. ???