IWG Holding Boost

[need bb]

I recently moved from an EWG to IWG setup. With the EWG I could easily hold 19psi to redline with a TD05-20G, but I am having difficulty holding high boost to redline using the IWG setup.

 

I upgraded the spring in my IWG to one 7psi stiffer and while this improved the WGDCs, I only gained 1psi at redline even with 100% WGDC. Given the much larger spring I am thinking the issue is beyond the IWG.

 

I did a boost leak check recently and everything checked out fine. Any ideas?

[utc_pyro]

We need a little more information:

 

3-port?

WG spring?

What is your mass flow in this range?

Turbo exhaust housing size?

 

To the first point, presuming you’re using the standard Mac 35A based 3-port (Cobb, Grimmspeed, ect), there isn’t an effective difference between 89% and 100%. See here: http://www.circuitse7en.net/page26.php The stock ECU controls the WGS at ~15HZ.

 

Your spring/preload may be too low for your desired boost level still. Or you’re choking out the turbine housing and there isn’t enough drive energy left to spin the turbine fast enough.

 

Did you pick up mass airflow between the two WGDC settings?

[need bb]

Thanks utc_pyro. See below:

 

Grimmspeed 3 port

The WC spring is stated as 1.7 bar, but with 0% WGDC it acts like a 1 bar spring

Mass flow peaks around 340g/s

exhaust housing is 8cm

 

Moving from the 1.2bar to 1.7bar spring along with the extra WGDC, the mass flow only increased by 2%.

[utc_pyro]

As you're not flowing any meaningful amount more air, it sounds like flow is choked somewhere. You're at 45lb/min which (depending on who you ask) means you're at the max a 20G compressor is rated for. You're also on a TD05H, which will be starting to choke out at those flow numbers. So your flow numbers are right inline with the average 20G on gas. Most 20G builds you see going much further have TD06SL2 turbines in 10cm housings, or EWG's (like you previously had).

 

Remember, flow is more directly proportional to power output than boost. You'll reach a point that the boost increase doesn't raise airflow enough to compensate for the losses producing that boost create.

 

As for trying to push it harder, due to geometry your wastegate may still be creaking open up top due to high EBP. Get a mighty vac and pressurize the wastegate through it's travel to check the alignment. You can see really odd things if it's not acting as direct as possible on the wastegate actuator. You could also try external helper springs, but you're well into the point of diminishing or even negative returns now.

Edited July 13, 2019 by utc_pyro
Added more detail on why you may already be maxed

[need bb]

Thanks! This really helps explain the core issue and thus the benefit of the EWG.

 

Given the 1-2psi lower boost I was able to add 2 degrees of timing back to minimize the power loss with the IWG.