WGDC
 

What sort of WGDC should my Impreza 2.5 with gt30 need to make 1.4 bar?

The WG spring is 0.8 bar, it’s fitted with a 3 port boos solenoid.

Currently what seems to happen is it’ll make 1.3 bar but very late on, I have no idea of what the duty cycle is at the moment but I’m meeting up with the mapper again this Saturday coming to hopefully get everything bang on.

Ideally I want it making as much boost as possible low down and to hold it for as long as possible.

The spec is fully built ej25 with 20 heads, avcs on the inlet (not entirely sure if it’s working) gt30 with full breather mods, fmic, custom exhaust full decat etc.

Redline is set @ 7100 and when out last night it was only making 1.1/1.2 bar until very late on then it would peak @ 1.3 bar just before hitting the limiter.

I believe the WGDC needs tweaked, I’m guessing 100% dc means that all air is being bled away and it would be making full boost, and 0% is spring pressure?

Is t better to have 100% or a higher number lower down in the Rev range to achieve maximum boost quickly and then have the numbers lower as the revs go up to try and maintain the boost pressure?

how much duty is a bit like how much string do you need - there's a lot more to it than that like engine compression ratio, how much fuel/timing your running, atmospheric pressure, what brand boost solenoid, how big the intercooler piping is (total volume as well as actual diameter).

by the sounds of things you maybe have a boost leak and the turbo is having to work harder to make your target value, have you tried relocating the boost gauge to the turbo compressor cover to see how much boost your making there vs what's making it into the manifold?

On a 3port at 100% duty yes it's fully activated and all incoming pressure is diverted away from the gate. However hold that 100% duty for too long and you'll end up spiking and overshooting your boost target in higher gears. Say for example you've got 100% duty from 0-4000rpm, then drop to sensible levels because that works well in 3rd. But if you try in say 5th gear, stomp on the pedal at 3500 you could quickly find yourself licking the windscreen when fuel cut prevents something nasty happening.


On that setup I'd be expecting you to be up and running about 3700rpm with a plot something along these lines but smoother (this is the first chart that came to hand and it was at the start of setting up the car)



https://cimg6.ibsrv.net/gimg/www.sco...2a1e73a08e.png


As you can see it ramps up fairly quickly to 1.1bar, drops down and comes back to about 1 bar (MAP readings are absolute so just -1 to get relative/gauge pressure).

Once the wastegate was properly set mechanically and the WGDC tinkered accordingly this car ended up holding a nice 1.2 bar from 3800 right up the limiter.

This is a subject i spent many hrs trying to perfect ! (95 wrx 2 litre tho not 2.5)

As the Guru :notworthy says it depends on many factors and again, as said, what you strive for at say 3100 rpm bites you in the arse at 5k ! Been there tested that lol

I found i could hit 1 Bar at full throttle/load sometimes at 2900 or 3k, hitting 1.4 bar at 3200 and it would stay at this all the way to the redline, nice i thought, until i planted the loud pedal and got full load (around 64 on this particular occasion, must of been a cold nite lol ) and whallop, hits 1.55 bar and i nearly loose my teeth

So after lots of WGDC changes i settled on hitting 1 bar around 3100 and hitting target boost of 1.4 around 3500 and this then gave me room when i wanted full load at higher RPM ranges, it doesnt spike or overboost

https://cimg3.ibsrv.net/gimg/www.sco...a332ac741e.png

ahah but your boost control is old and slow mr rig, newage ECU's are a little more fancy and most of them can do per gear compensations as well as more fine grained adjustment for min/max values.

usually your as handy setting the max value in 4th gear and that helps prevent too much overshoot but on cars with fancy gates/long plumbing runs/different brands of solenoids you sometimes have to get creative with the target values as well as per gear comps/differences in the min/initial value along with some adjustment to the turbo dynamics to get it predictable every time you jump on the pedal.

Ah true, i keep forgetting modern cars can tune per gear and have min /max WGDC values, thanks for reminding me :cry::lol1:

just give in and re-wire your car to run a newage ECU :D