How to: Stock WGA spring mod
I'll letcha know, I just did that today. I'll log tomorrow. Anyone had the spring pop off or snap due to heat cycling? I'm a bit concerned about that happening.
Actually... I wasn't going to do this but yep... Imma unload my thesis now:
If the spring is a linear spring (which is most common) then foce doesn't increas dramatically with deflection. This means that adjusting the eyelet on the WGA arm adds pretention to the spring which assures initial cracking pressure is adiquate, but does not actually increase force put on the arm. Adjusting the eyelet also decreases the flapper stroke, which means the maximum boost limiting ability is decreased. This isn't a problem unless it is over-adjusted. The only real advantage that might come from adjusting the eyelet (WGA arm length) would be cracking pressure, which means higher boost spike. The decreased flapper stroke gives the turbo the ability to hold higher boost... because less exhaust gasses escape. Adding the external spring actually sounds quite genius to me because it basically increases the spring's entire curve.. not just an initial pressure.
On a normal WOT pull this is how the WG is working:
During the spool, the WG remains closed.
As boost approaches the target (max) the WGA spring does its deal and allows the WG to open linearly until its open all the way at target boost.
At higher RPM the engine "eats" the boost faster so the boost decreases. This is where the WGA should start to close the WG again. I believe the problem is that when the WGA tries to close the WG at this time the exhaust velocity/pressure is so high that it overcomes the spring pressure. Increasing the pretention will not help in this and decreasing the maximum flapper stroke doesn't help either. The only thing that would help is increased force. This can only come from a stiffer spring or added springs to increase return force.
In summary:
-Adjusting the eylet (WGA arm length) increases pretention which increses boost spike value and may result in higher possible boost values due to decreased flapper stroke.
-Adding another spring or increasing spring stiffness prevents taper and premature opening, all while slightly modifying the boost curve.
So I will test this out tomorrow to see what this single change results in. I'm hoping to maintain 20-21 by redline, while keeping my normal 24-25 at peak torque.
Actually... I wasn't going to do this but yep... Imma unload my thesis now:
If the spring is a linear spring (which is most common) then foce doesn't increas dramatically with deflection. This means that adjusting the eyelet on the WGA arm adds pretention to the spring which assures initial cracking pressure is adiquate, but does not actually increase force put on the arm. Adjusting the eyelet also decreases the flapper stroke, which means the maximum boost limiting ability is decreased. This isn't a problem unless it is over-adjusted. The only real advantage that might come from adjusting the eyelet (WGA arm length) would be cracking pressure, which means higher boost spike. The decreased flapper stroke gives the turbo the ability to hold higher boost... because less exhaust gasses escape. Adding the external spring actually sounds quite genius to me because it basically increases the spring's entire curve.. not just an initial pressure.
On a normal WOT pull this is how the WG is working:
During the spool, the WG remains closed.
As boost approaches the target (max) the WGA spring does its deal and allows the WG to open linearly until its open all the way at target boost.
At higher RPM the engine "eats" the boost faster so the boost decreases. This is where the WGA should start to close the WG again. I believe the problem is that when the WGA tries to close the WG at this time the exhaust velocity/pressure is so high that it overcomes the spring pressure. Increasing the pretention will not help in this and decreasing the maximum flapper stroke doesn't help either. The only thing that would help is increased force. This can only come from a stiffer spring or added springs to increase return force.
In summary:
-Adjusting the eylet (WGA arm length) increases pretention which increses boost spike value and may result in higher possible boost values due to decreased flapper stroke.
-Adding another spring or increasing spring stiffness prevents taper and premature opening, all while slightly modifying the boost curve.
So I will test this out tomorrow to see what this single change results in. I'm hoping to maintain 20-21 by redline, while keeping my normal 24-25 at peak torque.
Okay, just that added spring gave me just under .5 psi at 7K. I went from 18ish to 18.7ish. Perhaps that helps some of you. Here... I'll try to post a pic. (Edit: that's a 3rd gear pull) Looks like an upgraded WGA would be necessary to hold boost better.
Last edited by honki24; Feb 8, 2008 at 06:47 AM.
I just put the spring on my stock evo 8 and went from 18.5 psi to 20psi. Thats indicated by my boost gauge, no datalogging or anything like that for exact #'s. Pulls strong all the way to redline with no spark knock.
I done just the spring over the weekend .
No spring mod @ 25 psi peak = 230 2byt load @ 7000rpms
spring mod + mbc back down to 25psi = 230 2byt load @ 7000rpms
So in other words it did nothing to raise the load , btw there is some preload on my wga arm
No spring mod @ 25 psi peak = 230 2byt load @ 7000rpms
spring mod + mbc back down to 25psi = 230 2byt load @ 7000rpms
So in other words it did nothing to raise the load , btw there is some preload on my wga arm
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Joined: Dec 2007
Posts: 120
Likes: 1
From: New York
so is it safe for us stock evo owners to put this on just to help with boost taper, but not to increase max boost?
my evo sees quite a bit of taper at redline, id really like it to hold better (no leaks). Is it safe to use just the spring? Would you replace the arm or just simply add the spring to the assembly?
my evo sees quite a bit of taper at redline, id really like it to hold better (no leaks). Is it safe to use just the spring? Would you replace the arm or just simply add the spring to the assembly?
Hello,
Just did the actuator mod today, turned it 2 rotations... the max i guess would be 3 rotations...
other than that, i hv a 0.975 mm pill in the hose going from the turbo to the wg, and no pill from the turbo to the solenoid...
with solenoid dc zeroed out, i hv 15 psi (strt wg pressure)... i hvn't done any tuning for the boost with ecuflash yet (wgdc & wg error correction)...
i hv the following problem: wot @ 2000 rpm, boost goes up to 21 psi @3500, then @ 4500 down to 11 psi all the way to 5000-5500, then goes up to 15 psi and holds it till redline... remind u i hv wgdc = 0, load error correction = 0
What would be the problem?? maybe a very small pill?? maybe i hv to add another pill at the solenoid??? before i did the actuator trick, with the small pill and wgdc = 0, i didn't hv this problem. boost didn't go higher than 12 psi no matter what :S
any ideas??
Just did the actuator mod today, turned it 2 rotations... the max i guess would be 3 rotations...
other than that, i hv a 0.975 mm pill in the hose going from the turbo to the wg, and no pill from the turbo to the solenoid...
with solenoid dc zeroed out, i hv 15 psi (strt wg pressure)... i hvn't done any tuning for the boost with ecuflash yet (wgdc & wg error correction)...
i hv the following problem: wot @ 2000 rpm, boost goes up to 21 psi @3500, then @ 4500 down to 11 psi all the way to 5000-5500, then goes up to 15 psi and holds it till redline... remind u i hv wgdc = 0, load error correction = 0
What would be the problem?? maybe a very small pill?? maybe i hv to add another pill at the solenoid??? before i did the actuator trick, with the small pill and wgdc = 0, i didn't hv this problem. boost didn't go higher than 12 psi no matter what :S
any ideas??
Last edited by EE; Feb 13, 2008 at 07:13 AM.
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From: Hurlburt Field, FL
spring is really there to fix boost taper, there is more preload on the wga so you may need to change your mbc setting or your wga duty cycle via ecuflash.
EE
run a vacuum line straight from the nipple of the turn to the nipple of the wga with no restrictor see what you get.
sounds like with the preload from the wga and the restrictor cause it to spike high (21 psi). Then the all air finally caught up to the diaphram of actuator to push the flapper open in the turbine housing (11 psi). Now remember the flapper is not fully open because the wga is preload. So compare to running with a stock preload a little more exahaust gases will hit the turbine wheel (15 psi).
This were you have to go in and edit your wga duty, boost desire load, boost contol offest, & boost error based up your target boost. Not every setting will be the same as you can see from your exprience
With mine I have the turnbuckle all the way down with the spring using the gm 3 port with no restrictor. Running wga pressure I see about 15 psi start boost and 19 by redline.
EE
run a vacuum line straight from the nipple of the turn to the nipple of the wga with no restrictor see what you get.
sounds like with the preload from the wga and the restrictor cause it to spike high (21 psi). Then the all air finally caught up to the diaphram of actuator to push the flapper open in the turbine housing (11 psi). Now remember the flapper is not fully open because the wga is preload. So compare to running with a stock preload a little more exahaust gases will hit the turbine wheel (15 psi).
This were you have to go in and edit your wga duty, boost desire load, boost contol offest, & boost error based up your target boost. Not every setting will be the same as you can see from your exprience
With mine I have the turnbuckle all the way down with the spring using the gm 3 port with no restrictor. Running wga pressure I see about 15 psi start boost and 19 by redline.
Last edited by bnice01; Feb 13, 2008 at 02:45 PM.
adjusting boost from the ecu doesn't work in this case, bcs if i want to make it in such a way to remove the "dip" when i go wot from 2000 rpm, then i'll hv like 35 psi when going at wot from 4500 rpm, if you see what i mean...
i hv to try rmoving the pill, or at least re-installing the original one.
Another way would be turning the turnbuckle 1 rotation instead of 2 and c wt happens... i'll test all this tomorrow
thx for yr help
i hv to try rmoving the pill, or at least re-installing the original one.
Another way would be turning the turnbuckle 1 rotation instead of 2 and c wt happens... i'll test all this tomorrow
thx for yr help