So I was thinking about the function of the wastegate actuators. The issue that heavier springs help you hold more boost is a simple one.

What exactly are we affecting by tightening the rod? The actual boost is set by the ECU. So is it that the wastegates start to open a bit later causing you to overshoot the boost you want? I suppose this will cause you to bleed off more bboost than you want and repeat the cycle?

Given this train of thought, isn't it best to have the actuator loosened a bit? as opposed to having it too tight?

 

Hey Ari-

I have no idea what you are asking, but howw ya been buddy?

 

Real good. You? Still got the beast? I heard you got rid of it?

 

Yeah, I was spining on this when I did the wastegate upgrade and tried to figure out syncing.

When the WG Actuator is pressurized this overcomes the spring in the wastegate- and allows the rod to move. THis in turn opens the flap in the wastegate of the turbo, releasing the boost pressure

I think there is simply a range in which the DME can effectively control boost. But too loose on the rod and it will take too long for the signal from the DME to acutate the rod and bleed boost - and you can get transient overboosts which can trip an error. Too tight and you will bleed boost quickly.

I've not seen good information on what the calibration should be. Elsewhere I read that 8psi to both wastegates should get some particular rod travel in mm... this was not true for me. I found that 8.5 to 8.75 psi would **just** loosen the wastegate (these are upgraded UMW wastegates).... I wonder if there is any kind of 'learning' algorithm that the DME can actually change how it actuates the N75 valve to achieve optimal boost release. In any event mine have no issues, so I guess I got it right.

A

 

What kind of boost are you seeing? Do you have a Greddy or similar EBC?

I've noticed that peak boost is significantly less when you lift and re-punch mid gear. This obviously pretty common in driving.

You can easily see how a 3150lb 500 (crank) HP Z06 can hang with a stage 4 TT, due to throttle response alone.

I read somewhere that an X50 shoud start to open or "crack" the wasetgate at 12 PSI to readily control boost to 1.1-1.2 BAR (significantly more than 12 PSI of course). I also have modified wastegates. I'll keep posting as I experiment.

 

I think tis is the exact opposite. The tighter you make it, the slower the wastegates respond, making for boost spikes. no?

 

Ari,
you experiencing what every other member does that has upgraded Wg springs.... I went thru ur nightmare 4 years ago.... it was very hard to get the wgs under control...

I had a 40 degree temp drop and all of a sudden the car was doing 1.6 bars vs 1.3 bars...
this is normal... except the stock car has a I believe 7 psi WG spring so no matter how cold it gets it will never hit what your 1 bar spring will in similar Cold conditions...
and contrary to some opinions... I believe that a BOost controller is the most effective way to change the WG spring point of actuation(movement) on boosted and upgraded cars will bigger springs... I can controll the wgs on the go in seconds vs one having to do it manually under the car...
my car usually has .8 bar Tial external WGS... meaning that it will run .8 bars at a minimum with the EBC OFF.... but with a boost controller ON I can turn it 4x or more and get almost 40+psi...
I have been told that the ecu can control the WGs only up to a point...

 

I also like to know more about this. What would happen if I were to install upgraded 1.0 bar WG actuators on a stock car. Would it improve my performance? I know it is a good idea to upgrade your DVs since the stock ones are cheaply made and can easily leak, would this also apply to the stock WG actuators, thanks...

 

Still got it. We need to hook up sometime!

 

I was fortunate enough to have ARD living in my area...and when I bought the UMW wastegate upgrade kit, ARD was generous enough to offer to help me modify and install them since he had done the same to his car. He used a home made pressure gauge that pressurized each side, and we set the PSI at which they opened to right around 8.75. (On one of these forums he shows how to build one of these) This must be right on the money becasue I routinely hit and hold 1.2 bar on boost at WOT. Thanks for the help ARD. The only problem I'm having is I now need a new clutch.

 

Quote:

Originally Posted by ari

I think tis is the exact opposite. The tighter you make it, the slower the wastegates respond, making for boost spikes. no?

I think I misspoke-

As Chuck mentioned above, I developed a pressure source and calibration method when I upgraded my wastegates... I posted a DIY on turboflatsix I think.

Definitions: Wastegate = WG= flap in turbo housing that, when open, releases pressure.

WG Arm= external arm connected to the internal wastegate inside the turbo housing.

Actuator = 'biscuit' sits on the outside of the turbo that when pressurized will extend the rod that goes to the wastegate arm. The Actuator internally is a bladder and spring. The pressure in the bladder ovedrcomes the spring force- the rod out the end of the actuator moves when the bladder expands and the spring compresses.

The wastegate is usually closed. The rod is attached to the WG arm, and inside the Actuator the rod is held closed by the internal spring.

When pressure is applied to the Actuator, the pressure in the bladder overcomes the spring pressure and allows the rod to move and the WG to open.

In the 'inactive' state- the WG is held closed by the internal Actuator spring- this is important as the ability of the actuator to "hold" higher boost pressure is dependent on this spring- the DME supplies pressure to the acutator which releases boost, but the DME can't increase the ability to HOLD pressure.

Inside the actuator there is a bladder that pushes agasint the above referenced spring- when target boost is achieved, the DME activates swtich N75, pressurizes this bladder, overvcomes the actuator spring pressure and the rod move out- moving the Arm and opening the WG.

So, tightening the rod will put more preload on the spring inside the Actuator- since F=kx, this may marginally increase the pressure needed from N75 to open the WG- and it should increase the boost pressure slightly since again the pre-loaded spring is now prviding more force. How much it too much and will cause overboost spikes? Don't know.

I don't have a good handle on what forces and motions look like at WOT...for example why do we see 1.2- (1.3 now that it is cold ) which is ~18-19psi but the actuator begins to open at 8-9psi? I am guessing that things are non-linear as the volumes of moving air increases....


Adam

 

I have tightened down the external rods so that 1" is exposed and my car holds 1.2 bar.

 

Both side the same? Are they pressure synchronized? My UMW modded units run 32mm on one side and 30.4mm on the other side- since they are not symmetric I don't think length is an accurate measurement to sync them...

 

I'm pretty sure that boost pressure helps to keep the wastegate closed as well. Hence the explanation of a 1 BAR wastegate spring holding more than 1 BAR. 1 BAR spring + boost pressure is helping keep the wastegate closed.

The point being made here is that the only thing we are really controlling by tightening or loosening the rod is the response time of the wastegate actuation and hence overshooting or undershooting the desired result. The effect being boost spikes (opening too late) or weak boost buildup (opening too soon) like the factory springs when running above 1 BAR.

I think Markski is right (as usual) in that aftermarket "fuzzy logic" boost controllers can "learn" to compensate for the reaction time of the wastegates. I'm hesitant to run one though because it's one less safety measure we're taking away from the ECU.

While we're on the topic. If you have K24s (or anything that is expected to maintain more than 1 BAR of boost) definitely get upgraded WG springs or wastegates. The difference in mid range torque and high end HP is eye opening.

 

I only went by measurement not pressure synced so it's probably not as accurate as it should be but I had no problems with my stock WG's until we had a temperature drop and I saw my car spike to 1.5 bar I went back to stock settings after that. Now I can't seem to hit 1.2 the highest I get is 1.1 bar I have FVD chip and exhaust on my car. Ii think that I really need to do upgraded WG's and DV's.