Michael Filippello

when should I start hearing exhaust coming from the wastegate dump tube? I just installed my rx6b kit and this is my first experience with a single and an external wategate. I am unfimiliar with all the new sounds and am unsure if things are working correctly. This is what is happening.

As soon as I start going into boost (0-.1bar), I hear the wastegate openning. Is this normal. It will still build boost but leaks the whole way. I am sure it is this because if I disconnect the boost signal from the side nipple, it stays shut. boost builds with out any exhaust noise. I tried hooking it up with the boost controller hooked to the top nipple and then just to a boost source connected to the side nipple. with it connected using just the side nipple, i thought it shouldn't open till I hit the spring rating. Am I wrong in this assumption?

One other thing I was thinking is how does backpressure in the exhaust manifold affect the wastegate functioning? It would seem that the more backpressure in the exhaust manifold, the more pressure on the wastegate valve. This pressure is pushing the valve in the same direction as the boost signal pushes the spring, and the two would have a cummalative affect in overcoming the spring. This is the opposite as to what happens to a blow of valve. Here the boost pressure in the piping is the same as the boost pressure coming in from the line attached to the intake manifold. They therefor negate each other and the spring tension is what keeps the valve shut. when a vacuum is applied to the diaphram it opens the valve. This we know.

So what is causing my wastegate to open so soon?

mike

TurboFD

I have no clue but that seems like a really good question. you should post it again if no one else answers it. I plan to get the rx6 too it sounds like a really good set up. Tell me how you like it once u get ur wastegate problem fixed

-Jim

Michael Filippello

Ok, I took the wastegate off the car for some testing. Here is what I found.

The top chamber is sealed. When you apply pressure to it, it pushes against the spring and help hold the valve closed. If you do not release the pressure via the boost control solenoid, it will remain pressurized. This is why you need a 3 way solenoid with COM, NO, NC, to hook it up correctly.

Now for the bottom chamber. The boost applied via the side nipple leaks out around the piston at what seems a constant rate. This means that if you supply a continuos flow of pressurized air, it will hold the wastegate open the same distance. I checked the spring rate by filling a large air tank to 20psi. I attached one end of the boost line to the tank and the other end to the side nipple on the wastegate. I placed a tee in the line with a boost gauge attached to it. At 20psi it threw the valve wide open. At 15 psi the same. When I got to 10psi, with the tension screw on the back fully turned out, it barely moved. This means that I have a 10 lb. spring. If I turn the preload screw in more, then it takes more psi to move the valve.

This all works great on the bench, but what about on the car. On the bench, there is no force on the wastegate valve. On the car, there is back pressure in the exhaust manifold helping to move the valve in the same direction as the boost signal. I confirmed this by putting a 10 psi signal to the wastgate on the bench. The valve did not open but as soon as I placed my finger on the valve, I was able to open it effortlessly. Without the 10psi signal, it took a lot more force to push the valve open by hand.

I think this is why my wastegate is opening with such little boost. The apex has a small exhaust housing and therefor builds more back pressure. This is even more of a problem on my car since it is street ported. The other problem is that backpressure is not constant so how can boost controll be contant. If operating the wastegate off just the spring by just using the side nipple, one will get different boost levels depending on how much back pressure is in the exhaust at the time (rpm vs load.)

Am I making any sense, or am I missing something? Has anybody else confimed a 10lb. spring? Is this normal operation?

Thanks in advance

mike

BMike

I believe what your epxeriencing is normal, the wastegate slowly opens more and more, the spring isnt an all or nothing deal really, it opens linearly as boost increases, with a good electronic boost controller though it should stay completely shut until you reach the boost controllers preset level <or at least the point where it begins cycling the WG.>

weaklink

sorry, but what is COM, NO, NC?

Michael Filippello

These are the three connections on a boost solenoid.

Com = common , NO = normally open , NC = normally closed.

The COM port will work always and switches between NO and NC when the solenoid cycles.

maxcooper

COMmon
Normally Open
Normally Closed

-Max

Michael Filippello

Has anybody ever experienced compressor surge opening a wastegate? The reason I ask is that I am able to get the wastegate to open by accelerating and decelerating accross the Zero boost line. If accelerate to about 2 psi and then let off and then accelerate after the boost goes back into vacuum, The wastegate will start to open, If I do this again and then accelerate out the wastegate is full open at only 1 or 2 psi.

On the other hand, if I make a steady pull from cruising past 0 and into boost, the wastegate operates normally and won't open till around 7psi.

This makes me think that compressor surge is backing up in the intake plumbing all the way back to the turbo where the nipple for my wastegate is. I was thinking of moving the wastegate line to the intake manifold and see if this will help stabilize the wastegate. I know it should be at the outlet of the turbo, so what gives?

Is it possible that I just have the preload screw to far out on the back of the wastegate or the B.O.V is to stiff?
anybody else have these symptoms? Is That normal and I just never heard it with the old internal wastegate setup or is this thing set too sensitive still?

mike

maxcooper

It is normal for the wastegate to open from compressor surge. It makes kind of a wub-wub-wub Three Stooges noise when you snap the throttle shut after boost. It is normal.

-Max

sub-zero

I had the same problem with that turbo and had to have the BOV set to MIN. and still had the wub,wub. Mike I also had problems with that wastgate. Maybe have it checked over and check that valve guide as it causes problems with sticking open or closed.

Michael Filippello

while looking around to try and find more info on my situation, I noticed that apex has two ways to hook up the waste gate. The one way is how I have it now;

line from compressor hosing to side nipple on wastegate. there is a tee in this line which goes to the boost control solenoid and then to the top nipple on the wastegate.

The other method that apex shows is to connect it the same as above but to also run a line from another tee in the main line coming off the comp. housing and run this line to a nipple on the upper intake manifold.

This would help stabilize the the pressure in the intake plumbing under deceleration when the manifold is in vacuum but the intake plumbing still has pressure. It should also equalize pressure differentials from one side of the butterflies to the other.

Has anyone hooked their wastegate up like this, and did it work better? I am going to change it this weekend and see what happens.

mike

TurboFD

tell us how the new set up works

dclin

iTrader: (4)

Did you get around to trying it Mike? Thanks!

weaklink

back from the dead-still need an answer

Michael Filippello

I know it's been awhile and this post is old, but I forgot to post my results with my wastgate routing. The only way that worked for me was to hook the wastegate to a source from the manifold. If I use a boost signal line coming from the outlet of the turbo, the wastegate opens very early. This would imply that the turbo is making boost very quickly at the compressor outlet before it shows in the manifold.

Hey this made me just think about something. I wonder what boost pressure I should see between the turbo and the IC. If it is higher than in the manifold, could something be wrong? I have never thought about this, but it is the only thing that I can think of that would cause the wastegate to open when I am still making very little boost. By hooking the wastegate up to the manifold only, I have eliminated the problem.

by the way. i too have a problem with this turbo having surge with my blow of valve. I am going to try and lower the setting on it. I was told by Matt Scranton last night that Abel told him that these Turbos need large blow off valves to dump all the air. Something about the thrust plates or bearings can get damaged if we don't use a good enough blow of valve. I am going to switch to a Type R.

mike

devlman

iTrader: (13)

Good info Mike, thanks. I have the same setup and problem and am going to try this new setup you mentioned. I'm using the Apexi twin-chamber BOV and hope it's going to do the trick, but since I'm leaking so much pressure under boost through the WG now it's hard to tell. How'd yours turn out?

setzep

Yes, you need a BOV that will vent enough air to prevent compressor surge. Make sure you get a adjustable one. I have mine set to crack at 19"hg, at idle I'm at 17-18". You want to set it to open at a tad higher vacuum than what you are seeing at idle. But to take a stab at your other problem I think your turbo is too small for the amount of airflow your streetport is wanting to move. According to your other thread it builds boost way to easy with light throttle/airflow.

Michael Filippello

Yeah, this is was i have been thinking/afraid of. If this turbo is indeed undersized for my car, then what to upgrade to. I think I am getting more boost than I need. The key is to find that right size turbo that will still give me the same low end boost but just barely so that there is no waste, too big and then the lag will be greater. I feel that I can go bigger and not loose boost down low. Do you think the gt35/40 would still be too small and I should move to a straight t4 platform.

A friend of mine said he had a lot of luck with a T61 on his seven.

One other thing I just tested, is to see at what psi my wastegate opens with no boost controller hooked up. After rereading this post I remebered that my spring was 10# based on some testing off the car. Now I tested it with the boost control disabled, and it opened at .5 bar. This is less than 10#'s. I have not changed the setting on the wastegate at all and wonder why it is opening earlier on the car than on the bench. Any ideas?

mike

IGY

Nothing is wrong. It's called pressure drop and you will see varying amounts of pressure drop depending on intercooler/piping setup. Does your boost stay pretty steady once it hits peak, or does it fall off, or creep up. If it stays fairly steady (1-2psi change) there is nothing wrong with it. A wastegate must open early (as much as 5psi)so that you don't get a boost spike(goes up then settles down to preset boost). Some electronic boost controllers can keep the wastegate closed longer and still stop spikes and is one of the main reasons they are used. The longer the wastegate remains closed the faster the boost will rise.

devlman

iTrader: (13)

I'm seeing the same thing. I preloaded the spring some more and got the BOV routed differently and am maxing out at about .65bar (9.5 psi) before the WG just dumps the whole load. IGY, can you elaborate on this wastegate control? I'm using an AVC-R and wasn't aware you could tell the WG to stay closed like that. Thanks.

devlman

iTrader: (13)

Oh, and can anyone confirm the following for certain? I've been reading all the related posts and there still seems to be a great deal of debate on this:

Is the spring that currently comes with the Apexi wastegate 10lbs? I've heard 1 bar (~14.5 lbs) as well. And is this at any particular preload/spring tension?

Does anyone know where to get a replacement spring at different tension? All the ones I've found are for TiAL or HKS. Do the HKS ones work?

Thanks