If it held 16psi to 6800 with the smaller spring the gate is capable of venting enough exhaust to keep you at 16PSI. Problem is with the stiffer spring the gate can't fully open without more pressure on the bottom port.

First how do you have your vacuum tubing run? Are you only using the bottom port on your WG? Are you using spring pressure alone?

There are a couple things to try before I went cutting on things.

Put the 5.8psi spring back in for all 3 of these.

1.) Use a grainger valve as suggested inline with the bottom port. This should block the boost from entering the WG until your desired boost is set... say 16psi. Then at 16psi the pressure the valve will pop open and the gate will open maintaining your 16psi level.

With the 5.8 spring you say boost immediately went to 5-6psi... If the grainger valve was installed the gate wouldn't' see any pressure until 15-16psi. This should keep the WG closed. Sounds like this would work best for you.

2.) Have you tried the 5.8psi spring with no vacuum going to the WG? IE spring pressure only? Try it... see what it gets you.

3.) "T" your WG supply line. One line to the bottom of the WG and One line through an adjustable bleeder to the top port. This will add additional force to the top of the gate to keep it closed.

For example I run a 12 lb spring in my gate. This nets me 14-15lbs. I then have an adjustable regulator in the cab that slowly adds pressure the top WG port. This adjusts my boost from 15-25lbs from the cab.

[img] http://www.team-integra.net/forum/attachments/forced-induction/1284d1315582146-where-install-manual-boost-controller-wstgate.gif{/img]

 

Problem is it only held 16psi with a 5.8psi spring or the 10psi spring. I want the wastegate to function correcly with just a wastegate spring and reference line to the bottom port. I just have a vac line from the compressor housing to the side/bottom port of the gate. When I put the 15psi spring in and it built boost really fast but it wouldn't bleed off enough to maintain 16psi with that spring and it made 20 before I lifted and got out of it. So it seems by running more boost quicker that it can't recover quick enough to maintain 16psi so i'll just block off the existing placement and move it.

 

Just saying this to try and help. I hate to see people do a ton of work when they could get by with a little. But I’ve always been lazy…

Moving the WG may help. Or it may be a ton of work and not change a thing when a $10 valve and 2 minute install time could fix your problem.

If it held 16psi with a light spring then the gate is large enough and placed well enough to regulate pressure to 16lbs with the correct boost control setup. To say it has to hold 16lbs with a heavy spring in it is makes no sense to me. Who cares what spring is in the gate if it regulates boost how you want it!

To get your desired result which is close to 16psi quickly and constantly…

You need to block the boost signal to the bottom port until 16psi is reached. With a little tuning this should keep the gate closed with the smaller spring and allow you to make 16lbs very quickly and then maintain it in the upper RPM’s.

Also IMO you should have the boost reference form the intake manifold. Readings taken at the turbo can be much higher than at the manifold depending on the setup.

Promise I’ll shut up now and I do wish you the best of luck with it!

 

I understand what you're getting at but whether I hold the gate shut to 16psi with a spring or a valve by the time the gate opens it now can't recover quick enough to hold 16psi since the exhaust pressures are now very high and a lot more volume due to the added boost. With a light spring and lazy to come into boost it allows the gate to bleed it off gradually and it slowly overcomes it until 16psi whereas when the gate stays closed (via a heavier spring or a valve) for longer right until 16psi it seems to become a chain reaction and now it has opened too late and exhaust pressures have already overcame what the gate can emit and boost keeps rising causing the exhaust volume and pressures to keep rising as well. Kinda hard to explain, and either way I respect and appreciate your help, especially earlier in this thread but at this point I think I'll just move it and place it correctly where it will see exhaust flow without having to travel backwards against the flow. I can take that crossover piece off within 10 minutes that just get a hole saw bit and drill into the merge and weld a pipe and flange for the gate. I think it will be worth it in the end to have proper control rather than just a "band aid" fix.

 

Not entirely true. One is installing a stronger spring, one is just hiding the boost until a predetermined level and then letting that pressure hit the spring and force it open.

 

I have my doubts about your wastegate theory above...

Recovery and exhaust gas volume/pressure have nothing to do with it. You've already proved the gate can regulate down to 16psi to redline with the light spring. Your exhaust gas/rpm/flow etc don't change because you change a WG spring. I think you may be over complicating it. It sounds very simple. The gate isn't opening 100% with the stronger spring to regulate boost down to your desired 16lbs. Anytime the gate opens 100% boost should drop down to 16ish where it was with the light spring. A gate is not an ON/OFF valve. It won't expel as much exhaust if it's not open all the way... especially on a low back pressure setup.

If your WG placement was the issue, even the lighter spring wouldn’t regulate the boost down.

 

Ok serious question here:
With a 15psi spring once the gate sees 15psi to the bottom/side port from the vac line attached to the compressor cover and it sees the boost rising, would the gate be open 100% of the way at that point? Wouldn't the gate operate the same way with the lighter spring but your just hiding the boost from the wastegate by installing a "check valve" in the vac line then when it hits 15psi the gate opens 100% again?

 

Ok I see what your saying, I posted this ^^^ before seeing your post. I was wondering if the gate opens 100% with the same springs once it reaches its pressure limit. As far as my wastegate placement being an issue, it def is considering that a 5.5psi spring nets me 16psi.

 

The poundage issued to the spring means jack diddly about actual manifold pressure. A 10lb spring may open at 5lbs or 15lbs depending on the setup. It's difficult to judge the cracking point of the gate vs the 100% open point. Exhaust backpressure acting on the WG valve and boost pressure sources all vary.

On your setup the 15lb spring may crack open at 15lbs and not be fully open till 20... You already know that with your gate 100% open with the light spring you can regulate the boost to your desired levels. If 16psi is your goal... it's not an issue. Block the signal to the bottom port until that point is reached at the manifold... Give it a shot. Worst case you'll be out $10...

 

Well I finally got around to moving my gate. Here is where I have moved it to:

 

Hopefully this will do the trick. I still haven't tested it yet since I haven't made a dump tube. (Before it was open without a tube, but now I may melt a belt it I let it open and just blast downward without any direction) What do you guys think, should this correct my issue? I'm thinking it should have much better flow to the gate then it had before. I did think ahead a bit and didn't hack off the old port and weld it closed but spent the money for a new flange, clamp, and those blockoff plates they make for a tial 44mm. So the old port is still there, just blocked off and I figure if this new location still doesn't do the trick I can always just add another gate and put it in the old location and now run 2 gates if need be (hopefully I want have to).

 

Bumping this back up. With the gate moved to its new location it is doing the exact same thing and has the exact same symptoms as before. Really want to get this figured out, at this point I don't want to do a bandaid fix, I want to be able to put a 6psi spring in the gate and a vac line ran from the side port of the wg to the compressor outlet and get 6psi, which I am not, its still creeping to 16-17psi even with a good wg placement imo. Anyone got any ideas I'm not seeing?? At this point my thinking is that it has to be something really stupid. Tomorrow I'm going to try to replace my vac line in case it has a small hole in it. May try to ref the intake as opposed to the compressor outlet. I also had someone tell me to look for a hole in the diaphragm of the wastegate, I'll check that tomorrow as well hopefully. Any other ideas?

 

He has given a pretty darn good explanation. I feel no need to repeat the exact same thing. Call it a low boost spring if it makes you feel better and a high boost spring. You may just have too much backpressure going on to control it as simply as putting a 6 psi spring in and getting 6 psi. Or the gate may not be big enough.

 

That I would have to disagree with. I think its the other way around. With the tc76 on this motor and same setup it could control boost perfectly for whatever spring I chose to use even with the terrible gate placement, I believe that if you have a lot of backpressure you can screw up a gate placement and still be ok because the high pressures will flow out the gate when it opens no matter where its placed due to the really high pressures. With a better flowing setup and less back pressure I would think your gate placement is more important now and you want good flow to the gate rather than relying on the high back pressure to feed the gate.

 

Sadly I never got a chance to mess with the car today but I'm thinking its not a wastegate placement issue since it acted the same in both locations. I'm going to replace the vac line and try to reference it to the intake instead and see what happens. Then may pull the gate and inspect the internals to see if its functioning correctly.

 

You are right. Less back pressure will make boost harder to control. Order another gate to put in your old spot. 2 gates may control boost the way you described.

Also your new location isn't optimal IMO. You'd want something like the pic below to be optimal. Your placement still leaves exhaust gasses making a 90* turn to come out the gate. Ideally you'd want the gate exit going with the flow of the exhaust. Placing it on a 90 works best. Not always an option I know.

 

The pic above is terrible. Returning the w/g back into the exhaust at 90deg and so close to the turbine discharge itself is about the worst you could configure.

The entry to the w/g might be good, but everything else sucks.

And that rubber oil drain right beside the hot pipe ?? Nuts, that's asking for fire.

To the OP

For clarity, draw a schematic of exactly what you have. IMO gate position looks fine provided it has good free access to both turbine inlet tubes.

Can you control boost to an acceptable "low" level if you remove the w/g spring and try it with the valve allowed to open fully ?

Is ignition timing sensible at higher rpm's, and not exceptionally low which might induce runaway boost ?

 

In the pic it looks like its off the merge at a 90 but its more of a 45. It is right in the merge and just a 45 so it should be decent I would think.

Thanks, I was thinking the placement was good also. Should a 44mm gate be enough to control down to atleast 10psi? Ignition timing is 14 degrees I believe since I'm just 93 pump alone. I never tried removing the spring altogether guess I should try that and see what happens.

 

A single 44mm gate for a big single turbo application does sound pretty small.

 

Its a pt7675 CEA not that big. Shouldn't it still be able to control boost down to say 10psi?