External wastegate questions. I'm very confused.

[hamradio]

So,
I was bored tonight, and went shopping around ebay of all places for a cheap external wastegate.  They seem to be of alright quality, and will last the light use it'll see on my diesel.  

There's a possibility of me getting one from an audi 5000, but I'm not sure, as of yet.

here's the ebay one I was looking at.


What runs an external wastegate?  I thought it was just connected to a line coming from one of the intercooler pipes or intake mani, and when it reached whatever the spring was (we'll say 10psi), the pressure just pushed the wastegate open.  But, I thought I read something about vacuum???  I'm confused.

Second, does it pull the valve inside towards the diaphragm and stuff, to open it, or does it push it outward?  I'm really confused.  Seeing as it appears the line for boost (or whatever happens, I'm not sure anymore) connects to the top, wouldn't it push it open?  But I thought I've seen pics of similar wastegates that pull the valve inside of them?  Or, do some wastegates pull the valve towards them, others push it open?

I hope this all makes sense, I'm confused.

Thanks,
Devan

[jimfoo]

It will open with either pressure(top) or vacuum(bottom). You don't need to connect both, but you should probably put an open line on the unused port to try to keep crud out.

[Benjamin]

external wastegates work identical like internal wastegates, the actuator with the membrame in can be controlled with boost or vacium, alltough, boost is the most easy one in this case. (dont know in what case the vacium is used with gasoline cars)
its important to know, do you realy need an external wastegate?
you can drive without wastegate also, and most turbos do have internal wastegates.

the springs on ebay are around 7psi or so, you probably cant regulate the boost with a boost controller till +20a25psi, also important is the wastegate may not be to big, alltough there is much space. for example, you cant fit a 50 or 60mm wastegate on your diesel, it will simple not work well.

i ever bought an external also, cause of a vnt turbo, but before i installed it there was enough knowledge on the forum to know the boost can be regulated without wastegates also.

Greetz, Benjamin

[hamradio]

I was going to run an external wastegate simply because I do not want to mess with trying to make the little vnt actuator can run on boost.  I've already got the vanes linked to the throttle linkage via a cable and springs; vanes are shut by about 3/4, and open by about 1/4 or so.  Rather than sit and mess with springs and stuff with the vnt actuator, I figured I'd just run the wastegate.  Seems like a few people have done it so far, with decent results.

[Benjamin]

wich vnt turbo is it? and on a 1600td or?
i dont think it will work well with only throttle to the vnt

if the vanes are closed you do have backpressure, its good to make it spool, but in next stadium the turbine will not have enough flow to have enough power to make the compressor work like you want, you see?

at high boost, the vanes need to be opened, with low boost they need to be closed, only if you take a very small turbo it will spoolso fast that you have a problem with boost spike, but remember you are builing a IDI engine, tdi's make it spool faster, see the difrence is you think about boost spike.

Greetz, Benjamin

[hamradio]

at the moment, I'm not really all that concerned.  I was reading some threads, and someone is apparently running a wastegate with no problems.  I'm just looking to do this quick, dirty, and cheap.  I just want the car on the road again.  I can dick around with having boost open the vanes, later, imo.  Plus, if the wastegate is open, it won't be open for long, as I'd quick shift to keep the turbo building boost, right?  The only time I see this as an issue is in an autox course, where the wastegate might be open for a good portion of time.  I'd want a bigger wastegate, so the boost wouldn't slowly creep, right?  I think I've located one from an audi 200tq.  

Really, would it be that big of a deal to have closed vanes and an open wastegate?  Wouldn't the turbo start spooling down as exhaust pressure is let off, and when it got down below, say 10 psi, it'd shut and build boost again?  My manifold has the overboost valve thing on it, too.

[mud and diesel]

Don’t flame me if I’m wrong, but I thought the whole point of a vnt was efficiency, quick spooling is just a result of that. Waste gates vent off potential energy from the exhaust where as a vnt never vents off it just adjusts flow through the turbine to control boost. ?? Is that right?? :oops:

[Benjamin]

at the moment, I'm not really all that concerned.  I was reading some threads, and someone is apparently running a wastegate with no problems.  I'm just looking to do this quick, dirty, and cheap.  I just want the car on the road again.  I can dick around with having boost open the vanes, later, imo.  Plus, if the wastegate is open, it won't be open for long, as I'd quick shift to keep the turbo building boost, right?  The only time I see this as an issue is in an autox course, where the wastegate might be open for a good portion of time.  I'd want a bigger wastegate, so the boost wouldn't slowly creep, right?  I think I've located one from an audi 200tq.  

Really, would it be that big of a deal to have closed vanes and an open wastegate?  Wouldn't the turbo start spooling down as exhaust pressure is let off, and when it got down below, say 10 psi, it'd shut and build boost again?  My manifold has the overboost valve thing on it, too.

if you wanna make the car run asap, just open the vanes full, and drive it with the vanes opened, do use a boost gauge in ANY case. Later you can adapt the vnt controller, this is the safe way to do it.

why not run a T3 / K24, its bolt on, no customs, low cost anyway and you can get nice power also.

i'm not saying you need to make an expensive system, but if the vnt controller dont work well, it will not perform at all, in worste case you will also have a turbofailure cause boostspiking.

Greetz, Benjamin