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Y-TRY
01-10-2006, 08:58 PM
What is the best way to source the ports on an External Wastegate?

Many diagrams I've seen use a line from the compressor housing to the side port of the wastegate. Other set-ups are sourcing the same wastegate port directly to the intake.

The top port of the wastegate is after the boost controller, which is also either sourced at the manifold, or at the compressor.

I recently saw an HKS diagram that specified NOT to use the manifold for a boost source, but I see cars like Monty's Corvette (www.montygwilliams.com) successfully reference to the manifold.

I've also 'heard-tell' that only one or the other (top or side) port should be used on the wastegate, but not both. And also that the wastegates can be referenced at any point that sees pressure during boost. If that's the case, they could be referenced anywhere in the intake system.

As I understand it now, the side port introduces pressure under the wastegate diaphragm. With enough boost present, this will overcome the internal spring and lift the valve off its seat- bypassing the exhaust gasses from the turbine. Right? So it would make sense to reference this to actual manifold pressure. However, manifold pressure will introduce vacuum into the wastegate during driving, while none of the other sources would.

Can anyone clear this up for me, with some references? I am having an issue with my wastegates and I want to be able to rule out, or re-consider, how they are plumbed. :hmm:

myclone
01-11-2006, 06:54 AM
Many diagrams I've seen use a line from the compressor housing to the side port of the wastegate. Other set-ups are sourcing the same wastegate port directly to the intake.

Ive plumbed the external WG both ways on my Syclone and never noticed any difference in WG performance. I referenced side port off of the intake at first but later moved it to the compressor housing just to clean up the intake area of the engine a little by having one less vacuum/boost line hanging off of it.


The top port of the wastegate is after the boost controller, which is also either sourced at the manifold, or at the compressor.

The top port on mine is always referenced from the boost control where as some ppl reference it to the compressor or intake with the other port open to atmosphere and do most of the boost level tuning by swapping out the WG spring with a lighter or stiffer piece. That works fine IMO for someone who runs the same boost most all the time but I like to be able to fill the tank with race gas and just turn the control up rather than disassemble the WG to swap springs since my WG requires partially disassembling the vehicle to get to it.


I recently saw an HKS diagram that specified NOT to use the manifold for a boost source, but I see cars like Monty's Corvette (www.montygwilliams.com) successfully reference to the manifold.

I ran an HKS boost control for about a year or so refereced off the intake and never had any trouble with it like that. I never noted anything in the instructions that stated not to plumb it into the intake either but then again I never liked the HKS since it was about as user friendly as quantum physics equation written in pig latin IMO.


I've also 'heard-tell' that only one or the other (top or side) port should be used on the wastegate, but not both.

Ive heard of ppl doing that but Ive never actually been able to pick anyones brain that has done it on how it performs.


And also that the wastegates can be referenced at any point that sees pressure during boost. If that's the case, they could be referenced anywhere in the intake system.

My understanding is that as long as the location you pick to reference boost isnt restricted in any way then you can pick a spot that is most convenient for you.


As I understand it now, the side port introduces pressure under the wastegate diaphragm. With enough boost present, this will overcome the internal spring and lift the valve off its seat- bypassing the exhaust gasses from the turbine. Right?

That is correct however it gets more complicated if you run a smaller more restrictive turbine side ("hot" side) since you will need a stiffer spring to not only hold the WG shut to the desired boost level but also to over come the back pressure in the exh. An example would be on my set up where I have to run a 18lb spring to get a base boost (no external WG control just spring pressure) of 14psi since I run a small-ish exh housing. Basically the 14psi of boost plus the exhaust back pressure over comes an 18lb spring and opens the WG at only 14psi of boost. Make sense?


So it would make sense to reference this to actual manifold pressure. However, manifold pressure will introduce vacuum into the wastegate during driving, while none of the other sources would.

Im not aware of any WG diaphram that would be harmed by being subjected to vacuum and Ive checked into quite a few of the domestically available units (Innovative, PTE, ect). The only thing I can think of off the top of my head is that you might see a slight lag in WG reaction due to quick on/off throttle action (like a road course/stick trans set up) where it may take a slight amount of extra time to pull the vacuum off the WG diaphram and pressurize it. I would think that would be an almost immeasurable amount of extra lag in boost control though.


Can anyone clear this up for me, with some references?Im short on time as of right now (not to mention Im on dial up which is painfully slow) so I dont have time to hunt for the write up that is on one of the linked sites from www.syty.net but I'll check later this evening if someone else hasnt chimed in.


I am having an issue with my wastegates and I want to be able to rule out, or re-consider, how they are plumbed. :hmm:

What kind of issues are you having? What kind of WG are you running?


FWIW stuff Ive learned or have picked up from other ppl that we all learned the hard way:

1. Watch your control line inside diameter. Too large diameter of control lines can dampen the response time of a boost control set up. Same thing as too big of an intake port makes for a soggy intake signal since the larger mass of the air in the boost lines takes longer to accellerate/decellerate. I use 6MM ID silicone hose/plastic hard line and it seems to work just fine and some ppl go so far as to use braided line. I havent had any issues with the silicone/hard line up to 26psi so far.
2. I found that running long lengths of soft vacuum/boost lines would cause some lag in boost control due (IMO) to the lines expanding under pressure before over coming the WG spring and actuating the WG. I switched to hard plastic tubing connected to the ports with short lengths of silicone hose which helped quite a bit with boost control at higher boost levels (20psi+).
3. Make sure that where you plumb the reference lines in arent obstructed by factory installed check valves in the vacuum/boost circuit. Ive seen ppl fight boost control issues to the point of insanity only to find out later they had plumbed the WG circuit(s) into the first factory vacuum line they touched which had check valves installed in at other/remote locations from the factory. If youre system is plumbed directly into the intake/compressor you shouldnt have this problem though but its worth mentioning if your using any part of a factory vacuum/boost circuit.
4. Boost control is an application specific type deal where you have to consider a lot of parameters. A low restricion hot side and properly sized WG can use a simple bleader/needle valve type set up and usually provide rock solid boost control where as a restrictive hot side and/or a marginally sized WG will probably require an electronic boost control set up to provide solid control. Some juggling of WG springs of vairous stiffness may be required also.
5. Adding to #4 at relatively low boost the control set up can be a little "sloppy" (so to speak) in my experience but the higher the boost levels the more well set up the boost control needs to be. While I dont have any diagrams or engineering tables to back that up my personal experience is that my set up can be controlled with a simple bleeder valve at ~12lbs but above that I ran into over boost/boost creep situations and had to switch to an electronic control. Some ppl can live with 2 or 3lbs of boost creep but Im tuned just below detonation so in my situation even a 2lb creep is engine destruction.

Disclaimer: Im a drag racer so my set up up spends most of its time either at idle or WOT throttle (or on jack stands :lmao: ) so the things Ive mentioned may very well not be valid for a road course vehicle which spends its days constantly on and off the throttle as well as the fact my set up runs an automatic trans so anyone with a stick may see things totally different.


Yikes....Im late and gotta get to the shop. Hope some of this helped a little.

Y-TRY
01-11-2006, 09:29 AM
To answer some questions:

My wastegates don't seem to be opening. I'm using two HKS Standard 40mm gates with 9.7psi springs. I'm using a TurboXS Dual Stage Boost Controller, also. (The problem still occurs when I bypass the controller). These for two PT-52 turbos with .69 A/R turbines housings.

I have a single stiff line running from the intake, around to the front of the car. In front, I have a vac. manifold "log" where the 'gates, BOV, and BTM all source from. I'm using 6mm Silicone hose from there.

One line from the log is teed into two lines, feeding each side port of the wastegates, respectively. Another line from the log feeds into the inlet side of the controller. The line from the outlet is then teed and connected at the top ports of the wastegates.

I've used a boost/vac gauge and verifired that all points in the line are seeing equal pressure. i.e. the ports at the "log"/manifold pressure/at each component are equal.

For a while there, it's seem to magically stop right at 10psi, with no sign the wastegates were opening (they are currently open to atmosphere, and no noise or soot)

Now, they'll just increase boost as long as your foot is in it. Luckily, it makes for a scary ride and the car would be airborne before overboosting, so I let off (to save my ass and my engine)

myclone
01-11-2006, 02:57 PM
Have you applied shop air to the waste gates to see that they are opening and verify they arent stuck? Ive noted a few times that other ppl that drive their cars sparingly or have extended down time due to mods, long winters, whatever have ran into a over boosting problems in the past.

If I was a betting man I would find it hard to bet that two WGs would stick rather than just one but then again Ive learned that when it comes to cars/engines they tend to suprise you when its least expected.

Anyways, I would verify that the WGs arent stuck by applying shop air (regulated down to ~15psi) and then go from there.

Y-TRY
01-11-2006, 04:22 PM
Besides my tubing as a possible solution to the problem, my more-than-likely diagnosis is this:

I noted that the flanges warped a bit when welding them to the wastegate boxes. So much so, that you really have to torque the WG down to the flange with the bolts to get it to seat. It's like the bevel surface is pushing into the wastegates on both sides. To mount the flange to them, you kinda have to depress the spring in a good 1/4" from where they are at rest. Before welding, you could slide the flange on and spin it around. The dignosis is that the warping is causing the valve to bind in the "pocket" on the flange.

That's my original diagnosis and my main focus right now is to have the flanges and bases mate easily as they did before welding. The tubing thing is kinda a side note, as it was suggested to me that my lines were all wrong. I don't think they are, and you kinda confirmed that.

my72vette454
01-11-2006, 05:39 PM
I used 38 mm tial gates on my vette and I cant get then to go under 11 lbs with 7 lb springs in them. mine seem to be opening as they are sooted up but I have never heard them and they are vented to the atmosphere right under the front fender. The ones I have use a bolt on flange so you can weld the pipe to the flanges and not have to worry about warping the gate body. I guess I need bigger gates so I can get the boost to go lower.

Y-TRY
01-12-2006, 10:08 AM
72vette... I love your signature!! I've done that a time or two myself!

myclone
01-12-2006, 03:28 PM
That's my original diagnosis and my main focus right now is to have the flanges and bases mate easily as they did before welding. The tubing thing is kinda a side note, as it was suggested to me that my lines were all wrong. I don't think they are, and you kinda confirmed that.

While Im at a loss to visualize in detail what youre explaining I think I have an idea and I would agree that the WGs are now bound up due to the warpage and some extra exh soot that collected on them. That would explain why they worked at first but then quit working all of a sudden.

I also agree that 72vettes sig is pretty cool. BTDT myself. :naughty:

Y-TRY
01-12-2006, 04:00 PM
To be more specific- I don't think they are stuck in the flange, I think that the spring rate has increased because they are compressed at rest. The plunger is pushed up a good 1/4". I'm really thinking that the rate is increased, similar to how you increase valve-spring rate by shimming under it. So I think my 9.7 spring is really about 20 right now. I'm going to experiment with some lower springs and see what happens.

To help visualize what I'm saying.... The WG flange has a raised ring on the mating surface. The inside edge of this ring is beveled. This ring goes up into a hole in the bottom of the WG base and the bevel cradles the valve, like a valve seat. I think the ring got out-of-round during welding and it no longer slips easily into the base. It's kinda forced in there by torquing the bolts down. Capice?

Here's the WG, see the flange and raised bevel on the right? That ring no longer fits easily into the base. I had to jam it in there.
https://static1.pt-content.com/images/noimg.gif

myclone
01-12-2006, 06:24 PM
To help visualize what I'm saying....

.........Capice?

Ok, I see now. Hrmm, that flange that the valve rests on doesnt look too awfully high and I would think you would only see maybe a lb or two increase by compressing the spring the height of that inner flange/seat.

Have you applied shop air to the WGs to see if they are in fact not stuck? Using shop air allows you to hear them make a "tap" sound when the WG goes max open then you can hear the same sound when you release the air closing the WG. If you regulate the air pressure down to ~15psi and quickly apply it to your WGs that only have a ~10lb spring you should here them open/close just as fast as you apply or remove the air pressure. Any lag in the WG action vs air application means youve got a sticky WG which needless to say makes for abnormal boost readings.

If the WGs check out ok with full on/off type air application but are still having boost issues you may have to rig up a regulator on the shop air supply to "sneak up" on the WG. Ive ran into a situation where an Innovative Turbo Systems WG would hang up but only intermittently and only by 3lbs. I found it by attatching shop air with a regulator/gauge and slowly applied air pressure until the WG opened while monitoring the gauge. Every 3rd or 4th opening with shop air the WG would hang and it would take a few extra lbs of pressure to open it according to the gauge. It was a new WG so I sent it back to ITS and they replaced it so I never got to tear into it to see what the prob was.

Anyways, Id do some checking with shop air, regulator, and gauge to get a handle on whats going on with the WGs.