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MOPAR2YA
06-16-2007, 08:41 PM
I plan on trying this at SDAC, if it works it will be a good compromise between a small turbine for good spool and a larger one for peak power.:thumb:
http://www.turbododge.com/forums/f11/f40/136651-tiii-dual-wastegates-why-u-ask.html

contraption22
06-16-2007, 08:44 PM
If backpressure in the manifold was a problem that could be solved with more wastegate flow... wouldn't you have problems with boost creep?

MOPAR2YA
06-16-2007, 09:57 PM
Not really. I know Larry J was running well over 2:1 backpressure and he was controlling boost, there is a point where backpressure becomes so severe that the wastegate cannot flow enough to control boost. I dont knw if that is at 2:1 3:1 or where. I know on my T3T4 that the stock internal gate could not hold without haveing 3 external spings pulling the flapper closed. Id love to have known what the back pressure was.

contraption22
06-16-2007, 11:49 PM
So why don't the the pros use one wastegate per cylinder and tiny turbines with huge compressors to make quick spooling, high flow turbos?

tryingbe
06-17-2007, 12:14 AM
Pro doesn't need it to be a daily driver?

contraption22
06-17-2007, 12:34 AM
What I am trying to say is that it is likely that you will have the same exhaust pressure no matter how much wastegate flow you have, because the same amount of exhaust energy is going to be needed to maintain the desired boost pressure. If the wastegate you had been using wasn't flowing enough to keep backpressure under control, you would have boost creep. The amount of work the turbocharger has to do determines the backpressure, not how big the wastegate hole is... because the wastegate is going to stay closed until the desired boost pressure is reached, once below that boost pressure, its going to close again.

If it worked, somebody else would be doing it by now... don't ya think?

Ondonti
06-17-2007, 12:51 AM
Or he could be depending on exhaust gas velocity keeping the turbo spooled even though there is less pressure in the manifold.
High pressure in the manifold helps initial turbo spool but then instantly starts to hurt spoolup and power.
But then how do you prevent all that velocity/power from just going out the wastegates...or will there still be enough energy going to the turbine to maintain boost pressure. Will less reversion also help keep the turbine spooled up...

I understand the boost creep idea but

High pressure in the exhaust manifold kills the velocity of the exhaust gases. Dumping some of that pressure would cause the whole exhaust system before the turbo to behave differently so you cant just assume that you will lose the ability to keep the turbo spooled up.

If the exhaust manifold was a wastegate biased design then I could see this being a problem with "too much" wastegate. On that note I think a lot of very successful turbo manifolds used in professional racing of years past have had wastegate biased manifolds (flow to wastegate being more important then flow to turbine) so this might be a similar function as running two wastegates.

my thoughts.

contraption22
06-17-2007, 12:56 AM
Or he could be depending on exhaust gas velocity keeping the turbo spooled even though there is less pressure in the manifold.
High pressure in the manifold helps initial turbo spool but then instantly starts to hurt spoolup and power.
But then how do you prevent all that velocity/power from just going out the wastegates...or will there still be enough energy going to the turbine to maintain boost pressure. Will less reversion also help keep the turbine spooled up...

my thoughts.

You're putting way too much thought into this and ignoring the simple function of a wastegate. A wastegate is not going to work differently just because it is willed to.

If Wallace's turbo needs 30psi of backpressure to make 15psi of boost... then he is still going to have 30psi of backpressure at 15psi of boost even with two wastegates.

Dave
06-17-2007, 12:58 AM
I see where Wallace is coming from. At 15psi it may be around 25% of the exhaust flow opposed to 25psi. Once he hits 25psi there still will be excess exhaust pressure, that pressure then needs to go somewhere. He's not concerned with the flow rate and efficiency of the turbine housing so much as he is of getting everything out as fast as possible. It takes only so much work to produce 25psi, after that the engine is still producing more exhaust pressure than what it was at 25psi. Instead of stacking the exhaust pressure he seems to be taking that wastful backpressure and dumping it out. In a turbo system it's like taking advantage of wasteful energy... twice. :thumb:

Sounds complicated but in theory it should work.

Ondonti
06-17-2007, 12:58 AM
sorry I added more when you typed this, but as I said earlier

I think the existence of wastegate biased turbo manifolds would say that the function of a wastegate can be more then just boost control.

You can keep a turbo spooled up without having high pressure in the turbine manifold.
The idea is to maximise velocity to the turbine to keep the turbine spooled and minimize pressure in the manifold. Thats how you make huge power.

Tony Hanna
06-17-2007, 01:00 AM
So why don't the the pros use one wastegate per cylinder and tiny turbines with huge compressors to make quick spooling, high flow turbos?

Just a guess, but the ammount of energy transfered from the exhaust side of the turbo to the compressor side has got to be equal less friction loss. I would imagine that with the small turbines (and housings) the backpressure would have to be high in order to transfer enough energy to keep the compressor building boost.
Basically what I'm getting at is that by the time you dump enough exhaust with the wastegates to reduce backpressure any reasonable ammount, you're no longer going to have enough energy to drive the compressor.
I may be wrong though...

Edit: you already said that and somehow I overlooked it.:o

Dave
06-17-2007, 01:02 AM
You can keep a turbo spooled up without having high pressure in the turbine manifold.

Only if the amount of exhaust pressure does not exceed what the volume and efficiency of the turbine housing can handle. Past that point it becomes, proclaimed, inefficient.

Ondonti
06-17-2007, 07:51 AM
Only if the amount of exhaust pressure does not exceed what the volume and efficiency of the turbine housing can handle. Past that point it becomes, proclaimed, inefficient.

What does this have to do with my comment? You are talking about the limitations of a turbine housing and I am talking about the fact that high exhaust manifold pressure is not what is needed to keep a turbo spooled.
My example does not talk about the limits of the turbine housing since the purpose of the dual wastegates is to ignore the limites of the turbine housing and simply concentrate on making sure the turbine blades still spin fast enough so that boost does not drop off.
Exhaust gas velocity is much more important in making big power and keeping the turbo spooled then pressure in the manifolds. Pressure kills velocity and causes reversion.
If wallace can decrease exhaust manifold pressure and prevent boost from dropping he should have a huge increase in HP at the same boost level and be able to successfully use more aggressive cams etc. .

Dave
06-17-2007, 08:47 AM
What does this have to do with my comment? You are talking about the limitations of a turbine housing and I am talking about the fact that high exhaust manifold pressure is not what is needed to keep a turbo spooled.
My example does not talk about the limits of the turbine housing since the purpose of the dual wastegates is to ignore the limites of the turbine housing and simply concentrate on making sure the turbine blades still spin fast enough so that boost does not drop off.
Exhaust gas velocity is much more important in making big power and keeping the turbo spooled then pressure in the manifolds. Pressure kills velocity and causes reversion.
If wallace can decrease exhaust manifold pressure and prevent boost from dropping he should have a huge increase in HP at the same boost level and be able to successfully use more aggressive cams etc. .

Sorry I thought you were referring to the turbine housing, not exhaust manifold. My mistake, should've read better.

It is, however, still an issue with what Wallace plans to be doing. I see what Contraption is saying, if you loose too much of that pressure there will be less velocity. But what's the say you will have too much or too little pressure because of the extra wastegate? I think that will ultimately depend on head flow and cam lift/duration.

GLHSKEN
06-17-2007, 09:24 AM
It will be interesting to see the results. Thanks for sharing

MOPAR2YA
06-17-2007, 10:25 AM
Back pressure has litle to do with turbine speed. Stephane was running just under .98:1 with 38 psi intake pressure if I recall Larry J was well over 2:1 with 25 psi intake pressure. Think of accelerating a car, it takes alot of power to get it to 70 mph, but once its there it requires alot less to maintain that speed.

This is a good read...http://en.wikipedia.org/wiki/Variable_geometry_turbocharger
http://www.autozine.org/technical_school/engine/tech_engine_3.htm

If it doesnt work, I will have a wastgate for sale and a block off plate to install, but Im confident it will work.

8valves
06-17-2007, 10:49 AM
I think the existence of wastegate biased turbo manifolds would say that the function of a wastegate can be more then just boost control.


DING DING DING!

That's why real well though out manifolds don't pull 90* from the turbine housing or collector in fron to fit... they pull smoothly from the area entering the turbine. Even better yet, in theory, is the turbine entry tube that drops down into the turbine housing and the straight section goes into a MONSTER wastegate.

Then by using the small AR housing the spool comes on faster but doesn't choke up top.

However, we thought about doing this a while back and came up to the point that it might only help (as far as using the small AR with the big wastegates and a prioritized header design) if your car has the means to hook up the powerband lower in the RPMs. In our cars cases we decided probably not.

I'll be curious to see how it does pulling from that particular location.

Good thought, hope it works!

The Pope
06-17-2007, 12:40 PM
an example of much of this thread is as simple as looking at an SRT 4 turbine and how they get over 300 WHP from a straw size turbo. Most internal wastegates are located at the turbine, which means on a factory style intake you get big reversion and you hurt flow into the turbine by making the exhaust turbulent and changing directions in the scroll. The SRT 4 uses a huge wastegate, not much different than 2 little ones. But much more important it releases the huge exhaust back pressure in the center or the manifold, not one end. Then the tiny turbo doesn't have a valve in its scroll to hurt the smooth flow of exhaust to the wheel. So it isn't the direct need for more wastegate, it is a need for one big one in the right spot to ballence the exhaust for more power, spool up, etc.

MOPAR2YA
06-17-2007, 12:47 PM
I suppose I will find out at SDAC. This may not be the most optimal setup, but its gotta be better than what I had.

turbovanmanČ
06-17-2007, 04:13 PM
Interesting, going to nice to see what happens.

8valves
06-17-2007, 07:38 PM
an example of much of this thread is as simple as looking at an SRT 4 turbine and how they get over 300 WHP from a straw size turbo. Most internal wastegates are located at the turbine, which means on a factory style intake you get big reversion and you hurt flow into the turbine by making the exhaust turbulent and changing directions in the scroll. The SRT 4 uses a huge wastegate, not much different than 2 little ones. But much more important it releases the huge exhaust back pressure in the center or the manifold, not one end. Then the tiny turbo doesn't have a valve in its scroll to hurt the smooth flow of exhaust to the wheel. So it isn't the direct need for more wastegate, it is a need for one big one in the right spot to ballence the exhaust for more power, spool up, etc.

Excellent point, although just plopping a wastegate onto a manifold, or two for that matter, anywhere is not a great idea.

I see people who weld on a wastegate port to their stock manifolds behind cylinder 2 and 3, or 1 and 2... whatever. What happens to the mixture of each individual cylinder when two of them are fighting backpressure into the turbine, and two others are flowing freely out of the wastegate?

The way I see it, if you pull from cylinders specifically, or not near the turbine housing entry without it being equal on all cylinders as far as the amount exposed to the wastegate, you would have quite the issue of cylinder-cylinder tune being different.

Skibbe
06-17-2007, 09:59 PM
Excellent point, although just plopping a wastegate onto a manifold, or two for that matter, anywhere is not a great idea.

I see people who weld on a wastegate port to their stock manifolds behind cylinder 2 and 3, or 1 and 2... whatever. What happens to the mixture of each individual cylinder when two of them are fighting backpressure into the turbine, and two others are flowing freely out of the wastegate?

The way I see it, if you pull from cylinders specifically, or not near the turbine housing entry without it being equal on all cylinders as far as the amount exposed to the wastegate, you would have quite the issue of cylinder-cylinder tune being different.


The flow will equalize in the log pretty quickly, no matter where the easiest exit is. If the wastegate is attached behind 1 & 2, then 3 & 4 may still push some exhaust over to the wastegate when the turbine gets backed up. It's not like there's a wall between 2 & 3 that prevents everything from balancing.

MOPAR2YA
06-18-2007, 09:37 AM
FYI, I made a quick hit in third gear. It only made 20 psi and was sputtering at that. So I welded a washer with about a 1/2 inch hole in the end of the dump tube. Thats dramatically reduced the sputtering, I wonder if its still a little to big of a hole. I also thought about making a seperate pressure line from the compressor to the wastegate incase the pressures of modulating back and fourth between gates. If I dont get it 100% down, Im bringing a blockoff plate....

tryingbe
06-18-2007, 03:18 PM
What turbo are you using?

Tony Hanna
06-18-2007, 03:20 PM
Pretty sure He's running a Holset HX35 with a Bullseye turbine housing.

Dave
06-18-2007, 11:20 PM
The flow will equalize in the log pretty quickly, no matter where the easiest exit is. If the wastegate is attached behind 1 & 2, then 3 & 4 may still push some exhaust over to the wastegate when the turbine gets backed up. It's not like there's a wall between 2 & 3 that prevents everything from balancing.

I suppose that could work if your turbine flange was in dead center of the manifold. But if we are using our log manifold where the flange is behind 3 and 4, you install the WG port behind 1 and 2 those cylinders will dump a considerable greater amount of exhaust out than 3 and 4, which should cause turbulence in the manifold, and if I remember my physics, turbulence reduces pressure which reduces velocity. Anyways, off topic, but what I'm getting at is pressure will ALWAYS look for the easiest path to escape.

I'm not saying you're wrong and I'm not trying to be arrogant, I'm just trying to find out what's correct. But then we get into the question, is this something that a typical driver will notice? I doubt it, but when you're looking for those extra .01 off the 1/4 then I suppose a stable boost threshold such as what Wallace is trying to achieve may become really essential.

Another thought with unequal port pressure... if there is such a restriction stacking behind 2 cylinders, will that not cause some exhaust gasses to recycle back into the valve? I'm sure it's not perfect stock, but when you start modifying the WG system, it may not work out too well. It seems it's working alright for Wallace thus far.

MOPAR2YA
06-19-2007, 12:02 AM
Hx-40. What Ive learned is a ton at this point. I took it for a quick spin yesterday. I normally run 25 psi rock solid. With the dual wastegates it made 20 psi and had horrible wastegate flutter. You could see the boost gauge very rapidly shaking around the 20 psi mark. So I took it back pulled the 1.5 inch dump tube and welded a washer on the end with a 1/2 hole in it. It raised the boost, but still had some flutter.

I have 2 things to do, 1- run seperate boost signals to each wastegate and see what it does, if no improvement, hook up pressure to the tops of the wastegates as well. This will stabilize the wastegates. Im fairly certain that using a Tee in the wastegates now is causing the pressure to go back and forth between the gates caussing flutter. Im not giving up, but I dont know it will be ready for SDAC. I can always grab a HX35 turbine and then have a whole host of housing to chose from.

Tony Hanna
06-19-2007, 05:23 AM
Pretty sure He's running a Holset HX35 with a Bullseye turbine housing.


Hx-40.

Oops.:o

Ondonti
06-19-2007, 06:56 AM
DING DING DING!

That's why real well though out manifolds don't pull 90* from the turbine housing or collector in fron to fit... they pull smoothly from the area entering the turbine. Even better yet, in theory, is the turbine entry tube that drops down into the turbine housing and the straight section goes into a MONSTER wastegate.

Then by using the small AR housing the spool comes on faster but doesn't choke up top.

However, we thought about doing this a while back and came up to the point that it might only help (as far as using the small AR with the big wastegates and a prioritized header design) if your car has the means to hook up the powerband lower in the RPMs. In our cars cases we decided probably not.

I'll be curious to see how it does pulling from that particular location.

Good thought, hope it works!

I can see why tricks like wastegate placement are huge in road racing though.
being able to come out of ANY corner in the fat of your powerband is vital.

8valves
06-19-2007, 01:03 PM
I can see why tricks like wastegate placement are huge in road racing though.
being able to come out of ANY corner in the fat of your powerband is vital.

Absolutely.

Wastegate fluttering is often the result of exactly what I mentioned... one or two cylinder dumping out of the tube with the others trying to feed the turbine. What you're hearing is basically open port off of one or two cylinders. Sounds like a chainsaw built by Harley!

Find a video clip of the old turbnetics cast manifold for DSM's. It pulls from cylinder number 1 only and has a TERRIBLE flutter sound.

Putting boost pressure to the top ports should help the valve not flucate as easily either.

puppet
06-20-2007, 11:49 PM
So the WG's should be located in the manifolds turbine entrance.

8valves
06-21-2007, 07:07 AM
So the WG's should be located in the manifolds turbine entrance.

That's a good way for a constant flow and from all of the cylinders.... but not good for disrupting air as it's trying to get into the volute of the turbine. :o

2.216VTurbo
06-21-2007, 10:45 AM
So if I am following the popular theory correctly, the gate should be at a point that all cylinders feed somewhat equally and in a direction that doesn't cause turbulence or turn the direction of the exhaust flow...


Kinda like...

The guy who made this manifold for me (eight or so years ago) used to make stuff for turbo Joe Morgan who had a 9 sec 2.3l Pinto turbo. He said the first EX header he made for Joes car had the wastegate dump not in line with the exhaust gas flow, when the gate opened, boost would spike like crazy. He thoerized the header was actually scavanging from atmosphere instead of leeting out pressure. Pretty hard to believe but he changed the dump location on the next header and the spike was fixed:)

8valves
06-21-2007, 11:24 AM
Exactly. That, or more of a divided V, one leg going to the turbine and one leg going to the gate, is what I would consider one of the more optimal systems out there for power and boost control.

Your's there is near identical to how my gate is pulled, but I have two for each merged runner.

Too bad 8V cars have all that clutter of intake and battery, wiring, shifter cables, TB, upper and lower IC pipes bla bla for turbo placement to be more logical there like your Masi. I've always wanted to see a nice picture of your cars setup there. Very cool!

8valves
06-29-2007, 07:56 AM
Wallace, did you give up or did you get it to work?

2.216VTurbo
06-29-2007, 11:16 AM
Ya know Wallace, I tried to talk with and spend some time with all of the online gang at SDAC so I could place a face with everybody. I don't think I managed that with you:o Maybe if I'd been sober for part of the meet:D ... Next year for sure though:eyebrows:

mcsvt
06-29-2007, 11:23 AM
The setup was still on the car in the parking lot. Fairly sure he was using it during racing as well. He made the quick 8, but can't remember who took him out... Definitely had the quickest Spirit there! Sorry Fleck ;)

Aries_Turbo
06-29-2007, 11:52 AM
he bypassed one of the gates cause it was fluttering.

Dave
07-01-2007, 02:34 AM
Was he not able to get the vacuum lines hooked up correctly? He mentioned he needed independant sources for each wastegate.

Aries_Turbo
07-01-2007, 02:14 PM
right, he said that he was going to try two independant sources from the manifold and possibly two grainger valves at different settings. so the way i saw it, one had the boost reference hose to the bottom diaphragm of one through a grainger and teed off before the grainger to the top of the other diaphragm to keep it shut.

I figure if he cant keep the boost down below his setpoint (creep) then he can set one to open at one grainger pressure (the setpoint) and then have another grainger at a slightly higher pressure (2psi above the setpoint maybe?) with a bleed after the grainger so it doesnt open the whole way... or instead of a bleed, send some boost to the top of the diaphragm on the higher set wastegate to keep it from opening the whole way.

as long as the boost stays between the settings of the two wastegates, they should stay constant. at least something to try though.

Brian

Brian

The Pope
07-04-2007, 12:04 AM
The flow will equalize in the log pretty quickly, no matter where the easiest exit is. If the wastegate is attached behind 1 & 2, then 3 & 4 may still push some exhaust over to the wastegate when the turbine gets backed up. It's not like there's a wall between 2 & 3 that prevents everything from balancing.

Air stacks, as is has weight and mass. Then comes the issue of exhaust backwash reversion. I guess physics no longer apply's then? In a log exhaust manifold the farthest cylinder has the most pressure. Then as overlap keeps the valves open hot exhaust backwash's between cylinders. This is all VERY OLD NEWS and nothing new and it hasn't gone away just because no one has brought it up in a while.

2 wastegates? I like TUs cast exhaust manifold picture from the SDAC. Thats a good idea for daily drivers and can use a second wastegate in the right place. There are 2 things about a 4 into 1 header, they equalize pressure and flow. Now a second wastegate will help equalize flow a little better. But what it will do best is equalize exhaust pressure. Unless you guys don't consider backwashing 2 cylinders vs 4 a step in the right direction? Cylinders 1 and 2 will go out there own hole vs backing up trying to get past 3 and 4 to the turbo. This means that the pressure at cylinder 1 is less to make the same boost. So in easy terms your friction loss is dropped by getting rid of stacked exhaust, less exhaust pressure to create the same boost at the end of the log.