Twins for dumbies

Tree Trimmer · Sep 3, 2011

but didnt charles put the gate right into the housing of his 38r? and that would bleed off pressure exactly where you needed pressure bled off.

i dont know if it makes a difference or not, but to me, given the choice of location of wg placement, the housing would make the best place for it. isnt it the pressure in the housing that makes the difference, not the pressure in the up-pipe? if your bleeding off pressure before it gets to the housing, isnt that taking away from the available velocity of the exhaust. you lose pressure and velocity, as opposed to just pressure. granted, its probably comparable to spitting in a pond, but i wondered, so i asked.

^^i probably murdered the train of thought/choice of words in that paragraph, but im sure you get the idea.

granted, ease of installation/tuning, and available space come into play also, but given the option, isnt the housing the best place for it?

Big Bore · Sep 3, 2011

Tree Trimmer said:
but didnt charles put the gate right into the housing of his 38r? and that would bleed off pressure exactly where you needed pressure bled off.

Yes, but right at the entrance.

i dont know if it makes a difference or not, but to me, given the choice of location of wg placement, the housing would make the best place for it. isnt it the pressure in the housing that makes the difference, not the pressure in the up-pipe? if your bleeding off pressure before it gets to the housing, isnt that taking away from the available velocity of the exhaust. you lose pressure and velocity, as opposed to just pressure.

I disagree with all of that.

TyCorr · Sep 3, 2011

Dzchey21 said:
What i have gathered from set ups like brian's truck is the reason you run two gates is because a single big gate tends to dump pressure too fast, which can make the gate surge and chatter opened and closed, because the gate even opened very slightly is dumping a TON of air, i have no experience with it tho. but it makes sense, if you can basically open on gate wide open, and then start to bring a gate in at the higher rpm to blead any additional back pressure up top if the rpm range.

Im running a single 46mm gate for now, and then if i need more i will add another gate. I also like two gates because there is no real reason two tie both uppipes together (for flow reasons) where with a 60 gate you would have to.

Doesnt a stock type wg only puke from one scroll? I dont think that having a big gate on one upipe would be that horrible. That how I planned on doing mine actually. Unless Im not following you correctly!! Which is a possibility since I spent three g'd*(n hours at home depot today!! FML.

Big Bore · Sep 3, 2011

TyCorr said:
Doesnt a stock type wg only puke from one scroll? I dont think that having a big gate on one upipe would be that horrible. That how I planned on doing mine actually. Unless Im not following you correctly!! Which is a possibility since I spent three g'd*(n hours at home depot today!! FML.

No what he is saying is having to tie the two up pipes to a single WG mount would be a PITA. Whic is why I think the guys running a single WG put it in the exh housing.

I would think wastegating one up pipe would cause some imbalanced flow in the exhaust.

TyCorr · Sep 3, 2011

Big Bore said:
No what he is saying is having to tie the two up pipes to a single WG mount would be a PITA. Whic is why I think the guys running a single WG put it in the exh housing.

I would think wastegating one up pipe would cause some imbalanced flow in the exhaust.

It depends on how the piping is set up...because thats exactly what the stock setup does, really. The internal gate only bleeds from the one side of the scroll. I realize we're talking about gating different parts of the induction system but pressure will equalize itself either when the pipes converge or after passing through the housing. At least they do in my mind.

If you gated one upipe and the pressure coming out of that side, lets pick an easy number, 40psi, and the other side was making 65psi, you'd have one pipe meeting another at different pressure. It would equalize itself immediately after mixing.

TyCorr · Sep 3, 2011

Big Bore said:
No what he is saying is having to tie the two up pipes to a single WG mount would be a PITA. Whic is why I think the guys running a single WG put it in the exh housing.

I would think wastegating one up pipe would cause some imbalanced flow in the exhaust.

Ha ha...I also think that if you're this far into being comfortable with fabrication making a "Y" to send both uppies into one LARGE gate would be fairly easy. I appreciate the input but Im not completely convinced that two gates would be better. Thats me though. Gotta question everything! :thumbsup:

Ill tell you this, a 60mm gate can handle the pressure cycles better than a little guy that is getting hammered by overboost constantly. There should be a way to dampen the larger gate to prevent shudder when it cycles. I may be approaching this all wrong but in the tuner world people had tons of trouble/failures running small gates. Brand matters imo too. Tial is THE gate manufacturer.

Big Bore · Sep 3, 2011

TyCorr said:
It depends on how the piping is set up...because thats exactly what the stock setup does, really. The internal gate only bleeds from the one side of the scroll.

The internal gate was not designed to bypass the type of boost pressure we are talking about here. If it was, people would not be buying non WG housings and putting external wastegates on. However I believe the internal gate is actually bleeding off pressure from both exhaust manifolds

Big Bore · Sep 3, 2011

TyCorr said:
Ill tell you this, a 60mm gate can handle the pressure cycles better than a little guy that is getting hammered by overboost constantly.

Thats why you use two gates, each of which has more area than half the single and it's only bleeding off half the pressure.

Brand matters imo too. Tial is THE gate manufacturer.

I agree, specifically because tial makes a water cooled WG, but only in the 44mm and under sizes.

TyCorr · Sep 3, 2011

Big Bore said:
The internal gate was not designed to bypass the type of boost pressure we are talking about here. If it was, people would not be buying non WG housings and putting external wastegates on.

Right on! I know that. Im just saying that at a lower pressure its doing the same thing right? I think its the physical size of the internal gate in the stock charger and 1.00housing for the 38r that makes it suck. There are pressure inequalities even in stock trucks. Do a wot run on a stock truck and let off...you probably will hear what sounds like a turkey gobbling. Pressure equalizing itself...

Take any charger and any non-wg'd housing add any size plumbing you want and gate one of the two uppies. What will happen? You might create a slight amt of backpressure on the bank that is feeding the wg. Or you might find that nothing is happening because that pressure equalizes when it comes into common space, like the uppipe collector. I would think a little backpressure would allow the gate to function more crisply too.

Ive not done this on a diesel and it may be way outta line with popular thinking but it makes sense to me.

This is one of the best threads in a long time!

TyCorr · Sep 3, 2011

Big Bore said:
Thats why you use two gates, each of which has more area than half the single and it's only bleeding off half the pressure.

I agree, specifically because tial makes a water cooled WG, but only in the 44mm and under sizes.

They dont make a 48 or 60?

http://www.tialsport.com/prod_wg_60.html

TyCorr · Sep 3, 2011

Charles uses one 44mm gate. Its just barely enough. So if one were to go any bigger or not want to run a 44mm gate on the ragged edge a 46 would be much better. The 60 would be overkill even if you were dumping to atmosphere twice what Charles is.

I dont think lack of watercooling on the 46 or 60 would deter me from it.

psduser1 · Sep 3, 2011

Tycorr is correct- by the time the exhaust gas hits the wheel on a standard 1.0 housed 38r, the scrolls are no longer divided. That's why there is one 18.8 mm wastegate, which is woefully inadequate! If you gate before that you'll have a pressure difference between the uppipes, but not at the wheel.
I can't say for a 1.15 housing, cause I don't have one, but Id speculate that its similar. Please correct me if I'm wrong.
That design would make a wastegate most effective when plumbed into a common space, per Charles, rpminc, etc. Less piping, more accessible, so on.

Closer to OP train of thought, if your primary turbo starts the boost, and guys with bigger housings mention slightly increased lag in a compound setup, would a tighter housing, aka 1.0, or even .84 housing minimize that. After all, your looking at a bigger turbo (atomospheric) to handle the top end. Properly gated, of course.
Btw, execellent thread. Keeping the brain cells moving!:thumbsup:

Dzchey21 · Sep 3, 2011

TyCorr said:
Doesnt a stock type wg only puke from one scroll? I dont think that having a big gate on one upipe would be that horrible. That how I planned on doing mine actually. Unless Im not following you correctly!! Which is a possibility since I spent three g'd*(n hours at home depot today!! FML.

no im just saying that a single uppipe doesnt flow what the gate will

Big Bore · Sep 4, 2011

TyCorr said:
They dont make a 48 or 60?

http://www.tialsport.com/prod_wg_60.html

Not water cooled, which is what I was referring to.

Big Bore · Sep 4, 2011

Big Bore said:
The internal gate was not designed to bypass the type of boost pressure we are talking about here. If it was, people would not be buying non WG housings and putting external wastegates on. However I believe the internal gate is actually bleeding off pressure from both exhaust manifolds

That should have read drive pressure.

Tree Trimmer · Sep 4, 2011

can someone show the math involved for a couple things.

in taking and converting lbs/min to cfm

in figuring out how much lbs/min the exhaust will flow at various rpm's

and how to modify that formula to account for different variables. boost, injectors, and the many other things involved with ending up at X lbs/min.

i can read a turbine/compressor map, but without being able to figure out what my motor does lbs/min wise, the maps are useless.

jkidd_39 · Sep 4, 2011

psduser1 said:
Tycorr is correct- by the time the exhaust gas hits the wheel on a standard 1.0 housed 38r, the scrolls are no longer divided. That's why there is one 18.8 mm wastegate, which is woefully inadequate! If you gate before that you'll have a pressure difference between the uppipes, but not at the wheel.
I can't say for a 1.15 housing, cause I don't have one, but Id speculate that its similar. Please correct me if I'm wrong.
That design would make a wastegate most effective when plumbed into a common space, per Charles, rpminc, etc. Less piping, more accessible, so on.

Closer to OP train of thought, if your primary turbo starts the boost, and guys with bigger housings mention slightly increased lag in a compound setup, would a tighter housing, aka 1.0, or even .84 housing minimize that. After all, your looking at a bigger turbo (atomospheric) to handle the top end. Properly gated, of course.
Btw, execellent thread. Keeping the brain cells moving!:thumbsup:

You can go tighter on the housing but you need to look at your map and make sure you aren't going to choke out the turbo. If the housing is too small you also run the chance of making it too tight.. the turbo will spool super fast but be hard to control. And cause some wicked backpressure.

Tree Trimmer said:
can someone show the math involved for a couple things.

in taking and converting lbs/min to cfm

in figuring out how much lbs/min the exhaust will flow at various rpm's

and how to modify that formula to account for different variables. boost, injectors, and the many other things involved with ending up at X lbs/min.

i can read a turbine/compressor map, but without being able to figure out what my motor does lbs/min wise, the maps are useless.

http://www.turbobygarrett.com/turbobygarrett/tech_center/diesel_tech.html

from what I am seeing in the twins game.. everyone wants to go larger than a cummins twins kit b/c of the displacement advantage. However the cummins has a better head design in terms of air-in vs. air-out. I would look into a smaller set up. Something along the lines of a 62/68 secondary over a 80 or 82/92 or 96.

There are others on her that have more experience with this subject than me.. but for instance.. Brian Jellich is running a 66 over a 103-ish primary..

V-Ref · Sep 4, 2011

Tree Trimmer said:
can someone show the math involved for a couple things.

I'll try! I like references for stuff....Hope this helps.

Tree Trimmer said:
in taking and converting lbs/min to cfm

Reference-Garrett Turbotech103
"Many people use Volumetric Flow Rate (expressed in cubic feet per minute, CFM or ft3/min) instead of mass flow rate. Volumetric flow rate can be converted to mass flow by multiplying by the air density. Air density at sea level is 0.076lb/ft3"

Since you want to convert the other way, just inverse the equation-

Ex1: 95 lb/min / .076= 1250 cfm

Ex2: 1250 cfm x .076 = 95 lb/min

Tree Trimmer said:
in figuring out how much lbs/min the exhaust will flow at various rpm's

Reference-Donaldson Filter page 7

(Exhaust Temp. (°F) + 460 / 540 ) x Intake Airflow(CFM) = Exhaust Flow

Tree Trimmer said:
and how to modify that formula to account for different variables. boost, injectors, and the many other things involved with ending up at X lbs/min.

Can't help here. I'd be pretty critical of the credentials of somebody that says they were to ensure you weren't getting fact not fiction....as you're asking some deep PhD level stuff above...

There will be a small addition to the exhaust mass that isn't accounted for above because of the addition of fuel. The link below is speaking to gassers.

http://www.eng-tips.com/viewthread.cfm?qid=104735

If that chit right there don't make your brain hurt...well...umm...:wtf:

Tree Trimmer said:
i can read a turbine/compressor map, but without being able to figure out what my motor does lbs/min wise, the maps are useless.

You'd need to know turbo RPM to accurately plot the performance of a compressor wheel.

Besides Charles/Gearhead/Tarm and other smart folks posts on some the of threads here and elsewhere, this link below is one of the best references I've ran across in learning how to read turbine maps.

http://www.dieseltruckresource.com/dev/do-turbine-maps-tell-us-turbo-t168543.html

I'd PDF these links...as I've already lost a couple good links due to forums going Tango Uniform.

I've got a couple book on turbocharging/supercharging too....but nobody reads those anymore :lookaround:

juniort444e · Sep 4, 2011

I didnt even read that v ref. I went crossed eyed and quit.

Some good info in that tho. I love math and will try to figure some numbers out for my setup.

juniort444e · Sep 5, 2011

Tarm im still having trouble finding the 4288 you were talking about.

But here are the two im thinking will work good together and that im willing to try. If someone thinks other wise please post why and what you would change. Thank you.

Primary is a Gt4094R w/ a 1.06 or 1.19 housing. And the atmosphere would be a gt5533 with the 91.2mm inducer and a 1.00 housing.

After looking at my engine bay and trying to imagine where i will put these i think i found a good solution that others have already succeeded at. Ill move the passenger side battery and stick it in there. But until i get the turbos and time and money i cant do much now.