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Discussion Starter #1
The sig pretty much sums it up to date.
Planning ahead, adding a second turbo would make the most sense, which one?
What else?
Do I need 60lb springs? Should I pull the head and ring it, swap to better head bolts?
Got another 12v in case.
 

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You don’t NEED to ring it, or stud it for 500. Plenty of people have gotten by on a retorque of the head bolts. That being said, I’m o-ringed and studded lol. But my end game is shy of 700. 60lb springs are a must though.


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Not sure if the 60# springs are a must. If you rev the crap out of your motor or have very high boost, then it is a must. I can get 40 lbs of boost, but it is not enough to open the intake valve befor the cam tells it to open. I don't know what point that happens though.
 

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It looks like 31 lbs of boost can blow open an intake valve on a 12v with 60 lbs springs (assuming no pressure in the cylinder). My p24v has smaller valves, so needs smaller springs to hold back the same pressure.
 

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That's a sweet looking setup. Someday I'll go there.
 

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The Uppity 12v Admin
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I would argue 60lb springs are stupid not to do for what they cost as far as protecting your engine up to 3800 rpm. ctmaybury, double-check your math. "60lb" springs have about 150 lbs on the seat in real life. A stock-size 12v intake valve has about 1.81 square inches of effective area on the back side. Roughly 82 psi to cancel out the spring. Stock-size exhaust valves have about 1.57 square inches of effective area on the back side, or 96 psi to cancel out the spring.

There really isn't anything to be concerned with as far as valves "blowing open."

During the exhaust stroke where the intake valve is most vulnerable, cylinder pressure is always going to be higher than boost pressure. Best (unrealistic) case scenario, it will drop completely to equilibrium with drive pressure, which will be higher than boost. Assume 1.2:1 for a rough conservative guess. If you're running 75 psi boost and 90 psi of drive pressure, there is still 15 psi of cylinder pressure exerting a closing force on the intake valve face, which is substantially larger (33%) than the effective area on the back side of the valve. That 90 psi in the cylinder vs 75 psi behind the valve results in a closing force of 215 lbs vs an opening force of 135 lbs from gas pressure on each side of the valve, or a net closure force of 80 lbs. In all reality, it is more accurate to say cylinder pressure closing the intake valve is thousands and then hundreds of psi on a decreasing curve until the end of the exhaust stroke.

During the intake stroke where the exhaust valve is most vulnerable, cylinder pressure is never going to be zero. There is some valve crossover and the flow of (pressurized) charge air into the cylinder begins before the exhaust valve has fully closed. The exhaust valve would start fluttering on the seat when drive pressure exceeded boost pressure by enough to cancel out the spring. Now, there is again a surface area bias which works in the favor of valve closure. On the exhaust valve, the surface area bias results in 35% more area on the valve face than on the back side. If you're maintaining the 1.5:1 ratio between drive pressure and boost the internet says you should, you'd have to be pushing a preposterous 485 psi of boost and 725 psi of drive pressure to reach a force equilibrium with the valve spring. 485 psi boost results in 1162 lbs of closure force on the valve face, and 725 psi of drive pressure results in 1312 lbs of opening force on the back side of the valve, or a net opening force of 150 lbs, which would effectively cancel out the spring. I don't know of any turbodiesel in history that's ran anywhere close to these levels of boost and drive pressure. Now, the pressure in the cylinder will not be 100% of boost as the engine is not 100% volumetrically efficient, but even if I were to drop the level of pressure that actually makes it into the cylinder to reflect a reasonable 80% VE, it would still take 285 psi of drive pressure to reach that equilibrium and cancel out the spring. Maintaining a healthy 1.5:1 ratio, this would mean a still outlandish 190 psi boost.

@OP, you don't need a manifold. They get flipped over. I would stud it. Skip the o-rings for now, but do them if you ever have the head off. 5x14s are a good injector for the K27/369 setup. I would advise upgraded locks and retainers with the 60lb springs as well. Stock ones have a tendency to pull through and drop valves over time.
 

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Discussion Starter #8
Yes, What We Are Looking For...

I would argue 60lb springs are stupid not to do for what they cost as far as protecting your engine up to 3800 rpm.
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@OP, you don't need a manifold. They get flipped over. I would stud it. Skip the o-rings for now, but do them if you ever have the head off. 5x14s are a good injector for the K27/369 setup. I would advise upgraded locks and retainers with the 60lb springs as well. Stock ones have a tendency to pull through and drop valves over time.
Studs, you mean head bolts?
Would the motor run lean with 5x11's? Or just not enough fuel to reach full potential?
Need to figure out the oil usage, could it be because it is a huffing and a puffing a bit under full pedal?
 

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A 60 lb spring is more like 150 lbs of seat pressure. Thats good to know. It seemed way to close to the blow open point. K27/369 looks like a very fun setup. Wish I read up on he k27 before getting the super b. Looks like the smaller tubine would contribute nicely to quick spool.
 

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The Uppity 12v Admin
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Studs, you mean head bolts?
Would the motor run lean with 5x11's? Or just not enough fuel to reach full potential?
Need to figure out the oil usage, could it be because it is a huffing and a puffing a bit under full pedal?
I mean studs unless you have the ability to make the custom washers required for the socket-head bolts. They all need a chamfer on the ID and the ones that go between the valve covers need to be turned down so as not to cut the gaskets. Studs will help hold the gasket better than the socket caps, depends on how much of a gamble you want to take with blowing the gasket.

Diesels don't have the same lean/rich sensitivity that gas engines do. Gasoline, spends all it's time in normal operation between roughly 11.5 and 18:1. Leaner than 18:1, you start blowing holes in pistons and experience sporadic combustion. Richer than 11.5:1, and you start getting black smoke and retarded combustion. A clean-running diesel is always running lean. Off hand, I'm not sure what your "just driving around" AFR would be, probably between 30:1 and 50:1 I would guess. Stoich for a diesel is ~14.6:1, but visible emissions begin around 19:1. Basically, you will start hazing before you reach stoich. Diesel will make the best power between 14:1 and 10:1, but going richer than that will start to retard combustion. I have an AFR meter that I'm going to integrate into the datalogging setup I'll be running when my truck is back together.

A 5x11 will not give you any driveability issues, you'll just be limited to essentially the same horsepower a K27 can support all on it's lonesome. The 5x11s may not fuel hard enough to spool the 369. I'd argue there's almost no point installing the 369 with those injectors.

I'm not sure what your oil usage is about, I would check the obvious sources one by one. It would be a good idea to replace the valve stem seals when you do the valve springs. Mine were done when I tore down at 334k.

A 60 lb spring is more like 150 lbs of seat pressure. Thats good to know. It seemed way to close to the blow open point. K27/369 looks like a very fun setup. Wish I read up on he k27 before getting the super b. Looks like the smaller tubine would contribute nicely to quick spool.
"60lb" springs are a factory part for a 370 Marine engine. They got the name they have because one of the exhaust brake manufacturers started selling them as an upgrade, advertised as allowing an increase to 60psi of backpressure from the brake, where the stock springs could only handle about 30.

I ran a 57/65/.8 S300G on mine for a while before I took it apart last fall. This is what the Super B is based on, it was hands down the worst turbo I've ever had on my truck.
 

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Time to put anothe turbo on the shelf.

I'd like to know about your data logger. I was going to design one for my truck to aid in dialing the afc, timing and comparing ic vs water to air cooler. Iat, egt, throttle position and boost pressure data points on .5 second intervals during a wot run might be very useful.
 

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Before getting the super b, someone on the 24v section running it posted some nice dyno numbers. Greater than 400 hp and greater than 1000 ft lbs torque. The 2.5 to 1 ratio seemed impressive to me. I think his screen name is ganzey or something close to that. Apologies to ganzey if I got his name wrong. Not a lot of dyno numbers come in with that high a ratio.
 

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Ducati M.
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Volumetric efficiency is over 100% on our engines because of forced induction. Only naturally aspirated engines fall below 100% (though from what I hear the Ducati 1199 engines actually can run 100% ve).
 

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The Uppity 12v Admin
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No, that's not how VE works. The engine still has a VE band covering 75-85% VE (or whatever) across the RPM range. The difference between NA and forced induction is that the mass of charge air may be many times that of ambient. VE is still applied, but it's applied factoring in the higher intake air density.

To be fair, it is somewhat common for people to talk about boosted engines as having in excess of 100% VE, but that isn't the proper way to model the engine's operation. This is another example of bad tech that seems to be endemic to the forum experience in general.

Air density and volume are different things. A cubic foot is a cubic foot, regardless of the absolute pressure or density of the gas within it.
 

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Dauntless is right about the ve numbers. The forced induction increases the airflow to be sure but the ve number has to do with the measured volume of air the engine flowes vs the displacement (tdc to bdc) in a perfect world. Sorry 12v guys, but 4v heads out flow 2v heads, but from what I understand, a ported polished 12v head can outflow a 24v head. Ve is one area I want to address with my motor. Equal length tube headers with the primary tube lenghth tuned for cylinder scavenging at 1900 rpm (freeway speed) will increase my ve. Some head work will also add to ve. Highly tuned f1 race engines can approach 115% ve.
 

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Ducati M.
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I never learned it on the forum. It was how it was explained to me when I went to school for my chosen career path. Seems like bs otherwise, and everything else I’m finding only corroborates my viewpoint. If you can prove/show me valid data on it fine, I have no trouble amending my viewpoint, but the current logic doesn’t track with me.
 

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After some Gargling, it appears there is no shortage of resources I otherwise would have considered credible making statements about forced induction increasing VE over 100%. It would seem that in the context of an engine, they are advocating incorporating the increased density of the charge air into the calculation but then fixing the volume's comparison baseline at "ambient pressure." I find that odd because in liquid handling applications, it's simply actual moved volume divided by measured displacement volume of the pump itself. The rest of the system is ignored. I am compelled to pose the question (perhaps rhetorically), why is this double standard accepted?

I suppose with the complete engine, including turbochargers, as the system, it would not be inaccurate to say VE would be in excess of 100%, however when the scope is dialed back to the longblock only, or perhapes even the cylinder itself (piston, walls, combustion chamber, valves and valve timing), as would be the case if we were talking about something like a hydraulic pump, there will still generally be filling, emptying, and combustion losses (we'll skip over inertial supercharging as it's not relevant to this particular engine platform) and the cylinder system itself would still have a sub-100 volumetric efficiency as a result.

Hmm. I'm not sure which scope is more cromulent. I suppose it depends on what you're trying to evaluate.

As far as understanding where I'm coming from, roll this over in your head. If you think about it, it makes sense:

Now, the pressure in the cylinder will not be 100% of boost as the engine is not 100% volumetrically efficient...
 

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Ducati M.
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Valid points knowing where you’re coming from, and I agree. Biggest difference between fluid handling, and gasses is compressibility. I can’t remember the math, but due to how minute it is many consider liquids to effectively be incompressible, whereas gasses can be compressed substantially. In terms of volume hundreds of litres of air can be forced into a few litre container given adequate pressure (though I feel like the limit is when the gas achieves enough pressure to change state (the whole 1psi of pressure increases boiling point roughly 3* thing)), hence it’s not so much a double standard as a different set of rules for a mediums state.
 

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Volumetric Efficiency (and the REAL factor: MASS AIRFLOW), by EPI Inc.

This is a good explanation. On this site is where I learned about cylinder scavenging from the reflected pressure wave.

Imo the ve of our Cummins motors are hurt by the torturous path the intake air takes to get to the cylinder. All that plumbing plus the ic. Thats a lot of friction making the ve poor. Have you looked at the 89 without an inter cooler? We need to cool the charge air so picture a water to air cooler sitting on top of the valve cover and a straight shot to the intake from the turbo. I think boost will build much faster without all that 3 inch plumbing and ve will be increased dramatically. That's the direction I want to go.
 

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The Uppity 12v Admin
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Valid points knowing where you’re coming from, and I agree. Biggest difference between fluid handling, and gasses is compressibility. I can’t remember the math, but due to how minute it is many consider liquids to effectively be incompressible, whereas gasses can be compressed substantially. In terms of volume hundreds of litres of air can be forced into a few litre container given adequate pressure (though I feel like the limit is when the gas achieves enough pressure to change state (the whole 1psi of pressure increases boiling point roughly 3* thing)), hence it’s not so much a double standard as a different set of rules for a mediums state.

Bulk Modulus.


Liquids vs gasses is obviously a big difference, but the component vs system thing is what I'm getting at.



Sticking with hydraulics, because it's easy, both hydraulic systems and engines are fairly modular. If a hydraulic system (say a simple pump and motor setup to drive a load) was assembled, one could stick two hydraulic pumps in series which would increase the VE of each, but nobody would ever make a selling point out of the "increased VE" of that whole system.


I suppose if there was a better way to do it, someone else would have thought of it 50 years ago.
 
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