I have built a few triple set ups now and will be doing another in January. The sets I have done thus far have been "deadheaded" like you have seen. The reason for this is that the turbo's have all been large and real-estate under the hood was not large enough to accommodate a Y in the hot pipe. On the triple set I will be building I will be utilizing a Y in the hotpipe as the turbos are smaller and there is space for it.

I have had no issues with the dead head hotpipe and have made large power doing it, I do agree that a Y is a best case scenario but at the end of the day sometimes you just have to make it work. Research project leftovers Frankenstein on this forum and you will see the build of one of my sets.

As far as tuning I have not had any issues. They were all tuned the same as a normal 2 stage compound set. I could see issues if you just stuck on some turbos with no consideration of airflow requirements on the particular vehicle. As long as they are sized correctly it should be very easy to tune.

If you want any help calculating your airflow needs let me know what you are trying to do as far as desired rpm and peak power and I can help you size turbos for your application.

 

Thank you for your insight. Good to hear that they are the same as regular compounds to tune. I have inquired at local dyno events and was told that triples aren't for the faint of heart and difficult to tune.
First off let me say project Frankenstein is impressive! I had a grin a mile wide on my face as i read about the dual air to water intercoolers! It has been part of my plan also to use two intercoolers one air to water between stages and one air to air before the engine. Wow, stunning to see the effort put into your truck.

Yes you are right i do have my heart set on a line of turbos (Borg Warner EFR) and i hope that they will size correctly to match. If that isn't the case i will find what works correctly. I have been deep in turbo math research trying to understand how to properly size compounds.

2nd off i want to say i have decided to use triple turbos for the following reasons:

1. I firmly believe that if you require enough air to need compound turbos, no matter how small the gain it's going to be, they will produce better EGT control, Drive pressure control and better boost response than the standard two turbos in compound arrangement.

2. Basically i am trying to perfect my cummins. I had installed MHP oversized stainless steel valves with port work. The original idea was to reduce required boost and drive pressure to increase reliability (less stress on head gasket) and reduce drive pressure. The new head flow tested equal to a stock 24valve in flow this lowered my peak boost from 67 psi gauge to under 50 psi. Predictably power went up in the top rpm as the swirl ramp was partly removed. Light idle and lower rpm haze showed up.

(All above mentioned and currently running) info is using my MODIFIED(No silicone boot between stages) DPS D-TECH 62 over an HT3B. Since then i have found the only thing i could do to my current setup was to change the turbine housing on my HT3B turbo.

Original housing was i think 32cm turbine housing, i changed to 26cm and finally a 23cm housing. i watched as my Egt's decreased with each smaller turbine housing and drive pressure and low pressure turbo spool up increased. The truck need more air.

Currently my Ht3b has a cermanic coated 23cm housing under the stock D-Tech 62. The compound set has producd 57psi total 21 psi from the primary and with all summer long of driving/hotroding the max EGT ever was 1295 degrees. Drive pressure peaks at about 69psi. I calculate and the 2nd stage is over driven and making about 14psi.

Yes the truck does well, i think the turbos i am running are now too big because of the better flowing head. I can certainly tell the engine feels choked out up top with the 23 cm housing. With the 26 the truck cleaned up all unburnt fuel at full rip and now with the 23 cm housing it again black smokes. I need more mid range spool up to better tow with and i believe that most people who have experienced these issues with similar head port work simply had the wrong combination of parts.

3. I want increased reliability through lower Driver pressure and lower EGT's

4. I want to have fun at dyno events, throw the truck to the rollers spank it good and still Daily drive it and tow with it. (Race truck/play truck)

I think triples will be a good compromise for me and might improve my low end haze and spool up with the benefit of improve EGT and drive pressure. I have seen that with housing changes the low pressure turbo represents a restriction to the engine until it starts to spool (26cm housing was most obvious)
With the 23cm back pressure is higher and harder to notice when this transition occurs.

So... i think both turbos are too large and significant improvements could be made especially to the low pressure turbo spool up. I have a cylinder head that mainly improves the top rpm range and some to the mid rmp range. I need everything i can to improve the low and mid rpm power spool up with the hopes of keeping the all out performance up top.

It's not all bad, the plus side is that the truck requires less throttle than ever for daily driving and i can't even hit 1300 degrees for a 525 rwhp truck though this is the HP before the head work. It defiantly has more balls up top than ever before. My plan is different from most. I want all the above plus the cleanest and most efficient truck using only the fueling i already have. No more fuel no less.

More later on turbo air requirements i need sleepy.....though this turbo obsession has given me many sleepless nights! lol:drool2:

Thanks again everyone, let me know what you think so far.

 

Where did you hear trips are hard to tune, and how was that meant? They aren't any different than a typical compound setup, they just split the primary stage across two turbos.

The *** trips don't just "deadend", they have an overall wastegate at the end of the log. I would assume that and packaging constraints is why they are the way they are. They work, they work well, I'm not going to complain.

My only issues from a "tuning" stand point has been weeding out little issues, like exhaust and oil leaks, coolant leaks, and when I get the head back on I'll be tuning the waste gates because they've never worked properly on my truck. They did on at least two of the three previous trucks that ran these...I don't know how they worked on the 3rd truck. As far as the ECM tuning, it was pretty much spot-on from the get-go. I can't take credit for that.

I would venture to guess no one is open with turbo specs and such because anyone can slap three turbos under the hood, but having the three turbos work well in conjunction with each other is an entirely different thing. Yes, I know what mine measure, no I won't tell you


Can I venture down a side track and ask why you're set on running trips?

 

I have long wondered why any one would discourage triples. Makes sense that they tune the same as regular compounds, though when local diesel shops tell you they aren't for the faint of heart ant they are difficult to tune your imagination can go wild.

 

Well MoparProud i finally read your 44 page project blue balls build...HOLY CRAP coolant/exhaust leak repairs. lol. These projects can sure take time. While working out the kinks life still has to go on and can really slow the projects down.

I had alot of issues working out the kinks after my new engine. Many people thought i would give it up and couldn't understand why i would not.

Looking forward to see you get them running proper good luck man!

 

Thanks man. Once I dug in there (removed the entire turbo setup) I think I may have found at least a partial cause for some of my issues. One of the coolant lines I routed in a way that looked fine upon assembly, but seems after being on the road it kind of folded over on itself and while not completely blocking off flow, certainly had to impede it to possibly the point of being enough of a blockage that the coolant didn't have anywhere to go but out some random place, like the fitting I found that's likely been leaking.

So I finish up this headgasket and reroute that coolant line and.....cross my fingers, no more coolant leaks.

Exhaust leaks, I don't know what to do there. I keep having nuts fall off the manifold studs, and actually at one point lost two or three of the four mounting a turbo. Part of me wants to loctite the nuts on, however the way this manifold is, it would be nearly impossible to pull the manifold without really fighting it (studs can't come out all the way with a nut on the end, especially on the wastegate ports.


It's been a headache at times, but every time I drive it it's awesome. And still fun to watch people try to wrap their head around three turbos Short of a full ballbearing compound setup, I'd put triples against any combo out there really.

 

To me the real benefit of triples is cost. How much money does a turbo that can move 200lbs of air cost? On Frankenstein the s475's are around 725 each. That is over 200 lbs of air for $1450. that is probably 1/3 the cost of a turbo capable of doing that much mass on its own due to economy of scale. Not a huge demand for 200 lb/min turbos. If you have to pay someone to do the fab work you may end up with the same expense because the fab is so much more time consuming. If I was building Frankenstein right now I would probably use the new s369 instead of the 475 for packaging reasons. I may do that anyways because I think the new sxe369 is so sweet!

As has been mentioned many times real estate under the hood is the real problem. A remote mount oil filter will be your friend.

 

Thanks Power Driven Diesel.

I agree the amount of air triples can supply make it all worth it. I am wanting the best setup i can have so for me triples are it. I can, will do all the fab work myself and i am ready for the challenge. Cost is not a problem. I want to use the Borg Warner EFR turbo line if possible. Basically i want to use all full ball bearing turbos.

I will take you up on your offer about the air flow calculations.:thumbsup:

My truck previously dynoed at 525rwhp and was slightly over fueled so i would assume i have enough fuel for say 530rwhp.ish I want to add no extra fuel to this triple turbo setup i am happy with my HP and the trade offs they have caused.

I am looking to run a max of 2800-3000 RPM.
Given that my new cylinder head is better flowing ( oversize MHP engine valves, flow tested to equal 24 valve stock ) i assume my VE= .90%?

I am figuring 15% loss to the wheels with a manual transmission.

Not sure what to use for BSFC or Air to fuel ratio
I took my best guess at it from the research i have done Take a look at the attaches calculations. It would be a real killer to type all of it. lol:S:

I appreciate all you help!

 

My $ 0.02:
Your manifold intake temp will be much much higher, you're compressing air twice. Also, I think you might be over thinking it. Assuming your 85lbs is right you just need your two primaries to have a combined flow at that. Well maybe a touch more for inefficiencies. Trying to find your overall boost will give you a number to shoot for while tuning, but if your above that well that's great too.

 

Hey thanks for the input. You're probably right about the intake temps. I have almost completed my calculations for the actual air flow of my compounds and boost pressures. I could stay up late and finish however i need sleepy!

I will say that compounds are supposed to be matched in a 1:1 boost and flow ratio. Meaning they should be splitting the flow and boost half and half. The big primary or atmospheric turbo is producing it's half of the air flow and boost yet needs to be capable of total flow throughput. Much the same way you match a single turbo to an engine's base air flow throughput.

If someone were inclined, maybe you could run two 40 something lbs per minute air flow turbos in parallel?

I agree, excess boost pressure wouldn't be a problem with me!! This is another reason i want triple turbos.

Some discourage primary turbos from operating above this matched 1:1 ratio. Not sure i see the real harm in it... well mine are operating this way anyways. Maybe if it were extreme it could cause the stage 2 turbo to surge?

I think that a properly designed street turbo system should be operating with some % of waste gating going on.

 

I looked over you notes and they seem great! I get the same airflow using a .38 bsfc and a 22 AFR to be 85lbs/min. There are a few things I didn't see and maybe they were there and I just couldn't read them. But what are you calculating your intercooler efficiency to be and I also saw the over all boost but I didn't see the requirements for each individual stage and the PR's you are planning to run on each stage. I ran some calculations based on what I saw on your notes and here is a rundown.

Lets assume that you have a cooler that is 75% efficient. The efficiency here is defined as though 100% efficient would cool the charge to equal the temp of the cooling medium, in this case ambeint air of 72º.

Further lets pick some easily attainable PR's. I hereby choose 2.5 for the first stage of compression and 1.9 for the second stage. yeilding 55.27 psig at sea level.

Ok so now lets start to determine the requirements of this design.

at 3000 rpm with a 90% VE your engine will consume a whopping 281 cfm. Big power right!?

The weight of every single Cubic foot at sea level at 72º is .075 lbs. and NA this engine consumes about 21.5 lbs/min at sea level at 72º.

If we force feed it with the 1.9 PR this engine is now boosted to 13.2 psig and will still take in a whopping 281 cfm. But now each cubic foot weighs .111 lbs and we are now flowing 31 lbs/min through the engine. It is true that the temperature is now 220º F but the pressure overcompensates and each CF is more dense thereby more powerarty018:

Now in order for the turbo to supply 281 cfm at a weight of .111 per CF it needs to take in 418 CFM of the air that weighs .075 lbs to do it. (These calculations assume a 72% compressor efficiency for those who care)

So quick recap the engine flows 281 cfm and the turbo flows 418 cfm to meet the demand of 281 cfm at a PR of 1.9.

Now we are looking for 55 psig not 13.2 so as per the design specifications of blue beastie we are going to compound this guy. We have already decided to run this stage of compression at a 2.5 PR or 22psig so we need to supply 418 cfm at 22psig which will require 741 cfm of air at atmospheric pressure. 741 cfm is at .075 lbs/CF give us 56 lbs per min of total system flow. Which is about 30 short of our goal.

The reason we are so short is the lack of intercooling thus far in our calculations. In theory we have 281 cfm going through the engine, each cubic foot now weighs .197 lbs. and is at a temperature of about 498.43º give or take, just ball parking it here.

But we decided that we have an intercooler that is 75% efficient and that will make a massive difference. We have air that weighs .197 lbs/CF before it goes into the intercooler at 500º. after it is cooled it will leave the intercooler at about 180º and if there is no pressure drop (impossible) it will now weigh .296 lbs. per cubic foot.

Well crap that changes everything, the small turbo now has a double whammy against it. It is taking in hot air from the other turbo and it is then cooled afterwards. So the turbo that needed to flow 418 cfm now must flow 500 cfm or around 38 lbs/min. and that means that the atmosphere turbo is now having to supply 500 cfm with 22psig not 418 so it now must flow 1112 cfm to do it. And what does 1112 cfm at our ambient conditions of .075 lbs./CF equate to? 1112X.075=83.4 lbs per min.

What the crap I thought we were after 85lbs/min?!

The conditions provided call for 72º temps. The maps for compressors are done at standard conditions so in order for a turbo to flow 83.4 lbs per min at 72º it will have to show that it is able to move 85 lbs of air on the map.

If we want to flow 85 lbs of air through this system with these conditions I would suggest a total boost of 57 psi to do that.

Some areas where you can see some differences in my calculations is compressor efficiency. I didn't see that accounted for in your calculations and that is why I had to have higher boost numbers to achieve 85 lbs/min.

Also I hope you all noticed the huge gain in a good intercooler. By adding a second turbo to the first we picked up 25 lbs/min through the system. By intercooling we added 30 more which was more than the second turbo did. This is why you see the extreme effort I put into Frankenstein in regards to intercooling. But you must account for it because as you saw it changes the requirements of each individual stage.

And finally I am sure the author knows that triples are way over kill for the his flow and power goals. And while I would not personally recommend triples for these goals I still think it will be cool and look forward to seeing how this thing turns out!

 

Power driven diesel Thank you!!! Good to see your take on this. I am happy to see some familiar numbers.

I thought i could check myself and try to figure out what my current compound are producing. Doing so will help me gain confidence to properly size triples. My theory was both were too big just slightly, especially the D-Tech turbo unfortunately i couldn't get a smaller turbine housing like i did for the HT3B to see the effects it had. I think it would probably just push it closer to surge anyway.

Please let me know what you think about my calculations. I will post plotted compressor maps shortly too.

The Known Factors –
Turbos are Diesel Power Source D-Tech 62 (Known as stage 2, secondary, high pressure turbo or even manifold turbo) over a Borg Warner HT3B (Known as Stage 1, Primary, Atmospheric, or low pressure turbo)
My compound turbo produced total boost of 57 psig = 4.87 pressure ratio
Stage 1 atmospheric/low pressure turbo has produced 21 psig max = 2.42 PR
To figure out the boost and pressure ratio of second stage turbo, I have the total
PR of 4.87 or 57pisg
Stage 1 compressor is 21 psig or 2.42
Using 4.87 PR/2.42 PR= 2.012 PR = 2.0 PR 2nd STG turbo
So boost pressure would be 2.0 X 14.7 -14.7 = STG 2 turbo 14.7 psig
Turbo Boost Ratios
1st stage low pressure turbo 21 psig
Stage 2 turbo 14.7 psig
21/14.7 = 1.42:1 ratio low pressure turbo is overdriving second stage turbo
EGT’s max 1297
Max RPM 3000
Drive Pressure
Max total boost 57 psig Max drive psig 69 69/57 = 1.21:1 ratio for drive pressure.
To improve engine breathability low pressure turbo should now be waste gated for increased top rpm HP to maintain 1:1 drive pressure ratio.
*New triple turbo might also improve idle haze as drive pressure is high at idle now b/c of the smallest available low pressure turbo (HT3B) turbine housing is now installed, 0.6 psig at idle. Drive pressure tends to be higher until low pressure turbo spools or steady heavy load is applied. Boost is 0.3 psig at idle. When under steady load drive ratio is just above or at 1:1. Drive psi at idle when cold engine is 1psig (thick cold oil)


Compressor Flow Calculations
For most outlet temperature and density ratio calculations, I can calculate separately if I feel crazy enough to do so lol. I am using density ratio table and compressor discharge temperature tables for the following formulas. The known information is:
Calculate Engine Air Flow requirements
Air Flow in CFM = CID X RPM X .5 X VE / 1728
RPM = 3000 CID = 361 VE = 90%
361 X 3000 X .5 X .90/1728 = 282 CFM air flow required before turbo charging
282 X .076 to convert to pounds per minute of air = 21.43 lbs of air
Calculating Air Flow Requirements of Stage 2 Compressor First
Information 21 lbs of air X stage 2 compressor density ratio. Stage 2 compressor has a 2.0 PR
Assumed 72% compressor efficiency
Using the table = 1.5 density ratio with 90-degree ambient inlet air outlet temp is 250 F
21 lbs of air X density ratio of 1.5 = 32.1 lbs per minute of air @ 2.0 PR is what the stage 2 compressor must flow
Confirmed D tech 62 turbo is operating at 74% for required output.
Stage 1 turbo Assume 75% efficiency at 2.42 PR ambient air 90 degrees F outlet air temp is 290 F
Density ratio is 1.7 X stage 2 air flow requirement of 32.1 lbs air = 1.7 X 32.1 = 57.7 lbs per min required air flow for stage 1 low pressure turbo.
Confirmed Borg Warner HT3B turbo is operating at 74% efficiency with 54.7 lbs per minute of air @ 2.42 pressure ratio.

Correcting stage 2 turbo density ration calculation
Because inlet air temperature is no longer close to 90 degrees Fahrenheit. It is now the outlet temperature of the stage 1 turbo which is 290 degrees.
Forced to calculate long head because no density table exists with ambient temperature as high as 290 degrees.
DR = (T1c/(T1c+(((T1c x PR.283) – (T1c)/CE)) x PR
T1c = original ambient inlet temperature in degrees Raken. (290 degrees F stage 1 outlet temp + 460 = 750 degrees R)
PR = 2.0 CE = Compressor efficiency – checked compressor map, found for 32.1 pounds of air at a 2.0 PR the compressor was actually more efficient than originally assumed. New compressor efficiency is 74%.
(750/(750+(((750 x 2.0 .283) – 750) / .74%))) x 2
(750/(750+(((750 x 1.216) -750)/.74))) x 2
(750/(750 + ((912-750)/.74))) x 2
(750/750+(162/.74))) x 2
(750/(750+218.91)) x 2
(750/968.918) x 2
.774 x 2 = 1.54 DR corrected for STG2 turbo
*Not much changed for the Density ratio, though a tiny chart is hard to eyeball and I think I did just round down so not too surprised.

Corrected Compound turbo air flow calculations
Base engine air flow requirement was: 21.43 lbs air per minute
21.43 x corrected DR STG2 turbo= 21.43 x 1.54=33Lbs of air a minute, required air from STG 2
33lbs air* STG 1 turbo DR= Stg 1 air flow
33 x 1.7= 56.1lbs of air per minute corrected air flow produced from STG 1 turbo.

Determine inter cooler inlet/outlet temp and density ratio
*Note: I have a Spearco intercooler rated at 1100 cfm and 1 psi pressure drop. Cannot find spec for efficiency, would have to contact factory.
I do have intercooler inlet and outlet temperature sensors installed on my truck. I can recall approximate temperatures of at max power testing of 290 degrees F at full throttle inlet and approximately 130 degrees F outlet.
Finding intercooler efficiency based on above information:
290-130=160 temperature drop on a 60 degree F day when testing occurred
TE= Thermal efficiency of intercooler – unknown
Tcharge= Intercooler inlet temp - 290 degrees F
Coolant = Outside ambient air temperature – 60 degrees F
TE= Tdrop/(Tcharge – coolant)
160/(290 -60)
160/230= .69 % intercooler efficiency
I will use 65% efficiency to error on the conservative side. Also the above tests were noted at 60 degrees F whereas everything calculated so far is based on 90 degree ambient air.

Calculate Intercooler Inlet Temperature
Hot air left STG 1 @ 290 degrees F and entered STG 2 inlet
Actual turbo temperature rise of STG 2
T2C = New compressor outlet temp degrees Rankin = unknown
T1C = Original inlet absolute degrees R = 460 + 290 = 750 R
PR = Pressure ratio = 2.0
CE = Compressor efficiency New corrected efficiency is 74%
T2C = T1C (((T1C X PR .283) – TC1)/CE)
750 +(((750 x 2 .283)-750)/.74)
750+(((75 x 1.216)-750/.74)
750+((912.541-750)/.74
750+((162.54/.74)
750+219.651
T2C=969.65 -460 =509 degree F air leaving stage 2 compressor headed for intercooler

Final Inter Cooler Calculations
From calculated above intercooler efficiency is 69% I will use 65% to error on the conservative side. 590 degerees F x .65 = 330.8 intercooler will remove from charge air temperature
509-331 = 178 degrees leaving intercooler into engine
IC = density change from temperature change through intercooler
T1 = original temperature degrees Rankin leaving compressor stage two 509+460=969 degrees R
T2= New intercooler temperature leaving intercooler degrees R 178+460=638 degrees R
IC = (T1/T2)-1
(969/638)-1=1.51 -1 =.51
Density increase of 1.51 = a 51% increase in air density
Total engine airflow is 56.1 x intercooler density ratio of 1.51 = 84.71 lbs/minute entering the engine or 84.71/.076 = 1114.06 cfm at 57 psi total boost

 

High pressure turbo compressor map D-TECH 62 and my HT3B low pressure turbo map.

 

Power driven diesel i wanted to calculate required total airflow and psig need to develop the HP i should currently have. Trying to be as realistic as possible i was over fueled at the last dyno so... it could be as high as 550wrhp i don't know. I just need to be realistically conservative. I only factored in pressure drop from air filter to any thing i could think of as being a important estimate for system restrictions.

Thought if i could run numbers to see what i need to have for flow and boost, i could better understand what i would want to tweak and how everything relates to system performance. Until now i had not put the whole picture together for a complete compound system.

Thank you i do realize triples are over kill. I am not interested in a minor improvement with a new set of compounds. I want the best possible tow and play truck. Everyone says you can't have your cake and eat it too, i am going to try!

 

blue beastie10,

Your stuff from above is a lot of work and confusing to get to the number I think you were trying to prove.

Easy things I can show you've found:
Manifold intake temp is 178 degrees
You make 57 psi total
Your engine uses 282 CFM @3000rpm

Assuming dry air and using an online air density calculator: air at 71.7 psi (57+14.7) and 178 degrees is .303 lbs/ft^3

This means your current set up produced 282*.303 = 85.5 lbs min of air

This means your primary produced/moved 85.5 lbs/min which is nearing its maximum at that pressure ratio.

This means your secondary also compressed or moved 85.5 lbs/min.

 

An interesting experiment once you decide on turbos. First mount the new secondary over your current primary. Do some testing. Then build your trips. It would give you a some-what apples to apples comparison between a single and parallel primaries.

 

Well I am going to start crunching numbers for my new triple turbo setup. This may take me some time, so please be patient.

If my previously figured numbers are correct, I will be looking to make 85 lbs/min total. Yes Power Driven Diesel was correct in pointing out that the intercooler in my setup is like literally adding another turbo's air flow to the system. Notice that I had only 56 lbs/min before the density increase from the intercooler.

My triple turbo setup will retain my spearco intercooler (1,100 CFM rating). I will add another air to water intercooler between stages. This will change the size requirement of the manifold turbo.

I am shooting for 85 lbs/min(or 1,114 CFM) total with total PR OF 5.35 (64 psig) or 2.6 PR for each stage.
That is 24 psig for stage 1 and 2

I am hoping to use 3 equal sized Borg Warner EFR turbos. Part # 6258

Yes the math is a lot of work, but several years ago I began contemplating 3 turbos, I realized that I needed to better understand the entire picture. The math has helped me with that.
For instance, I suspected that running lower boost was more efficient and I was very happy when I calculated the difference for density ratios when requiring more boost (less efficient engine with more pumping losses) it made it clear to me that more boost produced more heat and lowers density ratios. That is what we are most concerned with. How dense is the air actually getting into the engine?

More boost is not more power!! More boost = more heat requiring more pressure!

 

More boost is not more power!! More boost = more heat requiring more pressure!

Actually, providing you have enough fuel, more boost typically does yield more power. It has been shown in the past, that even taking something like an HX35 and pushing it way off it's map to like 45-50psi, will still create more power at higher boost. It will be hot, with greatly diminished efficiency, but it will be more hp. Well, at least until the turbo grenades.

Speaking of grenades....

You are aware of the reliability issues with running an EFR on a performance diesel, right???

 

Geez. See that's why I let others figure it out. Math sucks.

 

The numbers look good! Now your next step is to test how well the math translates into reality.

I often hear the phrase of how more boost = more heat not power. Others have said it but I would really like to hammer this point home. Once an engine is assembled the more boost you can efficiently run through it the more power it will make.

 

I guess the point i am thinking of is that more boost for a given setup is not necessarily the best yes it can be increased efficiently however most people including myself at one time, get caught up thinking about how high a boost number we can achieve and that this will make the most power.

One engine needs 70psi boost to make 500 HP and another may only need 50 psi to do the same.

Again i am the amateur here and still very much learning. I did realized that my math only worked forward i didn't work it from the engine backward to the stg1 turbo so my air flow is off.

The points on the compressor maps should probably move to the right towards choke. I think the HTB3 should be should have a total of 85lbs/min. air flow @ 2.42 PR.

Thoughts on this?

 

Please post results, they'd be the Bees Knees if they held together.

 

I know the first atmospheric turbo needs to be capable of flowing at 85 lbs per minute because of the entire system requirements including engine, inter cooler and first stage turbo. My question is, where on the compressor map, for the stage 1 turbo, should I be plotting? Is the stage 1 turbo required to flow 85 lbs per minute at a 2.42 pressure ratio? Or is it supposed to be flowing at 57 lbs per minute at the 2.42 ratio like previously calculated and just needs to be capable of flowing the 85? I guess I am just confused.

I guess I am also discovering that by porting the head and increasing engine efficiency, I have increased the flow requirements of the turbos and reduced the pressure requirements of the turbos. This is not what I had expected, but it's why I am trying to understand how to properly size the turbos.

 

You know your confused, that's good. If you want the stage one to be efficient and at PR of 2.42 it needs to flow 85lbs because all the air the engine needs must flow through that turbo. Since there is an air volume decrease with temperature while maintaining the same pressure, you need a turbo that flows more air. What's confusing is lbs/min and cfm. Most turbo maps are in lb/min and with compounds that doesn't translate perfectly. Power driven had a good example, look through it again, it will help you size your stage 2 turbo.

 

Hey Thanks austinbrose,

I did finally figure out my learning disability... it was way too many numbers and formulas! lol
Ok so now i get it! I did plot my points on the compressor maps for my current compound set incorrectly. STG2 turbo needs to flow base engine air requirements plus the intercooler's air flow needs. STG1 compressor must flow all of that plus the other half of the total air flow required to produce the desired HP.

 

I have calculated potential triple turbo combination.arty018: Requirements were considering that I was slightly over fueled at 525 rwhp. I have adjusted air flow requirements for a reasonable 15 hp gain of 540whp

So I am looking for 635 flywheel hp. I am trying to get the cleanest exhaust possible so I am hoping for 25:1 AFR. Though I am calculating a realistic 23.5:1 AFR.
I also adjusted the engine base airflow requirements to account for .020" over sized pistons. This brings the new engine air flow requirements to 21.85 lbs/min.

Using three Garrett GXT3582R turbos that have a 62 mm inducer with a 82 mm exducer.

I'm looking for 4.6 total pressure ratio with 2.3PR for each STG.

This setup will have two inter coolers, one is an air to water. Each will have an approximate efficiency of 69%.

Ambient air will be figured at 90 degrees F.

Adding it all up:
Engine requires 21.85 lbs/min x STG 2 inter cooler density of 1.28 = 27.96

STG 2 turbo density ratio x inter cooler air flow requirements of 27.96 lbs

27.96 x 1.69 = 47.2 lbs/min @ a 2.3 PR required AF for STG 2 compressor

STG 1 inter cooler= air flow STG 2 turbo AF x STG 1 cooler DR of 1.19 = 47.26 x 1.19 = 56.24 lbs/min then mutiply STG 1 turbo density ratio 1.7 x 56.24 = 95.6lbs/min is required flow from STG 1 turbos at @ PR of 2.3

Final outlet air temperature after leaving the last inter cooler in line is 172 degrees F.

I will attach compressor maps for the candidate turbo chargers.

Things I noticed during my calculations, the higher the pressure ratio, even with good compressor efficiency, meant higher discharge temperatures and higher density ratios. All of which pushed my total air flow too high.

Either from increased turbo density or more greater temp change through the inter coolers resulting in again way too much air flow. The higher the discharge temp going into the inter cooler, the greater the density increase was because there was more temperature change. It seemed tricky to find the right amount of boost to keep total air flow near my goal of 94 lbs/min.

Also for plotting the compressor map points I am simply dividing linearly back from my max output/RPM calculation.

I would like to know everyone's thought on this method?

I could run the numbers for different RPM points, however I would be guessing about engine VE at different RPMs, besides turbos respond to load and are too dynamic I think to better predict anything less than max output.
Though I might go mad from calculations! lol

 

Triples maped

 

Per the KISS method of sizing turbos....

You're looking for 635 HP. Diesels burn ~.0067 lbs/min/hp of fuel.
635 x .0067 x 23.5(A/F ratio) = ~100lbs per min. Add 15% due to temp rise = 115lbs/min

That's a lot of air for just 635 HP. You'd be much better off to lower your air/fuel requirement so that you can run smaller primaries that would spool quicker. Just dropping to 20.5:1 (which is still very clean), you'd get by with 100lbs min.

 

Humm.... Well i think you and I are on the same page Maybe u missed a key? I used:
BSFC.38 AFR 23.5:1 FWHP 635

The formula is: AF= HP X AFR X BSFC X (.38/60)

.38/60=.00633 then 635 x 23.5 x .00633= 94.45lbs/min is my airflow requirement.

Previously I had used a formula to calculate required manifold pressure, a good formula though I disregarded it. I don't believe they apply when compounding. As PowerDrivenDiesel mentioned my previous calculations were independent of compressor efficiency and total system efficiency.

Notice these turbos only needed 53psig to accomplish the total 96lbs of flow. On that note my calculations use actual temperature and include the effects through all inter coolers and compressors. so I shouldn't need to add any extra flow... I think.

I think boost and flow are obviously related and neither can be determined without picking a set of turbos and calculating out the efficiency they impart on the system.

Yes the 62's are large, but that is mostly because I have too many inter coolers LOL

 

Actually, I used a BSFC of .4. That's what I normally use it in calculating range in marine applications, it's easier calculating in my head with one decimal place, pretty close for most boats too. Diesel's BSFC is not a constant anyway, it can vary from low .3s to upper .4s depending on other factors, .4 is a nice round number in the middle. The formula doesn't care how many turbos you have.

62s because you have too many intercoolers, Hmmm?

When I was looking into maybe doing trips, I was planning around the GTX3582s as primaries, but that was for 1000 RWHP. I'm sure they'd work for you, they just won't be as much fun to drive as something better suited to making 600hp. But they would give you lotsa room to grow.