Calculating Compounds
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- Опубліковано 20 лип 2024
- In this video we go over the basics of turbo diesel compound turbo charging using science, math, paired with real world examples. How to actually calculate what is going on, and how to make adjustments to make the system work better. Compound turbos are extremely miss understood and hopefully the video sheds some light onto what is actually going on with each turbo and the motor.
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I have ran air-to-air cooling between stages as well as after the manifold turbo since 2015, and I can confirm that it makes a difference at full boost big enough that you don’t need a dyno or fancy monitoring to see it. The issue with interstage cooling is added lag, because the manifold turbo doesn’t like having to pull all of its air through the interstage cooler plus the extra piping and atmosphere turbo. I solved this partly by playing with pipe size leading to the manifold compressor inlet, as well as adding a check-valve to allow more air into the manifold charger so it can spool better.
That’s super rad. Kinda similar to what cummins did on some of the newer engines. I agree 💯 that the interstage cooling if fitment allows works wonders vs trying to run a aftercooler large enough to deal with the temps/flow rate encountered on higher flowing high pressure engine setups.
I need to sit down an have some beers with you! You seem like me an love the nitty gritty details that make things not only work but efficiently! Cant wait for more vids
Any time. The mini fridge is always loaded, I am in central CA but we do travel for truck pulling and soon diesel drag racing events. A lot of this goes back to not making the power we “expected based on the Internet” so it turned into why is this occurring and what changes can I make to correct it. Thank you for watching
I've always thought interstage cooling would be the way to go but after hearing you explain inlet temps post intercooler of a typical compound setup, I definitely want to fab up a W2A interstage cooler.
Fantastic video man!!
For many applications it just won’t fit. And in many cases big power is being made without it but it by no means that a lot is not being left of the table. It is done in truck and tractor pulling when allowed and is also gaining in popularity in pro mod cars that run 3.5 sec 1/8th Mile’s. Todd at pdd runs a interstage air to water cooler. Many do this with water injection. Shane t has a 4 cylinder 2.x liter motor running on methanol, I stee stage cooling, 125-150 psi compound setup doing 2500 hp working on getting to 3k. And has a great interview on you tube of it. Triple turbo 4 cylinder engine.
@@savagefabrication795 I had no idea Todd was running interstage. I moved the batteries out from under the hood of my 2nd gen so I've got some room for the A2W. I'll check out Shane T. Sounds Insane!
@@savagefabrication795 I'm just some kid with an s10
I have been tracking down this very piece of insight you have bestowed upon the world
I like to be different and compound makes so much logical sense
I watched Todd at power driven diesel as well, he definitely knows his stuff
But the way you explained it was so concise, and straightforward
Also, slow enough that I could make sense of it
And yes, I still had to rewind
@@austinsturgeon4055 also check out my updated video or just call/text me 2094844227 and I can correct some small errors I made. In all honesty it all still comes out essentially the same but I can simplify the heck out of it for ya.
@@austinsturgeon4055 also check out my updated video or just call/text me 2094844227 and I can correct some small errors I made. In all honesty it all still comes out essentially the same but I can simplify the heck out of it for ya.
Ok, what turbo would you choose to use on an 08 6.7 for hauling a small camper around the country? I Would like to keep VGT but not necessary.
All I have currently is a 5" exhaust turbine back and mini-max delete tune.
The vgt’s are limited in how crazy the turbine wheel can get. So staying vgt using htt’s performance chargers are about as good as it is going to get but it’s not a large capacity gain nor egt control gain due to the turbine wheel itself. We have had good results going 67/67/9 351cw on 6.7’s that put in work as well as josh at horse torques liking the 67/83/xx s400 chargers with a proper tune and converter do really well when it comes to putting in work while still having a nice rev range.
Where could I go to get a set of compound turbos to be “sized right for the application”? @11:10
They do multiply. I thought you would contradict yourself going thru the calcs, but then for some reason you added an extra 44.7 to your 2nd PR calc, so you got 2.67 instead of the correct 1.67. ~75psi : ~15psi absolute is a total PR of ~5:1 for the system. 3:1 PR for first stage times the 1.67:1 PR for the second stage. 3 x 1.67 = 5.
Looks like you used the same mindset on the 2nd PR calc as the 1st calc. The 30 PSI 'boost' on the first turbo is the gauge pressure, so you added 1atm to get absolute pressure 44.7. You did the same the 2nd turbo which is unnecessary since you're 44.7 inlet pressure is already in absolute pressure. If this is confusing, then draw a diagram and make sure all your pressure values are in absolute pressure.
DR of 5.5 @ 60psi boost? Do engines running 60psi of boost, regardless of charge method, make 5.5 times the HP? No.
The DR calcs are more complex because intercooler efficiency comes into play along with compressor efficiency. In an ideal world with no losses 5x pressure would give you 5x density. If you have a huge intercooler with ice water running thru it so its efficiency could be ~110% dropping air temps well below ambient, then you could hit a DR of 5.5:1. Without ice water, or in any air/air setup, you lose ~5-15% air density thru each stage (depending on your compressor and intercooler efficiencies), which ends up at ~10-25% thru a 2 stage compound turbo system. So your ideal 5:1 DR turns into 4.5:1 at best and probably closer to 3.75:1.
Thank you. I knew whay he was saying wasnt correct.
60psi would be a PR of 5.08 not 5.5 to start with. And also with many engines the hp (ve) goes upp MORE then the PR would sugest, on both gas and diesel this happens.
You talk about intercooler efficiency being complicated but gues what, you got pressuer and temprature and thats it, not complicated at all. There is no magic about it and what he says in the video is all correct accept for the PR misscalculation at the begining.
Compound turbochargers seem to have remarkable power increase potential. Reminds me of what Eric Jarvis (Mad Scientist Auto) did with a compound turbocharged Honda K24 S2000 with a 88mm turbocharger fed by a 7685 turbocharger well exceeding 1000hp. I just never really understood how compound turbochargers worked. I still haven't understood it completely (yet).
It gets pretty wild. But I severely need to re do this video as it uses steps that are technically incorrect. Guess that’s what happens as ya start to make more sense of things haha.
That's very interesting. Seems like everybody are talking about boost multiplying not adding. But it's logical the way you explained it.
I have one not typical question. What is in your opinion turbo which you don't need any wastegating for 3 liter diesel motor spinning max 6000rpm. So basically 5.9 cummins limited to 3050rpm :)
I have on mind efr7670 (fancy sxe257)as HP and sxe372 as LP. And I hope 372 wouldn't need any WG. Motor will take 75psi
Because he screwed up the math.
@@vica153 So you think when calculating compounds you should multiply pressure (density) ratio? The results seems to be similar up to around 30psi both stages. Only with higher pressures the results are different when adding or multiplying
@@deadlift4life1 Yes. The vertical axis on the compressor map is pressure ratio. Its the ratio of outlet pressure to inlet pressure. Along the 2.0 PR line the turbo is multiplying the inlet pressure by 2. Doesn't matter if that's atmospheric ~15psi turned into 30psi(15psi boost) or 30psi from another turbo into 60psi or 10psi (air pressure going over mountain pass) into 20psi.
A turbo at a 3.0 PR pushing into a turbo at 2.67 PR would result in a total PR of 8. That's 117psi working at sea level, which is exactly why compound turbo setups have no problem pushing 150psi of boost. If those pressure ratios only hit 60psi, then both turbos at a PR of 3.5 would be struggling to reach 100psi.
I don’t have any experience with the efr turbos (I would like too but it’s hard to get any of the diesel people here to spend that kinda money on a turbo) so what I would look at first and foremost is to see who is running that turbo at the boost you would like to run and note down where peak torque is at. Rule of thumb using displacement like you did above, get a idea even if it’s not the same engine your going to run. If your goal is peak hp at 6000 rpms then peak torque needs to be at 5000 rpms, maybe 4500 (really depends on the injection pump curve, how the turbine is going into choke flow, and what the head is doing) the s372 you will have no issues with as the atmo, a shop we sell through at a event ran a s372/74/.91 on a verified 1400 whp truck (using compounds) the dyno class was small single so compounds came off and the s372 went on. No waste gates, made 780 whp with a pull to 4,000 rpms on the same tune up for 1400 whp. We had barely edged them out with 811 whp on a hx55, but a side note to the competition is that we got to visually see what a s372 can support on diesel fuel as a average (dynos all read different) and that’s it won’t over speed as long as the engine speed vs flow rate is all within its safe range. I do believe if they tried taking the s372 to 5,000 rpms on the 5.9L at the same boost level it would have in fact failed haha. So correlating that back your way, 60 psi at 8,000 rpms total would be where the danger zone may lie depending on how much intercooling is being done.
If your wanting a setup that makes peak power at a lower engine speed then all you do is move that peak torque location down. Similar to selecting the cam shaft for a spark ignition motor. Looking for the rpm range we want it to do the best in.
S252 sxe 0.84ar paired with a s369 sxe 0.91ar would be a much more efficient setup, no wg:s needed. Better spooling and way more cost effective then a efr turbo.
Can you put your formulas in the description of the video? Thanks for the video
Yeah. Although it’s technically wrong. Lol. You arrive at the end at pretty close to the correct spot but it is incorrect. Which is kinda funny lol. I will make a new video of the correct way to do it.
this guy would drive a lip reader insane...
i had to go do some investigations...
the pressure ratios are easy.
the issue is matching the mass flow of two compressor maps so the things work together, sharing the work between them equally, or as best as possible.
and whilst it seems subtle, there is a big difference between a map that is measured in mass flow, kg or lbs/min or sec, versus CFM or M3....
you have to work on the volume for compounds. its been compressed. the mass flow increases. a map in mass flow units has to be scaled... where a little compressor would choke out if it were running atmospheric to PR3 alone, it will still be in its happy zone when fed at 2 atmospheres and still running PR3. the mass flow has more than doubled, its way beyond what the map says it can handle... but the volume flow at that pressure (2 bar) is still within its capabilities.
That is correct. I’ve definitely learned quite a bit since this original video and your comment is spot on :)
It would be easier to calculate in bars instead of psi because 1 bar = 14.7psi.
PR , BAR psiG, or psiA same same just changes what and how many conversations are required. Counting bar in psi is like counting by prime numbers, do it enough to get good and it's not even a thought the auto pilot kicks in.
Better calculate in pressure ratio like engineers do.
@V8Lenny what is the actual difference in value between 1 bar, 2BarA 14.7psi, 29.4psia and the metric equivalents ( layman's unit) and 2 PR ( turbo engineers unit)
How dose using engineering units help with using the compressor map with 1lb of air at 1,2,or 3barA vs 1 lb of air at 0, 14.7, 29.4psi ,
Hint: thermal is a part of the answer .
Without mass the PR has no value to an engineer , as an engineer would refuse to do the exercises without that hafe of the equation.
@@daviddroescher compressor maps are in pressure ratios.
@V8Lenny so Now apply that vast knowledge to the multiple question asked.
the second this man used his calculator to add 60+14.7 i closed the video
👍
I think there's some good information here. The presentation is confusing, however. I wish you'd re-do the video and show all the formulas before plugging in your specific numbers. That would be very helpful. Also you need to watch your mathematical () parantheses. 30+14.7-14.7 is not the same as (30+14.7)/14.7, as others in the comments have pointed out.