realise* - depending on the parts of the world you live in, for example in the UK for a lot of words S's replace Z's. You ought to look up localisations of words next time before you "correct" a correct spelling.
What makes this so good is this is people telling you what you need to know and how to build things instead of acting and get you to buy product from a sponsor.
Boys.... I would be really interested in watch the dyno of the compound turbo set... It would great to see how the tuner uses the 3 controls and what issues are thrown up. Another nice episode
I am absolutely loving these videos where we just sit and listen to a master of his craft talk about what he knows best. It's informative, and interesting, and it really showcases not just how much you guys know, but how smart y'all really are. You explain things in a way that makes a layperson like myself be able to understand, and that's a real skill. They don't call you Turbo Yoda for nothing! What you're doing is great. Keep up the awesome.
Congrats on your first year of Skid Factory boys. It's been great following the progress of your builds and hope for many more years of success for you.
Compounds are probably the hardest to tune, making the transition smooth is double the tablespoon have to modify basically. When tuned correctly it can drive like stock and be a monster, my Cummins runs compounds and now limited by fuel… it tows like tug boat, it’s a beast, and being able to have the air for your engine is awesome. The Cummins guys run compound just like this but they run triples just for the dyno numbers, but you will notice when they sled pull, the run compound, or just one big single cuz your literally pegged, those big singles though take nitrous to spool the turbo but the triple doesn’t need nitrous to spool. Because the primary turbo helps, but you will be limited in dyno numbers overall on a compound your power band will be 5,000 rpm of usable driving instead of spooling up at 4400 rpm on a Cummins and using 1500 rpm of usable power.
Never heard of this before and its very fascinating to me, I've heard of a turbo and supercharger combo before. Thanks for sharing and as always Keep Building👍
The reason you would want to go to triple turbo setups is to allow for better spooling speed vs one very large atmospheric charger. It also allows for lower smoke output on the street during transient throttle on non emissions diesels making above about 1000hp while making throttle more like a factory truck.
Aweseome video my guy. Was getting a chuckle listening to the complaining of mounting t3's and the wastegate when im trying to figure out how to mount an s400 under the hood with a v8 taking up most of the room. You do clean work and i like the no bullshit.
First off i know very little about diesel turbo engines, but i'm glad i watched this video. I was always under the impression that compounding meant that the small turbo was on the manifold then feed the larger turbo with the pressured fresh air (or what would usually go to the TB).
And there I was remarking in the last eps comments that it was a pity you didnt touch on Compound Turbo set-ups..... :v Glad you saved it for a separate, more in-depth & practical episode- thank you!
With the setup shown in this video, there's no wastegate dumping to atmosphere. Every kilo of air that enters the exhaust manifold is going full speed ahead through that secondary turbo. I get it, works great on a diesel application, but gasoline/E85 applications require any excess of energy to be dumped to atmosphere in order to keep the boost in check. By using an exhaust manifold reference for the primary turbo wastegate and using an intake manifold runner reference for the secondary turbo wastegate, we can both keep backpressure under control across the entire spool range and rev-range; and we can also control boost in a linear fashion without dips in the curve. Your backpressure and boost curves would look like a flat line after 3000RPM because everything would be set mechanically in a controlled fashion. Even if you wanted to rev it to 9000RPM, you would still have the possibility of seeing 30lbs of boost from 3000 RPM to 9000 RPM, and that makes a damn fun and damn efficient street car and effective race car.
It makes me happy I just so happen to have the same shield as Al I didn’t think anything about it when I bought it I’m just lucky, you guys are a huge inspiration
I believe the reason why they are now using 2 turbos as the secondary instead of one is because it fixes what you said about it takes more time to build boost having one large turbo as your secondary. By having two smaller turbos for the secondary, when your building RPM's you can direct the air thru one of the smaller secondary turbos to quicker reach it's maximum range of boost efficiency quicker than the increasing exhaust gas can be used to reach the primary range of efficiency for the 2nd smaller turbo, thus making the system as a whole work more efficiently.
I always thought Turbo Compounding was when the exhaust gases drive a turbine that is directly connected to the crankshaft thus increasing efficiency and lowering fuel consumption. I.e. Wright R-3350 radial aircraft engine. Great vids chaps! Massive fan of your work!!
In the aviation world, a 'compound turbo' is a weird sort of reverse-supercharger, where the exhaust gas is used to push a turbine that is used to help push the propeller shaft.
I like the way you think Al.. i was always told is what you are saying about the pressures across the head best way is equal in and equal out across the head .. placing the external waste gate on the small turbo and allowing the restriction to move around it but still feed the bigger is the way i would do it
Good explanation of how the compound system works. I think Alen misspoke at one point though, a turbine isn't using the exhaust heat to spin it is using the kinetic energy from the exhaust flow leaving the engine.
It uses both kinetic and thermal energy. The temperature drop across the turbine has a direct relationship to the energy recovered from the exhaust stream. Kinetic energy recovery is dependent on turbine blade design, and how effectively pulse energy is preserved in the exhaust manifold.
The real benefit amounts to lower boost threshold and lag minimization, but the cost, complexity, weight, and space required for compound (i.e., sequential) setups is such that many people choose to go the single-turbo route.
I've always wanted to do this on a gas engine like a t3t4 t04e and then like a stock diesel turbo like a holset. Only differences both turbos would be Waste gated. Bunch of low end torque with decent mid and high range.
I have a genuine question for turbo Yoda. I (thought) I understood the basics on how turbos work. For this compound setup, I understand that both turbos use the exhaust gasses to get spinning, but why is it that the smaller turbo is getting fed through its intake from the charge port on the large turbo. Shouldn't it be the other way? Spin up that small turbo first, use the charge that it creates to spin that large turbo quicker, then use the charge from the large turbo to feed the engine. In your demonstration, you were feeding the small turbo with the big turbo, which meant that the small turbo was going to be feeding the engine. Am I just misunderstanding what is being accomplished here and all compound turbo setups are like this where it goes big->small->engine? Shouldn't it go small->big->engine?
The large turbo needs to be the one that breathes from the atmosphere because the bigger compressor inlet diameter can flow a higher mass flow of air before reaching the Mach limit.
Don't forget that at high boost pressure your dynamic timing is significantly advanced.... You also need to shorten the length of time the fuel pulse is occurring and the only way to get the correct volume in a short time frame is larger injectors
Awesome job looks much better, hope it brings results. Keep up the good work Skid Factory is one of my favorite channels. Wish I could have made the meet and greet in Dunville but it was the same day my girl friend was getting bone marrow transplant :(
Hi Guys - I saw that Borg Warner had developed a twin scroll turbo with a variable diverted which could channel all exhaust gasses into one turbine housing and then progressively open up the second intake on the second larger scroll. It looked to have achieved a similar trick to the compound turbo but in a much simpler package. the diverted tab was also cast iron and very robust so very good for petrol engines with high EGTs. Have you seen these turbos in the marketplace? It was at SEMA a few years ago and it was covered on engineering Explained.
Just ream the hole of the internal waste larger. Back pressure you can measure easily, just run a pressure gauge in the primary turbo housing and you can see what rpm it starts to pressurise over the boost pressure = back pressure
I always wondered about using the wastegate that way. Super interested in seeing some data on this combo. I figured there's got to be a reason it's not done. Probably about the efficiency range if I was gonna guess. Overspeeding maybe.
I love the way you explain turbos. I know how they work but I have a very hard time explaining it to others. Especially explaining it in a way that doesn't sound over complicated. Somehow I end up putting in more difficult terms rather than simplifying it lol. Or I just end up on a tangent about one specific attribute and I lose my train of thought, over explain one aspect and not explain another at all. I guess my ADHD might have a bit to do with that lol.
The internal waste gate won’t work because, as you said, once the smaller turbo spools up, it’s essentially a larger engine. Now all the exhaust gas from the “larger” engine must travel through the smaller turbo turbine and waste gate, which will strangle it. By fitting an external wastegate, you’re increasing the bypass flow capability, and reducing back pressure (as much as you can anyway before you have to drive the 2nd turbo). For the same reason, the external gate should be sized larger than you normally would for a 4.2L engine.
Noting the space limitations on this build it may not be viable, but adding an intercooler between the turbochargers will further improve efficiency and boost potential.
Hey guys I have an idea for a video for you guys. I see a lot of videos focusing on the basic tools you'll need to complete a job but you hardly ever see a professional like Al explaining what tools he has bought that make his life easier when working on so many different cars. I see Marty fell in love with your multi tool with the ratchet head attachment. I would be very interested in seeing what tools or power tools you have bought and will never go back to the old way type of thing. No matter how expensive they may be what tools have paid for themselves ten fold. That kind of thing. I am slowing getting use to wrenching on my own cars and Id be very interested in seeing what someone like Al considers his most worth while purchases for his shop. Or personal garage. And I'm sure a lot of people would too. Cheers guys love the show.
You need a LOT more wastegate than a typical internal gate. Same for the big turbo, it should be 1.5-2x higher flow than the small. The reason the small turbo can flow so much more - it's ingesting compressed air, which takes up less space. It's also getting most exhaust bypassed thru the wastegate. I just hope you guys get some vids of it on the dyno!
A lot of twin dam stuff I've seen has two feeds, like a valve, so 1st spools up then once the bigger one starts to flow, then a valve closes the little Turbo off.
sirgallium Yes. It’s great for Low and top end power you just need to be able to tune the wastegates well. I’ve had a compound setup on my Subaru Forester and it was great. Had a td04 and a GT35. Quick responsive down the bottom and top end power. Since then I’ve rebuilt the engine with valve springs and retainers and ported the heads so it can flow more air. Still currently building a 3rd compound setup.
Just to be clear. A turbo doesn't directly increase an engine's efficiency. It lets you burn more fuel for more hp meaning higher hp/liter. In effect a small turbo engine can output the same as a bigger one. That's where the better efficiency comes from -> small block = less friction and losses =better efficiency.
This is by far my favorite RU-vid channel thank you for making videos... wish I could have met you guys when you were in Canada maybe next time. I'll how do you feel about doing compound turbos on gas vehicles or spark plug vehicles to get rid of lag or help with lag or boost threshold whatever you want to call it.
There aren't many petrol engines that can handle the power and loading associated with compound turbos so it isn't often done. There are a few drag cars using it on smaller engines with high strength like 4G63 and 2JZ. It's not really a practical thing for a road going petrol engine.
you should of added a bypass to the larger tubo compressor outlet (bypassing the smaller) to the intake so that the smaller doesnt cause restriction when the larger 1 is at boost, great work though, can you cover some compound setups with turbos and superchargers? thanks
