Freiburger Explains Supercharger Basics - Roadkill Extra
Roadkill Garage episode 24 features a revamp of the Crusher Impala, the 1969 Chevy that’s now powered by a 489ci, supercharged big-block Chevy that was formerly used in the Hot Rod magazine Crusher Camaro. During the filming of the episode, David Freiburger took a moment to appreciate the Weiand 8-71 blower atop the engine and to explain supercharger basics-like, what does “roots blower” and “8-71” really mean? Find out in this episode of Roadkill Extra, the show with vlogs and outtakes that appears every weekday on MotorTrendOnDemand.com.
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As you watch, cruise over to Facebook.com/RoadkillShow, follow us, and watch for future posts asking for your questions to be answered on the Q&A sessions that are posted every Friday on Roadkill Extra Powered by Dodge.
Just wanted to point out a roots blower is so much cooler than a turbo hands down .
I tend to agree. :)
Eh depends what you have i4-V6 or v10-v12 I would turbo v8 would be the only thing I would supercharge and even then the whining gets annoying after like that a hour
As the El Paso Taco girl says. Por que no los dos? TWINCHARGING!!!!
Yes sir...no doubt👍😎
@catalyst_99 I agree turbos are better , but not as cool looking as a 871 supercharger setting on top of a 426 Hemi in something like a 1970 Plymouth Roadrunner
I'm a mopar guy but I love that Crusher Impala. Something about old rusty American Iron with a big v8...
mopar guy here too and i love that muscle truck.
Hey guys, old school muscle is old school muscle. Things were simple back then.. Die-Hard Mopar guy myself as well, but you just can't beat a SBC/BBC for that ratty, cheap fun!
thats why i like mother mopar and im a chevy guy
@@Ecosse57 the Muscle Truck is cooler than show trucks that sell for 5X what the MT is worth.
Hey mopar made the 440. Thats a big American rusty V8.
You forgot the roots blower's most important advantage - the wickckcked sound it makes! :-D
That would be the pulley/belt combo.
aah , the whine.. the whine
intimidation factor of pulling up on the line with your shiny fuel delivery system sitting above the hood and the blower whining away.
@@CarsandCats It's a combination of things. Yes, the belt is part of the equation. I had to run a 16 rib belt on my 10-71 a few years ago at a local event when my belt broke. I had a new in a box, but it was damaged. A guy there had a set of Whipple 16 rib pullies he lent me so I could run. The sound changed surprisingly little. I have a three lobe high helix Blowershop blower, and those rotors scream, they scream a lot louder than the cogged belt.
WEEEEEEEEEEEEEEE WAAAAAAAAAAAAAAAAAAA
One "simple" explanation for what a blower does is that it improves volumetric efficiency. I once had a teacher ask the bonus question on an exam in auto class. The question was can an engine achieve 100 volumetric efficiency and I said "yes even more" He gave me a zero for that answer until I explained to him it was possible with a blown engine. He argued that I knew that is not what he meant but I explained that I also think in terms of hot rodding so my answer was valid. I ended up getting the two marks for that bonus question with a 102% on my exam. Was one of my best days ever in school!
you could have also cited two strokes, with their scavenging trickery and dynamic CR.
Musta been an old auto class. N/A engines regularly exceed 100% VE these days. Even a strong street engine will hit 105%-110%. When I worked with sprint car setups, they commonly hit 120%+ if I remember correctly. But I do have an old (1962 I believe) Ed Isky book about valve timing. And on one of the first pages he says flat out you'll never exceed 100% VE. Just old school thinking.
yeah, with tuned intake ports a n/a enging can reach more then 100% ve... basically the same as an expansion pipe on a 2 stroke
isn't it all in the exhaust scavenging for N/As? so that like in a two stroke the exhaust pulls the intake into the chamber (pushes it because haha physics) although to a much smaller degree than on a 2t.
jacob fraser Doesn't take tuned intake ports. It can be done on old V8s without any kind of fancy intake. Just takes the right setup. Done properly. Good cam, heads, intake, exhaust. All working together. Vicious Slayer It's not ALL in the exhaust scavenging. But the only way to get 100%+ VE is to flow more than the cylinder holds. Obviously that air has to go somewhere, generally out the exhaust (I won't get into variable compression engines). Scavenging does refer to the effect of having an exhaust that flows properly to pull air from the intake behind it. But in order for that to work. You have to have a cam/heads/intake capable of doing it as well. Exhaust can't pull from the intake if the valve is closed for example. At the same time, the piston/intake also works with scavenging to create higher VE. It just doesn't contribute as much. But once again, can't work if the engine isn't setup properly. ChrisHallet83 Well, it's obviously physically possible since engines do it all the time. Especially in the muscle/hot rod/racing car world. So you're statement is flat out wrong. You're not creating something from nothing. The engine is simply moving more air than the cylinders can hold. There's no magic there. VE doesn't refer to how much air the cylinders can HOLD it refers to how much air the engine moves in relation to how much air the cylinders hold. More air moved than the cylinders hold? 100%+ VE. This is a basic engine concept, so I suggest you learn more about them before making an obviously wrong statement.
Man I never get tired of hearing the tech tips!! Best gear head show around!!!
I remember years ago I was working on an old federal signal siren. It was a thunder bolt kind which uses a roots style blower to give it a distinct sound. It's spun by an electric motor mounted at the top or bottom of the pole it's mounted on, and blows air into the spinning rotor of the siren to give it a buzzing like sound.
That mostly depends on the blower type. I was under a thunderbolt 1000 with a C series blower and the buzz on that thing was incredibly loud. Then another time I was under a 1000t with a 6M blower and it was a lot quieter. There’s another siren that uses a supercharger to add noise and it’s called the ACA hurricane. They’re almost all gone now though.
I love roots blowers. They just look so cool.
The blower whine is awesome, screw type though, powaaaaahhh
Twin Screw are more efficient and just as instant.
Lifted_Above yea but they dont look as cool.
Which is very important when the hood is down and you're looking down the highway 1/10th of a mile for cops waiting to ruin the fun.
As long as it can fit under a 2 or 3 inch cowl hood.
Really appreciate these types of videos. I could watch them all day.
0:53 Thanks for explaining that often overlooked piece of information. Turbos were originally called turbosuperchargers.
There was a Highway Patrol episode where the getaway car was a "Supercharged" roadster. The car in the show had no supercharger, they probably couldn't find one, but I guess we all just let it slide.
Awesome video.Two cycle detroit diesels dont have intake valves.The blower mounts to the block with a port in it that corresponds with the port on the blower.It forces air into whats called an air box that surrounds the cylinders or sleeves.The sleeves have a row of holes all the way around them in about the middle that allows the air into each cylinder.Thats how 2 cycle Detroits get their air.On a Detroit the blower is gear driven.They sure look awesome on a V8 gas engine.
Hey David, We love your shows. My wife even loves the roadkill episodes. Thanks to you and the other guys for sharing your vast amounts of knowledge with us all. Being a car guy all my life I still learn something every episode. Boy sometimes you guys are gluttons for punishment. But we love to watch. Keep up the good work!
Freiburger, you are correct on the scavenging of the two stroke diesels, and the blower blowing all of the exhaust out. What you missed, though, is that they won't run without forced induction. In small, gas two strokes, the fuel/air charge is drawn into the crank case, then pressurised and forced into the cylinder by the piston traveling down. One: Detroits used a common crank case, and standard oiling, making this impossible. Two: when diesel engines get introduced to an outside fuel source, including their own oil, they run away. SO, air has to be forced in "artificially."
Beat me to it! steve
Very interesting, good presentation, David. Thank you.
I love when people question Freiburger stating he was wrong then pulls out this little nugget of info and blows everyone’s mind #becausefreiburger
Learned something new today, thanks for the nuggets
Love your videos Freiburger, keep them coming.....
Nice and good info. Being from Sweden I just wanted to point out that since you mentioned "twin Screw" blowers, I think the Lysholm Supercharger i worth mentioning; The Twin Screw Supercharger was invented by Mr. Alf Lysholm® in the 1930's, who was then Chief Engineer at Svenska Rotor Maskiner AB (SRM). The twin screw design was developed to replace dynamic type (centrifugal and axial turbine) compressors, for boosted engines. With the slim profile and awsome performance they were banned at US dragstrips once, being supreme to GMC:s. Keep up the good vid's. Mike
Nice
I'm thinking a compressor/supercharger/blower is more like having a bigger engine. In both cases it will suck in more air/fuel because it can "pump a larger volume".
I love the way you explained it
Very nice presentation thumbs up!! Not only looks cool but it intimates other drivers lol Kool factor !!
The local community tech college had a straight 6 6-71 Detroit Diesel that was rebuilt by yours truly. It was plucked out of a WW II Navy PT boat (they usually had 2 mounted side by side, although there were some special forces boats rumored that only had 1). By the governor controls there was a extra selection for power level,,and it was stenciled "BATTLE MODE".,, which gained you a handful of extra rpms on a 2 stroke diesel,,but they were very quick rpms at that point. Took 2 donor blowers apart and made 1 good one out of all the bits. The little 4-71's went into alot of smaller sea boats. You could't wear them out. Drove me sum 6-71 trucks,,and Silver Series 8v92's with turbo directly over blower(575 hp,,torque rating was "Whoo-hoo!" when it 2 stroked).
Freiburger, you're pretty much spot on with the Detroit. The blower is an air pump used for scavenging. The exhaust valves are on the top of the cylinder, and there are no intake valves. Instead, there are intake ports down low on the cylinder sleeves. I was told years ago at UTI that since these can't run without the blower, this Detroit is actually considered naturally aspirated. On a side note these are bastard engines and a pain to work on!! Keep up the great work buddy!!
I love that you talk about how it started, the idea of the "hot rod" guys putting a GMC diesel type blower onto a flathead or GMC 6 cyl or anything back after WW2 was using what they had access to and using their skill, as you could not just go and buy one of these kits and put it on. I love seeing the old pictures of the multiple belts used to run these things before the "toothed" belts came into play, it was using what you had and making it work! A lot of these guys worked on airplanes and trucks in the war so they had the idea of the concept, they just needed to figure out what to use, and creativity is the mother of invention! Thanks Freiburger!
I think of it this way - a roots blower is essentially increasing your displacement across the board, centrifugal superchargers increase your displacement, this increase varies by RPM, and a turbo increases your displacement which varies by RPM and throttle input (or more realistically exhaust pressure); hence the ability of a turbo to generate the most power and/or be the most efficient.
Biggist engine ive ever worked on was a Detroit v16 92 super turbo. Sounds like gods pants tearing. Super cool to see a turbo blowing directly into a roots blower. Heat load would be a problem but it was a marine raw water cooling. Only 1200 hp but well over 3k fp trq.
These videos are the best!!!
Thank You for this video. Ever run one on a 4x4 trail rig
Great video. Your knowledge on superchargers is correct.
he doesn't need your approval if its correct or not.
Burning Mysteria . lololol
I hope to hear about the benefits of blow through Vs suck through on turbos/super chargers. As blow through always seemed a better idea, keep the fuel atomized better.
Big_Adam_2050 kick loguc to the cerb bo the impossible
I don't know if that'd make a difference, as it's the same volume of air going through. But then again, if it's under the supercharger, the velocity would be lower. Perhaps that would actually hurt atomization.
Fuel is horsepower when it's mixed with the correct amount of air to burn it. Everything you do to improve power basically centers around being able to burn more fuel/air mix.
GREAT VIDEO DAVID!!! I AGREE WITH YOU 100%. I LOVE ROOTS BLOWERS AS WELL.
Good job explaining
Nice and informative guide. No criticism, but it at the start, it might be helpful to mention that in a N/A engine, the air is naturally drawn through the carburettor, as the pistons go downwards. But in a supercharged engine, that air is additionally forced, or ‘blown’ in by the supercharger, which acts as an air pump.
Fry man your making my life Soo much easier
Roadkill best show ever
well said you made me understand.
Awesome video 👌👍🤘
Freiburger: Useful videos as always! Can you do one showing the parasitic losses of a turbo vs. a positive displacement supercharger (preferably a twin-screw like used in modern OEM SCs, not roots)? I.e. pick a turbo and supercharger that makes roughly the same max HP on the same engine and then disconnect the boost (for the SC it's difficult but maybe mount it on a bracket away from the carb but still have the belt go through?) and see how much power they're stealing against the same engine naturally aspirated? I don't think this has been done. Thanks!
excellent explanation
We have a 671 2 stroke diesel (from the 50's) at our Community college here. Cast into the block is "GMC"! You are correct Sir, the early "Detroits" were made by GMC.
Freiburger is the man!
Note: Not all Roots blowers have three vanes, some have two like those on Detroit _53 engines.
I would like the myth of "high compression" in a "supercharged" engine to be discussed. Too many people have added superchargers to stock high compression engines. Then got half assed tunning, & chips. Then burnt up a piston and blamed the compression ratio. Other factors should have been thought of. The ring gap? Correct AFR?
One of the rat rods featured in ZZ Top's "I gotsta get paid" video has a Nivaro roots supercharger on it.
Great info thanks
Geat info . Thanks
Parasitic loss on a top fuel dragster is believed to be over 600 HP to drive the blower. 😬
The two stroke diesels used the supercharger to fill the cylinder. A four stroke unit uses the pistons down stroke to pull in the charge air but the two stroke can't so it needed a blower to push the air in. Smaller two stroke petrols compress the air in the crank case below the piston and use that in the combustion process hence needing to mix oil with the fuel.
GREAT VIDEO..
the only "root blower" I got in my car is when the old lady is riding shotgun.......come on now! lol
I'd love to see you expand your air cleaner test with the blower motor.
Thanks for explaining ,, your right ,, it do look good 😊
More roadkill extra videos then there is actual roadkill episodes
Israel Cardona That’s correct. Roadkill Extra airs every weekday on Motor Trend On Demand and just Saturdays on YT
Thank you so much, Freiburger! :)
@Elmer Cricket That's a nice vette!!
From what I understand a 2 stroke diesel can't aspirate on its on so the supercharger also makes it breathe in addition to blowing the exhaust out
Dave - roadkill idea - instead of a belt-driven supercharger, hook up a twin-v motorcycle engine to the supercharger shaft. That sounds like it would account for your parasitic losses, plus it would look freaking cool.
My god....I'll be back going to the garage
Didn't they already do something similar with the boost caboose?
Syncing blower drive engine RPM with primary engine RPM would be a headache.
Yup.
Kevin Opalka Kind of, but this would be so much cooler
I learn more watching this motortrend channel than any other car shows on velocity or videos on youtube. Short and some with a lot of comparisons and analysis. Good job guys keep it up. Please do a budget build episode on mustang. I have a 2002 mustang v6 that I didn't pay a lot of money for but I want more power without going to a v8 until I can afford to trade up to a v8.
if its getting more air in it and more Feul .. Did you also set bigger Jets in it ?? and are the slots made bigger in the pistonrings ?
There is actually a formula for the modified effective compression ratio once boost is added, and it's not just ratio*(abs pressure/atmosphere pressure)
I love root blowers because of the insane whine
I want to put a blower on my motor but its a bone stock tbi 350 with swirlport heads. Wonder if it would we worth it or not
Can I get some thought on an engine swap I've been thinking about? I have a Ford F-150 with a manual trans with V6 in a regular cab and a narrow bed, I'm wanting to do an engine swap with a 5.4 Triton V8 with a supercharger. But I want to keep the manual trans in it, but I don't know what kind of computer I would need as well what trans can take the power and still fit in the truck. And would I need a new rear end for it? Would I have to replace the pistons and cam in the engine?
Hey Dave, you are correct on the compression ratio myth being wrong. They air pump adage is closer to correct. The more air the engine pumps the more fuel you can stick with it meaning the more power it makes. You can typically estimate the engines power at a certain boost level by taking the boost, adding it to the atmospheric pressure of the location that you are at and then dividing all of that by the local atmospheric pressure again. Then you multiply that number by the old hp number and subtract the amount of power that you can guesstimate the compressor is eating either directly (pretty easy if you can find a compressor map) or from restricting the exhaust with a turbo. And bam... you’ll get a reasonable number to expect after supercharging or increasing your boost etc. if you don’t end up near that number you may have belt slip, a lean condition, trouble maintaining spark or some other issue contributing . Anyway New hp =old hp((boost+atmospheric pressure)/atmospheric pressure)- compressor loss
He understands the most intricate knowledge of gas engines, but doesnt understand diesels lol
I hope youre right, diesels are pretty straight forward
On a 2-stroke Detroit Diesel it's a blower, not a supercharger. It's only job is scavenging - clear all exhaust gases from the cylinders and fill 'em with fresh air. "Airbox" pressure will be above atmospheric, but very little. A 2-stroke Detroit without a turbo (or turbos), is naturally aspirated.
The wonder of a supercharer is to take your current 350 cubic inch air pump that comes apart at about 6500 rpm, bolt a 200 cubic inch roots pump on top of it, add a drive reduction so you can spin that one at twice the speed, so you can have the effective power of a 400 cubic inch engine. And well, they make bigger pumps too.
Hi, I’m interested in how the -71 series blowers were create. Yeah longer and longer rotors and cases, but who and how were these done. I’ve searched far and wide but few have lived through the era these blowers how were the rotors made longer before billit ones were made on cnc machines. Were there on gear shafts made and section of rotors cut off to fit then various spacers made so they fit in the cases. Then the tunnel case ends and trinangular opening on the bottom. What I’m looking for is a time line with construction.
I want this in the FB Rx-7.
on a episode of engine masters you should compare high compression vs boost?
Understood the last part really well, the rest of it--about half. :-)
i really would have liked if you had explained the effects of installing a (non boost) camshaft with a supercharger how it affects the vacuum operated accessories like boost bypass valves, egr valves and brake boosters
N/A cams are usually "hotter cams" than for boosted applications. The longer duration and larger overlap will increase your top end power, but reduce vac at idle. Should not compromise accesories unless you go for a serious N/A race cam.
I love em too !
Just want to ask something we're does carburetor go when installing supercharger
When I was a mechanic in the Army, the M113 personnel carrier had a Detroit Diesel with a blower. Mysteriously a lot of those blowers disappeared...…...lol
Did a lot magically resurface in the hot rod scene?
That's absolutely what happened to them
How necessary are aftercooler cores for Roots s/c's?
What's your opinion on compressed air supercharging
A 2-stroke diesel has no intake or exhaust stroke. The intake ports are uncovered and the exhaust valves are open when the piston is at the bottom of the stroke so the air in the cylinder must be completely changed at that point. If it weren't for the blower pushing fresh air in which pushes the spent gas out, it would simply stay there. I worked on GM locomotives which have 20 cylinders each of 765 ci and two blowers so they were sized at 10/765. Later versions had turbochargers that had a clutch in them. At start up and low revs, the clutch was engaged so the turbo acted like a roots blower and and revs increased, the clutch disengaged and the turbo became a turbo.
You were right on the money with this extra Frieburger exept,engines dont make explosions (unless it fails). They make a combustion out of the fuel/air mixture hense inturnal combustion engine :-).
This is my dream car no doubt
Hey, based on your last Engine Masters video, you're gonna need some better air cleaners on that motor to make more power! Especially over those little donuts in there, and your back carb is probably starving for air! Still another enjoyable common man video, well done!
HA HA FRY BURGER Its the Best Looking!!! I agree 100%!!!
Power/torque is related the force pushing the piston down during the power stroke. Burning a fuel creates an increased amount of heat in the space where combustion occurs. According to Boyle's law, if you increase the heat of a gas without changing the volume, you increase the pressure. As the fuel/air is burned in the confined space of the combustion chamber the pressure goes up, and this increased pressure pushes the piston down the cylinder during the power stroke. If you are able to get more air/fuel into the combustion chamber space to be burned, the combustion event creates more heat, and therefore greater pressure to push against the piston during the power stroke. Supercharging works by increasing the volumetric efficiency of the engine, which is the ratio between the size of the cylinder and how much air/fuel is drawn into the cylinder into the cylinder during the intake stroke. More air/fuel in the cylinder -> more heat produced during combustion -> more pressure to push the piston during the power stroke.
Big difference between high compression and supercharge-turbo is pressurize intake manifold with cool air. This helps to control the combustion burning better. Specially by using intercool intake system. Where high compression engine, air and fuel gets heated and can cause uncontrollable combustion at compression stroke. Newer engines got GDI (gasoline direct injection) can control the combustion by changing injection time and spray frequency. Also combustion heats up only air at compression stroke which makes the combustion control much easier. Mazda coming out with engine which can run without spark under some condition in gasoline engine. This engine will use very high compression ratio. Will produce higher HP for litter and better economy.
Is it OK to have that blower belt loose like that? Don't hurt yourself Boyz!!! Big Respect...
I imagine that delt size goes up with blower size, right? My roommate has a Weiand 144 blower on a '79 Firebird, but the belt is an inch wide. My friends dad think it's fake because of its belt size.
okay you may think im extremely stupid for asking this but im a 16 year old classic owner and still learning. does anyone know if a engaging and disengaging is a thing for carbureted engines mad max style?
beautiful
USE MATH! 15psi boost doubles your displacement, cause atmosphere is already 15psi(a) a 5L engine @100% volumetric efficiency uses 5L of air @15psia, air at sea level is 15psi compared to a complete vacuum, if you double the pressure of atmosphere(15psi) you double displacement 15psi boost is 30psi(a) the a stands for absolute vacuum therefore 5L@15psi = 10L@0psi 10L@15psia = 5L@30psia you have to force twice as much air into an engine for it make 15psi boost
Anybody happen to have the link to the video where they put a blower on the stock 350 like he was talking about??
Frieburger only told half the story about why you want a high compression ratio, the other half is thermal efficiency. If you start with 1000 psi of pressure with 5:1 compression you're still left with 200 psi at the bottom of the power stroke. That 200 psi goes out the exhaust valve and never does any work. If you have 10:1 compression you're only left with 100 psi that goes to waste.
This exactly! I feel like if you want to have a meaningful conversation about the pros and cons of forced induction, you need to know the difference between gage and absolute pressure and at least know of the Carnot cycle
Should I be worried about pre ignition/ detonation if I installed a supercharger with 10.3:1 cr
So... what size blower would be good an a 351c?
It's increasing the effective amount of air and fuel and in effect making a bigger engine.
just the cool factor alone is what turns most people on to these blowers. I personally like turbos cause exhaust is a recycled by product to create more power unlike belt driven superchargers but it's all personal preference really.
Nothing like the sound of a blown motor at idle, some confuse it with camshaft rock.
I like this guy.
Since I don't have mtod myself, have you done a detailed video of an engine teardown/ rebuild yet?
Redneck Chevy funny u ask Freiburger and dulcich just finished a 16 part series on every little thing u could possibly ever need to know for building an engine starting with picking it up from the machine shop
724 Street Cars then I'm getting mtod. That is the useful information I'd pay for. Thanks
Except putting in the cam.
So what about the little supercharger that you coukd disengage with a push of a button? Would something like that be perfect for a turbo engine?
That's basically what modern Volvo engines do, only there's no button the computer controls everything.
18-71 is the largest produced today as I´m aware of. (DMPE)
dragsterdolme They made the 2 strokes in a 53,71,92 and 149 cubes per cyl. Biggest I’ve been around is a 20v-149, usually used on 1500-2000kw generators and other big shit like some trains. They stick a v6 block between 2 v8 blocks and voila , ya got a 20 cyl.
For cars, probably. The biggest Roots blower I know of comes on a 20 cyl GM engine (used in locomotives, I'm a railroad engineer) which has 756 ci/cyl and 2 blowers so each one is a 10-765.
MrTheHillfolk I am no doctor, but wouldn't 8+6+8=22? What am I missing? Are some cylinders "shared" between the blocks?
Why is roots least efficient supercharger can some one please explain and which type is the best?