z34_nut Posted July 7, 2005 Report Share Posted July 7, 2005 They have always been a mystery to me (not fully), but I still have no grasp on how to create the system, or what it takes to make a turbo set up. Its the opposite with superchargers. I understand those 100%. But I mean, Does any-one know of a good link that describes a turbo system, advantages, disdvantages, turbines, intercooling, wastegate, BOV, piping, and exhaust? I mean, I just don't understand why they run so much more pressure vs. a supercharger. Why can it make so much more PSI then a supercharger, and not make the engine ignite? I dunno, theres a million questions, but I was hoping some-one would have a link that helps answer some of my questions. Quote Link to comment Share on other sites More sharing options...
sl3196 Posted July 7, 2005 Report Share Posted July 7, 2005 http://auto.howstuffworks.com/turbo.htm http://auto.howstuffworks.com/question122.htm Some good info in there. Quote Link to comment Share on other sites More sharing options...
z34_nut Posted July 7, 2005 Author Report Share Posted July 7, 2005 Thanks for the links, I read it and understand a little bit more now. But twin turbo vs on large turbo, what would work better? smaller turbo's create less inertia, while the big turbo goes for the long run. Could you mix sizes of turbos, one big and one small? the small one boosting low end, then the big one carrying out for the top end? I suppose if you didn't balance the two near perfectly, the little one could overrev, but couldn't it also help get the big turbo spooling faster because its creating more pressure in teh exhaust? Quote Link to comment Share on other sites More sharing options...
slick Posted July 7, 2005 Report Share Posted July 7, 2005 Could you mix sizes of turbos, one big and one small? the small one boosting low end, then the big one carrying out for the top end? I suppose if you didn't balance the two near perfectly, the little one could overrev, but couldn't it also help get the big turbo spooling faster because its creating more pressure in teh exhaust? Thats why you have the TT cars out there from the factory, to have boost at all times. Suprising as it may sound, the major upgrade is a larger single turbo. In this kit, I am assuming(not totally for sure) that it includes pistons that would increase the compression ratio some, so there will still be some low end kick, then once the larger turbo kicks in, it's all out balls from there. Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 7, 2005 Report Share Posted July 7, 2005 They have always been a mystery to me (not fully), but I still have no grasp on how to create the system, or what it takes to make a turbo set up. Its the opposite with superchargers. I understand those 100%. But I mean, Does any-one know of a good link that describes a turbo system, advantages, disdvantages, turbines, intercooling, wastegate, BOV, piping, and exhaust? I mean, I just don't understand why they run so much more pressure vs. a supercharger. Why can it make so much more PSI then a supercharger, and not make the engine ignite? I dunno, theres a million questions, but I was hoping some-one would have a link that helps answer some of my questions. well a turbocharger has two basic parts - the turbine and the compressor. everything starts with the turbine. exhaust gas is collected from all of the cylinders and enters the turbine side of the turbo tangently and exits axially. the exhaust gas hits the impellar wheel inside of the turbine housing causing it to spin very quickly. the shaft is connected to the compressor side, so it spins the compressor wheel at the same speed. this causes air to get sucked into the compressor side. anyways, after the exhaust gas goes through the turbine, it gets dumped into the downpipe. some of the exhaust gas exits through the wastegate, which is how boost pressure is regulated. IOW, when exhaust gas goes through the wastegate it isn't used to spin the turbine wheel therefore boost pressure doesn't keep rising. the wastegate is controlled by a boost controller, which may be controlled pneumatically or electronically. a boost controller tells the wastegate when to open. there are internal and external wastegates, but their job is the same. now with the compressor side, air enters the compressor axially after (going through an air filter) and then exits tangentially and out through the compressor discharge. as the air goes thru the compressor, it is moving so fast and then slowed down through the scroll which creates pressure (and heat). after the air leaves the compressor, it goes to either the throttle body and into the engine or it goes through an intercooler first. the intercooler is basically a radiator for the air. since the air gets heated up alot after it gets compressed, it is definately a good idea to have an intercooler. cooling the air causes it to become more dense, which means more power can be created at the same boost level. there are air-to-air intercoolers (most common) and water-to-air intercoolers like the Sy/Ty uses. their job is the same though. there is also chemical intercooling, such as adding water or alcohol injection. even nitrous is basically chemical intercooling. some people also spray CO2 at the intercooler to make it more efficient. the downside of an intercooler is pressure-drop through the intercooler. losing 1-2psi through the intercooler is common. a BOV is just a valve that opens after the throttle body blade shuts. it is controlled by a vacuum line on the other side of the TB blade (plenum side). when the TB blade shuts, the BOV sees the pressure diffrential between both sides of the TB blade. IOW, there is pressure in the charge pipes but no pressure in the intake. basically after the TB shuts the compressed air has nowhere to go which creates a pressure wave that sends alot of energy back to the compressor wheel. this slows the turbo down FAST and can hurt the bearings in the turbocharger's center section. the main purpose of a BOV is to prolong the life of the turbo. it also helps keep the turbo spooled between shifts (since it doesn't slow down so fast without the pressure wave coming back at it) and of course it sounds cool too! Quote Link to comment Share on other sites More sharing options...
1990lumina Posted July 7, 2005 Report Share Posted July 7, 2005 very good explanation Josh Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 7, 2005 Report Share Posted July 7, 2005 I mean, I just don't understand why they run so much more pressure vs. a supercharger. Why can it make so much more PSI then a supercharger, and not make the engine ignite? that's easy. first, the supercharger is belt driven and boost pressure increases as RPM increases. that's of course why people put smaller pulleys on superchargers - so it spins faster creating more boost at the same RPM. a turbo is different though. not only is it typically MUCH more efficient than a supercharger (meaning it doesn't heat up the air as much when compressing air to the same boost level), but more importantly boost doesn't increase with RPM. boost increases with engine load since exhaust gas is what spins it. for example, you could be at a VERY low RPM and still get high boost. drop down to 3rd gear at 20mph and mash the gas - boost level is almost certain to peak even though RPM is extremely low. it's also much easier to increase boost with a turbo, since you don't have to swap pulleys....just adjust your boost controller whether the engine can handle it or not is a different story altogther. Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted July 7, 2005 Report Share Posted July 7, 2005 think of a turbocharger as a supercharger ... superchargers are driven directly from the engine by using a belt to spin the rotors/twin-screws/centerfugal fan - a turbocharger works indirectly from the engine using the movement of exhaust gasses and the heat and expansion of the gasses to spin a turbine which is connected to a shaft to spin the centerfugal fan on the opposite side of the turbocharger. Turbochargers are prone to head-soak more then superchargers are, which is why they are usually cooled with oil, AND with coolant, some of the older turbochargers use only oil (like the one in my mustang) as technology advances turbochargers have been made to handle greater and greater speeds allowing a smaller unit to produce as much airflow as some of the older bigger units which often ran slower and were more prone to "boost lag" a downside of having a turbocharger setup. I hope that helps some. stupid fact #1: most turbochargers can and at times do spin greater then 100,000 RPM's. stupid fact #2: part of the noise from a turbocharger (only a very small small part) is the audible sound of the turbocharger blades breaking the speed of sound. --Dave. Quote Link to comment Share on other sites More sharing options...
z34_nut Posted July 7, 2005 Author Report Share Posted July 7, 2005 This is some GREAT information. Thanks a ton Josh and Dave. Those explainations helped alot. I accually feel like I learned some-thing today. This should be made into a sticky in the performance section I have a question how-ever. Considering the different types of Intercoolers, Which is the most efficient. What accually uses a Sequential Turbo set-up? I don't think I have ever noticed, unless it is commen for a TT set-up. Why would one big turbo be better then a TT set-up? If a TT set-up is sequential, wouldn't it go hand in hand with the fact that it would be more efficent then one big turbo? Thats all for now, I'll prolly try and squeeze as much info out of you guys. Quote Link to comment Share on other sites More sharing options...
ShockTherapy Posted July 7, 2005 Report Share Posted July 7, 2005 This is some GREAT information. Thanks a ton Josh and Dave. Those explainations helped alot. I accually feel like I learned some-thing today. This should be made into a sticky in the performance section I have a question how-ever. Considering the different types of Intercoolers, Which is the most efficient. What accually uses a Sequential Turbo set-up? I don't think I have ever noticed, unless it is commen for a TT set-up. Why would one big turbo be better then a TT set-up? If a TT set-up is sequential, wouldn't it go hand in hand with the fact that it would be more efficent then one big turbo? Thats all for now, I'll prolly try and squeeze as much info out of you guys. Front mount, 3KgtVR4,less complicated, and less pressure loss, no. Quote Link to comment Share on other sites More sharing options...
AWeb80 Posted July 7, 2005 Report Share Posted July 7, 2005 VW is looking at putting a supercharged and turbocharged motor in some upcoming cars.....i just read it in motor trend i think. Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 7, 2005 Report Share Posted July 7, 2005 A (inline) Twin turbo setup is used on some diesels and Alot of the tractor pullers some rin as high as 100psi boost basically a large Turbo compresses a large amount of air to 2-40psi and then a smaller turbo behind it compresses it further to 80+ psi and diesels as you know run upwards of 16 to 1 compressions so in effect that engine has at WOT close to 40 to 1 compression that is why them tractor pullers make 1000's of HP but Make 4000+ Lb Ft of tq that drags that big ass sled down the dirt track! the twin turbo Rx7's have a small and large turbo the small turbo provides boost at lower rpm's then the system switches over to the larger turbo at high Rpm's (where the small turbo would be a restriction) creating the best drivability for a factory car produced for the public. but the biggest Mod on these cars is upgrading to a single Large Turbo for more top end power. and the tuners tune the turbo lag so the engine makes as much power as it can without the tires breaking loose at the line. plenty of turbo cars tune the lag to keep traction off the line and fullboost not too far past the 60 ft mark... Turbo's you can control this with dual/tripple stage boost controllers that limit boost in 1st gear and then bump it up in 2nd then full bore it in 3rd gear+ to keep the driveline components happy and alive as well as to prevent tire spin (which just slows ya down) <---LOVE'S TURBO'S!!!!!!!!! and another design of IC (intercoolers) uses an Air to Freon system where the AC compressor (shuts off at WOT) works to compress refrigerant that is passed through an evaporator (very similar to the air to water IC's) that the Turbo outlet air moves through, chilling it down to ambient or below ambient air temps. some of these systems pass through an Air to air then through an air to Freon ICoolers seen more than a couple out in cali we will be using an air to freon IC on the rear 3800 when it gets Turbocharged this winter BTW Ford has a factory air to Freon IC on the newer Lightning trucks (factory supercharged) james Quote Link to comment Share on other sites More sharing options...
z34_nut Posted July 7, 2005 Author Report Share Posted July 7, 2005 tuners tune the turbo lag so the engine makes as much power as it can without the tires breaking loose at the line. plenty of turbo cars tune the lag to keep traction off the line and fullboost not too far past the 60 ft mark... thats very cool, never considered that. as is this, Turbo's you can control this with dual/tripple stage boost controllers that limit boost in 1st gear and then bump it up in 2nd then full bore it in 3rd gear+ to keep the driveline components happy and alive as well as to prevent tire spin (which just slows ya down) Now about Knock retard. Its a serious probelm with GTP's once they go into the smaller pully's and stock exhuast. But if a turbo is creating say 10 lbs of boost, then the pressure with-in the intake would be higher, along with compression. pressure creates heat, and heat will create knock. But I see cars running around with a turbo, stock manifolds but 10-15lbs of boost with little or no knock. What gives? How can a car have pressure built up in the combustion chambers (or so I think) yet avoid the knock with stock manifolds and compression? Does the turbo create a vaccum in the exhuast due to the turbine? Is that even possible? Or does the turbo operate solely on the manifold backpressure? Quote Link to comment Share on other sites More sharing options...
Prospeeder Posted July 7, 2005 Report Share Posted July 7, 2005 well knock is when the gas ignites because of pressure before its supose to, not by the spark? well if so, they use higher octane fuel, that makes it withstand more pressure Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 7, 2005 Report Share Posted July 7, 2005 Now about Knock retard. Its a serious probelm with GTP's once they go into the smaller pully's and stock exhuast. But if a turbo is creating say 10 lbs of boost, then the pressure with-in the intake would be higher, along with compression. pressure creates heat, and heat will create knock. But I see cars running around with a turbo, stock manifolds but 10-15lbs of boost with little or no knock. What gives? How can a car have pressure built up in the combustion chambers (or so I think) yet avoid the knock with stock manifolds and compression? Does the turbo create a vaccum in the exhuast due to the turbine? Is that even possible? Or does the turbo operate solely on the manifold backpressure? a roots typr SC is a fairly ineficient means of compressing air which means that to increase the boost it heats up the comprewssed air more per PSI than a turbo, a more efficient SC is the whipple design as it actually compresses the air as it goes through it (the SC) the roots type just "blows"=moves more air than the engine can injest which presurizes the air in the intake a turbo (or belt driven centrifugal) dep on the compressor design can move more air and compress it without increasing it's outlet air temp per PSI as much as a roots SC and sice a turbo (usually) has lag when the engine is under the most load at lower rpm's the boost level isnt high enough to cause KR but when the engine revs up it has less load on it (dep on trans/diff gearing) so everything is happening at a much faster rate and there is very little time for the mixture to preignite (most of the Top Fuel engines actually live under controlled detonation-thats why pistons rods etc get changed every 1-4 runs, that an ~8000Hp doesnt let components live that long...) and yes exhaust restriction factors into the equasion but there are many variables that come into play with non IC turbocharged cars... an excellent book is "Maximum Boost" by Corky Bell (amazon.com etc) this will give you an idea of the math, and fluid dynamics involved in turbocharging a vehicle properly.... cam profiles, head flow all play into the total system design...and aas with most things mechanical there is a bit of compromise...street drivability or maximum HP.... the turbo doesnot create a vacum on the exhaust..the turbo is using the hot expanding gasses (which is wasted energy on an NA engine) to turn the turbine, a properly tuned Turbo system will have a bit of backpressor if the turbine is sized for the engines VE and airflow requirments a turbo with too much backpressure is not an efficient turbo system... I highly rec the book i stated earlier as it can answer ALL of your questions.... James Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 7, 2005 Report Share Posted July 7, 2005 Octane is the measurment of a fuels resistance to ignition... it doesnt make the fuel burn slower (on higher quality fuels) but yes this contributes to knock resistance on both turbocharged and SC engine's... but so does combustion chamber/piston face design....as well as if the chambers have any carbon buildup.... Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted July 7, 2005 Report Share Posted July 7, 2005 an other way to reduce knock in an engine that's "charged" (supercharged or turbocharged) is to lower the static compression ratio, remember, if you're charging the air or forcing it into the engine you're basically making the engine think* it's bigger (for lack of a better way to put it) which will raise the compression ratio (can't remember the word for it when it's in motion, I wanna say dynamic compression ratio, but that doesn't sound right) as for twin turbo setups, sometimes two small turbos are used to move more air at lower engine speeds, this works, but the smaller turbos will generate more heat then one large turbo. the two vehicles that come to mind when thinking about sequential twin turbos are the Toyota Supra's and the RX7's both use the sequential turbochargers, one small one for slow speeds and one large one for higher engine RPM's with the smaller turbos doing almost nothing, the coolest thing about this setup is hearing the "pre-spool" stage of the second larger turbo - those setups do not have one turbo feeding into the other like someone else said (altho there are setups like that usually in tractor pulls and other type of highly modified engines) the downside to the seq. turbo setup is sequence timing is very important, pre-spool is extremely important, and keeping those things together is a hard accomplishment. Also, the two turbos together will hold a LOT more heat near the engine. if I think of anything more about them later I'll post that. --Dave. Quote Link to comment Share on other sites More sharing options...
z34_nut Posted July 7, 2005 Author Report Share Posted July 7, 2005 Maximum boost was only $23 at amazon.com. i'm going to try my local bookstore first. I just hate shipping. Quote Link to comment Share on other sites More sharing options...
Canada Posted July 8, 2005 Report Share Posted July 8, 2005 In all honesty, I wouldn't both reading about turbocharging on the internet. Awhile back I bought a book. Maximum Boost by Corky Bell. He is a very good technical writer and actually knows what he is doing. The book isn't written for the engineer (which is nice) and he sort of wrote his view of certain aspects into. Do it. Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 8, 2005 Report Share Posted July 8, 2005 i need to get that book! Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 8, 2005 Report Share Posted July 8, 2005 It's a great book, mine's getting old though.... BTW I just found a new Turbine housing design with a segmented housing design and a swing valve that closes at low speed for faster spoolup and swings open for maximum exhaust gas flow to the turbine....found it mentioned in a 4x4 mag fairly pricy though but it gets rid of one of the hardest compromizes...lag and overal flow.... Quote Link to comment Share on other sites More sharing options...
Canada Posted July 8, 2005 Report Share Posted July 8, 2005 Thats why I like VNTs.....like on the LLY Duramax. Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 8, 2005 Report Share Posted July 8, 2005 Ah but long term the VNT Turbo has issues with the vane controller components (the older Mopar's) the new one's have modern materials and engineering.... but the design i just saw has one moving part vs 18-30 .... yes VNT's are great... but as the saying goes, ..yeah i can make you go fast.....how big is yur wallet? Quote Link to comment Share on other sites More sharing options...
88Regal Limited Posted July 9, 2005 Report Share Posted July 9, 2005 Damn you guys know alot! Good information! Stupid question: Could you turbocharge a supercharged engine? or would that create too mutch heat and effectively melt the pistons in the motor? PS: when did you guys decide to make this section? :oops: Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted July 9, 2005 Report Share Posted July 9, 2005 It has nothing to do with the heat, it has more to do with the fact that the supercharger would just more resistance than it would help. You've got two moving lobes (or screws depending on the supercharger), they'd do nothing but in the way of the air the turbo is trying to push. You could do it, it'd just be incredibly stupid and a waste of time. Quote Link to comment Share on other sites More sharing options...
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