why a turbo is better than a s/c
08-24-2004, 09:36 AM
#1
why a turbo is better than a s/c
Note: a lot of this info came from things I read at turbomustangs.com. Everything I said came from memory so I didn't do any copy and pasting bull ****. If you want to read their very, very well put together articles on turbo's and such check out that part of their site here: http://www.turbomustangs.com/turbotech/main.htm
Anything that didn't come off of that site came from personal experience and research.
Not sure if this has ever been put in to detail so if it has, sorry for the repost.
I just figured I'd post why a turbo is a much better unit for forced induction compared to any s/c's.
Reason 1:
A turbo is a lot more efficient than any supercharger. People often misunderstand what this means and claim that a turbo is free power. There is no such thing as "free power" when you are using one thing to power another. There will always be losses between the two... and if you ever figure out how to change that you'll either be the richest person in absolute existance or it would cause such a change that the entire world's economy would collapse in an instant...
Ok, back to the point. Since there are always going to be losses you want to get the lesser of the two evils. The turbo is the most efficient form of forced induction you can get, which is why people seem to think the powr is free. The reason it is more efficient is because it is using spent energy that has no use anywhere else at moving the car. Superchargers, on the otherhand, are using energy (power) that can be used at propelling the car forward (taking power away from the crank).
The amount of power taken away from the engine by a supercharger varies by the type and the amount of pressure you are creating. Centrifugal superchargers won't use as much power up as a roots because it isn't boosting near as much at the same rpm's plus there is a bit less weight to be turned. The roots s/c's take up quite a bit of power but can make some pretty good power as well. For instance, the top fuel draggers are using a roots setup that helps the engine produce its 4000 hp or whatever they're pulling these days. The only problem is, these roots superchargers are taking 400-500 hp from the engine to turn! That's an incredible amount of power loss.
A turbo would make the same power and not take up near as much power to do it. One problem is, we will never know how much power turbos are capable of on these cars nor the losses by the turbo since they have been banned from that type of race... stupid rules. Before they were banned (quite some time ago before all of this new turbo technology) a guy had a turbo setup and saw tons of potential but before he could fine tune the setup turbos got
.
Reason 2:
The amount of power turbos can add is absolutely incredible. The older F1 cars that had tiny 1.5 liter engines were turbocharged and were pulling.... 1500 hp... That's 1 hp per cubic centimeter and 1000 hp per liter! (eat that toyota
) Could you imagine that kind of power on an engine like ours...? 3000 hp! Its a far fetched claim but I have no doubts it could be done if a manufacturer wanted to.
Reason 3:
Space and weight consumption. Granted any forced induction setup will add quite a bit of weight. The weight and space will always vary depending on which route you take. What is nice about a turbo compared to a supercharger is that you don't always have to have it near the belts. You can put a turbo damn near anywhere since its not belt dependent. I've even seen turbos mounted in the back of a car under the body as I'm sure some of you have seen that as well. The superchargers always have to be accessible to the belts. If you don't have much space anywhere around the engine, you're not going to fit on on there without some crazy fabrication. A turbo you can stick damn near anywhere as long as you can get your exhaust pipe to it and such.
Depending on how your setup is the weight can always vary quite a bit. If you run a roots setup that is mounted straight to your intake you'll more than likely have the lowest weight consumption of the other forced induction units but of course you won't quite have the pwoer output abilities of the others due to intercooling and such.
The centrifugal s/c's will probably always be lighter than a turbo setup simly due to the lack of a turbine housing. Being cast iron, the turbine housings can get pretty dang heavy.
If you have to do a roots setup that is mounted elsewhere in the engine bay the turbo and s/c would end up being lighter and have less space consumption.
Reason 3:
The ease to get more power.
Say I'm boost at 10 psi with a turbo setup and what to boost some more. I reach over, press a few buttons on my boost controller, and now I'm boosting at 15 psi.
Someone else has a supercharger setup and wants to boost some more... no buttons, *****, or switches here. You have to shut the car off, open the hood, pull the old pulley and belt off of the s/c, put on the new pulley and belt, and now you're boosting some more. Lots of work to add just a few pounds of boost.
Reason 4:
Turbos have lag, that's a given. Most people claim the lag ruins everything about a turbo. These days lag is starting to disapear. With the introduction of ball bearing turbos and other nifty turbo setups they've been able to produce more power, and spool up even quicker.
A roots supercharger has near instantaneous boost and has full boost at that time to boot. They tend to gradually lose pressure in the top of the rpm range though.
A centrifugal supercharger is basically like a belt driven turbo. They are both centrifugal but one is being spun by exhaust and the other by a belt. Because of this, the centrifugal s/c doesn't reach maximum boost until redline. A turbo on the other hand can reach full boost way before redline since it isn't rpm dependent, only exhaust dependent. The amount of exhaust doesn't quite depend on the rpm's, only the amount of air and fuel being burnt.
Since the turbo will have full boost much earlier than the centrifugal s/c the power output will be much greater earlier in the rpm range than the s/c. Plus, when going down a track for instance the turbo will always have full boost while the s/c is still building up boost per the rpm since it can only spin as fast as the engine spins it.
The roots on the other hand will always have insane off-the-line power. It will have full boost off the line usually taking of a turbo and s/c setup. Where the cons appear is when the engine gets higher in the rpm's... where you are most of the time when racing. The roots s/c's tend to lose boost higher in the rpm's while the turbos are still making full boost up to redline and back to the rpm where it falls to when you upshift.
There are many more reasons why turbos are far superior to superchargers but these reasons should be enough to show why.
Have fun whichever route you take though!
Anything that didn't come off of that site came from personal experience and research.
Not sure if this has ever been put in to detail so if it has, sorry for the repost.
I just figured I'd post why a turbo is a much better unit for forced induction compared to any s/c's.
Reason 1:
A turbo is a lot more efficient than any supercharger. People often misunderstand what this means and claim that a turbo is free power. There is no such thing as "free power" when you are using one thing to power another. There will always be losses between the two... and if you ever figure out how to change that you'll either be the richest person in absolute existance or it would cause such a change that the entire world's economy would collapse in an instant...
Ok, back to the point. Since there are always going to be losses you want to get the lesser of the two evils. The turbo is the most efficient form of forced induction you can get, which is why people seem to think the powr is free. The reason it is more efficient is because it is using spent energy that has no use anywhere else at moving the car. Superchargers, on the otherhand, are using energy (power) that can be used at propelling the car forward (taking power away from the crank).
The amount of power taken away from the engine by a supercharger varies by the type and the amount of pressure you are creating. Centrifugal superchargers won't use as much power up as a roots because it isn't boosting near as much at the same rpm's plus there is a bit less weight to be turned. The roots s/c's take up quite a bit of power but can make some pretty good power as well. For instance, the top fuel draggers are using a roots setup that helps the engine produce its 4000 hp or whatever they're pulling these days. The only problem is, these roots superchargers are taking 400-500 hp from the engine to turn! That's an incredible amount of power loss.
A turbo would make the same power and not take up near as much power to do it. One problem is, we will never know how much power turbos are capable of on these cars nor the losses by the turbo since they have been banned from that type of race... stupid rules. Before they were banned (quite some time ago before all of this new turbo technology) a guy had a turbo setup and saw tons of potential but before he could fine tune the setup turbos got
.Reason 2:
The amount of power turbos can add is absolutely incredible. The older F1 cars that had tiny 1.5 liter engines were turbocharged and were pulling.... 1500 hp... That's 1 hp per cubic centimeter and 1000 hp per liter! (eat that toyota
) Could you imagine that kind of power on an engine like ours...? 3000 hp! Its a far fetched claim but I have no doubts it could be done if a manufacturer wanted to.Reason 3:
Space and weight consumption. Granted any forced induction setup will add quite a bit of weight. The weight and space will always vary depending on which route you take. What is nice about a turbo compared to a supercharger is that you don't always have to have it near the belts. You can put a turbo damn near anywhere since its not belt dependent. I've even seen turbos mounted in the back of a car under the body as I'm sure some of you have seen that as well. The superchargers always have to be accessible to the belts. If you don't have much space anywhere around the engine, you're not going to fit on on there without some crazy fabrication. A turbo you can stick damn near anywhere as long as you can get your exhaust pipe to it and such.
Depending on how your setup is the weight can always vary quite a bit. If you run a roots setup that is mounted straight to your intake you'll more than likely have the lowest weight consumption of the other forced induction units but of course you won't quite have the pwoer output abilities of the others due to intercooling and such.
The centrifugal s/c's will probably always be lighter than a turbo setup simly due to the lack of a turbine housing. Being cast iron, the turbine housings can get pretty dang heavy.
If you have to do a roots setup that is mounted elsewhere in the engine bay the turbo and s/c would end up being lighter and have less space consumption.
Reason 3:
The ease to get more power.
Say I'm boost at 10 psi with a turbo setup and what to boost some more. I reach over, press a few buttons on my boost controller, and now I'm boosting at 15 psi.
Someone else has a supercharger setup and wants to boost some more... no buttons, *****, or switches here. You have to shut the car off, open the hood, pull the old pulley and belt off of the s/c, put on the new pulley and belt, and now you're boosting some more. Lots of work to add just a few pounds of boost.
Reason 4:
Turbos have lag, that's a given. Most people claim the lag ruins everything about a turbo. These days lag is starting to disapear. With the introduction of ball bearing turbos and other nifty turbo setups they've been able to produce more power, and spool up even quicker.
A roots supercharger has near instantaneous boost and has full boost at that time to boot. They tend to gradually lose pressure in the top of the rpm range though.
A centrifugal supercharger is basically like a belt driven turbo. They are both centrifugal but one is being spun by exhaust and the other by a belt. Because of this, the centrifugal s/c doesn't reach maximum boost until redline. A turbo on the other hand can reach full boost way before redline since it isn't rpm dependent, only exhaust dependent. The amount of exhaust doesn't quite depend on the rpm's, only the amount of air and fuel being burnt.
Since the turbo will have full boost much earlier than the centrifugal s/c the power output will be much greater earlier in the rpm range than the s/c. Plus, when going down a track for instance the turbo will always have full boost while the s/c is still building up boost per the rpm since it can only spin as fast as the engine spins it.
The roots on the other hand will always have insane off-the-line power. It will have full boost off the line usually taking of a turbo and s/c setup. Where the cons appear is when the engine gets higher in the rpm's... where you are most of the time when racing. The roots s/c's tend to lose boost higher in the rpm's while the turbos are still making full boost up to redline and back to the rpm where it falls to when you upshift.
There are many more reasons why turbos are far superior to superchargers but these reasons should be enough to show why.
Have fun whichever route you take though!
08-24-2004, 10:45 AM
#2
Excellent summary.
One thing, though. I was gratified to see you state that power to drive a turbo isn't free, but then in the next paragraph you seem to reverse yourself and say that the power used to drive the turbo is "spent" power. Meaning, I guess, that it doesn't reduce the power made by the engine. But it does affect the engine somewhat in that the turbo presents a flow restriction in the exhaust system, and a certain amount of efficiency is lost due to increased back pressure between the cylinder and the turbine. The lost efficiency is much less than the power required to turn a supercharger, though, so turbos win over superchargers in that regard.
A question I have is whether it is really true that a turbo can produce full boost from low rpm all the way to redline. A turbo sized to reduce lag and produce good power at low rpm tends to run out of flow capacity at high rpm. That is why you see so many dynos of turbocharged vehicles with awesome torque but the power drops at high rpm. A turbocharger sized to bias power to the high rpm range results in decreased low end power and the dyno graph looks similar to a centrifugally supercharged engine, although it will still have more low end power than the SCed engine. This is just something I have observed based on my limited exposure to turbochargers, I don't claim to know much in this regard.
One thing, though. I was gratified to see you state that power to drive a turbo isn't free, but then in the next paragraph you seem to reverse yourself and say that the power used to drive the turbo is "spent" power. Meaning, I guess, that it doesn't reduce the power made by the engine. But it does affect the engine somewhat in that the turbo presents a flow restriction in the exhaust system, and a certain amount of efficiency is lost due to increased back pressure between the cylinder and the turbine. The lost efficiency is much less than the power required to turn a supercharger, though, so turbos win over superchargers in that regard.
A question I have is whether it is really true that a turbo can produce full boost from low rpm all the way to redline. A turbo sized to reduce lag and produce good power at low rpm tends to run out of flow capacity at high rpm. That is why you see so many dynos of turbocharged vehicles with awesome torque but the power drops at high rpm. A turbocharger sized to bias power to the high rpm range results in decreased low end power and the dyno graph looks similar to a centrifugally supercharged engine, although it will still have more low end power than the SCed engine. This is just something I have observed based on my limited exposure to turbochargers, I don't claim to know much in this regard.
08-24-2004, 12:28 PM
#3
Yeah, I understand what you're saying in the first paragraph. That is kind of hard to explain because in the end... they are both basically using the firing of the pistons to power them. What I mean is:
The power loss for the turbo should come from the pistons trying to "compress the exhaust" since there is back pressure in the manifolds. The momentum of the engine should help do this but there will be some power taken from the other pistons that are firing (a bit more restriction on them) and that should be where the power loss is coming from on a turbo. However, since the actual energy that is spinning the turbo is fuel/air that has already been used, that's where the "spent energy" thing comes from.
The s/c uses the current burning of fuel/air to spin it instead of fuel/air that has already been burnt. Basically like running your a/c. (maybe we can make a turbo a/c )
That is kind of a hard thing to explain but in the end, they both use power as no power is free but the turbo is more efficient.
With a lot of the new turbo technology I'm sure it is possible to have full boost throughout a good portion of your rev range. The ball bearing turbos allow spooling to occur much sooner therefore allowing larger the use of much larger wheels (fast spooling, high power). If you wanted to go real crazy on a turbo setup you could go with a variable vane turbine setup. Basically, with that kind of setup you could have a very large turbo setup with multiple turbine a/r's. It would be like running a T3/T4 with a .48 a/r on one of our engines. Incredibly fast spooling but once you start pulling some major power the small housing can't support the flow of exhaust. With the variable setup it would change the a/r to something that would handle the high power. That's the basics of that kind of turbo from what I've read. That would a far superior setup than anything on the market (super, triple, mega, teflon, ball bearing, nut busting, disco potato, turbo charger with the patented knight rider turbo boost)
Regular ball bearing setups don't do too bad though. The turbo I was looking at for my 280Z with the VH45DE should produce full boost by 3500 or so rpm (this engine has a 7000 rpm redline). The turbo is supposed to handle up to 1000 hp according to Garrett. (quick spool and lots of top end power). I'm speaking of a GT42R mated to the DOHC 4.5 liter V8 out of the Q45 btw.
The power loss for the turbo should come from the pistons trying to "compress the exhaust" since there is back pressure in the manifolds. The momentum of the engine should help do this but there will be some power taken from the other pistons that are firing (a bit more restriction on them) and that should be where the power loss is coming from on a turbo. However, since the actual energy that is spinning the turbo is fuel/air that has already been used, that's where the "spent energy" thing comes from.
The s/c uses the current burning of fuel/air to spin it instead of fuel/air that has already been burnt. Basically like running your a/c. (maybe we can make a turbo a/c
)That is kind of a hard thing to explain but in the end, they both use power as no power is free but the turbo is more efficient.
With a lot of the new turbo technology I'm sure it is possible to have full boost throughout a good portion of your rev range. The ball bearing turbos allow spooling to occur much sooner therefore allowing larger the use of much larger wheels (fast spooling, high power). If you wanted to go real crazy on a turbo setup you could go with a variable vane turbine setup. Basically, with that kind of setup you could have a very large turbo setup with multiple turbine a/r's. It would be like running a T3/T4 with a .48 a/r on one of our engines. Incredibly fast spooling but once you start pulling some major power the small housing can't support the flow of exhaust. With the variable setup it would change the a/r to something that would handle the high power. That's the basics of that kind of turbo from what I've read. That would a far superior setup than anything on the market (super, triple, mega, teflon, ball bearing, nut busting, disco potato, turbo charger with the patented knight rider turbo boost)
Regular ball bearing setups don't do too bad though. The turbo I was looking at for my 280Z with the VH45DE should produce full boost by 3500 or so rpm (this engine has a 7000 rpm redline). The turbo is supposed to handle up to 1000 hp according to Garrett. (quick spool and lots of top end power). I'm speaking of a GT42R mated to the DOHC 4.5 liter V8 out of the Q45 btw.
08-24-2004, 02:35 PM
#4
Originally Posted by Stephen Max
A question I have is whether it is really true that a turbo can produce full boost from low rpm all the way to redline. A turbo sized to reduce lag and produce good power at low rpm tends to run out of flow capacity at high rpm. That is why you see so many dynos of turbocharged vehicles with awesome torque but the power drops at high rpm. A turbocharger sized to bias power to the high rpm range results in decreased low end power and the dyno graph looks similar to a centrifugally supercharged engine, although it will still have more low end power than the SCed engine. This is just something I have observed based on my limited exposure to turbochargers, I don't claim to know much in this regard.
Well from my little knowledge, most of it is due to Volumetric Efficency/VE. Since the VE is highest at peak TQ, thanks for the refresher ben, your power is made there @ normally your peak PSI. Then as the PSI stays the same, your VE decreases and your HP drops.
I consider useable power ~4000 rpm. that's low rpm to me. You may consider ~3000rpm the low rpm.
That's my 2 cents
08-25-2004, 07:00 AM
#6
Not really, if you blow the turbo, the car will still drive. If you blow the SC belt, you have to ghetto rig it or you're stuck. If you blow anything on the piping side of a turbo, the car will still drive. If you lose an oil line...well that can happen with the SC too.
Originally Posted by meccanoble
well if there's one benefit with supercharger, its that if there's a problem its much easier to ghetto rig a setup to get yourself home with a supercharger vs a turbo.
08-25-2004, 08:40 AM
#7
I've lost a turbo before and was still able to make the 1 hour drive home. All I had to was disconnect the oil line as it was leaking oil pretty bad into the exhaust (almost got pulled over). I had to do some ghetto rigging but I made it. If it wasn't leaking oil (due to something I did directly to the turbo when trying to change it out) I would have been able to make it home without any ghetto rigging anything.
Thread
Thread Starter
Forum
Replies
Last Post
litch
4th Generation Maxima (1995-1999)
123
01-04-2024 07:01 PM
Keyno McMike
3rd Generation Maxima (1989-1994)
1
09-21-2015 07:18 AM