Behind the wheel difference between superchargers and turbos?
01-21-2014, 09:30 AM
#21
I suppose whether you are auto or manual makes a big different too. An auto will help with the lag a big.
being that my car will always be a manual I wish I could fit a roots but it would never fit. I'll probably just end up going procharger and tinker with the idea of a wastegate on it.
I have 317's and a forged rotating assembly on the way. Soon enough she'll have boost.
being that my car will always be a manual I wish I could fit a roots but it would never fit. I'll probably just end up going procharger and tinker with the idea of a wastegate on it.
I have 317's and a forged rotating assembly on the way. Soon enough she'll have boost.
01-21-2014, 09:42 AM
#22
Just look at the dynos... Here's mine. D1SC Procharger, ~17psi of boost, 347 cube motor.
As you can see, the power curve looks very similar to an NA motor in that the torque comes on gradually and builds. Personally, on the street, I feel this is ideal since it doesn't 'shock' the tires with an instant hit like a spooling turbo does. I personally feel like the procharger pulls longer and harder as the rpms go up, because it's obvious the torque curve does just that.
Like Fotoboy stated, for a manual trans, it's hard to beat the feel of a Procharger for instant power and responsiveness. There's no boost lag between shifts, and the power feels pretty linear to me.
FYI, my power dropped off slightly due to a boost leak above 15psi I was seeing. Once that's fixed, it should make a bit more hp than it does now. Typically, at these levels, you'll see roughly 100-150 more hp than torque.
As you can see, the power curve looks very similar to an NA motor in that the torque comes on gradually and builds. Personally, on the street, I feel this is ideal since it doesn't 'shock' the tires with an instant hit like a spooling turbo does. I personally feel like the procharger pulls longer and harder as the rpms go up, because it's obvious the torque curve does just that.
Like Fotoboy stated, for a manual trans, it's hard to beat the feel of a Procharger for instant power and responsiveness. There's no boost lag between shifts, and the power feels pretty linear to me.
FYI, my power dropped off slightly due to a boost leak above 15psi I was seeing. Once that's fixed, it should make a bit more hp than it does now. Typically, at these levels, you'll see roughly 100-150 more hp than torque.
01-21-2014, 10:01 AM
#23
What CR are you running? I'd like to get a good balance out of my motor without and water or meth injection on 93. Ideally I want to stay above 9:1 as it's almost entirely a street car.
Your numbers also make me feel good about not running something bigger than the D1SC. I was thinking about the F-1A as they are almost the same size but I want the helical gears.
Your numbers also make me feel good about not running something bigger than the D1SC. I was thinking about the F-1A as they are almost the same size but I want the helical gears.
01-21-2014, 10:17 AM
#24
CR I am ~10.3:1. I do run meth/water injection to add some safety factor into the mix. Timing on that run was only 16.5 degrees, which is very conservative, and my AFR was way too rich at 10.2-10.6. I had recently swapped injectors and pullies, so I was in the process of getting it tuned and felt it was safer to do on the dyno. Ran out of time, got 3 pulls in, but good data to finish tuning the car. I decided to pressure test my charge pipes and found the proflo wouldn't hold boost beyond 14-15psi and would leak past the butterfly valve.
Once everything is squared away, it'll be a solid 800hp/700tq street car.
Once everything is squared away, it'll be a solid 800hp/700tq street car.
01-21-2014, 11:40 AM
#25
Easily at those AFR's you definitely have more power in there not to mention the leak you might have. I think I'll go 9.5. Little more torque for the street as the peak number isn't what I'm chasing. Thanks for the info man. You've made my decision much easier.
01-21-2014, 12:45 PM
#26
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^^ The difficult part with a wastegate on a blower comes from efficiency ranges. The idea works for some setups but I would spend a ton of time studying compressor maps before spending money. The f1 is not going to be in its range turning half max speed at 3k rpms or one quarter of max impeller speed.
I do agree with the comment about the centrifugal being smooth. They have a very linear power curve. Turbo power curves can vary greatly depending on how they are sized. They can be anywhere between roots blower and supra power curves.
I do agree with the comment about the centrifugal being smooth. They have a very linear power curve. Turbo power curves can vary greatly depending on how they are sized. They can be anywhere between roots blower and supra power curves.
01-21-2014, 01:04 PM
#27
You don't over spin it. You use an oversized blower and spin it to max rpm at redline NOT over. But you bleed of boost so you don't blow the motor. Gives a lot more low end power.
Over spinning is someone that wants to get more out of what they already have.
Over spinning is someone that wants to get more out of what they already have.
01-21-2014, 02:32 PM
#31
Measurement of FI performance is manifold pressure. This is what crams more air:fuel into the cylinder and makes power.
With a blower, the amount of boost you get depends on the pulley size and rpm. A smaller pulley will spin the blower faster, and you get more boost. But once you've set it up, that's what you get at that rpm. So lets pick a number and say 10psi from the blower alone.
The boost pressure from the blower alone will rise according to the rpm. It's a set number, and won't change. You choose the pulley size for the maximum boost your engine can handle, at maximum rpm. Lets say your max boost at 7,000 rpm is 16. Which means at 3,500 rpm your boost will about 8 psi; you're not going to get max boost or max power. But, with a nice linear power curve based on RPM, superchargers are perfect for drag racing.
A turbo, OTOH, works very differently. The waste opens when boost levels get too high for your particular engine. And that's important, because boost is load dependent - and not rpm dependent. This is a key point. If you're tooling along at 2,500 rpm's and whack the throttle, boost goes to max (as controlled by the waste gate), which means that power goes to max. If you're climbing a big hill at 3,500 psi, you'll get max boost of 16psi. Already you can see the advantage over the belt driven blower. Turbos are much better suited to road racing. That's why Porsche uses them.
One of the big advantages to a turbo is it's performance at altitude. That's important to me because I live at 6,200' ASL. A road trip day could take me as low as 4,200' and as high as 11,000'; all in the same day.
A NA engine loses manifold pressure as the ambient air pressure drops (by increasing altitude). That means as you go up in altitude you lose power. You generally lose about 2-3% per thousand feet.
Since the belt driven blower is running at a fixed speed based on rpm, it will also lose manifold pressure at the same rate. As you pull a mountain pass at 3,500 rpm's, you boost is about 7psi. As you continue to climb, your boost pressure will continue to drop. At sea level, your belt driven supercharged engine makes 550hp. At 11,000' that same engine makes about 400hp; you've lost 25-30% of your power.
Ambient air pressure + boost pressure = manifold pressure.
A turbo is load dependent, and controlled by the waste gate. As you start climbing that mountain pass, the load goes up, and so does the boost. At 3,500 rpm's, you're at 16 pounds of boost if you need it. You're getting max power at 3,500 rpm's.
Additionally, you don't lose power for altitude. 16 pounds of boost means you're cramming a set amount of air:fuel into the cylinders. As the ambient air pressure drops, the waste gate opens later and maintains that 16 pounds of boost, regardless of ambient pressure. At sea level, your turbocharged engine makes 550 hp. At 11,000', that same engine makes 550hp.
A turbocharged engine will often get better mileage, too. Lets say you're driving south I-25 at 80mph, 2,500 rpm's. That's a gradual down hill drive for the most part. The belt driven supercharger is making, say, 6 pounds of boost simply because you're at 2,500 rpm's. To match that flow of air, you have to match that amount of fuel to maintain that perfect ratio.
A turbocharger will drop to near zero when there's no real load. As you're traveling the same rate, boost is close to zero. Pumping less air through the engine means you're pumping less fuel.
That's how the theory of the two systems works. In real life, it's not quite so black and white. You have to take in to account certain inefficiencies of mechanical systems, tuning differences, etc. In actuality, a turbocharger will lose some power at high altitude, but not much. And over the last decade or two the big differences have been narrowed a bit by technology. Especially with the Whipple and other screw-type supercharger and computer controls.
With a blower, the amount of boost you get depends on the pulley size and rpm. A smaller pulley will spin the blower faster, and you get more boost. But once you've set it up, that's what you get at that rpm. So lets pick a number and say 10psi from the blower alone.
The boost pressure from the blower alone will rise according to the rpm. It's a set number, and won't change. You choose the pulley size for the maximum boost your engine can handle, at maximum rpm. Lets say your max boost at 7,000 rpm is 16. Which means at 3,500 rpm your boost will about 8 psi; you're not going to get max boost or max power. But, with a nice linear power curve based on RPM, superchargers are perfect for drag racing.
A turbo, OTOH, works very differently. The waste opens when boost levels get too high for your particular engine. And that's important, because boost is load dependent - and not rpm dependent. This is a key point. If you're tooling along at 2,500 rpm's and whack the throttle, boost goes to max (as controlled by the waste gate), which means that power goes to max. If you're climbing a big hill at 3,500 psi, you'll get max boost of 16psi. Already you can see the advantage over the belt driven blower. Turbos are much better suited to road racing. That's why Porsche uses them.
One of the big advantages to a turbo is it's performance at altitude. That's important to me because I live at 6,200' ASL. A road trip day could take me as low as 4,200' and as high as 11,000'; all in the same day.
A NA engine loses manifold pressure as the ambient air pressure drops (by increasing altitude). That means as you go up in altitude you lose power. You generally lose about 2-3% per thousand feet.
Since the belt driven blower is running at a fixed speed based on rpm, it will also lose manifold pressure at the same rate. As you pull a mountain pass at 3,500 rpm's, you boost is about 7psi. As you continue to climb, your boost pressure will continue to drop. At sea level, your belt driven supercharged engine makes 550hp. At 11,000' that same engine makes about 400hp; you've lost 25-30% of your power.
Ambient air pressure + boost pressure = manifold pressure.
A turbo is load dependent, and controlled by the waste gate. As you start climbing that mountain pass, the load goes up, and so does the boost. At 3,500 rpm's, you're at 16 pounds of boost if you need it. You're getting max power at 3,500 rpm's.
Additionally, you don't lose power for altitude. 16 pounds of boost means you're cramming a set amount of air:fuel into the cylinders. As the ambient air pressure drops, the waste gate opens later and maintains that 16 pounds of boost, regardless of ambient pressure. At sea level, your turbocharged engine makes 550 hp. At 11,000', that same engine makes 550hp.
A turbocharged engine will often get better mileage, too. Lets say you're driving south I-25 at 80mph, 2,500 rpm's. That's a gradual down hill drive for the most part. The belt driven supercharger is making, say, 6 pounds of boost simply because you're at 2,500 rpm's. To match that flow of air, you have to match that amount of fuel to maintain that perfect ratio.
A turbocharger will drop to near zero when there's no real load. As you're traveling the same rate, boost is close to zero. Pumping less air through the engine means you're pumping less fuel.
That's how the theory of the two systems works. In real life, it's not quite so black and white. You have to take in to account certain inefficiencies of mechanical systems, tuning differences, etc. In actuality, a turbocharger will lose some power at high altitude, but not much. And over the last decade or two the big differences have been narrowed a bit by technology. Especially with the Whipple and other screw-type supercharger and computer controls.
01-21-2014, 02:45 PM
#32
Is this on a normal street radial with no sidewall? Put a 325/50/15 drag radial on it and it's a different story. My car spun everywhere on my 275/40/17's now it dead hooks and goes. You can't really say you have too much low end power if you are spinning on a street with a street tire.
01-21-2014, 02:53 PM
#33
If I had concerns about wild altitude changes I would consider a turbo much more heavily. It's not really an issue where I'm at though.
Also, at 2500 rpm cruising you are pulling vacuum. Therefore the blow off valve is open meaning the charger is really only using frictional load and not adding any air to the motor. This holds true for most tvs and whipple blowers as well due to the bypass valve. They usually use less than one hp at cruise rpm.
Also, at 2500 rpm cruising you are pulling vacuum. Therefore the blow off valve is open meaning the charger is really only using frictional load and not adding any air to the motor. This holds true for most tvs and whipple blowers as well due to the bypass valve. They usually use less than one hp at cruise rpm.
01-21-2014, 03:19 PM
#34
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I've only had a Centri and like it but I would love turbos but my wallet said no. In a vette, I don't need tons of torque down low to get moving. I like the power curve.
Stock LS6 with headers at 10#
Stock LS6 with headers at 10#
01-21-2014, 03:54 PM
#36
Is this on a normal street radial with no sidewall? Put a 325/50/15 drag radial on it and it's a different story. My car spun everywhere on my 275/40/17's now it dead hooks and goes. You can't really say you have too much low end power if you are spinning on a street with a street tire.
I was just trying to say that a huge hit of torque on the street isn't always a great thing.
Honestly, I am biased because I have a Procharger and love the setup. I've never driven a turbo'd ls1, so I don't know if I wouldn't like it more, but I will say that I love my current setup, other than having too short of a rear gear at this point. Having some 3.42s or even 3.23s would help with my traction issues. But I love the instant torque while rowing gears. My daily driver is a turbo'd 4 cylinder (I know, not the same) but there is a lag there when you roll into the throttle, even if it's for a split second, it's still there.
There are definitely some positives with modern turbo setups, but there's also more headaches and work to get them right, aka oil feed and returns, having hot side pipes crack or cause damage due to excessive heat, figuring out downpipe sizing as well as charge pipe setups properly, and let's not forget the complication of a/r ratios and cubic inches vs compression.
So for ease of setup, and overall simplicity, it's hard to beat a D1-F1 procharger with a front mount. Can you make more power, differently with a turbo, sure, but like I said, it's not that you make more power, you just make it differently.
I suggest people get rides in, and if they can, drive different setups first before you make a decision. Some people hate centri blower sounds, others, like myself, love them. Again, personal preference.
01-21-2014, 07:39 PM
#37
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Ehtyl's Big Black Whipple would rip the pavement right up on the road the instant you put your foot in it. Too wit
4.0 Liter Whipple 1100 ft lbs of Torque at 2000 RPM
Ethyl's Twin Turbos are smoother but the slight delay before they come into it scares the **** out of me.
4.0 Liter Whipple 1100 ft lbs of Torque at 2000 RPM
Ethyl's Twin Turbos are smoother but the slight delay before they come into it scares the **** out of me.
01-22-2014, 06:17 AM
#40
Is this on a normal street radial with no sidewall? Put a 325/50/15 drag radial on it and it's a different story. My car spun everywhere on my 275/40/17's now it dead hooks and goes. You can't really say you have too much low end power if you are spinning on a street with a street tire.