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Forced Induction Turbo, Supercharger, Methanol, Nitrous


View Poll Results: Turbocharger or Supercharger?
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Old 03-03-2021, 01:56 AM   #29
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Turbos cause they got that cooliness factor. But also with the cooliness comes with alot of negatives. There are alot more potential problems that could happen with them. The first one being things will get HOT. Installing them has alot more complexity because theyre are more parts to put on, meaning more things to break/leak/explode.

Superchargers are like having a bigger engine than you actually have. Torque at IDLING /s. But seriously torque from the get-go is pretty awesome. Installing, ive heard is simpler. Heat is there but not as much as a turbo. They say theres parasitic loss because its being powered by the engine itself but eh it puts out more power than whats being taken away so i never saw that as a huge negative. And you get instant noodle response on power.

Torque at low rpm is what breaks these engines. Looking at dyno sheets from both FI systems on our FA20 motors, it seems majority the of SC make more torque at low rpm than turbos. But having said that low end torque from the SC probably wont break the motor since it happens linearly/gradually/slower. A turbo, however, has a higher than to break things with low end torque. Turbos want to build power and punch you in face with it. It happens so quickly compared to a SC. Not slow. Plenty of turbos can have torque in the low rpm range but since its the FA20 motor Iím assuming its being tuned so all that power doesnt fully happen until higher rpm ranges. Low rpm range = 2500-3000ish at least to me.

But i still chose a turbo, cause its cooler. (not literally cause theyre hotter, much hotter) they go whoosh and stuff. I guess i like being punched in the face with power.
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Old 03-03-2021, 02:33 AM   #30
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It definitely depends on the size of the turbo. A bigger turbo will have greater turbo threshold and thus less low end power. In general, the turbocharged cars will still produce more torque per horsepower, so the 300hp turbo guys are typically producing much more torque. Partially this is because they aren't dealing with parasitic losses, so more torque gets put to the ground, and the other part is because the torque drops off and doesn't build to redline like a JRSC, for instance. Looking at this FA20F from a WRX, we see what a typical turbo application from the factory looks like. I would agree that more curves are shifted more to the higher rpm range:



The other factor is lugging the engine. This is never good, but with a supercharger, the rpms will just sit down low and provide whatever constant boost is at that rpm, so if someone was going 45 mph up a steep hill in 6th gear at 2.5k or whatever, the supercharger wouldn't be making much torque, so bad but not terrible. The turbo is more load dependent, which is why brake boosting is more effective than just revving the engine, so the turbo will typically build more boost/torque in the above scenario. Could be bad.
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Old 03-03-2021, 08:01 AM   #31
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Turbos cause they got that cooliness factor. But also with the cooliness comes with alot of negatives. There are alot more potential problems that could happen with them. The first one being things will get HOT. Installing them has alot more complexity because theyre are more parts to put on, meaning more things to break/leak/explode.
I would counter this by saying at least the parts can be services and replaced quickly/easily. Supercharger parts are terribly application unique. Nothing should leak if the installer is careful
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Old 03-03-2021, 10:45 AM   #32
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Originally Posted by Irace86.2.0 View Post
To raise the boost level on a supercharger, a smaller pulley has to be installed. Obviously this can't be done continuously
Google variable speed superchargers. Some manufacturers offer them for Mustangs, Cameros and Corvettes (and probably others as well). These have a small CVT between the driven pulley and the charger itself which is electronically controlled.

When reading your post I immediately thought of a simpler CVT arrangement between the existing pulleys, kinda like a Reeves drive on a mechanically variable speed drill press. Would be a fun experiment for someone mechanically inclined with cash to spare.
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Old 03-03-2021, 11:06 AM   #33
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Originally Posted by Irace86.2.0 View Post
Dude, this is really going over your head. I'm not talking about the existence of the bypass valve being bad; I know what it is there for and that it is good. Your talking about a separate thing. Pope and I were talking about replicating an electronic boost controller (EBC) on a supercharger system, so a supercharger could be controlled/tuned to do boost-by-gear, boost-by-rpm, multiple boost maps, etc.

For a turbo, this is easy. The EBC bleeds pressure off of the wastegate line, so the wastegate stays closed, which raises the boost beyond the wastegate spring--super simple and easy to control. To raise the boost level on a supercharger, a smaller pulley has to be installed. Obviously this can't be done continuously, so the only way to control boost the same way as the turbo in order to do boost-by-gear, etc is to install a small pulley, and then the tuner would have to use an EBC on the bypass valve pressure line to open the valve partly when someone is on-throttle to bleed off excess boost, so the driver can limit boost. This would mean the supercharger is being asked to work harder, but not produce more, so it is inherently inefficient in a way that generates heat and raises the parasitic load on the engine. The result would be a greater chance of heat soak for a given power output and less fuel economy and less power for a given amount of work. This is analogous to someone digging a hole at a fixed speed and someone throwing some of the dirt back in the hole, so the rate of the depth of the hole can be controlled, where a turbocharger just asks the digger to slow down or to speed up, which is much more efficient and easy.

The advantage the supercharger has over the turbo is that the turbo can't add any more boost down low if the turbo threshold hasn't been met, but the supercharger will add more boost down low with just a pulley change. A wastegate can add more boost to extend the power curve, but it can't make boost come on sooner like a supercharger can. In order to do that, a smaller turbo would be needed or other modifications would need to be done like restricting flow through the head, so pressures are higher/faster to spool the turbo faster or a ball bearing or twin scroll setup is utilized, but for the most part, people use turbo housing sizes to move the boost threshold up and down the rpm band, where a supercharger changes size in order to change the steepness of the power curve, which will result in progressively more boost at every rpm (typically), meaning more down low. While this is an advantage, a turbo will build boost so fast, that unless the turbo is large for the motor, the turbo will still out boost a supercharger.
Superchargers, especially centrifugal types, increase the boost with rpm; that is its advantage over turbo. Why would you implement a boost-by-rpm with a supercharger where it already works that way? Useless idea. All that discussion for nothing, unrelated to the original question anyway. All that is done by adjusting pulley size and valve spring.

Last edited by mrg666; 03-03-2021 at 11:32 AM.
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Old 03-03-2021, 01:04 PM   #34
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Originally Posted by Ohio Enthusiast View Post
Google variable speed superchargers. Some manufacturers offer them for Mustangs, Cameros and Corvettes (and probably others as well). These have a small CVT between the driven pulley and the charger itself which is electronically controlled.

When reading your post I immediately thought of a simpler CVT arrangement between the existing pulleys, kinda like a Reeves drive on a mechanically variable speed drill press. Would be a fun experiment for someone mechanically inclined with cash to spare.
Iím aware of these, but I donít know of anyone who has developed one for the 86, and from what I have seen, these donít drop right in to an existing space, so someone would need to make a custom setup. These are often bulkier, so packaging can be an issue. It is definitely a cool concept, and it would be a lot more efficient than over-spinning the supercharger.
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Old 03-03-2021, 05:25 PM   #35
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Originally Posted by mrg666 View Post
Superchargers, especially centrifugal types, increase the boost with rpm; that is its advantage over turbo. Why would you implement a boost-by-rpm with a supercharger where it already works that way? Useless idea. All that discussion for nothing, unrelated to the original question anyway. All that is done by adjusting pulley size and valve spring.
A supercharger is a disadvantage in ways, and it is an advantage in ways, especially for not breaking rods on stock blocks. The OP didnít give specifics, so we donít know if this is for him or a hypothetical. Regardless, it is worth being exhaustive.

Someone who was doing boost-by-gear would also likely want to do boost-by-rpm. Boost-by-gear is about limiting the boost ceiling in a particular gear, so 5 psi in 1st and 8 psi in 2nd and 17 psi in 3rd and 25 psi in 4th through 6th. Something like that. The turbo would still have the same torque profile, so if it could hit 25psi by 4k then it would still be hitting say 7 psi by say 1500 rpms, so someone may want to ramp up boost a little for first gear for traction.

On a supercharger, changing the pulley changes the max boost and the aggression/steepness of the torque profile, so it would make just as much sense to do the same. Yes, a centrifugal supercharger wouldnít need as much adjustments by rpm, but here is a sample for an unspecified supercharger: 4-6th gear is 20 psi by 8k, so 10 psi at 4k and 5psi at 2k. Maybe 5 psi will be the max desirable boost in 1st gear, but it would still hit by 2k, so maybe that would be too much. Someone could limit the slope so 5 psi is hit at redline in order maximize traction at WOT launches. Considering most stock cars will break loose if input isnít controlled, it would make sense that someone might want to do boost-by-rpm instead of just limiting boost to say 5 psi (boost-by-gear) and holding that from 2k to redline. Get it?

Again, this can be done, and it is done, but at a greater cost in heat generation, efficiency and supercharger wear.
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Old 03-03-2021, 09:59 PM   #36
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Having the max potential for less power at any rpm is never a positive. This is by no means a positive.

Plenty of ways to limit and turn down power if so desired, this can be done by how it’s setup, how it’s tuned, or how much throttle you give.
Turbos make less crank power at same whp vs supercharger. IE 300whp is roughly 345 crank on turbo vs 365 crank on supercharger from parasitic draw. Supercharger always add extra strain to the engine at any rpm/boost as it’s always spinning even if the boost is being bled or blowet ain’t spinning fast.

High torque, high load, low rpm snaps rods, so do any of the numerous things to turn down or limit boost down low, or on a PD blower if you want less torque use less throttle or detune it.

Centrifugals are great for tracking as they are fairly efficient, have decent heat management, and make good power at high rpm. For a daily a PD is better would you rather daily an NA flat 4 or an NA v6? PD blower turns the engine into an NA v6. Effortlessly get up to speed or pass people without downshifting and reving out. Have great power off the line and still make power top end.

A turbo can do any and all of that better if setup properly. The options for what can be done are limitless. Might be a little more difficult and expensive to do right and setup at first. But in the end will be better in just about every way. For a DD it isn’t unreasonably priced to setup, for tracking it does cost substantially more.

So for low budget track car centrifugal all day. For a DD if you can setup a turbo yourself properly or have the funds then turbo, if you aren’t up to the task a PD blower is the next best DD option.

In the end it comes down to budget, car use, and mechanical aptitude (what can/can’t you do on your own)
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Old 03-04-2021, 11:18 AM   #37
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Would it be possible to control the boost on a PD supercharger by using the BPV to recirculate the undesired boost back pre blower.
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Old 03-04-2021, 01:09 PM   #38
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Would it be possible to control the boost on a PD supercharger by using the BPV to recirculate the undesired boost back pre blower.
Thatís what we have been discussing the last two pages. It means the supercharger is over-spinning wastefully leading to excess heat, poor efficiency and greater supercharger wear.
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Old 03-05-2021, 10:10 AM   #39
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But the load is not the same. So, heat, efficiency and wear will be less.
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Old 03-05-2021, 02:14 PM   #40
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Thatís what we have been discussing the last two pages. It means the supercharger is over-spinning wastefully leading to excess heat, poor efficiency and greater supercharger wear.
I've been pondering this for quite a while now, but thinking of the positive displacement supercharger set ups that are available for the twins:

What if one could reduce the parasitic load on the engine that the supercharger draws, to almost nothing as engine RPM's increase, by installing an exhaust-driven turbine in addition to the suoercharger, which spins a gearbox, which then spins a pulley to drive a belt that spins an overrunning clutch pulley, which is mounted to the supercharger's drive pulley?

In theory, at low engine RPM's, the supercharger would be providing the immediate low-end boost and as the RPM's increase, the turbine gradually spins up and takes over the torque demand of the supercharger.

The key part would be the overrunning clutch pulley to allow the engine driven belt for the supercharger to initially spin the supercharger's drive shaft, and then as the turbine and its gearbox gradually takes over, the turbine assembly's belt would take over, spinning the supercharger's drive shaft, but just BARELY faster than the engine's serpentine belt would at top RPM.

Something like this:
Name:  Screenshot_20210305-131613~2.png
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which can be found here:

https://www.hilliardcorp.com/overrunning-clutches/

This set up could again, in theory, eliminate the parasitic draw of the supercharger, increasing available torque to the drive train.

Basically, this is a turbine-driven, positive displacement (this could even be applied to a centrifugal) supercharger with little to no parasitic loss to the engine, combining the two best advantages of both a supercharger 1) immediate low-end boost from the engine, and a turbocharger 2) free horsepower and torque from the exhaust gasses.

This is not twincharging, as the intake air is not compressed in two separate stages.

The only disadvantages of this set up that I can think of would be 1) slightly more weight, which would be immediately negated by greater available drive train torque, 2) higher under-hood temperatures, which can be dealt with as one would normally do with a turbo set up, and 3) a slightly more complex set up.

I think this is totally do-able with the right parts, which are already available, and by a persistent and innovative individual (with obviously deep pockets).
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Old 03-05-2021, 02:18 PM   #41
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I've been pondering this for quite a while now, but thinking of the positive displacement supercharger set ups that are available for the twins:

What if one could reduce the parasitic load on the engine that the supercharger draws, to almost nothing as engine RPM's increase, by installing an exhaust-driven turbine in addition to the suoercharger, which spins a gearbox, which then spins a pulley to drive a belt that spins an overrunning clutch pulley, which is mounted to the supercharger's drive pulley?

In theory, at low engine RPM's, the supercharger would be providing the immediate low-end boost and as the RPM's increase, the turbine gradually spins up and takes over the torque demand of the supercharger.

The key part would be the overrunning clutch pulley to allow the engine driven belt for the supercharger to initially spin the supercharger's drive shaft, and then as the turbine and its gearbox gradually takes over, the turbine assembly's belt would take over, spinning the supercharger's drive shaft, but just BARELY faster than the engine's serpentine belt would at top RPM.

Something like this:
Attachment 198062

which can be found here:

https://www.hilliardcorp.com/overrunning-clutches/

This set up could again, in theory, eliminate the parasitic draw of the supercharger, increasing available torque to the drive train.

Basically, this is a turbine-driven, positive displacement (this could even be applied to a centrifugal) supercharger with little to no parasitic loss to the engine, combining the two best advantages of both a supercharger 1) immediate low-end boost from the engine, and a turbocharger 2) free horsepower and torque from the exhaust gasses.

This is not twincharging, as the intake air is not compressed in two separate stages.

The only disadvantages of this set up that I can think of would be 1) slightly more weight, which would be immediately negated by greater available drive train torque, 2) higher under-hood temperatures, which can be dealt with as one would normally do with a turbo set up, and 3) a slightly more complex set up.

I think this is totally do-able with the right parts, which are already available, and by a persistent and innovative individual (with obviously deep pockets).
Do it! Be an innovator and pave the way. That sounds pretty cool in theory.
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Old 03-05-2021, 02:37 PM   #42
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But the load is not the same. So, heat, efficiency and wear will be less.
Yes, the load will be less at 10 psi with the valve bleeding boost at 20k rpms than the load at 20 psi of boost at 20k rpms, but still greater than the load at 10 psi of boost at 10k rpms. This isn't an object spinning in the vacuum of space. There will be drag created by spinning the supercharger at 10k rpms beyond what is necessary. The drag will be from the bearings, from the interface of the rotors, from the air resistance, NVH, etc. Since a twin screw supercharger is always compressing air and not just pumping air like a roots supercharger, there were be the resistance of compressing air. Once the air is compressed, the boost would be vented, so there wouldn't be extra resistance from pressure building in the manifold, but compressing the air initially would be that much more wasteful and parasitic. There is no way around doing more work and wasting that work, and it not being more parasitic/wasteful.
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