turbo or super
 

as the title says, turbo or super charge? and why?

thanks all

There’s literally a million posts on this. It’s all subjective.


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Both because why not.
https://drivetribe.imgix.net/OBHyd-E...rop&crop=faces

Once again the only correct answer is “Yes”!

That's the reason we have two separate injection systems right?
One fore each form of FI.

If you want it to feel NA like you have a bigger displacement motor with more immediate response where you still have to rev it out then get a supercharger. A supercharger will also be more forgiving on the internals because there is less low end torque. There

If you want more drama, sound, efficiency, tuning control and low end torque then get a turbo.

With a centrifugal? YES.
With a Positive displacement? NO.
A PD blower will give that TQ from just about idle.

Also low end tq can be minimized or enhanced based on size of turbo (pulley for SC) and tuning (Wastegate for Turbo).

https://www.google.com/search?client...e-gws-wiz-serp

Here are the other 1000 threads on the same subject.

I voted turbo because I feel poll thread should be even.
https://encrypted-tbn0.gstatic.com/i...O1-9Q&usqp=CAU

At redline I hit a bar of boost (14 psi). At 3,750 I'm half that, so 7 psi. Half that at 1,875, and I am at 3.5 psi (a turbo could hit full boost by then). At half that at 950ish rpms (idle) I might be making 1-2 psi. Even a PD supercharger is RPM dependent instead of load dependent. Yes, a centrifugal supercharger will make even less low end torque, but any supercharger will still be safer in general. Safer because they aren't making as much low end torque, and I'll add that they are safer because there is no chance of over-boosting anywhere, but especially down low.

Supra dyno showing full torque at 2k
https://hips.hearstapps.com/hmg-prod...1559240377.png

Different torque curves, showing PD supercharger still building torque
http://www.ft86club.com/forums/attac...1&d=1445839471

Yes, a larger and slower spooling turbo will have less low end torque than a smaller turbo, and yes, a tuner could do boost by rpm to avoid low end torque and to ramp up boost. Someone could definitely design their torque profile to match a supercharger's torque profile. Most don't do that.

Turbo if you know what you’re doing and/or want the most whp to crank hp ratio.
Supercharger if you don’t known what you’re doing and/or don’t care about whp to crank hp ratio.

Also, do a turbo if you want to do boost-by-gear, boost-by-rpm, multiple boost maps, etc. It is also easier to run a turbo with FlexFuel/E85, especially when E85 is not always available; I would need to swap pulleys if I couldn't get E85 or drive around without going into boost or something, but a turbocharged car could just do boost-by-fuel by either limiting boost or just running a completely separate map. Finally, you can always swap to a different sized turbo or vary exhaust and compressor sizes if you are not happy with your turbo profile. You can swap superchargers too, but it isn't always as easy or an option. The JRSC has the C30 and C38, but the Edelbrock kit doesn't offer a different sized blower. It is typically much easier to option a turbocharger of your desire during an initial purchase, and it is easier to make a swap later--typically.

Seems like there is just overall less to go wrong with a SC vs turbo and they have greater consistency to throttle inputs as it is directly driven off the crank. :party0030:

Definitely less could go wrong. Worst case scenario is being stranded with a snapped belt. Throttle response is also more predictable, even if the power isn’t as good.

Another benefit of a turbo is more power at varying altitudes. A supercharger at altitude will achieve less psi at a given pulley size than at sea level, but the turbo will just suffer from more lag, but still hit full boost.

That's why I keep a spare belt in the car haha

Me too, and a spare socket and a long ratchet.

I decided JRSC 4 years ago, no regrets. I prefer increasing torque curve of Rotrex compressor. I think the high low-end torque is only good for casual driving and drag racing. I prefer not wasting gas and stressing the engine for grocery shopping. Power is there when I need it with just a downshift. The continuously increasing torque gives a much steeper power increase with rpm. Whole rpm range is useful, especially before the redline. There is no power plateau before the redline. The car feels like it will accelerate more if it can go over the redline. I need to downshift and upshift at the right moment, otherwise the engine let's me know what a sucker I am. I like the rewarding and punishing character of the JRSC engine just like a sports car needs to be.

Turbo, because it's flexible. You can build and tune your car to do nearly whatever you think is best.

You could somewhat replicate a turbo's boost-by-X tuning by running a wastegate on the intake tube with an electronic control or an electronic control on the internal bypass (if the blower is equipped) and smallest pulley for the upper limit of desired boost.

I haven't seen this in some years and I don't have the impression it was widely used, but back in the early/mid-oughtes when turbos were really starting to take over from superchargers in the 5.0 Mustang community, some SC users realized they could mimic the broad, linear powerband of a turbo by installing a small wastegate on the intake tube to dump excess psi. By targeting, say, 10 psi and running a 20 psi pulley, they could make 10 psi a couple thousand rpm lower in the torque curve and hold it through redline instead of making 10 psi near redline with a 10 psi pulley.

I'm aware, but the reason this is less common is because the supercharger is essentially over-spinning once the bypass is activated, which isn't good on fuel economy or on the life of the supercharger, and it produces a lot of extra heat. I also don't know if the bypass is large enough or if there would be some boost creep, but I doubt that is an issue. A turbo wouldn't have this issue because it would just not spin as much. For the Harrop kit, the smallest pulley is 65mm, which is around 18 psi. I think Harrop needed to use a larger crank pulley to achieve 20+ psi. Even then, the car is only making 10 psi at 4k, which a turbo could be far above that. Just saying.

I toyed with the idea of going FI. I ended up with a header and tune and it woke the car up and isn't putting a bunch of extra strain on the car overall. Going FI and flogging the car and you'll break things and it gets expensive. It's best to know what you're getting into. You'll find some guys that have had a decent experience and some with terrible experiences so it's a roll of the dice.

That only happens after a downshift without pushing the throttle. It is a useful *feature*, done on purpose for engine brake or entering a curve with high rev while aiming to exit accelerating. If sc is over-spinning continuously at constant speed, there is something wrong with either the valve spring adjustment or the driver is not shifting right.

You completely missed the context of the conversation. We were discussing the use of the bypass valve as a wastegate to bleed boost like turbos bleed exhaust, so someone could run a smaller pulley, but not hit high boost. Essentially they would bleed boost so boost would be flat instead of building with rpms. I was saying this means that if the supercharger is hitting 10 psi from 4-8k then it is spinning twice as much at 8k than at 4k while only producing 10 psi, so at 8k the engine is working harder creating more heat and is less efficient than it is at 4k. It is over-spinning while the bypass valve is open and bleeding/wasting boost. Turbos don’t waste boost, which is why they are much more efficient when doing boost-by-rpm/gear/map.

then it would just be easier to choke the inlet pipe with a restrictor.
It doesn't affect much under 5000 rpm but limits airflow capacity at high rpm

to reach a flatter boost curve like a PD supercharger or a turbo it would require such a small pulley that you ll overspin and break the impeller
Centrifugal sc anyway won't put out much boost at lower rpm even with a smaller pulley because it just won't spin enough

EDIT: and then after writing I remember that you actually don't have a centrifugal supercharger but the Harrop, sorry

Turbo's use similar recirculation valves in addition to wastegates. Sure, precisely designed turbo systems could omit the valve if the compressor can withstand the surge within design limits. Recirculation valve can also be omitted with a supercharger in the same way.

That overspin is not a disadvantage of supercharger. Actually it can be an advantage that eliminates the turbo lag. Plus, when the recirculation valve is open, supercharger's parasitic load on the engine becomes minimal since the superharger does not need to work against the back pressure of engine intake.

Volvo does it! And hell they throw in electric power also. [emoji1]


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It would be easier to choke the inlet, but that wouldn't really be the same as doing boost-by-rpm, boost-by-gear, multiple boost maps, etc, nor would it solve the inefficiency of over-spinning the blower, but it would create the effect of flattening the top end of the power band, so the car has a broader torque curve.

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.

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 I’m 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. :party0030: (not literally cause theyre hotter, much hotter) they go whoosh and stuff. I guess i like being punched in the face with power.:iono:

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:

https://www.boostaddict.com/images/i...12/graph-1.jpg

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.

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

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.

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. :bs: All that is done by adjusting pulley size and valve spring.

I’m aware of these, but I don’t know of anyone who has developed one for the 86, and from what I have seen, these don’t 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.

A supercharger is a disadvantage in ways, and it is an advantage in ways, especially for not breaking rods on stock blocks. The OP didn’t give specifics, so we don’t 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 wouldn’t 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 isn’t 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.

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)

Would it be possible to control the boost on a PD supercharger by using the BPV to recirculate the undesired boost back pre blower.

That’s 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.

But the load is not the same. So, heat, efficiency and wear will be less.

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).