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Forced Induction Turbo, Supercharger, Methanol, Nitrous


View Poll Results: Turbocharger or Supercharger?
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Old 03-01-2021, 12:45 AM   #15
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Worst case scenario is being stranded with a snapped belt.
That's why I keep a spare belt in the car haha
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Old 03-01-2021, 02:13 AM   #16
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That's why I keep a spare belt in the car haha
Me too, and a spare socket and a long ratchet.
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Old 03-01-2021, 07:59 AM   #17
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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.
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Old 03-01-2021, 11:54 AM   #18
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Turbo, because it's flexible. You can build and tune your car to do nearly whatever you think is best.
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Old 03-01-2021, 12:59 PM   #19
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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.

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.
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Old 03-01-2021, 06:37 PM   #20
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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.
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Old 03-01-2021, 07:38 PM   #21
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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.
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Old 03-02-2021, 03:55 PM   #22
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Quote:
Originally Posted by Irace86.2.0 View Post
supercharger is essentially over-spinning once the bypass is activated
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.
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Old 03-02-2021, 04:37 PM   #23
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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 donít waste boost, which is why they are much more efficient when doing boost-by-rpm/gear/map.
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Old 03-02-2021, 05:25 PM   #24
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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
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Old 03-02-2021, 06:03 PM   #25
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Quote:
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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 donít waste boost, which is why they are much more efficient when doing boost-by-rpm/gear/map.
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.
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Old 03-02-2021, 06:47 PM   #26
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Both because why not.

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


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Old 03-02-2021, 09:05 PM   #27
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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
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.
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Old 03-02-2021, 09:41 PM   #28
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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.
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.
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