Twincharged NB Miata
07-21-2020, 03:40 AM
#21
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Join Date: Jun 2020
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Hang on a minute....
Is the supercharger blowing into the turbo ?
Its rather difficult to see where that pipework all goes from just the pictures, and no written explanation of what it all does.
That is definitely not going to work, it cannot work, unless you are VW, and your goals are fuel economy and emissions, not performance.
The supercharger passes a (sort of) fixed volume of air per revolution. It acts like a metering pump controlling and limiting the amount of air going into the engine. Feeding that into a turbo is going to do nothing except reduce the supercharger discharge pressure once the turbo starts spooling. The supercharger then throttles the air into the turbo.
A less than clever way around that is to bypass the blower. Then you have just an ordinary turbo engine without any compounding, and with the high turbine exhaust back pressure, and the turbo doing all of the work.
All turbo people quickly learn that a bigger turbine (or turbine housing) with reduced exhaust back pressure makes more power. Why is that ?
The answer is that exhaust back pressure kills power, and its especially worse if exhaust pressure is higher than boost pressure as it often is.
A much smarter way to do this is to add a positive displacement supercharger after the turbo.
That increases boost, while also slightly lowering exhaust back pressure.
You get the massive power increase, without having to have the typical big turbo high boost threshold, and the dreadful big turbo lag.
What needs to happen is the supercharger feeds air directly into the engine in the normal "supercharged engine" way, effectively multiplying the capacity of the engine with the larger swept capacity of the supercharger.
The turbo then blows air into the supercharger intake, filling the rotors with more dense air.
Thus supercharging the supercharger with more dense air if you like to think of it that way.
That is where the compounding comes in. The pressure ratios straight out multiply.
What makes compounding so powerful, is that the final induction pressure is always going to be so much higher than the final exhaust back pressure the engine sees.
That is quite difficult to do with just a turbo by itself, even a very big turbo.
With the turbo blowing into a supercharger, you get the excellent cylinder filling and excellent exhaust scavenging, and resistance to detonation if you can get rid of the hot exhaust residuals, while the turbo provides the very high power producing airflow at high engine revs where the Ve of both the supercharger and engine may both be rapidly falling.
You get the advantages of both supercharger and turbo, without the disadvantages either.
It should spool like a crazy thing if you do this the right way.
In fact your turbo may actually be a bit small !
The turbine gets ALL of the exhaust energy to work from, but the turbo compressor only has to do half the work of compression it normally does to make the same exhaust flow.
Likewise, the supercharger only requires perhaps half the the shaft drive power to provide half the final boosting pressure, so belt drive loads are going to be much lower.
Its a win win situation.
If the blower is feeding into the turbo, I suggest you seriously rethink this.
I speak from about thirty five years of successful twincharging experience.
Sorry for the rather intemperate rant from a grumpy old engineer.
Is the supercharger blowing into the turbo ?
Its rather difficult to see where that pipework all goes from just the pictures, and no written explanation of what it all does.
That is definitely not going to work, it cannot work, unless you are VW, and your goals are fuel economy and emissions, not performance.
The supercharger passes a (sort of) fixed volume of air per revolution. It acts like a metering pump controlling and limiting the amount of air going into the engine. Feeding that into a turbo is going to do nothing except reduce the supercharger discharge pressure once the turbo starts spooling. The supercharger then throttles the air into the turbo.
A less than clever way around that is to bypass the blower. Then you have just an ordinary turbo engine without any compounding, and with the high turbine exhaust back pressure, and the turbo doing all of the work.
All turbo people quickly learn that a bigger turbine (or turbine housing) with reduced exhaust back pressure makes more power. Why is that ?
The answer is that exhaust back pressure kills power, and its especially worse if exhaust pressure is higher than boost pressure as it often is.
A much smarter way to do this is to add a positive displacement supercharger after the turbo.
That increases boost, while also slightly lowering exhaust back pressure.
You get the massive power increase, without having to have the typical big turbo high boost threshold, and the dreadful big turbo lag.
What needs to happen is the supercharger feeds air directly into the engine in the normal "supercharged engine" way, effectively multiplying the capacity of the engine with the larger swept capacity of the supercharger.
The turbo then blows air into the supercharger intake, filling the rotors with more dense air.
Thus supercharging the supercharger with more dense air if you like to think of it that way.
That is where the compounding comes in. The pressure ratios straight out multiply.
What makes compounding so powerful, is that the final induction pressure is always going to be so much higher than the final exhaust back pressure the engine sees.
That is quite difficult to do with just a turbo by itself, even a very big turbo.
With the turbo blowing into a supercharger, you get the excellent cylinder filling and excellent exhaust scavenging, and resistance to detonation if you can get rid of the hot exhaust residuals, while the turbo provides the very high power producing airflow at high engine revs where the Ve of both the supercharger and engine may both be rapidly falling.
You get the advantages of both supercharger and turbo, without the disadvantages either.
It should spool like a crazy thing if you do this the right way.
In fact your turbo may actually be a bit small !
The turbine gets ALL of the exhaust energy to work from, but the turbo compressor only has to do half the work of compression it normally does to make the same exhaust flow.
Likewise, the supercharger only requires perhaps half the the shaft drive power to provide half the final boosting pressure, so belt drive loads are going to be much lower.
Its a win win situation.
If the blower is feeding into the turbo, I suggest you seriously rethink this.
I speak from about thirty five years of successful twincharging experience.
Sorry for the rather intemperate rant from a grumpy old engineer.
Last edited by Warpspeed; 07-21-2020 at 05:42 AM.
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07-21-2020, 07:31 AM
#22
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Thread Starter
Join Date: Jul 2020
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Hang on a minute....
Is the supercharger blowing into the turbo ?
Its rather difficult to see where that pipework all goes from just the pictures, and no written explanation of what it all does.
That is definitely not going to work, it cannot work, unless you are VW, and your goals are fuel economy and emissions, not performance.
The supercharger passes a (sort of) fixed volume of air per revolution. It acts like a metering pump controlling and limiting the amount of air going into the engine. Feeding that into a turbo is going to do nothing except reduce the supercharger discharge pressure once the turbo starts spooling. The supercharger then throttles the air into the turbo.
A less than clever way around that is to bypass the blower. Then you have just an ordinary turbo engine without any compounding, and with the high turbine exhaust back pressure, and the turbo doing all of the work.
All turbo people quickly learn that a bigger turbine (or turbine housing) with reduced exhaust back pressure makes more power. Why is that ?
The answer is that exhaust back pressure kills power, and its especially worse if exhaust pressure is higher than boost pressure as it often is.
A much smarter way to do this is to add a positive displacement supercharger after the turbo.
That increases boost, while also slightly lowering exhaust back pressure.
You get the massive power increase, without having to have the typical big turbo high boost threshold, and the dreadful big turbo lag.
What needs to happen is the supercharger feeds air directly into the engine in the normal "supercharged engine" way, effectively multiplying the capacity of the engine with the larger swept capacity of the supercharger.
The turbo then blows air into the supercharger intake, filling the rotors with more dense air.
Thus supercharging the supercharger with more dense air if you like to think of it that way.
That is where the compounding comes in. The pressure ratios straight out multiply.
What makes compounding so powerful, is that the final induction pressure is always going to be so much higher than the final exhaust back pressure the engine sees.
That is quite difficult to do with just a turbo by itself, even a very big turbo.
With the turbo blowing into a supercharger, you get the excellent cylinder filling and excellent exhaust scavenging, and resistance to detonation if you can get rid of the hot exhaust residuals, while the turbo provides the very high power producing airflow at high engine revs where the Ve of both the supercharger and engine may both be rapidly falling.
You get the advantages of both supercharger and turbo, without the disadvantages either.
It should spool like a crazy thing if you do this the right way.
In fact your turbo may actually be a bit small !
The turbine gets ALL of the exhaust energy to work from, but the turbo compressor only has to do half the work of compression it normally does to make the same exhaust flow.
Likewise, the supercharger only requires perhaps half the the shaft drive power to provide half the final boosting pressure, so belt drive loads are going to be much lower.
Its a win win situation.
If the blower is feeding into the turbo, I suggest you seriously rethink this.
I speak from about thirty five years of successful twincharging experience.
Sorry for the rather intemperate rant from a grumpy old engineer.
Is the supercharger blowing into the turbo ?
Its rather difficult to see where that pipework all goes from just the pictures, and no written explanation of what it all does.
That is definitely not going to work, it cannot work, unless you are VW, and your goals are fuel economy and emissions, not performance.
The supercharger passes a (sort of) fixed volume of air per revolution. It acts like a metering pump controlling and limiting the amount of air going into the engine. Feeding that into a turbo is going to do nothing except reduce the supercharger discharge pressure once the turbo starts spooling. The supercharger then throttles the air into the turbo.
A less than clever way around that is to bypass the blower. Then you have just an ordinary turbo engine without any compounding, and with the high turbine exhaust back pressure, and the turbo doing all of the work.
All turbo people quickly learn that a bigger turbine (or turbine housing) with reduced exhaust back pressure makes more power. Why is that ?
The answer is that exhaust back pressure kills power, and its especially worse if exhaust pressure is higher than boost pressure as it often is.
A much smarter way to do this is to add a positive displacement supercharger after the turbo.
That increases boost, while also slightly lowering exhaust back pressure.
You get the massive power increase, without having to have the typical big turbo high boost threshold, and the dreadful big turbo lag.
What needs to happen is the supercharger feeds air directly into the engine in the normal "supercharged engine" way, effectively multiplying the capacity of the engine with the larger swept capacity of the supercharger.
The turbo then blows air into the supercharger intake, filling the rotors with more dense air.
Thus supercharging the supercharger with more dense air if you like to think of it that way.
That is where the compounding comes in. The pressure ratios straight out multiply.
What makes compounding so powerful, is that the final induction pressure is always going to be so much higher than the final exhaust back pressure the engine sees.
That is quite difficult to do with just a turbo by itself, even a very big turbo.
With the turbo blowing into a supercharger, you get the excellent cylinder filling and excellent exhaust scavenging, and resistance to detonation if you can get rid of the hot exhaust residuals, while the turbo provides the very high power producing airflow at high engine revs where the Ve of both the supercharger and engine may both be rapidly falling.
You get the advantages of both supercharger and turbo, without the disadvantages either.
It should spool like a crazy thing if you do this the right way.
In fact your turbo may actually be a bit small !
The turbine gets ALL of the exhaust energy to work from, but the turbo compressor only has to do half the work of compression it normally does to make the same exhaust flow.
Likewise, the supercharger only requires perhaps half the the shaft drive power to provide half the final boosting pressure, so belt drive loads are going to be much lower.
Its a win win situation.
If the blower is feeding into the turbo, I suggest you seriously rethink this.
I speak from about thirty five years of successful twincharging experience.
Sorry for the rather intemperate rant from a grumpy old engineer.
"Supercharger is feeding turbo, and is bypassed by pressure trigured level at 0.39bar ~5.7psi. (with an actuator from a m90 feed by a standalone boost controller/MAC)
I use two MAC-valves.. one is controlled by a standalone controller to open the SC bypass on given pressure, the other one is hooked up to the MS2-box to control the turbo boost.
Turbo is then feeding a frontmount intercooler."
I appreciate old engineering rants, brought up by an engineer and surrounden with active thinkers and critical minds which might be a challenge if you are a little on the restless creative side!
The goal here was actually not compound charging, that is higher boost levels than achievable with just one of the two. Todays turbo/SC-solutions can already give that, beyond what the rest of the powertrain can handle. The goal was to try to win both low-end from SC and high-end from turbo to create a broader torque-band..
When i started i already had the SC, which was a hotside m45-kit from Jackson Racing. I let this dictate a little on how and what to do. I wanted to keep it as simple as possible.. i could see what some of you guys achieved with electronic steering and bypasses and alot of fabrications but i didn't want to do it that way (even if it might be BETTER).. i wanted to see if i could build a twincharge setup on basically only catalogue parts (catalogue build?). I took a look in my enginebay and realized i had a big(?) space under the sc and plenty(?) of room for routing pressure pipes to an back from where a Turbo should be placed, as long as it is a low mount turbo. I started researching what kits had lowmount in a way that i thought wouldn't interfer with the sc, and ended up with a cast (yay!) manifold from Kraken. I emailed about it to Michael over there and after a while i decided to give it a try.
The setup now acts like this:
SC (with the TB on the original spot, not on SC), feeds the turbo, and blows right through to an intercooler, and then to the TB, on the pipe to the TB i have an open BOV so that the SC wouldn't overheat.. i got this just in case the original JR-bypass wouldn't be enough. So i get a baseboost of about 5-6psi and as soon as i have spool i get my pressure from the turbo. For the SC bypass i mounted a m90-actuator because it has one port on each side of the membran, so with a boostvalve i can control which port i want to feed and when. So when the boost controller (which reads manifold pressure) reaches a certain level i activate pressure on the lower port of the bypass actuator to open the sc-bypass, to let in more air, not just having what flows through the SC but also through the bypass. This has shown to bottom out at boost levels around 13-14psi. which is more than double of what the SC in this high gearing would generate. Also i wanted the SC to give less parasitic loss to the engine power on high rpm's so that is also why i activate the bypass to open up and letting it "freewheel".. or what you call it.. which gives minimal load on the engine.
So to add some reasons for this setup / order of chargers is that the supercharger is hotside, and also a little sensitive to heat i wanted to only worry about radiation heat from manifold and not also heated air from turbo (or even setting up a intercooler between turbo and SC, which would be to complicated), i wanted easiness in my build. The 1.8 BP / Miata engine reacts so good on so very little boost, and putting the set powerceiling at known acceptable tolerance-levels (~220lbft torque max), you reach that level very quickly.. and i imagined to play with forming the torque-curve in a predictable way, by having the advantage of boost-control that turbo offers as part of the tuning-***** if you will.. for setting the right/target curve.
So what i learned from this.. is that very little of my spectrum/revrange is actually compound, which means that my sizing was completely off.. and i have now ordered a much better size turbo for my target power-figures and the SC will have less part of the whole band than i first thought.. the only task is to give base-boost when turbo does not.. otherwise just spin passively..
I'm not aiming for the sky.. just exploring what stock internals let me in characteristics and power..
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07-21-2020, 04:59 PM
#23
Tweaking Enginerd
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Yeah, it looks to me like Garrett must have made some marketing decisions on the HP numbers they tie to these turbos. You would never get 475HP out of a BP on a 2860. That published 475 is no doubt under the absolute ideal PR and exhaust back pressure circumstances. The compressor map for the GTX2860R looks to me like a great choice for a 300whp build at ~PR 2.25-2.5. The GTX2867R G2 has this wonderful little surge line bump around PR 2.75 that really gives excellent torque at ~3250-3500 RPM for my altitude. The efficiency island is also very nice at PR 2.75.
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07-21-2020, 07:33 PM
#25
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Back in the old days, advertised turbo rated power was usually made at a pressure ratio of 2.0 and usually at the last 60% contour line.
All the US and European turbo manufacturers did it that way, so as a rough size indicator it worked out pretty well.
Looking at the GTX2860R compressor map, that indicates about 37 Lb/min flow.
That would be about 528 CFM, and assuming 1.5 CFM/Hp, that gives us a figure of 352Hp.
So you might say compared to anything else the GTX2860 turbo might be considered to be a 350Hp sized turbo in the "old" way of rating, which is probably fairly realistic.
The Chinese now have their own much more imaginative ways of specifying all kinds of things to give give hugely unrealistic figures for advertising purposes.
O/k I now understand better what you are trying to do.
You will not gain much down low, and up high, the air bypass around the blower may be restrictive, and the turbine back pressure will be as high or higher than just running with a straight turbo.
A smaller exhaust housing is going to choke things up top, with I expect a minimal improvement to boost threshold down low.
Running both the supercharger and turbo flat out will as you say, produce an insanely high boost pressure, but you don't have to do it that way, just because its possible.
For what you hope to achieve, a VERY wide flat power band, compounding is still the best way get that, and it does not have to be a high boost high power system.
The way I would approach this would be to run the M45 through the intercooler into the original throttle body, as you are already doing.
Fit a two port actuator to the air bypass, and you also already have that which is good.
Now connect two air lines from the blower bypass actuator to directly across the throttle body.
Full boost pressure ahead of the throttle to one side of the actuator diaphragm, manifold vacuum after the throttle to the other side of the actuator diaphragm.
With the engine idling (at vacuum) that should hold the blower bypass fully open. Full throttle with zero pressure differential across the throttle, the blower bypass should be fully closed.
That should all work very well as just a straight supercharged engine, and you want the pulley ratio to produce about half to two thirds of your final anticipated boost pressure.
The M45 is small, and power is not going to be terribly strong at the top end, but the mid range should be quite good.
Now connect the turbo compressor up so it blows into the supercharger.
Set the wastegate to the full final desired boost pressure, and the wastegate sensing line to just ahead of the throttle body.
Low end torque will increase by more than you are probably expecting, because even though the turbo may be barely turning over, its still blowing into the supercharger helping to fill the rotors.
The slight increase in exhaust volume spins up the turbo more. It creates a very powerful positive feedback system, the turbo helps the blower, and the blower helps the turbo.
That is how to quickly make real low end boost.
The wastegate sets the final boost pressure so the turbo makes up for any flow limitations in the supercharger, especially at the top end where the Ve of such a small supercharger becomes very poor.
That should come pretty close to meeting your expectations, and the final boost pressure need not be set outrageously high to achieve it.
One other point. The M45 is small and people tend to over rev them to try and get high boost and high flow, which is a futile exercise.
Much better to run the blower slowly at a much lower pressure ratio where its more efficient, and use a turbo to fill the blower.
If for example, if a turbo is putting two atmospheres of boost into an M45 (a pressure ratio of two) That M45 is going to flow as much air per revolution as an M90 at the same blower speed !
The M45 will still be operating down in its more efficient area on the flow map too.
The only change would be about double the shaft driving torque would be required to turn it with twice the air density air.
So a bit of turbo boost can easily make up for an under sized supercharger, as long as the final power expectations are realistic.
All the US and European turbo manufacturers did it that way, so as a rough size indicator it worked out pretty well.
Looking at the GTX2860R compressor map, that indicates about 37 Lb/min flow.
That would be about 528 CFM, and assuming 1.5 CFM/Hp, that gives us a figure of 352Hp.
So you might say compared to anything else the GTX2860 turbo might be considered to be a 350Hp sized turbo in the "old" way of rating, which is probably fairly realistic.
The Chinese now have their own much more imaginative ways of specifying all kinds of things to give give hugely unrealistic figures for advertising purposes.
O/k I now understand better what you are trying to do.
You will not gain much down low, and up high, the air bypass around the blower may be restrictive, and the turbine back pressure will be as high or higher than just running with a straight turbo.
A smaller exhaust housing is going to choke things up top, with I expect a minimal improvement to boost threshold down low.
Running both the supercharger and turbo flat out will as you say, produce an insanely high boost pressure, but you don't have to do it that way, just because its possible.
For what you hope to achieve, a VERY wide flat power band, compounding is still the best way get that, and it does not have to be a high boost high power system.
The way I would approach this would be to run the M45 through the intercooler into the original throttle body, as you are already doing.
Fit a two port actuator to the air bypass, and you also already have that which is good.
Now connect two air lines from the blower bypass actuator to directly across the throttle body.
Full boost pressure ahead of the throttle to one side of the actuator diaphragm, manifold vacuum after the throttle to the other side of the actuator diaphragm.
With the engine idling (at vacuum) that should hold the blower bypass fully open. Full throttle with zero pressure differential across the throttle, the blower bypass should be fully closed.
That should all work very well as just a straight supercharged engine, and you want the pulley ratio to produce about half to two thirds of your final anticipated boost pressure.
The M45 is small, and power is not going to be terribly strong at the top end, but the mid range should be quite good.
Now connect the turbo compressor up so it blows into the supercharger.
Set the wastegate to the full final desired boost pressure, and the wastegate sensing line to just ahead of the throttle body.
Low end torque will increase by more than you are probably expecting, because even though the turbo may be barely turning over, its still blowing into the supercharger helping to fill the rotors.
The slight increase in exhaust volume spins up the turbo more. It creates a very powerful positive feedback system, the turbo helps the blower, and the blower helps the turbo.
That is how to quickly make real low end boost.
The wastegate sets the final boost pressure so the turbo makes up for any flow limitations in the supercharger, especially at the top end where the Ve of such a small supercharger becomes very poor.
That should come pretty close to meeting your expectations, and the final boost pressure need not be set outrageously high to achieve it.
One other point. The M45 is small and people tend to over rev them to try and get high boost and high flow, which is a futile exercise.
Much better to run the blower slowly at a much lower pressure ratio where its more efficient, and use a turbo to fill the blower.
If for example, if a turbo is putting two atmospheres of boost into an M45 (a pressure ratio of two) That M45 is going to flow as much air per revolution as an M90 at the same blower speed !
The M45 will still be operating down in its more efficient area on the flow map too.
The only change would be about double the shaft driving torque would be required to turn it with twice the air density air.
So a bit of turbo boost can easily make up for an under sized supercharger, as long as the final power expectations are realistic.
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07-21-2020, 07:45 PM
#26
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Advantage/disadvantage of Turbo-SC vs SC-Turbo.
1. + higher total boost numbers possible with Turbo-SC
2. +higher boost at low rpm possible with Turbo-SC
3. -tougher to control boost with Turbo-SC
4. -increased system complexity with Turbo-SC
If you are boost limited then you probably you don't care about #1 above (most turbos will go to 30psi without compounding with good efficiency)
You can get better low rpm boost, by spinning the charger faster. You can go faster than a supercharger only setup, because at high RPM the SC is not working too hard. (a SC clutch would help this too)
Other than the normal turbo boost control (WG controlled by MS), you would need at a maximum just a single valve to open for controlling this setup. (it's very simple)
So either approach can be successful if your goals fall into the above criteria.
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07-21-2020, 08:12 PM
#27
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IMO, there are advantages and disadvantages of both systems:
Advantage/disadvantage of Turbo-SC vs SC-Turbo.
1. + higher total boost numbers possible with Turbo-SC
2. +higher boost at low rpm possible with Turbo-SC
3. -tougher to control boost with Turbo-SC
4. -increased system complexity with Turbo-SC
If you are boost limited then you probably you don't care about #1 above (most turbos will go to 30psi without compounding with good efficiency)
You can get better low rpm boost, by spinning the charger faster. You can go faster than a supercharger only setup, because at high RPM the SC is not working too hard. (a SC clutch would help this too)
Other than the normal turbo boost control (WG controlled by MS), you would need at a maximum just a single valve to open for controlling this setup. (it's very simple)
So either approach can be successful if your goals fall into the above criteria.
Advantage/disadvantage of Turbo-SC vs SC-Turbo.
1. + higher total boost numbers possible with Turbo-SC
2. +higher boost at low rpm possible with Turbo-SC
3. -tougher to control boost with Turbo-SC
4. -increased system complexity with Turbo-SC
If you are boost limited then you probably you don't care about #1 above (most turbos will go to 30psi without compounding with good efficiency)
You can get better low rpm boost, by spinning the charger faster. You can go faster than a supercharger only setup, because at high RPM the SC is not working too hard. (a SC clutch would help this too)
Other than the normal turbo boost control (WG controlled by MS), you would need at a maximum just a single valve to open for controlling this setup. (it's very simple)
So either approach can be successful if your goals fall into the above criteria.
The biggest advantage is high low rpm boost and essentially lag free throttle response.
2/ Yes it will feel like a large capacity V8 down low.
3/ No tougher than controlling boost with just a turbo.
4/ You still need turbo + supercharger + intercooler + wastegate + blower bypass, no matter what order they are arranged in.
Cost and complexity not too different.
Spinning the charger faster may move you out of the most efficient operating area at mid and higher rpm.
You can put the highest supercharger efficiency point anywhere you want. Probably most useful at engine mid range and above engine mid range.
Declutching or bypassing the supercharger under boost is never a good idea.
You suddenly lose half your boost pressure and half your airflow. How is that going to help anything under acceleration?
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07-21-2020, 08:43 PM
#28
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One other point I should make here.
You often hear turbo people say that feeding a turbo through one of those horrible inefficient belt driven supercharger things, restricts the turbo once it has spooled.
As long as the boost pressure coming out of the supercharger is higher than the boost pressure going into the supercharger, it cannot be restricting the flow.
Restrictions always cause a pressure drop, never a pressure increase !!
The other common urban myth is that compressing the air twice creates twice as much heat as compressing it only once. Not so.
If both stages of compression have about the same efficiency, each would contribute equal shares of half the total final heat added.
Using just one compressor doing all of the work instead of just half, the heat contribution would be exactly the same.
You often hear turbo people say that feeding a turbo through one of those horrible inefficient belt driven supercharger things, restricts the turbo once it has spooled.
As long as the boost pressure coming out of the supercharger is higher than the boost pressure going into the supercharger, it cannot be restricting the flow.
Restrictions always cause a pressure drop, never a pressure increase !!
The other common urban myth is that compressing the air twice creates twice as much heat as compressing it only once. Not so.
If both stages of compression have about the same efficiency, each would contribute equal shares of half the total final heat added.
Using just one compressor doing all of the work instead of just half, the heat contribution would be exactly the same.
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07-21-2020, 09:32 PM
#29
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Location: Toronto Area, Ontario
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Rather than muck up Mr Lindkvist's build thread further, if you want to debate Turbo-SC vs SC-Turbo, I invite you to create a new thread, perhaps in the DIY Turbo section? (I will keep an eye out)
Who knows, maybe we will have a debate rivaling the old turbo vs SC threads of the distant past!
In the meantime, let's continue to help the OP in whatever way we can.
Who knows, maybe we will have a debate rivaling the old turbo vs SC threads of the distant past!
In the meantime, let's continue to help the OP in whatever way we can.
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07-22-2020, 01:33 AM
#31
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Rather than muck up Mr Lindkvist's build thread further, if you want to debate Turbo-SC vs SC-Turbo, I invite you to create a new thread, perhaps in the DIY Turbo section? (I will keep an eye out)
Who knows, maybe we will have a debate rivaling the old turbo vs SC threads of the distant past!
In the meantime, let's continue to help the OP in whatever way we can.
Who knows, maybe we will have a debate rivaling the old turbo vs SC threads of the distant past!
In the meantime, let's continue to help the OP in whatever way we can.
Please don't shut up!
Ok, when it comes to flowing capabilities the form of pipes and ports matter less when you pressurize them.. and i see mr Warpspeeds point in pressurizing the SC to erase or minimize the flow restrictions. Also i thought that total pressure would be more difficult to control if turbo was first but it is not since the wg-actuator (if connected correctly, to the manifold) still reacts to the total pressure and not only from one source. I will have a look now to see if i can do this kind of setup somehow (i think i have space if i clock the turbo differently). Also the car will be more discrete because the turbo will "hide" alot of the sc-intake noise-screeming, which i do enjoy alot but also am worried about when attracting the wrong kind of attention.. When it comes to boost, in my opinion (and excuse my perhaps naive thinking here) i see boost pressure as a result of restriction / lack of airflow in the relationship between air supply vs. air flow.. despite whatever parameters.. (and of course heat when we talk about pressure raising because of heat).. or to put it maybe simpler.. the result of the air, that the poor briggs & stratton engine we use cannot gulp/swallow..
When we talk about boost and torque and hp, i think it would help to think about this in energy terms. When it comes to energy, as you know, energy cannot be created, only converted. In that conversion the less we loose to heat (unless we want heat?), the more we can use in the energy form that we want. It is very interesting to think about running SC within the efficiency band away from the "only heat boost"-part of the band.. to perhaps save some heat-conversion if you may.. and also as long as the WG on the turbo is open, least heat there is created from exhausts.. (not created but kept in the manifold with the help of backpressure from forcing the exhausts through the turbine).. from a heat perspective, the exhausts need to be exited as quickly as possible heatwise..
The new turbo will be a little smaller, but still flows enough both exhausts and compressed air for my power goals.. and i think that the numbers they give, is not a guesstimation on how well our complete setup works in efficiency.. but only converted how much air does the compressor produce and how much exhaust can the exhaust-housing handle.. and with that.. how much power would that amount of air/exhaust flow mount up to if everything of the air is used.. our Briggs&Stratton-efficencies set aside..
Then of course the chinese numbers which i guess are as reliable as the pictures in the adds.. this is why i bought from a local dealer which brand depend on the quality of the stuff they sell (because they are not cheap)..
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07-22-2020, 03:07 AM
#32
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The turbo will not only hide induction noise, turbos also make excellent "rotary mufflers" for the exhaust.
Its the best way to add the slight constant back pressure necessary to reduce the amplitude of the vicious pulsing, and all those nasty discordant shock waves, while getting something back in the process.
Tuned length headers and all that pulsing is unavoidable in a highly tuned normally aspirated race engine, but on the street noise can sometimes draw unwelcome attention.
The whole reliable power thing is based mostly around maximal unrestricted airflow, and well thought out temperature management, and making the engine a happy engine.
Engines are most happy when the induction side is providing very cool dense air, at pressures that exceed the back pressure on the exhaust side of the engine, and with good detonation headroom.
Its the best way to add the slight constant back pressure necessary to reduce the amplitude of the vicious pulsing, and all those nasty discordant shock waves, while getting something back in the process.
Tuned length headers and all that pulsing is unavoidable in a highly tuned normally aspirated race engine, but on the street noise can sometimes draw unwelcome attention.
The whole reliable power thing is based mostly around maximal unrestricted airflow, and well thought out temperature management, and making the engine a happy engine.
Engines are most happy when the induction side is providing very cool dense air, at pressures that exceed the back pressure on the exhaust side of the engine, and with good detonation headroom.
Last edited by Warpspeed; 07-22-2020 at 03:21 AM.
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07-22-2020, 03:20 AM
#33
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The turbo will not only hide induction noise, turbos also make excellent "rotary mufflers" for the exhaust.
Its the best way to add the necessary slight constant back pressure necessary to reduce the amplitude of the vicious pulsing, and all those nasty discordant shock waves, while getting something back in the process.
Tuned length headers and all that pulsing is unavoidable in a highly tuned normally aspirated race engine, but on the street noise can sometimes draw unwelcome attention.
The whole reliable power thing is based mostly around maximal unrestricted airflow, and well thought out temperature management, and making the engine a happy engine.
Engines are most happy when the induction side is providing very cool dense air, at pressures that exceed the back pressure on the exhaust side of the engine, and with good detonation headroom.
Its the best way to add the necessary slight constant back pressure necessary to reduce the amplitude of the vicious pulsing, and all those nasty discordant shock waves, while getting something back in the process.
Tuned length headers and all that pulsing is unavoidable in a highly tuned normally aspirated race engine, but on the street noise can sometimes draw unwelcome attention.
The whole reliable power thing is based mostly around maximal unrestricted airflow, and well thought out temperature management, and making the engine a happy engine.
Engines are most happy when the induction side is providing very cool dense air, at pressures that exceed the back pressure on the exhaust side of the engine, and with good detonation headroom.
I started my build almost two years ago with preparing those things.. so my actions to control heat has been : qmax reroute, mishimoto oversized radiator, mishimoto thermostat oil-cooler, cold-air-intake-solutions on different steps (first version i put the filter on the passenger side with just a 90-degree elbow from tb, which improved intake temps alot), and then also running e85 for a cooler-burn and better cooling-effect on the engine.. i also have a wmi-kit laying on the bench to pre-spray the SC in case of high MAT-values, but haven't need that yet since i installed the IC.
I would need to have a pressure-sensor for the exhaust-manifold to keep track of the "backpressure" but previously i didn't worry since exhaust was in only sc-version very freeflowing de-cat and everything.. and with the 2871 the flow was also oversized and with a 3" full system also de-cat.. and the powerlevels i aim for, this is only a problem if things break-loose and clog the exhaust path..
I am not overnegative about running sc first since i noticed how nicely it worked and that the combo made a difference compared to both sc-only and turbo-only (when i installed the turbo, i made sure it ran ok before bolting on the sc, so things wouldn't go crazy and become difficult to troubleshoot).. the car was so much fun to drive and even if my setup hurt spool and top-end-power i had enough for a really fun experience driving it.. tires breaking loose in 60mph/100kmh in 3rd gear on damp roads.. it was starting to become a handful to say the least..
I would like to try the turbo-first-setup later.. i will have to figure out a way to route intake-air without interfering with the sc-pressure-pipe, but if i can find room, i will try it.. if not, i am sure this less-efficient sc-turbo-setup will be good enough for my goals
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07-22-2020, 03:41 AM
#34
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I am looking at maybe a two year build as well, with my sixth twincharge project. Far too early to start a build thread, but I am taking photographs at each very slow step, and very gradually accumulating parts as I can afford them.
The only thing that really matters is that you are happy with your project and the final results.
Someone else will always have more money, better facilities, a higher power goal, and world beating ambitions.
I do it for fun, and as a learning exercise in retirement to try out new and different ideas, and if its something a bit unusual or untried, so much the better if it works.
The only thing that really matters is that you are happy with your project and the final results.
Someone else will always have more money, better facilities, a higher power goal, and world beating ambitions.
I do it for fun, and as a learning exercise in retirement to try out new and different ideas, and if its something a bit unusual or untried, so much the better if it works.
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07-22-2020, 03:47 AM
#35
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I am looking at maybe a two year build as well, with my sixth twincharge project. Far too early to start a build thread, but I am taking photographs at each very slow step, and very gradually accumulating parts as I can afford them.
The only thing that really matters is that you are happy with your project and the final results.
Someone else will always have more money, better facilities, a higher power goal, and world beating ambitions.
I do it for fun, and as a learning exercise in retirement to try out new and different ideas, and if its something a bit unusual or untried, so much the better if it works.
The only thing that really matters is that you are happy with your project and the final results.
Someone else will always have more money, better facilities, a higher power goal, and world beating ambitions.
I do it for fun, and as a learning exercise in retirement to try out new and different ideas, and if its something a bit unusual or untried, so much the better if it works.
Twincharging (which my setup is more than compound charging, i am starting to understand) has been a way to challenge myself and my theoretical understanding.. something odd to learn and explore.. and even if this build is full of compromises it also pushes the limit of different parts a little to get the best of each..
I think you should share what you have even if it feels early, this is a very nice way to shoot ideas and inspire/get inspiration from others!
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07-22-2020, 04:47 AM
#36
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No, I think I will keep all my ideas to myself at this stage.
I did as a first attempt show how I had modified a Nissan GTR plenum and individual throttle bodies to work on a BP-4W cylinder head, and posted pictures of exactly how I did it.
I was attacked, told to start a build thread of my own (by a moderator no less) and not to mess up other peoples threads.
I did as a first attempt show how I had modified a Nissan GTR plenum and individual throttle bodies to work on a BP-4W cylinder head, and posted pictures of exactly how I did it.
I was attacked, told to start a build thread of my own (by a moderator no less) and not to mess up other peoples threads.
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07-22-2020, 04:50 AM
#37
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No, I think I will keep all my ideas to myself at this stage.
I did as a first attempt show how I had modified a Nissan GTR plenum and individual throttle bodies to work on a BP-4W cylinder head, and posted pictures of exactly how I did it.
I was attacked, told to start a build thread of my own (by a moderator no less) and not to mess up other peoples threads.
I did as a first attempt show how I had modified a Nissan GTR plenum and individual throttle bodies to work on a BP-4W cylinder head, and posted pictures of exactly how I did it.
I was attacked, told to start a build thread of my own (by a moderator no less) and not to mess up other peoples threads.
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07-22-2020, 09:25 AM
#39
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(it was supposed to be a gtx2860 at first, but it was marked on backorder.. and a 2867 they had in stock.. so picking it up, first thing tomorrow morning!)
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