Twins!
Twins!
(03-30-2010, 03:43 AM)winmutt Im thinking you need more cold air and faster.
From the '10mm element thread':
(03-30-2010, 03:43 AM)winmutt Im thinking you need more cold air and faster.
(04-06-2010, 12:09 AM)shredator Whaddya think?
(04-06-2010, 12:09 AM)shredator Whaddya think?
I think there will be more educated posts, but do you really need all that air?
I know it is fun discussing ifs and whats but wouldn't be more constructive working on something really achievable .
For the heck of the discussion, where is the second turbo?
(04-06-2010, 01:42 AM)Deni I think there will be more educated posts, but do you really need all that air?
I know it is fun discussing ifs and whats but wouldn't be more constructive working on something really achievable .
For the heck of the discussion, where is the second turbo?
(04-06-2010, 01:42 AM)Deni I think there will be more educated posts, but do you really need all that air?
I know it is fun discussing ifs and whats but wouldn't be more constructive working on something really achievable .
For the heck of the discussion, where is the second turbo?
Two turbos with two intercoolers?
You're going to lose your engine under all that plumbing.
Honestly an idi mercedes is not going to hold together with 65psi boost up it. Your calcs seem on track, but I work in metric and I can't be arsed converting the answers to metric to check them with my spreadsheets.
Sure a single turbo can produce big hp numbers, but it becomes a dyno queen that does nothing but belch smoke until the turbo finally spools in the last top bit of the rev range.
Compounds offer flexibility that single stage compressors can't.
(04-06-2010, 04:50 PM)Kiwibacon Compounds offer flexibility that single stage compressors can't.
(04-06-2010, 04:50 PM)Kiwibacon Compounds offer flexibility that single stage compressors can't.
(04-06-2010, 05:05 PM)ForcedInduction(04-06-2010, 04:50 PM)Kiwibacon Compounds offer flexibility that single stage compressors can't.
As do VNT/VGT turbos.
(04-06-2010, 05:14 PM)Kiwibacon VNT/VGT turbos are single stage compressors. The above statement still applies.
(04-06-2010, 05:14 PM)Kiwibacon VNT/VGT turbos are single stage compressors. The above statement still applies.
(04-07-2010, 05:30 AM)ForcedInduction No it doesn't, you're missing the point.
(04-07-2010, 05:30 AM)ForcedInduction No it doesn't, you're missing the point.
(04-08-2010, 12:53 AM)Kiwibacon The rest of your post is irrelevant.
(04-08-2010, 12:53 AM)Kiwibacon The rest of your post is irrelevant.
(04-08-2010, 08:36 AM)ForcedInduction Far from it, it invalidates the argument for compounds. Proper matching of the turbo is required instead of just tossing on a BFT and "hoo wee, I've got 500hp at 7000rpm but 100hp below 5000rpm!"
(04-08-2010, 08:36 AM)ForcedInduction As stated before, BMW's "big" turbo is simply a K26. If they can make 265hp using the same outdated and inefficient turbo found on many of our engines, there is no reason you can't make 300hp with a single turbo that will spool up as fast as the stock turbo.
(04-08-2010, 08:36 AM)ForcedInduction Compound turbos aren't staged, they are for multiplying the pressure ratio to get high pressures.
(04-08-2010, 08:36 AM)ForcedInduction Low end performance is still limited by what HP turbo is used and the LP turbo won't spool until the second half of the RPM range anyways. PSI for PSI under 35 you'll be making LESS power than with a single because of the efficiency drop across multiple turbines and much higher compressed air temperature.
(04-08-2010, 08:36 AM)ForcedInduction Far from it, it invalidates the argument for compounds. Proper matching of the turbo is required instead of just tossing on a BFT and "hoo wee, I've got 500hp at 7000rpm but 100hp below 5000rpm!"
(04-08-2010, 08:36 AM)ForcedInduction As stated before, BMW's "big" turbo is simply a K26. If they can make 265hp using the same outdated and inefficient turbo found on many of our engines, there is no reason you can't make 300hp with a single turbo that will spool up as fast as the stock turbo.
(04-08-2010, 08:36 AM)ForcedInduction Compound turbos aren't staged, they are for multiplying the pressure ratio to get high pressures.
(04-08-2010, 08:36 AM)ForcedInduction Low end performance is still limited by what HP turbo is used and the LP turbo won't spool until the second half of the RPM range anyways. PSI for PSI under 35 you'll be making LESS power than with a single because of the efficiency drop across multiple turbines and much higher compressed air temperature.
http://www.youtube.com/watch?v=y-Me6yWAp...re=related
Here's a good argument for combination turbos. I especially like how he set it up. It took me a while to figure out the piping but once I understood what he was doing I really felt he was on to something.
Check it out.
Derek
Jettmar, thats not a compound system. Its called a modulated 2-stage. Same thing BMW uses on the BMW 335d.
(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.. How is that different from compounds? Edit: basically, you just tweak the wastegates to keep the turbos in their maps and give you the airflow you want... Is a regular compound setup different somehow (i.e. no wastegates?)
(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.. How is that different from compounds? Edit: basically, you just tweak the wastegates to keep the turbos in their maps and give you the airflow you want... Is a regular compound setup different somehow (i.e. no wastegates?)
Actually I think FI is correct it is staged. Listen to Marc explain the details, he mentions the external wastegate between the two turbos that dumps all exhaust to bigger turbo after 22psi.
If you stop the video at 17 seconds have a look at the piping. After the ex manifold collector it 'y's to the small turbo (st) and to a wastegate dumping to the big turbo (BT). Before EMP reaches 22psi all exhaust is going through the st into the BT prespooling it. Once EMP reaches 22psi the wastegate opens and sends ALL exhaust to the BT so that removes and pressure from the st which therefore means the charge after 22psi is only flowing through the st, not being compressed by it. for it to be a true compound setup there is no wastegate 'between' the two turbos, there is wastegate protection for overboost but not in this manner.
(04-12-2010, 07:50 PM)Telecommbrkr Actually I think FI is correct it is staged. Listen to Marc explain the details, he mentions the external wastegate between the two turbos that dumps all exhaust to bigger turbo after 22psi.
(04-12-2010, 07:50 PM)Telecommbrkr Actually I think FI is correct it is staged. Listen to Marc explain the details, he mentions the external wastegate between the two turbos that dumps all exhaust to bigger turbo after 22psi.
(04-12-2010, 07:15 PM)Kiwibacon(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.. How is that different from compounds? Edit: basically, you just tweak the wastegates to keep the turbos in their maps and give you the airflow you want... Is a regular compound setup different somehow (i.e. no wastegates?)
It is a compound setup, they're just limiting boost to a very low level for a compound setup (22psi).
That video nicely sums up all the reasons that compound setups have benefits even at boost pressures that single turbos have no problems with.
(04-12-2010, 07:15 PM)Kiwibacon(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.. How is that different from compounds? Edit: basically, you just tweak the wastegates to keep the turbos in their maps and give you the airflow you want... Is a regular compound setup different somehow (i.e. no wastegates?)
It is a compound setup, they're just limiting boost to a very low level for a compound setup (22psi).
That video nicely sums up all the reasons that compound setups have benefits even at boost pressures that single turbos have no problems with.
(04-12-2010, 08:04 PM)Telecommbrkr I do agree that Marc does say some things that tell of the benefits to be gained from compounding. I do believe I will be trying this .............someday, when the usual time and money allow. The main idea of compounding that has stuck with me in some of the reasearching that I have done on the subject, is the fact that the 20 or 30+ psi of boost that I am looking for from such a set up can be achieved early in the powerband and maintained throughout the entire rev range consistenly, and neither turbo has to 'break a sweat' so to speak. When compared to variable turbos, yes they accomplish nearly the same effect, and are a little easier to set up, but I believe that they lack a possible robustness of tunability in regards to the combined turbo map potential of the two turbos.
Just my semi-informed opinion.....
(04-12-2010, 08:04 PM)Telecommbrkr I do agree that Marc does say some things that tell of the benefits to be gained from compounding. I do believe I will be trying this .............someday, when the usual time and money allow. The main idea of compounding that has stuck with me in some of the reasearching that I have done on the subject, is the fact that the 20 or 30+ psi of boost that I am looking for from such a set up can be achieved early in the powerband and maintained throughout the entire rev range consistenly, and neither turbo has to 'break a sweat' so to speak. When compared to variable turbos, yes they accomplish nearly the same effect, and are a little easier to set up, but I believe that they lack a possible robustness of tunability in regards to the combined turbo map potential of the two turbos.
Just my semi-informed opinion.....
(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.
Quote:Listen to Marc explain the details, he mentions the external wastegate between the two turbos that dumps all exhaust to bigger turbo after 22psi.Exactly. He says right in the video the small turbo puts out 20psi and at 22psi "that wastegate goes wide open and it flows as much exhaust around the small turbo as it can".
If you stop the video at 17 seconds have a look at the piping. After the ex manifold collector it 'y's to the small turbo (st) and to a wastegate dumping to the big turbo (BT). Before EMP reaches 22psi all exhaust is going through the st into the BT prespooling it. Once EMP reaches 22psi the wastegate opens and sends ALL exhaust to the BT so that removes and pressure from the st which therefore means the charge after 22psi is only flowing through the st, not being compressed by it. for it to be a true compound setup there is no wastegate 'between' the two turbos, there is wastegate protection for overboost but not in this manner.
Quote:That video nicely sums up all the reasons that compound setups have benefits even at boost pressures that single turbos have no problems with.Except the exhaust efficiency loss, added weight and added intake air heat.
(04-12-2010, 07:58 PM)Kiwibacon They don't send all the exhaust around the small turbo, that would require shutting off exhaust which doesn't happen.They don't have to, BMW doesn't do it either. All they need to do is flow enough exhaust around the turbine for the pressures on the inlet and outlet of the turbine to equalize and there will be little flow (work done) across it. That functionally takes it out of the loop.
...
That wastegate doesn't block flow to the HP turbo, it merely dumps the "wasted" exhaust into the LP turbo.
(04-12-2010, 07:02 PM)GREASY_BEAST Forced, why is that not a compound setup? It is two turbos, LP feeding HP, each with its own wastegate.
Quote:Listen to Marc explain the details, he mentions the external wastegate between the two turbos that dumps all exhaust to bigger turbo after 22psi.Exactly. He says right in the video the small turbo puts out 20psi and at 22psi "that wastegate goes wide open and it flows as much exhaust around the small turbo as it can".
If you stop the video at 17 seconds have a look at the piping. After the ex manifold collector it 'y's to the small turbo (st) and to a wastegate dumping to the big turbo (BT). Before EMP reaches 22psi all exhaust is going through the st into the BT prespooling it. Once EMP reaches 22psi the wastegate opens and sends ALL exhaust to the BT so that removes and pressure from the st which therefore means the charge after 22psi is only flowing through the st, not being compressed by it. for it to be a true compound setup there is no wastegate 'between' the two turbos, there is wastegate protection for overboost but not in this manner.
Quote:That video nicely sums up all the reasons that compound setups have benefits even at boost pressures that single turbos have no problems with.Except the exhaust efficiency loss, added weight and added intake air heat.
(04-12-2010, 07:58 PM)Kiwibacon They don't send all the exhaust around the small turbo, that would require shutting off exhaust which doesn't happen.They don't have to, BMW doesn't do it either. All they need to do is flow enough exhaust around the turbine for the pressures on the inlet and outlet of the turbine to equalize and there will be little flow (work done) across it. That functionally takes it out of the loop.
...
That wastegate doesn't block flow to the HP turbo, it merely dumps the "wasted" exhaust into the LP turbo.
(04-12-2010, 11:02 PM)ForcedInduction Except the exhaust efficiency loss, added weight and added intake air heat.
(04-12-2010, 11:02 PM)ForcedInduction Except the exhaust efficiency loss, added weight and added intake air heat.
(04-12-2010, 11:43 PM)Kiwibacon You keep repeating this, but have offered no proof or explanation to backup these claims.Thats because you keep not reading my posts.
Quote:The graph you keep trotting out is just one example of how a compound system can run. Attempting to apply it to all systems is a little foolhardy.I'm not attempting to apply them to anything, its what people keep building!
Quote:Their current system (I was at BMW Welt in Munich this February) externally bears little relation to the system they were using several years ago.Which is the one being discussed.
Quote:The BMW system is different in many aspects to the system in the video which we are currently discussing.Right, BMW actually has a compound mode that makes 42psi of boost for a brief period. Functionally, they are identical. The difference is in timing of the exhaust bypass.
(04-12-2010, 11:43 PM)Kiwibacon You keep repeating this, but have offered no proof or explanation to backup these claims.Thats because you keep not reading my posts.
Quote:The graph you keep trotting out is just one example of how a compound system can run. Attempting to apply it to all systems is a little foolhardy.I'm not attempting to apply them to anything, its what people keep building!
Quote:Their current system (I was at BMW Welt in Munich this February) externally bears little relation to the system they were using several years ago.Which is the one being discussed.
Quote:The BMW system is different in many aspects to the system in the video which we are currently discussing.Right, BMW actually has a compound mode that makes 42psi of boost for a brief period. Functionally, they are identical. The difference is in timing of the exhaust bypass.
(04-13-2010, 02:40 AM)ForcedInduction Thats because you keep not reading my posts.
PSI for PSI, compounds are less efficient. They have many times more exhaust surface area (heat energy lost to the atmosphere), two pressure drops, two masses to overcome inertia, two stages of compression adding their own heat to the air and the added vehicle weight.
Compounds at sea level, each working at a 1.7 pressure ratio.
LP turbo
10psi@65% efficiency
Temp out at 85*f ambient: 221*f
HP turbo
16psi out
197*f gain, 386*f outlet temperature
----
A single turbo @16psi will be 280*f.
(04-13-2010, 02:40 AM)ForcedInduction Thats because you keep not reading my posts.
PSI for PSI, compounds are less efficient. They have many times more exhaust surface area (heat energy lost to the atmosphere), two pressure drops, two masses to overcome inertia, two stages of compression adding their own heat to the air and the added vehicle weight.
Compounds at sea level, each working at a 1.7 pressure ratio.
LP turbo
10psi@65% efficiency
Temp out at 85*f ambient: 221*f
HP turbo
16psi out
197*f gain, 386*f outlet temperature
----
A single turbo @16psi will be 280*f.
(04-13-2010, 03:01 AM)Kiwibacon A LP turbo pushing 10psi on the same intake would produce air at 103C, the HP turbo sucking on that produces air at 140C (284F).Your math is wrong.
(04-13-2010, 03:01 AM)Kiwibacon A LP turbo pushing 10psi on the same intake would produce air at 103C, the HP turbo sucking on that produces air at 140C (284F).Your math is wrong.
(04-13-2010, 03:43 AM)ForcedInduction Your math is wrong.
You're not taking into account the HP turbo's inlet temperature and still calculating with ambient.
Doing as you did with a 30c inlet temperature and 24psi absolute pressure, I come up with 103*c as well.
Doing it correctly with a 108*c inlet temperature, surprise, 200*c.
So you're right, I had an error in my math, I listed the HP turbo's outlet temperature to be too cool!
(04-13-2010, 03:43 AM)ForcedInduction Your math is wrong.
You're not taking into account the HP turbo's inlet temperature and still calculating with ambient.
Doing as you did with a 30c inlet temperature and 24psi absolute pressure, I come up with 103*c as well.
Doing it correctly with a 108*c inlet temperature, surprise, 200*c.
So you're right, I had an error in my math, I listed the HP turbo's outlet temperature to be too cool!
(04-13-2010, 04:48 AM)Kiwibacon There's a serious error in your calcs and you still haven't found it.Sorry bud, bad math on your part doesn't mean an error on mine.
Quote:My calculation sets are correct, they've been verified by others.I have yet to see any "others" post their math. In fact, I haven't even seen you post YOUR math.
Quote:The HP turbo is only working at PR of 1.24 (equivalent to 3.5psi), which is why it's adding such a small amount of heat (37C).3.5psi makes compounds even more of a waste! At such a low ratio you'll just be running the turbo in its choke range, reducing its compression efficiency even more.
(04-13-2010, 04:48 AM)Kiwibacon There's a serious error in your calcs and you still haven't found it.Sorry bud, bad math on your part doesn't mean an error on mine.
Quote:My calculation sets are correct, they've been verified by others.I have yet to see any "others" post their math. In fact, I haven't even seen you post YOUR math.
Quote:The HP turbo is only working at PR of 1.24 (equivalent to 3.5psi), which is why it's adding such a small amount of heat (37C).3.5psi makes compounds even more of a waste! At such a low ratio you'll just be running the turbo in its choke range, reducing its compression efficiency even more.
lol, I get different numbers than both of you.
If you guys have spreadsheets, you should post em! that way if there are mistakes folks can find them. It would be alot more constructive than this "you're wrong", "no you're wrong", "no you're wrong!" nonsense.
btw, has anyone found errors in mine?
It seems to me that turbos plumbed in this manner could be operated either as "compounds" or "modulated twins" pretty easily, and that the two modes of operation are not exclusive of each other, so the system could be somewhere in between and possibly get some of the benefits of each.
fuck it. Im building the damn thing. Then at least we can argue over actual results.
has anyone welded stainless headers with 75/25 argon/co2? If so, how did it turn out? Did/do you have any corrosion/brittleness at your joints?
(04-13-2010, 05:27 AM)ForcedInduction 3.5psi makes compounds even more of a waste! At such a low ratio you'll just be running the turbo in its choke range, reducing its compression efficiency even more.
(04-13-2010, 03:23 PM)shredator lol, I get different numbers than both of you.
If you guys have spreadsheets, you should post em! that way if there are mistakes folks can find them. It would be alot more constructive than this "you're wrong", "no you're wrong", "no you're wrong!" nonsense.
btw, has anyone found errors in mine?
(04-13-2010, 03:23 PM)shredator It seems to me that turbos plumbed in this manner could be operated either as "compounds" or "modulated twins" pretty easily, and that the two modes of operation are not exclusive of each other, so the system could be somewhere in between and possibly get some of the benefits of each.
(04-13-2010, 03:23 PM)shredator has anyone welded stainless headers with 75/25 argon/co2? If so, how did it turn out? Did/do you have any corrosion/brittleness at your joints?
(04-13-2010, 05:27 AM)ForcedInduction 3.5psi makes compounds even more of a waste! At such a low ratio you'll just be running the turbo in its choke range, reducing its compression efficiency even more.
(04-13-2010, 03:23 PM)shredator lol, I get different numbers than both of you.
If you guys have spreadsheets, you should post em! that way if there are mistakes folks can find them. It would be alot more constructive than this "you're wrong", "no you're wrong", "no you're wrong!" nonsense.
btw, has anyone found errors in mine?
(04-13-2010, 03:23 PM)shredator It seems to me that turbos plumbed in this manner could be operated either as "compounds" or "modulated twins" pretty easily, and that the two modes of operation are not exclusive of each other, so the system could be somewhere in between and possibly get some of the benefits of each.
(04-13-2010, 03:23 PM)shredator has anyone welded stainless headers with 75/25 argon/co2? If so, how did it turn out? Did/do you have any corrosion/brittleness at your joints?
(04-13-2010, 02:40 AM)ForcedInduction Compounds at sea level, each working at a 1.7 pressure ratio.
LP turbo
10psi@65% efficiency
Temp out at 85*f ambient: 221*f
HP turbo
16psi out
197*f gain, 386*f outlet temperature
----
A single turbo @16psi will be 280*f.
(04-13-2010, 02:40 AM)ForcedInduction Compounds at sea level, each working at a 1.7 pressure ratio.
LP turbo
10psi@65% efficiency
Temp out at 85*f ambient: 221*f
HP turbo
16psi out
197*f gain, 386*f outlet temperature
----
A single turbo @16psi will be 280*f.
(04-13-2010, 05:28 PM)Kiwibacon Where are your figures? I didn't see them but I'm more than happy to check them through.not sure what you mean by 'figures'... you can download my spreadsheet at the bottom of the first post. the columns on the right show the volume flow rates and mass flow rates at the various locations in the system. So, pick the column for the units that you want, and go to the row for the location in the system that you want. some of the colums display metric units, so hopefully you wont have to convert those. There are also maps for the gt2056v and the he351ve pasted into the spreadsheet, but nothing gets plotted on them automatically.
(04-13-2010, 05:28 PM)Kiwibacon Honestly, stainless isn't a good material for headers. IMO it's for show cars.Can you elaborate? What are the drawbacks, other than cost, and the fact that you cant use 75/25? It wasnt really that much more expensive, and slight additional cost seemed to be worth the corrosion protection to me. Now I realize that I will probably have to TIG it. That makes me wish that I just went with mild steel, cause I suck at TIG.
(04-13-2010, 05:28 PM)Kiwibacon Where are your figures? I didn't see them but I'm more than happy to check them through.not sure what you mean by 'figures'... you can download my spreadsheet at the bottom of the first post. the columns on the right show the volume flow rates and mass flow rates at the various locations in the system. So, pick the column for the units that you want, and go to the row for the location in the system that you want. some of the colums display metric units, so hopefully you wont have to convert those. There are also maps for the gt2056v and the he351ve pasted into the spreadsheet, but nothing gets plotted on them automatically.
(04-13-2010, 05:28 PM)Kiwibacon Honestly, stainless isn't a good material for headers. IMO it's for show cars.Can you elaborate? What are the drawbacks, other than cost, and the fact that you cant use 75/25? It wasnt really that much more expensive, and slight additional cost seemed to be worth the corrosion protection to me. Now I realize that I will probably have to TIG it. That makes me wish that I just went with mild steel, cause I suck at TIG.
(04-15-2010, 04:44 PM)shredator(04-13-2010, 05:28 PM)Kiwibacon Where are your figures? I didn't see them but I'm more than happy to check them through.not sure what you mean by 'figures'... you can download my spreadsheet at the bottom of the first post. the columns on the right show the volume flow rates and mass flow rates at the various locations in the system. So, pick the column for the units that you want, and go to the row for the location in the system that you want. some of the colums display metric units, so hopefully you wont have to convert those. There are also maps for the gt2056v and the he351ve pasted into the spreadsheet, but nothing gets plotted on them automatically.
(04-13-2010, 05:28 PM)Kiwibacon Honestly, stainless isn't a good material for headers. IMO it's for show cars.Can you elaborate? What are the drawbacks, other than cost, and the fact that you cant use 75/25? It wasnt really that much more expensive, and slight additional cost seemed to be worth the corrosion protection to me. Now I realize that I will probably have to TIG it. That makes me wish that I just went with mild steel, cause I suck at TIG.
(04-15-2010, 04:44 PM)shredator(04-13-2010, 05:28 PM)Kiwibacon Where are your figures? I didn't see them but I'm more than happy to check them through.not sure what you mean by 'figures'... you can download my spreadsheet at the bottom of the first post. the columns on the right show the volume flow rates and mass flow rates at the various locations in the system. So, pick the column for the units that you want, and go to the row for the location in the system that you want. some of the colums display metric units, so hopefully you wont have to convert those. There are also maps for the gt2056v and the he351ve pasted into the spreadsheet, but nothing gets plotted on them automatically.
(04-13-2010, 05:28 PM)Kiwibacon Honestly, stainless isn't a good material for headers. IMO it's for show cars.Can you elaborate? What are the drawbacks, other than cost, and the fact that you cant use 75/25? It wasnt really that much more expensive, and slight additional cost seemed to be worth the corrosion protection to me. Now I realize that I will probably have to TIG it. That makes me wish that I just went with mild steel, cause I suck at TIG.