wastegate with centri blower?
11-30-2006, 10:11 AM
#102
Originally Posted by 70Stang
RPM - 1000 2000 3000 4000 5000 6000
BOOST- 1 2 3 5 7 10
or, with a restrictor...
RPM - 1000 2000 3000 4000 5000 6000
BOOST- 1 4 7 10 10 10
BOOST- 1 2 3 5 7 10
or, with a restrictor...
RPM - 1000 2000 3000 4000 5000 6000
BOOST- 1 4 7 10 10 10
Secondly, even a restrictor won't provide a "flat" boost curve of 10 psi at 4000 - 6000 rpm. The boost loss is proportional to flow rate squared. So, there is loss at even 4000 rpm, just not as much as 6000. If you restrict it to lose 4 psi at 6000, then it will still lose almost 2 psi at 4000.
When I get home this weekend, I'll quantify some of the extra losses caused by pulleying up and adding a restrictor.
11-30-2006, 12:12 PM
#103
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Originally Posted by kp
I'm not sure how you are getting 6psi @ 3500, I have a small cam and 9.5: compression and with the 7.25/3.4 on a D1SC I'm only seeing 5psi @ 3500 and seeing 17psi @ 7000.
There were some good points in this thread but you have to remember sometimes results can be a little skewed depending on what someone is trying to sell plus the 'jones factor.' Its very easy to find an example to prove you point but just because something worked for so and so doesnt mean its going to work for you. My advice is always just try it for youself and see what happens, thats simple enough.
Here is a 1st gear a pass with my car with the 7.25/3.4 with the inlet hat on, I deleted a ton of frames to make it all fit on the the screen but thats with the 2step at 3500rpm up 7000rpm (max impeller on a D1SC). I cant honestly see 7psi @ 3500 unless its a 100% stock engine and if you are trying that the stock engine wont last long.
There were some good points in this thread but you have to remember sometimes results can be a little skewed depending on what someone is trying to sell plus the 'jones factor.' Its very easy to find an example to prove you point but just because something worked for so and so doesnt mean its going to work for you. My advice is always just try it for youself and see what happens, thats simple enough.
Here is a 1st gear a pass with my car with the 7.25/3.4 with the inlet hat on, I deleted a ton of frames to make it all fit on the the screen but thats with the 2step at 3500rpm up 7000rpm (max impeller on a D1SC). I cant honestly see 7psi @ 3500 unless its a 100% stock engine and if you are trying that the stock engine wont last long.
In my case i got 13psi with a 3.85 pulley and 7.25 crank with the hat and filter off. I saw 10psi with the hat on and the same pulley, but the filter and hat on. The setup was a stock engine with just a cam. It still running strong, but i decided to save it and move to a new short block. Im keeping the stock engine for a new project Im doing.
Anyways take the data for what it is... those are the results we got and Im not trying to sell anything
Edit: Thinking about it more... It could be the different loads each setup are facing... I mean my car weighs 3950lbs with me in it while your car could be moving 3500lbs or so. That 450lbs could be the factor that is generating the extra 1-2psi at low RPM's.
11-30-2006, 06:53 PM
#104
with 1.28 60's I doubt I'm getting any belt slippage, maybe you are getting belt slippage up top 
Its on the 2step and trans brake @ 3500rpm and it will bounce between 3600-3300 on the 2 step for a few seconds before I let go of the brake, the around 5000rpm the converter starts locking and it will hang there for a tiny bit also. Remember all that stiff in that lig is happening in 1.5 seconds. After the 1st 40' my car will never drop below 6000rpm so I cant use 2nd or 3rd for an example.
No one is trying to argue with your results, what mike and anderek are saying is you loose some efficiency by blowing boost off or restricting the inlet and you cant argue with that. If you have a big enough blower using a restriction may help flatten the curve out a little but these blowers have a pretty narrow window where they make a lot of airflow vs heat. Spin it too slow and it drops off like a stone, spin it too high and the same thing happens.
I see very litle difference with the hat on or off, it even fell off the car and I ran over it during a burnout and the car ran no different for the next three passes lol. But on the dyno it picks up with the hat off, all has to do with average HP. But like I posted earlier in this thread there sometimes is more then one 'right' way to do things
Its on the 2step and trans brake @ 3500rpm and it will bounce between 3600-3300 on the 2 step for a few seconds before I let go of the brake, the around 5000rpm the converter starts locking and it will hang there for a tiny bit also. Remember all that stiff in that lig is happening in 1.5 seconds. After the 1st 40' my car will never drop below 6000rpm so I cant use 2nd or 3rd for an example.
No one is trying to argue with your results, what mike and anderek are saying is you loose some efficiency by blowing boost off or restricting the inlet and you cant argue with that. If you have a big enough blower using a restriction may help flatten the curve out a little but these blowers have a pretty narrow window where they make a lot of airflow vs heat. Spin it too slow and it drops off like a stone, spin it too high and the same thing happens.
I see very litle difference with the hat on or off, it even fell off the car and I ran over it during a burnout and the car ran no different for the next three passes lol. But on the dyno it picks up with the hat off, all has to do with average HP. But like I posted earlier in this thread there sometimes is more then one 'right' way to do things
Originally Posted by LSs1Power
I dont know too, but you can see the boost graph and TQ numbers that are backing the boost numbers too. Are you getting any belt slippage around 3200-3600RPM? It seems your staying around 5psi for a while and dipping back to 4.9psi before u get more boost.
In my case i got 13psi with a 3.85 pulley and 7.25 crank with the hat and filter off. I saw 10psi with the hat on and the same pulley, but the filter and hat on. The setup was a stock engine with just a cam. It still running strong, but i decided to save it and move to a new short block. Im keeping the stock engine for a new project Im doing.
Anyways take the data for what it is... those are the results we got and Im not trying to sell anything
Edit: Thinking about it more... It could be the different loads each setup are facing... I mean my car weighs 3950lbs with me in it while your car could be moving 3500lbs or so. That 450lbs could be the factor that is generating the extra 1-2psi at low RPM's.
In my case i got 13psi with a 3.85 pulley and 7.25 crank with the hat and filter off. I saw 10psi with the hat on and the same pulley, but the filter and hat on. The setup was a stock engine with just a cam. It still running strong, but i decided to save it and move to a new short block. Im keeping the stock engine for a new project Im doing.
Anyways take the data for what it is... those are the results we got and Im not trying to sell anything
Edit: Thinking about it more... It could be the different loads each setup are facing... I mean my car weighs 3950lbs with me in it while your car could be moving 3500lbs or so. That 450lbs could be the factor that is generating the extra 1-2psi at low RPM's.
11-30-2006, 07:24 PM
#105
Originally Posted by kwiksilverz
....
I have to admit, I am not into the "math" side of things, I did have an interest in engineering years ago, but saw first hand that just because it looks perfect in formula- it doesn't mean that the "wrong" way won't work better in practice. ....
I have to admit, I am not into the "math" side of things, I did have an interest in engineering years ago, but saw first hand that just because it looks perfect in formula- it doesn't mean that the "wrong" way won't work better in practice. ....
11-30-2006, 09:59 PM
#106
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This was asked on another forum and I posted some example calculations assuming inlet restrictor disk. Bleeding boost on compressor discharge is a waste IMO.
Just adding to the confusion… Oh, a disk in my opinion will add some in low boost applications but once you exceed say 12 PSI (to engine), I believe losses will outweigh benefit.
This portion covers pressure drop across various disks and varying mass flows:
Pipe = 4 inch ID and Disk = 3.75 inch opening
Pressure drop in PSI
10 lbs/min = 0.00, 26.53 ft/sec
20 lbs/min = 0.02, 53.05 ft/sec
30 lbs/min = 0.04, 79.58 ft/sec
40 lbs/min = 0.07, 106.10 ft/sec
50 lbs/min = 0.11, 132.63 ft/sec
60 lbs/min = 0.16, 159.16 ft/sec
70 lbs/min = 0.22, 185.68 ft/sec
80 lbs/min = 0.29, 212.21 ft/sec
Pipe = 4 inch ID and Disk = 3.5 inch opening
Pressure drop in PSI
10 lbs/min = 0.01
20 lbs/min = 0.04
30 lbs/min = 0.10
40 lbs/min = 0.18
50 lbs/min = 0.28
60 lbs/min = 0.41
70 lbs/min = 0.57
80 lbs/min = 0.76
Pipe = 4 inch ID and Disk = 3.25 inch opening
Pressure drop in PSI
10 lbs/min = 0.02
20 lbs/min = 0.08
30 lbs/min = 0.18
40 lbs/min = 0.32
50 lbs/min = 0.51
60 lbs/min = 0.75
70 lbs/min = 1.05
80 lbs/min = 1.41
Pipe = 4 inch ID and Disk = 3.00 inch opening
Pressure drop in PSI
10 lbs/min = 0.03
20 lbs/min = 0.13
30 lbs/min = 0.29
40 lbs/min = 0.53
50 lbs/min = 0.85
60 lbs/min = 1.27
70 lbs/min = 1.79
80 lbs/min = 2.47
80 lbs/min is approximately 800 FWHP…
Following is a oversimplified example of hit up top with disk:
So a stock LS1 pushing around 10 PSI will consume around 60 lbs/min with a pressure ratio of 1.68:1. To look at effect of restrictor disk, boost= PR*Actual_Inlet-14.7.
3 inch example;
1.68*(14.7-1.27)-14.7 or 7.86 PSI of boost
3.25 inch example;
1.68*(14.7-0.75)-14.7 or 8.74 PSI of boost
3.5 inch example;
1.68*(14.7-0.41)-14.7 or 9.31 PSI of boost
As can be observed from above restrictor disks are not that bad down in lower flow region and not much of a hit. It’s up top the drop becomes noticeable. With say a 3.5 inch disk blower can be increased a few 1000 RPMs and still make same boost, but part speed or cruising will improve.
Following is simple estimation of boost curve with various disks:
As mentioned above restrictor disks allow user to over-spin supercharger and put it in a more efficient operating range earlier, especially at lower boost levels (stock engine).
Below are calculations on a “theoretical” supercharger with constant efficiency (not so in real life) and that does not run out of steam up top. First boost column is with no disk, then other 4 are with varying disk sizes from 3.25 to 2.5 inch ID or passage.
The 2.75 inch disk at 4000 RPM showed a loss or dip in boost and did double check. Optimal values would take some testing but likely around 3 inch perhaps a bit less assuming 4 inch tube ID.
Engine RPM, Boost no disk, Boost 3.25, Boost 3.0, Boost 2.75, Boost 2.5
1000, 0.26 PSI, 0.26 PSI, 0.27 PSI, 0.30 PSI, 0.33 PSI
2000, 0.95 PSI, 0.97 PSI, 0.99 PSI, 1.11 PSI, 1.25 PSI
3000, 2.18 PSI, 2.23 PSI, 2.23 PSI, 2.55 PSI, 2.86 PSI
4000, 4.05 PSI, 4.14 PSI, 4.94 PSI, 4.66 PSI, 5.15 PSI
5000, 6.67 PSI, 6.75 PSI, 6.85 PSI, 7.43 PSI, 7.81 PSI
6000, 10.13 PSI, 10.13 PSI, 10.13 PSI. 10.13 PSI, 10.13 PSI
As can be seen from above at part speed (daily driving) flow is going to be increased more so then boost. Also in real life boost will taper off more up top then what my numbers indicate.
ATI/Procharger will act a little differently do to very little diffusion, but know Vortech and suspect Paxton will be somewhat close. Oh overdrive was about 29% from no disk to 2.5 inch restrictor and overdrive to 3 inch restrictor disk was about 10% again on paper.
Mike
Just adding to the confusion… Oh, a disk in my opinion will add some in low boost applications but once you exceed say 12 PSI (to engine), I believe losses will outweigh benefit.
This portion covers pressure drop across various disks and varying mass flows:
Pipe = 4 inch ID and Disk = 3.75 inch opening
Pressure drop in PSI
10 lbs/min = 0.00, 26.53 ft/sec
20 lbs/min = 0.02, 53.05 ft/sec
30 lbs/min = 0.04, 79.58 ft/sec
40 lbs/min = 0.07, 106.10 ft/sec
50 lbs/min = 0.11, 132.63 ft/sec
60 lbs/min = 0.16, 159.16 ft/sec
70 lbs/min = 0.22, 185.68 ft/sec
80 lbs/min = 0.29, 212.21 ft/sec
Pipe = 4 inch ID and Disk = 3.5 inch opening
Pressure drop in PSI
10 lbs/min = 0.01
20 lbs/min = 0.04
30 lbs/min = 0.10
40 lbs/min = 0.18
50 lbs/min = 0.28
60 lbs/min = 0.41
70 lbs/min = 0.57
80 lbs/min = 0.76
Pipe = 4 inch ID and Disk = 3.25 inch opening
Pressure drop in PSI
10 lbs/min = 0.02
20 lbs/min = 0.08
30 lbs/min = 0.18
40 lbs/min = 0.32
50 lbs/min = 0.51
60 lbs/min = 0.75
70 lbs/min = 1.05
80 lbs/min = 1.41
Pipe = 4 inch ID and Disk = 3.00 inch opening
Pressure drop in PSI
10 lbs/min = 0.03
20 lbs/min = 0.13
30 lbs/min = 0.29
40 lbs/min = 0.53
50 lbs/min = 0.85
60 lbs/min = 1.27
70 lbs/min = 1.79
80 lbs/min = 2.47
80 lbs/min is approximately 800 FWHP…
Following is a oversimplified example of hit up top with disk:
So a stock LS1 pushing around 10 PSI will consume around 60 lbs/min with a pressure ratio of 1.68:1. To look at effect of restrictor disk, boost= PR*Actual_Inlet-14.7.
3 inch example;
1.68*(14.7-1.27)-14.7 or 7.86 PSI of boost
3.25 inch example;
1.68*(14.7-0.75)-14.7 or 8.74 PSI of boost
3.5 inch example;
1.68*(14.7-0.41)-14.7 or 9.31 PSI of boost
As can be observed from above restrictor disks are not that bad down in lower flow region and not much of a hit. It’s up top the drop becomes noticeable. With say a 3.5 inch disk blower can be increased a few 1000 RPMs and still make same boost, but part speed or cruising will improve.
Following is simple estimation of boost curve with various disks:
As mentioned above restrictor disks allow user to over-spin supercharger and put it in a more efficient operating range earlier, especially at lower boost levels (stock engine).
Below are calculations on a “theoretical” supercharger with constant efficiency (not so in real life) and that does not run out of steam up top. First boost column is with no disk, then other 4 are with varying disk sizes from 3.25 to 2.5 inch ID or passage.
The 2.75 inch disk at 4000 RPM showed a loss or dip in boost and did double check. Optimal values would take some testing but likely around 3 inch perhaps a bit less assuming 4 inch tube ID.
Engine RPM, Boost no disk, Boost 3.25, Boost 3.0, Boost 2.75, Boost 2.5
1000, 0.26 PSI, 0.26 PSI, 0.27 PSI, 0.30 PSI, 0.33 PSI
2000, 0.95 PSI, 0.97 PSI, 0.99 PSI, 1.11 PSI, 1.25 PSI
3000, 2.18 PSI, 2.23 PSI, 2.23 PSI, 2.55 PSI, 2.86 PSI
4000, 4.05 PSI, 4.14 PSI, 4.94 PSI, 4.66 PSI, 5.15 PSI
5000, 6.67 PSI, 6.75 PSI, 6.85 PSI, 7.43 PSI, 7.81 PSI
6000, 10.13 PSI, 10.13 PSI, 10.13 PSI. 10.13 PSI, 10.13 PSI
As can be seen from above at part speed (daily driving) flow is going to be increased more so then boost. Also in real life boost will taper off more up top then what my numbers indicate.
ATI/Procharger will act a little differently do to very little diffusion, but know Vortech and suspect Paxton will be somewhat close. Oh overdrive was about 29% from no disk to 2.5 inch restrictor and overdrive to 3 inch restrictor disk was about 10% again on paper.
Mike
Last edited by Skunkworks; 11-30-2006 at 10:10 PM.
11-30-2006, 10:41 PM
#107
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I always appreciate a methodical and mathematical approach but the inducer id of a P1SC, D1SC and F1 is 3.37".
S trim -3.10"
T trim 3.29"
Novi 1500 3.29"
Novi 2000 3.50"
Novi 2200 3.49"
sorry for all the edits. I hosed the first post up and gathered some info.
S trim -3.10"
T trim 3.29"
Novi 1500 3.29"
Novi 2000 3.50"
Novi 2200 3.49"
sorry for all the edits. I hosed the first post up and gathered some info.
Last edited by andereck; 11-30-2006 at 10:50 PM.
11-30-2006, 10:59 PM
#108
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According to ProCharger’s site inducer for P1SC and D1SC is 3.37, F1 is 3.75 and F1R is 4.
My only point was when I looked at boost curves Vortech unit followed mathematically calculated curve almost perfectly from 2000 RPM on up. ProCharger did not, perhaps my guesstimate of efficiency was too far off.
Mike
My only point was when I looked at boost curves Vortech unit followed mathematically calculated curve almost perfectly from 2000 RPM on up. ProCharger did not, perhaps my guesstimate of efficiency was too far off.
Mike
11-30-2006, 11:13 PM
#109
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The F1 is a misprint as the inducer size is listed as the same as the inlet flange. The F1R spec is also incorrect and I believe its 3.75". My point was the 4" tube would be incorrect to base the restriction orifice off of as the inducers are much smaller in real life.
11-30-2006, 11:33 PM
#110
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Pipe = 3.50 inch ID, Disk passage = 2.85 inch ID
Pressure drop in PSI
10 lbs/min = 0.03, Loss = 0.01, 36.6 ft/sec (pipe), 56.3 ft/sec (disk)
20 lbs/min = 0.13, Loss = 0.04, 69.3 ft/sec (pipe), 104.5 ft/sec (disk)
30 lbs/min = 0.30, Loss = 0.09, 103.9 ft/sec (pipe), 156.8 ft/sec (disk)
40 lbs/min = 0.54, Loss = 0.16, 138.6 ft/sec (pipe), 209.0 ft/sec (disk)
50 lbs/min = 0.88, Loss = 0.27, 173.2 ft/sec (pipe), 261.3 ft/sec (disk)
60 lbs/min = 1.31, Loss = 0.40, 207.9 ft/sec (pipe), 313.5 ft/sec (disk)
70 lbs/min = 1.87
80 lbs/min = 2.60
313.5 ft/sec = about 214 MPH so you can understand pressure drop.
Following is close to 4 inch disk and 3 inch opening with respect to pressure drop. I originally picked that size because it works with some air filters. I can substitute just about any size and you do not want disk too close to impeller eye do to inlet pressure distortion issue.
Mike
---EDIT---
Look at F1R cutaway http://www.procharger.com/images/artwork/F1R_cut.jpg site may just be correct about inducer diameter, besides to flow those kind of numbers you need some decent passage height.
Pressure drop in PSI
10 lbs/min = 0.03, Loss = 0.01, 36.6 ft/sec (pipe), 56.3 ft/sec (disk)
20 lbs/min = 0.13, Loss = 0.04, 69.3 ft/sec (pipe), 104.5 ft/sec (disk)
30 lbs/min = 0.30, Loss = 0.09, 103.9 ft/sec (pipe), 156.8 ft/sec (disk)
40 lbs/min = 0.54, Loss = 0.16, 138.6 ft/sec (pipe), 209.0 ft/sec (disk)
50 lbs/min = 0.88, Loss = 0.27, 173.2 ft/sec (pipe), 261.3 ft/sec (disk)
60 lbs/min = 1.31, Loss = 0.40, 207.9 ft/sec (pipe), 313.5 ft/sec (disk)
70 lbs/min = 1.87
80 lbs/min = 2.60
313.5 ft/sec = about 214 MPH so you can understand pressure drop.
Following is close to 4 inch disk and 3 inch opening with respect to pressure drop. I originally picked that size because it works with some air filters. I can substitute just about any size and you do not want disk too close to impeller eye do to inlet pressure distortion issue.
Mike
---EDIT---
Look at F1R cutaway http://www.procharger.com/images/artwork/F1R_cut.jpg site may just be correct about inducer diameter, besides to flow those kind of numbers you need some decent passage height.
Last edited by Skunkworks; 11-30-2006 at 11:40 PM.
11-30-2006, 11:46 PM
#111
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Well a 50% increase in airspeed is something I would think you're going to hear. Somebody will just have to try it, and it won't be me until the snow and ices melts that was just dumped on us. I would hope that whoever trys it would also add an absolute pressure sensor after the restriction to verify pressure drop as well as post charger air temp.
11-30-2006, 11:49 PM
#112
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Originally Posted by Skunkworks
---EDIT---
Look at F1R cutaway http://www.procharger.com/images/artwork/F1R_cut.jpg site may just be correct about inducer diameter, besides to flow those kind of numbers you need some decent passage height.
Look at F1R cutaway http://www.procharger.com/images/artwork/F1R_cut.jpg site may just be correct about inducer diameter, besides to flow those kind of numbers you need some decent passage height.
The 4" restrictor OD is fine for assembly, you just don't want to base your area change on that dimension.
12-01-2006, 12:22 AM
#113
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Originally Posted by andereck
Well a 50% increase in airspeed is something I would think you're going to hear. Somebody will just have to try it, and it won't be me until the snow and ices melts that was just dumped on us. I would hope that whoever trys it would also add an absolute pressure sensor after the restriction to verify pressure drop as well as post charger air temp.
I need to say that one will come up on a point of diminishing returns very quickly if he/she gets greedy.
Mike
12-01-2006, 11:39 PM
#114
Allright, guys, I built the spreadsheet and calculated the theoretical hp to drive the blower and losses associated with pulleying up and restricting down. Here's the scoop:
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
12-02-2006, 06:53 AM
#117
Originally Posted by engineermike
Allright, guys, I built the spreadsheet and calculated the theoretical hp to drive the blower and losses associated with pulleying up and restricting down. Here's the scoop:
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
plus with an sd tun e you could have 14 psi just by taking the restrictor plate off!
thanks Chris.
12-02-2006, 11:22 AM
#119
It's not going to pick up 4 psi boost anywhere. As Skunkworks eluded to earlier. . .
If the base case boost curve is:
1000 2000 3000 4000 5000 6000 7000
1.4__2.9__4.3__5.7__7.1__8.6__10.0
Then you pulley up, the boost curve is:
1000 2000 3000 4000 5000 6000 7000
2.0__4.0__6.0__8.0__10.0_12.0_14.0
Now, you add a restrictor to bring the boost back down to 10 peak:
1000 2000 3000 4000 5000 6000 7000
1.9__3.7__5.3__6.7__8.0__9.1__10.0
Comparing the final boost curve to the base case, you retain 10 psi peak, which is the original goal, but get more boost in the midrange. The boost gain at 5000 rpm is only .9 psi and at 6000 rpm is only .5 psi. There will be inefficiency losses at these points also, though not quite as much as the 15 hp loss at peak. The net change will be a slight increase in the 2000 - 5000 rpm range (<1 psi worth) and a loss of 15 at peak.
Mike
If the base case boost curve is:
1000 2000 3000 4000 5000 6000 7000
1.4__2.9__4.3__5.7__7.1__8.6__10.0
Then you pulley up, the boost curve is:
1000 2000 3000 4000 5000 6000 7000
2.0__4.0__6.0__8.0__10.0_12.0_14.0
Now, you add a restrictor to bring the boost back down to 10 peak:
1000 2000 3000 4000 5000 6000 7000
1.9__3.7__5.3__6.7__8.0__9.1__10.0
Comparing the final boost curve to the base case, you retain 10 psi peak, which is the original goal, but get more boost in the midrange. The boost gain at 5000 rpm is only .9 psi and at 6000 rpm is only .5 psi. There will be inefficiency losses at these points also, though not quite as much as the 15 hp loss at peak. The net change will be a slight increase in the 2000 - 5000 rpm range (<1 psi worth) and a loss of 15 at peak.
Mike
12-02-2006, 03:21 PM
#120
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Originally Posted by engineermike
Allright, guys, I built the spreadsheet and calculated the theoretical hp to drive the blower and losses associated with pulleying up and restricting down. Here's the scoop:
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
Assumptions:
Inlet air is at 70 deg F
Inlet pressure is -.2 psi
Boost pressure in the intake is 10 psi
ATI doesn't publish their compressor efficiency maps, so I used the Vortech T-trim map - should be within a few percentage points.
Engine consumes 70 lb/min air
In the base case with no restrictor, the pressure ratio is 1.70. The efficiency is 66%. Outlet temperature ideal is 157 deg F, but with compressor inefficiency outlet temp is 202 deg F. This compressor takes 52 hp to drive.
Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold. The compressor pressure ratio is 1.98 and efficiency is actually a tad higher at 67%. Outlet temp ideal is 184 deg F, but with compressor inefficiency outlet temp is now 240 deg F. This compressor takes 67 hp to drive. Now, when you expand the 14 psi air back down to 10 psi, it cools off some, but you added extra heat to it because the compressor is only 67% efficient. So, when expanded, it won't cool all the way back down to the 202 deg outlet temp of the 10 psi compression calculated above. It will actually only cool off to 211 deg F.
SUMMARY
If you are running 10 psi base case and decide to pulley up to 14 psi, but add a restrictor to get it back down to 10 psi, then you will be giving up 15 hp plus whatever losses are associated with 10 deg hotter IAT's.
Mike
My problem is you say “Now, we pulley it up to 14 psi and restrict it back down to 10 psi in the manifold”. The restrictor is upstream not downstream or after blower. You are creating pressure drop to wheel eye or inlet not dropping pressure after air is already compressed and work has been done.
Rerun your numbers for inlet restriction and you will find losses are less then what you came up with. There is a point of diminishing returns when using this approach and should probably be limited to stock bottom ends. Once you go forged just crank up the blower.
As far as boost curve look at http://www.kennebell.net/media/artic...TBASHpart2.pdf Page # 6 and compare against your curve. Centrifugals do not come up as aggressively as your example at part speed, it looks more like an axial flow compressor curve.
My base curve I think is closer in real life.
Oh, centrifugal boost curve is exponential not linear (most wish it was linear).Mike
Last edited by Skunkworks; 12-02-2006 at 04:12 PM.