skav said:
What makes the Whipple/screw more efficient than a roots straight lobe? Is it just a newer, better design? Both are available with intercoolers so heat shouldn't be an issue. Would it be correct to call a roots setup "old school"?
I get the whole efi computer deal. My Whipple and mefi is super mellow-if that's the right way to describe it.
It always fires right up and idles at 850 with no surge.
Read more
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Screw Superchargers are actually an air compressor which is more adiabatic efficient than a Roots Supercharger. A Roots supercharger, which most originated from a 2 stroke diesel engine, typically a Detroit ie; 8-71 (8 cylinder, 71 cubic inches per cylinder). Centrifugal superchargers are kind of a cross breed between turbos and Screw or Roots Superchargers. All of these are mechanically driven.
Turbo Chargers work primarily on the Radiant Heat/Expansion of exhaust gases not so much exhaust pressure or back pressure. In a Diesel engine they work perfectly. However with a gasoline engine they can cause a snowball effect once the engine fuel/air ratio goes lean as it will case more radiant exhaust heat which will spool the turbo to make more boost which will only further lean the engine, and so on.
All types of supercharging used to increase the volumetric efficiency of the engine which will raise the power output or Brake Means Effective Pressure.
Here are a couple of links that you should find interesting. All of them are pretty basic and short reads but will give you a better understanding of what you are asking about.
Hope this helps.
http://www.superchargersonline.com/index.php?main_page=page&id=12
https://en.wikipedia.org/wiki/Turbocharger
http://kennebell.net/KBWebsite/Common/pdfs/SC_efficiency.pdf
Screw Superchargers are actually an air compressor which is more adiabatic efficient than a Roots Supercharger. A Roots supercharger, which most originated from a 2 stroke diesel engine, typically a Detroit ie; 8-71 (8 cylinder, 71 cubic inches per cylinder). Centrifugal superchargers are kind of a cross breed between turbos and Screw or Roots Superchargers. All of these are mechanically driven.Turbo Chargers work primarily on the Radiant Heat/Expansion of exhaust gases not so much exhaust pressure or back pressure. In a Diesel engine they work perfectly. However with a gasoline engine they can cause a snowball effect once the engine fuel/air ratio goes lean as it will case more radiant exhaust heat which will spool the turbo to make more boost which will only further lean the engine, and so on.All types of supercharging used to increase the volumetric efficiency of the engine which will raise the power output or Brake Means Effective Pressure.Here are a couple of links that you should find interesting. All of them are pretty basic and short reads but will give you a better understanding of what you are asking about.Hope this helps.
Guessing!
In my 20 years of RACING & dyno testing (with my engines) with Roots Blowers I have run 3 sizes of blowers, aluminum & steel heads, one carb & 2 carbs, roller & hydraulic camshafts and different engine timing. Boost or what a boost gauge reads largely depends on one (1) thing........ fuel mixture into and exhaust out of the engine "period". You can have the BEST flowing heads & Camshaft with small 1 1/2"heads through and stock exhaust system and you boost numbers will be high as hell with zip for power after RPM's (R'sPM) same goes for the camshaft, good flowing heads with a small camshaft and large tube headers with no exhaust system. B & M had a GREAT (if not the BEST) Supercharging book out when they were into blowers the easiest to understand and read, I learned a lot from that book. They showed a small block Cheby & Drof engines with different size blowers, cams, heads & headers on the dyno, you saw exactly (with graphs) what happened to the HP & torque with different combinations......................GREAT book (I still have it).
With steel heads (6X) and a small hydraulic camshaft with 1 3/4" headers (no exhaust) I could run half racing fuel and half regular gas with no problems if I keeped my boost in the single digits (Never hurt my motor). With the same blower (B & M 174 Street Charger) and E-Heads (87 CC) with a roller camshaft I ran 110 racing fuel and picked up 1/2 second in my E.T. the interesting thing was my boost number dropped down from 7-8 lbs. of boost to 3 1/2 lbs. of boost (better flowing heads & camshaft). Now on the dyno I ran the same combo) engine, heads & camshaft) with a B & M 250 Street Charger (it's a little smaller then a 4-71) I picked up 38+ HP (max 698 to 742) all through my engines RPM range switching from one (1) dominator to two (2) dominators (it's an air flow thing). Remember if you can't suck it in your not going to make horse power and your boost numbers will be low. In the timing issue I tried timing from 28 degrees to 36 and my engine always made more power (ran quicker) with 34 degrees timing, funny thing the B & M book showed the same thing. in the exhaust department I pick up .2 (8.90's to 8.70's) of a second (8-71 blower) going from 2 " headers conventional headers to 2 1/4" zoomies (no matter how much fuel mixture your blower shoves in your engine if you can't get the exhaust gases out your HP numbers will be lower...........my engines boost numbers also dropped a little).
Lets face it with a stock block you DON'T want to go over 750 HP anyways (unless you have an engine diaper) so keep the boost numbers between 6-8 lbs. (under drive the blower), timing at 34 degrees or less and 110 racing fuel (while racing it) and you shouldn't have any problems with the E-heads and engine. Remember think small first until you get a handle on your combo!
GTO George
Am I missing something? Nowhere in this thread does it say how big a camshaft he is running or how large the headers are or if he will race with his exhaust system hooked up or what. How can anyone predict/guess what kind of boost numbers he will have at a certain over or under drive on the blower.In my 20 years of RACING & dyno testing (with my engines) with Roots Blowers I have run 3 sizes of blowers, aluminum & steel heads, one carb & 2 carbs, roller & hydraulic camshafts and different engine timing. Boost or what a boost gauge reads largely depends on one (1) thing........ fuel mixture into and exhaust out of the engine "period". You can have the BEST flowing heads & Camshaft with small 1 1/2"heads through and stock exhaust system and you boost numbers will be high as hell with zip for power after RPM's (R'sPM) same goes for the camshaft, good flowing heads with a small camshaft and large tube headers with no exhaust system. B & M had a GREAT (if not the BEST) Supercharging book out when they were into blowers the easiest to understand and read, I learned a lot from that book. They showed a small block Cheby & Drof engines with different size blowers, cams, heads & headers on the dyno, you saw exactly (with graphs) what happened to the HP & torque with different combinations......................GREAT book (I still have it).With steel heads (6X) and a small hydraulic camshaft with 1 3/4" headers (no exhaust) I could run half racing fuel and half regular gas with no problems if I keeped my boost in the single digits (Never hurt my motor). With the same blower (B & M 174 Street Charger) and E-Heads (87 CC) with a roller camshaft I ran 110 racing fuel and picked up 1/2 second in my E.T. the interesting thing was my boost number dropped down from 7-8 lbs. of boost to 3 1/2 lbs. of boost (better flowing heads & camshaft). Now on the dyno I ran the same combo) engine, heads & camshaft) with a B & M 250 Street Charger (it's a little smaller then a 4-71) I picked up 38+ HP (max 698 to 742) all through my engines RPM range switching from one (1) dominator to two (2) dominators (it's an air flow thing). Remember if you can't suck it in your not going to make horse power and your boost numbers will be low. In the timing issue I tried timing from 28 degrees to 36 and my engine always made more power (ran quicker) with 34 degrees timing, funny thing the B & M book showed the same thing. in the exhaust department I pick up .2 (8.90's to 8.70's) of a second (8-71 blower) going from 2 " headers conventional headers to 2 1/4" zoomies (no matter how much fuel mixture your blower shoves in your engine if you can't get the exhaust gases out your HP numbers will be lower...........my engines boost numbers also dropped a little).Lets face it with a stock block you DON'T want to go over 750 HP anyways (unless you have an engine diaper) so keep the boost numbers between 6-8 lbs. (under drive the blower), timing at 34 degrees or less and 110 racing fuel (while racing it) and you shouldn't have any problems with the E-heads and engine. Remember think small first until you get a handle on your combo!GTO George
If you want to learn more, please visit our website Benyuan.
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Roots vs screw? And blower vs turbo questions
skav said:
What makes the Whipple/screw more efficient than a roots straight lobe? Is it just a newer, better design? Both are available with intercoolers so heat shouldn't be an issue. Would it be correct to call a roots setup "old school"?
I get the whole efi computer deal. My Whipple and mefi is super mellow-if that's the right way to describe it.
It always fires right up and idles at 850 with no surge.
Click to expand...
Screw Superchargers are actually an air compressor which is more adiabatic efficient than a Roots Supercharger. A Roots supercharger, which most originated from a 2 stroke diesel engine, typically a Detroit ie; 8-71 (8 cylinder, 71 cubic inches per cylinder). Centrifugal superchargers are kind of a cross breed between turbos and Screw or Roots Superchargers. All of these are mechanically driven.
Turbo Chargers work primarily on the Radiant Heat/Expansion of exhaust gases not so much exhaust pressure or back pressure. In a Diesel engine they work perfectly. However with a gasoline engine they can cause a snowball effect once the engine fuel/air ratio goes lean as it will case more radiant exhaust heat which will spool the turbo to make more boost which will only further lean the engine, and so on.
All types of supercharging used to increase the volumetric efficiency of the engine which will raise the power output or Brake Means Effective Pressure.
Here are a couple of links that you should find interesting. All of them are pretty basic and short reads but will give you a better understanding of what you are asking about.
Hope this helps.
http://www.superchargersonline.com/index.php?main_page=page&id=12
https://en.wikipedia.org/wiki/Turbocharger
http://kennebell.net/KBWebsite/Common/pdfs/SC_efficiency.pdf
Screw Superchargers are actually an air compressor which is more adiabatic efficient than a Roots Supercharger. A Roots supercharger, which most originated from a 2 stroke diesel engine, typically a Detroit ie; 8-71 (8 cylinder, 71 cubic inches per cylinder). Centrifugal superchargers are kind of a cross breed between turbos and Screw or Roots Superchargers. All of these are mechanically driven.Turbo Chargers work primarily on the Radiant Heat/Expansion of exhaust gases not so much exhaust pressure or back pressure. In a Diesel engine they work perfectly. However with a gasoline engine they can cause a snowball effect once the engine fuel/air ratio goes lean as it will case more radiant exhaust heat which will spool the turbo to make more boost which will only further lean the engine, and so on.All types of supercharging used to increase the volumetric efficiency of the engine which will raise the power output or Brake Means Effective Pressure.Here are a couple of links that you should find interesting. All of them are pretty basic and short reads but will give you a better understanding of what you are asking about.Hope this helps.
Roots BlowerRoots Blower Boost questions
Guessing!
In my 20 years of RACING & dyno testing (with my engines) with Roots Blowers I have run 3 sizes of blowers, aluminum & steel heads, one carb & 2 carbs, roller & hydraulic camshafts and different engine timing. Boost or what a boost gauge reads largely depends on one (1) thing........ fuel mixture into and exhaust out of the engine "period". You can have the BEST flowing heads & Camshaft with small 1 1/2"heads through and stock exhaust system and you boost numbers will be high as hell with zip for power after RPM's (R'sPM) same goes for the camshaft, good flowing heads with a small camshaft and large tube headers with no exhaust system. B & M had a GREAT (if not the BEST) Supercharging book out when they were into blowers the easiest to understand and read, I learned a lot from that book. They showed a small block Cheby & Drof engines with different size blowers, cams, heads & headers on the dyno, you saw exactly (with graphs) what happened to the HP & torque with different combinations......................GREAT book (I still have it).
With steel heads (6X) and a small hydraulic camshaft with 1 3/4" headers (no exhaust) I could run half racing fuel and half regular gas with no problems if I keeped my boost in the single digits (Never hurt my motor). With the same blower (B & M 174 Street Charger) and E-Heads (87 CC) with a roller camshaft I ran 110 racing fuel and picked up 1/2 second in my E.T. the interesting thing was my boost number dropped down from 7-8 lbs. of boost to 3 1/2 lbs. of boost (better flowing heads & camshaft). Now on the dyno I ran the same combo) engine, heads & camshaft) with a B & M 250 Street Charger (it's a little smaller then a 4-71) I picked up 38+ HP (max 698 to 742) all through my engines RPM range switching from one (1) dominator to two (2) dominators (it's an air flow thing). Remember if you can't suck it in your not going to make horse power and your boost numbers will be low. In the timing issue I tried timing from 28 degrees to 36 and my engine always made more power (ran quicker) with 34 degrees timing, funny thing the B & M book showed the same thing. in the exhaust department I pick up .2 (8.90's to 8.70's) of a second (8-71 blower) going from 2 " headers conventional headers to 2 1/4" zoomies (no matter how much fuel mixture your blower shoves in your engine if you can't get the exhaust gases out your HP numbers will be lower...........my engines boost numbers also dropped a little).
Lets face it with a stock block you DON'T want to go over 750 HP anyways (unless you have an engine diaper) so keep the boost numbers between 6-8 lbs. (under drive the blower), timing at 34 degrees or less and 110 racing fuel (while racing it) and you shouldn't have any problems with the E-heads and engine. Remember think small first until you get a handle on your combo!
GTO George
Am I missing something? Nowhere in this thread does it say how big a camshaft he is running or how large the headers are or if he will race with his exhaust system hooked up or what. How can anyone predict/guess what kind of boost numbers he will have at a certain over or under drive on the blower.In my 20 years of RACING & dyno testing (with my engines) with Roots Blowers I have run 3 sizes of blowers, aluminum & steel heads, one carb & 2 carbs, roller & hydraulic camshafts and different engine timing. Boost or what a boost gauge reads largely depends on one (1) thing........ fuel mixture into and exhaust out of the engine "period". You can have the BEST flowing heads & Camshaft with small 1 1/2"heads through and stock exhaust system and you boost numbers will be high as hell with zip for power after RPM's (R'sPM) same goes for the camshaft, good flowing heads with a small camshaft and large tube headers with no exhaust system. B & M had a GREAT (if not the BEST) Supercharging book out when they were into blowers the easiest to understand and read, I learned a lot from that book. They showed a small block Cheby & Drof engines with different size blowers, cams, heads & headers on the dyno, you saw exactly (with graphs) what happened to the HP & torque with different combinations......................GREAT book (I still have it).With steel heads (6X) and a small hydraulic camshaft with 1 3/4" headers (no exhaust) I could run half racing fuel and half regular gas with no problems if I keeped my boost in the single digits (Never hurt my motor). With the same blower (B & M 174 Street Charger) and E-Heads (87 CC) with a roller camshaft I ran 110 racing fuel and picked up 1/2 second in my E.T. the interesting thing was my boost number dropped down from 7-8 lbs. of boost to 3 1/2 lbs. of boost (better flowing heads & camshaft). Now on the dyno I ran the same combo) engine, heads & camshaft) with a B & M 250 Street Charger (it's a little smaller then a 4-71) I picked up 38+ HP (max 698 to 742) all through my engines RPM range switching from one (1) dominator to two (2) dominators (it's an air flow thing). Remember if you can't suck it in your not going to make horse power and your boost numbers will be low. In the timing issue I tried timing from 28 degrees to 36 and my engine always made more power (ran quicker) with 34 degrees timing, funny thing the B & M book showed the same thing. in the exhaust department I pick up .2 (8.90's to 8.70's) of a second (8-71 blower) going from 2 " headers conventional headers to 2 1/4" zoomies (no matter how much fuel mixture your blower shoves in your engine if you can't get the exhaust gases out your HP numbers will be lower...........my engines boost numbers also dropped a little).Lets face it with a stock block you DON'T want to go over 750 HP anyways (unless you have an engine diaper) so keep the boost numbers between 6-8 lbs. (under drive the blower), timing at 34 degrees or less and 110 racing fuel (while racing it) and you shouldn't have any problems with the E-heads and engine. Remember think small first until you get a handle on your combo!GTO George
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