F1r on an LT1
Moderator
Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Re: F1r on an LT1
You need to start with "how big a blower do I need". A decent SBC stroker with a D1 will be in the 600rwhp range, an F1 in the 675-700 range and the F1R 800-900rwhp. More or less depending on the combo, but those are typical numbers. Keep in mind that it takes a lot of fiddling to get a maxed out F1 to run reliably on pump gas, and I would say it's not possible with an F1R. Of course, you could always pulley a blower down, but why bother to mount and drive a bigger blower than you need to?
Overall, I think the F1R wouldn't be an optimal blower for a stroker small block Chev in the vast majority of cases. Too much boost for pump fuel/street use and not enough boost/airflowfor an all-out race car with the added fitment issues. I have a buddy using one, but his motor is a small Ford stroker (331ci) and his car is a lot lighter than a 4th gen (~3,100lbs). So, he can get to his goal (running high 8's) with "just" 800-900rwhp.
A motor that is ~20% bigger is going to need ~20% more airflow, all else being equal. Something on the order of an F2 (2,700CFM) would be the smallest I would consider on a 383/396 race setup, not the F1R. For 99.9% of us, the D1 is a good choice.
Rich
Overall, I think the F1R wouldn't be an optimal blower for a stroker small block Chev in the vast majority of cases. Too much boost for pump fuel/street use and not enough boost/airflowfor an all-out race car with the added fitment issues. I have a buddy using one, but his motor is a small Ford stroker (331ci) and his car is a lot lighter than a 4th gen (~3,100lbs). So, he can get to his goal (running high 8's) with "just" 800-900rwhp.
A motor that is ~20% bigger is going to need ~20% more airflow, all else being equal. Something on the order of an F2 (2,700CFM) would be the smallest I would consider on a 383/396 race setup, not the F1R. For 99.9% of us, the D1 is a good choice.
Rich
Registered User
Joined: Mar 2005
Posts: 849
From: Shawnee Kansas
Re: F1r on an LT1
This may have been discussed here before and if so consider it a refresher. The "boost" or density potential of a supercharger is based on the cfm potential of the blower divided by the engine with atmospheric pressure removed.
((BlowerCFM/EngineCFM)*AtmospericPSI)-AtmosphericPSI=PotentialBoost Available.
The max CFM listed for centrifugals occurs near the listed redline of the blower.
Most centrifugals produce boost at the rate of 4 times the boost at double the blower rpm.
The formula for engine CFM is:
((CID*RPM)/3456)*VE%
So you can figure a stock engine has a VE% of about 85-90% at peak torque depending on the engine. LT1's and LS1's have a higher VE% than a Gen1 sbc due to the cylinder head and intake design so a given blower and ratio will show less "boost" on a better breathing engine because less air backs up in the intake.
By comparison a 500 in. prostock engine has a VE% of 115-118% at peak power.
Every 15psi of intercooled air will virtually double your engine size or power potential. Big gains can be had because internal engine friction remains virtually the same regardless of the added boost. Parasitic drag of the blower increases with pumping potential (blower size) but it is still a winning proposition. There is also a gain in pumping efficiency because the blower pressure assists engine rotation by applying force to the piston top. So while the blower requires real torque to operate it gives back in reduced pumping losses. This cannot be said of the turbocharger due to increased exhaust back pressure that is typically twice the boost pressure.
There are very fast cars using both technologies, but the blower is almost always a less expensive approach and an easier install that gets you to the track quicker.
Back on topic a centrifugal is most efficient near its max rated rpm. Buying more blower than you need may cost you performance. Decide on a power level and base your decision upon that. A common agreed formula for power is 1.5-1.6 cfm per HP.
Gear the blower to provide the airflow you need while keeping the blower below redline and allow for a missed shift or broken driveline component. Blowers are durable and can easily be sold at a later date if you desire an upgrade due to a new combination. Some superchargers may be upgraded at the factory to a different performance level if you desire. This is generally true if the diameter of the volute doesn't change betrween levels.
Happy boosting!!
((BlowerCFM/EngineCFM)*AtmospericPSI)-AtmosphericPSI=PotentialBoost Available.
The max CFM listed for centrifugals occurs near the listed redline of the blower.
Most centrifugals produce boost at the rate of 4 times the boost at double the blower rpm.
The formula for engine CFM is:
((CID*RPM)/3456)*VE%
So you can figure a stock engine has a VE% of about 85-90% at peak torque depending on the engine. LT1's and LS1's have a higher VE% than a Gen1 sbc due to the cylinder head and intake design so a given blower and ratio will show less "boost" on a better breathing engine because less air backs up in the intake.
By comparison a 500 in. prostock engine has a VE% of 115-118% at peak power.
Every 15psi of intercooled air will virtually double your engine size or power potential. Big gains can be had because internal engine friction remains virtually the same regardless of the added boost. Parasitic drag of the blower increases with pumping potential (blower size) but it is still a winning proposition. There is also a gain in pumping efficiency because the blower pressure assists engine rotation by applying force to the piston top. So while the blower requires real torque to operate it gives back in reduced pumping losses. This cannot be said of the turbocharger due to increased exhaust back pressure that is typically twice the boost pressure.
There are very fast cars using both technologies, but the blower is almost always a less expensive approach and an easier install that gets you to the track quicker.
Back on topic a centrifugal is most efficient near its max rated rpm. Buying more blower than you need may cost you performance. Decide on a power level and base your decision upon that. A common agreed formula for power is 1.5-1.6 cfm per HP.
Gear the blower to provide the airflow you need while keeping the blower below redline and allow for a missed shift or broken driveline component. Blowers are durable and can easily be sold at a later date if you desire an upgrade due to a new combination. Some superchargers may be upgraded at the factory to a different performance level if you desire. This is generally true if the diameter of the volute doesn't change betrween levels.
Happy boosting!!
Last edited by markinkc69z; Oct 6, 2005 at 09:22 PM.
Registered User
Joined: Feb 2001
Posts: 946
From: Lees Summit, MO
Re: F1r on an LT1
Originally Posted by markinkc69z
This may have been discussed here before and if so consider it a refresher. The "boost" or density potential of a supercharger is based on the cfm potential of the blower divided by the engine with atmospheric pressure removed.
((BlowerCFM/EngineCFM)*AtmospericPSI)-AtmosphericPSI=PotentialBoost Available.
The max CFM listed for centrifugals occurs near the listed redline of the blower.
Most centrifugals produce boost at the rate of 4 times the boost at double the blower rpm.
The formula for engine CFM is:
((CID*RPM)/3456)*VE%
So you can figure a stock engine has a VE% of about 85-90% at peak torque depending on the engine. LT1's and LS1's have a higher VE% than a Gen1 sbc due to the cylinder head and intake design so a given blower and ratio will show less "boost" on a better breathing engine because less air backs up in the intake.
By comparison a 500 in. prostock engine has a VE% of 115-118% at peak power.
Every 15psi of intercooled air will virtually double your engine size or power potential. Big gains can be had because internal engine friction remains virtually the same regardless of the added boost. Parasitic drag of the blower increases with pumping potential (blower size) but it is still a winning proposition. There is also a gain in pumping efficiency because the blower pressure assists engine rotation by applying force to the piston top. So while the blower requires real torque to operate it gives back in reduced pumping losses. This cannot be said of the turbocharger due to increased exhaust back pressure that is typically twice the boost pressure.
There are very fast cars using both technologies, but the blower is almost always a less expensive approach and an easier install that gets you to the track quicker.
Back on topic a centrifugal is most efficient near its max rated rpm. Buying more blower than you need may cost you performance. Decide on a power level and base your decision upon that. A common agreed formula for power is 1.5-1.6 cfm per HP.
Gear the blower to provide the airflow you need while keeping the blower below redline and allow for a missed shift or broken driveline component. Blowers are durable and can easily be sold at a later date if you desire an upgrade due to a new combination. Some superchargers may be upgraded at the factory to a different performance level if you desire. This is generally true if the diameter of the volute doesn't change betrween levels.
Happy boosting!!
((BlowerCFM/EngineCFM)*AtmospericPSI)-AtmosphericPSI=PotentialBoost Available.
The max CFM listed for centrifugals occurs near the listed redline of the blower.
Most centrifugals produce boost at the rate of 4 times the boost at double the blower rpm.
The formula for engine CFM is:
((CID*RPM)/3456)*VE%
So you can figure a stock engine has a VE% of about 85-90% at peak torque depending on the engine. LT1's and LS1's have a higher VE% than a Gen1 sbc due to the cylinder head and intake design so a given blower and ratio will show less "boost" on a better breathing engine because less air backs up in the intake.
By comparison a 500 in. prostock engine has a VE% of 115-118% at peak power.
Every 15psi of intercooled air will virtually double your engine size or power potential. Big gains can be had because internal engine friction remains virtually the same regardless of the added boost. Parasitic drag of the blower increases with pumping potential (blower size) but it is still a winning proposition. There is also a gain in pumping efficiency because the blower pressure assists engine rotation by applying force to the piston top. So while the blower requires real torque to operate it gives back in reduced pumping losses. This cannot be said of the turbocharger due to increased exhaust back pressure that is typically twice the boost pressure.
There are very fast cars using both technologies, but the blower is almost always a less expensive approach and an easier install that gets you to the track quicker.
Back on topic a centrifugal is most efficient near its max rated rpm. Buying more blower than you need may cost you performance. Decide on a power level and base your decision upon that. A common agreed formula for power is 1.5-1.6 cfm per HP.
Gear the blower to provide the airflow you need while keeping the blower below redline and allow for a missed shift or broken driveline component. Blowers are durable and can easily be sold at a later date if you desire an upgrade due to a new combination. Some superchargers may be upgraded at the factory to a different performance level if you desire. This is generally true if the diameter of the volute doesn't change betrween levels.
Happy boosting!!
Thread
Thread Starter
Forum
Replies
Last Post
oldschool
Parts For Sale
16
Feb 9, 2016 09:21 PM