GRUMPY????
I have a 383 SBC which according to the builder has; speed pro hypereutectic pistons with a 9.9:1 comp, eagle crank, Vortec aluminum head back-cut 2.0/1.55 1.25 springs, a cam with a 110 center-line 488-490 lift corrected 1.6 ratio 226/228dur@050. I have also added a TPI with 58 Throttle body and 36 lbs injectors. I would really like to install a paxton SN92 supercharger that I was going to use in a previous engine. Everything that I read on SC seems to point a comp of about 8.5 and not 9.9.. So can I / should I proceed with the installation, and expect to successfully run enough boost to make a significant improvement in power levels
thats a great question, so Ill take a few seconds to post you some linked info and do a basic calculation
youll want to run a DYNAMIC compression of about 8:1 to avoid detonation with pump octane fuel
with 9.9:1 static compression , and your current cam,timing, and your current effective dynamic compression ratio even with only a modest 5 psi boost will require race octane fuel or you'll quickly get into engine destroying detonation unless you use some method to cool the combustion like an alcohol/water injection system and octane boosters in the gas plus a ignition retard under boost , it would be cheaper and easier to build a rotating assembly with a FORGED piston and about a 7.8:1 static compression ratio if your intention is to maximize the superchargers effect on your 383 sbc build as hypereutectic pistons with 9.9:1 static compression will more than likely result in problems once the superchargers boost is used.
if you have easy access to E85 fuel and your willing to do the required mods to the fuel system to run E85 the increased octane will make it easier to run high compression and boost from a supercharger , but youll generally need to run about 50% more fuel thru the engine because ethanol alcohol had a higher octane but less BTUs so you need to run about 1.5 times more to produce the higher hp levels
theres a great deal of related info in these threads, yes I,m fully aware theres a great deal of info to read thru but if you want to understand what the limitations are and what the probable results will be, its worth, taking the time and effort to do so!
http://www.wallaceracing.com/dynamic-cr.php
http://autocalc.onlinedyno.com/compress ... 9&afr=12.7
http://www.rbracing-rsr.com/compression.htm
http://horsepowercalculators.net/e85-ca ... calculator
http://www.wallaceracing.com/boost-comp ... o-calc.php
http://www.dragsource.com/index.php?nav ... ctoview=3#
viewtopic.php?f=55&t=2718
viewtopic.php?f=86&t=1894
viewtopic.php?f=86&t=4634
viewtopic.php?f=52&t=727
viewtopic.php?f=52&t=1070
viewtopic.php?f=52&t=4299&p=11332#p11332
viewtopic.php?f=86&t=1330
viewtopic.php?f=86&t=4484&p=11815&hilit=alcohol+water#p11815
viewtopic.php?f=86&t=1329&p=8354&hilit=alcohol+water#p8354
I have a 383 SBC which according to the builder has; speed pro hypereutectic pistons with a 9.9:1 comp, eagle crank, Vortec aluminum head back-cut 2.0/1.55 1.25 springs, a cam with a 110 center-line 488-490 lift corrected 1.6 ratio 226/228dur@050. I have also added a TPI with 58 Throttle body and 36 lbs injectors. I would really like to install a paxton SN92 supercharger that I was going to use in a previous engine. Everything that I read on SC seems to point a comp of about 8.5 and not 9.9.. So can I / should I proceed with the installation, and expect to successfully run enough boost to make a significant improvement in power levels
thats a great question, so Ill take a few seconds to post you some linked info and do a basic calculation
youll want to run a DYNAMIC compression of about 8:1 to avoid detonation with pump octane fuel
with 9.9:1 static compression , and your current cam,timing, and your current effective dynamic compression ratio even with only a modest 5 psi boost will require race octane fuel or you'll quickly get into engine destroying detonation unless you use some method to cool the combustion like an alcohol/water injection system and octane boosters in the gas plus a ignition retard under boost , it would be cheaper and easier to build a rotating assembly with a FORGED piston and about a 7.8:1 static compression ratio if your intention is to maximize the superchargers effect on your 383 sbc build as hypereutectic pistons with 9.9:1 static compression will more than likely result in problems once the superchargers boost is used.
if you have easy access to E85 fuel and your willing to do the required mods to the fuel system to run E85 the increased octane will make it easier to run high compression and boost from a supercharger , but youll generally need to run about 50% more fuel thru the engine because ethanol alcohol had a higher octane but less BTUs so you need to run about 1.5 times more to produce the higher hp levels
theres a great deal of related info in these threads, yes I,m fully aware theres a great deal of info to read thru but if you want to understand what the limitations are and what the probable results will be, its worth, taking the time and effort to do so!
http://www.wallaceracing.com/dynamic-cr.php
http://autocalc.onlinedyno.com/compress ... 9&afr=12.7
http://www.rbracing-rsr.com/compression.htm
http://horsepowercalculators.net/e85-ca ... calculator
http://www.wallaceracing.com/boost-comp ... o-calc.php
http://www.dragsource.com/index.php?nav ... ctoview=3#
viewtopic.php?f=55&t=2718
viewtopic.php?f=86&t=1894
viewtopic.php?f=86&t=4634
viewtopic.php?f=52&t=727
viewtopic.php?f=52&t=1070
viewtopic.php?f=52&t=4299&p=11332#p11332
viewtopic.php?f=86&t=1330
viewtopic.php?f=86&t=4484&p=11815&hilit=alcohol+water#p11815
viewtopic.php?f=86&t=1329&p=8354&hilit=alcohol+water#p8354