Re: Building a Procharged 6.1
[Re: FastmOp]
#3118651
02/03/23 04:02 PM
02/03/23 04:02 PM
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Joined: Aug 2003
Posts: 43,129 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,129
Bend,OR USA
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Measure what you have and do the math I wouldn't raise the compression ratio unless it is less than 7.5 to 1 ratio or worse, I would use the blow off valve, valves, to control the HP based on boost I am new to racing a supercharged motor so what do I know
Last edited by Cab_Burge; 02/03/23 04:03 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Building a Procharged 6.1
[Re: Dart 500]
#3118899
02/04/23 04:42 PM
02/04/23 04:42 PM
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Joined: Aug 2003
Posts: 43,129 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,129
Bend,OR USA
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I would verify the actual, not factory specs,. true compression ratio that motor actually has and go from there. Aren't all the 6.1 Hemi 10.0 to 1 or more stock? The last pump gas street Hemi motor I built for a customer had right at 9.3 to 1 true mechanical compression ratio, it had a Litlefield 10:71 roots blower on it with two Carb Shop built Dominatoer carbs that were around 1050 CFM at 28.5 inches. That motor 927 HP at 7300 RPM with CA pump swill at 7.5 lbs. of boost at 12.0 percent underdriven with 33 degrees total timing using a MSD 7AL2 ignition, we switch the pulleys which made it have 13 percent overdrive and we retarded the timing to 25 degrees BTDC total and swap to Union 76 race gas with 116 octane and that motor made 1027 HP at 6500 RPM with 12.0 lbs. boost before starting to detonate and miss My point is that motor drove on the street a lot better than another pump gas blown Hemi motor for another customer that had less compression ratio and sped up the blower to make more power on the street. Most street driving is around or under 2500 RPM in town at light part throttle so that makes the low RPM throttle response important
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Building a Procharged 6.1
[Re: FastmOp]
#3118916
02/04/23 07:24 PM
02/04/23 07:24 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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A centrifugal blower has minimal boost until higher RPM, compared to a Roots or axial type. The psi varies (roughly) with RPM^2: 5 psi @ 2,000 becomes 45 psi @ 6,000. Without high stall (or a strong 1st gear) the car won't launch, and higher static CR will help, but what to do about spark at higher PSI level? MSD retard? Water injection? Be careful. I'm going to try Snow on my turbo engine, now safe @ 17 psi, to see if leaner mixture or more spark will pick up some power.
Boffin Emeritus
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