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when does the boost come on

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  • PackardV8
    replied
    Paxton supercharger boost is multi-variable-regressive equation. It depends on a complex relationship between RPM, throttle opening and load. It has very little to do with rear gear ratio.

    1. Rev it to 5,000 RPM in neutral and very little boost.
    2. Open the throttle full in any gear at 2,000 and very little boost.
    3. Hold full throttle in any gear from 3,500 to 5,000 and it should show boost rising from about 1-2 PSI to maybe 5 PSI.
    4. FWIW, very few stock R2s show a real 5 PSI. Unless there are new valve springs shimmed to high end of recommended seat pressure and a recent valve job, most R2s will float the valves between 4,500 and 5,000.
    5. Avanti tachometers and vacuum/pressure gauges are notoriously inaccurate. Don't believe anything they say.

    thnx, jack vines

    PackardV8

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  • 59r2
    replied

    Good point Dick
    -The 3.08 gears are only temp. Ihave a 66 rear flanged axle rear I am fixing now with 3.31's . The car flys and time between shifts is secounds. The gears in the t-10 must be close ratio because there is only a 1200 rpm drop. I am happy with the power and sound. I was told boost is proportional to load, by the way it moves maybe the weigh isn't giving the engine to much fight.Although an avanti should be lighter?Anyway I was asking for someone else experience with an r-2 when and how their boost was? The engine is vin number R-1984 originally an r-1 with high compression heads ,dished 9.8 -1 hyper pistons punched out 40 over with a r-2 cam, ported and polished heads ,stock 289 manifolds with avanti straight thur quiet-tone mufflers.I am usaully ready to shift before the weighted butterflies open.
    JOE

    1959 HARDTOP R2 clone
    1960 conv
    SDC member since 1972

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  • JDP
    replied
    I once owned a R1 Avanti 4 speed with 4:11's and 0-60 was faster then a R2 with 3.31's. With 3.08's, you'll pull stronger in 4th above 100 MPH.

    JDP/Maryland

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  • Dick Steinkamp
    replied
    quote:Originally posted by JDP

    The 3.08 gears are a boost killer since the engine,is spinning up slower in the gears. Put it in 4th, pull 5000 rpm and 130 MPH and you should see 5-6 pounds.
    Why would the engine spin slower with one rear end ratio or another? The car would go faster at 4,000 RPM (in any chosen but same gear) with a 3.07 than a 3.73, but the engine would be spinning up the same.

    I thought supercharger boost was related to engine RPM only. The faster the supercharger spins, the more boost it puts out. Why would it put out more boost at 5000 RPM in 4th than it would at 5000 RPM in first?




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  • Allan Songer
    replied
    quote:Originally posted by JDP

    The 3.08 gears are a boost killer since the engine,is spinning up slower in the gears. Put it in 4th, pull 5000 rpm and 130 MPH and you should see 5-6 pounds.

    JDP/Maryland
    3:08 gears in a 4-speed R2? That's just plain UNNATURAL!! You need to get you some 3:73 gears!!!!

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  • JDP
    replied
    The 3.08 gears are a boost killer since the engine,is spinning up slower in the gears. Put it in 4th, pull 5000 rpm and 130 MPH and you should see 5-6 pounds.

    JDP/Maryland

    Leave a comment:


  • 59r2
    started a topic when does the boost come on

    when does the boost come on

    I took the 59ht for a ride with the new r-2 engine. Started nice and easy got it up to temp,and decided to see what she had. with 3.08 gears it is not much out of the hole, brought it up to 3500 shifted (@3500 I still had 5 inches of vacum)pushed harder in secound to 4000 had about 0 inches of vac nailed third kicked the secoundries brought it up to 4200 noticed about 2 lbs ,hit fourth and ran out of safe road. Called john erb before I did this (he said I should have about 1 lb at about 2000,3-4 at 3000-3500 and about 6-8 lbs at 4000-4200). I am running a 5 1/8" supercharger pulley and the belt isn't slipping. tried running a search for porfance of a r-2 and can't find any rules of thumb.would apreciated any insight on this subject.
    Thanks,
    JOE

    1959 HARDTOP R2 clone
    1960 conv
    SDC member since 1972
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