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  1. #1
    Vern's Avatar
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    Riva Stage 2 thoughts

    I was reading the new post about how Bo Dupriest is running 77 mph with basically a Riva stage 2 setup, but BDNJ does also. I know some of us have wondered how that is possible and if the 'magic' is in their intercooler, or the prop, etc, and yet trying those individual parts did not answer the question or add 'the magic' by themselves. I was looking at the Riva dyno charts and did some thinking, wanted to throw it out here for consideration.
    Peak Peak 8100rpm 8100rpm
    Stock, 7.28 psi, 209 hp, 137 tq 209 hp 136 tq
    Air Filter, 7.98 psi, 212 hp, 139 tq 210 hp 137 tq
    S/C Impeller, 8.42 psi, 215 hp, 141 tq 215 hp 140 tq
    Intercooler, 8.75 psi, 230 hp, 151 tq 229 hp 149 tq

    Concentrate on the far right columns, at 8100 rpms:
    Looking at 8100 rpm, the air filter picked up .70psi, but only 1 hp.
    The S/C impeller only picked up .44 psi, but gained 5 hp.
    The Intercooler only picked up .33 psi, but gained 14 hp.

    The 'magic' is in the entire package as Jerry and others have mentioned. As Nitro and others have tried to explain, boost does not mean much ... its all about air density. As a blower starts to operate outside of its efficiency 'envelope', boost can go up, but hp go down. This is due to the blower starting to 'overheat' the air, which will register as additional boost, but will make less hp since it is too hot, and therefore less dense. This is why it IS important what CFM the blower will produce. Knowing only boost without knowing CFM (or exit air temp or air temp rise from the blower) will not tell us much.

    I think anyone who has only installed the Riva intercooler and the 15/20 (but not the S/C impeller) will be disappointed and not have the craft perform to Riva's advertised speeds. I think the Riva/Vortech S/C impeller favorably changes the CFM and 'efficiency map' of the supercharger, and THAT is more of a help than the slight increase in measured boost. I think the impeller is a bigger help than we thought, and that is another reason why I am very interested in all the possible blower improvements in the works.

    Anyway, just my .02 for today. Boost and air density and hp, like most things in life, are like an onion ... there are many layers of knowledge to all these subjects. The answers are rarely as simple or one-dimensional as we would like.

    Shucks, can't get the columns to stay lined up ... oh well, hopefully you still get the idea!


  2. #2
    Nonstop, all day, everyday. 01xdime's Avatar
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    It'd be nice to run a test with a temp sensor before the SC, before the IC, and before the throttle body.

  3. #3
    Vern's Avatar
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    Exactly! That would answer a lot of questions. Speaking of density, cooler air is more dense and that is why the Riva Intercooler, altho only registering .33 psi of additional boost picks up 14 - 15 hp. It does what an intercooler should, cooling the air, making it far more dense, making more hp.

  4. #4
    Nonstop, all day, everyday. 01xdime's Avatar
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    Thats why i've been saying all along. You can have an IC run more boost but if it's hotter air it might not mean shit. Then you might have an IC that makes for less boost but cooler temps which mean denser air and more HP. And thats all that matters.

  5. #5
    Water4fire's Avatar
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    I sure wish we had numbers on the RR IC. I bet they are dam close to each other.


    .

  6. #6

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    The only thing Bo is running from Riva is the IC. It was good for almost 3 mph no problem. His stuff is that fast because of his total package. he has spent the last 2 weeks working and testing on his RXP Morning till night. Back and forth to the lake, atleast 3 times a day. He changes everything, even the aftermarket stuff he recives, he tests it, then goes back and will work on it or change it till it is better. Once again, all he has is a Riva IC Solas prop, Aircleaner ran up front, and something elese, and Im sure you guys will know soon, its leaking all over this fourm now. He has done some other stuff to help handleing and some stuff to the pump area, to make the stock pump work a little better, I think, but I have not really payed attention.

  7. #7
    Vern: here is one scenerio that will not yeild same resulys as Riva indicated:
    Being that the RXP SC turns faster than the GTX SC= gearing.
    I did not change the gear ratio, kept the stock set-up, 17 tooth SC gear.
    Now: SC has RR shaft and Vortech installed.
    going to install Riva thru hull
    going to install Riva IC
    going to install Riva air intake
    going to install RXP ECU soon...

    and this will be with a modded pump using the 16\21 3 blade...

    What do you guys think I will gain???
    I don`t think it will be nearly the same gain as Riva advertises for the RXP...PR...

  8. #8
    way2fast's Avatar
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    "what do you guys think I will gain?"

    A big bill for parts and if you are lucky, a little speed !

    (sorry, I couldn't resist )


    Richard

  9. #9
    oh Richard you comedian you!...LOL...PR...

  10. #10
    Nonstop, all day, everyday. 01xdime's Avatar
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    Shit you think thats bad look at me! Forged pistons, oil system work, RXP SC gears, IC, RR ECU,rxp fpr, thru hull exhaust, intake, sponsons, RXT pump w/triple bearing mod and stainless wear ring, prop, seat cover, boost and A/F gauges, and possibly one of Les's kits with a bored throttle body. I hope i gain something. especially reliability.

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