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  1. #1
    porschemaniac's Avatar
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    Gpr drag racing setup questions

    Looking for opinions on the best intake grate,ride plate,pump,impeller and nozzle combos for 1/8th and 1/4 mile drag raing. Thanks for any information.


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    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by porschemaniac View Post
    Looking for opinions on the best intake grate,ride plate,pump,impeller and nozzle combos for 1/8th and 1/4 mile drag raing. Thanks for any information.
    depends on what powertrain you are using

  3. #3
    porschemaniac's Avatar
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    1490cc,48 novis,165 comp,m16 cages,mad total loss, mild porting on 66e cylinders, mild crancase porting(gasket matched and transfer port opened) mechanical trim tabs,trued hull, 50 to 80 shot of nos. Of course t&w crank in bottom. Tdr waterbox,holeshot mod and rear of hull filled also. Trying to determine if 05 up ho pump is usefull for holeshot and intake grate - ride plate combo. I've got regular skis to play on - this one will simply be for grudge matches on the lake so I don't mind that it will be propped for the nos.

    ---------- Post added at 03:31 PM ---------- Previous post was at 03:28 PM ----------

    Sorry forgoT a bunch of stuff but it's. Triple pipe ski

  4. #4
    mjh3ides's Avatar
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    Before the hydrodrags I tested a HO pump with a 15/23 DF against a 14v Skat SB pump with a 15/23 Skat swirl back to back with a stalker radar. The Skat pump setup was nearly 1/2 sec faster 0-60 than the HO pump. There was no cavitation on either setup. Unfortunately, I was out of time & couldn't add more pitch to the skat prop without breaking it & it was slamming the rev limiter with the stock ignition.

    For a big HP setup like yours you'll probably find more acceleration opening up the leading edge & dropping the trailing. For example, I usually run a 14/25 DF on the OEM pump for top speed but my 15/23 DF accelerates sooooo much harder & for an 1/8th mile drag it didn't matter losing 1mph on top. I'll also be going to triples & if I was willing to spend another g-note on that ski I'd probably go with a 158mm Skat pump to replace the 155.

  5. #5
    philip_gpr's Avatar
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    The Skat pump setup was nearly 1/2 sec faster 0-60 than the HO pump.

    Good feedback, i bet most of this gain was would have been from the impeller so if you wanted to save some $ just get a skat full swirl impeller.

    With a 1/4 mile the Dynafly might come out on top because as already mentioned it will have a higher top speed. Pretty sure in the 1/8 the Skat would win.

    The R&D B transom set-up (rare) would be a great drag racing set-up. Next choice would be the R&D pro shoe and intake grate set. Next would be just a Riva or R&d single bar grate. With any of these set-ups pump tunnel pressure relief must be used.

    Nozzles - GPR 85 or 87

    Rideplate - faster is better (just make sureit is trimmed properly for you water conditions)

    Trim tabs - any, just make sure they are shimmed down, with stockers try something like .120 inch all 8 bolts

  6. #6
    "just sayin".. jetdave56's Avatar
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    Trim tabs - any, just make sure they are shimmed down, with stockers try something like .120 inch all 8 bolts[/QUOTE/]

    with the trim tabs shimmed down ,what are the ''on plane'' advantages?...trying to figure out the machinics of it...is it to keep you planted better in the water? any disadvantages?...can you explain to me Phil or someone who has tested this....might just make this adjustment..

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    Moderator Insanediego Joe's Avatar
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    It keeps the nose down coming out of the hole. also keeps you from bouncing all over the place at wot. You want to have the loosest set up possible with out bouncing. Bouncing kills speed!

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    porschemaniac's Avatar
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    Thanks for all the great info! Keep it coming-please. So popular opinion would be go with a HO pump(second to a scat-i wish!) with a scat swirl over a non HO pump with a concord?? single bar intake grate-no toploader? Anouther question-can a HO pump be macined to accept the 158mm scat impellers?

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    mjh3ides's Avatar
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    Quote Originally Posted by philip_gpr View Post
    The Skat pump setup was nearly 1/2 sec faster 0-60 than the HO pump.

    Good feedback, i bet most of this gain was would have been from the impeller so if you wanted to save some $ just get a skat full swirl impeller.

    With a 1/4 mile the Dynafly might come out on top because as already mentioned it will have a higher top speed. Pretty sure in the 1/8 the Skat would win.

    The R&D B transom set-up (rare) would be a great drag racing set-up. Next choice would be the R&D pro shoe and intake grate set. Next would be just a Riva or R&d single bar grate. With any of these set-ups pump tunnel pressure relief must be used.

    Nozzles - GPR 85 or 87

    Rideplate - faster is better (just make sureit is trimmed properly for you water conditions)

    Trim tabs - any, just make sure they are shimmed down, with stockers try something like .120 inch all 8 bolts
    Yeah, I would've preferred to do the test with identical props but I didn't have a DF available that was machined for the Skat pump, & my swirl prop that was machined for the Skat pump didn't work on the HO pump. I'm not sure the Skat prop alone would pull as hard as the full 14v setup. It comes out of the hole so much better with that pump. Both tests were done with an 85 nozzle & single bar grate. The single bar grate was actually loading the pump too much off the line & I switched back to a 1200 grate just before the race. The ski was probably tuned a little fat on the green fuel setting but with the cool temps I didn't want to take a chance of leaning it too far to get a crisper holeshot with the single bar grate. The single bar grate would've probably worked better with an 87 nozzle but then I would've had to start all over with my prop pitch & didn't have time.

    ---------- Post added at 01:08 AM ---------- Previous post was at 12:53 AM ----------

    Quote Originally Posted by porschemaniac View Post
    Thanks for all the great info! Keep it coming-please. So popular opinion would be go with a HO pump(second to a scat-i wish!) with a scat swirl over a non HO pump with a concord?? single bar intake grate-no toploader? Anouther question-can a HO pump be macined to accept the 158mm scat impellers?
    My opinion is the Skat swirl prop pulls harder off the line but the DF does better from midrange to WOT because of its taller root angle, so use a swirl for 1/8 mile & a DF for 1/4 mile. Like I said above, the Skat pump comes off the line REALLY well, but it's kinda hard to justify the price unless you are using it for CC racing because rough water hookup is where it really shines compared to the stocker. The single bar grate is a top loader, it just has one bar behind the wing instead of 2 like a 1200 grate. It wouldn't require any modification to the HO pump to run a 158 impeller. You'd just need to replace the stock 155 wear ring with a 158. Unless you're trying to cure cavitation, I doubt there would be any gains from doing that though. We do that with the 4 strokes & it takes 2-3 mph off the top speed without inproving acceleration, just helps fix cavitation. On the other hand, I think a complete 158 Skat prop/pump would be the absolute best for someone looking for acceleration over top speed.

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