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Friday, September 03, 2010

Author:	Topic: Rexx's Mazda Rx-7 Powered GSX Seadoo
Rexx	posted: 8/6/2002 8:14:48 PM Nope.. Between a bachelor party that punished the liver and more hull truing..not much got done. Should be in the water this week though and I'm looking forward to it! I'm starting to go through withdrawls. Usually the first sign of withdrawls is twitching of the throttle thumb.
rx7351w	posted: 8/6/2002 7:18:27 PM Rexx Did you get any water time in this weekend?
Rexx	posted: 8/4/2002 2:19:42 PM Shawn, Yes, the RX hull will work too. There may be some gains to play with the mounting position for the specific shaft to be used. But, I can make a pump spacer out of ABS plastic to get the proper location with respect to pump shaft. The pump spacer is actually a good thing as it sets you up for a more even flow field distribution on the impeller intake side. At any rate, the mounting scheme will be application specific where as the drive assembly will be universal. Indications are that any 785 based ski or 951 (ideal) will work for mid two seaters and three seaters. As for the 20B in an RX fit wise, that might be a tight fit. You could move the gas tank a bit forward and this may allow you to squeeze it in. But, the problem would lie in getting the motor rotated properly when you insert it in the hull since the 20B is longer than the 13B by about 5 inches. Hmmm..you wanting that stock 300 hp huh? A peripheral port 13B will give you 300+ hp naturally aspirated. Would you really want anymore than that for the RX hull (peripheral port 20B would be 450+ hp naturally aspirated). The 20B would be a good match for the heavier SeaDoo three seaters and big Yamaha GPR and XLT barges. I'll probably make my own ignition/wiring harnesses for those not interested in making their own.
SeaS	posted: 8/3/2002 9:35:13 PM Rexx would a 20b fit into the rx hull??? Just wondering? That could be your next project. Also if the mounts you have made work in the gsx hull would the identical mounts work also work in the rx hull? I would asume the mounts would work and the drive shaft would have to be altered. Also if someone were to purchase a rebuilt rotary engine from scratch where could the ignition and wiring harnesses come from? Please post and keep posting as often as possible!!! Thanks Shawn
Rexx	posted: 8/3/2002 4:33:31 PM Either automatic or manual will do. YOu won't be needing the flywheel, but you will need the counterbalancer from an automatic. If you were to remove the flywheel/clutch pack from a manual or remove the torque converter/flex plate/counterbalancer from an auto, you would be left with the same block and crank. Some guys will confuse you and tell you that the cranks are different (bullsh*t!). Go on ebay, and look for apex seals. They will have a direct link to atkins. You can use the stock motor, but it would be good for you to rebuild your own so you know what you are starting out with. These motors are real simple. In my case, I wish I had rebuilt mine as who knows what the engine condition is with 69k chicago city miles. If you do tear yours down, I'd suggest a peripheral port. I will be setup to incorporate peripheral ports on stock housings soon. YOu may want to check the bottom of your hull to now that the engine is out. While a few mph gain don't mean too much in light of the big rotary transplant, you may want to check rideplate alignment and what not. I looked at my friends stock GSX it it had about 3/8 inch dip before the ride plate on one side an 1/4 inch on the other side. If anything, the ride plate should be level to partially recessed.
Ziggy	posted: 8/3/2002 1:05:50 PM I've located an '87 W/ 100k "running when removed" in a preliminary search. I'd like to find something newer and with less wear. Does the original transmission configuration matter in this application? I keep getting asked whether I have a manual or automatic. All I can tell them is "well..." I've been to Atkins Rotary and many other rotary sites so I know what you're saying about seals. If you'd like to email direct I'm at DavidMSigler@AOL.com
Rexx	posted: 8/3/2002 12:16:41 PM Lucky you! I love that '99 GSXL, probably the best color scheme of all skis! Yeah, the 951 based skis (with thrown rods) make the best setup conversion. They have the bigger pump channel and the bigger 951 pump. With a decent running 13B motor, you'll need every bit of that 155mm pump. Keep in mind, requiring the 155mm pump is a completely different way of thinking than tuning previous two strokes. Big Yamaha superstocks are turning the 155mm skat pump with no problems. Because of the lower torque of a built two stroke over a stock wankel motor configuration, a properly running 13B rotary motor (1300cc two stroke cc's with tremendous bottom end grunt) is required to be mated to the bigger pumps. The 951 motor cannot torque the 155mm pump and that is why the D pump at 148mm is a better match for the 951 motor. Some people will change their tone about the Mazdoo when I start tuning it and posting results. Hope to have it back together this weekend. Anyhoo... I'm sure I sound like a broken record repeating the differences in torque of a two stroke versus a four stroke. Actually, my main motivation with the rotary was to have a platform to supercharge or turbocharge. I had no idear that these things can make over 300 hp in naturally aspirated form on 87 octane gas. This news came to be about March or April (I was already cutting chips at that point). The kit availability will be a bit, so, get the motor out,clean out the hull, find a set of (2) 48+mm carbs. NOvis would be a good bet. The BRMs require a different fuel rail which rigidly holds the carbs together. I can make this fuel rail pretty easy. Just mount the carbs to the motor, then identify the bolt coordinates for a CAD/CAM model. Don't tear into the electrical system quite yet. I'm wanting to develop an interface to the existing electrical system. This shouldn't be too hard to figure out. Things you will also need are a decent marine grade fuel pump (I have a 110 GPH, but that is bigger than what I need), fuel pressure regulator (3-40 psig regulation), fuel pressure gage, MSD ignition (two channel would be better to direct fire the leading and trailing simultaneously, but two rotor banks independently...otherwise the trailing plugs will detonate if you batch fire all four plugs at once). Start looking for a healthy 13B motor. The 3rd gens ('93-'96) are the strongest motors. But, they come with low compression rotors. Unless you plan on turbocharging or supercharging, I'd try to locate an '89-'91 N/A motor. But '86 and newer 13Bs will be just fine too. If you go the route of a 12A, this will have a different mount pattern, which I can accomodate for in my CNC programming...just haven't made that program yet. With the motor out, you may want to consider an entire rebuild. Before you start the rebuild, ask yourself what kind of power you expect and at what RPM you want to run. The first upgrade I would do immediately is get the 2 piece, 2mm apex seals. These things are considerably better than the OEM 3 piece,2mm apex seals. Go to www.atkinsrotary.com , actually, they sell these apex seal kits all the time on EBAY. I can post details about rebuilding the motor and even setting up a peripheral port motor when you get to that point.
Ziggy	posted: 8/3/2002 10:08:53 AM OK Tom, I'm ready to talk about this MazDoo project. I picked up a '99 GSX-L last night with a thrown rod. Everything else appears to be in good condition - need to tear into it in a couple of days. This boat should make a good platform for the project, what do ya think?
Rexx	posted: 7/31/2002 10:18:19 PM ttt (just for you Robert, I know you're peaking...lol..)
PWC Beast	posted: 7/31/2002 7:02:13 PM Yawn :-)
Rexx	posted: 7/31/2002 6:03:59 PM Someone finally gave me some target numbers!!! 155mm pump: 16.5/23.5 impeller @ 8000 RPMs gave them 77 mph on a heavy ski, way bigger nozzle than me... Finally getting some target information... very cool.... Need to find 800 more RPMs and my horsepower brake will be spinning with respect to the Rotaries capabilities having 69k miles and no port work. he he.....things are making sense. Exhcellent!!
Rexx	posted: 7/31/2002 1:57:12 PM Wayniac, I say, just build a big enough floatation with seat padding to float the motor and jetpump and ride! That's all a stand up is!...lol.. I just like the idea of making 300+ hp naturally aspirated and consuming 87 octane gas!!! You won't find a motor like that to fit skis. In fact, these rotary motors will run off of 80 octane quite nicely (racers bring 80 octane to the racing tracks to up their horsepower!!). 93 octane in naturally aspirated form is a big waste of money. Although, 93 octane would be required for high boost setups (supercharged/turbocharged).
The Wayniac	posted: 7/31/2002 1:04:12 PM right on. yeah, the smaller ones would come along later i guess. i always harp on the older ones though, cuz i started riding in '89. three seaters are boats. 4-tec...forget it. of course the is just in ref to myself. families get great function from those rides. they just don't equate to fun for me.
Rexx	posted: 7/31/2002 1:01:12 PM Yeah...or hull mods. I could see leading and trailing sponsons much like you see on stand ups for the HX and smaller skis. That won't be a priority at this stage though. While my initial release is not focused on the three seater platform like every other PWC manufacturer has done for fourstokes, the biggest market would probably be the GSX type hull. The RX is 60-70 lbs heavier than the GSX 800...people have come accustomed to weight increases. Whats more....I bet many people would buy a 4-tec powered GSX or RX if it weighed 600 lbs. The rotary 13B (2.6 liter) being 1.1 liters bigger (four stroke liters) than the 4-tec (1.5 liter)...certainly there will be interest. If the rotary was all aluminum (which can be done), it would be lighter than the 4-tec motor (I'll bet money on this as this is a shoot from the hip guestimate).
The Wayniac	posted: 7/31/2002 12:53:24 PM never put too much time on either of those types of machines. i spend most days either bombing to the river (HX), or chasing big boats (X4/XP). good point on the flipping, but i guess i'm heading to......>will this kit be just for the GSX/GTX? it seems there might be other possibilities, but maybe not the ones i like best. probably just as well, cuz i have serious doubts about the majority of hulls staying controllable at the speeds you seem to estimate are within the realm of possibility. how do we all tackle that???? new hull designs?
Rexx	posted: 7/31/2002 12:42:05 PM Wayniac, Valid concerns. Hence the reason or need for a demo unit to diffuse these concerns for prospective consumers (until the word gets out that all is "as advertised"). By the way, when was the last time you rolled a GSX or GTX? I think people confuse XP (X-4 hull) useage with other skis that aren't exposed to the same nonsense. The oil system is easily solved with a dry sump setup using an active scavenge pump. For most users, they hardly notice the weight changes associated with high versus low gas tank levels, so, I'm guessing they won't notice the weight impact of the rotary since it is closer to all neutral axis of the ski with significant torque increase and thrust to weight ratio increase. Increasing weight does help with rough water hook up. Ever notice that riding two up stays better planted in mild chop? Certainly too much weight costs performance. Heck, an old SPi feels heavy due to lack of horsepower. This rotary conversion won't lack horsepower! Bottom line, I don't expect anything big till performance, reliability and satisfaction from word of mouth.
The Wayniac	posted: 7/31/2002 11:46:41 AM Rexx. The jetboats is where I think some of the best usage/apps would come from. I feel (for one reason or another), that alot of people who want big HP are like me... 1) sick of modding 2 strokes to run them to the breaking/blow-up point, but 2) like to ride hard and are concerned about increasing the weight of their ski and 3) would inevitably be concerned with 13b durability/reliability in the event of "turn-overs" and sinkings. Alot of jetboaters would give two craps about anything i mentioned, as P to W would be sufficient to make the conversion unnoticable (from the handling and usage standpoint). I'm a bit apprehensive about the 13B WRT a fun, agile ski. no burn, just throwing in my perspective and specu.... pete....some one would want the coffee can deal, no doubt. i'm waiting for a "Graphics Unlimited" or big "H" Honda logo to show up on a ski at the lake.....it'll happen (running to grab a barf bag), lol.
Rexx	posted: 7/31/2002 7:51:15 AM But Pete, If this thing had a crustang V-8, you'd be all about it!...lol...I was looking into a small Hemi, but the darn thing weighs 350lbs! As for the carbon fiber...already exists. The Coffee can exhausts? I'd shoot anyone that considered such an idea. But a nice 304 SST billet exhaust with 6 flush head bolt pattern looks nice which is what my current setup has. I'd rather see PWCs go down the route of cigarette boats using Gaffrig gages, anodized hardware...etc. Joe, This could turn huge. Think of all the hulls out there for this update kit (blown up 951 skis, anemic 785 GTXs, Kawis, Yamis, Polarises, two strokes are still in production). Right now, it is a working concept and is receiving its improvements as I continue to learn the setup. While I can figure things out now for my one-off ski, the difficult bridge to cross is when I release preproduction to a small beta test group. This will unravel little annoyance problems that I never encountered..hopefully not, but preproduction is designed to work the fine kinks. The real excitement will be when I get big speeds, endurance run time hours and demo acceleration. Regardless of dyno plots of the rotary motors all over the internet, there will always be this small population in which torque curves don't register into reality. For those, a public demonstration both in terms of a riding demo and race lineups are what will attract attention. The development is fun. I also like the idea of jetboat prospects. Imagine all the single engine 785 jetboats that would benefit from this conversion..... The website will be started soon (one of my Engineer friend's 13 year old son wants to do it...talk about cheap qualified labor eh??..kids these days are amazing!!). As long as Glen allows (and to date, he generously has), I will continue discussion on his board.
Rexx	posted: 7/31/2002 7:19:10 AM Chris, I wish I had the end and mid hsgs designed and qualified for aluminum material to replace the cast iron. This would knock the weight down to 150 and you wouldn't notice the difference between your current ski and one with a rotary motor. I hope to make production kits over the winter. But this all depends on how much time I log onto my current ski to be sure I don't sell crappy kits. Assuming a clean hull, the install won't take long. One weekend for the motivated and a month for the slow paced folks. The XP would probably be the easiest to do given the engine compartment size and accessibility. 300 hours and time for rebuild? I'd run it longer. that's what's expected of the 951s though?....yikes.
chris_w	posted: 7/31/2002 1:33:42 AM c'mon Tim, dont let me down, my 951 is pushing 300hrs dont make me take it to 400 or should i rebuild the 951 as a fall project or will it be a RoraryXPRR (RR for Rexx Racing)
chris_w	posted: 7/31/2002 1:29:58 AM Rexx- the reason for my question is in regards to the xpl hull. moving farther back will be tough without fabricating a new fuel cell. I think handeling wise the xpl hull would do ok with the weight up front. the ski can bury turns using the entire ski, unlike other seadoo model hulls, but this pushes huge amounts of water and takes plenty of HP the 951, nearly stock, cant keep up with. I imagine that the xpl hull might get a little spooky at 70+ with additional weight up front (kinda like my FX-1 now) the ass end is constantly trying to pass the front end, but i can control the 250lb ski with my 160, I think trying to control a 650lbs ski trying to swap ends may be a little hairy, but lest see :^ )
Rexx	posted: 7/31/2002 1:11:54 AM Chris, The rotary motor is setup to be the same center of mass where the rider sits. It appears to sit further back as the drive assembly is hollow. Indeed, I have a 2.5 inch spacer between the hull and pump with a stock RX driveshaft. While the back part of the motor sits back, it also reaches forward so that the center of mass is more or less a wash. You will feel differences between a 785 powered ski and a 13B mazda powered ski. But it is not significantly different. What I consider significantly different is an X-4 hull versus an Ultra 150 hull. The thought for motor placement was to get more bow lift (so you can comfortably sit when grudge racing rather than hang your butt off of stern to get desired bow lift). Additionally, most side loads through turns are reacted by the hull strakes/chines/sponsons being aft. Would you want weight forward to slip more?...I don't think so. Would you want to plow more?..nope. Certainly, motor position will be optmized in final production configuration. The initial setup is a guestimate of what 'should be'.... I'd really like an adjustable setup for PPG to evaluate and let them tell me where motor position should be. I don't claim to be a riding expert.
snkypete	posted: 7/31/2002 1:10:18 AM The problem is next thing you know the next generation will come about and start putting huge wings and coffee can exhaust systems on the MazDoo. After that??? Probably a bunch of VTEC stickers and sponsons that stick out 4-5" from the hull of the craft (cuz it looks kewl of course!) I see carbon fiber dash inlays, neon and strobe lights abound! Then they'll get jealous of the Honda guys with the turbos....they'll all want to buy sound machines to make the whoooooosh sound of a BOV. I say sink it now before it gets out of hand and is more than just a nightmare! :)
dms500technician	posted: 7/31/2002 1:02:55 AM Rexx, I am not well versed in your project. However, it sounds like you are at the staring point of a very cool thing. As you perfect this it will get lighter. Look where Ford started..... The model A was a pile of crap compared to a car made in 1930. Your mazdoo is not even in production. If this went big I could image where it could be in 5 years with an entire seam of engineers working on it. If you machine can run with reliability, stability, HP. ETC ETC ETC. you will go somewhere with this. From the little I have read you will and there will be a X4 weight beast on the water. Joe........
chris_w	posted: 7/31/2002 12:57:24 AM Rexx, In respect to motor mount location. It appears in the picture (motor in hull) that it sits further back than the stock motor? it is hard to tell in a pic, plus that is not a stock hull. Is / was the motor location for the hull the same as a stock hull? I know you were thinking that the 100lbs in the xpl hull might be too much up front. And this may be the case, but i think it would handle, it might look a little peculier at idle though. Maybe I will pack 100 of lead by the motor and see what it does. about 20 lbs of lead does the FX-1 some good in chop (not to be confused with the FX-140)
The Wayniac	posted: 7/31/2002 12:47:47 AM check. well, a GSX isn't too bad of a hull i guess. sorry for my love of the X4, lol. as for the pitch/yaw/etc, i wasn't sure where the motor sat, WRT the pacement of a typical two stroke motor. i guess that wil depend on your motor mounting scheme...which it sounds like you've put some thought into.
Rexx	posted: 7/31/2002 12:40:34 AM Wayniac, My GSX weighs 500 lbs! But it is carbon fiber too. Two guys can lift it up. Seriously though, with the tremendous increase in low end torque and top end power, you won't notice the increased weight inboard of the ski. The weight is increased about the neutral yaw, pitch, roll axis of the craft. The ski won't feel big like a Yamaha or Kawasaki, but will have the spunk. This discussion highlights the need for a demo model. I'll eventually need to get my hands on a 785 GSX and setup a 13B GSX so people can ride both for comparison. The reality of my market is that people buy GPRs and Ultra 150s without too much worry of 100 to 200 lbs weight impact with marginal hp improvements. Eventually, I will develop aluminum housings to bring the weight of the rotary down from 200 to 150 lbs. With some weight trimming, the ski could be brought down to weight levels indistinguishable of small two stroke powered skis. Keep in mind, racers pack their skis with lead to keep some weight for hook up. I would not recommend this kit for the X-4 hull. The 920 is your best bet for that.
The Wayniac	posted: 7/31/2002 12:22:47 AM BOING. sorry about the 450#/951 comment. i don't and won't own any ski newer than '97 (except SPX's). not to big a fan of all these barges they call 'jetskis'. i like the X4, HX, and stand-ups. '97Xp i had was fun too, but too heavy. so, your answer WRT the 785 was more what i was looking for. that's alot of weight to me (i like jumping). can you envision a 500# 13b powered set-up? in any hull (obviously only the hulls that'd take it...my HX...there's little sense, cuz the hull can't behave above 60mph)
Rexx	posted: 7/31/2002 12:02:24 AM LOL!!! Wayniac...450lb 951 boat? What'd you put the GSXL on Jenny Craig? ....he he.. Seriously though, I estimate a 100 lbs difference for the 785 motor and 70-100 lbs difference for the 951cc motor. The GSXL weighs in at 530 lbs and the GSX weighs in at 500 lbs. So, I'd guess a GSX or GSXL with rotary motor to be at 600 lbs +/- something (??). Bottom end torque and top end power. Yup....rotary motor is a volumetric marvel (1.225 ft-lbs/CID, most four strokes are challenged to meet that number!..let alone whimpy two strokes). We haven't talked about variable intake geometry as factory standard for the '86 motors giving you top end power and low end torque. But really, a peripheral port behaves closer to a super, duper high compression two stroke but build power way up in to 10K RPMs (SCCA racers rev up to 13K). The bottom end torque of a peripheral port is still higher than a two stroke, but you can run 87 octane. With the Mazda Rotary motor, it's like the horsepower Gods have smiled down at us.

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Topic:	Rexx's Mazda Rx-7 Powered GSX Seadoo
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