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Sun Nov 12, 2006 4:05 pm

Has anyone ever built a rotary baja? A succesful one? :) As in driving around today or in the past? Used mainly half on-road, half-off?

Searching this forum for "rotary baja" only turned up a few hits and it was mainly discussions on the pros and cons. Mostly cons. The rest were for rotary fuel pumps.

Rotary bajas are generally frowned on due to their higher rev range and less low end torque making them less desirable for off road use. This is because the most reliable means of extracting more power is through porting, which moves the torque peak higher in RPM. For this reason, most tend to shy away from rotary bajas.

Feel free to add to this post, contradict me etc. :) The more info available, the more future swappers can use to make their engine choice decisions.

Sun Nov 12, 2006 4:12 pm

Rotaries tend to do great in street driven bugs regardless of how they're set up, but for off road, not so great. Knowing the potential pitfalls of going rotary, and having been into them for a number of years, I know how to keep them happy and repair whatever goes wrong. I can also build one with excellent low RPM attributes and keep it simple. I feel it's a pretty safe bet for me to rotary my baja.

Why do I want to go rotary? The current 1600 is tired. If these engines have a healthy 55HP when new, I'm sure mine is somewhat lower now. It had some recent headwork and possibly cylinder work before I got it. There is lots of blowby; you can see it as slight steam coming out of the breather by the oil filler cap. The passenger side of the engine gets covered in oil after a hard run (in other words, just keeping up with highway traffic, lol). The level itself doesn't go down much so it's not a lot of oil, but you can tell a fair amount of compression is lost if it causes that much oil to come out.

It still runs ok, but it's tired. I'm sure a carb upgrade would help some as the stock one has a flat spot in the accelerator pump. Of course the accel pump doesn't affect partial throttle cruise, where the engine also lacks power. A Weber progressive or other aftermarket carb would make the car harder to start and less friendly to low revs. Right now it can idle at 500 RPM and if accelerated slowly enough, it builds power until about 4000 RPM. Not bad, but I'm ready for something better. Besides, it can't climb a slight grade near my house in 2nd gear which my rotaries can handle with similar gearing in heavier vehicles. Infact, it has some trouble in 1st.

I want to go carbed 13B with stock ports and a stock carb. Simple, reliable, driveable, cheap, and should provide twice the HP and torque of the current 1600 without twice the weight. Maybe 40 extra pounds? That's what everyone is saying. Mine should weigh the same as a 12A because I'll use a 2nd gen waterpump to shave 6 pounds, which is about as much as the 13B specific parts will add. It should break even with ZenJoe Green's bug in the weight department. :) Mine will just have more torque while his has more high end HP.

Who knows. I may be the first to successfully baja a rotary. Oh, and it should be able to idle at 500, too. :)

Sun Nov 12, 2006 4:21 pm

yep this is my rotary powered naja bug that has been on the road and my daily driver for the past 8 months and has never let me down it also sees the beach and in the next few weeks with some mud tires some more dirty work

it is a 13b injected series 4 injection with a series 5 block and large extended port job, i run a microtech lt8xs with the dash unit and everything esle is custom built take a look at my website it should provide you with all teh info mation on how to do the swap

http://groups.msn.com/GottaVW

enjoy :)

Sun Nov 12, 2006 6:33 pm

You might also search here for rotary bajas/bugs:
>Conversion Perversions<
http://www.shoptalkforums.com/viewforum.php?f=19

Sun Nov 12, 2006 8:24 pm

thudknuckle's baja is one example. It's been successful on the street. I can't wait to find out how your baja will do in the dirt. You say it's ported but I've seen the primary ports in S4 engines, and the port timing is rather limited. That is to say the side plate itself limits the size of the primary ports (not enough material in the casting to port very large). You'd be lucky to port an S4/S5 out to stock 12A spec. :) Then again you also have the dynamic chamber which improves power and a progressive throttle body which begins to open the secondary ports at about 10% primary throttle opening. You also have 460cc or 550cc injectors, depending on S4/S5, and tuneable timing advance. Since it is a 6 port, you've got the aux ports which kick in at high RPM and act like a huge streetport, but without the drawbacks at low RPM. I'd like to have a 6 port but glad I don't have to deal with the wiring and ECU stuff. My carb has already proven itself an excellent low RPM runner on stock and streetported 4 port 13Bs. Surprising well, actually. That's why I chose it specifically for this project. I don't want to deal with the added complexity of an EFI setup in a such an otherwise simple car. I've already got my hands full with a MegaSquirted 20B. I considered the 20B in my baja, but ultimately decided against it. Well, maybe I could do it some day... :) Of course that would mean the recipient of the 20B would have to get a 4 rotor instead. That would leave the 20B available for the baja. :lol:

subybaja, yeah I searched a couple weeks ago and found several of my old posts there. Then as soon as Zenjoe started his forum, the level of rotary related posts at Shoptalk diminished significantly. That's probably a good thing too seeing as how all the noobish questions can be asked on zenjoe's forum where they'll get better answers.

Sun Nov 12, 2006 9:40 pm

It's got a bugeye kit. How should I mount the radiator?

I don't want to switch to a single piece front end. I considered some wide eye fenders but I don't know yet.

I have a really great radiator in mind from a 1st gen RX-7. It's tall and almost square. Plenty of cooling surface area. If I totally ditched the bugeye nose and installed the radiator in its place, and moved the headlights to where the turn signals are, similar to SHMO's setup, I bet it would work. Kinda ugly though. Hmm...

Mon Nov 13, 2006 1:09 am

the rotary in my baja actually has a series 5 4 port turbo block including all three plates and rotor housings :) the plates wehere ported by Mr rotary to ensure that the recieved teh biggest possible port job without goin bridge and i opted to go this way rather then a 6 port N/A block becouse in the future ( few months) i am hoping to fit a supercharger maybe a whipple :) i have had my baja out in the dirt a few times now and it performs extremly well, alot better then the hot 1600 tp that was in it before i went water cooled and ove rthe xmas break i will be doin a 5 day beach trip in it so ill keep you posted on how it goes in the sand :)

take car all chill

Tue Nov 14, 2006 4:31 pm

Was your exhaust ported? Or just the intakes? A whipple is a very nice supercharger. I helped a local rotary shop owner get one running on his 20B in a T2. I never drove it, but he said it was scary fast. http://www.nopistons.com/forums/index.php?showtopic=43926

How is the low end of your engine? I mean the really low end like 1500 RPM and lower? Where does your engine idle? Can you start out below 1000?

I realize EFI has several advantages over carbs, and your idle can still be decent even with large ports (especially because even T2 primary ports can be ported only out to 12A spec). I can port my primaries quite a bit larger, but that would destroy the low end power.

Right now I'm communicating with a rotary guy that knows a fair amount about air flow through carbs, manifolds and ports. It's my goal to choose the best parts to give the engine the best low to high RPM power while comprosmising as little as possible. Preference mainly on low end. I know the answer is out there. I just have to learn a little more. Then I can build the engine.

Tue Nov 14, 2006 7:25 pm

hey there yeah my exhaust ports are ported a little and being a turbo housing they dont have the air diffuser in them iether which can also limit flow.

As for idle it is more then happy to idle at 800 -850 for ever on end and i find that the low down toque is plenty being in a light car. 1st through to fourth general driving sees the gear changes at around 2100-2500 and i normally cruise around in fourth at 60 kmph with out any troubles at all including up hills although on a very steep incline 3rd is required :) i am running a standard ratio 091 box :)

im only just started to look into superchargers in depth and i have heard some good things about whipple and atkins :) i am goin to go supercharger over turbo for a few reasons 1st is the low end toque advantage over a turbo 2nd is the unque sound of a supercharger whine and 3rd how many people do you know with a supercharged rotary in a baja bug LOL ahh heheheh i like to be differant :)

i know that many people will still suggest turbo though, becouse it is much more efficant but im really liking the sound of a supercharger ( even though it is not at all needed cos the car already goes like a STUNG CAT heheheh

Tue Nov 14, 2006 8:31 pm

I recently installed an Atkins 5" in my brother's RX-4 wagon. It only had 600 miles on a fresh rebuild so he is taking it easy for now.

The low end below 1500 isn't impressive, just to let you know. It's basically like stock. Above that is surprising. He only took it up to 5500 so far and it starts to get scary as the suspension is stock. So are the brakes. :)

I suspect he'll really open it up after it's reached 1500 miles and has gotten a little better at judging the new powerband.

Would I do a supercharger in a baja? Well, keeping with the less complicated the better, perhaps. It would weigh less than a 20B and wouldn't require EFI. The super low end would have to be all there first though. That's what I'm trying to sort out right now.

Hey, any ideas for where or how I should mount my radiator with a bugeye nose?

Does the 091 have shorter ratios than a stock bug? I'm going to see if I can trade my 1600 and bug tranny for a good bus box. Preferebly 5 rib. I'm not sure how I'll connect the shifter. Those adaptors are kinda funky.

Tue Nov 14, 2006 11:00 pm

hehe sounds like fun :) suprising to hear that it doesnt have alot below 1500 ?? is that abotu where it starts to pick up ?? cos even then that is bearable :)

i find the ratios of the 091 ( 6rib) to be great all round but if you would like to go a a lil lower a 5 rib might be the way to go or even lower again a 1600 kombi box ( least you would be quick of the line and through the gears lol

i highly recommend front mounting the radiator after all that is where they are ment to be as my car has never had an over heating problem- i have seen others mount them in the back cage - above the gearbox - above the engine and in the shape of a big rear wing all of which may be a possibility )

if you where to front mount it in a big eye kit maybe you could get some wide eye fenders and use them for the healights and customize the bug eyes into grills or slot them out to make one long wide grill with the radiator behaind it . you will also need a radiator shroud to help direct the air through the radiator cos if air is able to go arond the raditor it will instead of through it ( less resistanc)

Wed Nov 15, 2006 11:11 pm

Yeah, I was told by Atkins themselves that their SC doesn't start boosting until 1500. Then I experienced it first hand on my bro's engine. It's not bad, and you can vary the load on the engine with the clutch pedal and throttle to work with it/work around it. I got the hang of it after a few minutes of stop and go driving around the block.

I don't think I need a Kombi box. My friend's streetported 13B baja did ok with a 5 rib. I'll have to see if my local VW guy is willing to trade one for my running 1600 and bug tranny.

My friend's baja ran hot with the radiator up under the rear wing. I am considering mounting it in the back with the fan behind. That would be the most simple to set up. Would it run cool though? It may not work well with the exhaust I was planning.

If I mounted the radiator up front I could relocate the headlights to the sides, under the fenders or on the front bumper with these. http://www.mooreparts.com/AC941411.html

The problem with the bug eye front is the lack of room inside. It's a good thing for what it is; a really small front end, but bad for a radiator. There are only a few bajas around here, and none have a bugeye front, so at least I've got the 'different' look going.

If I could come up with a good way to route the exhaust so its heat wouldn't get to the radiator, I'd would mount the radiator in the back.

Thu Nov 16, 2006 2:57 am

my orginal plan for my exhaust may very well work for you :) i was planing to have the extractors run back over the top of the axle turn right over the gearbox where it would join into one pipe and then drop back down the otehr side of the gearbox and out the back into a straight through muffler:)

The reason i didnt do this was to keep the heat away from the top of the floor pan and inside the car ( i also wrapped my exhuast to help stop this) and i dont have much room above my gear box due to my fuel pump being located under there..

the problem with havign the radiator in the back is air flow you may need to make some sort of scoop to help direct the air from the back of the car and down through the radiator to prevent it from fust goin ove rthe raditor and not through it ?

in order to fit a radiator in the front of my kit i also had very limited room but this was solved by cutting the front of the baja ( wheel well area) right up to the fual tank ( i then braced it with tubing) the front nose cone of you baja looks about the same size as mine as it looks liek it meets the beam in the same place :) some thing to look into

i have seen ppl with the raditor mounted directly behind the motor ( subi conversion) and he found that it ran a lil hot, but say with teh aid of wings directing the airflow helped :)

hmm cant wait for a SP should be sooo much fun in a baja :)

Sun Nov 19, 2006 6:49 pm

well i took the baja out on a bush buggy bash today with the aussie manx offroad club and honestley the rotary had more then enough balls to get the job done the problem is purly traction. with road tires on that i was able to get up the the hills and aroudn the course but would have been alot easier with mudders. the rotary povided ooddles of power and i am re thinking the idea of a supercharger as it easily wanted to continually spin the wheels in second up one of the steep hills ( starting of at idle speed at base of hill). had a great day with no breakages other then a small split ( 1 cm) in a rear gaurd, car slide down into a tree.

Mon Nov 20, 2006 10:59 am

That's just the kind of info I was hoping for. Thanks for the performance report.

I decided to rethink my 20B idea too. A 13B will be plenty. More than enough. I'll only reconsider the 20B idea if and when I do a 4 rotor in an RX-7 some day. Yeah, some day. :roll:

I took the baja for a short drive after correcting the bowden tube and front tranny mount. The PO didn't set them up right which resulted in seriously pronounced clutch chatter and a slightly sagging engine. Now the chatter is a rare occurance and much less severe (I think my bowden tube still needs more of a bow/longer length as I've run out of space to add washers). I can actually drive it now. It just needs electrical (blinkers etc) to make it road legal.

It barely made it up a nearby paved hill in 2nd at a slow speed. The engine seems to have the most power between 2000 and 3000. I assume this is due mainly to the dual port heads. Above that its acceleration starts to drop off as it hits 4k (I think 4500 is the engine's max). Below 2k it wants to bog.

I can't wait to put a rotary in it. I just got my REPU running again after sitting for a month due to carb trouble (and lots of rain making working on it outside unpleasant). After swapping the carb and spacer, it now will idle pretty smoothly at 500RPM, but I have it set up closer to 850 or so. It still needs some fine tuning for cooler weather.

Its low RPM performance surprised me when I attempted to idle it up a hill. Idling around 900, I let the clutch out slowly without any throttle and it crept up the hill, slowly pulling the RPM down to about 400. :) Satisfied, and with the truck shaking lol, I slowly laid into the throttle and felt for any bogs or other signs of struggle. There were none. I drove it the rest of the way up the hill between idle and about 1300. It handled it fine. All this from a streetported 13B. Man, I can't wait to see how an unported 13B handles itself down low.

I also am very intrigued as to whether the bug tranny in my baja will be compatible with a rotary. It has tall gearing but the 1600 is so gutless it seems that switching from 3rd to 4th on the freeway doesn't increase speed or help at all. So much for the freeway flier, or whatever gearing it has. :roll:

1st and 2nd aren't that bad though. Somebody somewhere thought this tranny was a good idea in a baja, and it actually was bajaed for 8 or 9 years successfully with no breakdowns. Of course the engine has never had more than maybe 60HP or so. Curiosity is winning out over common sense and I find myself wanting to leave the bug tranny in there even though I know it's not the best setup for it. It will make for a good comparitive test if nothing else.

Mon Nov 20, 2006 3:02 pm

i think a 20b in a baja would be way to much and would take you less places then a 13b , you can have to much power. i find the 091 6 rib is perect for my rotor as it likes to easily putt around in 4th at 60 kmph and pull fairly well up untill 100kmoh where it starts to come alive a bit more and has no problems in taking the baja of the clock with ease. although it will do that in 3rd also :) . have fun with teh conversion would like to know who it all goes :) :twisted:

Tue Nov 21, 2006 3:46 pm

a few pics some of the other members got form the day

can be found at http://www.manxgallery.org/gallery/album343/100_0444

and also under manx club gallery [/img]

Tue Nov 21, 2006 8:42 pm

also a a small vid of the first track can be found at http://www.manxclub.org/TripReport.asp?EventId=41 down the bottom of the page :)

Wed Nov 22, 2006 3:31 am

any feed back would be awsome :) cheers guys

Wed Nov 22, 2006 10:26 am

I checked it out. Your baja sounds different from the rest. :twisted:

It looks like it does well in the dirt. Certainly has more power than mine.

Question. Do you have to keep the revs up to tackle hills like that with your port job? Or is it possible to idle up them with your Kombi box?