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Index > @ the Pickup Bed (General Topics) > Thread: 4 X 4 REPU
Thread: 4 X 4 REPU
Jeff20B


Moderator
Posts: 661
posted September 15, 2001 05:19 PM

I've once seen a 4x4 Courier in an auto trader. It had a 4 boinger in it so I'm pretty sure a 4x4 REPU would be fairly easy.

Yep, interesting to think about.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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risc


1st Gear
Posts: 23
posted September 15, 2001 09:48 PM

The manager of Market St. Mazda in Salem, Oregon had one that was a 1 off conversion. I think it would be a cool little 4x4. I'd settle for a limited slip though.

-Dom

       
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted September 23, 2001 07:17 PM

4x4. . .

That would be way cool... have the little repu with a lift kit, and a 4x4... Too bad some of those old magazines haven't found their way onto the web yet.. I bet some of the places that had kits are still around, and the may have one in the back of a warehouse or something... Hum.

Although, 25 years is a long time to keep stuff around... I know that stuff for the 3rd gen has been reduced to sell as of late, as part suppliers don't want to keep parts around for a 10 year old car that sold less than X copies... Imagine how many places still have stuff for a 25 year old Japanese truck that sold Y copies...
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The best way to predict the future is to invent it!
-- Tom Matano


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repuguru


Redlining
Posts: 319
posted October 15, 2001 09:32 PM

I have thought about maybe a body lift and a locker rearend robbed from a late 90's Toyota FourRunner. It is actually an electric locker that only locks when it is activated, by remote switch. Since most four wheel drives today use open differential set ups for both ends they only have 2 drive wheels spinning anyway. And when the two spinning are the ones with least resistance that means your stuck. Unless you have a locker. At least this way there is weight pushing one of the rear wheels at all times.
Oh yeah, the Toyota rearend also has disc brakes and gear options.
Like I said I have thought about this option and realize this would not be a bolt together project, but I think it would be easier than trying to set up a well designed REPU 4X4 that would truly work in real world applications. With probably the same results.

       
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woooody


1st Gear
Posts: 25
posted December 13, 2001 10:01 PM

Curious... I searched the web to find this place, specifically to ask this question. Been debating on what to do with my 74 REPU, and I currently have a couple of Toyota Land Cruisers, and was aondering if an adapter was out there for the rotary.

So, to sum up, some have seen it, but no one knows for sure?

Thanks

woody

       
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repuguru


Redlining
Posts: 319
posted December 15, 2001 03:59 PM

4 b' 4

I think the biggest limitation in building a 4x4 REPU is the fact that Rotaries have no torque. My 77 REPU with its 3.90 rear ratio and stock tire height requires a little extra slipping of the clutch to get it moving. It is well tuned and has great power moving, but, I really think that the 3.9 is almost too much gear for a NA street ported truck to really enjoy. So you head to the 4.6 ratio found in the 74' rearend. Man it makes the REPU a real stump puller with recommended tire size. But how far can you go when you add taller tires before it starts bogging and require extra clutch slippage to get moving. Can you imagine sitting in a creek bottom trying to climb out with big tires and no torque.
I really think that if you want to overcome the problem OEM REPU gear ratios are not a choice. You have to go way down. Maybe a 6.3 or something along those lines.
The LandCrusier stuff might be a bit heavy duty. I had an FJ40 for some time and looked at the possibility of putting a REPU on top of an FJ40 frame, but the wheelbase is not right. The FJ45 truck frame might be closer, but since they are impossible to find anymore that would move me to other options. Also they are geared for a low rev 6 cylinder torque monster not a high strung Wankle.
I would set up a gear ratio/transfer case combo that would yield a crawl ratio as close to 100:1 as possible while in low range that way the torque issue becomes irrelivent. Heck you could almost have the REPU moving on pedal power with that kind of reduction.
I still haven't even addressed the steering linkage problem with dropping a wankle in most truck chassis, but I think that with enough over engineering even that could be overcome.
A 2" body lift with maybe 29's or 30 inch tires with the electric locker rearend out of the Toyota 4-runner is what I will do to have an off-road ready REPU. It may not be a Moab rock crawler, but for most off-roading adventures I have it would be just what the doctor ordered.

       
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Jeff20B


Moderator
Posts: 661
posted December 16, 2001 03:46 AM
Edited By: Jeff20B on 16 Dec 2001 03:51

No torque at idle you mean? I agree, but anything over 1500RPM has enough torque for anything. I like the fact that a rotary still has lots of torque when a piston engine starts to drop off (at 4kRPM+) and continues up to around 7k before dropping off. We've got to figure out proper gearing to take advantage of the different style of torque. We've got less tip-in, but more overall usefull torque, and that's a fact (according to a Corvette website that praised a long flat torque curve. I don't have the URL at the moment).

Maybe 6.3 would be ok with a torqueless street ported engine, but I don't really agree with using a street port in a 4x4 because the ports sacrifice low end torque for high end power which is basicaly opposite of what any decent 4x4 would normaly use. But don't take my word for it. Try it yourself and see if you like it.

I personaly would still use a rotary over a boinger in a 4x4 if it is tuned for maximum torque. It will still have the high reving smooth delivery of power (torque) that the rotary is famous for, and less weight than a comparible piston engine (V8). A fuel infection system can offer more torque than a carb for example, but then we're getting into all that computer junk and sensors that go along with it. Then there is the turbo option (see FI option). There is also the SC option which allows a rotary to have V8-like torque with rotary-like instant pedal response without the weight. It runs hotter than stock, but a large rad and oil cooler are already a given in anything other than stock.

I've seen a rotary in a B2200 or B3000 4x4 and the guy said it wasn't geared very well because it was still using the stock geared drivetrain. I think the engine was street ported with a light flywheel because it died on him while he was trying to pull away from a hill. My truck doesn't have those kinds of problems. Viva la heavy stock flywheel! I have no idea what became of that RX-4x4.

By the way, NSU, the company that builds the Wankel engine, went out of bussiness recently :( RIP. Yes, there is a real Wankel rotary engine and there is also a Mazda rotary engine. Sorry, but whenever I see the word Wankel being used to describe the Mazda Rotary, I always picture the Wankel engine instead. Just because Dr Wankel invented it doesn't necessarily mean that my adjustable wrench is made by a company called Crescent :). (if you think that's bad, you should check out Felix Miata's naming recommendations)
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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repuguru


Redlining
Posts: 319
posted January 07, 2002 10:32 PM

Can o' worms

Damn this place has turned into a graveyard of threads so I figured I'd stir this pot one more time.
Yeah Jeff anything over 1500rpm is HP and the high torque curve(3500rpm and up) on most N/A Rotar Motors would be useful in some situations, but most of the off roading situation I have encountered with my FJ40 LandCruiser, and this is my personal expierience in the S.E. U.S., is crawling around between 1000 and 4000 rpm. Usually just above idle. Now I don't do much mud boggin' and if you are able to go faster than 10mph you probaly don't really need the 4WD engaged anyway. Momentum will carry you through.
I am not saying the Rotary is not a good power source to use for grunt work in some 4x4 situations (Mud boggin', high speed off road). And that is if it is set up properly. But compared to a big lumbering Cummings Diesel or most inline 6cylinders for that matter its just less than ideal.

Supercharged 13B, Automatic w/modified torque converter, Marlin Transfer case. Insane low gear ratios w/air lockers F/R, 33' SuperSwampers.

Thats just sorta the direction I'd head in if I had plenty o' funds and time. And if a 20B could not be had reasonably.

       
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Jeff20B


Moderator
Posts: 661
posted January 21, 2002 12:28 AM

Well, I think my first off road vehicle to use a rotary will most likely be my baja. The engine will probably have small ports for more torque as well. Hmm, my REPU engine could go really nicely in it I think. I've just got to sort out which parts are going into which vehicles first. I could get away with a 12A if I wanted/needed to.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Klaus43


Rotorhead
Posts: 1259
posted January 21, 2002 11:50 AM

hey jeff-
In case you missed it: there's a rotary to vw adapter setup on ebay right now...just search ebaymotors for all categories under 'rotary'...
Also, remember your torque curve will be influenced not only by port size and choice of intake/ intake runner length, but also header/exhaust design: length, diameter, and at what point, if any, the two rotor's exhaust collect...
I've long been curious if anyone's ever explored expansion chambers for the rotary...seems to me they would make sense, if the design & construction can be cost& weight effective...
And what of that 'Predator' carb I've heard (so little) about? Seems it's a more basic, MC type design...could it be just the thing for the holley blues??? Anyone got any info?
And while we're dreaming: how about those superchargers Atkins is building? They sure look sweet! Makes me oh-so-tempted to go severely into debt to build one of my REPU's the way it oughta be!
Anyhow, "keep on truckin'" --KLAUS

       
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repuguru


Redlining
Posts: 319
posted January 21, 2002 03:22 PM

Yeah the Atkins Supercharger is a neat item. It is sorta tough to intercool a suck thru system though. Which is what their version of a roots style blower is. Since there is not an intercooler, intake temps will be high ,so you really have to keep the boost levels down. 6 or 7 psi tops.
I am in a forum over at Mazspeed.com talking about this very subject in one of the threads. We are discussing H2O injection. Which actually sprays a fine mist of H2O into the hot intake charge. And we all know H2O cools better than air. I do have one example of a guy here local who is able to push 18psi thru his stock 12a. And has been doing this since the early 80's. With H2O injection. I am slowly but surely finding out what will allow me to dial up at least 10psi in my high compression 13b and allow it to live thru it repeatedly.

____________
77' REPU plus a few spare parts
for it.
85' GSL-SE
83' GSL

       
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Klaus43


Rotorhead
Posts: 1259
posted January 26, 2002 08:37 PM

boost, temp., H2O injection, durability...

By all means Guru, do tell..."it's nice to share"! What level of build/type of setup is your local pal running to allow him to achieve durability at such levels of boost? What can we learn from what you're learning? How much is a water injection setup? I, for one, am clueless beyond the basic theory of how it works...and theory is nice, but no substitute for years of practical experience, especially if it's years of success. Thanks! --K

       
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Jeff20B


Moderator
Posts: 661
posted January 27, 2002 03:23 AM
Edited By: Jeff20B on 27 Jan 2002 03:26

Thanks for the VW adapter info! If I had an extra $200 sitting around I would have purchased it.

Ok, I've never needed to use my powers of mod before, but Dan is very busy and this thread is drifting from 4x4 to forced induction. I know it's ok to have some drift, but some people seem very interested in boost related stuff. Go ahead and start a new thread about forced induction if you want to. Thanks :)
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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repuguru


Redlining
Posts: 319
posted January 27, 2002 08:38 AM

Well you had discussed the supercharger in your first 4x4 post. I guess we were just running with the ball. Lets take our toy and go play somewhere else Klaus.

       
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted January 28, 2002 11:12 AM
Edited By: rotarynews on 28 Jan 2002 11:12

Forced induction

Please go here for the forced induction thread
http://www.mazdarepu.com/board/viewthread.php3?FID=1&TID=78

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