Zebvance Posted March 17, 2014 Share Posted March 17, 2014 The renix 4.0 in my mj is getting old and wore out. It's getting to the point where it is dumping more oil in the air box than the Exxon Valdez (yes I have replaced and cleared out all the CCV system). I would like to put a new engine in it next year after I graduate. Ill prolly go the easy route and just get a "complete" stroked 4.7 and be done with it but it is always fun to throw around the idea of possible engine swaps. When I think of a good nominee for a mj engine swap I keep in mind a few things. -Will I be able to keep it cool in the engine bay without a outrageously expensive custom radiator? -Will it be comparable or preferably smaller in size and weight than the 4.0? I don't want to have to reinforce the unibody just because the weight of the new engine and I don't want to stuff this big engine in a engine bay that's to small for it, because I know I will just have the issue as referred to in the bullet above. -Will it produce enough power? -Will it be a PITA to work out the electronics? I know there are a few very common swaps. Such as the Chevy vortec family v6's and v8's and I have seen a couple 4bt's done and the Mercedes diesels. With the v8's I hear of problems keeping them cool and I know it requires a good bit of firewall modification work. With the diesels, when I think of having to run a whole new fuel system it steers me away. Not to mention with the Mercedes engines it doesn't look like much gain in power for a lot of work. So to the point, the thought came to me when I passed a rx7 in town. I have always thought those little cars were cool and I hear of them getting some ridiculous numbers as far as power goes. I know they have a 1.3 liter rotary engine which are known for being torquey little motors. After doing some research I found that the last model that was sold in the US was the third generation of them (1993-1995). It is a 1.3 liter twin turbo rotary engine. It puts out 255 bhp and 217 lb-ft. Not as much as a stroked 4.0 but keep in mind that is stock. Do some bolt ons and maybe swap out the turbos and I'm sure you could easily get the power numbers in the 300's. Now reading this is what jumped out at me and really screamed a great nominee, "The system was composed of two turbochargers, one to provide boost at low RPM. The second unit was on standby until the upper half of the rpm range during full throttle acceleration". Sounds perfect for offroading right? Well to me it did at least. Lower rpms and slow speeds is where most offroaders spend their time right? Well except prerunners and mud racers I guess. But it sounds like it gives a good band of power all the way through the rpms to be the best of both worlds. The next things that spoke out to me was the weight of the engine. Around 225 POUNDS!!!! That's less than half the weight of the 4.0, and we all know less weight = faster! Next was the general size of the engine compared to the size of the mj engine bay. It is plenty small enough to take up what I'm guessing is the same amount of space as the 2.5, 4 cylinder. Therefore I would think no modifications to the engine compartment would be needed. Also plenty of room around the engine for air to flow which I would think keeping it cool would not be as big of a issue as the v8s have. But I do know turbos put off ALOT of heat so I'm not sure on that one. Now as with every engine swaps there are questions to be left and they are not small ones. such as, - Can you use the transmission that is mated to the rx7 and how will it mate to the np231 jeep transfer case? - Or can you just get some sort of adapter plate to mate the aw4 (in my case) to it? -What about the electronics? Where to start with that? and the main question..... - How much will it end up costing? Anyway that's my random thinking for today when I was out in the work shop all day filling orders. Hopefully this gets yalls mind working too wondering what other never done swaps might be possible. Let me know your thoughts on this. I feel like it is a fun discussion to get going. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 17, 2014 Share Posted March 17, 2014 Can you rebuild a piston motor yourself? If not, a rotary is beyond you, don't even try. Link to comment Share on other sites More sharing options...
carnuck Posted March 17, 2014 Share Posted March 17, 2014 Exactly. Even with the special equipment at Hayes Rotaries it was hard to build the 1.1 or the 1.3L but the last one in the US was the RX8 turbo @ '06. There's even a couple for sale here in Seattle http://www.royrobinsonsubaru.com/tcd/inventory/used/Mazda/RX-8/?tcdkwid=25289952&tcdcmpid=19758&tcdadid=33362443421&locale=en_US The RX7 remodel may be coming back in 2016 as a hybrid. .33L (not a typo) with electric. http://www.autocar.co.uk/car-news/new-cars/mazda-rx-7-return-2016 Link to comment Share on other sites More sharing options...
Zebvance Posted March 17, 2014 Author Share Posted March 17, 2014 Can you rebuild a piston motor yourself? If not, a rotary is beyond you, don't even try. Yes, me and my brother rebuilt is fox body mustang 5.0 and put a vortec supercharger on it. Still runs great to this day. I'm not going to say I that I know much about rotary engines, but I feel as though I am fairly mechanically inclined, there hasn't been much that I have attempted and not been able to do. But keep in mind, I never said I was going to do it, just said it was fun to throw around the idea. I would never attempt something like this with out many hours of research and a bullet proof game plan. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted March 17, 2014 Share Posted March 17, 2014 I think those motors like to rev high before they make their torque, but I could be wrong. If you want low end pulling power and good top end, I'm not sure a rotary would be my first choice... But, it would make for an interesting swap. You certainly would be the only one I've heard of doing such a thing. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 17, 2014 Share Posted March 17, 2014 You would be better off running a small turbo traditional motor. Link to comment Share on other sites More sharing options...
GirsMJ86 Posted March 17, 2014 Share Posted March 17, 2014 A rotary would be interesting, but I'd rather grab a 6 bolt 4G63 Mitsubishi engine and turbo the thing. Hell of an engine. I have a friend with a 1st gen Talon TSi AWD and I'd bet he is pushing over 300hp. It's just a little four banger so space wouldn't be an issue. Hell if you wanted to you could probably grab the entire AWD system and stick it in the MJ somehow. I've seen crazier things. The rotary is poor on gas, uses oil like crazy (designed to though), poor emissions, and seal issues. On the plus side, you never have to change the oil, power to weight ration is great, no engine knock, and very little vibration. But it is really meant for performance. It shines when being pushed, but in daily commute it sucks. Link to comment Share on other sites More sharing options...
Incommando Posted March 17, 2014 Share Posted March 17, 2014 There are many stock engines that push 300 hp that can be had for cheap. Yes you can throw enough parts at that 4-ricer to make those numbers but my observation is that longevity suffers and you can build more HP for less. I can post pics of my completely streetable Road Runner that can dip into the 10's and the engine is going on 12 years with no repairs. I have right at $5k in the whole car. Pie-in-the-sky daydreaming is one thing but many of these engines, like a rotary, have issues (as mentioned above) that make them pretty unsuitable for use in a jeep. Heck, the rotary made great power for its size but you had to wind it to 10 grand to do it and that got you poor even by V8 standards fuel economy and other issues. If it was so wonderful why didn't Mazda use it in all of their vehicles? The last version here, the RX8, was a horrible car with all sorts of problems. Use it as a 4x engine and use the 4x? I can't imagine why you would try. If that 200# is so important run alloy wheels, small tires, and lighten a few things and there is your 200# in a much more sensible weight reduction plan. Is speed that important to you that the weight of a passenger would make a huge difference? Then ditch the transfer case and front axle/driveshaft by doing a 2wd swap (reduces parasitic drag, as well) and leave the tailgate off. You can make about anything work with enough time, skill, and money. But unless your goal is to be eccentric why would you? Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted March 17, 2014 Share Posted March 17, 2014 There's no replacement for displacement . Do you consider a Subaru wrx motor a ricer? If so how about a grand national 3.8 turbo? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 17, 2014 Share Posted March 17, 2014 I think its good youre trying to find ideas like this, but a rotary is not a good idea. I'm a Mazda dealer tech, and most of the RX8's that come in have had 2 or 3 motors put in under warranty within 80000 miles. And like was said, power isn't made until the higher RPM's (5-10K). They are fun to drive though, but I wouldn't own one. We actually considered buying one before I was with Mazda.... glad I didn't! They are beautiful cars, but at the time the price put us off. Your best be is to go with whats proven. That way youll still get to drive the thing and not mess with finding or making custom parts that may or may not work for an engine that never been swapped into an MJ before. Good luck, and let us know what you end up doing! Link to comment Share on other sites More sharing options...
FrankTheDog Posted March 17, 2014 Share Posted March 17, 2014 LS and done. Stock motors put out anywhere from 280 hp to 600+. Novak makes the parts to bolt it in. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 17, 2014 Share Posted March 17, 2014 Very original. Btw, a gm buick 3800 puts out more hp than a 4.0 and is far more efficient...mid 20s for mpg In my MJ. Link to comment Share on other sites More sharing options...
GirsMJ86 Posted March 17, 2014 Share Posted March 17, 2014 Yea... an LS. oh boy. Sarcasm aside, was the OP even read? The whole idea behind the rotary was to avoid the hard to cool V8s. You want to use a V8, and be like 90% of the people out there who resort to an LS when they do a swap, get a full size truck. The 3800 or Vortec 4300 are a wiser choice for an MJ if you gotta go GM. Link to comment Share on other sites More sharing options...
Incommando Posted March 17, 2014 Share Posted March 17, 2014 There's no replacement for displacement . Do you consider a Subaru wrx motor a ricer? If so how about a grand national 3.8 turbo? Ricer? Yes I do. Moderate horsepower in an economy car has always been a recipe for speed but a WRX is still an Impreza economy car no matter how you slice it. I know that the Impreza WRX people hate to admit that and the vast majority that I see go so far as the remove the Impreza badges to hide its humble 148 horsepower and slow as a dickens beginnings. The WRX and WRX STI are not models: they are merely option packages on an Impreza. As to the other: To keep it all Buick apply a similar turbo tailored to a 455 ( 7.4L ) and where would you be? Far far ahead of the 231 with 245 horsepower. The 455 would have greater HP without the turbo. In fact most naturally aspirated V6's found in today's family cars easily surpass the GN's output. The Pentstar 3.6 has a smaller CID & 291 hp in a Charger. Do you still want to crow about that 3.8 turbo GN? I wouldn't. The later 3800 supercharged engine made an underwhelming 220 hp. That there is no replacement for displacement is absolutely true as the same mods applied to the larger displacement engine will net greater gains. Period. The average 3.8 made less horsepower than a 4.0 and the 4.3 just got into the ballpark. The obvious answer is a 4.0. Link to comment Share on other sites More sharing options...
Incommando Posted March 17, 2014 Share Posted March 17, 2014 I think its good youre trying to find ideas like this, but a rotary is not a good idea. I'm a Mazda dealer tech, and most of the RX8's that come in have had 2 or 3 motors put in under warranty within 80000 miles. And like was said, power isn't made until the higher RPM's (5-10K). They are fun to drive though, but I wouldn't own one. We actually considered buying one before I was with Mazda.... glad I didn't! They are beautiful cars, but at the time the price put us off. Your best be is to go with whats proven. That way youll still get to drive the thing and not mess with finding or making custom parts that may or may not work for an engine that never been swapped into an MJ before. Good luck, and let us know what you end up doing! I will add that such a swap would be interesting/eccentric...just not very sensical. Link to comment Share on other sites More sharing options...
Comanche County Posted March 17, 2014 Share Posted March 17, 2014 I kinda like the idea of a having a Wankel engine, not necessarily in any vehicle. Just as a garage ornament and talking piece. I saw an Rx7 in the yard the other day and did the same bench racing idea. But man, those things are full of all sorts of vacuum lines, oil and coolant lines etc. It would be interesting to see one in a Jeep but I don't think I'd attempt it. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted March 17, 2014 Share Posted March 17, 2014 I'm not trying to down anyones ideas . The gn motor with a different turbo will run 11s / 12s with very limited work there a v6 instead of a v8 so more clearance for the radiator etc . The op doesnt want a v8 and he wanted a turbo . I'm just responding to what he asked . I like ls motors and big blocks etc but when you're confined to a certain size sometimes it's bang for the buck . Link to comment Share on other sites More sharing options...
87sparTruck Posted March 17, 2014 Share Posted March 17, 2014 There's a reason why everybody does the same swaps, they work and are beneficial enough to go through the effort in the first place. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 17, 2014 Share Posted March 17, 2014 In the early 70's, AMC was looking into getting Wankels for their cars and trucks. They'd signed agreements with Curtiss-Wright, but then switched to one GM was developing for use in the Vega, designing the Pacer around it, with plans for use in "Jeep-like vehicles" as well. GM canned the project though and AMC was forced to hastily redesign the Pacer to accept the straight six to be able to launch it on time. So it's not the first time someone's brought up something similar. Had GM not "postponed" the project, there could have been factory Wankel Jeeps. A Wankel would definitely be a unique, oddball, eccentric swap. And you wouldn't see too many of them around (or any), so it would have it's own cool factor just for having done it. I personally see that as the only advantage to it. Sure, you can get decentish power out of them, at high rpm, but they suck fuel and don't make all that much power to show for it. And the ones Mazda runs, you'll be very lucky to get 50,000 miles between rebuilds, a common issue among Wankels due to the apex seals which no-one really has solved. Would it be cool? Yes, definitely. Practical? Not so much. I personally wouldn't do it, because I like my stuff to be a little more reliable, but I would be very interested if I saw someone else had. I like odd-ball things. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 17, 2014 Share Posted March 17, 2014 There's no replacement for displacement . Do you consider a Subaru wrx motor a ricer? If so how about a grand national 3.8 turbo? The average 3.8 made less horsepower than a 4.0 and the 4.3 just got into the ballpark. The obvious answer is a 4.0. The 3800 I put in my MJ was faster than any 4.0. The series 2 sat at 230hp, 240 ft/lbs torque. It beat out the 4.0 h.o. On power and economy. I averaged 26mpg. A 4.0 cannot touch the 3800 for power and economy. I like 350s and LS swaps, but they are far from original. A 2.8 vm CRD would be great, but my god is that expensive. 4bt are great, but equally expensive. Except they are idiot proof, which is beneficial. Not sure what to tell you guys except that there are great choices in motors, and if a v6 is an option, the best economy v6 ever made is the buick 3800 Link to comment Share on other sites More sharing options...
Zebvance Posted March 18, 2014 Author Share Posted March 18, 2014 Great discussion we got going on. For me as a few have mentioned, v8s are out of the question. I don't want to deal with the firewall mods and trying to keep them cool. yall bring up a lot of good points about the wankel engine. Main one being the life span of them. I didn't know that they would need rebuilds that soon. Even though what ever engine I end up swapping I'm sure will never see more than 20k. In the past 2 years of owning this truck I have put about 4000 miles on it. With that in mind fuel economy is just not the biggest concern that I have. However reliability is. My brother (the same one as mentioned before with the 5.0) also has a 05 wrx. To say the least I'm just not that impressed with it. My 08 v6 ford fusion could take the wrx in a 1/4 mile I feel like. My parents also have a Subaru wagon with the 6 cylinder boxer in it. That one is more fun to drive...I just feel like working on that engine would be a huge PITA seeing as how the heads are horizontal. Link to comment Share on other sites More sharing options...
benjy_26 Posted March 18, 2014 Share Posted March 18, 2014 I've been thinking along the same lines as you. I want more power than my 2.5, but want something different than the 4.0. I'm seriously considsring going with a Toyota drivetrain. I just gotta figure out how to make a 3SGTE mate up to a truck tranny. OR... I may say screw it and just use a 1UZFE! ;) Link to comment Share on other sites More sharing options...
Zebvance Posted March 18, 2014 Author Share Posted March 18, 2014 funny you say that because my buddy is scrapping his mr2 and he has a fresh rebuilt 3sgte with 0 miles on it sitting in his garage with no plans for it that I know of. BTW where are you located in Tx if you don't mind me asking. Link to comment Share on other sites More sharing options...
Zebvance Posted March 18, 2014 Author Share Posted March 18, 2014 Also just so we are on the general engine swap discussion. I know another buddy that has a couple of Comanches in town and in his sporttruck he is swapping a amc 360 in it. It looks like he has been working on it for a while from the looks of all the crap piled on top of the truck. Who knows if he will ever get it done. But he mentioned to me that he had to notch the frame rails and a lot og other work to fit it in. not sure whats holding him up from getting it running. Looks like he has most of the hard work done.... His other mj is his wheeling rig and he has 430k on the 4.0. Its parked about to get a built 4.0 he scored of CL put in it. Just thought I would mention that... Link to comment Share on other sites More sharing options...
johnj92131 Posted March 18, 2014 Share Posted March 18, 2014 I actually purchased a new Mazda RX3 with the rotary engine in 1974. The car went like a bat out of hell for the time. Turned 7K rpm in a flash. Mazda also sold a rotary powered minitruck that was a real hot rod in it's time. The engine was smooth and powerful. Also suffered from some issue that lead to short life. Later versions of the rotary supposedly cured the endurance issues. But lack of low end torque was never really solved, even with the very latest RX7/8. I like the KISS principle. That tells me to stick with the Jeep inline 6. The factory solved all kinds of problems to deliver a power plant that lasts for years under all kinds of conditions. That covers both the 4.0 and the stroker versions of the stock 6. Next keeping with the KISS principle, I would look at the aluminum block, aluminum head Chevrolet V8 engine and a GM transmission (6 speed automatic). Close to 100 lbs. lighter than the Jeep 6, just as good or better mpg and so much smooth torque over a very wide band. Yes, you are going to put effort into the cooling problem. (Remember, this is not a factory solution). But lots of support and people who have been there, done that - some good, some bad. Also, considerably more $$ that the 4.0/4.5/6. No matter what you do, you still have a 25+ year old truck. Keep that in mind also. I keep mine because it is relatively cheap to keep for what I do with it. Link to comment Share on other sites More sharing options...
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