flyboy333

The weight issue shouldn't be huge, the V8 might add a few pounds but it should really be negligible at the end of the day, thought where the poundage sits should favor the Renesis. Thank you for giving me a straight answer about the Ren. in that there's almost no documentation, I'll really have to think long and hard about it and go on the RX8 boards to ask them about how tough the ECU is to get to run without having the rest of the car around it. It would be cool to have something that unique, but at the same time, it would be cool to stomp on C5 corvettes... I thought of going with a VR6, but I can't see the advantages of having a very tall iron block V6 with no natural RWD tranny configuration.

Actually a T-5 is probably a bit lighter, and I don't really need 6 speeds with an 8, it has that whole torque thing going on. I liked my 8's manual though, very nice throws for sure.

cyipher

iTrader: (1)

really just depends on what you want the car for, ive only delt with the v8 sides of things and i can tell you in the fb they overheat like a sob when you start making power with them. the engine comparment is too small and the v8 radiator swap is the same, undersized. with that being said i would prob tell you to go 13b turbo and skip then rennie motor, I guy who i worked with had a rx8 and that thing was a slug but the fb i would imagine is about 1000 lbs lighter too. All just depends on what your looking to do with the car and how much fab skills you have. Im sure no one makes a aftermarket harness for the rennie so thats all gotta be made or modified.

j9fd3s

iTrader: (3)

that right there is the problem. in theory since they can do some programming on the ecu, they can do it, but the one 1st gen we've all seen with the rx8 engine has the whole stock rx8 CAN network and all the pieces, like the gauge cluster, and climate control unit

flyboy333

I can figure out a workaround for overheating, and I'm not going to have a stock front end but a big gaping hole type of front bumper, mostly for aero to keep the front end from lifting at 150 or so mph. It's the whole fab skills thing that's getting me, I don't have a lot of experience fabricating or much in the way of machinery to do it with. For this reason the V8 is looking damn tempting.

This does seem to be the crux of the issue, and combined with the fact that there doesn't seem to be a huge weight savings to go with the huge increase in complexity and loss in power and torque makes me think that doing a V8 would be a less frustrating project. Keep in mind (everyone) that this isn't a redneck status 500 dollar stock 5000 rpm 302 swap into a peg-leg burnout 81 GS or anything like that, this is going to be a chassis upgraded immensely with regards to handling and a screamer stripped down 6500 RPM minimum redline block with as much weight savings as possible and as money allows for. This is going to be a car that will simply eat most other cars for breakfast in a straight line and around the bends. Canyon driving is the one thing in life that makes me truly feel alive. I design accordingly.

Ken7102

also a renesis is more performance, my cousin has a 13b 1st gen that destroyed all the v8s in the competition so the renesis should be great

flyboy333

Oh yes, The Competition, I enter it all the time...

Box_Man

A 13B-MSP is going to require far less fabrication than any V8, unless you're buying a kit to put the engine in. Even then, engine mounts aren't hard to make, and neither is a transmission mount. Ditch the RX8 ECU and run it on something like Megasquirt 3, it can do everything the stock ECU can for that engine, and then some. Then there's the whole nose weight issue, You said you want to build a "Canyon killer", the V8 is heavier (maybe by a small margin if it's all aluminum), but it's focused further forward than the weight of the rotary. Hanging more weight forward of the front axle centerline is never good...

flyboy333

Of course that's never a good thing, but is it worth the fabrication needed? And you have the fabrication needed for each option backwards, 160 dollars worth of kit is all the V8 needs to sit nicely, and although the megasquirt might be able to handle the injectors, there are also the variable intake and ports that need actuating as well as the Drive by wire system, and after looking at it and the whole CAN bus system it seems like a real pain in the *** for 250 horses at most with minimal torque to get me through tight corners at low revs. Not that it would wreck my world but there is a tried and race tested option that I can go down to pomona on the 17th and pick up.

I don't know how to stress that the weight difference is really not that great, maybe 100-150 lbs, which is not good but at the same time also not going to ruin my distribution, heck the Evo doesn't have the best balance stock and they do pretty damn well up Seventurn. I am going to be pulling the headlight motors next and replacing them with prop rods to save a few front end pounds. Long story short, I think it's pretty clear that the MSP would be a cool engine for someone with lots of fab skills and or money, but I don't have either of those.

cyipher

iTrader: (1)

ill have to find my weight sheet, but my mazda with a 8.8 and a v8 swap was almost 50/50 dist.

Box_Man

All the variable junk in the intake is no problem as it's either on or off (open or closed) and can be controlled by an RPM triggered output. Drive by wire is a non-issue too, use a mustang throttle body or any appropriately sized single bore throttle body. Any and all RX8 related electronics go out the window and in the trash (or for sale). Either you build engine mounts for the 13b or you re-engineer your radiator shroud to keep your $20,000 302 from blowing up when it can't get enough cooling air through the radiator. It's going to be roughly the same amount of fabrication either way you look at it, one will make less power, but run infinitely better and WILL corner better. The other will be very fast in a straight line, be a handfull around the bends on these canyon roads and will require frequent carb tuning to keep it happy (assuming you put a holley on it). Also, if you're that concerned about weight that you'd be willing to eliminate the headlight motors, I can't fathom why you don't care about that extra weight over the front axle. It's not just that it's only "100-150lbs" (which is a lot of weight), it's that it's shifted over the front centerline of a front engined, rear wheel drive car with a solid rear axle and poor suspension geometry.

flyboy333

You don't say, it would be nice to have some concrete evidence to silence the naysayers, which are a byproduct of doing something out of the ordinary as far as I can tell...

You had better calm down, because you're starting to spout nonsense. Not only is there going to be almost no difference in the handling (it's the steering system I would more like to change) I don't need 20k to make a 302 make 350 horses, more like 5k if i want to do it well, and I would have to fab a radiator for either of these engines, so once again, much more fab to get a Renesis to mount into the engine bay. Also, no carb. If the weight difference between the stock and 302 even gets to 100 lbs the battery relocation and other bits and bobs taken out of the engine bay should do wonders for keeping the distribution similar.

I did not start this thread to be told why a V8 will not work, I started it to see how feasible a Renesis is, and from the looks of it, it would be in complete unknown territory, which is not somewhere I can afford to be.

jtspells

If you are looking to build something custom go for the Renesis, if you want quick cheap and something with support to fall back on go for the V8.

Good luck.

Box_Man

Sounds like you already had your decision made before you even started a thread about deciding between a rotary or a v8. I never said it wouldn't work either, I'm getting at the fact that one option will result in a car that will be very different to drive than a car built under the other option. A Renesis is very feasible, if you can think creatively. Whatever you do, do quality work and enjoy the car.

ProjectD

iTrader: (15)

This really made me lol.

j9fd3s

iTrader: (3)

that's a good point. its not technically true, mazda has published a couple of SAE papers, and new model training books that really explain everything on the engine, they really even gave enough info to have a good start on programming an aftermarket ecu. it would take a lot of time.

the other story i have, is my friend was taking me around infineon, and we came out of turn 11 right next to us was a factory 5 cobra. to our surprise the 8 pulled on the factory 5, all the way until after turn 1. the factory 5 is 2000lbs, and on slicks, so it should leave a showroom rx8 in the corners.

Troux

iTrader: (6)

Man, there are a TON of Civics for sale at the local Honda dealerships. They've gotta be the worst car in the WORLD!

flyboy333

This is correct, I was originally planning on a V8, and after looking at Renesis prices and thinking back to my 8 I started to reconsider, and that's why I wanted to throw the idea out there for those who have seen far more than I and who have way more knowledge to throw down their opinions on. It seems that this is not something that's even been done more than once or twice, so I'm quite hesitant after knowing this.

...me too

Thank you, this seems to be exactly how it has broken down after hearing some of the better informed voices that have piped up in this thread.

I know it's not entirely unknown, but my point is that it is not a well known swap in any way, and as you can see in my build thread my shop is a space in the driveway and a bit of the garage, not the most conducive for fabrication and I don't know ECU programming very well though I could learn. I used to have an 8, speed though is not the issue, as I have stated. Also just to point out the FFR is about 2400 lbs and with a stockish 302 it should be faster than an 8 but not a ton faster, and in the wrong gear or hands I could see how you could pull on one.

That's the only reason to sell a car ever!

ProjectD

iTrader: (15)

Damn look at all these clunkers FS. These cars must really suck!

...Cars for sale...

Lots of squirrely logic here

ProjectD

iTrader: (15)

On a more serious note....OP, you are on a "slightly" bias forum here. No rotards will advise you to "ruin" an rx7 with pistons. Likewise, most piston swapped owners will tell you to drop the rotary like a bad habbit.

That being said you really need to decide what you wanna do on your own. If you need answers to cost qustions by all means ask. But itwould be wise to ask those who have experience (or at least a clue, don't bother asking a rotard how much it will cost to swap a v8 and vice versa)

That being said, I've always wanted a REW swapped 1st gen...

flyboy333

I'm well aware of the bias here, and I figured it would work to my advantage in that if it was easier to do a Renesis swap then it would be pointed out right away. The fact that everyone wants me to do it is irrelevant, but the fact that they think it will involve a lot of design work is exactly what I wanted to find out. I don't know if calling them rotards is a good idea... I like those engines myself you know.

ProjectD

iTrader: (15)

Don't get me wrong I love the rotary engine as well, hence...I just think it is silly to be so close minded about other options. Let alone trolling the "other engine conversion" section trying to keep people from defecting lol.

flyboy333

Haha I noticed you saying that, and yeah haha I guess it wasn't deemed a prudent question for FB drivers. Such is life, those who get to mod are those who get to decide what goes where. Perhaps they sensed an impending flame war? Seemed civil enough to me, or at least as civil as mentioning anything piston-filled on this board can be...

dream36realms

iTrader: (4)

You know how I feel about this. I would say ignore anyone except yourself. however it is true there are lots of V8 7's. Heck, there is even v8 8's. I would go with a pull out motor and build one on the side. when you are done building it you can simply replace it and sell th epullout.

kevk

putting a Renesis in the 7 would be a lot easier then a v8 since the mounts ar not that diffient you would just have to a cradle for it like the 7 already has


if you look at how its mounted it should be easy to figure out how to mount it when i get back to Virgina i can even figure how make a cradle . as far as the ecu it mostly connected to the gauges although it does talk to other systems like the steering computer and the abs and there are after market ecu's available out there check the rx8 forum.

thejallenator

iTrader: (14)

you sir are very wrong. it is a bolt on putting a v8 into these cars. since it has become so popular to ditch the 13b for something a little better, companies have been making a killing selling these kits to people. takes literally no fabricating at all to stick a v8 into the car. al lyou have to do is know how to use basic tools and you can do a v8 swap. no need to create a craddle foe the rx8 motor. and hell if youre scared of wiring a sbc needs like 4 wires to make run, talk about simplicity, no need for a ecu or anything of that sort

and also when the v8 is in the car its positioned pretty far back. its not like all the weight it over the front wheels. you can still keep the 50/50 weight ratio if you do it right

see i told you they were gunna be up your *** to keep it rotary powered.

oh and also whoever said the 6 speed would be an upgrade, go hit tjhe books. its not