ghetto 4 rotor build
 

That's right. Doing a 4 rotor on the cheap.

It's going into a GSL-SE. The car will be CYM (competition yellow mica; 3rd gen color) so we already painted the engine bay. The rest of the car will be done after the engine is installed.

The stripping of the old engine and painting the bay was the first step. The second was to put together a mock up engine. Third to test fit it. Fourth build motor mounts. Fifth... well, I'll let this first group of pictures speak for themselves.

https://www.rx7club.com/forum/attach...d=229803&stc=1

https://www.rx7club.com/forum/attach...d=229804&stc=1

https://www.rx7club.com/forum/attach...d=229805&stc=1

https://www.rx7club.com/forum/attach...d=229806&stc=1

https://www.rx7club.com/forum/attach...d=229807&stc=1

Jeff- you have too much time on your hands! Nice, let me know when you get the ghetto e-shaft done....

cool you could put 4 turbos on it lol. that looks cool.

No kidding, dont say your just gunna cut two and weld them togather.
But it does look nice

Jeff, you've been on a roll lately, i know know you've been making me think much harder of enginge builds, combinations of parts and porting/air flow dynamics. This is by far the wildest one yet. Very interested in how you plan on constructing the e-shaft. That should be an adventure initself.

Are you going to need to cut into the firewall or install the rad at slat or even flat to get the clearence needed?

Yah right...
4 rotor 12a.... this is the one we all dream about....

Now thats a project...

What intermediate plates are those?
What are you gonna do about stat. gears for the middle rotors?
heck... are you using tension bolts from either end of the block, or are those just mammoth???????? Going for any bracing on that big daddy, I forsee a bit of torsion there!

Tell us more!!!

+1 what are you doing for tension bolts and eshaft?

What about the distributer?

PP that beast haha

Here is another idea!
Oil pump and water pump, do you think the stock pumps can put out enough to lube that beast????

But if you get the e shaft to work i have an extra 5sp Titanium internals tranny. Youll need it.

Wow, thats awesome Jeff. I, too am interested in the eshaft making. Keep us updated.

Jerry, the ghetto e-shaft should be actually pretty easy to build. I already know that in order to get the awesome 4 rotor exhaust note, you need a rotor to fire every 90°. The prefered firing order is 1324 where:

L1 0° (TDC)
L3 90°
L2 180°
L4 270°

I even figured out a ghetto direct fire ignition system (currently leading only*) that will not only fire each plug at the correct time, it will also provide the cool late leading or 'wasted' spark like DLIDFIS and 2GCDFIS that we all know and love. :D Very simple, very little to go wrong, based on parts that are easy to get, totally ghetto. :D I'll get more pictures after I've built it and my camera is working again.

*plans to add trailing are for possible future MegaSquirt project. For now though it will be NA carbed with a dizzy. No real need for trailing right now since it doesn't really do much if you're NA with a direct fire (late) leading ignition. Test it yourself on the dyno some day. You'll see what I mean.

One more picture of the engine bay showing tilt of engine. I think I got it level before constructing the motor mounts.
https://www.rx7club.com/forum/attach...d=229826&stc=1

You will have to have a shaft made, you can not weld two togather and balance it.
The centerplates will not wiggle on, you almost need to have a key in lobe something you use some high strenght set screw on.
But if you can work it out more power to you i know you can buy the 4 rotor 4 piece shaft for about 4-5,000.00 dollars.

very cool project...and nice job on a correct 4-rotor firing/exhaust note!!

openshot, gonna be NA for now with no plans to go turbo. The future is open though.

Nick, that would be too easy. You gotta be able to assemble and tear down the engine. :D

trochoid, yes I've been doing quite a few projects lately now that the weather is getting better. I always try to do something new if I can, and learn from it. The latest is an '84 automatic 12A car that needed some TLC. The Nikki and mani thread showed the carb and intake that I modded for it. I got some more done yesterday but my camera's battery gave out when I was shooting the progress last night.

No need to cut the firewall. Using 12A rotors, the whole engine is just short enough that no mods are required. Infact even the stock front sway bar is still in place. Can any 2nd gen guys say that with a shorter 20B? :) It'll get an RB bar and probably Eibach springs (to help handle the extra weight) after the engine is done.

Gen1onr, GSL-SE intermediate plates because they have motor mount studs on both sides. This project would be more difficult if I was using 2nd gen intermediates because they only have horizontal studs on one side and vertical on the other. Plus the extra length of the 13B rotor housings would complicate things.

The gears can be machined down and the intemediate hole can be machined out a little. That is to say the section of the gear that bolts to the plate can be machined down, not the gear itself. lol SLots must also be added to allow the oil to drain back down into the pan.

Tension bolts, long threaded studs, I'm not sure yet. I've already fabbed a couple to keep the mockup together. Dowel pins too. They only go through the rear plate and thread into the front plate.

The motor mounts will add a bit of strength. I overbuilt them. :)

13b4me, the distributor will be direct fire only. It'll have a cap but that's just to keep the dust out. :) I'll mod an '81-'85 and take advantage of the 4 rotor's natural 90° firing interval. I won't spill the secret of just how to do it yet. ;)

Jeezus, yeah, that's the only way. Those tiny GSL-SE intake ports are too small.

Nick, waterpump, yes. Oil pump, maybe.

We'll use the tranny until it breaks. Same for the rear end. No sense fixing something that ain't broke. Breaking something is half the fun sometimes. It means you had a good day. :D

twinkletoes, yeah. I bet this thread will get updated fairly often as things progress. I can't post any new info at this time because A: the car isn't here and B: my camera isn't working any more.

I can post one more picture. This is from when I pulled the mockup and tore it back down. It's sitting next to another mockup. :)
https://www.rx7club.com/forum/attach...d=229832&stc=1

I'll get a picture or two of the motor mounts when my camera is working again.

Ah, some new posts.

Nick, I've got two shafts here to look at. One is the early type with a removeable blind plug. The other is the later type with a staked-in brass plug. If I use them the brass one will be for the rear rotors.

I'm thinking cut a slot to accept a key, machine the opposite ends of two shafts for one to slip into the other, then add a set screw like you said. As long as it's true and can be balanced with four letter C rotors (because C was in the middle of the production weights from A through E) I don't see why it wouldn't work.

Actually with the NZ exchange rate, it costs less to buy a shaft from there. :)

dubulup, thank you.

that is so cool, when its running get vids posted!

Two words: Freakin' Sweet.

Jon

Impressive project! I'm definatly subscribing to this one. I have so many 12a's sitting around I was thinking about trying to make some kind of killer engine out of them, this is good inspiration....

Jeff is God

Wow. Words can't describe what a 4 rotor engine sounds like. I have only heard two in my life running. Sounds like a swarm of pissed off bubble bees! Turbo? Holy hell. With a 4 rotor? That would be like puting nitrous on a jet engine!

April fools!

Why stop at 4?

DD

http://i4.photobucket.com/albums/y12...ty/6_rotor.jpg

omg.....this is one amazing build

can't wait to keep reading on your progress jeff

Fuckin' Christ. :) This makes me want to just collect whatever parts I can from junkyards. All I see is a monster ready to be unleashed.

Hmmm
 

Hmm nice build.I do give u hands up for thinking outside the box.No flaming here but alot of people bitch and complain about some one putting a v8 in there and over weighing the front end.Did u stop and think how heavy this thing will be,thats alot of cast iron and Alum there,and u haven't even have the intake and exhaust and other components on.Pls Quote me wrong but a 20b 3 rotor weighs in at around 300kg or700lbs loaded what do u think this 1 will weigh?

Remember no flaming just asking and again nice build

Hmmm
 

Hmm nice build.I do give u hands up for thinking outside the box.No flaming here but alot of people bitch and complain about some one putting a v8 in there and over weighing the front end.Did u stop and think how heavy this thing will be,thats alot of cast iron and Alum there,and u haven't even have the intake and exhaust and other components on.Pls Quote me wrong but a 20b 3 rotor weighs in at around 300kg or700lbs loaded what do u think this 1 will weigh?

Remember no flaming just asking and again nice build

Ah ahaha! Yeah maybe. I guess we won't know until I fire it up and post a video. It's still a few months out.

82transam, you won't be disapointed.

Welcome, ducattiman. I'm not sure where you got your 20B information from, but it only weighs about 75-80 pounds more than a similarly equipped 13B. The 4 rotor 12A will weigh about 128 pounds more than a similar 12A. Just get stiffer springs and relocate the battery. Sure it's still more total weight than a 2 rotor, but the stock GSL-SE was front heavy too, with all that AC and power steering stuff. None of that on this car. The intake will be simple IDA carbs and the exhaust will be short headers.

OMG. That is my dream engine lol. I want to put one in a drift rx-7, and build a 4wd rally first gen for a 4 rotor lol.

Good luck man.... I might do this some day.

Hmmm taking my project ideas are you? LOL You're breaking my balls Jeff, you're breaking my balls LOL. I think I have a pretty good idea on how you will attain your firing order, just so long as you find one ;) Definitely keep us posted, you may do all the hard work for me LOL

Awesome, cant wait to watch this thread

What....Where, when, who...

Guys, that 6 rotor never ran. It's a mockup at Hurley.

FirebirdSlayer666, yeah I just have to be sure to post each step. Heh.

trochoid, I forgot to mention we haven't decided which radiator to use or how to mount it. We need to get the engine in there first. We'll start with the GSL-SE oil cooler and add a second one if necessary. Not sure which fan(s) to use. We may do a dual fan setup like on this rotary baja we got running last month or so. https://www.rx7club.com/forum/showthread.php?t=624151

i cant wait to see this finished. it looks badass already just sitting under the hood.

OMG, at first I thought this was an April fools. Now I don't know which is more shocking, the fact that the terms "4 rotor engine" and "cheap" were used in the same sentence without a negative, or that Jeff will soon have an FB in his possesion! This IS incredible!

Here's a link, maybe it'll help, though you've probably seen it before.

So for all us on the cheap would be followers, would 12A intermediate plates work the same as well?

Jeff: Oh my goodness.....

I cant believe my eyes!

First the ignitions and all the other crazy things,and now this?

WELL DONE!!!!

Karis

just spend the 9500$ for the shaft and irons from nz:) and ya will still be on the cheap:)

ProjectR13B, thankyou.

innertwist, it's not actually MY FB. It's a joint project. Mine is white and it's progressing in a different direction.

You know that link? That 4 rotor engine sounds like two 13Bs reving up together due to phasing. Blah. Mine will sound like a true 4 rotor with one fire every 90°.

karism, you should see the way I do the ignition on the 4 rotor. You'll get a kick out of it. :)

blwfly, with the favorable exchange rate, the shaft and modded intermediate plates etc come out to around $5000 USD. Not bad. If the two shafts together don't work out, we're getting the shaft from NZ.

awesome project jeff! CAn't wait to see that thing fired up!

I was about to say . . . .I have seen pictures of that build on Nopistons. :P

Great project, but we need more pictures

Glad to see you did your homework on the e-shaft and yes i think your key in idea will work and the setscrew but please GO TITANIUM lord knows if that brakes your SOL and it would suck to have to rip back open.

At least get a racing oil pump! i would feel safer for sure if you did.
If you need any help a machine notes or any tricks with metal let me know!
Heck i might donate some machine time to get this beast working for you.

Everytime I sign on to rx7club you are doing something else that is insane. I have to hand it to you, and give you all the props I have because, let's face it, not too many people have the balls to attempt the things you do in fear of failure, and yet you undertake it all even if all you learn in the end is that it won't work. So to that, I've got to say its admirable, and a waste of money. In saying that - anytime you modify a car its a waste of money to someone, so I say you spent the money wisely, lol.

-Dustin

lol it's only ever a waste of money if you SELL the car. :) Ever wonder why you see so many V8 RX-7s for sale all the time? If they were so great, why sell them? Of course they usually sell quickly but that's beside the point.

I believe once people see how easy and cheap it is to do a custom 3 or 4 rotor engine, the V8 conversion will lose some of its appeal. Just think about your own reaction every time you see another V8 RX-7 thread here or there on the forum. It's a real yawnfest. Then this thread appears and it erupts with positive comments. It's only been in existance for about 24 hours and we're already on page three!

V8s are cheap in this country, and if you're into that, that's cool, but you know not just anyone can pull off a 4 rotor project, making them rare and extremely awesome. Maybe that is the underlying motivation for sharing this info with the forum, to remove the romantic notion of the 4 rotor from its pedestal and place it in the hands of fellow 1st gen owners. Or something like that.

How many of us can spend $5000 on parts from NZ? How about another $5000 on misc things like carbs/fuel injection, exhaust, suspension, brakes, tires, tranny+driveshaft+rearend etc. How many have already spent $10,000? Does it sound more appealing if I mention the car will have the performance of a typical new $50,000 sports car? What if you can cut corners during the build? What if you don't change parts until they become inadequate/break like tranny, rearend etc? What if the bare mininum for just the engine and a couple other parts like some Weber IDAs, some basic exhaust components and an upgraded fuel cell with high volume fuel pump only comes out to $7000? Sound a lot more appealing then?

By the way when the mockup was in the bay, the front end did not sag at all. That's on stock springs. I even leaned on the bumper and it didn't go down much. The internal guts of the engine don't weigh too much at around 9 pounds per rotor and whatever it is for the shaft, plus it's located further rearward than I was on the front bumper. I don't anticipate any front end sagging problems with this build. We'll be going with RB or Eibach springs though as a matter or course.

I bet they're still 6 months out, as they have been for the last year or so. At least they redid their web page since then.

Anyone know how soon autotech will start selling shafts?

Said in the words of Butthead "Beavis, this is the thing that could save all man kind, uhh, huhhu uh, huhh huhhhha".
Sweet!

what are planing on doing for the ports becouse from what I see you will starve the two middle rotors of air with such a small ports.

you've got to post pictures of all the maching that has to be done for the stationary gears to fit the intermediate plates, there is so much engineering in that alone. as a matter of fact, i'd love to see any and all of the maching work that goes into this build. things like this amaze the hell outta me! good job man!

i beleave he is going to be going PP... so there should be no starving of the rotors :)

What kind of baseline would you anticipate for this? I love the idea, but I look at things in a price to power ratio. I am sorry, but if I were to invest the money in something like this, I would build a 4 rotor out of two 13B-REW's I wonder if you could run a sequential QUAD turbo engine..... ::drools:: oooh man I think I am going to blow a load because of this thread...
Not trying to take away anything from what you are doing, it is truely awesome..

Peripheral ports.

I'd estimate at least 400HP but it depends on port size, intake and exhaust. Remember this is NA.

Do you think there is a way to optimize the intake flow on the center rotors to possibly build for a non-PP set up? I would want something more streetable than a PP, I can live without four rotors though. But I still would like to see this build completed, oh and sorry about the quad turbo comment, I had the Veyron on the brain earlier in the day :)