Johnny Kommavongsa

iTrader: (13)

There are probably a few other 4 rotor FDs in the states but Rob’s and David’s are probably the most discussed and recently another turbo 4 rotor build emerged at SEMA.

Rob is in the process of building an AWD Turbo 4 rotor.


David has a track oriented turbo 4 rotor but I haven’t see a street friendly non tracked NA 4 rotor FD.


When I say street friendly, here is what I’m thinking

• Idles below 1k rpms
• OEM clutch pedal feel
• Power steering
• Heat and AC
• Leverage OEMs rubber engine mounts

What are your thoughts on a street friendly NA 4 rotor FD?

Engine setup would be

• REW rotors with OEM Apex seals sourced from two new REW engines. I know most people would use S5 NA rotors.
• REW housings, irons and counter weights
• Rotating assembly balanced
• Street-port side port
• Custom oil feed to bearings
• Ok with 7k RPM limit so currently thinking wet sump. Don’t want to have to deal with external pump and oil reservoir. Chip Motorsport has a nice new dry sump setup but the product is too new to try.

Fuel

• Pump gas
• Primary injectors only
• Custom rail

Intake

• Slide throttle or plenum

DaleClark

iTrader: (55)

Any reason not to use S5 NA rotors? Would be nice to have the higher compression.

Would also be cool (but a CRAZY amount of work) to somehow put 2 S5 intake manifolds together to have the 6-port and VDI.

Also the 89-91 NA's had an 8000 RPM redline. I don't see any reason not to use the higher redline. Being NA the engine will be much less stressed than a turbo version.

Dale

Johnny Kommavongsa

iTrader: (13)

I think it would be more cost effective to use parts from two new REW engines being that you can one for under 5k shipped. Unused parts from the engines could be sold. You could reuse the OEM apex seals and wouldn’t have to clearance the side seals.

And yea using the two s5 intake manifolds would be cool but complex.

newtgomez

Depending on your fab skills, I would say it's possible to have a street friendly 4 rotor, but from what I understand, one part is the complexity of shaping an OEM side port based intake manifold. Of course, if you're spending the money, why not go big or go home? Another concern of course is packaging as the 4 rotor extends out really far forward. I'd be extremely interested in seeing someone achieve such a thing, personally.

DaleClark

iTrader: (55)

In the scheme of things this isn't a project you can save money on, it's going to be a LOT of money. Just the e-shaft would be some serious money. Also custom fabbed intake manifold, an ECU that can run the thing, you're probably looking at $30k easy. Not to mention getting it all tuned so it not only runs well and safely but is streetable with good manners all through the power band.

Really it's like doing a turbo 4-rotor but just saving some of the turbo costs associated. Price would also go up if you wanted a more exotic intake manifold - variable length runners or ITB's for example.

Dale

Copeland

iTrader: (42)

The primary concern is cost vs benefit. If you're going to spend the money to turn-key a 4 rotor setup, you're not saving much to go N/A or streetport. It's a negligible cost difference (in the grand scheme of things) to go turbo p-port with a lot of power specific benefits (roughly 3-400 additional RWHP). Even if you truly want just a street motor, you'd be better off with a turbo in either case.

The secondary concern is practicality. It's essentially a fully custom setup to run a 4 rotor; this means a lot but I'm going to focus on one particular hangup for the 4 rotor design: The side port 4 rotor sucks. It will make almost no power for what you're investing (see cost vs benefit concern).

The side port 4 rotor uses much smaller primary ports for both intake ports. You don't have the benefit of the much larger secondary port on the engine such as every other useful rotary engine. If you look at the 3 rotor, it has a "fat iron" because it has the much larger intake port designed into that iron to balance the center rotor to match the end plate intake ports. The "fat iron" of the 3 rotor also holds the stationary bearing, which is less of an issue for this discussion. The similarly designed short crank 3 rotor, also has the same, less than desirable, side port design; which is why almost all of them are configured for turbo p-port intake setups.

If money was no object, you'd probably still not want a side port N/A 4 rotor engine design due to the lackluster performance. So that brings you to the p-port N/A 4 rotor, which is where almost all of your streetability is lost to begin with, the p-port. So then you're left with the turbo side port 4 rotor, which is still not perfect but probably the most streetable setup you could go with but expect roughly 3 rotor power numbers for a much higher price tag.

If you're going to build a 4 rotor, you build it with a turbo and a p-port configuration because the cost is absurd to build one at all; You're going to want that extra power if you're investing a small fortune into it. Either way, you're probably not going to be daily driving any of these configurations, so build a turbo p-port monster and enjoy the sweet sound of a proper 4 rotor.

gmonsen

Copeland... It kind of matters what he wants as en end result. I have an NA 20b that makes close to 400 whp. A 4 rotor NA would easily make 450-500 whp. Turbos would make a lot more power, but that might no be his goal. It certainly wasn't mine.

Johnny Kommavongsa

iTrader: (13)

Thanks for the feedback.

Not following this comment but I'm assuming you meant to say, "you're not saving much to go N/A or Turbo"You have a valid point on, if you are going to do this, might as well go p port and turbo.

I do think a p port would be cool and I think they sound awesome. It’s just not something I’m going to want driving around town. Same thing with boost, I love a boosted car but for this setup, I think a NA would be best as its less complex. Less heat, no wastegates, no additional oil and coolant lines, no intercooler, etc…

dguy

iTrader: (8)

I think you're going to be doing so much custom fabbing that sticking to REW parts just because you can get 2 kegs new will net you next to nothing. With regards to your redline it depends completely on how many bearings you're going to shove in there for support/to prevent shaft roping. I'm currently fitting one of Logan's peripheral port 4 rotors into a tube chassis with an FD body.

BLUE TII

iTrader: (9)

Here is my idea which makes side port and preserving some of the FD chassis balance easier.

Use two crate 13B-REWs side by side in the engine bay. I measured and they fit but you have to dry sump them and turn them spark plug side down.
Have an inboard boat engine shop make you a twin engine to transmission adapter (its what they do).

You can use a standard short exhaust manifold to a single turbo on each engine (EFR 9180 iwg would be nice and simple) and a custom vertical short runner intake to plenum (modified 4cyl piece) on each engine with dual lever/shaft linked TBs.

The downpipes would be a headache, so probably easiest to reverse mount the turbos and bring the DPs forward and into cats/mufflers down where the radiator would normally be. A sheet stainless duct over the top of the exhaust guides air from the front bumper over the exhaust, but dumps under the car in front of the engine (like radiator waste heat) and/or through a Vmount style forward hood vent.
muffler exit either side on front bumper just ahead of wheel well.

Bonus with reversed turbos you can use the Feed style cowl vent hood to feed pressurized fresh air to turbos airbox against the firewall.

Liquid to air ICs in the plenums (so might as well use Cobalt SS plenums with their superior Laminova IC cores).

Rear mount radiator for engine and IC where gas tank and muffler was. Ducted inlets from under the car and rear of rear wheel wells and exit through a mesh screen moulded into the rear bumper cover or a diffuser set higher in a trimmed up rear bumper.

Gas tank moved into race car fuel cell where storage bins were (you make expanding foam in trashbag mould of the space and they make you the fuel cell). Cover that in sealed sheet metal above with nothing in rear seatbelt holes below and its safe and legal for racing too.

Steering rack must be rotated so input shaft is forward and steering shaft must be extended to run over the engine and then use a steering quickener style coupling to bring the shaft and rack together in front of the engine.

It would look **** with the top mount turbos/plenums and could use standard engines, 2 rotor ecus, base maps and turbo kits (So, all known quantities), the 600lbs of engine would be where the original 420lbs of engine were instead of 300 in stock location and 300 in front of that like an inline 4 rotor.

You want AC too? Ugh, put that with the rear radiator and use an electric AC pump *somewhere*.

You know what?
Might be easier and cheaper to buy the white Scoot 12A based 4 rotor car since streetable emissions passing 4 rotor was their goal with that one. Sure, it might not make much power, but it is a 4 rotor and the shorter 12A based 4 rotor is a nod to preserving chassis balance.

rdahm

iTrader: (6)

I wanted to comment that Copeland is a little off on the side port 4 rotor being a waste or low power etc. I’m a massive fan of street ports for their low idle etc. but holy crap does this engine pull without the turbo boosting. And i haven’t even attempted to clean up the tune much.

But i think op messaged me privately. The issue I see is that you have to do the bearing mod if you pull the parts from two REWs. And the center iron definitely should be a tall port for the same concerns Copeland had. Mines billet on the awd engine. So poet matching is pretty solid.

Going to buikd my second motor into a semi p na motor. Or turbo it down the line. Idk. But I feel like one of the unspoken benefits as billet blocks come alive is the weight savings. It makes a 4 rotor less of a burden in your street fd. The 3 billet aluminum irons knocked 100 or so pounds out of my engine. I don’t remember exactly. But it was substantial and my 4 rotor weighs the same as my 3.

Just a late night brain dump

H_M

iTrader: (7)

I think Logan from Defined Autoworks offers several different pre-built 4 rotor engines. Last time I checked, he has a couple of "mild" more street oriented engines on his website.

Copeland

iTrader: (42)

Your car is a very unique example of a 3 rotor N/A build; I know it took you years to iron it out properly.

Isn't yours setup a p-port motor? I'd argue that's where a lot of the complexity lies in street manners, it's very tough to make a p-port setup streetable. If not, it's still impressive but not a good comparison since you have a fat iron 3 rotor which the 4 rotor will not benefit from due to the skinny intermediate plates.

I just don't think a significant investment on a 4 rotor would be worth 450-500rwhp when a 13B turbo can make that on pump gas. Yes, you can probably make the 4 rotor more reliable, but I can also rebuild that 13B 10+ times for less than a 4 rotor cost.

Sorry, I meant to say there is a negligible difference in in cost for N/A (N/A being non-turbo, naturally aspirated) side-port, N/A p-port, side-port turbo, or p-port turbo; when it comes to building a 4 rotor at least.

I understand wanting less complexity but I'm just being realistic and pointing out the cost to power is hard to justify for most people when the 13B turbo makes similar power with decent street manners. I'd even argue that the 13B turbo has less complexity than a 4 rotor, of any kind, brings.

Don't get me wrong, I'd still love to see you build one.

I think your car is an extreme example and probably not a good comparison to what most of us would build. The billet plates probably help but they still only have so much real estate for airflow when they're still using the skinny intermediate plates.

I'm sure the side-port 4 rotor still pulls nicely but for comparisons sake, your car is likely to have different transmission and axle gearing than stock and the butt dyno is a tough comparison to use.

Edit:

I'm only saying the side-port 4 rotor is a waste, when compared to a similar p-port 4 rotor. It is essentially only a couple percentage points cost difference between the two and the power gains are significant. The power gains are due to the skinny intermediate plates restricting intake side-port size.

Johnny Kommavongsa

iTrader: (13)

Makes sense thxs for the info Copeland. I remember seeing your car at DGRR and that thing looked rowdy.

And thxs to Rob and others for chiming in.

Still interested in hearing others feedback.

Any feedback on slide throttle vs ITB or plenum?

Cable vs drive by wire throttle?

Mechanical vs electric water pump?

Gilgamesh

A proper side port 4 rotor could be built with billet plates.

Johnny Kommavongsa

iTrader: (13)

What are your thoughts on using 12A center plates?

gmonsen

Very cool build you're doing. You make a good point regarding redline. I think you need to do whatever can be done to support the eshaft. You get wobble. You also need to be sure you open the oiling passages and possibly add some additional oiling. Dry sumping helps as well. Basically the 20b and 26b will only run reliably to maybe 8500 rpm before having issues.

arghx

iTrader: (3)

Johnny and I have spoken about this build and I've been recommending him to make it as mild/OEM as he can. Don't even play the power game is what I've argued.

My recommendation is basically side port 4 rotor with the two REW blocks if he can make it fit. Just use the stock rotors and stock seals. If wet sump won't fit then dry sump, but if you can make wet sump work then do it. Johnny mentioned using Xcessive LIM's as a foundation for a manifold or fabricate. Either way, use a single throttlebody and common plenum with common vacuum signal.

-- Not many big builds have rubber mounts and idle like stock.
-- Absolutely no ITB's. No Plenum - no vacuum signal, Alpha-N tuning only. Yuck!
-- electronic throttle preferable but if not, install an idle speed control valve at least. I know there are romantic notions about throttle cables on this forum but they've been out of production since 2008.
-- [gasp] use a simple exhaust manfiold and even consider a muffler and a high flow cat...
-- simple cooling system
--no expensive drivetrain and transmission hassles
--PCV and evaporative purge solenoids! Yes you heard me! no catch can to check, no vapors smell on a hot day! Just like a normal car. Bet you've never heard someone argue for those before. Keep the stock charcoal canister and purge solenoid and PWM control it like a normal car.

No turbos = no knock, no secondary injectors or huge fuel systems needed either. Stock red line saves cost and complexity and risk. You just need a trigger wheel on the crank and could probably get away with batch firing it. Cooling system is nowhere near as difficult as with boost, no need to fit the turbos and intercooler stuff.

Big power 4 rotor will just spin tires and be a one trick pony (which is why Dom's car is going the AWD route, and why try to copy someone else?) 6 port irons and VDI aren't worth the trouble, if you could even fit them. Then you're stuck with two throttlebodies and Alpha-N or other complicated tuning and idle control. WIth this style setup you get better low end torque vs ports with very late closing and huge overlap.

It's not going to dyno a whole lot but it will be different and it will be torquey and it can be more comfortable and quiet.

dguy

iTrader: (8)

I don't understand the push to save what amounts to a few hundred dollars on using stock seals from new REW kegs on what will amount to be at least a $40000 project after labor (I'd say north of 50 to be honest). This doesn't make sense nor does pushing for REW irons, housings, and rotors for that matter. The amount of machining required to fit stationary gears and bearings in the irons negates all savings and you also have the option of just running things like PAC performance aluminum pieces and for the cost of this project overall just run lightened NA rotors.

Also Alpha-N with MAP compensation using a vacuum manifold run to each ITB is completely streetable given some finesse during tuning, even on a peripheral port.

With regards to the other bits, I think you're oversimplifying the ease of staying 'oem-ish', though I do agree with keeping modern emissions controls, real mounting components, and a reasonable exhaust.

All of these things are totally doable, just don't kid yourself that you're saving anything by sticking with a couple OEM blocks.

BTW, these ******* are bigger than they seem, and even if you've seen one in person you wont appreciate it until you try to shove it in a chassis:






P.S. I can't stress this enough: I'm not saying you can't do it, nor am I saying don't try.

arghx

iTrader: (3)

...

arghx

iTrader: (3)

the reason you go with the OEM blocks is because the parts are actually new. All this stuff about lightweight this and clearancing that, what's the point if it won't breathe over 7k? Sure you could if you do the whole ITB/velocity stack with big ports for high rpm breathing. The 6 port systems you could probably get working if you really want to, but now you've got to deal with n/a irons and controlling the ports etc. VDI is out of the question because you can't make that UIM work.

With ITB's and big ports your low end torque takes a hit, you've got to balance 4 throttles by turning screws, and you've got half the carburetor experience at that point. You can't run electronic throttle, you can't run an idle valve, you'll probably have to open vent the evap canister and PCV system (catch can), your MAP signal is questionable. Yes you can run Alpha-N, but why bother?

You can use some aftermarket seals but the stock ones work fine. Sure the 9.7:1 rotors would be a small benefit if you want to go that route.

I think we all have a different definition of street cars and streetability. I'm judging by the standards of a stock FD, and a stock FD is basically awful by modern car standards due to its rough and unstable idle, poor HVAC, etc etc. Everyone else is judging by the standards of a typical peripheral ported race car. Only Johnny can decide what the goals are.

Copeland

iTrader: (42)

I'd love to see you build any kind of 4 rotor setup so let's start off with some suggested (or at minimum, required to look at sections). I'll try to focus on the non-engine specific things to consider, I'll touch on the oil pump though.
.

• Transmission upgrade: The factory transmission can break with minor upgrades to a 13B and a 4 rotor is a lot more than a minor upgrade. You'll no longer be able to keep one behind this motor for longer than a year at a time otherwise, reduce life based on how often you hit the peak torque of the motor. Don't forget about the associated clutch and hydraulic upgrades required to change to another transmission. I highly advise against an upgraded gearset/mainshaft inside of the factory transmission case; the factory case is the weak link, not necessarily just the gears.
• Differential upgrade: You'll at minimum want to build and brace the rear differential substantially. The factory diff case/internals can break fairly easily with 13B upgrades. This presents an issue for NVH if you use the factory diff, as the braces reduce isolation substantially due to the need for strength. You may want to consider an 8.8 diff upgrade. You may also want to consider axle upgrades.
• Fuel tank size: You'll like get between 100-150 miles to the entire factory tank with a 4 rotor, driving normally; probably around 75-125 miles if you want some reserve space. You'll want to start planning out upsizing the tank if you plan to drive it a lot. They don't sip fuel.
• Brake upgrade: I'd suggest a brake upgrade but you may be able to get by with factory brakes with some upgrades. I know they're decent factory but you're approaching territory where they'll need some extra capacity.
• Cooling upgrades: The 4 rotor presents an absolutely massive heat generation issue. You'll have heat, but it will need very large oil coolers and an equally monstrous oversized radiator and fans. These eat up real estate in the tight engine bay too, so you may have to get careful if you still want to run a traditional A/C system on this setup. You want to overbuild the cooling system otherwise you'll never be able to enjoy the car if it has overheating issues.
• Alternator upgrade: The larger electrical load on the car will need to be addressed with an upgraded alternator of some sort. The factory upgrades are pretty unreliable from what I've seen so you may want to consider something that is not the factory alternator case; perhaps something that is OEM from another manufacturer but still puts out more amps than the FD's factory 100amp setup.
• Water pump upgrade: You'll be forced to go aftermarket on the waterpump as the factory one will no longer be adequate. I'd suggest an electrical water pump, but it will be tight with A/C and P/S still on the car!
• Oiling system dilemma: The factory oil pump is not really big enough for twice the motor. You can use an external oil pump but you'll be short on space for such a large device; this also requires some fancy sump work or a dry sump setup. You'll want to determine how you want to do this before jumping too far into the engine build.
• Serpentine struggles: Be sure to plan how you want to fit the alternator, P/S, A/C, possibly an external oil pump, and the electrical water pump fittings/hoses in with the radiator/radiator fans. It will be tight but it can be done.
• ECU/wiring: This will depend on your tuner/expectations of capabilities.
• Fuel system: Single rail would simplify this a lot with modern injectors.
• Ignition system: They eat a lot of space for individual coils, so batch may help here but reduce overall capacity.
• CAS/timing setup: Will it be a FD style or a FC/Cosmo style?
• Intake manifold: It will be custom.
• Exhaust manifold: It will be custom.
• Oil pan: It will be custom, depending on your mounting location/subframe use.
• Engine mounts: Probably custom if you want rubber mounts.
• Subframe: Probably want custom to relocate engine further back.
  • If you should move the engine back or not: Firewall cutting, driveshaft length, transmission mounts/shifter location, dash impact of firewall modification, etc.
• Power steering rack fitment with oil pan/engine location
  

.
It will be a lot of work but it can be done. I just suggest you look at your budget before digging too far into it, it will add up quickly. This was why I brought up cost vs benefit, it's going to be hitting on some unfavorable ratios by the end of it.

DaleClark

iTrader: (55)

If you're doing NA 4-rotor and staying at 350-400 I don't see needing to do a trans/diff upgrade. Turbo 4-rotor, yes.

Room is going to be a big issue for sure. 4-rotor is just damn long. I think Scoot in Japan did a 4-rotor with 12a housings/rotors, that would knock 40mm off the length of the motor.

Dale

Johnny Kommavongsa

iTrader: (13)

Thanks for the consideration items Copeland.

I don’t think I will be making more than 450 with the current setup that I’m thinking so I’m hoping the trans and diff will be ok. I think a lot of the issues with them breaking is how hard one is on them.

Didn’t think about the fuel tank but you have a good point. I don’t foresee myself putting a whole lot of miles on the car. The furthest drive we ever do at once is to DGRR which is about 200 miles. I probably average 5k miles a year on the FD.

I could see myself doing a brake upgrade in the future.

Alternator, I need to figure out what Rob and David are doing.

Check out how the alternator is mounted on the scoot car and how Logan did the Alternator and PS on his 3 rotor build. Would be neat to try and do something similar.





The scoot car started off as a 12a but now has 13b parts

The Rotary Dream Is Well & Truly Alive At Scoot - Speedhunters

gmonsen

Here's a few shots of my alternator on the 3 rotor. I wanted to retain the airconditioning.