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I had some issues with the length of a 4 rotor and originally thought I could do as much as 400-425 whp with a streetable 3 rotor. Only got to 397, but am happy with that. For me its the instant response and consistent throttle response of NA that's attractive. Plus, I have never had any issues with reliability. And, I have had the 3 rotor since 2009. A lightly tuned NA 4 rotor should easily do 425-450 whp or more.
I'm not trying to start a fight with you, for some reason this whole sticking with oem and REW stuff for a 4 rotor that isn't going to take advantage of their ports (na), and then settle on less than best in class parts for such a large undertaking is just plain...weird, and wrong. Now, if it's just because the dude wants to, have at it, I'm taking issue with the justification being thrown around so here goes:
Originally Posted by arghx
the reason you go with the OEM blocks is because the parts are actually new.
You can get everything that you can actually use new for less after you factor in all of the machining required to stick with REW blocks. Rear engine mounts, only two bearings, no large tension holes.
All this stuff about lightweight this and clearancing that, what's the point if it won't breathe over 7k?
My point about lightweight/clearanced NA rotors has less to do with the fact that they're machined to be lighter and more to the point of balancing, and I believe you can still purchase new, optimal core shift NA rotors from Racing Beat. I'm also not quite certain where you're getting the number 7k for some sort of breathing wall unless you're talking about a pre 91 engine or a 20b with silencers in its exhaust still. I've done many back to backs on my dyno facilities and even stock ports breathe quite well, its just that factory manifolding is way less than ideal.
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?
Most of these statements are just ill informed and kind of not true in this day and age other than torque. Modern ITBs (TWM comes to mind) are easy to maintain and if they remind you of a carb I don't know what carbs you're speaking of. E-throttle can be had via an S54 actuator, I've seen many very well thought out solutions. Active and aftermarket emissions controls could easily be adapted and MAP compensation based Alpha-N using a vacuum manifold for signal conditioning, fuel economy suffers a bit, though I haven't had issues getting it rotary reasonable.
You can use some aftermarket seals but the stock ones work fine.
Why is what amounts to 1/40 of the budget brought up over and over?
Sure the 9.7:1 rotors would be a small benefit if you want to go that route.
In an NA application it's really not that small of a benefit when you don't have a boost screw to turn up in my opinion.
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.
There's peripheral ported street car and then peripheral ported race car. I've driven periph street cars that drive better than stockish FDs (light flywheel, heavy clutch). I think that YOU may be assuming that once you go peripheral you're now being forced to live with an IMSA drivetrain or something.
Only Johnny can decide what the goals are.
True dat. Also, Johnny, I'm more than happy to take dimensions or close ups if you're curious about how Logan has built the engine I'm working with to make informed decisions. It'll be a sweet project.
Johnny needs to figure out the target torque curve. WIthout knowing that you can't define the intake port closing timing (i.e 4 vs 6 ports, and porting on top of that), the runner length, or whether you want to use pulsation effects in the manifold (ie a plenum).
This is from Mazda's own research from 1982. It's really no different than a piston engine with fixed cam timing. Later closing - more high rpm power, worse low end torque. Bigger isn't always better, shorter runners aren't always better either.
There is no variable intake manifold runner length option here unless you can somehow shoehorn in an S5 VDI system, and I doubt that would be optimized. The 89+ and Renesis VDI were not designed for 4 rotors (duh). You've got to pick an RPM point of peak VE and go with it. Of course it can breathe over 7k with later intake port timing and short ITB's. There's no debate there. But you're going to take a hit in low end torque. Mazda went through this 40 years ago when they designed the early 6 port + plenum system. You've got to give something up.
ITB's are not a slam dunk. ITB's and short runners hurt low end torque. They add complexities to tuning and streetability. Just because it's been done before doesn't mean it needs to be done again. If you can get a six port system + plenum going like on a 84-88 13B you'd get a broader torque curve, and in that case you need to make FC irons work.
Now I wasn't aware that someone had successfully used the BMW actuators for Rotary ITB's. Has anyone actually done that or was it just a retrofit on a different piston engine? Last I heard Electromotive was under consideration for the ECU in this case, and as far as I know electronic throttle isn't even an option for their most expensive unit. If somebody has already figured out ITB electronic throttle on a rotary with 4 ITB's, it would be the first I had heard.
So what are the goals?
Target idle speed? Acceptable fluctuation under accessory load? Acceptable warm up behavior? Lowest acceptable starting temperature?
Target peak torque rpm? Target peak power band?
Emissions and fuel economy - ok with open venting the charcoal canister and PCV ? running cat or no cat? Obviously premix is required here and secondary air (air pump) is off the table. Tip in fuel control - do you care how rich it goes on tip and tip out (has implications for acceleration enrichment tuning) ? Do you want to have wideband feedback control (full time closed loop) ?
If you ask me, if you want the broadest torque curve, you've got two options: plenum with single throttlebody and 4 port, or plenum with single throttlebody and 6 port.
Not to derail the conversation but... what chassis and race org/class is this car being built for? I'm hoping to see it on track
It's an older John Finger chassis with an FD body. It had a 2 rotor in it competing in NASA and now it'll have a 4 rotor competing in either Super Production or GT-X with SCCA.
Here it was at Buttonwillow shaking down the suspension with the old powerplant
Any more questions on it means I should probably do a build thread but I'm pretty bad about stuff like that. Back to Johnny's 4 rotor build.
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I had some issues with the length of a 4 rotor and originally thought I could do as much as 400-425 whp with a streetable 3 rotor. Only got to 397, but am happy with that. For me its the instant response and consistent throttle response of NA that's attractive. Plus, I have never had any issues with reliability. And, I have had the 3 rotor since 2009. A lightly tuned NA 4 rotor should easily do 425-450 whp or more.
I thought you spun bearings at DGRR 7-8 years ago and I believe the car has been down for other issues as well? Not stirring the pot but dont sugar coat how extensive and finicky the setup will be unless he throws a fortune at it. Even then, I would expect a lot of hiccups for the first couple of years.
You know my opinion already but Ill post here. Start with the two REW blocks, spend the little bit extra for the S5NA rotors to have them lightened and scalloped. You will need minimal new internal seals. Dont skimp on electrical and alternator. Make sure oil coolers are overkill, spend a lot of money and time on tuning. Keep it simple where you can with trans, streetable clutch, rear diff. Work out the few kinks when you get it back that you are more then capable of handling then enjoy. You are sending it to the right place and I think it will be a really enjoyable car for your intentions.
DJ... As I said above regarding eshaft wobble, when Barninger gave me the car to drive to DGRR in 2011, he didn't have it properly balanced and the bearing spun on the third rotor. That is the only problem I have ever had with the motor since 2009, although I only have about 10,000 miles on the motor. That includes Ihor running some pretty extreme dyno runs. Other than Barninger's screw-up, the motor has been bullet-proof.
This is just something I keep thinking about and probably won't work at all or not the way I am thinking about it. Myself and others are using ITB's and one ITB per housing with runners that split off or "Y" to service both the primary and secondary intake ports. There are a lot of issues with the lengths of the runners to each port and diameter of the runners and where they split off. I and others are using something like 50mm ITB's.
I wonder if it wouldn't make sense to run separate ITB's for the primary and secondary ports. So, with a 4 rotor, you would have 8 ITB's. (Probably motorcycle ITB's, where you could size them small enough.) One larger and one smaller per rotor. Different length runners and different diameter runners to optimize flow. The primaries need runners about 14-15 inches long, IIRC. The secondaries' runners should be shorter and as straight a shot in as possible. Using throttle-by-wire controls and a really good ECU, like a MOTEC, this setup would make more power -- ceterus paribus -- and it might provide a lot smoother transition.
Damn talk about memories. That's the Autotech 4 rotor from years back. That car gave me the inspiration to move my engine back when I started my own 20b Fd swap back in 2007 (can't believe it's been 13yrs). Anyways, that lower intake was fabbed from scratch and very short so they could get the engine to clear the firewall without modifying it. I think it was a 12A block.
Hey, Trey. How about some pictures or video of your 20b?
Now Gordon based on discussions we had years ago, you know I cant show pics of my engines very unique PP mods (especially when I'm trying to get a Patent on the design by the end of the year. After that, I'll have no problems showing anything. Just gotta protect all my hard work over the years.
t-von... I knew you had some trick stuff, Trey, but how about a video of you driving it? Just love to hear it.
Per our PM conversation a while back, engine is down due to coolant leaks from the PP's. Gotta reseal them once I put my new steel building and lift up this summer as I don't currently have a way to pull the engine right now since I no longer have the shop I built my car in. Here's some old audio.
Funny we Trey's had the exact same problem when I 1st fired mine up too. The oil filter pedestal I made was leaking badly. Sadly that wasn't the only leak. Intake and coolant leaks have been my biggest problems. That's why I cant wait to pull everything down and re-engineer the whole setup now that I actually know how to fab and what the hell I'm doing. When I look at my current setup, I think to myself "what the hell was I thinking". Lol!!!
12-05-19, 12:42 PM
