4rotor buildup concerns....
 

Ok... as many of you should know, I am making a 4-rotor First Gen RX7, to go n/a, and carbed, to break the land speed record for a rotary.


However... other than the obvious aerodynamics and hp concerns, comes something that was a hindsight of mine until I began planning out exactly what parts to start buying....



What distributor am I gonna use? Keep in mind, this is for a 23A, essentially two 12A's sammiched together. How will I hook up the second one, if at all?



How will I get enough fuel delivered at 200+mph? I've heard horror stories from Bonneville teams, Nascar teams, F1 teams, etc., about how fuel starvation at such high top end speeds is such a crisis.

I was planning on running two 255lph fuel pumps, to give the engine enough juice. Also keep in mind, that while I will be bumped into a different class, I will more than likely be spraying nitrous.... LOTS of it. a 200 shot on each carb (there's 2 carbs) to spray at the same time. The fuel has to match it.




So, fuel and ignition stuff is the worry of the week this weekend, so feel free to post away!

Well, that's a bit of a problem you've got there...
I have no idea about rules or anything, but wouldn't it have been easier to go EMS? With twin carb you'll need to get very proper synchronisation... Well, that's the smallest problem, the ignition is more complicated.
You could look into an old RX2 front cover, as this uses twin-dizzy's. Maybe they can be replaced by two 12A ones. One for each half of the engine. I don't really know, it's just an idea. Maybe it's also possible to convert a 12A distributor for four rotor use, much like Racing Beat does for 20B aplications. Again: not sure, just an idea.
Since the engine is basicly a double 12A, the 1st and 3rd rotor, and the 2nd and 4th will probable do the same thing at the same moment, right?
Couldn't one distributor trigger two DF units?
Still, I believe programmable EMS (ignition only, does that still excist?) would be easiest...
Not sure if I helped you a lot, but well, at least I tried :confused:

Distributor? Whats that? Direct fire :).

~T.J.

I think that rotary emotions might be on to something. If your firing order really is two sync'ed 12as then using a single 12a dizzy to trigger some sort of massive dual sparkage is a path to investigate...
What will your firing order be?
What RPMs are you looking at?

On the carb issue, what kind of carbs? A row of Webbers like the old Bonneville flatheads? That would scream! Or dual Holley double-pumpers like some monstrous Pro-Street beast? You're going to need a gallons-per-second fuel supply alright.

for the money I still suggest a 3-rotor (parts already developed) along with suspension tweaks to effectively put that power on the pavement, even in corners, and a budget left over to make sure all the niggling little stuff (switches, door and hatch rubber, interior trim, etc) is worthy of the car.

I'm still wondering why you'd spend tens of thousands on a custom engine, yet not spend $500 on a rust free shell...

I wonder why carbs??? Look at 3rotor.com, he has a four rotor turbo under construction...

I get the impression that Chef seeks to drive the path less traveled. A nitro-huffing carb'd 4-rotor stuffed into a rust-repaired FB means pretty much bazing his own path.

I would start with a clean shell, too, and spend no more than $100 plus gas to go get it. But the one cool thing about a rusty shell is that you don't feel bad about modifying the heck out of it, like tube-framing, roof chopping, channeling, all the things that one might have to do in search of high-speed areodynamic stabilty.
This assumes you also don't feel bad about 10,000 hours of body work.

The free shell has now become the parts car for my 79 widebody.... the "shell" has a full interior in great condition, and other misc. odds and ends that I will need to swap over to the widebody to a)make it road worthy, and b)make it ~complete. The free shell, after seeing it, is nothing more than a parts car at this point.


I have seen some pristine shells (even one with the 2" chop that I want!), and for fairly cheap. I wasn't prepared to BUY a shell, per se, but after seeing the free one, I really have no choice.


And as far as the 20B concerns... yeah, it's a tried and true engine, but with the right hookups, and the right buildup, it [the four rotor] is gonna be indestructible, in theory.

in theory, bumblebees can't fly ;)

Chef, what will you call this motor: a 12AA or a 24A?

http://www.grannysspeedshop.com they built a 4 rotor... I talked to the guy who built it on the phone he is a really good guy... ther are a few companys makeing 4 rotor e-shafts now... I think it would be a good idea to use a twin distributer front cover... as far as carbs go get a large tpi setup... you will make more power with a fuel injection setup... or you can run twin throttle bodys...with some free flowing 4 bbl intakes... and run a aftermarket fuel computer...

What class you going to be in at Bonneville? I know its a ways away, but I have list of all the records for all the classes and I just wanted to see what you will be trying to break.

What size fuel lines are you going to be using? carbs don't use nearly as much pressure as with EFI. You will have to make sure you have a good volume of fuel supplied by the pump. Next, the plumbing has to be able to carry that fuel to the carb. Then the carb has to be able to deliver it without flooding. And where do you plan to tap the fuel system for your nitrous injection?

JEC, it will be called a 23A. a 12A is 1.15L. 1.15x2 = 2.3L, hence, 23A.

i_piss_on_hondas, granny's has been called a couple times, but with no conclusive answers yet. they want more questions when it's actually underway, rather than on paper. and WHO is making 4 rotor e-shafts, and how much? links? phone #'s?


will answer more questions in the morning.... very seepy.

I'd like to know who's making 4-rotor e-shafts too. And the price...

WEll if I tell yeah your going to have to call it the " I PISS ON HONDAS" ;) I comp it out of nz I know there makeing them... I think there is also one out of nz... I dont have the links any more to either of those too... Hurley MIGHT I am not shure if they do or not... I cant get there web site to work but there ARE companys out there that are makeing there own 4 rotor e-shafts...

shit I ment also a comp out of austrailia

I may have an available option for the igniton and distributor stuff....



http://store.summitracing.com/global.../msd-62151.jpg
MSD High Output Distributorless Ignition System

won't you need a digital dis-8, for 2 plugs per rotor x 4 rotors?

....and the fuel delivery....


http://store.summitracing.com/global.../aei-11202.jpg
Aeromotive A2000 Drag Racing Fuel Pump 350gph

wouldn't 2 digital dis-4's work the same?

I have an old "RX-7 Magazine" from Japan that has an article on the 4 rotor motor and I know that it discussed the firing order and problems encountered like the e-shaft snapping and stuff. I'll bring it into work and scan and translated but that won't be until tommorow.

To me, it seems like you would have too. Since the trailing doesnt fire opposite the leading. I don't think the dis 8 would work. But, what do i know?

A buddy of mine already has made a 4 rotor built from 12A parts. He's on his way to Kentucky to pick up an FD shell to put it into. The engine has a custom machined eccentric shaft and will be turbocharged: http://www.autotechmotorsports.com/projects-4rotor.htm

how would you synchronize the 2 dis 4 digital boxes?They'd both have to receive the same engine speed signal yet respond at different times.

Hmmm.... is there a way to send the signal from the first box to the second box, but delay it? Just a shot in the dark. There has to be a way. How would to propose to use the single box over the 2?

congratulations, I'm happy for him. However, I'm going n/a, carbed, and into a SA/FB shell specifically built for Bonneville, while maintaining street legality.

http://pineappleracing.com/ProdSvcs.html

While 2-rotor rotary engines are the norm, Pineapple Racing can claim to be one of the few shops to have worked on 1-, 3-, and 4-rotor engines, as well.

-bp-

Pineapple was who I was originally planning on getting the e-shaft from, but it looks like, if possible, MarvelSpeed is gonna be building my entire motor. THANK GOD FOR HOOKUPS!

Now I still don't know about 3 or 4 rotor E-shafts prices... :-( Come on, is this really as expensive as the original quote by Chef?

Pineapple said $1899+shipping (USD)

MarvelSpeed said they would *probably* include it in the engine buildup price.

The racing beat FD Bonneville car is a tube car and makes in excess of 900HP utilizing a 13G/20B engine and I believe tripple turbocharged. The engine sits litterally in the middle of the car. The speed they recorded back in 1995 is 242 MPH.

Using your carbed 4rotor 12a, you may not even come close to the HP figure that racing beat had.

In comparison, to stimulate some though, the 4 rotor R26B in the 787B race car, is fuel injected, tripple spark plugs, with complicated trumphet intake system makes in excess of 700HP. I doubt that your custom 12a 4 rotor utilizing a carb and non supercharge/turbocharge, with an unproven custom shaft design will even come close to those HP figures.

Have you tried computing in paper the weight of your car, wind resistance and how much HP you need to reach your target speed? Just curious, how many attempts have you done at Bonneville?
:cool:

rx720bt: all valid questions and concerns. MarvelSpeed in TX (Dallas, I believe?) is doing most, if not all the motor build. I have emailed them (Don Marvel) with the exact specs of what I want. I am still awaiting a reply on pricing.

With a full fuel cell (18gallons), 2-15# nitrous bottles, airbag setup, full rollcage (12pt.), lexan rear/side/ 1/4 windows, 2" chop from the roofline, custom made windshield (2x thickness, with 2" chop already), belly pan, 15x4.5" wheels, GoodYear Eagle Land Speed tires, extra aerodynamic spoilers (either aluminum or carbon fiber), and 2 occupants (a friend has agreed to pay me 1000 to ride shotgun for the ride), I *should* be right around ~2800#. With a 1.92 final gear ratio, a Tremec T56 from either an LS1 or a Viper (not yet decided), the engine tuned to run at a strong 8grand for 3 minutes or more (of the two course choices, 5 or 7 miles, I am choosing the 7 mile one), and 2-200shots of nitrous, I should be well ahead of my required 776rwhp. I am looking closer to 1200, maybe 1300.


With a coefficient of drag at a near perfect .27 based on the CAD designs, and a lower frontal area due to the 2" chop, I *should* be right on the money.

By plugging in my numbers....


W= 2800
fA= 19.5
Cd= .27
tV= 264

Required whp = 686.95hp
Assuming drivetrain loss of 15%, required crank hp = 790