I picked up an 86 RX7 last weekend to use as a donor for my next build. I've been doing research and think I know a lot more but damn is the rotary world kinda confusing.
In no particular order:
- I found this guide to remove emissions (http://www.rotaryresurrection.com/2ndgen/tech_s4_na_emissions_removal.html). Mainly for weight reduction but also to simply the install and looks of the engine. Good idea?
- Should I get rid of the oil pump and premix? Why? Why not?
- I'm reading all kinds of things about the exhaust heat. I was planning on DIY headers with a front fender exit. Street would have side pipe but race would end at the fender. Would I be better off just reusing the stock exhaust and doing a rear exit?
- I am getting the idea that getting air in and air out of the engine is even more important for performance than a piston engine.
- I'll be removing the air pump, AC, power steering, and hopefully a freer following exhaust. Anything else I can do to get free/cheap power?
Feel free to dump any and all knowledge into my brain.
Oh goodness...
First and foremost... You will NEED a muffler. an unmuffled rotary is disgusting, annoying, crazy loud and generally, nobody but the person who owns the car likes it....
Without tearing the engine apart, expect to get about 150 WHP with all of the bolt on mods.
Remove all emissions! It is worth removing that stuff just for the simplicity factor.
If you remove all of the emissions stuff, you will need some way to actuate the 5th and 6th ports on the lower intake. Otherwise, just leave them wired open (you lose some low rpm grunt, but again, its simpler).
Headers for these cars are fairly cheap on the used market (like $75). They are typically fairly long for some "harmonics" reason. I have been told they REALLY help increase HP. I have never done a before and after test to verify.
An S4 OMP is fairly reliable. However, the heat of the engine has probably attacked the lines and the "spider". You will probably need to redo the lines. There is no downside to pre-mixing other than remember to do it!
Are you using the S4 chassis as well? If so, I have some tricks to get it to handle better (well, works for road course racing, should help autox too).
If you want real power, turbo it or port it. You can turbo without taking the engine apart, but you will decrease the life of the engine and it will be living a bit close to the edge.... It has been done and can be done with mostly factory parts.
Porting requires engine rebuild.
What ecu do you plan to run? If stock, make sure you grab the # 1 plug from the donor car and chase it the entire way to the drivers side of the engine and get all the terminations for that. The CAS wires are a shielded group of 4 wires that goes from the ecu, across the dash and into the engine compartment by the drivers side shock tower. It is best if you can remove all of this in 1 piece.
In reply to wvumtnbkr :
It'll be stock ecu at first but maybe MS later if we turbo it. We will not be using the chassis. I hear you on the exhaust. I want it right below obnoxious for street driving. Will be willing to be obnoxious for reaching if it gets more power or affects the budget.
You do not want to run any kind of exhaust that doesn't have the words Racing Beat in the name. Anything else will be both loud and short lived, with life measurable in minutes. (This is not hyperbole. I had one muffler that was obnoxiously loud, and then it blew apart after 30 minutes. That was a fun drive home)
Racing Beat exhausts are the quietest ones available that still flow worth a damn, and they are just to the legal side of obnoxious. I still wear hearing protection on long drives.
For reference. I have a video of a Starlet with an open header at the dragstrip. When it is sitting at the line, idling, you cannot hear the big block Nova in the next lane doing its burnout. At all.
If you do want to go custom for the exhaust, you'll want a thicker wall than typical for the heat and noise issues mentioned.
However, I'd go with Racing Beat. You'll end up re-creating what they've already done.
Pick up a copy of Street Rotary.
That addresses the majority of any questions you may have as well as the weaknesses of each variant of the 13b.
I love that information exists online, and there's a wealth of it for rotaries, but the rotary community informational pages are pretty tough to break open unless you're familiar with the exact terminology.
That and they're often a cesspool only slightly better than that of the MSF and VWVortex with half of Google's queries deadending in "Search noob."
For the unanswered question: Premix and oil metering pump.
Rotaries consume oil via a squirter in the engine. If it becomes clogged or the pump fails it eats the engine alive.
Premix eliminates the chance that can happen.
There's also options like the add-on from Rotary Aviation which piggy backs an oil reservoir to the OMP allowing you to monitor and run 2 stroke oil.
I think you should use a different drivetrain and donate the rotary to me
Patrick said:
I think you should use a different drivetrain and donate the rotary to me
I have a 13b engine and trans....
wvumtnbkr said:
Patrick said:
I think you should use a different drivetrain and donate the rotary to me
I have a 13b engine and trans....
Message me? I don’t need them right now but I’m going to build a locost in the future and the rotary makes much sense
In reply to The0retical :
Thanks I'll grab that. My searching did remind me of miata.net.
