I had an '87. The car was a rat and not particularly fast, but the motor was fun and bulletproof. Looking at the ads, early Renesis motors are a dime a dozen.
I had an '87. The car was a rat and not particularly fast, but the motor was fun and bulletproof. Looking at the ads, early Renesis motors are a dime a dozen.
The silky smooth way a rotary revs is addicting.
dean1484 said:The silky smooth way a rotary revs is addicting.
Once you drive a bridgey, everything else feels leaden and dull. The most responsive turbos feel like you are controlling the throttle by a phone call to the Moon and back,
Rotary's fare much better when used in race applications. The constant revs help them live. Part of the reason street driven rx8s got a bad rap. They need to be beaten on to survive.
High load good, low load bad. Revs alone are pointless, pushing the skinny pedal into the front bumper is the rotary's salvation.
RX8driver said:Waaaaay back when I had my FC, I did a bunch of reading on what would make the ultimate street NA rotary. The 13B-RE from the Cosmos has some of the biggest and shortest intake manifold runners, can take a pretty big street port and will make good power when NA. I seem to recall that some of the throttle bodies (FD maybe?) had a larger lower opening compared to many earlier ones and would therefore be a bit less restrictive.
For higher rpm durability, use S5 NA rotors (or RX8 milled to take earlier 13B apex seals), RX8 stationary gears and bearings and run an external oil supply line to the front bearing. Run higher oil pressure, bypass the oil pump outlet in the front cover and tap the front iron for that instead (front cover can flex and bleed oil pressure). Rotor gears can come loose, but some of the spring pins can be pulled and replaced with set screws to keep the gear from walking out at higher rpm. If going above 8000 rpms, consider adding a little clearance to the rotor tips so that they don't touch the irons, or if wanting to go really extreme.
You're not going to find it in a local scrap yard, but if starting from scratch, maybe not the worst idea.
All that said, a Renesis is the easy button, other than making the ECU happy in something other than an RX8.
I have been turning 10k+ with Series 4 rotors and GSL-SE eccentric shaft and stationary gears for years.
The 12-pin rotor gears in use since 1986 are much kinder on the gear tooth interface tham the old 9 pin setup, which had gear loadings shoot to the moon over 8000. This is why they used to sell hardened stationary gears, and modify the rotor gears for retention clips. All not necessary if you have 12-pin rotor gears.
being able to use 2mm apex seals instead of 3mm explodium apex seals is a nice bonus. 2mm iron seals live at high RPM, 3mm break over 8500, so you have to use short-lived carbon-aluminum with an old 3mm seal rotor, after you unberk the rotor gear problems.
The front bearing issue is not caused by front cover flex, it is caused by turbulence in the dowel pins. OTOH I also run 90psi oil pressure up to 11k with very simple mods, mostly use of a 12A oil pump (smaller pump = less high RPM cavitation) and some judicious porting of the front housing's oil passages. Lots of porting.
An engine from the FC or 8 are both good options. The renesis makes more power out of the box so no need for porting and it will idle better than a bridge or pp.
Bridge ports are hard on side seals due to the lack of side support, Need more idle rpm and are louder
In reply to amg_rx7 (Forum Supporter) :
RX-8 engines are hard on side seals because hot exhaust gases contact them.
Bridge ports are no harder on side seals than stock ports. It is early-opening street ports that are hard on side seals (if you don't make good landing zones) because the trailing and sometimes leading edges of the side seal end up unsupported. A bridge port will leave the stock port's opening line alone, so side seals remain well supported.
Hi Kreb,
I'd just get a Renesis and be done as it seems to me the only case against this approach is that you'll need to keep the ECU and make it think it's in a RX-8 or go with a M.S. set-up or put a carburetor on it (I consider option #3 to be more theoretical than practical).
For reference, I've put 282K on a new NA 13B, 87K on a new Renesis, 152K on a rebuilt Renesis, and 6K on an original 12A that had 42K when I bought it.
Maybe you're going for an engineering challenge or maybe your bar is set higher than mine in terms of the definition of "major undertaking".
A Renesis would make a 1,400 Lb. car absolutely scream (again, perhaps your bar is set higher than mine) right out of the box...no turbo lag and no massive surgery on the engine. Reneses engines don't have good longevity but given that you're building a 1,400 Lb. car, it's pretty obvious you're not looking for a daily driver appliance that'll give you ten years+ with nothing more than oil and tire changes.
Bottom line, a healthy Renesis with a compentent master should hold up way out into the future given the hours it'll likely see in your application.
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