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with (TD) Troy Graham
Rotary Engine Install: Part 1, Page 6
2:30AM, 23 April: After 3 weeks of intense knuckle-busting, swearing, coffee consumption, and sleeping in the garage, Mazuki cranked over and fired! She did not run well though, missing at idle, and stumbling under heavy load. Due to the 1/2 transfer shaft, she’s also got some pretty pronounced vibration, especially in the higher gears. 11:30PM, 23 April: Got the motor running perfectly by running switched power to the bowl vent solenoid and adjusting the idle mixture. Do some shimming of the tranny mount and get rid of most of the bad vibes. You wanna talk acceleration, buddy? She now charges past 60mph like the 1600 goes past 30mph! 5th gear passing is quick and easy. The exhaust is nice and quiet too – hmmmmmm…. 6:00AM, 24 April: Throw the boonie box, hi-lift, and all the off-road paraphernalia in Mazuki and head out for Attica, the acid-test. 10:00AM, 24 April: Wind up on the toughest trail in the park, after it has rained for a week. Wind up drowning Mazuki in a HUGE, bottomless mud hole about 1/8th of the way into the trail. This ain’t water folks, it’s soupy mud, and it’s coming in over the tailgate. I attempt to keep the motor running, but she eventually misses and stalls. The stock (probably original) spark plug wire boots do not seal against the plugs, and the disty, although mounted high, has no seal either. After drying/cleaning both out she comes back to life. She then ran flawless for the rest of the weekend.Conclusion: The Mazuki Project, while still needing some further development, is a resounding success. The rotary motor makes an awesome off- and on-road motor for a Samurai, better in almost every respect than a 1600. The idle and just-off-idle torque is impressive to say the least. With the 1600 idling at
900rpm, I could carefully let out the clutch in 2nd gear, low, without stalling the motor. With the rotary, I can dump the clutch in 2nd and feather it in 3rd. While idling up a 50% grade this weekend, I juiced it and easily broke all four tires loose. The abnormally heavy flywheel of a rotary only helps. The low-end torque concern about rotary motors is a non-issue.
The 4-barrel Nikki carb that came stock on the 12A rotaries is a PERFECT off-road carb. Whether straight up, straight down or nearly rolling, it NEVER stalled out or loaded up. I only detected a slight miss when severely off-camber to the right side, but it did not stall or load up. The jetting seems to be spot-on, based on the plug and exhaust color, indicating the factory runs the carb slightly rich, then leans them out with air control devices. One nice feature is the transition off-idle is really smooth and not at all sensitive or herky-jerky, like the FI Sammies can be. The clutch engagement is very smooth and progressive as well, and has a very light pedal pressure.(All you guys who have endlessly toiled to get those Webers to run right ought to figure out how to adapt this carb to your setup. There is only one wire to run, the rest of the carb is mechanical with a manual choke, and they are plentiful and cheap.) Near as I could tell from the 300 mile round trip, mileage is in the 18-20mpg range. Not as good as the 1600 (23mpg), but rotaries run best on the lowest-octane fuel you can find versus premium for a cost savings (~$.20/gal, X 8 gal = $1.60 less per tank using low test, whereas 4 mpg extra X 8 gal = 32 extra miles / 23 mpg = 1.4 gal X $1.30 per gal = $1.82) so that issue is a wash, IMO The jury’s still out on the single u-joint xfer shaft. I’ve tried several differing shim thickness’ at the tranny mount to get rid of a pronounced harmonic vibration that occurs in the higher gears. There is literally NO vibration through the first three gears, but fourth has a little, and fifth has the most. It also is not necessarily speed-related, because it does not occur at 55 in 3rd, but shift into 5th at that point, and there it is! At 60 in fifth it goes away, and comes back at about 65, then gets progressively worse to 90 (where I backed out of it – there was more there ;’) My theory is that the transfer case and motor are twisting on their mounts in different directions, and the higher gears exacerbate the problem, thereby placing higher lateral loads on the xfer shaft. And any minute clearances in the slip yoke and u-joint are causing the vibration. I’m thinking of coming up with a pseudo-Cardon-type/CV joint to go in there using bits from the stock xfer shaft, and moving the tcase backward ~1″ to accommodate it. This movement will be OK for my rear M/L application, but without it, the driveshaft might need to be shortened. ORRR… I am also thinking of fabbing a bracket to tie the tcase and tranny together, which would seem to be the easier of the two solutions. As it is, the crank in the motor and the input shaft in the tcase line up almost perfectly. More head-scratching….. The 10″ pusher fan I have is not sufficient, and will need to be replaced with a 12″, or more likely, 14 inch fully-shrouded, with a high CFM rating. The thermostat control I got through Summit Racing (Perma-Cool) is a joke and will be replaced with a VW-type thermoswitch screwed into a fitting attached to the radiator, then wired through a three way switch (like the “other” Troy Graham spoke about). The fan is currently ~3/4″ away from the rad, which is also a mistake, it needs to be close, like 1/8″. In the “Duh” department, I had a rad built with a high-performance core, which is a
3-row with “fine” finning. One good dunk in the mud near completely plugged it up! I turned the fan on right away and that blew some of the muck out, and it didn’t overheat, but it still made me nervous. A core with coarse finning would be the ticket here. One more reason to have on-board air, right? hehe At idle or light load (most of our off-road time), the rotary really did not seem to heat up that much. I checked the top rad hose temp against one of the stock Sammies in my group, and they felt about the same. My theory is, the rotary motor requires so little effort to turn over (you can literally grab the crank pulley and turn it over easily), it just doesn’t do much work, and therefore does not heat up. It seemed to actually run cooler on the trail than on the road.
The Mazda tranny is SOOOOO nice to shift, and is undoubtedly stouter than the Sammi one. Many thanks to the list members who helped me out and especially Larry Desaulniers (Mr. “Rotary God”).
08/11/10 15:19
