Rotary Alpine

[bobw]

I thought I would be making this report months ago, but it has finally happened. I started my Alpine with the Mazda rotary engine. Mostly it went smoothly with only one wiring glitch that held me up for about 10 minutes. Video posted on YouTube at http://www.youtube.com/watch?v=FwceNc2ydN8

I also noted a rotary engine thread a few weeks ago. I will definitely make some comments, but have been too busy trying to get this thing running.

Note the Stockton 14" steel wheels, the steering wheel from the Colorado, and the Oak dash from Pennsylvania. (I'll get the referenced names later.)

Still a lot of work to do, but at least it's running.

Bob W.

 

[64beam]

Hi Bob,

Thanks for posting the video. Great job on the installation, it looks great. It looks like you have to drop the front suspension down a bit due to the weight difference. Is that the case? Are you still running the Alpine gearbox and diff?

Regards, Robin.

 

[bobw]

Thanks Robin,

I"m using the RX-7 transmission, but still have the Alpine rear end. I'm not planning any high performance driving until I get more familiar with how the installation is working. I'm thinking somewhere down the road I may put a Ford rear end in it to handle the higher power.

Bob W.

 

[Mod_Squad!]

That's awesome! I still remember my first startup with the V6. I wish I would have had someone taking a video. The first drive I had two fires. The first was electrical. The wiring was hanging all over and I was sitting on a tackle box to drive the car. A hot wire got pinched between the shifter and the trans tunnel and all of my wiring started to melt. Luckily I had a cut off switch on the battery. The second fire was a few minutes later. I got a good backfire through the carb and it started the aircleaner on fire. Luckily I have the fuel pump on a switch too. I love switches . I think you need a longer cord for the battery charge though .
Nice work!
Bryan

 

[todd reid]

Congratulations Bob! It's always a good feeling when they start and move for the first time.

I don't think the Alpine rear will have any problems with the Rotary HP, especially in street use. I'm quite sure Tiger Tom ran a stock rear in his for many years. If you want to change the ratio, add disc brakes, etc then maybe its a different story.

Keep up the good work!

 

[chris]

That was cool. Like the V6 the rotary engine looks like it was made to fit. I don't know much about them or their availability, but it looks like a good way to go.

 

[Jim E]

bobw,
Think the rear will be fine but sugest you change the woodruff keys in the hubs, may not need it but I know with the V6 conversion it is very easy to break a key and spin the hub, ruins the hub and the axle.. would also take into account what gear the car the engine/tran had before going to the ford unit, just to make sure you can get the gear set you want.

By the way what gear do the Rotary cars carry?

 

[bobw]

Thanks for the encouraging comments, and the info on the rear end being strong enough, particularly for the kind of driving I will mostly be doing. I'll check the woodruff key.

This is the data I have on transmissions and rear ends:

RX-7 Alpine SV
1st gear 3.475 3.353
2nd gear 2.002 2.141
3rd gear 1.366 1.392
4th gear 1.000 1.000
5th/OD 0.697 0.871
Rear end 4.100 3.89
Tire Dia (in) 24.9 23.78 My tires 23.6 (175/70 14)

This appeared to me to be a pretty close match. If I ever put in a new rear end, I would think I could go with a little higher ratio considering the revs I have available. The engine computer limits me to 7500 rpm, but I suspect the engine would do 9000 without complaining too much.

The steering wheel is from Ken Corbin I have some photos at http://bob-white.com/photos/alpine/steering-wheel/index.html. Ken does a great job on the steering wheels and I understand he is now making some that are more like the stock wheels. Mine is reduced to 14" dia. and the wheel is a little fatter than stock.

The dash came form Rick Ryan in Pennsylvania. I purchased it unfinished and without the usual instrument holes. After finishing, several things wouldn't fit in their holes, which is why the switches are all hanging down behind the dash.

I will say that now when I work on the car, it feels more like I'm fixing something rather than like I have this humongous project to complete. Much more relaxing.

Bob W.

 

[RootesRacer]

Bob,

You might also consider ditching the aviation ECU.

Tuning an engine with a single potentiometer is not very realistic even if it provides redundant control.

 

[bobw]

Tuning is quite a bit more sophisticated than that. The potentiometer only adjust the mixture as you drive which you won't have the capability to do with an automotive ECU. There are quite a few other adjustments that aren't obvious. One of the complaints I see frequently is the rotary is a gas hog, but I can run a much leaner mixture than a typical piston engine. I think with that pot, I will be able to cruise along with good economy. Drivability remains to be seen.

Bob W.

 

[RootesRacer]

Tuning is quite a bit more sophisticated than that. The potentiometer only adjust the mixture as you drive which you won't have the capability to do with an automotive ECU. There are quite a few other adjustments that aren't obvious. One of the complaints I see frequently is the rotary is a gas hog, but I can run a much leaner mixture than a typical piston engine. I think with that pot, I will be able to cruise along with good economy. Drivability remains to be seen.

Bob W.

When I saw your writetup on the aviation ECU, I was very interested as I design automotive ECUs.

The ECU you run, other than having 2 of everything on it for redundancy, lacks many of the items that make automotive ECUs why its so easy to drive new cars.
Most aftermarket ECUs have the ability to run a "mixture" pot like what you have, but with the advent of closed loop lambda control, such a tuning tool would be totally unnecessary and not something you would want to be messing with while trying to overtake a large semi.
Also the aviation ECU lacks a barometric sensor, which is an important sensor in speed density systems. I suspect the knob allows you to tweak for barometric compensation as you need it.

The reason for the lack of sophistication on that ECU is probably because it was intended to run at idle and near max load, but not in between.
Automotive systems are used at the lighter end of the load envelope 99% of the time, so making it work well between idle and max load is paramount.

One last engine control related comment I will make (on the rotary) is that leading and trailing spark are not for redundancy, nor really is it an emissions item, but rather the timing of the two plugs is intended to cause a collision of flame fronts at a particular location and at a particular rotor angle both for detonation prevention, and production of max rotor torque at the angle of greatest mechanical leverage.
Mazda (if anyone) really perfected the Wankel design and learned that two plugs were needed to properly time the combustion to prevent apex seal fractures due to detonation.
If turning off either spark doesnt cause the engine to loose measurable power, one or both the timing angles is not correct for that particular load point.

This is one of my favorite conversion engines, I really like the idea of such a lightweight engine and all the revs that a rotary engine has.
In my opinion, the only thing better than a rotary powered alpine, would be a big assed turbo rotary alpine.

Kudos on the conversion and hope to see more.

 

[bobw]

An aviation ECU without a barometric sensor would be non functional. Operating from sea level to possibly 18000 ft. or more is quite a range of air density. This ECU operates on a MAP table which can be adjusted to compensate for variability of the input, but once set doesn't have to be messed with. I didn't make the function of the mixture pot clear. It isn't used to compensate for barometric pressure changes. It allows the mixture point to be altered for the entire MAP table.

I think you are overly concerned with the split timing issue. The aviation users have found no advantage, and I found this quote on the MegaSquirt site: (http://www.megamanual.com/v22manual/rotary.htm).

Mike Robert spent some time on a dyno last year and was able to test what happened in the case of stock 'spilt' spark timing, trailing only, leading and trailing firing simultaneously (no split) timing and leading only timing.

The results were:

* Leading and trailing spark in a roughly stock timing split configuration gave ~164 RWHP @ 8500.
* Trailing spark only only ran very badly (as expected) and power was way down, EGT was high enough to make the exhaust medium red; that run was aborted.
* Leading and trailing spark firing simultaneously were no different form stock split until after 6500 rpm or so; even then the difference was almost negligible.
* Running leading only spark produced about the same power as well, within error margins.

All of these tests were run with 26 degrees leading advance max on 87 octane pump gas.

However, idle and low load emissions might be better running both Leading & Trailing spark with split timing.

The concern with detonation is "only" for boosted engines. It just doesn't happen on an NA engine. Even so, there are several boosted rotary engines flying successfully with the EC2 controller. See John Slade's turbo Cozy at http://www.canardaviation.com/cozy/ or Dave Leonard's turbo RV-6 at http://n4vy.rotaryroster.net/.

The main reason I'm using the EC2 is that I already had it. Certainly a closed loop system would be more straightforward to set up and operate. If I find that the EC2 doesn't give acceptable results I will be checking back with you on a suitable alternative as I have no doubt that you are more knowledgeable than I on the use of ECU's in an automobile. I'm just doing a little experimenting.

Bob W.

 

[RootesRacer]

Bob,

With regard to what you read about megasquirt and the rotary engine, take it
with a grain of salt. These guys are notoriously cheap and often come up with solutions that sacrifice function against cost.

Megasquirt cant run 4 separate ignition phases so their solution would be to use a mazda 4 phase (2 coils, 2 phases plus 2 splits) distributor or just run two phases and ignore the trailing timing since both plugs would fire simultaneously.

Also just becuase its N/A doesnt mean you dont need to worry about detonation.

Any system (other than the OEM mazda controller) will have some sort of ignition mapping for timing based on RPM, load, intake or coolant temps.
If you tune it yourself, then you will supply this map, likely based on a base map from someone who has tuned that type engine before.

The ignition timing and split (in this case) has a bunch to do with the porting (rotary int/exh timing) combustion volumes and EGT tolerance.
Timing will be different on each engine build type (like your engine guy built one special for you, it wont have the same mapping as a stocker), and timing
is setup so as to provide max combustion pressure (without det) as some magical rotor angle.

Running too much timing in a particular load point will result in detonation, naturally aspirated or not.
Not enough timing and your EGTs will go through the roof.

Either one will destroy your apex seals, the difference is the mode of destruction and the amount of time it takes to do the damage.

Most engines, rotaries included have about a 2 degree band of where EGTs will be the lowest they are going to get without detonation.

This means that unless your ECU was mapped specifically for your engine build, it had better be within 2 degrees of optimal across the map or you
will either have det, or EGTs higher than they could be.

Since your engine and ECU was designed to be run near 100% load most of the time, I doubt that ignition timing is optimal at light loads since this would require dyno time during tuning, and the engine/ECU was not intended to live
in that regime. In fact, much like the nascar boys, many folks run a locked out distributor or magneto set to the optimal high RPM, high load timing and live with that timing in the non optimal sections of the map. This is often acceptable for specific applications since it reduces complexity of the system and yeilds ideal timing in that narrow band of operation.
You'll never pull of driving a car on the street that way though.


And of course if you ever need any help in the matter, feel free to message me.

 

[bobw]

I've already posted all I know on the subject, maybe more. I'll keep the forum up to date on how I'm progressing, and will definitely take you up on your offer if I can't get the results I want with the EC2.

Thanks,

Bob W.

 

[bobw]

Rotary Alpine Motif Badges

My Alpine is in the paint shop, where it's been for the last 3 weeks. One of the pieces I was missing were the motif badges on each side and trunk. I ordered the chrome surrounds from Sunbeam Specialties, but decided to get something a little different for the badge. I ordered a series badge to have a sample, then found a local shop that could make something similar. My first attempt was pretty poor. I didn't get enough silver paint in the lettering and when I added the black background, it bled through pretty badly.

I've attached a photo of the first attempt, the second attempt, and the reference sample from Sunbeam Specialties. The silver color isn't as bright on my badges as the SS sample, but there isn't as much difference when looking at them as you would think looking at the two photos. I used a Krylon color called "Metallic Shimmer" for the silver. There was another color called "Chrome" that might have done better. On the car, these look pretty good, so I think I'm done experimenting for now.

Paint progress through primer can be seen at http://drop-of-color.com/webalbum/current/Alpine/
(There are three photos of a Thunderbird that aren't supposed to be in there)