- This topic has 6 replies, 5 voices, and was last updated May 26, 2005 at 6:54 am by
.
-
Posts
-
-
-
-
Ohighway,
There have been posts on the SAOCA Forum (http://www.saoca.org/sforum/) by Scott Rohr about his S-I with a 12-A Mazda rotary, Don Scott about his S-II with a 12-B and John West about his S-V with a 13-B.
All of them said the engine and transmission fit the Alpine very nicely, but the stock exhaust manifold will not fit and a custom exhaust is necessary.
Scott and Don are SAOCA members. If you are interested, let me have your contact information and I can send them an e-mail asking them to get in touch with you.
-
I can be reached at: ohighway@gmail.com Thanks.
-
Dear Ohighway,
This is a bit long, but in case anyone else is interested: I would actually recommend using a 13B. Better parts availability and more power. The 13B is only a couple of inches longer than the 12A, so the fit is still excellent. Surprisingly, rotary engines in my experience anyway, are not very fuel effiecient. I get about 18 MPG. Something you might want to keep in mind with today’s fuel prices. The best places for performance parts are Mazdatrix and Racing Beat. The former is in Long Beach, CA – and just down the road from my house actually. Racing Beat is in Anaheim, CA. They have a great catalogue with some interesting information on performance rotarys. They charge for it, but it’s worth it.
The biggest problem, and I think Barry mentioned this, is the exhaust. You’ll have to build the header yourself or find someone to do it for you. You won’t find anything off the shelf that will really work. If you can weld and have access to either a stick or MIG welder, Racing Beat has a header kit that you can work up yourself quite nicely. Even if you have it done by a shop, get the kit. The rotary exhaust temps are much higher than a piston engine and you really need the extra thick-walled tubing for it to last. Oh yeah, the Alpine appears to be a bit shorter than the RX-7, giving a shorter exhaust system and no room for the beefy muffler they use on the RX-7; and I have never really managed to get mine very quiet. I kind of like it a little loud, but some may not.
Depending on where you live the cooling system may be a problem as well. When I built the car originally I lived in Seattle. The mild climate was no problem for the stock Alpine radiator, butI moved to New Jersey and the hot summers there were really tough on the car. When I moved to Los Angeles I decided this had to be fixed. I spent a lot, about $400, on a custom made aluminum radiator – best money I spent on the car. No over-heating problems at all. If you live anywhere except the Pacific Northwest, plan this in your budget.
A couple of years ago I installed a webber carb and intake assembly from Mazdatrix. That made a huge difference in power from the stock RX-7 carb I was using.
Most of the rest of the pieces you will have to fabricate are pretty easy and you can do with a modestly equiped garage. Bottomline is plan on spending a couple of grand on the project, but this really depends on how much you do yourself and how you want your engine built. I’ve done everything myself except for the radiator and cutting the driveshaft. Well, and a large airplane manufacturer formerly headquartered in Seattle was kind enough to do a little free machining work for me before my dad became a retired engineer. A driveshaft will only run you about $100 at most any shop and I don’t think you could ever do it as good as a shop can.
Unfortunately, I have lost or misplaced many of the photos I had of the various stages the car has been through. Mostly due to a careless changing of hard drives in my computer last year – damn it. However, I can look around and see what I can send you if you’re interested.
Hope you go for the conversion and feel free to ask any questions you may have. I’ve owned this Alpine since 1984. When I got it, it was more or less a planter box for blackberry bushes. I got the car running, then started the first conversion in 1987. I had the rotary running by 1989. During the early 90’s my job with a travel company kept me from making much progress on it though. In the mid-90’s I got back into it and after a little moving around and several incarnations, I really just “finished” a fairly complete restoration and the final version of the engine swap in about 2002. This car was also my daily driver until about 1999.
It seems the most popular choice for conversions is the (Ford?) V-6. You can find lots of discussions about that on saoca.org and here too I’m sure. I’m really happy with my project, but I’ve enjoyed the process as much as the finished product. If you decide to go the rotary route; I’m sure you’ll end up with a car you’ll enjoy, a realiable driver, and very decent performance, although the basic engine cost will probably be a little more.
Good luck with your project,
Scott Rohr
Lakewood, CA (Los Angeles)Series I Alpine – rotary conversion
Series II Alpine – future project
Mk III Jensen Interceptor – newest toy
Lotus Elan +2 – currently stalled project with a friend -
Scott hit on a lot of good points on a rotary installation. I’d like to embellish some of the points he made and address two omissions that will drive the fabricator up the wall.
First the exhaust. You cannot use standard mild 16GA steel exhaust tubing. I used a thick wall mild steel cause that is all I could bend on our exhaust machine. 14GA, if I remember correctly. It still blew holes through at the exhaust port. I finally solved the problem by forming and welding on a high grade steel plate of some unknown type.
The biggest problem with a street machine is noise as Scott alluded to. Personally I had a hard time accepting the piercing chain saw sound in an every day car. I spent hours on the phone with Racing Beat exploring the theory and application issues of rotary exhaust systems. And I spent years fine tuning the system.
Here is what I came up with and it worked very well except for one problem, which I’ll explain later. First, there were no Mazada exhaust mufflers or resonators that could be used on the Alpine cause they are just to darn big. Don’t fit, no way. Now I should add, this was in 1980. Times change so maybe there is something today. Anyway, based on what I learned from Racing beat and reading lots of tuner articles, this is what I learned. The Rotary likes a free flow exhaust system. Its power gains are based on exhaust flow characteristics at the port area and very short distance of the header. After that, keep system open and free flowing. The rotary engine produces a high frequency component in the exhaust flow. It traverses as a laminar current in the exhaust flow. So the first mission is to reduce the high freq amplitude by disrupting the high freq component. That is done by using a pipe with a fluted baffles in the interior, similar to what GM was doing in some of their large cars in the 70’s. Another example would be the side pipes used on Vettes. I accomplished this by using a cheap “cherry bomb” glass pack muffler. It worked great but the exhaust was still loud. The next thing I did was use “turbo” free flow mufflers. One midstream and one as a resonator at the tail pipe end. I tried dozens of mufflers til I found a combination that worked well to quiet the exhaust. I was able to get the sound level down to about what a MAzada was. Now to that problem. In the 70’s and 80’s there were NO aftermarket mufflers designed to work with a rotary engine exhaust. The high frequency component of the exhaust would cause the mufflers to resonate giving off a tin can sound.
I wrapped the midstream muffler with a 1/2″ layer of fiberglass and then wrapped that with a piece of aluminum flashing. It looked just like a normal muffler. This also reduce a lot of noise. Now the real problem, the internal baffles would vibrate and fatigue crack at the weld attachment points. Pieces of the baffle would then float around inside the muffler and rattle like a can of marbles. I never got more than six months out of a muffler before the baffles would disentigrateNow the two omissions.
1. Cooling. The rotary engine uses water AND oil to cool the engine. I forgot the percent of cooling the oil does but something like 40% is what I remember. Any way, the fabricator must allow for cooling for the oil too.2. Clutch. It doesn’t make sense to me but in Mazada’s infinite wisdom the throw out lever comes out the top of the bell housing, It makes for serious fabrication problems.
Tom Hall in CA did a rotary Alpine several years ago. I am not aware of him making it quiet Alpine.
-
I think I went a little more difficult route Tom. I used Racing Beat’s “header kit”, which is really just a big U-shape and two other lengths of their really heavy walled steel tubing pre-bent to a similar shape of their standard RX-7 header configuration and a mounting plate. You have to purchase the collector assembly separately. For some real backyard ingenuity, I took a piece of foam for insulating water pipes and used a coat hanger inside of the foam to make a rough mock-up of the header shape I needed. The crucial part is leaving enough room so the header doesn’t interfere with the end of the tie-rod with the wheels turned to the right. After I had my rough shape I cut up the “kit” pieces in smaller sections, tacked them together as I went, and finally pieced together the entire header. When I was satisfied it all fit I welded all the pieces together. It has worked great and once you grind the welds smooth and paint it, the whole thing looks pretty darn good.
You are completely right about the rest of the exhaust system. Mufflers just don’t seem to last very long. I too use a “glass pack” right behind the X in the floor. It was a lot worse when I had no interior, but now with a little extra padding under the carpet, and since I rarely drive with the top up anymore – it ain’t so bad.
You point on the oil cooler is important. I used the stock RX-7 oil cooler mounted in front of the radiator. It fits nicely under the cowl and the brackets were easy to build. I used the same mounting holes as the Alpine’s radiator, just using longer studs that stick out further to the front. This is the big oil cooler they used on the first generation RX-7’s. I would stay away from the water-cooled unit that mounts under the oil filter on the second generation Mazda’s, not having heard very good things about them. I think in Racing Beat’s catalogue it says Mazda uses the stock first generation oil coolers in their race cars.
I can’t say the throw-out lever was a big problem for me. It definitely is right up against the firewall in its furthest back position, but it seems like you wouldn’t really want to shove the engine and transmission any further back in the car anyway.
One point I did leave out is the rear end. My Mazda book says the RX-7 rear end is a 3.909, so the same as the Alpine, but I think the RX-7 has 14″ wheels. I’m not sure if that makes the difference; but I’m shifting out of first gear by the time I get across the intersection, the revs seem high to me at freeway speeds even though the rotary is a very high-reving engine, and my gas mileage seems poor. Someday when I get caught up on my other projects I’d like to try a Mustang II rear end. It seems like something around a 3.50 rear end would be more suited to the Mazda 5-speed and the Alpine’s little wheels. The rear disk brakes would be a nice update to the Alpine as well.
While not all that difficult, the electrical system was kind of tedious. Basically I left the light circuits, tore all the rest out and started from scratch. I wasn’t crying over losing the Lucas electrics, but it was a fair amount of work.
I’m curious what others have done about the cross-member and engine mount. Originally, I just made some cut-outs in the lower center section of the stock cross-member and welded some sheet over them. The rotary oil pan is wider than the Alpine’s stock engine. I actually used the stock engine mounts and made the front engine mounting plate out of 3/8″ steel plate. A little tech tip -make a mock-up with cardboard or fiberboard first.
However, in 1999 one of the pivots on the lower A-arm siezed up and I tore the A-arm away from the cross-member. For some reason I thought this was a good excuse to do a little cleaner and nicer job on the front mounting. I took a spare cross-member I had, cut the ends off and used square tubing to fabricate a new center section. I went to a local parts store and found some motor mounts that looked about right and made a new front mounting plate. Now it looks really nice and I’ve had no problems with it at all. I am a little concerned about ever selling it with a custom made suspension. I’m not sure what kind of liability I may have if it came apart, but I can’t really ever see selling this car with all these years into it. I guess I would just make sure any buyer was completely aware of what modifications have been made.
I really think this is a great conversion, but you don’t hear about too many people doing it. I’d love to hear what some of you have done if you’re out there.
Scott Rohr
-
- You must be logged in to reply to this topic.