Engine Help - '79 12a
09-09-06, 12:20 AM
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Engine Help - '79 12a
So, I'm helping a freind out with a 1979 RX-7 that's in....well....odd shape. The car sat...completely still..... for 13 years. And, apparently wasn't driven much back in it's day either.....it only has 37K miles on it. The plan is to rebuild the thing. Get it back to stock condition, replace or rebuild everything that needs it; and then possibly modify from there. We've re-done the suspension, steering, brakes and cleaned the body (undeneath) all pretty...and now we're ready for the motor.......
Here's the back story.....The car sat for 13 years up in Canada (yeah, there was a little rust and corosion...we've cleaned all that off the chassis though). About 2 months ago, the car was towed to a garage where a "mechanic" got it running again. The mechanic replaced the gas tank and did a basic tune-up to get the thing running. Then it was driven 1,400 (scary) miles to Colorado. When the road trip started, the car ran pretty good they say. But, when they arrived in CO the car was backfiring and blowing blue smoke on startup....and altogether kind of rough.
I know the elevation difference is taking it's toll. I've got to figure that the carb needs to be adjusted and the timing is probably way off too. Which might explain the backfiring. But, that "blue smoke on start up" problem is bugging me. The smoke is pretty heavy and does fade some once the thing warms up. But, you can still smell burnt oil when it's warm.
Does anyone have any suggestions?....are they any common causes for burning oil on startup with these motors?
I'm contemplating tearing the engine down and replacing all the seals...but very hesitent to tear apart an engine with only 37,000 miles on it (plus I'm anything but experienced with rotary motors....although not afraid of it either). I've found that any metal or rubber that was painted, covered or otherwise "inside" of something is in prestine condition. Anything that was exposed is gone, though. And, based on that, I want to make the assupmtion that the engine internals are in good condition (and I should therefore look for other causes of the oil burning problem).
Can someone explain the "oil injection" system to me? I know how it works, how to adjust it, and that it's suposed to dump about 2 cc's of oil per 6 minutes.. But, how reliable of a system is it? Does it require a lot of attention....routine inspection/adjustments? Are their any common failures for it? Can the elevation difference affect it's pump rate?
I have a suspicion that the sitting around for 13 years and the 3000 feet of elevation gain have the thing way out of adjustment. And, that is what is causing the blue smoke on start up.
It may be wishfull thinking on my part, but I have the engine torn down to the block and, aside from the corrosion on the outside, the block looks to be in good shape. The intake and exhust manifold gaskets were in pretty good condition when I took them off. I've peered into the intake and exhaust ports.... and nothing looks out of line there. There's no score marks or strange things visable in the rotor housing. The motor turns very smoothly. Doesn't seem to have leaked any oil through gaskets (except for the oil cooler lines....they're gone). I'm going to pull the front cover off and have a look in there soon. But so far, aside from the blue smoke on start up, I've got nothing that tells me this motor should be torn down.
Can someone with some experience offer some advice? I've read everything I can get my hands on about rotary motors, but there just isn't much diagnosis info....or explanations of what all these components and things associated with this motor do.....and why they do it.
Here's the back story.....The car sat for 13 years up in Canada (yeah, there was a little rust and corosion...we've cleaned all that off the chassis though). About 2 months ago, the car was towed to a garage where a "mechanic" got it running again. The mechanic replaced the gas tank and did a basic tune-up to get the thing running. Then it was driven 1,400 (scary) miles to Colorado. When the road trip started, the car ran pretty good they say. But, when they arrived in CO the car was backfiring and blowing blue smoke on startup....and altogether kind of rough.
I know the elevation difference is taking it's toll. I've got to figure that the carb needs to be adjusted and the timing is probably way off too. Which might explain the backfiring. But, that "blue smoke on start up" problem is bugging me. The smoke is pretty heavy and does fade some once the thing warms up. But, you can still smell burnt oil when it's warm.
Does anyone have any suggestions?....are they any common causes for burning oil on startup with these motors?
I'm contemplating tearing the engine down and replacing all the seals...but very hesitent to tear apart an engine with only 37,000 miles on it (plus I'm anything but experienced with rotary motors....although not afraid of it either). I've found that any metal or rubber that was painted, covered or otherwise "inside" of something is in prestine condition. Anything that was exposed is gone, though. And, based on that, I want to make the assupmtion that the engine internals are in good condition (and I should therefore look for other causes of the oil burning problem).
Can someone explain the "oil injection" system to me? I know how it works, how to adjust it, and that it's suposed to dump about 2 cc's of oil per 6 minutes.. But, how reliable of a system is it? Does it require a lot of attention....routine inspection/adjustments? Are their any common failures for it? Can the elevation difference affect it's pump rate?
I have a suspicion that the sitting around for 13 years and the 3000 feet of elevation gain have the thing way out of adjustment. And, that is what is causing the blue smoke on start up.
It may be wishfull thinking on my part, but I have the engine torn down to the block and, aside from the corrosion on the outside, the block looks to be in good shape. The intake and exhust manifold gaskets were in pretty good condition when I took them off. I've peered into the intake and exhaust ports.... and nothing looks out of line there. There's no score marks or strange things visable in the rotor housing. The motor turns very smoothly. Doesn't seem to have leaked any oil through gaskets (except for the oil cooler lines....they're gone). I'm going to pull the front cover off and have a look in there soon. But so far, aside from the blue smoke on start up, I've got nothing that tells me this motor should be torn down.
Can someone with some experience offer some advice? I've read everything I can get my hands on about rotary motors, but there just isn't much diagnosis info....or explanations of what all these components and things associated with this motor do.....and why they do it.
09-09-06, 11:02 AM
#2
Long post for the first one, and nicely detailed too. Thank you, and welcome to the forum.
Blue smoke on start up is common. If it's excessive, or continues after warm up, the oil contol o-rings are worn/hardened. Carrier rings for the o-rings can be worn also, but not with your mileage. Since the engine has sat for so long, there is more than likely some carbon causing the side seals to stick.
In my sig line is a link to the online FSMs. Download them and keep them handy.
Do not pull the front cover, or the main pulley boss until you are sure you are rebuilding. If you do, you have to do it right. You have a lot of reading ahead of yourself.
Check into the bringing a 7 back to life link in the FAQs, you're a bit ahead of yourself.
If your exhaust system is in good condition, save every piece of it as it is no longer available.
Blue smoke on start up is common. If it's excessive, or continues after warm up, the oil contol o-rings are worn/hardened. Carrier rings for the o-rings can be worn also, but not with your mileage. Since the engine has sat for so long, there is more than likely some carbon causing the side seals to stick.
In my sig line is a link to the online FSMs. Download them and keep them handy.
Do not pull the front cover, or the main pulley boss until you are sure you are rebuilding. If you do, you have to do it right. You have a lot of reading ahead of yourself.
Check into the bringing a 7 back to life link in the FAQs, you're a bit ahead of yourself.
If your exhaust system is in good condition, save every piece of it as it is no longer available.
09-09-06, 12:11 PM
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I already have the FSM..... and have read it cover to cover. And quite frankly...that FSM leaves a LOT to be desired. The least MAZDA could have done was put an exploded view of the engine in there. All it has is disassembly and assembly instructions; the pictures are poor at best and it doesn't tell you or show you what parts are where. Is there someplace I can get a good, detailed exploded view of the 12A motor?
I knew the blue smoke was common....but this motor is wayyyy out of wack....We filled a garage with smoke in the time it took to get the motor running and back it out (and nearly asphixiated ourselves).
The exhaust system was gone, gone, gone. Any exposed metal on the car was rotted. The outter shell of the header pipe was rotted through and the insulation was hanging out. The rest of the system was hopeless too. We can get some exaust parts but, I figure we're gonna have to fabricate a lot of it. How are these motors for headers? I normally hate headers....but is there a noticable power increase with them?
Where exactly are these oil "control" rings you speak of? If the FSM was worthy, I could look that up....but it's not. Are these the circular rings that are on the side face of the rotors (just outside of the shaft bore)? The FSM calls those the "oil seal". Or are these the long, straight(er) seals on the sides of the rotors that go from corner to corner to corner?
I'm still looking for information on the oil injection system. If anyone has anything, I'm all ears.
How critical is the air-pump to this motor? We used to cut the drive belt on GM cars that had those back in the early 80's (all they ever did was cost power and seize at 30K miles anyway). Is it at all critical to engine performance on a rotary? The car never has to pass emissions (only needed to be tested when it was registered and it passed)...so if that's it's only purpose...it's a goner.
Thanks for your help on these stuff.....I'm finding there is not a lot of readily available info out there on these particular motors. Seems anyone who already has the knowledge, only wants to sell it.
I knew the blue smoke was common....but this motor is wayyyy out of wack....We filled a garage with smoke in the time it took to get the motor running and back it out (and nearly asphixiated ourselves).
The exhaust system was gone, gone, gone. Any exposed metal on the car was rotted. The outter shell of the header pipe was rotted through and the insulation was hanging out. The rest of the system was hopeless too. We can get some exaust parts but, I figure we're gonna have to fabricate a lot of it. How are these motors for headers? I normally hate headers....but is there a noticable power increase with them?
Where exactly are these oil "control" rings you speak of? If the FSM was worthy, I could look that up....but it's not. Are these the circular rings that are on the side face of the rotors (just outside of the shaft bore)? The FSM calls those the "oil seal". Or are these the long, straight(er) seals on the sides of the rotors that go from corner to corner to corner?
I'm still looking for information on the oil injection system. If anyone has anything, I'm all ears.
How critical is the air-pump to this motor? We used to cut the drive belt on GM cars that had those back in the early 80's (all they ever did was cost power and seize at 30K miles anyway). Is it at all critical to engine performance on a rotary? The car never has to pass emissions (only needed to be tested when it was registered and it passed)...so if that's it's only purpose...it's a goner.
Thanks for your help on these stuff.....I'm finding there is not a lot of readily available info out there on these particular motors. Seems anyone who already has the knowledge, only wants to sell it.
09-09-06, 12:35 PM
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Ohhhhhhh....the Mazda Parts catalog......there are the pretty exploded views I wanted.
I'mprobably getting wayy ahead of myself here......but, can someone tell me about porting these engines. On the block, is there a specific area I want to cut down or stay away from....or is it just the standard "open it up as much as you dare" routine?
I'mprobably getting wayy ahead of myself here......but, can someone tell me about porting these engines. On the block, is there a specific area I want to cut down or stay away from....or is it just the standard "open it up as much as you dare" routine?
09-09-06, 12:44 PM
#5
The oil control o-rings sit in a steel carrier, 2 per rotor side, and seal the oil in the rotor from the side seals. The side seals seal the oil seals from the combustion chamber also. Confusing, sorta.
Headers/full exhaust are the 1st, and best, performance upgrade, followed by intake/carb, then engine porting, in that order.
If you disable the air pump, the exhaust manifold will soon collapse and plug. The SAs do not have cats.
Download the 84/85 FSM for a better view of the engine and most of the cars components. The early manuals are very poor on info and diagrams. Very little difference in 12As in the 1st gens. Most differences are external, carb, emissions etc.
Headers/full exhaust are the 1st, and best, performance upgrade, followed by intake/carb, then engine porting, in that order.
If you disable the air pump, the exhaust manifold will soon collapse and plug. The SAs do not have cats.
Download the 84/85 FSM for a better view of the engine and most of the cars components. The early manuals are very poor on info and diagrams. Very little difference in 12As in the 1st gens. Most differences are external, carb, emissions etc.
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09-09-06, 02:01 PM
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That's actually more HP than I was looking for. We were hoping for 50 or 60 total. Just something to make it a little more fun in the turns.
How is the exhaust manifold going to callapse without the air pump? And this car does have a cat.....or atleast something that looks like a cat. Although, it probably won't be there when I'm done with it.
How is the exhaust manifold going to callapse without the air pump? And this car does have a cat.....or atleast something that looks like a cat. Although, it probably won't be there when I'm done with it.
09-09-06, 02:10 PM
#9
I have been scratching my head, and memory, again. The SAs have a thermal reactor and I can't think of the name of the other part. The exhaust manifold can over heat and collapse, the piece in place of the cat doesn't.
The air pumps adds fresh air to the manifold to enable a cleaner burn of the exhaust, without it they overheat.
The air pumps adds fresh air to the manifold to enable a cleaner burn of the exhaust, without it they overheat.
09-09-06, 03:42 PM
#14
Welcome to the forum. You will find a crazy wealth of info here as you probably have already seen. As well as very helpful people (cough....cough....trochoid.......cough.....rougue wulff....cough). I would love to see pics of your SA when you have a chance to post them.
09-09-06, 03:44 PM
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All very interesting.....apparently I've come to the right place.
That exhaust manifold is awefully funny looking....I was wondering what the big chamber was all about. Adding air to the exhaust will only keep the fuel burning in the exhaust system though....which should actually heat things up more.....I would think anyway.
If we go to hearders....how does that work? Do I still need the air pump and heat exchanger?
That exhaust manifold is awefully funny looking....I was wondering what the big chamber was all about. Adding air to the exhaust will only keep the fuel burning in the exhaust system though....which should actually heat things up more.....I would think anyway.
If we go to hearders....how does that work? Do I still need the air pump and heat exchanger?
09-09-06, 03:51 PM
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If you go with a header, toss the TR, heat exchanger, and air pump in the recycle bin. At almost 100LBS, they'll bring a penny or 2.
Yes, the fuel continues to burn in the TR system, that's how it was designed, to clean up emmissions.
If you want to use a high-flow cat, keep the air pump. These will keep it evironmentally freindly, without harming power output.
Yes, the fuel continues to burn in the TR system, that's how it was designed, to clean up emmissions.
If you want to use a high-flow cat, keep the air pump. These will keep it evironmentally freindly, without harming power output.
Last edited by Rogue_Wulff; 09-09-06 at 03:56 PM.
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