I have just purchased an RX-7, i have some questions.
07-30-07, 10:19 AM
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I have just purchased an RX-7, i have some questions.
Hi, a few days ago i purchased a 1986 RX-7 First generation (i know they stopped making them in 85, it must have been registered the next year).
Its done 100000 miles, and has had a carbureted 13B fitted (13B has about 55000 miles on it) Its stock except for an aftermarket header and a 3" exhaust. Its very loud, sounds insanely cool, and sets off car alarms, my girlfriend wouldnt go for a ride in it cause it sounded so intimidating.
The engine is running very well, it was dynoed at 106kw 205nm (142hp 151 ft.lbs)
The question i have is, do all 13B's have 6 ports? Because this motor doesnt have any pipes going from the exhaust headers for activating the auxiliary ports, but with the power its putting out they cant be closed, and the bottom end power is good, this car has really nice grunt. Where would the the pipes connect? The header isnt very good, and id like to replace it anyway, so if i can id like to connect it all up properly.
Im not sure what carb it is (cant find any identification on carb), its four barrelled, probably a nikki, but the secondaries are mechanically opened, not via vacuum.
Car runs great, loads of fun, i have replaced the engine oil, gearbox oil, diff oil, oil filter, air filter fuel, fuel filter, all the normal stuff.
Oh and another question, how do you set the timing if there is no cambelt?
Its great to be part of the RX-7 community!
Its done 100000 miles, and has had a carbureted 13B fitted (13B has about 55000 miles on it) Its stock except for an aftermarket header and a 3" exhaust. Its very loud, sounds insanely cool, and sets off car alarms, my girlfriend wouldnt go for a ride in it cause it sounded so intimidating.
The engine is running very well, it was dynoed at 106kw 205nm (142hp 151 ft.lbs)
The question i have is, do all 13B's have 6 ports? Because this motor doesnt have any pipes going from the exhaust headers for activating the auxiliary ports, but with the power its putting out they cant be closed, and the bottom end power is good, this car has really nice grunt. Where would the the pipes connect? The header isnt very good, and id like to replace it anyway, so if i can id like to connect it all up properly.
Im not sure what carb it is (cant find any identification on carb), its four barrelled, probably a nikki, but the secondaries are mechanically opened, not via vacuum.
Car runs great, loads of fun, i have replaced the engine oil, gearbox oil, diff oil, oil filter, air filter fuel, fuel filter, all the normal stuff.
Oh and another question, how do you set the timing if there is no cambelt?
Its great to be part of the RX-7 community!
07-30-07, 11:39 AM
#2
Since it has a carburetor, I'm going to guess that someone put in an old school 4-port 13B. There were 4 port 13Bs but they are older, I think from REPUs? They may have come in Rx3s or Rx4s also. I can' really remember, but 4 port 13bs do exist, and I would guess that you have one. They are sorta rare, and very desireable... Nice find! Post some pictures!
07-30-07, 12:02 PM
#4
Welcome to the forum! The FAQ's are very helpful, as well as the "search" button. A FSM can be found here: http://www.wankel.net/~krwright/cars/cars.html
No, There were earlier 13b's that were 4 port only. These engines are more rare then other naturally aspirated 13b's. The 6 port 13b's are much more common as they were placed in 84-85 GSL-SE's and all NA 2nd gen's. As stated before, first post some pics of your setup and we can go from there.
From the factory the 6 ports were actuated by backpressure in the exhaust. A pipe from the main cat was routeded to 2 actuating diaphrams on the intake manifold. These diaphrams, when given 1-2 psi of pressure, turn a rod that is connected to a sleeve in the intake port. The system only works with a restricive exhaust similar to the factory. Once the exhaust is freed from the factory restrictions, there isn't sufficient backpreassure to supply the diaphrams.
The use of the 6 ports comes down to the intake manifold. If it is the factory piece then technically you could set it up. Personally, I would not recommend this.
There is a strong possibility that the sleeves were removed during the swap for maximum top end power. The 6 port design was trying to compinsate for the rotarys lack of low end torque. The result was a design that was flawed for modification and unreliable. Over time, the carbon buildup in the intake would restrict the sleeve's from turning and the ports opening.
www.racingbeat.com. Youwill find an assortment of quality exhaust setups. Though expinsive, these systems will withstand the high exhaust temps that are produced by rotaries.
The timing is set by marks on the main pulley. The complete proccess is in the FSM that I posted the link to.
Good luck.
Originally Posted by EpitrochoidalPower!
Do all 13B's have 6 ports?
Originally Posted by EpitrochoidalPower!
Where would the the pipes connect? The header isnt very good, and id like to replace it anyway, so if i can id like to connect it all up properly.
The use of the 6 ports comes down to the intake manifold. If it is the factory piece then technically you could set it up. Personally, I would not recommend this.
There is a strong possibility that the sleeves were removed during the swap for maximum top end power. The 6 port design was trying to compinsate for the rotarys lack of low end torque. The result was a design that was flawed for modification and unreliable. Over time, the carbon buildup in the intake would restrict the sleeve's from turning and the ports opening.
Originally Posted by EpitrochoidalPower!
The header isnt very good, and id like to replace it anyway, so if i can id like to connect it all up properly.
Originally Posted by EpitrochoidalPower!
Oh and another question, how do you set the timing if there is no cambelt?
Good luck.
Last edited by XLR8; 07-30-07 at 12:26 PM.
07-30-07, 01:29 PM
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Thanks for the reply guys, ill post some pics tommorow when there is some light, so if its a 4 port 13B that is probably pretty sweet for porting compared with the 6 port?
Oooh I like this
Now im really hoping for 4 port, because i plan on modifying this engine.
Oooh I like this
13B 4 Port - This is an early-model motor that was discontinued in 1986 for the 13B 6 port. This port setup produced up to around 140hp at its best. But because of its solid construction its an ideal platform to build up a high power race engine. There is a tremendous amount of material that can be removed to increase flow.
Last edited by EpitrochoidalPower!; 07-30-07 at 01:44 PM.
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07-31-07, 04:49 PM
#8
Sorry, I can't see the pictures. I am in the middle east right now and our filters block everything from Imageshack or Photobucket.
Anyway, The engine type should be stamped on the top of the housing on the drivers side, close to the distributor cap.
Anyway, The engine type should be stamped on the top of the housing on the drivers side, close to the distributor cap.
07-31-07, 09:29 PM
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it does look like it has an adapter plate for stock 12A carb all of the emision stuff has bon removed of off it. If money is not a huge problem I would go for a proper intake manifold that is designed for a 13B just becouse it flows more air the one you are using is restrikting the air to the motor I would also look into a bigger carb that should ease the motors air supply quite a bit. As for the 5/6 ports what is most likelly done is the sleeves that go in to the ports are taken out and it just runs the ports open all the time with that you sacrifice a little bit of bottom end tq but its not bad. As for the timing you set it by the main pulley that is not the e-shaft there are markings on it most of the time I just set mine just by listening to it becouse I suck and using the timing light eather set it wrong or get shocked.
07-31-07, 10:43 PM
#14
FB+FC=F-ME
Its definately a newer, EFI 13B from the 1st gen GSL-SE or the 2nd gens.
The only way it would be a 4 port would be if the engine had been built using a 2nd gen turbo engine as a base. All the turbo 13B's are 4 port style,whereas the N/A engines had the 6 staged intake ports to help boost torque.
Judging by the look of the car,the 1st gen waterpump/thermostat housing and everything else,Id say you have a GSL-SE engine converted to a carb.Did you uys over there even get the GSL-SE cars in 84-85?
If it were an 86-88 N/A 13B,there would be an EGR valve or block off plate on the center iron.
Its likely the 6 port actuators and everything were ditched when the adaptor plate went on for the intake manifold and the aux ports are wide open along with the secondary ports.The only downside is a bit of bogging if you floor it when the RPMS are too low,the topend power will still be the same.
There is still the chance you have a 4 port TII engine in there,the only real clue would be TII specific items on the 4 port irons......stuff like the turbo oil feed banjo on the front left corner,near the distributor.....or a knock sensor bung on the center iron under the oil fill tube (On S5's its on the rotor housing above the sparkplugs)
The only way it would be a 4 port would be if the engine had been built using a 2nd gen turbo engine as a base. All the turbo 13B's are 4 port style,whereas the N/A engines had the 6 staged intake ports to help boost torque.
Judging by the look of the car,the 1st gen waterpump/thermostat housing and everything else,Id say you have a GSL-SE engine converted to a carb.Did you uys over there even get the GSL-SE cars in 84-85?
If it were an 86-88 N/A 13B,there would be an EGR valve or block off plate on the center iron.
Its likely the 6 port actuators and everything were ditched when the adaptor plate went on for the intake manifold and the aux ports are wide open along with the secondary ports.The only downside is a bit of bogging if you floor it when the RPMS are too low,the topend power will still be the same.
There is still the chance you have a 4 port TII engine in there,the only real clue would be TII specific items on the 4 port irons......stuff like the turbo oil feed banjo on the front left corner,near the distributor.....or a knock sensor bung on the center iron under the oil fill tube (On S5's its on the rotor housing above the sparkplugs)
07-31-07, 11:45 PM
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It's got newer-style rotor housings, but they could be GSL-SE housings with old-school 4-port irons. That carb looks like a Hitachi to me (indicating an old-school engine) but I could be wrong. Where's Jeff20B? He could tell you for sure.
08-01-07, 01:41 AM
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Thanks for the replies guys, it does have 13B stamped on the rotor housings, if there is anything i can take photos of to help more just ask. Else when i have the time i'll just remove the intake manifold and take a look to be sure, im hoping for four port, but that seems unlikely.
08-01-07, 12:18 PM
#18
PercentSevenC, you don't know your Hitachis very well. That's a '79-'80 Nikki. A right hand drive model from the looks of it.
You don't know your differences from '85 to '86 very well either.
It's an FC engine, 12A manifold (probably the better '79-'80 style), 2nd gen to 1st gen manifold adaptor.
EpitrochoidalPower!, you need to complete your beehive removal project. There is no need for that extra coolant tube routed across the engine. Just block it off at the firewall and at the T on the engine. If you don't understand what I'm talking about, just leave it alone.
for everyone else, IT'S A SECOND GEN ENGINE! You need to notice that the tops of the rotor housings look a little different fron any 1st gen or older 13B. Just a little education for you.
EpitrochoidalPower!, I'm glad that it's a 4 port engine. One thing to consider is the reversion problem if you remove too much material from the adaptor plate. It's best to leave it a mm or two smaller than the engine port. I saw Carl around earlier today. If he sees this thread and feels like adding to it, I'm sure he'll clarify the whole reversion thing for you. For now, just try to keep the runners smaller than the port inlets. Your engine will thank you.
You don't know your differences from '85 to '86 very well either.
It's an FC engine, 12A manifold (probably the better '79-'80 style), 2nd gen to 1st gen manifold adaptor.EpitrochoidalPower!, you need to complete your beehive removal project. There is no need for that extra coolant tube routed across the engine. Just block it off at the firewall and at the T on the engine. If you don't understand what I'm talking about, just leave it alone.
for everyone else, IT'S A SECOND GEN ENGINE! You need to notice that the tops of the rotor housings look a little different fron any 1st gen or older 13B. Just a little education for you.
EpitrochoidalPower!, I'm glad that it's a 4 port engine. One thing to consider is the reversion problem if you remove too much material from the adaptor plate. It's best to leave it a mm or two smaller than the engine port. I saw Carl around earlier today. If he sees this thread and feels like adding to it, I'm sure he'll clarify the whole reversion thing for you. For now, just try to keep the runners smaller than the port inlets. Your engine will thank you.
08-01-07, 12:37 PM
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Thanks for the info, i dont intend to remove anything from adapter plate, but the intake manifold matches very poorly with the adapter, i want to match at those spots, i intend on getting a new manifold when i get a new carb, but at the moment i want to make it run like a new car, rather spend my money on dampers, brake pads, suspension bushings, want to service the diff, its whining a bit. I want it reliable as its an everyday drive, once thats all sorted im going to start work on getting some serious power. Oh, and want to get current carb tuned as its running a bit rich, is the '79-80' nikki any good?
Thanks again guys for the help
Thanks again guys for the help
08-01-07, 01:07 PM
#20
The manifold is something that confuses lots of people. They came stock with short intermediate (middle/primary) ports and yet the engine had tall port inlets. Why? It's a backwards compatability issue dating back to the '70s and a reverse runner manifold (primaries flowed into end plates and secondaries flowed into intermediate plate - good for low end but less spectacular at higher RPM).
Anyway the port mismatch doesn't hurt anything because it's flowing from a small volume to a large one, and it prevents (or atleast reduces) reversion pretty well.
You don't necessarily want to remove any material from the intermediate runners here because it will screw up your idle and give you a big headache every time you drive it. Basically it will run worse than it does now. There is a curve that must be maintained and removing material there to 'port match' it to the engine, or in your case the adaptor, will screw things up pretty badly.
If you had access to a flow bench and a little experience making educated guesses about air flow, then you could fill in the dead spots and reshape the curve to increase CFM, but without any of that, you're better off leaving it alone. Seriously. I've never touched that part of a manifold and have always had good strong idles and great throttle response on my engines. Granted I've never tried to use a Nikki on a 2nd gen engine.
But I did get to experience a Nikki on a 6 port J-spec RE-EGI engine out of a Luce (it's the small port version of the GSL-SE engine). It was a slow dog in my friend's REPU. Of course his exhaust is a pile of crap too with a cast iron manifold flowing into a 3" system. Bunch of garbage. He'd do better with an RB header flowing into a 2" system.
Where was I? Oh yeah. The '79-'80 Nikki is no good. It has a rich idle circuit for the thermal reactor. Also the fuel curve is harder to correct according to Paul Yaw or Sterling. Find yourself an '81-'85 Nikki and do the cool mods to it like upping the primary (only) jet size, switching to mechanical secondaries, and my favorite: increasing the accel pump shot. I did my first one in late '04 and it was a blast. The end result wound up on my 12A 1st gen with a mild port job. It needs slightly bigger primary jets (hehe) but everything else is excellent. The '81-'85 Nikki can be reworked to flow plenty for that 2nd gen engine of yours. T2 engines, like yours, had smallish primaries and largish secondaries. I don't see why it wouldn't work well on it. The only hurdle is the adaptor.
Hmm, Carl messed with a 13B manifold on a 12A engine. It's the same idea in reverse. Ask him for some pointers.
Anyway the port mismatch doesn't hurt anything because it's flowing from a small volume to a large one, and it prevents (or atleast reduces) reversion pretty well.
You don't necessarily want to remove any material from the intermediate runners here because it will screw up your idle and give you a big headache every time you drive it. Basically it will run worse than it does now. There is a curve that must be maintained and removing material there to 'port match' it to the engine, or in your case the adaptor, will screw things up pretty badly.
If you had access to a flow bench and a little experience making educated guesses about air flow, then you could fill in the dead spots and reshape the curve to increase CFM, but without any of that, you're better off leaving it alone. Seriously. I've never touched that part of a manifold and have always had good strong idles and great throttle response on my engines. Granted I've never tried to use a Nikki on a 2nd gen engine.
But I did get to experience a Nikki on a 6 port J-spec RE-EGI engine out of a Luce (it's the small port version of the GSL-SE engine). It was a slow dog in my friend's REPU. Of course his exhaust is a pile of crap too with a cast iron manifold flowing into a 3" system. Bunch of garbage. He'd do better with an RB header flowing into a 2" system.Where was I? Oh yeah. The '79-'80 Nikki is no good. It has a rich idle circuit for the thermal reactor. Also the fuel curve is harder to correct according to Paul Yaw or Sterling. Find yourself an '81-'85 Nikki and do the cool mods to it like upping the primary (only) jet size, switching to mechanical secondaries, and my favorite: increasing the accel pump shot. I did my first one in late '04 and it was a blast. The end result wound up on my 12A 1st gen with a mild port job. It needs slightly bigger primary jets (hehe) but everything else is excellent. The '81-'85 Nikki can be reworked to flow plenty for that 2nd gen engine of yours. T2 engines, like yours, had smallish primaries and largish secondaries. I don't see why it wouldn't work well on it. The only hurdle is the adaptor.
Hmm, Carl messed with a 13B manifold on a 12A engine. It's the same idea in reverse. Ask him for some pointers.
08-02-07, 12:49 AM
#22
You are technically correct; the best kind of correct. However you need to look again. He already stated he has a 4 port! So it's not an FC NA nor a GSL-SE anyway. Good for general info, but it's not what his engine is.
It's a T2 engine with a 12A carby. Hurray!
Good for general info, but it's not what his engine is.It's a T2 engine with a 12A carby. Hurray!
08-02-07, 01:19 AM
#25
Oh, good you got the reference.
For anyone that would like to see the differences in 1st and 2nd gen rotor housings side by side, check out this mockup.
One forum buck to anyone who can correctly identify which is the 2nd gen, and which the old school rotor housing. Two forum bucks to the first person who can tell me which rotor housing the side plates are compatible with. Ooh, a toughy.
For anyone that would like to see the differences in 1st and 2nd gen rotor housings side by side, check out this mockup.
One forum buck to anyone who can correctly identify which is the 2nd gen, and which the old school rotor housing. Two forum bucks to the first person who can tell me which rotor housing the side plates are compatible with. Ooh, a toughy.