timing?
04-03-17, 02:36 PM
#1
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timing?
Hey everyone I'm looking at getting a rx7 again. I haven't had one since I was in high school and I never really worked on it other than adding oil when needed. I'm getting ready to graduate college so I'm more than likely going to have to get one with a popped engine and was wondering if during the rebuild process is there a set timing that is needed? I assume it is similar to a piston engine where there is cam timing needed to get the A/F mix in and the exhaust gases out. I've been having a hard time finding information on this so if it is needed any information on how to set timing would be greatly appreciated.
04-03-17, 03:11 PM
#2
Hey everyone I'm looking at getting a rx7 again. I haven't had one since I was in high school and I never really worked on it other than adding oil when needed. I'm getting ready to graduate college so I'm more than likely going to have to get one with a popped engine and was wondering if during the rebuild process is there a set timing that is needed? I assume it is similar to a piston engine where there is cam timing needed to get the A/F mix in and the exhaust gases out. I've been having a hard time finding information on this so if it is needed any information on how to set timing would be greatly appreciated.
04-03-17, 11:28 PM
#4
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I am going to try to explain this to the best of my knowledge however I am not an expert I have not ever rebuilt an engine but I do own an fc and have read about them a lot. the rotary engine does not have a cam it does not have with lifters and intake and exhaust valves. the rotary has ports on the housing for intake and exhaust. as the rotor turns the port "opens" to intake air... basically as the rotor passes by the opening it is open to the combustion chamber and as the rotor gets past the port the port is no longer open to the combustion chamber. the intake and exhaust "timing" is controlled by the size of the ports the longer the port the longer it is open to the combustion chamber. please someone correct me if I am wrong on this but I believe the width of the port is comparable to the lift in a normal piston engine and the length of the port is comparable to duration. the only true timing I know of on a rotary is ignition timing which you have a leading and a trailing spark plug on each rotor the leading I believe is set 10 degrees ahead of the trailing on an s4 from the factory but definitely do not use that as reference. there is a really good video on youtube of "how a rotary works" that should help you out a bit.
04-04-17, 10:52 AM
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Thanks for all the info guys. I guess I should have mentioned that I'm trying to find a FC turbo ii. Also I got a decent understanding of the port system now and watched a few build videos. So as far as ignition timing what is the base setting I should start with? I believe I saw in a video that the leading plugs should be timed to like 35 degrees at cruise and like 10 degrees at boost with the trailing plugs like 10 to 15 degrees after the leading? my power goals are between 350 and 400 wheel HP and I'm not too sure if that overly ambitious or not so if it is please let me know so I can go in to this build with a realistic expectation.
Last edited by cbr600kid; 04-04-17 at 10:56 AM.
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04-05-17, 12:18 PM
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True I'm just trying to get a better understanding of how the engine itself is supposed to work. More than anything I was asking to see if when you do a rebuild if there is any special way you are supposed to index the rotor to the housing in regards to the spark plugs for timing or if there is some special way that the engine needs to be timed after a rebuild ?
04-05-17, 04:16 PM
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04-05-17, 11:00 PM
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True I'm just trying to get a better understanding of how the engine itself is supposed to work. More than anything I was asking to see if when you do a rebuild if there is any special way you are supposed to index the rotor to the housing in regards to the spark plugs for timing or if there is some special way that the engine needs to be timed after a rebuild ?
but yes, there is ways an FC and FB engine can be off time. an FD engine though is driven by a crank trigger wheel that i have not seen indexing issues with.
you can buy hub sets for the early engines that will be timed properly since the crank keyway is always at 9 o'clock exactly.
if you wind up with an engine that has never been apart, it should be indexed properly.
Last edited by RotaryEvolution; 04-05-17 at 11:04 PM.
04-07-17, 05:07 PM
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i always double check timing on the engines i build, because if it has been rebuilt before there is a high chance that the timing is not accurately indexed to the engine. i have threads on how to check this on the forum, though i think the pictures have long since died. unfortunately i am not really up for redoing the whole DIY all over again.
but yes, there is ways an FC and FB engine can be off time. an FD engine though is driven by a crank trigger wheel that i have not seen indexing issues with.
you can buy hub sets for the early engines that will be timed properly since the crank keyway is always at 9 o'clock exactly.
if you wind up with an engine that has never been apart, it should be indexed properly.
but yes, there is ways an FC and FB engine can be off time. an FD engine though is driven by a crank trigger wheel that i have not seen indexing issues with.
you can buy hub sets for the early engines that will be timed properly since the crank keyway is always at 9 o'clock exactly.
if you wind up with an engine that has never been apart, it should be indexed properly.
04-18-17, 01:24 PM
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