lonetlan

HEY! the picture of the 2 ports(front iron) is HUGE! Sorry.

Lynn E. Hanover

Not to worry. Read this: https://www.nopistons.com/forums/top...iming-degrees/



This is about building a device to find Top Dead Center (TDC)with great accuracy. It requires the purchase of a very big degree wheel. And an understanding of some rotary basics.



Rotaries are 4 stroke Otto cycle engines. The piston engine (also an Otto cycle engine) has the same EVENTS as the rotary. So you will see intake (valve) opening point or, event. Intake (valve) closing point or EVENT.



Same for exhaust. These events in a piston engine say their names. Top Dead Center is the piston at the top of the bore, or cylinder. Bottom Dead Center (BDC) is the piston at the bottom of the bore, or cylinder.



In the piston engine these two important events are easy to find.



In the rotary a bit more difficult. There are two TDCs and two BDCs. And they are in 4 places.



One easy way to remember this that TDC is also minimum volume at the rotor face. BDC is found where there is maximum volume in front of the rotor face. So there is a TDC where the rotor face stradles the plugs, and on the opposite side of the housing where minimum volume has you at TDC during overlap. Just like a piston engine.



Port timing is called out from the nearest event, and we pretend that there is only one rotor face. Once the light bulb goes on in your head, the rotary is less complex than the 4 stroke piston engine. A 2 stroke piston engine does everything in one revolution 360 degrees.



A 4 stroke piston engine requires 720 degrees or two complete revolutions. A rotary requires 1080 degrees or three complete revolutions.



So we ignore all of that and call out events from the nearest TDC or BDC, simple.



So intake ports are said to have closed at some number of degrees after BDC. The big maximum volume at the top of the housing is BDC and a stock side port intake might close at 50 or 60 degrees ABDC (After Bottom Dead Center).



The side of the rotor opens and closes the intake ports. The apex seals open and close the intake port in a periphery port engine.



So you build the rig to find TDC. Then you use the pointer and degree wheel to lay out various

EVENTS copied from Nopistons, or other sources. Use Magic marker to stain the iron and scribe with a dull nail to protect the iron.



Lay down duct tape in 4 layers around the port. The die grinder will hop out of the hole from time to time and try to ruin the iron. Wear eye protection and a mask. Set up a fan to keep air moving across your work and keep the chips off of you.



Piece of cake.



Lynn E. Hanover



The picture is one of my very large "J" bridgeports in a 12-A iron. Closes at 85 degrees ABDC.

Lynn E. Hanover

Here is a picture of the rotor at TDC firing and the degree wheel and pointer showing TDC.



For easy understanding, we ignore the full 1180 degrees of rotation required for a full cycle, and just report the open and close events to the nearest TDC or BDC. We use any rotor face that is close to the event we are interested in.



So all of the porting data can be recovered in one 360 degree rotation of the crank.



Piece of cake.



Lynn E. Hanover

Lynn E. Hanover

Here is a list of Events I first saw on Paul Yaw's web site.



Lynn E. Hanover



Port timing basics by Paul Yaw

InboxX



Reply |Lehanover@aol.com to me

show details Jul 18 (6 days ago)







Port Timing

IO = Intake opens

IC = Intake closes

EO = Exhaust opens

EC = Exhaust closes



US Model First Generation RX-7

IO 32° ATDC

IC 40° ABDC

EO 75° BBDC

EC 38° ATDC



European Model First Generation RX-7

IO 32° ATDC

IC 50° ABDC

EO 75° BBDC

EC 48° ATDC



First and Second Generation 6-Port 13B

Primary intake (Part throttle/cruise)

IO 32° ATDC

IC 40° ABDC

Secondary intake (Part to full throttle)

IO 32° ATDC

IC 30° ABDC

Auxiliary high speed ports (Full throttle above approximately 4000 rpm)

IO 45° ATDC

IC 70° ABDC

EO 71° BBDC

EC 48° ATDC



Second and Third Generation Turbo 13B

IO 32° ATDC

IC 50° ABDC

EO 71° BBDC

EC 48° ATDC



Racing Beat "Street Port"

IO 25° ATDC

IC 60° ABDC

EO 84° BBDC

EC 48° ATDC



Racing Beat "J-Bridge Port"

IO 115° BTDC

IC 72° ABDC

EO 88° BBDC

EC 57° ATDC



Mazda Factory Peripheral Port

IO 86° BTDC

IC 75° ABDC

EO 73° BBDC

EC 65° ATDC

Mazdanowski

Lynn if you are not at the flight line in Oshkosh for the fly in you should be. FYI I did like the reminder to clean up the opening on the intake in case you ever turned the motor backwards while working on it. You wouldn't want to have the side seal drop and catch.



I had a couple relevant questions that that maybe other people have interest in. For a frame of reference, do you know at what degree ATDC your intake ports would be opening if you ported right up to the lead of the side seal in our SB, C or D?



How about the Renesis?



If we are not Pro builders but would like an accurate degree wheel does anyone know what we have for choices today? Price and source?



I know most guys have their intake ports opening around 22 to 25 degrees ATDB. I do read about a couple builders that uncover the lead of the side seal and with scissoring and beveling say they last. But that is only a couple guys compared to how many at 25 degrees. Has any average Joe build a motor with an uncovered opening side seal and had it last?



Thanks

Lynn E. Hanover

I use a Mr. Gasket part number 6120. Its 11" in diameter and that is the smallest diameter I would try to use. The bigger the better.



http://www.amazon.com/Mr-Gasket-6120.../dp/B000BW8W2K This one is $41.27 right now.



Jegs has a Moroso part number 62191 18" diameter for $45.99 right now.



http://www.jegs.com/i/Moroso/710/621...Fdw55QodDHXmaA



I have never tried to do a street port, so I have not experimanted on opening events for one.



I would not unsupport the leading end of the side seal in any case. Even with a proper ramp to pick it up at the closing line, there will be some rounding of the corner, and eventually you will get lower compression and hot start problems. The trailing end of the seal can be allowed to droop into the port. If you do this, you must extend the closing of the port to start on the inside and finish on the open line. The open line must be moved out to prevent the end of the drooping seal from touching the side of the port. This takes you close to the track of the leading end of the seal. I do this and can get 2 seasons out of a set of seals. The radius at the very bottom of the port must be bigger to account for the drooping seal end should you turn the engine backwards. The open at 25 degrees ATDC seems to be the standard street port number.



The other problem with drooping the leading end is that you are down to 50% of the corner seal being supported. Pictures of the tracks and ramp diagrams in the porting section.



I have never ported a Renesis. Sorry.



Lynn E. Hanover

diabolical1

Lonetlan, sorry i don't log in here as often as i would like to, so i missed this. i know (from the other side) that you're making forward strides, but over here you get the insights of Mr. Hanover, which are always a treat to me.

lonetlan

Don't worry about it. I update both threads almost at the sametime. I slowed down a bit because I'm waiting on some "retired" irons and housings so I can really get this down before I start on new housings and pretty new irons. I'm trying to make my new engine last as long as it did(180,xxx+). I don't want to do all this work and fail.