rgordon1979

iTrader: (3)

For those of you that have street ported a s4 TII, I have a question. I, well....we (Zach McAfee) and myself are in the process of porting my 88 TII. I have attached a picture of our process so far. Since neither of us have ported a Turbo before, we were wondering if anyone could tell us if we have much more room before hitting the water jacket. I would like to angle it a little more, but wanted someone else's opinion.

Secondary Port1

Secondary Port Pic #2

capsoval

I am not touching that one with a 10 ft. pole.

rotarygod

iTrader: (1)

Its pretty hard to tell from the pictures. I see you only went up on the ports (close them later). I also opened mine a bit earlier. If you feel around the back of the port in the coolant passages you can tell how far you can go. You can also scratch the inside of the port with your finger nail and 'listen' at the thickness. The sound changes the thinner you go. I also spent alot of time on the inside radius (opening side) of the port. This is just a sharp edge stock but I gently radiused mine in. Its a little hard to describe without actually showing you but if you stare at it you'll see what I mean. I'm afraid to tell you yes you can go farther because I don't want to be responsible if you hit the water jacket. Mine are more or less based off of the Racing Beat 4 port template closing and opening timings. I change them slightly but they are close.

rgordon1979

iTrader: (3)

Yeah, I was surprised to see that the street port from mazdatrix only goes up on the port. I may open the bottom edges up a little bit to make it open earlier. thanks for the help rotarygod.

rotarygod

iTrader: (1)

Actually the Mazdatrix template does open the ports earlier as well. The opening side is not the bottom of the port but rather the long, straight side (the left side in your pictures). There is no point to going downward on the secondary ports. This part of the port is so small and skinny that there isn't much flow through that part anyways. The T-II port actually goes down farther than the Madatrix/Racing Beat template does anyways. I go down on the primary ports even with level of the bottom of the intake runner itself and actually just a tad lower since I kind of give a slight rounded profile to the back of the port to aid in airflow. My primaries and secondaries all open and close at the same time which they do not do stock. On a stock motor the primaries open AFTER the secondaries. If you still have a stock turbo it will spool extremely fast assuming you also did the exhaust ports. The downside with the stock turbo is that you may as well shift gears at 5500 rpms since the turbo can't flow enough to make good top end power. A boost controller and some wastegate porting will help this a little.

rgordon1979

iTrader: (3)

i think i will leave the opening and oposing side alone... I think I am just going to follow the m.trix/r.b. template for the primary port. As far as exhaust goes, I am not going to do anything major. I think I may take the bottom of the exhaust port down by about 2-2.5 mm. This is what i gathered from judge ito on nopistons.com. For the wastegate porting, you can only open the wastegate a minimal amount before the flapper will actually be smaller than the wastegate. B/c of this, most of the porting is done inside the wastegate opening?

rotarygod

iTrader: (1)

Some people actually port the wastegate opening bigger than the flapper door! Up to 20% bigger! Sounds a little strange but the factory turbo is so small (for a rotary) that a little pressure being bled off doesn't make that much of a performance difference on the low end but helps a great bit on the top end where we like to stay at anyways. I use custom machined exhaust sleeves but when I did use the stock ones I actually just ported the exhaust port out to match the size of the factory sleeve. Even with the exhaust closing later and the intake opening earlier I could still pass Texas emissions with flying colors. On an n/a, exhaust port timing is more critical because of header length, desired power band, intake manifolds, etc. On a turbo engine a bigger, higher flowing exhaust port works best. turbostreetfighter (Marcus) and riceracing use exhaust ports as big as they can get them. Marcus said that he had better results with exhaust ports on turbo cars (he builds alot of them) when they were ported larger. My philosophy is a little different for street applications where I try to maximize port velocity to spool the turbo as fast as I can. The downside is that after a certain point I hit a brick wall in power where I can't easily go any higher without a larger port. There are many different styles out there depending on who does it. Everyone will tell you different. On a turbo engine I just make everything as large as I can. On an n/a I base my ports on the required conditions. Almost anything you do will work much better than stock so I don't think you'll be disappointed with anything you try.

Zach McAfee

The template we have doesn't open earlier.

Has anyone ever JB welded the back side and ported it straight down with any luck? I know the NA guys do it all the time. The only concerns are a) will the JB weld break off and b) will it create a hot spot on the face of the housing.

Zach McAfee

I'm designing an NA port so I thought I might sneek this question in.

Is this something you should shoot for when designing your own ports? In other words, is there an advantage to having the same timing for primary and secondary, or is that just the way yours worked out?

rotarygod

iTrader: (1)

Kind of strange on the template since mine does open earlier. Mine is a Mazdatrix one although I don't use it anymore. On my turbo engine I do have epoxy on the backside of the port in the runner itself. I did this to slightly lessen the sharp turn at the back of the port. My 6 port n/a does not have this (I think I forgot to do it!). If you use JB Weld it WILL fail!!! Don't use that crap on anything. I use Devcon plastic steel epoxy. Looks similar but works much better. Make sure the port is very clean and rough it up first.

As far as my ports opening at the same time, I did this to both my turbo 4 port and my soon to be turbo n/a 6 port. Mazda's goal was to increase low end power and gas mileage. Since the standard 3 blade tb is used they could get away with this. At part throttle the primary throttle blade is the only one open and even then it is only very slightly open. Since no air is flowing through the secondary ports their timing effect doesn't do much at this stage. Since the primary ports are the only ones flowing air they open them later which decreases functional port overlap and promotes better emissions and economy. Once you hit about 15-20% throttle all the blades are open and there is no longer a benefit to it. I like mine opening all at the same time as early as I can get them. I want all the maximum amount of time available to get all the air in that I can. My GSL-SE 6 port is streetported and ran high 14's with the stock restrictive intake manifold and a big streetport. Power fell off at 7000 rpm due to the small manifold. It still passed Texas emissions and is very streetable. I like it better on the street than stock. The new intake manifold is a S5 manifold that has been modified to accept a Mustang throttlebody. The car now pulls up PAST 8000 rpm with ease! My port is an example of how a port can be too big with certain manifolds. Smaller ports would have been better for the SE. Obviously since all of my ports can get air at the same time I want them all to open earlier. Paul Yaw once told me that when he does Turbo engines he closes the port late as on the template and opens the primary at the same time as the secondary. However he leaves the secondary opening alone so as not to increase overlap duration. This is where I differ. I open these earlier too. To make a very overly complex response short, open them all at the same time. You won't see any downsides to it.

banzaitoyota

i'll post pics of my 87 TII wastegate 2nite, its huge!!!

RETed

Ask this question to 100 people, and you're most likely going to get 100 different answers.

I can only give you my opinion - well, you asked.

I do not like to extend the opening side at all.&nbsp Overlap kills low end power, and I haven't seen any positive results from having any overlap at any RPM.&nbsp I've been in many debates on the advantages of overlap in a rotary motor, and bottom line (to me) is that the rotary engine dynamics doesn't take advantage of overlap as a (crossflow head) piston engine, period.

The only exception is to port the primary ports with the same port opening timing as the secondary ports.&nbsp I do this for all-out motors in my Stage II port jobs.&nbsp This does not noticably degrades idle in all practical sense.&nbsp The Kouki 13BT engine runs 10-degree later port opening than a Zenki 13BT!&nbsp The difference in intake port timing from primary to secondary is around 10-degrees already!

With the idea to minimize overlap, this means porting "down" is a no-no in my book also.

Porting "in" encroaches on the oil control ring seal travel path, and doing so will cause excessive blow-by.&nbsp I've seen this for myself!&nbsp No, it wasn't my engine.

This leaves porting "upward" the only option.&nbsp Via the Mazdatrix pics on their FAQ section, you get a pretty good idea of how much metal you've got back there - on a 13BT, there isn't much. Without some kinda major water passage bloack filling, there really isn't too much you can do - be careful now, as there is such thing as "too big" an intake port, unless we're talking race motors.&nbsp Minimal metal removal will produce noticable power increases - keep that in mind.&nbsp I've got picstues on my port work, but they are kinda crappy, so I refuse to post them.&nbsp I think I posted one pic of a rough job on the primary port somewhere else in here - it looks similar to what you're doing.&nbsp (Sorry, my vision kinda sux, and those pics were kinda small, but they look close to what I normally would do with a port.)

I've been also toying with the idea of backfilling the entire water jacket and "going to town" on the primary port - I just don't have the funds to do such an experiment right now.&nbsp Summit Racing sells "block filler" for pretty cheap, so that would be a starting point - I wouldn't trust JB Weld in my engines.



-Ted

banzaitoyota

Here is the pics of my wastegate porting as promised

rgordon1979

iTrader: (3)

thanks for the help everyone. It was very useful over the weekend. We took a little more out of the intake and polished it up real nice. On the exhaust we took it down about 2-2.5 mm. Like I said this is my first time rebuilding and Zach's first time doing a turbo so we are hesitant to do too much experimenting...also I am probably going to be using this as a daily driver so I don't want to take it too far. Only have to get the new bearings pressed into the rotors and it will be ready to go back together.

I looked at your pic banzaitoyota, is the wastegate bigger than the flapper door? That is what it looks like in the picture. I guess you could oval the wastegate to keep it from getting stuck. Do you have any problems with boost creep with that port size?

Exhaust Port

banzaitoyota

Yes the wastegate is ~25%>door opening,

rgordon1979

iTrader: (3)

any creep?

banzaitoyota

don't know yet, engine is still on the stand

rgordon1979

iTrader: (3)

ah, so it can be a race to the finish...

banzaitoyota

Yes it Can!!!!

banzaitoyota

Is this big enough TEd?

RETed

Looking good!



-Ted