Originally Posted by heretic' post='787720' date='Dec 18 2005, 08:25 AM

https://www.mazdatrix.com/sccaportrule.htm



I'm not much up on my circuit racing, but apparently the old definition of a street port was "the port window must be only one hole" or "the circumference of the port must be contiguous". There was a great thread on here referring to some of these porting types, such as the comb port, or making a bridge port most of the way and supporting the tab with a post or two, to try to get the advantages of a bridge port while meeting the letter of the rules. Unfortunately, I believe this post was lost when the forum was hacked a ways back. Of course, the rules have now been changed to something with no loophole.



{quote]"So it seems obvious that the open line would be moved to that location that is just legal, as the first part of the porting program. In an artical he wrote, Lemon said he had trouble getting used to shifting his E car at 10,000 RPM."

http://www.rx7club.com/showthread.ph...01#post1586101 might be the "article" in question.

Originally Posted by heretic' post='787720' date='Dec 18 2005, 11:25 AM

https://www.mazdatrix.com/sccaportrule.htm



<snip>



http://www.rx7club.com/showthread.ph...01#post1586101 might be the "article" in question.

Originally Posted by Don1' post='787700' date='Dec 18 2005, 06:52 AM

Thanks a lot, guys. So far, you have given me some serious things to consider.



Banzaitoyota said, "I would contact Carlos at CLR in Miami. Beveled Rotors and a balanced rotating assembly will help your cause."

====> Thanks, banzaitoyota. I don't know what beveled rotors are, but, I will try to find out and definitely have everything balanced.



---------------------------------------------------------------------------------------

Lynn said,



"I looked up the "Street Port Rule" and pictures for both 6 port and 4 port, street ports, and that gives you some help right away. Those pictures were supplied to SCCA by Dave Lemon of Mazda Trix. A reasonably successful (GREAT) engine builder. They seem to be all worried about the open line being moved so far as to expose the junction of the leading end of the side seal and corner seal to the intake port."

=====> I have tried to find the "Street Port Rule" in the GCR and could not. Could you point me in the right direction, please? I thought street porting meant pretty much anything goes except adding more holes for the intake.



Lemon wrote them a rule that disallows any air from entering from outside the track of the corner seal side seal junction. An air tight rule you might say. On the SCCA web site under rules, type street port into the search box. Or paste this link in your search engine.

http://www.scca.org/Club/Index.asp?IdS=015...=030|057|010&~=



The bottom choce is the street port rule with good pictures for both 6 port and 4 port irons.





"So it seems obvious that the open line would be moved to that location that is just legal, as the first part of the porting program. In an artical he wrote, Lemon said he had trouble getting used to shifting his E car at 10,000 RPM."

=====> Where may I find such articles, Lynn?



Go to the Mazda Trix web page to read about their race car. The link in the next post is also the "rule" but the pictures are not working tonight.



"So, I'm thinking that he could be using the 6 port irons at least on the ends. I think the 12A center irons have better looking runners and ports."

======> OK, so I need a 12A center iron. Are they all the same, or, is there a preferred one to use?

If it turns out that you need the big 12A center ports, I will dig up the P/N for you. One look and you will know.



That would be total speculaton on my part. The 6 ports I have seen came with relatively small runners and ports in the primary iron (center iron). If you call Dave or any of the guys at Mazda Trix they will advise on what makes power and what does not.



"I notice that only the 12A is listed on the Mazda Trix web page for CSR."



=====> The reasons I am trying to avoid the 12A are because I am not sure if they have the proper front motor mounts and I think the narrower rotor housings might make my present intake and exhaust unusable.



Exhaust headers are easy. The early 12As came with 4 studs on the front cover. That cover is often used on other engines to get the 4 studs for mounting. Is that what you have? There are also cnter irons with mound pads but I am unsure of what motor that is.



"I have two Drummond GT-3 12As, and have been very happy with his service."

=====> I have not heard a bad word about Daryl Drummond from anyone.



"We need about 265HP to be competitive, (in GT-3) with about 250 in hand."

=====> I, too, need 265HP. I now have 190 at the rear wheels : ^(



"The less obvious requirement is for minimum rotational weight. The 5 1/4" or smaller 4 1/2" Tilton style clutch. The Mazda comp spider ring gear and flywheel, or a cut down Tilton Chevy wheel and an old RX-2/3 flexplate. Minimal preload on the transaxle side plates, and pinion preload. The cat **** thin diff/trans lubricant."

=====> I'm very interested in getting the best clutch and related parts. I use the clutch only to get the car moving in first gear. I have never used anything other that standard street clutch and flywheels, so, I have no background here but think the proper choices are critical. I'm not so sure of using the cat **** thin oil, though.



"I would try the bleed valves for the wheels so you are at ideal tire pressures all around from the green, and not waiting a lap for the tires to come up to race pressures."

=====> I have never heard a positive reference to these valves before. Have you used them yourself? Hoosier tells me to not run my tires under 18psi. I go on the track usually with about 14psi and must heat the tires quickly. In the interest of not having a tire fail, I error on the side of slightly higher pressures than optimal. After a national race I usually find that I am carrying about two psi more than optimal. I should probably try those things and see for myself.



The circle track people use them all of the time. At Mid Ohio we start with L/F at 15 and all others at 16, looking for 24 in the fronts and 22 in the rears. The first lap is exciting. I have not looked at the Hoosier formula tires, but the size we run, 15X9.5" are heavy as sin. We run them because there is a Hoosier sponsored car and he gives us the tires. We are not fast enough to worry about it. But you should weigh a Hoosier and an Avon and a Goodyear to see if the Hoosier is a big disadvantage.



"You can give up a little sticky for a light tire and get it all back down the first long straight."

=====> Not in CSR. We pull well over 2 g's in corners and easily over 150 mph on straights such as Watkins Glen and Summit Point. To give up a tad of stick in the corners is to add serious time to lap times that cannot be made up on the straights, imo.



Have you ever found yourself behind a car that would hold you up in the turns, and he would pull away down the straights, and hold you up again at the very next turn? Was he ahead of you because he cornered well, or because he went down the straightaway well?



Two identical cars, with identical HP, one with light rims and tires, and a light flywheel and clutch assembly

and the other without. The outcome? A poor driver is going to be in the car with the lighter parts. You are in the "heavy" car. It will appear that even though you drove one hell of a race, you were down on power, and the trainee in his fist National race waxed your but.



The reverse magic of rotational weight is this. The car weights can be exactly the same. Yet the performance will suggest that one of the cars appears way down on power. The most obvious problem is the flywheel/clutch assembly. The energy expended accelerating this mass is unrecoverable. You don't get it back on the upshift. If you upshift without lifting slightly, you can break a part. Also the excess energy in the flywheel just appears as heat in the driveline, and drive tires. If you lift slightly to get the dog speed closer to the gear speed, (as you should) then the excess energy is expended on internal engine drag.



And you do it on every shift. The energy expended doing this is subtracted from the energy available to accelerate the car. Adding less driveline weight is adding the lowest cost HP you can buy. The "airplane people say add more lightness". And it stays in the car all of the time.



Your first laps with a light flywheel will have you on the rev limiter a bunch. You will think the limiter is hosed until you catch a look at the tach, and it IS on the limiter. You will be shifting late everywhere. Your lines will be hosed. Your breaking points will be hosed. It will be great. I will try to find the clutch and flywheel stuff on the Mazda Comp page. Call Mazda Trix and ask all of the questions about what parts to use.



"Not only do heavy tires look like heavy flywheels to the engine, they look like a heavy car to the brakes."

=====> Agreed.



"Read all of Carroll Smiths books. Read "Driving in competition" by Johnson."

=====> All of the Smith books travel to each race.



"And about one thousand other things I cannot think of at the moment."

=====> A thousand other things, huh? Please, continue.

Originally Posted by heretic' post='787513' date='Dec 17 2005, 07:47 AM

"Engines may not have a plenum common to multiple cylinders or rotors". This simple sentence would express the intent of the rules very cleanly and concisely.

Originally Posted by Lynn E. Hanover' post='787947' date='Dec 19 2005, 12:57 AM

Lynn E. Hanover

Originally Posted by 13BTNOS' post='788010' date='Dec 19 2005, 11:17 AM

This is what's meant by beveled rotor. It's a way around the rules and gives you more port timing comparitive to a bridgeport but without the bridges.

Originally Posted by Don1' post='788060' date='Dec 19 2005, 01:13 PM

WOW! Thanks, 13BTNOS. I never would have thought of that. Now I am trying to figure how you know where to cut how much....

Originally Posted by Don1' post='788056' date='Dec 19 2005, 10:09 AM

Thanks, Lynn. Excellent stuff. I am convinced that the clutch and flywheel need to be the lighest I can find. I will check the center iron as soon as I can get the flywheel nut off. Do you have any feeling about the beveled rotor (I am very intrigued)?