Whats makes a street port mild, aggresive, extended etc?
 

I'm In the midst of having my 13BT rebuilt and street ported using what I believe are Racing Beat Street Port Templetes. What would this fall under and why?

Details would be great.

Extend port and street port are pretty much synonymous... the port timing is extended later, you can't go much earlier on the intake timing without causing the corner seals to insufficiently supported. The way you make the intake open earlier is with a bridge port (bridge of metal holds corner seal and apex seal from falling out) and this is generally not "recommended" for "street" use. (Using the everyman's definition of "streetable" here)

How "aggressive" a port is is subjective, it's just a loose measure of where the port timing is vs. where stock was.

So with the extended port, this Is classified as "mild" or "agressive"?

Thanks for the reply btw.

I've always thought extended to be aggressive with a big port and late closing. It's subjective . . but once you start porting a plate you will get the idea of where "mild", "medium", and "large" ports are as far as enlargement of the stock port. "Large" is about as big as the boundaries will let you go, meaning to the limit of the corner seal track, port runner bottom and water jacket.

anything smaller than the biggest street port you can make, is in my opinion a waste of time and money. make it as big as possible on the intake. use your pinky (little) finger to reach in and feel how much metal wall you have left to grind. leave the wall about 2mm thick. i am talking about the top of the port. you have to go past the template from racing beat to have the maximum port size. you should put something around the port to protect the side plates from being damaged when you slip using the grinder. i use duct tape and thin flexible rubber, or you could cut a hole in a mouse pad and use it. protect all the metal around the port you don't want to grind.
the inside top of the port is the last place to close on the port. your enging timing stock is: intake opens at 32degrees atdc , closes at 50 degrees abdc. Racing beat steetport template timing is:intake opens at 25 degrees atdc and closes at 60 degrees abdc. a racing beat bridge port closes at 72 degrees abdc <---------------this indicates how much further you can go with the closing of the steet port because a bridge and a street port still close in the same area of the port.

A street port can be mild or aggressive, depending on how it's been done.

I agree that there is no such thing as a too-big street port, although I personally don't see much merit in porting the runners themselves. (WHY? I mean, the intake port runners are smaller, so porting the runners just means you are increasing volume without increasing flow, meaning killed low end with no benefit)

i agree with the runner statement.

So what would the RB streetport templates be classified as?

The RB port IMO is about more of a medium port. I mean i have seen some really small ports and then there are some huge ones. The RB ones have a pretty good closed time but they can go taller. the RB street prto timing is about:

IO 25° ATDC
IC 60° ABDC
EO 84° BBDC
EC 48° ATDC

CJG

I have seen 70deg closing time classified as "REALLY HUGE".

Just as long as you're not hitting water jacket, you're not too large. :D

If only i had a good digital camera i could post some pics of some pretty big ones that i have. They are almost as large as you can go. I think mabe i can get about nother 1/8 in or so but thats about it.

CJG

So Racing Beats Street Port Templates would be classified as non Big street port.:(
http://www.racingbeat.com/photos/22202.jpg

The Racing Beat T-II template I would personally classify as a "mild port" even though you can port less. The T-II template does not open the port any earlier. It just closes them later. The older 4 port templates (pre-RX7 13B) open them earlier and close them later. This is what I would classify as an "extend port". It is a very subjective question depending on who you ask. The older template can be used on the T-II housings but only on the outer ports due to their size. You could base the primary ports off of their timing though just not their size downward. You can get too big of a port and not just by hitting the water jacket. If you have a stock ecu and stock turbos, etc. then you don't want a huge port. The turbo can not flow enough for it. It can't really keep up with the stock port requirements. In this case just clean up their shape a little for flow and maybe open them up just a tad. If you have a standalone ecu and a nice big aftermarket turbo then you can get really big. There was a guy in the club near me (nameless) a few years ago who bragged about his big streetport yet everything else was stock. My friend Chad's T-II with stock turbo and stock porting walked all over him at 14 psi (upgraded fuel system) and the guy was running 14 also. If you still have the stock turbo or even a compressor wheel upgrade then don't go any larger than the RB template. If you've already replaced this stuff then go ahead and have fun. Remember that everything has to be designed to work together. A huge port will give you poor lowend and the stock turbo can't flow enough for good top end so the large port becomes a waste of time.

hmmm what about kevin landers "large street port"?

A wise man told me, that big insn't neccesarily better - smooth airflow is.

What if you had the manifold/carb to match? I would think that would help immensley. The manifold runners tend to be very restrictive. And Im not talking of hogging it out. Just matching for flow capabilities.

Well here's my theory.

If it doesn't need that much runner area for a given HP level, then opening it up only makes it worse.

Someone whose name seems to have become a swear word has bade 190hp with a street exhaust with a 12A manifold with the stock manifold port sizes, and you *know* those are quite a bit smaller than the engine's runners.

This is why my way of thinking is to not open up the intake manifold, but to close up the engine's port runners. Still leave them larger than the intake manifold, for a nice step out, but still smaller than stock.

Yes but were the manifold runners stock size or ported? There had to be some rework there due to the overly restrictive runners.

Now on the primaries I'd have to agree (and weve had this agreement b4) that they be closed up to the proper size. But on the secondaries, Id disagree.

But what then is the true benefit of porting (airflow wise)? A big port that flows more when wide open (which then properly sized intake runner and passages would be the key), or simply the extra duration gained from porting (which then flow matched runners and such wont matter as much)?

hey tony i made a mistake it wasn't racing beat templates it was templates that ivan had made back in the day when he used to race rotory's with sum modification. trus me the port is big very BIG! u will be very pleased with it. i don't think u could go much bigger

Where can "large" streetport templates be bought? I don't want a BP or PP, but want a large SP. Thanks.

you don't need a big template. you just use your eye and feel for the port inside the water jacket area.
just buy the RB template and go bigger. some housings have more material to remove than others,not much but some. always go with a big port that flows more especially with a turbo. i have tried the extra duration without the big port and it is not near the hp of the big open port with the extra duration.

i have also ported the primary and secondaries on the stock intake manifold with improvement all the way around. i made the intake runners match the runners in the side housings. with an INCREASE in low end power. i have never increased the size of the runners in the side housings it is NOT nessesary. if you look at pictures of the old manifolds like the early seventies cars and trucks you will see that the runners on the intake manifold are as big as the ones on the side housings. they matched. mazda created the restriction in the manifold for economy purposes.

Don't you hate finding out after everything Is all said and done?:D

I spoke to 20B-3Rotor and he had said the Intake Is of Racing Beat but the Exhaust Ports are considerably bigger.

Perhaps he can chime In and give me an exact description Junior.:p:

oh ok well ohwell i know they look sweet as hell and u gonna have spinnin the shiznit outa dem wheels

but i knew that thay were gonna order tha templates jus didn't know if they went ahead and did that. i guess they did but those ports are huge bro.

will spoool that turbo i giot for ya real nice what ya think/

The secondaries already are the same size as the runners in the block. Well, slightly smaller, which is what you want... you want *some* step. How much bigger do they need to be? I don't realistically see them needing to be larger because the port window is so necessarily small... in effect the port window is a choke point. Which is why you can't make it too big. :)

And why I see a benefit in making the runners *smaller*... since the large area isn't doing anything, let's get rid of it to increase velocity.

That answers my question somewhat. Now did you do this on an N/A or forced induction engine? I would imagine the requirements would be quite different. "Horses for courses" to quote Carroll Smith. And where is the hp gain? Top end, mid range.......

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i have also ported the primary and secondaries on the stock intake manifold with improvement all the way around. i made the intake runners match the runners in the side housings. with an INCREASE in low end power. i have never increased the size of the runners in the side housings it is NOT nessesary. if you look at pictures of the old manifolds like the early seventies cars and trucks you will see that the runners on the intake manifold are as big as the ones on the side housings. they matched. mazda created the restriction in the manifold for economy purposes.

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I agree the later inatke runners are very restrictive (my flowbench data supports that), but theres always a point of diminshing returns. As velocity drops so does your low end power.