MIKE-P-28

iTrader: (1)

Getting ready to send my engine housings off to be ported. Im thinking of a basic streetport. What can I expect? Very noticable difference? What are the tradeoffs for porting? Should I do more?

peejay

If the porting is intelligently done, the car will make more power across the powerband - you'll be able to use 5th gear at anything over 20mph and it'll pull as high as you want.

PaulFitzwarryne

I recently obtained as much information as I could on this subject relating to the 12a engine. Quite a few people give figures based on guesswork rather than an accurate dyno.

If you have a steet port done say using Racing Beat's opening and closing figures. a modified Nikki or high performace Carb such as the Holley, free flow air filter, and a better fuel pump then output will be in the order 180-185 hp if all matches. You should notice the difference with your 1/4 time falling from 17 seconds to 15.0-15.2. In other words more like the 1988 turbo. I agree with PEEJAY that you will get increased power over the whole range, if the go to far with the porting then it will be down under 3,500.

Sticking to a Nikki or Holley has its advantages, but you could go to others such as a Webber for marginally more performance but a few disadvantages to get it.

The critical point is everything has to match if you are going to get this type of performance improvement. If you keep everything else stock, then you will also notive the difference- little increase in power and drives like pig!

MIKE-P-29

Thanks guys, I know my post was very general. But I was just kinda curious. As its a lot of money to spend
Thanx

mar3

iTrader: (8)

Do the streetport while it's out because, hopefully, this will be the last time it's out of the engine bay. Everything else you do can be done to enhance the porting's ability to increase your HP over time as your budget allows in your own garage. Start with the exhaust side, then ignition and then intake unless your dying to get to the suspension first. I went with a RP streetport and stock Nikki. We did the exhaust side and power increased notably. G-tech readings went like this. All tests done in the parking lot of a local community college on Sunday. Stock, tired engine, 85 HP. RP streetport exhaust basically stock with cat instead of thermal reactor, 108-113(couldn't get the same within 2 HP reading). RP custom modified "blower" header with 2" primaries into 2.5" RT cat with custom 2.5" tubing all the way back BUT still stock Nikki, 140 HP. That's where I'm stuck until I get the moolah to run a modified Nikki that can still get me through emissions...

MIKE-P-29

Yeah Im gonna do the streetport, Yaw modified Nikiki (if I can get him to do it) and I already have RB headers and exhaust.

Might eventually go supercharge, but depends on the money sistuation by next year.

Just so many options , and I wann do the best with what I can do at the time I got everything apart...

Thanks again guys!

BadAssRX-7

when i had my dellorto on my streetport i dynoed 165, with all the ****.... well i moved to denver and swaped the stuff to my 83 and bolted the stock carb back on. MAN what a pos. i can barly tell its a ported motor untill 4500 then it pulls stronger than a stocker. so i knowa carb makes a BIG diffrence. i cant wait to get my new 36 dual down drafts on

jimmyv13

My 85 street port is pretty disappointing with the stock carb. I asked RB about rejetting and they said not to bother. If you go with a SP, upgrade the carb.
If I had to do it again, I'd go with a bridge port. I dumped all of this money into my 1st gen (exhaust & porting) and my very tired stock 2nd gen walks away easily.

REVHED

A street-port is a nice upgrade when setup properly with the right carb and exhaust but I regret not doing a bridge-port. But like they say you can never have too much power.

why_pistons

unless your building an all out race car a bridge port is not the best way to go. With a bridge port you loose almost all driveability on the street: the car will barely idle below 1500 rpm(if at all) and your only power will be above 7000 rpm

peejay

There are many many people who will disagree with that statement. there are quite a few members of this forum who have had or who currently have daily drivers with porting ranging from half bridge (only secondaries are bridged) all the way up to peripheral porting.

Perhaps you'd also like to claim that you can't put a turbo on a bridge or peripheral port?

Acuspeed

To be honest, I tend to agree with why_pistons. Given, I have never had anything beyond a streetport done, however, while researching the topic, most reputable resources indicate that anything over-and-above a streetport will narrow the power band while increasing peak power. Unfortunately, the power peak on a properly done bridge port is above the 8500 rpm limiting speed of the stock apex seals.

Just my opinion after researching the topic in the past...

MIKE-P-29

Ok guys you are really confusing me. I want this thing to make some juice... I got all the parts for a 12A... What should I do? I want some power! Too bad this wasnt car audio I could talk all day and give recommendations, but im stupid when it comes to the world of horsepower... Maybe I need a 13b?

peejay

It depends on how it's done!

Keep in mind that every NSU production car had peripheral intake ports, as well as the exhaust ports! If you keep intake velocity high (that means don't hog out the runners HUGE) you will have better torque at any RPM you could want.

The NSU Ro80 had a 10A sized engine. It was making 120hp at 5500rpm, at the same time Maxda 12As had to wind out to 7000 just to make 100! Why? Peripheral intake ports.

Acuspeed

Perhaps this link will be of assistance: http://mrmazda.members.atlantic.net/....html#APORTING

Also, check out what other such as Racing Beat and Mazdatrix have to say about porting. There is more to it than simply widening the ports, particularly once you get into bridge port territory if you want everything to work properly.

MIKE-P-29

Maybe I should post a poll

I was gonna have Revolution Rotary do the work... Anyone dealt with them before. I know they sell parts cheaper than anyone, and they were EXTREMELY friendly on the phone...

http://www.revolutionrotary.com

REVHED

And how many properly built bridge-ports have you driven? Try doing some research before making incorrect statements. The bridge-ports I've driven feel just as strong as my streetport down low and really come on power at around 4500-5000rpm.

peejay

IMO Felix Miata is full of BS when it comes to porting... he says you can't put a turbo on a bridge or peripheral, and that half-bridge engines are a waste of time/money... meanwhile people who actually do it find that it works incredibly well.

Acuspeed

Okay guys, come on, calm down. There is absolutely no reason in the world to get worked up about this topic. I have done research myself from good resources that suggests anything more than streetporting isn't all that streetable.

If you've found otherwise, that's great -- please give us the details. We are all open-minded and one of the reasons of having a forum is because most of us don't have the time/money to try all sorts of different things -- therefore we share our knowledge (rather than being defensive about our position).

peejay

That's funny, my street port made more low-end torque than stock but at 5500 it felt like another rotor was added to the engine, LITERALLY... punch it in 1st gear and unless the road was perfect the tires would break loose at 5500, same thing in the rain - hit 5500 and better hope you're wearing Depends.

So your bridgey was actually less peaky than my street port

BTW Paul Yaw's REPU has a bridgey in it... and he says he even tows with the thing. Somewhere on the forum is a graphic depicting the V.E. numbers for a peripheral port vs. side port... the graph started at 2000RPM and was higher EVERYWHERE... V.E. is directly related to torque output.

jimmyv13

What other mods do you have? My SP is NOT like that.

peejay

Here y'go... funny enough I found it in a topic right here in the 1st-gen forum, on the RX-8 engine:



Notice that VE drops to about side port level at appx. 6500 - this would indicate fairly small peripheral ports. Larger ones would have lower VE at lower RPM but if you do the porting intelligently (there's that word again) you can gain top end while still having more low RPM torque than stock.

peejay

Headers and MSD direct fire.

Firstly, it might be a good idea to go to personal.riverusers.com/~yawpower and read the technical articles, specifically port timing and exhaust theory.

I ported the engine in a specific way, ignoring templates. The templates tell you to open the exhaust port opening time drastically so it opens lots earlier, for a better blowdown. That's great at high RPM where resonance tuning is more beneficial (with an exhaust that will fit under the car) but I left the exhaust opening time alone. Instead I opened up the exhaust closing so the port was about doubled in height. I had room to go higher but it would have required destruction of the steel sleeve and/or making a "choke point" in the exhaust, so I went no higher. Smoothness above all else. This porting gave me a fairly small port compared to many, but it still afforded me a good deal of overlap without going bridge port. (It idled nice 'n' lumpy too ) The intake port runners themselves were not touched at all, and the port openings were opened up about 10-15 degrees, paying close attention to making the two 90 degree turns as smooth and seamless as possible. As I was still using the stock carb and stock intake manifold, opening up the runners or ports further would have been pointless, and would have only served to reduce low end torque because of reduced velocity in the runners. Speaking of intake manifold, it was EXTENSIVELY modified and looks nothing like stock on the inside.

I know now some other tricks I could have done, but for a first engine I'd say it came out rather nicely. If it wasn't for the stock carb it would have made LOTS more power, but it outperformed a atock port engine in every way possible - fuel economy, driveability, power output, and idle quality. (that's one's the most important )

REVHED

Acuspeed, I wasn't getting worked up. I was just refering to the comment about having no power below 7000rpm which is absolutely incorrect. In fact I agree the bridge-porting isn't for everyone but it's far from what most people who probably haven't even driven one make it out to be.

Peejay, I'd say my torque peak is at around 5000rpm as well but it's not as noticeable since it pulls so hard from down low.

MIKE-P-29

**** ****, I dont wanna spend this money If the difference is only marginal. I was give a 30 HP figure with everything else stock... Of course Im gonna do a lot more... I want it to be marginally streetable. Like where it will idle etc... Dont care if its a 1000 rpm but you get the point. and please dont get in a shooting match over this. I just know a lot of you guys have street ported engines and give me specifications. Im gunning for Mustangs etc..