McCarthy

Before you all say it yes i have done a couple of searches on this to try and get a little info before postng this up.

Now i have racing beat duel headers, twin custom 2" system all the way through, twin 50mm ITBs. 4x TII top mount injectors in custom rails and aftermarket ECU. I'm just about to rebuild the lump and have a couple of questions.

Should i go full bridge port or sick with a large street port?
What would be the power differences between the 2 on a 6 port?

Any thoughts / advice would be very much appriciated.

diabolical1

iTrader: (3)

my instinct says streetport, but i'll refrain from offering an answer for now.

my only question is why is bridgeporting on the table? i mean, what power goals and characteristics do you need from your motor to consider it or is it simply just to do it?

also, what generation car?

McCarthy

Yeah sorry its a '88 2nd gen EGI. No real goals just looking at options as the lump will be out and accessible. Just wanted to see people's veiws etc how well the bridge works on the 6port.

staticguitar313

iTrader: (2)

I'm also thinking about doing this, building a spare motor to swap in, I'd like to bridge the aux ports, just for giggles.

McCarthy

Why only the aux ports and not across both?

rotarygod

iTrader: (1)

*rant mode on* Bridging the aux ports only has NEVER worked for ANYONE ANYWHERE!!!! Anyone that says otherwise is delusional. It's a complete waste of time. The worst joke to ever befall the rotary community. Why anyone still thinks it's even slightly relevant is beyond me. It's pure and simple slow crap and your car will suck with it. Throw your engine away and replace it with a stock Civic motor. You'll be faster! *rant over*

Now saying that you can probably tell that I'm against the aux bridgeport. Everyone thinks about doing it at some point and everyone that has done it eventually realizes that it sucks and goes back to something far better such as a V8 (just kidding), a stock port. I'd rather have a completely stock motor than an aux bridged one. Why? They're nicer to drive!!! A bridge is not always better (and most of the time is worse) and this is a good example of one. Look at the words above my avatar. It's such a bad idea that I broadcast it. FWIW, It was the first port job I ever did. I've written extensively in the past as to how air flows through the ports and why it doesn't work like one would think it does. No, keeping the stock sleeves in place with them is not a good idea either.

Let's go to the other mentioned option, the full bridge. I see a couple of issues with this as well. First is that I really just don't like bridged 6 port motors. If you're going to do it, do it right and use a 4 port. Keep it simple.

Also it is mentioned that there is a true dual exhaust. If you want a bridgeport, change the exhaust. You absolutely, positively MUST run a collected exhaust with a bridge or peripheral port engine to get the most power out of them. You are wasting your time if you don't. You also must run a free flowing intake manifold and NOT be using the stock ecu in any way shape or form due to the air flow meter. If there is a stock intake manifold, ecu, and a true dual exhaust there is only 2 porting options and that is it. They are stock, and streetport. That's it. There is no other viable, usable porting style and nothing else will beat a streetport using the same setup.

If a person wants to go to a bridgeport, there is no cheap or easy way to do it and still get good results. You need to have a complete intake and exhaust designed that accounts for this porting. You also need to have full control whether it be with a carb or with a standalone ecu. Whatever it takes to tune it and not use the air flow meter. This really needs to be adhered to for best results. Just because a little more is better does not mean that more still is better yet. It doesn't work this way when it comes to porting. Everything has to be designed to work together as a unit and must be treated that way.

I have had people argue with me saying that just because I and every single other person in history who has tried something and hasn't made it work, doesn't mean they can't. That may be true but I know what the odds are and I'll take the bet against them any day.

Here's a general guideline for those who don't know what to expect from properly doing something.

A stock port is capable of about 175 rwhp or so max assuming everything is done properly. It's not easy to get but it's possible.

A good streetport should average in the low 200's rwhp. Most people don't hit 200 rwhp but it's not difficult. I've even seen one instance of a VERY large streetport that made crap low end power that made 290 rwhp revved up to 9500 rpm. Not usable for a streetcar in any way shape or form and it was on a race car anyways but the point is that you don't need huge overlap to make huge power. The Renesis is a good example. The stock pre-09 motors have been tuned to 260 fwhp and the '09 motor has hit 280 fwhp in at least one account. Yes they were tuned to within an inch of their life but it's possible.

The point being that you shouldn't fall into the trap of thinking that a large port is good so going larger is better. If you don't design the rest of your system around it, it won't work as good and usually not as good as you would have gotten should you have stayed simpler. I still have yet to see a dyno of a aux bridgeported engine that is higher than the highest stock port dyno I've ever seen and I doubt that I ever will.

A bridge can work spectacularly if done properly. Gut the car, throw everything away, and pretend you are designing a no compromise engine, transmission combo. Then you'll see nice numbers from bridging.

A turbo changes things a bit but again don't assume that it'll always work. A small turbo isn't a good choice for this port either. I could write a book on this topic.

peejay

Testify!

I just want to add that just because someone spends a LOT of R&D time on a setup, and gets a certain power figure, or a certain torque curve shape, doesn't mean that everybody can. If "everybody" could do it then "everybody" could have done it 20-30-40 (!) years ago when the engines were new. The first bridge ports were only making about 200hp at the crank, with wide open exhausts.

We've progressed a lot since then, and a lot of the knowledge is (thankfully) available so we peons don't need to re-do months/years of R&D. Which all that really means is that the bar for "everybody" has been raised but the "max" bar is higher still.


Is it possible to get 300hp from a street port? I used to think no, but it's been done, so it IS possible.

Is it possible for you or me to throw together an engine from off-the-shelf or hastily cobbled together parts, and make 300hp, just because some guy who had nothing to do for six months but try different (100% custom) intake manifold and exhaust system configurations was able to? Not on your life!

This is why my street port 13B (4-port) doesn't even break 160whp. It's a mishmash of parts. I expect to find another 10, *maybe* 20hp in going from a stock 12A exhaust system to something 2.5" and with no baffles anywhere.... but I am not expecting to make 200whp just because other people can. I don't have that kind of time.

OTOH, it demolishes a stock 6-port, and that's all I care about

diabolical1

iTrader: (3)

well, i guess i'm not as passionate as Rotarygod about trying to preach to the masses. i don't have the energy. however, i share his points of view on the subject. so my advice would be to take heed. no need for me to re-type them.

a good streetport will serve you well, i promise.

rotarygod

iTrader: (1)

A streetport is much nicer than many people think it is. If you've never had a ported engine and only know of the different styles, it's easy to think that just moving up to the next type is going to be better which is where the aux bridge usually getstossed around as an idea. It's just not that easy though and more isn't always better.

I mess up above. The large streetport I saw did 290 at the crank, not the wheels. It was on an engine dyno.

diabolical1

iTrader: (3)

oh absolutely! i don't need convincing. i think many things get taken out of context on the boards, and then you start getting warring factions of extremists! the numbers (HP, torque, dick size, whatever) start getting thrown around and which fuzzes the concept of context even further. add the fact the we live in a culture that promotes "bigger" and "more" and people that don't know any better have no choice but to make the wrong choice ... or something like that ...



i guess that was my rant, but it's over now.

peejay

My SP may be a tad *too* big... the only way it has decent drivability is if all of the throttles open at the same time, IE it barely wants to run on the primaries alone.

So this just means I need a spare TII upper that I can carve up to accept a single honkin' throttle body

That's another thing... guy X makes Y hp, that doesn't mean guy Z can also make Y hp even though he's using a different intake manifold, and the one he does have was ported by someone who has no clue what to do (ZOMG gasket match !!!), and the ignition timing and fuelling and exhaust system are different, and guy X used 100% new parts and not stuff scrounged from behind the tire stack... but other than that it's the same engine so it should make the same power right?

McCarthy

I had read what people are saying and duely noted indeed. Street port indeed. As said above was just looking for the opinions/views as the lump will be out anyway.

rotarygod

iTrader: (1)

It's good to do homework but it's always tempting to want tp push things a little more.

As was noted above, just because one person gets a certain power number doesn't mean someone else will. There are many little things that can make a big difference. Every once in a while you get someone who hits a number that is above what is typically seen. It happens. The high power nubmers that I've stated weren't done by people building engines in their garage using a template they bought. They were done by people who spent alot of time and effort on research, testing, and tuning and going through many different combinations to get to where they did. The point isn't to say you will get a certain power number. It's really to show that there is far more potential in these motors than most people realize and it's with far less aggressive porting than most people think possible.

On a street car, it's almost impossible to go wrong with a streetport.

Lasse wankel

"Flame suit on" ML has done some 6 ports bridge motors over the years. Best motor was a combo of 4 bridges on front and rear side housings while the intermidiate was heavily streetported 12A 85 model. It ran a ProSpark stand alone system with 2 45 mm butterflies for outer side housings and 40 mm for intermidiate plate The exhaust system was equal length primaries with a 3" exhaust. The engine was tunes by ProSpark Guru Aulis and made at cranc 290 hp@9000+rpm I don't know how accurate the rolling road dyno was converting to fhp but the little NSU TT sure was quick

/Lasse

rotarygod

iTrader: (1)

I didn't say you can't port those motors. I'd rather just see a 4 port done instead. That car also wasn't using a stock ecu, intake manifold, exhaust, etc.

Project86

i have an 86 na and im gonna go to banzai for a rebuild and have them street port. im pretty excited. besides bridge porting isnt really practical for street anyway is it? you wont make power until around 5000 i think. correct me if im wrong.

peejay

The single biggest contributing factor in WHERE the powerband lies, is intake port closing. Port area/velocity and exhaust tuning play a critical role as well but they are complementary to the intake closing.

6-ports have REALLY LATE intake closing when the aux sleeves are open. About as late or later than a really nice street port. Take out the sleeves and it feels like a street port to drive, too - kinda soggy down low and in the midrange and then the characteristic HOLY NUTS at the 5000-5500rpm point when it comes "up on the port".

A properly street ported 6-port shouldn't make the aux close much later than stock. Some people don't touch the closing line at all, others merely dress it for a nice airflow transition.

This is generally why people say "you can't/shouldn't port a 6-port". They're already fairly huge, and they have lots of port surface area relative to a 4-port ported to similar specs, which hurts flow. You can still have a good amount of fun with it, though.

A bridge port changes the HOW MUCH of the powerband. Exhaust tuning and intake tuning becomes critical. And the thing is, you can't look at the powerband merely as what it is at WOT. You need to consider the part throttle aspect. If you looked at a stock/street port as a smooth flat plane of power that was directly linked to throttle opening, the BP would be more of a curve, not being very useful at low throttle openings. They make more ultimate power than a SP (at ALL engine speeds, not just the high end) *but* they don't make gentle-throttle easy tip-in street friendly engines. The more overlap, the more the engine needs to be treated like a switch instead of a dial, power-wise.

It's fun for a few months. It can be street driven if you don't mind those characteristics. (NSU exclusively made peripheral port engines, and they were mated to torque converters to smooth out the power delivery) Most people get bored with it and revert to a street port, if they want to enjoy driving their car on a regular basis.

I logged something like 7500 miles in the six months I've had the 13B street-port in my RX-7, and it is not my primary vehicle. (This includes a 1000 mile break-in during the week between dropping the engine in and the first rallycross, at $4.25 per gallon and about 15mpg due to the over-rich tune) I think I only had 1000 miles on the P-port during the two or three months it was installed, and that was the second time I'd had it in the car...

I drove it again today since it's warm enough and the rain washed all the salt away. I might make the SP bigger but I won't go bridge, it's nice to be able to drive it any time, anywhere.


Cliff's notes: A big SP and a big BP both are peaky things that don't really get moving over 5500 or so, but a SP is much more friendly to small throttle openings, thus the name STREET port

Hyper4mance2k

iTrader: (40)

So I'm planning on getting my car off of the street soon and turning it into a full time autoX car. I was planning on bridging my 6 port 13b. I wanted to just bridge the front and rear iorns with a conservitive bridge, and a huge street port on the intermediate plate. Since it really seems as noone has every really done it and gotten results I figured I'd be the first to try it out.

McCarthy

OK so we have decided that he AUX port is rubbish and not worth doing and that indeed it looks like the street port is the real way forward. Now bearing in mind the conversaion is based around an 88 13B N/A 6 port with after market ECU/exhaust etc i ask what happens/ or are the effects if you where to bridge on the side and interplates as in this pic.

Please be aware i ripped this off the web and very crudely added in the red line to roughly represent what i'm talking about.

rotarygod

iTrader: (1)

I say go full bridge or go home! Change the intake manifold and ecu to take advantage of it though.

Twins80s

iTrader: (3)

aftermarket intake manifold check
aftermarket ecu check

....looks like i should do some porting when I pull my motor out

Hyper4mance2k

iTrader: (40)

That's what i was thinking about doing, but I just can't imagine there being any velocity through the aux port.