+3 aux ports close too late already, a bridge makes this worse.

 

How many 6 port street ports can put down ~120ft-lb at the wheels at 3200? Most 6-ports I've seen are hard-pressed to make that much torque *anywhere*, the ports just close too late and bleed off vital dynamic compression.

170 at the wheels with a half bridge is a much different driving experience than 170 at the wheels with a street ported anything. The street port may "feel" faster because the torque curve doesn't really do anything until after 5500, so you ghet that exciting kick in the pants after the engine finally gets up to that point , but the bridge just pulls and pulls and pulls from everywhere.

I know you will never agree with me, and that's fine. But saying that the two power levels are comparable is similar to (but not as extreme as) someone saying that a 400hp V8 is ridiculous because you can make that much power with a turbo D16. While technically true, they are very different in driving characteristics.

I'm never going to go street port again. It's half bridge at a minimum. That's how much better the port feels to drive.

 

I don't think the argument is that a good bridge ported motor isn't better. I think it's that an auxiliary bridge ported 6 port isn't better. It isn't. It's crap. That's not the fault of it being a bridgeport. It's because it's a bridgeport done on the smallest most restrictive port of a 6 port motor. A nice bridgeport on a 4 port engine with a good intake and exhaust would be a very different story.

 

I disagree that 6-port bridge port engines are no good, I've built strong 6-ports both street ports and bridge, From my experience the 6-port will make more power in the mid-top end. Keep in mind this is on car tuned correctly, good porting, a good carb and free flow exhaust thru a muffler.

 

^you mention a good carb and a free flowing exhaust. That's definitely a big part of it. Actually the biggest. As long as people keep saying that 6 port bridges work, kids are going to go out and bridge their 6 port motors with their stock intake manifolds and ecus. This isn't going to work. It can't. It never has and never will. The only way to make them work even in the slightest is to completely ditch the stock intake manifold, exhaust system, and ecu and either go to a full carb or full standalone. That's it. So for the sake of how it applies to 99% of the people who want to try it, they don't work. A bridgeport should never be used with stock manifolds or ecu's.

Now saying that, if I were going to go to the trouble of building a nice bridgeported engine that was going to use completely new intake and exhaust systems, I'd just use a 4 port. Keep it simple. So again, I still can't justify ever bridging a 6 port. There's no point.

 

Here's a link to a guy that claims he's using a stock ECU & AFM on a fully bridged
13b 6 port... (I've msg'd him, awaiting reply...)

http://www.youtube.com/watch?v=4Zh8gqI-L_0

Sounds great to me!!

Soo, whats the problem specifically? The RB J-bridge port closes later than the stock aux ports (we are talking about the 5&6th ports, correct?)

From my understanding the whole idea of bridge-ports is to get air in sooner...

 

That's judge ito's or to be more precise his daughter's car but he built it. This car was argued about online on other forums several years ago. Dyno's were shown and some strange things were going on and claimed. In one instance there was a quick 10 ft lbs spike in torque that was clearly an anomaly. The claim was then made that this peak was the peak amount the engine made. Stupid things like that. Arguments ensued on those forums with many different people. I don't remember ever being convinced that they were a good idea as a result of this build and we've never seen anyone copy it and get good results. There are no secrets. It's all known technology. Keep in mind that if the ecu was totally stock and nothing else done to alter it or added to it, that car wouldn't run.

Flow through the auxiliary ports and runners sucks. With the actuator rods in place it is downright terrible. Very turbulent. That's not what a bridgeport needs. Some may say to just take the actuator rods and sleeves out. That kind of defeats the whole purpose of doing an auxiliary bridge on one of these motors. If you want to do a bridgeport, do a real one where everything is done together as an entire package as it should be. If a person if going to that much trouble, just do a 4 port. It's that simple.

Yes you can physically bridge a 6 port motor. Yes you can physically put it together. Yes you can bolt it in a car, get it to start, idle, and run down the street with a stock intake and exhaust system. None of that is in dispute. You can make it physically move under it's own power. Lots of people have. The question is will you truly get more performance than a streetport in that scenario? The answer is always going to be no. You have to change other things for that to happen and as I said if you are going to go to that much trouble to get some real good performance from a bridgeport, start with a 4 port engine and get better results. People have this strange logic that a bridgeport is more than a streetport and is therefore better under any circumstance. Not true. It only applies when everything is done correctly in a way that everything works together. A port alone does not make performance. Many think it does.

People can make believe that it's viable all they want. They can tell themselves that just because 100% of the hundreds of people that have tried it before them couldn't make it work doesn't mean they can't when they try it. What's that old saying? Insanity is doing the same thing and expecting a different result. It applies.

 

That's just the thing. The same exhaust system and intake manifold that worked so nicely on my T2 half-bridge is awful on my GSL-SE half-bridge. The torque curve on the GSL-SE starts a lot later than the T2 did and it tapers off a LOT. On a Mustang dyno it put down 140whp (~180 crank) for about 1500rpm at the top end, and then just fell off around 8000. Rotaries shouldn't have a flat power peak like that, the rapidly degrading torque curve is a symptom of the exhaust choking off/intake too restrictive for the port timing.

Mind you, and I stress this, the same exhaust system (it never leaves the car) and the actual same intake manifold casting (save for the lower) were used on my S4 T2 half-bridge which had an awesome torque curve that started around 2000rpm and got its best 1/4 mi times and traps with shifting well over 9000rpm.

 

exactly, the circumstances dictate better, or the port in this case.

 

So how about just bridging the primary & secondary ports?

 

Don't use a 6 port motor!!! Here I'll use caps and some color. DON'T USE A 6 PORT MOTOR! Bridge a 4 port.

 

i simply cannot believe anyone can run a full bridge with the stock airflow metered engine management system. watch the airflow meter, now picture it going nuts with the airflow from a bridge. not to mention bridges pull less vacuum and need a bit more fuel than the stock ecu is mapped for.

 

In addition, don't use a 6 port engine, use a 4 port. Just to clarify in case it was ambiguous.

Been there, doing that, and the T-shirt doesn't fit very well. Guess what I'm building this winter? Hint: It doesn't have "aux ports".

 

I can sort-of believe it, in that the airflow meter isn't going to be "going nuts" since it IS damped, and the stock ECU dumps waaaaaay too much fuel, so it might actually approach a decent fuel mixture once the AFM tops out.

What i cannot believe is that it was done with the stock exhaust system.

 

I thought he used tii sec injectors and the exhaust wasn't stock?
and on a side note whats the afm top out at?

 

this is from the guy "all ports were bridged, including the 5 and 6 port. center plate was a very aggresive streetport with a very aggresive bridge port added.. sorry but no dyno figures on this engine. but on a different 6 port bridgeport. we pulled 230rwhp through the mufflers."
and
"MAKE SURE U RUN LARGER secondary injectors, usually go with turbo II 550cc injectors. always use the right impedance for your make and model second gen rx7. 2 types of injectors. low and high impedance."

http://youtu.be/INECtsxyZ74

and thats the same car>

 

i agree with your first argument about porting and torque but not about the stock ECU running rich enough to fit the narrow window that a bridge needs. perhaps with a walbro it might be semi drivable but still run like *** at points in the RPM range, then you'd need an AFC to compensate for the larger secondaries, it just doesn't seem to serve a purpose when you're not actually getting the most power from the porting with the inability to really tune it.

by nuts i'm not saying it will be slamming open and closed but if you press on the flapper while the engine is running you can easily see how sensitive they are to the fluctuations.

 

to update the thread, i am now planning on a large street port, with small eyebrows on the primaries on the end plates only, mostly for the brap brap. Then running RX8 rotors & E-shaft with an S5 counterweight. I am hopping the high compression rotors get me close to my power goals. I am also following though with the exhaust dump at the header, i know i will have to re-jet each time i head down to the drag strip, but i am ok with that.

 

the stock S4 NA AFM can read up to about 350cfm, or about 180hp at the flywheel

https://www.rx7club.com/showthread.p...ghlight=j9fd3s

also the S4 ecu does fuel cut at 7800rpm

 

 

I put down that much tq to the wheels at 4500

 

All I can say from the video is that I would absolutely hate to live near his shop.

Oh yeah and there is no way that is on a stock ecu. The burnout had the car well above the rev limiter and the throttle pick up and crispness are no way like what you would get from the "err on the side of richness" stock mapping.

Eric

 

thanks j9fd3s for the specs

 

if you have the money to do rx8 rotors why dont u do 4 port irons with a 1/2 bridge ? seems easier .

 

I'm gettin' reaaaaaaal tired of all these threads saying the same thing basically.