can someone please explain to me EXACTLY how the 5th and 6th ports on an 88 s4 work. mine are not working and im not sure what to do because when im at 115- 120 i have absolutly no power left. it is an 88 streetported n/a motor. also i have no cat and custome exhaust from manifold to Y pipe. please if anyone can explain in lamens terms it would be awesome. im new to the rotary world and im trying to figure these things out step by step. thanks in advance

 

Well, If your at 115-120 im guessing thats in MPH. There somtimes just isnt any more power to give at those speeds.

BUT. on s4 engines they work off the exhaust system. When exhaust velocity (right word) exceds 1.8psi the ports will open up. IF you have a custom exhaust system they probubly wont work. You can either wire them open, some say its stupid but sometimes at the point in someone life, there just isnt any other way to make them work, or do it electronically with an air pump.

its kinda hard to explain in words exactly how they work. If your new to Rotarys here are some sites that will help you out

http://www.rotaryillistrated.com
http://rx7.subbuteoclub.com/training.shtml
http://www.racingrotary.com

This PDF file from the training manual which is found in the 2nd link above is for the fuel and emmisions system. Go to page 14 and it will show you how they work.
http://rx7.subbuteoclub.com/Training...%20Systems.pdf

 

I have an 88 S4 that had nonfunctioning ports. We used a ford lumbar airpump combined with an RPM switch to activate the now "fully electronic 6-port activation." Before that we tried wiring them open but that killed my <3500 rpm power. I can tell you all about it if you want, my AIM screenname is jsberentsen (but I might not be online much since i'm home for xmas this is my dad's username btw mine is joeberentsen). My only regret is not getting a more powerful airpump, maybe use one from a walmart portable tire pump or just double up the one I have.

 

The car gets to 130 with ease now.

 

mine even with ports open would have a hard time getting to 120-125

 

dont be looking for the highest MPH for calculating HP. I forget what the ratio is but its so small. like an extra 40% hp equals 1% increase in top speed or somthing odd like that?

 

^i doubt it works just like that, it prob runs on a bell curve with a point of deminishing returns.

 

well mine are absolutly non functional and i can hit 120 quick i just has no power after that.

 

this was covered in depth not too long ago.
5th and 6th ports start to come on at 3300 ( ~1.8psi backpressure), finish coming on at 3800 (~4.6psi backpressure), and the aux injectors come on at 3800 (electronic) as well on a s4 NA. With a free-flowing exhaust, you never see that much pressure, so you don't get it. You can do a million things (search!) to get them on all the time, but this causes a small loss of low-end torque. Those of us that are more constructive (myself not included) build a circuit and use the tach signal and an air pump to activate them manually at whatever RPM.

 

if your 5th and 6th ports arnt working you should notice the power band tends to stop climbing around 5000-5500 rpm, it goes flat after that....


now are you shifting into 5th at 120???, 5th is a very long gear( could hit 200mph theoreticlly its so long!)

5th is so long that the car cant pull in 5th ussually at that speed ussually.

ive found to get over 120 i have to fully rev out 4th gear all the way out to "fuel cut " then i can hit about 135 in 4th but going to 5th didnt have the power to keep accelerating

if your in 4th and you run out of steam at 120 then something might be wrong.....