new aux port idea- will it work?
 

Ok heres the deal. I have an 86 NA. No cats, stock manifold. right now i am using the ACV dump tube method to open my aux ports (6 ports). I want to get rid of the acv and air pump. so heres what i am thinking:
If i drill a 1/8 inch hole in the top of my downpipe and put a hose nipple on it and run the hose to the 6port actuators, will it work? I have free flow mufflers so not much back pressure...

what do y'all think? is it worth a try?

-Pat

Dont you need 3.6psi to open the 5/6th ports?

i think its 2.8 psi...
im just not sure if i'll get that much or not.
i could weld the nipple on at an angle to catch more exhaust..might help.

Won't the temp of the exhaust melt the rubber? or are you using braided hose?

on my system,the guy that made it installed a pressure pick up tube in the header-it points straight in to the exhaust port,pertruding slighly on the inside of the header.is has a brake line fitting on it,so i just use metal brake lines with threaded fittings.they open slithgly late around 4-5k,i think.but,the difference in low end before/after[i had pulled my sleeves out at first,now i got the pineapple sleeves]is huge and very worthwile in my humble opinion.[over no sleeves,i mean]
d

I kinda doubt it because of the heat also.

well im not too concerned about the heat. after all the stock s4 setup used the split air pipe that came straight off the main cat, ran about 8 inches, then teed into a rubber hose so it must work that way... im just wondering how to do the hose and if i'll get the pressure that i need. right now my idea is to drill a hole in my downpipe about an inch below where it bolts to the manifold and weld a piece of 1/4'' ? steel tube into the hole at an angle so that the end faces "upstream" into the exhaust. then just run a hose to the 6port actuators. i think i will try it this weekend and see if it works or not. unfortunately, if it doesnt im gonna have a hole in my exhaust...

-Pat

yeah, the backpressure comes from holes in the manifold. That pipe to the cat has nothing to do with the 6 ports. If you take off the manifold there is a hole leading back into the block. It leads to the actuators. So that pipe means nothing.
Whay take off the airpump and stuff anyway? It won't save much weight at all, and you might gain 2-3 hp from not having to drive it anymore.

yes it does the split air pipe provides the air pressure for the 6ports on the s4, as opposed to the air pump on the s5. the actuators are not in the block they are outside. on either side of the acv.

the reason for takin it off is mostly just to clean things up, although the airpump and acv probably add up to 25 or 30 lbs, which some people would give their left nut to get rid of. and 2 hp or so, which the same people would also be very fond of. (i want rid of it, but would opt to keep the family jewels intact)

it all depends on your idea of the car. if it is ur daily driver and you just want a sporty car, then its fine with all that shit on there. if u want the fastest car around and a clean engine bay, not to mention less soreness of the knuckles, then u may want to yank some stuff. to give u an idea here, i have already removed my ps, ac, cats(obviously), egr, cold start, and am working on the vacuum spider.

wow that took forever to type

-Pat

****yeah, the backpressure comes from holes in the manifold. That pipe to the cat has nothing to do with the 6 ports. If you take off the manifold there is a hole leading back into the block. It leads to the actuators. So that pipe means nothing. ******

Wrong. The single hole that is left open when the exaust gasket is put on, is the feed for the EGR valve.

Could someone clarify to me whether or not the air pump plays a role in the opening of the auxiliary ports on a S4 (not S5) stock setup ?

I kinda think it does, but I am not sure.

Under certain conditions (probably medium load when warm), the air pump is injecting air into the split air pipe, which tees into the actuator pressure feed line.

Assuming the ports open under the above conditions (I don't know if they do but let's assume they do), would it be due to pressure from the air pump or pressure from the exhaust alone, or a combination of both.

I am not talking about heavy load conditions (like WOT) when the air pump is probably relieving, which takes it out of the picture.

just wondering,
Hugues -

On the S4 cars, the air pump has no role in opening the 6-ports. The air pump only dumps air into the split air tube under light/cruising loads. At medium/high loads, the air is dumped out the ACV. This is why people can actuate the 6-ports from the ACV exhaust! At about 3500-3800, there is no air going to the split air tube...So:

On the S4 cars in stock form, the 6-ports are actuated totally from exhaust back pressure generated by the cat and mufflers. You need about 2.2-2.3 PSI to open the ports. (Less is you mess with the adjustment screws)
The S5 6-port actuators need about 2.6 PSI.

So your stripping your engine down to the bare minimum. That's fine and dandy. What I'm wondering is if your trying to make things simple, why not just wire them open and forget about punching holes in your exhaust? That is by far the simplest solution and the cleanest. Hell, remove the sleeves entirely while your at it. Then you can grind out the lower intake manifold and fill the holes with JB weld...

UNLESS of course you like having your low end power below 4500 RPM. So what do you do in this case???Remove the air pump, buy an RPM switch and air horn motor. Then use one of the 3-way solenoids that you removed from the vacuum spider to have a fully adjustable electronic actuated 6-port solution. Total cost is around $75 bucks.

Jeff
86 modified NA
89 GTUs

yes, right on.

I don't know much about fluid flow,

but if you're under light/cruising load, the pressure from the air pump in the split air pipe plus the pressure carried by the exhaust may be able to open the auxiliary ports, NO ???
or do I have it completely backwards ?

Hugues -

The activation of the ports does come from the cats flow through a check valve.

My concern on Patmans orginal question would be that the exhaust pulses may be to much to actuate the 5/6th actuators.

At the top of the down pipe, the flow is very pulse ridden, which might make it so the actuators are snaping open and closed at the wrong times in a rapid ON/off Pulsing. I don't think relocating the check valve would solve this.

There is a reason that the factory (and Racing Beat) has their connection for the actuators so far down at the main cat's location. It because that is the nearest spot that the exhaust flow is not jack hammering.

Why does racing beat put that little pipe out the side of their presilencers? Is it possible that there is enough back pressure with a presilencer to opporate the actuators? Or is that just so the ACV has a place to dump unused air?

yep for the actuators

So even with a header and presilencer there is still enough pressure in that little tube to properly operate the actuators? Do you think there is enough pressure to support the actuation of both aux port sleeves AND the vdi? If so, I may loose the air pump and run that split air pipe again, directly to a 3 way "t" controlling both systems. I'm not so worried about when they open as long as they are open no later than when they opened stock. I can deal with them opening early. You really just need them closed when starting from a stop as far as I'm concerned.

[QUOTE: wankelhead]
on my system,the guy that made it installed a pressure pick up tube in the header-it points straight in to the exhaust port,pertruding slighly on the inside of the header.is has a brake line fitting on it,so i just use metal brake lines with threaded fittings.they open slithgly late around 4-5k,i think.but,the difference in low end before/after[i had pulled my sleeves out at first,now i got the pineapple sleeves]is huge and very worthwile in my humble opinion.[over no sleeves,i mean]
d


Wanklehead, Are you the guy I sold my custom dual exhaust to? Or did you buy it from the guy I sold it too, cause thats the exact mod I did for my custom built dual exhaust when I was runnig a ported n/a. I also installed dual O2 sensors, one on each header runner so I could tune front to rear fuel ratios. BTW with the ported motor they opened the aux ports between 3400-3800, the higher velocity/more volume from the street port i guess is what made them open earlier when on my car.

pretty much ANY single system (single meaning collected) exhaust system should have enough back pressure to open 86-88 aux ports


~Mike...........

Well cool the impression im getting is that this is a feasible idea so as soon as it gets a little nicer here i'll try it and see what happens. to answer your ? wozzoom i do want low end power and i would like a system simpler that the air compressor or solenoid mod. i am concerned with the reliability of the parts involved and i am a major cheapskate and dont want to spend 50 bucks for the rpm switch.
whats this about pulsation? that sounds kinda worrisome... do u think that the pulses would be far enough apart at 3800 rpm to make the ports open and shut? i am inclined to say no, but it may be a consideration that i should take into account when i decide where to t into the exhaust. another reason for this thread by the way is that if this works it would seem to me to be an easier way for new rx7 mechanics to mod their car. everyones first step is to get an exhaust, and for the s4, that totally screws your port operation. anyway, ill try it soon and let y'all know if it works

-Pat

The exhaust pulses above and below atmospheric pressure.

That's the principle they use on some cars to inject secondary air (would replace the air pump on the 7), it's called the pulsation secondary air system, or something like that.

At above 3,500 rpms, it may be ok but who knows ???

It also depends on where you put the pressure feed line like, right at the exhaust port, or after the converter (or any other obstruction). There's a dampening effect and the pressure is not as high.

You may want to look into recent posts by WOZZOOM. He's got a setup with an electric air pump that looks pretty good and a rpm switch, but it is a little bit more involved.

Hugues -

ok...was browsing my old posts and saw this..update:

i have done this, it does work.
under very low throttle there is a little bit of pulsation at around 3500 rpms. under any amount of acceleration there is none.
i have normal 6port power thru the normal range.
and it takes up no space, looks fine, and was real easy to do.

Pat

Euro-spec butterflies, works with vaccum and does not need any emissions or additional actuation thingys, and they dont stick.

http://rx7cz.net/photos/works08/IMG_0015.JPG