MARTIN

I was just wondering... cuz when my car was n.a I had disconnected it and the car ran just fine w/o it.

WAYNE88N/A

In a nutshell, it tells the ECU what the manifold vac pressures are, correlating to the load on the engine.

With it disconnected, the ECU reverts to an atmospheric setting (WOT)...Or 26.3 kPa, whatever the heckn that translates to

MARTIN

so in other words, your MPG just takes a big dip when driving normal and its not connected.. correct??

WAYNE88N/A

I would think so. I've driven around with mine disconnected too and didn't notice much difference performance-wise. Strange, huh?

Syonyk

I'd imagine it's also tied somehow to the shift-up light. It seems to be load sensitive.

-=Russ=-

1990RXHeaven

kPa is kiloPascals. thats worth about 1.5 cents

WAYNE88N/A

That's a very interesting observation, Russ

HAILERS

According to the 89fsms Relationship Chart, it effects: Lead and Trail timing, the Relief Solenoid, Switching Solenoid, Split air solenoid, Port air solenoid, and the fuel injection amount. Somehow I think this also applies to 86-88 also.

MARTIN

IS that on n/a or turbo ??? I wouldnt see why it would affect timing on the n/a. The fuel inj. part I kinda guest it..

WAYNE88N/A

It's input is probably used to disable all of the above mentioned solenoids during WOT conditions, wouldn't you think, Sir Hailers? Actually I guess it would enable the relief solenoid if it disabled all the rest...

Thanks for the S5 info, I'm sure it pertains to my S4. Sure of it. Humor?

NZConvertible

Many EFI systems that use an airflow meter as the primary load sensor also use the MAP sensor as a secondary load input. It reacts much faster than the AFM (or more correctly, the manifold pressure changes quicker than the airflow does), so it's useful for transient corrections, like rapid throttle movements. It's a good bet it's the main input used for ignition timing too (remember vacuum-advance distributors?).

HAILERS

NOt really. An example is the Relief Solenoid. At one time I used the 3800 rpm trigger of that solenoid to actuate my auxillary ports on a n/a via a solenoid and the discharge hose of the airpump. I was fat and happy because in the driveway I couold rev to 3800 rpm and those actuators would flip open like the dickens each and every time.

Then one fine day I put some leds in the cabin that were connected to the Relief and Switching solenoids. All seemed fine for a while then I noticed the Relief was being actuated at a rpm much lower than 3800 and seemingly at random. What a pisser says I. I abandoned that method of actuation of the six ports.

It was the input of the pressure sensor that was triggering the Relief solenoid at various times. Same with the Switching. On the other hand the tps coming off the throttle linkage might very well have been part of the events. I was not driving at full throttle though and the switching of the solenoids WAS happening at under full throttle at times. Fifth gear was another item that was messing up my opening of the six ports at 3800.

Put a led on your Relief solenoid and drive with the tps not fully extended and I'm fairly sure you'll see the Relief energize at rpms other than 3800 (see fsm).

That Relationship Chart mentions items that effect each other, but you don't know when.where or how much. There's a lot of interacting happening that we'll never know about.

That Relationship Chart in the 89 manual is very handy when TRYING to figure things out. It's an improvement to the fsm, much like the wiring diagrams in the 87 were a improvement that was discontinued for unknown reasons. Musta run outta rice paper.

jgrts20

I disconnected mine, it idles like its new and cold start is not a problem anymore!! I havent seen any performance changes either.

WAYNE88N/A

Lol, I should have known that you'd already tinkered with that system too, Hailers. Interesting tidbits, though. Maybe if I ever put the relief, switching, port air, etc solenoids back on the car I'll look you up if something breaks...

jgrts20- I don't know if taking that input out of the system is such a good idea, and I'd bet most of the gurus would agree (be the first time Hailers agreed with me in about 6 months, lol). If the car seems to run better without it, then you obviously have other problems that are being masked now. If you want, read out the sensor inputs at the ECU to see if maybe some sensors are out of whack...It's easy enough to do, and it might save you some headaches down the road...

https://www.rx7club.com/showthread.p...leshooting+ECU

Mint87RX7

hailers, so are you sure that it was not your tps messing up? my aux ports are not opening in my vert so i was going to hook it up to the air pump exhaust but then i just read this so now my idea sucks. i already have a rpm switch and junk on my 87 to open the aux ports and vdi but didnt want to go through all the trouble on the vert if i could avoid it.

HAILERS

Yes, I'm sure. Try that other method where the use the ACV exaust and a some type of restriction. Icemark is adament that it works. Give it a try. Low cost.

I prefer the Summit RPM switch myself. Always will.

WAYNE88N/A

Works pretty well if your ACV is rigged to act like it's dead and you use the ACV's INLET (air pump's outlet) also. Just remember that you'll have mucho extra air to play with (I sent most of the extra air to the non-existant cat location via the split air port, and the remainder out of a simple "T" with a 'calibrated' hole)...