Hey guys, anyone know (off the top of your head) the function of the delay valve in the vacuum system managing the intake of an 86 NA?

Any replacement strategies? Should I order from Mazda, get it from a junkyard, or something else?

Thanks for any help!

edit: good golly I'm dense.. found the first answer from the search function.. how about the replacement strategies (assuming I don't want to do the TB mod so I can stay in E Stock for autocrossing).

thanks again

 

My version...not quite the right version probably.....on a n/a it holds the vacuum in the line b/t the delay valve and the double throttle diaphram so that you don't get a jerky operation of the diaphram as manifold pressures rise and fall rapidly. It's only in use during cold start until the water temp rises enough to close/vent the water thermo device that feeds the delay valve, then there is no vac and the diaphram spring loads open for the double throttle. I've never seen one that works, and I've been through the junk yards and yet to find one there. So none of my n/a's have one.I capped the vac lilne b/t the delay valve and the double throttle diaphram.

 

Clarification. the delay valves all work....it's just the double throttle diaphrams that are bad.

 

Thanks, Hailers!

So you're saying that the delay valve might be had from a junkyard with success?

As for the function of the double throttle the test for whether it works or not is whether you get the 17 sec high idle on cold start? or something else?

Until recently, the cold start high idle was functioning appropriately.

 

No, the delay valve, that little green football is something like a check valve. It holds a vacuum on the double throttle diaphram. I don't see one of those going bad ever.

On a 86-88 the double throttle diaphram, that is located on the front of the throttle body, holds the outer set of throttle plates closed during cold start, until the water temp gets up. It does that thru a vacuum that passes thru a water thermo valve - thru the delay valve- to the double throttle diapharm.

When the water temp gets up, the vacuum ceases and the double throttle diaphram springs fully open where it will stay as long as the water temp is up. (the turboii diaphram is a bit different than the n/a in that it does not spring open, so please don't write whoever you are with the truboii).

No, the high start up at approx 3000 rpm for 17 seconds has nadda to do with the double throttle diaphram or the delay valve. That is a product of the BAC in conjunction with the AIR BYPASS SOLENOID, plus the water temp switch that is located at the left bottom of the radiator. Must have both wires attached to the water temp switch at the bottom of the radiator.

One more actor is the neutral switch. If the car is out of neutral, that act removes a ground signal from the ECU which in turn eliminates the 3000 for 17 second start up.

So make sure your BAC plug is on(located on the left side of the engine), that the Air Bypass Solenoid is plugged in (located on the left side of the engine, behind the oil filler neck, has two large hose going to it and one electrical connector), and the water temp switch on the bottom of the radiator is on(two bullet connectors).

Oooops. Left out the water thermo switch on the back of the water pump housing. A bear to get to .

If you download the factory service manual at http://www.iluvmyrx7.com and put the Fuel section on your hard drive, you can find a checkout in the Fuel section, callled Bypass Air Control System in my manual.

It has you put a 2 Kohm resistor in the water thermo switch(the one on the back of the water pump housing), then put a meter on the brown/yellow wire of the air bypass solenoids plug, start the engine and look for 0 voltage at the browm/yellow wire for 17 seconds after which it turns to 12v. The engine should rev high during the 17 seconds if the plug was still connected.

So you see the 17 second start has nadda to do with the delay valve.

 

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MechE00:

What makes you think the delay valve is not operating correctly ???

Did you actually test it (there's a procedure to test it in the FSM) and find out it was bad ???

Just wondering,
Hugues -

 

i have seen the delay valves fail on the gsl-se's it causes the secondary throttle choke butterflies to be closed all the time. the water thermo valve also fails

mike

 

The checkout of the delay valve is in the manual at he url I posted.

The double throttle diaphram.....put a piece of vac hose on it and suck. The diaphram should pull the throttle plates closed. I bet money its diaphram won't work.

Or, note prior to starting the car, the position of the piston on the double throttle diaphram. Should be extended. The start the car cold. The piston should retract, closing the secondary throttle plates. Probably won't work due to the diaphram being busted imho

 

MechE00:

Could you describe what the symptoms for your problem are ??

I have the feeling the delay valve stuff has nothing to do with your actual problem (if any), but I could be wrong.

What you're describing originally only affects the opening of the secondary plates (set number 1 in front of the other set of secondary plates)

but then you are talking about something that has to do with cold start stuff, which is completely unrelated.

just wondering,
Hugues -

 

Hey guys, sorry for my hiatus.. regarding the symptoms for me suspecting the delay valve is not functioning to specs, there's really just one piece of evidence--

The delay valve is in two pieces.



The car is not difficult to start and it is not stalling, but I don't know how well it's doing power-wise. My clutch is in desparate need of replacement, and so I have been treating the throttle quite gingerly.. Once the finances align themselves, I'll be getting that replaced.

I'm gentle on a cold car, but for autocross I'd like to be able to get near stock power levels out of the engine once I get a non-slip clutch in there.