IACV & AAC Delete

[JeffersonC]

Can all this idle accessory gear be deleted and setting the idle with throttle body adjustment and tuning?

[caliber676]

From my understanding with a map base tune it is possible. I plan to do so with my greddy manifold, I'll see how it goes.

[spinnanz]

Why take away your ecus ability to adjust idle dependant on load? If you love your car having a great idle and then stalling when load comes on (Ac, alt, p steer) go for it. If it was a good idea and Nissan (and Toyota and Honda and gm...) could have saved $5 on each car by not fitting them, they would have.

[Bruizer]

Some aftermarket ecus (like the VIPEC) doesn't not use the stock idle controls.

[spinnanz]

Correct, but in order to adjust idle dependant on load they must use some sort of air bypass valve, if they don't they will be unable to adjust idle. That's all good in a race or track car but I can tell you it's not fun on a daily driver.

[caliber676]

^If the valves aren't supported by the standalone ecu they won't work, they need an input. Many people daily drive with vipecs etc so it isn't necessary a mandatory thing.

[JeffersonC]

Just something I thought I could possibly eliminate. Im old school and still learning about modern tuning. I know all my carb'd engines Iv built with power steering, AC, vacuum pumps, etc never had any problems with idling even with massive camshafts. I will look into it more (and probably have to try for myself) to see if I can make it work. This build isn't a daily driver, a weekend burner and fun car.

[spinnanz]

Weekender it would be fine but I know when we had idle set up for say extreme unloaded (daytime, warm weather) compared to nighttime cold (lights, heater, demist etc all on) if you set the idle up for one it would either stall or idle way too high when the opposite load happened, depending on which way you went.

[caliber676]

Its been done, ill see if i can dig up the thread.

[supersayianjim]

still no thread?

[JeffersonC]

Found this post online. Probably best to keep them and be hassle free.

The IAC, AAC valves should share a 14mm or so vacuum hose that provides air to both idle valves, which provides air to intake plenum, just behind throttlebody on GTS or throttlebodies on GTR engine.

IAC valve adds extra air to intake plenum on top of what AAC valve does to raise idle rpm, which matches rich A/F ratio + advanced ignition timing when engine is warming up and slowly closes as engine warms up and A/F ratio goes leaner and ignition timing decreases.

AAC valve controls idle rpm when engine is warm and raises idle rpm when aircon, light's, etc is turned on. Without this idle valve, engine won't idle, as like IAC valve it provides air behind throttlebody or throttlebodies when their closed.

To run without AAC valve involves opening throttlebody or throttlebodies up a little bit to provide the air that AAC valve provides to intake plenum, resetting TPS idle contact to suit new position / angle of throttlebody plate inside throttlebody or throttlebodies.

But running without IAC valve is bit more complicated, as IAC valve closes as engine warms up and provides less air to intake plenum and there's no way I know of to vary throttlebody plate inside throttlebody to provide less air inside intake plenum as engine warms up.

[bobbo]

Yea. Although there is some room for improvement with these cars for the most part the designers and engineers at Nissan knew what they were doing.

[Dragon Humper]

The DJetro doesnt use the valve either, its basically a third nipple. The normal ignition timing for a fully warmed up motor is 20deg. The Jetro raises the timing to as high as 40 to regulate the idle for AC, cold starts and what not.

I have driven my car in any extreem that you can think of, even -10c, and it does just fine. I've thought of getting rid of it myself as it takes up a crap load of room under the plenum.




Jon.

[Skym]

Another option is a manual choke (to replace IACV, which is a automatic choke) from a pre 80's Nissan. Nissan Sunny had a manual choke up to around early 80's.

[Dragon Humper]

Shouldnt be necessary, even the knuckle dragging Djetro has a coolant temp correction for cold start enrichment. It was even a bit on the rich side, I had to lean it out a tad to get the most vacuum at idle when it was -10c outside. Rock solid idle too...1300rpm even with my lumpy cam timing settings.

I would imagine that any "modern" aftermarket ECU would be even more capable of dealing without an IAC valve.



Jon.