280z high altitude mode

[chaseincats]

Question for you guys, would jumping the terminals to engage the high-altitude switch improve my mpg?  Also, would this cause any engine damage if run like this in an area that doesn't require the switch to be on?

Apparently with it engaged, it decreases fuel by 6%.

Edited November 28, 2020 by chaseincats

[Dave WM]

3 minutes ago, chaseincats said:

Question for you guys, would jumping the terminals to engage the high-altitude switch improve my mpg?  Also, would this cause any engine damage if run like this in an area that doesn't require the switch to be on?

Put some new plugs in it, and try it. read the plugs after 100 miles (and listen to the engine for odd noises like backfires).

[TomoHawk]

I suppose that is what the altitude detector does: it leans the mix.  it's a switch connected to a small bellows.

But I forget:  should you use your regular fuel, or change octane for higher elevations?

I was also thinking that you could substitute a switch to get extra MPG on the interstate.  Just don't forget to go back to the correct mix ratio for passing or city streets!

Edited November 28, 2020 by TomoHawk

[chaseincats]

7 minutes ago, TomoHawk said:

I suppose that is what the altitude detector does: it leans the mix.  it's a switch connected to a small bellows.

But I forget:  should you use your regular fuel, or change octane for higher elevations?

I was also thinking that you could substitute a switch to get extra MPG on the interstate.  Just don't forget to go back to the correct mix ratio for passing or city streets!

I removed the sensor itself (and substituted a switch) because i doubt it worked and I couldn't test it with the FSM's test method since the rubber connector leaked air haha

[TomoHawk]

I keep forgetting, I have the Federal ECU... 

Oh well.  I  can just set the heater to 'floor' which means I get a vacuum leak from the brittle dashpot hose (heater guy just cuts & splices the hose instead of replacing it!) and that will throw the AFM off to cause a lean condition.  Or... I could add an electric valve to add air to the intake, post-AFM...

[Zed Head]

Thanks for following up on the switch.  It's a good tool for somebody who might have one of the aftermarket FPR's set to 38 or 40, or an AFM that runs just a bit rich, and just can't get that last bit of leanness they need to pass emissions or get a clean exhaust smell.  Just short that circuit and leave it.  Very useful for tuning.

You kind of reported the results in the wrong thread though.  Here's the post just to tie things together.

 

Edited November 28, 2020 by Zed Head

[chaseincats]

1 hour ago, TomoHawk said:

I keep forgetting, I have the Federal ECU... 

Oh well.  I  can just set the heater to 'floor' which means I get a vacuum leak from the brittle dashpot hose (heater guy just cuts & splices the hose instead of replacing it!) and that will throw the AFM off to cause a lean condition.  Or... I could add an electric valve to add air to the intake, post-AFM...

I'm pretty sure your car has the connector - it just didn't come with the sensor.  To my knowledge, they didn't create different wiring harnesses.  If you can find the connector, use a test light to see if it's getting power with the car running and that should tell you if this trick will work for you.

[TomoHawk]

4 hours ago, chaseincats said:

use a test light to see if it's getting power with the car running

So one terminal will have power, and the other goes to ground or the ECU?

[TomoHawk]

Is there a photo of the altitude switch?  Searching only turns up wiring diagrams, and there wasn't one on eBum, but I think it has a cylindrical body...

Edited November 29, 2020 by TomoHawk

[Zed Head]

I think that there's a drawing at the front of the Engine Fuel chapter of the 280Z FSM.  An exploded view of all of the EFI components.

[chaseincats]

47 minutes ago, TomoHawk said:

Is there a photo of the altitude switch?  Searching only turns up wiring diagrams, and there wasn't one on eBum, but I think it has a cylindrical body...

Yes, one terminal has power and the other goes to the ecu I'm guessing.  Here is a couple pics of the one I pulled out of my car:

Edited November 29, 2020 by chaseincats

[TomoHawk]

Thanks a lot.  I just haven't seen one under there, and I've been under there a lot.

In section EF (Engine Fuel) it connects to pins 9 & 12.  The sensors don't use a common +12V, so the ECU is supplying the 12V on one pin.

Edited November 29, 2020 by TomoHawk