A tidbit about IAT temps and resistance

[SVOboy]

Just a little something to throw out there in the hopes of collecting more information.

What I know fo shizzle:

OBD0 IATs are the same for Honda

That's about it, time to do a part number search,



So there you go. That's how IAT temps relate to resistance in hondas.



And there you see the stock Honda IAT compensation. Because I can tune my car I can change this any which way I please, ain't that fly. You'll notice that over a certain temperature it doesn't lean out any more, and also that the IAT temp does not affect timing (though if you have a knock sensor it might).

[rh77]

Sweet...now I just have to figure out if I have a knock or octane sensor. I was going to fill-up with 91-Octane after reading about the requirement higher octane vs. higher IATs -- maybe someone can help.

Taken from my datalogger Right now I'm running 130F air and the car is at an average of 20-degrees of timing advance and fairly low fuel trims. Since stock, I've increased the jacket temp from 77C to 89C and an IAT increase in 27C. According to the equation for octane:

From FAQs.org: "Increasing the water
jacket temperature from 71C to 82C, increases the (R+M)/2 ONR by two". Ok so I need a baseline to go by -- the manual says that 87 octane is required, but

"A new engine may only require a fuel of 6-9 octane numbers lower than the
same engine after 25,000 km. This Octane Requirement Increase (ORI) is due to
the formation of a mixture of organic and inorganic deposits resulting from
both the fuel and the lubricant."

I just seafoamed the engine and installed the PCV catch device (which is filling up) about 15K ago. Since I've been hearing knock at WOT / high RPM, I'd still stick with the base of 87. So far we're up to "89" Octane.

Now for the temp: "An increase in ambient air temperature of 5.6C increases the octane
requirement of an engine by 0.44 - 0.54 MON"

(27C/5.6C)* 0.5 = 2.4 MON

So now we're up in the 91-92 range.

So, should I run a tank of 91-octane to see if I get better economy?

RH77

[SVOboy]

What is your engine code? I don't think many if any older hondas came with knock sensors unless they're JDM/EDM, but if you give me the engine code I'll find out. Also, the fact that you can hear the knock says to me you prolly don't have one, but I've never driven one with a knock sensor so who knows?

Anyway, try a tank on 91 and we'll see if that equation holds any water.

[rh77]

Originally Posted by SVOboy

What is your engine code? I don't think many if any older hondas came with knock sensors unless they're JDM/EDM, but if you give me the engine code I'll find out. Also, the fact that you can hear the knock says to me you prolly don't have one, but I've never driven one with a knock sensor so who knows?

Anyway, try a tank on 91 and we'll see if that equation holds any water.

It's a B18B1. Thanks man...

RH77

[SVOboy]

Nope, no knock sensor for you. And I've never even heard of an octane sensor so I doubt we have one, but I will check.

[MetroMPG]

svoboy - that's awesome information. thanks for posting.

it's the first hard confirmation i've seen (aside from people just talking) that iat affects fuel trim directly (on some cars).

mind if i use that image on my site?

what engine / model / years does the plot directly apply to?

[SVOboy]

Use away that image, I believe it's taken out of a helms manual. This information is specific to the D16Y8 (96-00 Civic EX) engine, but I believe That the resistance is the same across all IAT sensors for honda from OBD0 to OBD2. I am unsure about this but I will search a bit more and hopefully get some confirmation or else I'll just test the sensors with some boiling water or something.

The program I have opened up is Crome, a tuning software, and I think that's B16A2 stuff (96-00 Civic Si), but that is the standard curve for all Honda engines. It is also split up by low, medium, and high load.

[SVOboy]

<a href=http://honda-tech.com/zerothread?id=1513454 target=_blank>Some H-T</a>

Moral of the story, OBD0 are all the same for honda/acura, I'll add this info to the top.

[MetroMPG]

Originally Posted by SVOboy

Use away that image

used it on the WAI summary at metrompg.com. good info. thanks again.

[SVOboy]

Sure thing, I'll see if I can find you something good that'll make a blanket statement about all honda IAT stuff (not 2001+ though).

EDIT: I thought you meant the first image, that picture you used is actually off my desktop, so yeah,