Hot Air Intake too Hot, no good for MPG!
 

Just did almost a half tank with my aluminum duct hose HAI totally up against the Exhaust Manifold, and judging by the gas gauge, I have gotten poor FE. Maybe like mid thirties, as opposed to my average 41-43mpg. Not having instrumentation sucks, but I just backed the hose up so it is parallel to the em, allowing sufficient cool air. When i moved it, it was really hot! Wish I could monitor the IAT in realtime, rather than all this guesswork. :D

You could just use a multimeter to measure the IAT, ;)

Ben, just read thru some threads and came across the resistance to iat graph you posted. You know whether our cars like the same iat? did you find your optimal iat? know of a link that will show me how and where to hook up a wire to monitor my iat while driving? thanks!

edit: just saw your iat mod thread from last year when you still had dpfi, and I saw where the iat sensor is on the im. do i need to splice into one of the wires that go into that plug?

I've never fudged around with it much myself, someone else might have some insight.

But, you can find a set of pinouts to figure out which wire to tap, shouldn't be all that hard, I don't have any offhand and I'm outside right now, or else I'd help you out.

iat sensor has 2 wires. red-goes to ecu, and green-ground. to determine iat, i need resistance, right? so which wire(s) go to which node(s) on the multimeter?

just ran red to neg on meter, and green to pos. reading was zero when i set it at 200 ohms, and 2k ohms. Then i switched the dial and then back again, and it would read approx 1k ohms on the 2k setting and 200 ohms on the 200 ohms setting. It only reads for a second and then switches to zero, so i have to keep switching the dial to get a reading that lasts a second or so. This normal? the 1k ohm reading translates into approx 105 degrees fahrenheit which seems normal for a reading with the intake hose sittting 3 inches away from the em, a couple minutes after a cold start. This would def explain my crap mpg when the tube was against the em, must have been really hot, like 200 degrees even, or more:eek:

Trial and Error
 

I've found by trial and error that the 'Teg likes IATs around 80-100. Anything above or below, and the fuel maps start to compensate with more fuel to either warm the emissions system or cool the charge. The hottest actual temp I noted was around 220F with an HAI. It was in the summer, and of course the car had no power and needed premium fuel to prevent detonation -- it required more throttle input and leaned-out the mix to a degree as noted on the long-term fuel trim. After trying cold, warm and hot, I noted on the scangauge that 95F seemed to be what it wanted. I can cruise with decent power at a lower throttle input to achieve a higher FE rating.

YMMV as every ECU is different, but you may have to experiment with real temps first or get your hands on a fuel map with the IAT variable included.

RH77

Slightly off topic, but why go through all the hassle of reducting your intake tract, instead of just relocating the IAT sensor? Or simply rewiring the IAT circuit so that the ECU always sees the ideal temp regardless of conditions?

Because:

1. The IAT occupies a hole on the very aluminum intake manifold of his engine.
2. Lying is mean.

But yeah, just changing the air intake charge is the easiest way. Lying would cause problems with lean air mixtures and o2 compensation, whereas the HAI would be working with the ECU and not against it.

Not a liar
 

I've never been comfortable "lying" about it, which is is why the duct-work was installed -- Saturns seem to really like the IAT mod, and other models: not so much. The concern is that you'll detonate the engine to its demise with an overly-lean situation and not let the ECU do job it was hired to do.

To maintain that ideal temp, I'm considering an installation of 2 ducts: one that draws the ambient outside air, and one closer to the exhaust manifold as I had before (I've used both idependently). The goal is to use the IAT signal to get the actual intake closest to 80-100F using a feedback loop and valves to open and close the flues of each air source. It sounds like a lot of work, but it's the safest response for a Honda engine. The IAT-resistor mod can't compensate for reality: air density, emissions system feedback, etc. which changes in an instant.

RH77

Hello -

I wish we had the ability to extract the Air/Fuel mappings from all these ECU/PCMs. They are all over the place in terms of what they like. Then we could optimize to the max. All that info is just sitting in the car computers lauching at us!!!!

Ho-Hum, I guess it's just trial and error. :mad:

CarloSW2

SVOboy -

Yes, I agree with this waht RH77's said. Also, like Red, this is my only ride. I want to do a compromise between maximum MPG and minimum risk to car. I could mooch off my wife's car if I break my car, but that wouldn't be cool. Also, I am not a mechanic, so I am super cautious.

"Working with the ECU" is cool to me because I consider it a harder thing to innovate from within a set of rules. When you succeed, the solution can be more gratifying.

CarloSW2

rh77 -

I agree with this. In the ideal, I keep imagining something like the single handle faucet ball valves that mix hot/cold water:

https://home.earthlink.net/~cfg83/gas.../ballvalve.jpg

Obviously, there must already exist a better (larger) 2 into 1 valve mixer that could be (stepper?) motor controlled based on the IAT.

In the actual, I think that two seperate motor controlled valves is more practical in an engine bay.

CarloSW2

why not read the intake temps with this.
I have one like this but with one external temp sensor , it has 2 1/2 meters of cable and it woudl make a good intake temp monitor.

https://www.pethobbyist.com/petproduc....jpg&imgtype=2

WAI mod
 

My carbed 87 Civic manual says that it keeps the intake air at 100 degrees farenheight (it uses the typical old preheater air snorkel system).

Why not go to a junkyard and get an air cleaner assembly from a motor with a carb that already has the preheat vacuum operated valve and thermosentive vacuum bleed valve on it? You could relocate the vacuum bleed valve into the rounded part of the air snorkel just downstream from the hot air/cold air flapper valve. Then cut off the large disk shaped air filter section of the apparatus and plumb in the short section with the flapper valve and thermosensitive vaccum bleed just upstream from your air filter box- then connect to a manifold vacuum source and it should regulate itself from there onout. You may be able to "adjust" the WAI temp by bending the bimetalic spring of the vacuum bleed valve to try higher or lower WAI temps. You could probably also get the tin cover for the exhaust manifold as well and adapt it to your exhaust manifold. I think you ought to be able to get this whole assembly for $20 max. The thin metalized tubing that connects the snorkel to the exhaust manifold sheild is about $4 at discount auto parts stores (I bought one a month ago so that my stock preheat system would work properly).

Just my 2 cents..

I get a constant reading when i set the multimeter to volts rather tha ohms. I will monitor the temp and adjust the hose accordingly. I would love to rig up something with those 87 parts, maybe when i get some time. Good ideas floating around in all your heads.

I just threw on the stock intake and am getting between 87 and 98 degrees fahrenheit in 40 degree weather at 30-60mph with my grill block in place. With the engine warm, sitting still it is at 97 degrees. The grill block allows me to run the stock intake and achieve good iat it seems! :p

Woo for grille blockee.

I should work on my car since it'll be warm for a few days, but what to do...

Ben, we both need to do our belly pans. then we'll really have happy engines. I too plan on doing that one of these warm days. You gonna use coroplast? I was thinking of using the metal roof flashing since it can't catch fire or melt and is really flexible. we'll see, the coroplast IS free. :rolleyes: