327Chevy

Hi,

I am trying to get my car ready for inspection. I've got the AIR tubes welded onto the headers, and the AIR system conected to the headers and the new cat.

I had previously roughed in my VE tune with the EBL (w/o AIR injection at that time).

Now with the AIR system back on, VE learn is giving me a lot of +12%'s, which may be the o2 sensor picking up the air coming from the AIR injection into the header.

I didn't notice anything in the EBL instructions regarding disabling AIR for learning. (It does say to temporarily disable EGR and the vac canister while learning).

The EBL has decent instructions. Word searches on AIR, smog, volt, etc didn't find what I was looking for. Searches here on thirdgen - i did find something here on voltage offset for this situation, but that wasn't for EBL.

Rbob or others - any thoughts on how to tune with AIR installed and can someone please confirm that EBL supports AIR at all?

Thanks.

RBob

iTrader: (1)

The EBL doesn't support an AIR system. Although there are a few things that can be done.

One method is to leave everything in place and set up the AIR solenoids so that it always diverts.

The other method is to set up the solenoids so that air only goes to the cat. Then use the PE Mode active output to divert the air in PE mode.

RBob.

327Chevy

Thanks for the info but WOW - how did I miss that?

OK, if I run the air to the cat all the time, would this cause any unexpected issues? That may be the best way to go. I guess I could also run air to the passenger header all the time since only the driver header has the o2 sensor.

My plan with this car has been to build a strong engine, but tune it to the point that it'll pass emissions. I'm doubting if this plan will happen now...any ideas on how to make the EBL deal with the AIR injection upstream of the o2 sensor? I know one can tell EBL the stoich AFR. Could I tweak that constant to just offset the voltage difference the o2 is indicating due to the extra air in the exhaust? That seems over simplified...

Or I could finish tuning the VE tables with the EBL (AIR temporarily disabled), put a stock computer back in and burn a chip for the stock computer that mimicks the EBL-derived VE tables. The stock computer should run the AIR system. Disadvantages: 1. I haven't finished my idle yet, but if I want n-alpha, that would not be available in the stock computer, right? 2. Not sure if the stock computer has the feature to stabilize the idle with the ignition timing instead of just IAC position. 3. No rev limiter in stock computer. 4. Have to buy prom burning equipment or pay someone to burn me a chip.

Other ideas? In the meantime I'll be reading on thirdgen on how the stock computer handles AIR, voltage offsets, etc.

Thanks for the info.

RBob

iTrader: (1)

Best to keep it simple. Run the air to the cat except when in PE mode. Use the PE mode active output to set the divert solenoid.

An AIR system has very little impact on emissions. So you will still be able to build a strong engine and have it pass. It is more important to get items such as the spark timing, closed loop fueling, and IAC set up properly for clean emissions.

Too much timing causes high NOX and high HC
Too lean causes high NOX and high HC
Too rich causes low NOX, high HC and high CO

The IAC plays an important role in reducing HC on a throttle lift. This is part of the purpose of the throttle follower along with the delays before the IAC closes.

RBob.

327Chevy

Thanks for the info.

What would be the downside to just running air to the cat all the time? In other words, why not do that in PE too?

All I could think of is maybe the cat would overheat since so much unburned fuel would be reacting with the air in that situation?

RBob

iTrader: (1)

You got it. In PE mode the cat can overheat with air being directed into it. At the same time, no air and an excess of fuel will put the cat out. Which is why stock calibrations are so rich in the mid-range.

RBob.

ninetyone

iTrader: (2)

Was it hard to weld the air tubes onto the headers? What kind of metal are the headers? what kind of metal are the air tubes made from?

327Chevy

My hooker headers were regular carbon steel. The air tubes were also carbon steel.

Is it difficult? Depends on if you can weld. The headers do have to be off the car and on the workbench to do it. I used a mig welder