E85 calibration for emissions testing

[XfireZ51]

Originally Posted by Marc Haibeck

Jep,

As I understand it, the OE switching oxygen sensors switch at a ratio of oxygen in the exhaust verses the 20.8% in the air. That represents stoichiometric combustion of gasoline. The ratio is very different for stoichiometric combustion of ethanol, so a switching sensor calibrated for gasoline would not work correctly with ethanol.

Marc,

Yes you are correct. I think E85 stoic is around 9:1 while stock NB O2 is calibrated for gasoline with a switching point optimized for 14.7:1. It is possible to adjust the O2 switch point but I suspect not to the extent needed to accommodate E85. Same for the WB. As I presented at the last Gathering, I play w these values to account for the E10 w a stoic of 14.3:1 and for dealing w the increased overlap of bigger cams. I might read up on how this is being done on the C6. I imagine O2 sensors from flex fuel vehicles may be alternatives.

[XfireZ51]

Ron,

In some quick reading, it seems that it may not be all that difficult to go to an E85 tune relatively speaking. The O2 issue really isn't one w changes to the calibration. Some disagreement regarding corrosive effect of higher alcohol content but fuel pump and injector mods would be necessary for increased fuel flow. Corresponding cal adjustments for same as well as SA changes to take advantage of cooler fuel. The Flex Fuel vehicles have a sensor in the tank to measure alcohol content directly and use the correct values already in the stock calibration to optimize for fuel used.
Bin switching or flashing would be a good feature to have when implementing this for our cars. I'll work on getting a bit more detail. Live and learn.

[USAFPILOT]

I am interested in this as well. I failed emissions for NO2 on gas, but with a can of denatured alcohol in the tank the NO2 came way way under but my HC's came right up to the limit. Was able to squeak under on the second pass on my second test by 1 HC. I am using the stock tune, but the car now has SW Headers, High Flow Cats and a B&B 3" exhaust with X Pipe.

[rkreigh]

running on both injectors full time with both pumps running will provide more than enough fuel to do 25 mph which is all the car needs to do for the emissions dyno.

I "spiked the gas" with lamp fuel a few years ago and got the car down to 98 HC on a 99 standard, but that was also before the secondary flaps were removed.

my cats are definitely older and putting some BIG and fresh cats on the car is worthwhile to see how clean I can get the car "as is"

Tony's corvette shop certainly has the dyno and probably an exhaust gas analyzer, and hopefully working with Marc and sending the data captures back and forth we could get this done. I know Tony has a tuner also so they may be willing to have a go at it.

probably will be a bit pricey but worth it!

[Hib Halverson]

Oxygen sensors sense lambda and 1.0 lambda is stoichiometric combustion for any carbon-based fuel be it pure ethanol or gasoline.

If you're going to try to cal for E85, know that...

1) Stoich for E85 is is around 9.8 but can vary because pump E85 often varies between 70 and 85% ethanol. So, you're going to need to calibrate for a lot more fuel flow, even at part throttle.

2) E85 is corrosive to metal parts of fuel systems not originally designed for it. Also, it may attack rubber and plastic fuel system parts.

If the car is close on passing the IM240 type test, I'd put some known good stock cats on it, then go get the cats really hot just before you test. If your car cools well, drive around the block several times at medium rpm in first gear then pull right into the test bay. Or if the test station is close to the expressway, drive in fourth gear at highway speeds for five minutes then go test.

[rkreigh]

Originally Posted by Hib Halverson

Oxygen sensors sense lambda and 1.0 lambda is stoichiometric combustion for any carbon-based fuel be it pure ethanol or gasoline.

If you're going to try to cal for E85, know that...

1) Stoich for E85 is is around 9.8 but can vary because pump E85 often varies between 70 and 85% ethanol. So, you're going to need to calibrate for a lot more fuel flow, even at part throttle.

2) E85 is corrosive to metal parts of fuel systems not originally designed for it. Also, it may attack rubber and plastic fuel system parts.

If the car is close on passing the IM240 type test, I'd put some known good stock cats on it, then go get the cats really hot just before you test. If your car cools well, drive around the block several times at medium rpm in first gear then pull right into the test bay. Or if the test station is close to the expressway, drive in fourth gear at highway speeds for five minutes then go test.

I'll likely blend my own E85 to control it better. I'll likely try some fresh cats out but with the cams, no secondaries, headers, ect... I doubt I'll get the 390 to blow cleaner than 48 HC at idle.

hoping the E85 (or pure alchy for that matter) would be an alternative

if the car could be calibrated to run on it without breaking the bank I'm not too worried about the limited exposure the fuel system would have.

I'd only have it in there long enough to get through the dyno/sniff test

I'd warm it up on gas, drain it, swap fuel & memcal, and drain it out an hour later.

I'm only a block from the emissions test so it wouldn't even have to run that great as long as it can run clean, go 25 or 30 mph, to get by the dyno test.

any advice on folks in Northern VA that might be able to help out with this.

Tony's Corvettes is the only folks that might take this on, but I'm sure they would need some remote help from a better tuner.

I don't have secondaries in the car either.

[XfireZ51]

Part of the issue with idle is the overlap on the cams. This messes with the O2 sensors or should I assume you are running Open Loop?

[rkreigh]

Originally Posted by XfireZ51

Part of the issue with idle is the overlap on the cams. This messes with the O2 sensors or should I assume you are running Open Loop?

no doubt the overlap is a tough issue. it's running closed loop.

I had a LPE open loop chip previously, but that was before mark tuned it and removed the secondaries.

the cams are very streetable but not good at all for emissions, and I'm sure pulling the secondaries didn't help the situation either. but I sure love the way the car drives without them. throttle response is right now with the light flywheel and ti rods, and no secondaries to snap open.

I'll talk more to marc about this and see if he's interested. I think it could have some performance applications down the road for a high compression lt5 with a fully updated fuel system (pumps, lines, injectors, tune)

there is some power to be had with e85, especially with turbos!!

[XfireZ51]

Originally Posted by rkreigh

no doubt the overlap is a tough issue. it's running closed loop.

I had a LPE open loop chip previously, but that was before mark tuned it and removed the secondaries.

the cams are very streetable but not good at all for emissions, and I'm sure pulling the secondaries didn't help the situation either. but I sure love the way the car drives without them. throttle response is right now with the light flywheel and ti rods, and no secondaries to snap open.

I'll talk more to marc about this and see if he's interested. I think it could have some performance applications down the road for a high compression lt5 with a fully updated fuel system (pumps, lines, injectors, tune)

there is some power to be had with e85, especially with turbos!!

So if you are running C/L then the O2 sensors are detecting a false lean.
The ECM is commanding extra fuel. Unless you adjust the O2 sensor window for idle, it will continue to do that. Also, the proportional gains need to be reduced. A cammed motor is more unstable and the values used for a stock motor tend to exaggerate the instability. That's why you find cammed motors surging and why most will use Open Loop.
My motor has secondaries removed and using Pete's cams on the intake side only. Running C/L.

[Corbusa]

Guys excuse my ignorance , I do not understand how the emissions work . My question is . If all that is needed is to pass the test once a year could some one just rig up some sort of Fresh air injection right into the exhaust where the testing is being done? ( a 30 galon air tank that kicks on at a certain rpm?) would that throw off the readings and show cleaner air? or a spark plug in each exhaust pipe wired to a coil to burn any extra fuel ? sorry for the dumb questions .