SMOG the results

[Steve Ekstrand]

Wild speculation... But the combustion chambers on that head are pretty notorious for getting carboned up. That can increase combustion temps. But didn't you say something about a new head?

Retarded timing can increase NO.

I'd rather have high NO than high CO or HC.

[Bob Pl]

Hi Steve,

Yeah, when the head was done that was all cleaned up, I saw it apart. Frank Fahey did the work & he's pretty meticulous.



It could be running lean, it has some sort of Dinan chip (carb legal) that so far as I can find out is really not supposed to do that much at all. But of course chips usually lean for power. Stochiametric etc.

It's always had the chip & always passed so far as I know.

I wonder if there is a "pass smog" chip that would rich it up a little. That should be ez to make & sell, a nice business project for someone. Lots of e36's needing smogs.

Any chip geeks listening? I will partner with you. Design it, get it made in China, sell it as an off road/test device, voila we make money. Sell to a hedge fund, retire & race cars.

[Will Kalman]

The CO2 value should be able to tell you if your mixture is right. I don't know what the value *should* be, however.

[Bob Pl]

The CO2 value should be able to tell you if your mixture is right. I don't know what the value *should* be, however.

Thanks Will,

No idea where I would even start to look for that, finding cold hard facts re BMW is kinda hit/miss I've found.

[Marshall Grice]

The CO2 value should be able to tell you if your mixture is right. I don't know what the value *should* be, however.

O2 will tell you if the mixture is correct.

[John Stimson]

Presence of O2 will tell you if there is not enough fuel.
Presence of CO or hydrocarbons will tell you if there is too much fuel.

If you have both, then the mixing or ignition isn't good.

CO2 won't tell you much unless you have a gross problem, because CO2 and H2O are the products of proper combustion, and gas analyzers are more sensitive to trace gases than to tiny fractional differences at full scale. It's easier to tell the difference between 0.0% and 0.1% of O2 or CO than to tell the difference between 33.2% and 33.3% CO2.

[Bob Pl]

co2 14.8

o2 0.0

The full report is linked on post 20 or 21. Maybe if you have time you could have a look?



I am learning a lot from you guys.

So this means I WAS/AM running rich?????

[John Stimson]

CO2 is different from CO. I thought your CO reading was pretty low, wasn't it?

[Bob Pl]

CO2 is different from CO. I thought your CO reading was pretty low, wasn't it?

.18 (low speed)
.06 (higher speed)

Sorry about that . I did pass high school chem a few decades ago.



So yes those seem low

[Max Likhterman]

Congratulations! Your motor runs perfect, that's just how they are, not low on CO/HC but not too good on Nox, they tend to run lean.All numbers look good, the way they should be. Our 99 M3 with 59K smogged the same. BMW's just tend to have higher combustion temps, and produce higher Nox. e36's in particular run 92C thermostats and just designed to run hotter than other cars.Your CAT is still good too. Next time you'll probably need a new CAT, but not necessarily. Nothing you can do to make it run richer ( and you don't want to I would think). So I would not worry about it.
Yes, they supposed to put a fan in front of the car, but with 70 degrees outside it would not matter much.

Max

[Bob Pl]

Thanks Max,

Next time would you think I should throw a new o2 sensor(s) in before (or after) the test? Maybe the sensor is getting "lazy". That costs less than a cat (although I know eventually a cat will be needed).

[Max Likhterman]

Well, you have about 2 years until the next test ( how many miles is that?), so I would not worry about passing the next test yet. But for better performance/fuel economy, replacement of an old 02 sensor is always a good thing, especially with gas prices going up...
If it is an original 136K mile sensor, I'd replace it. I believe it's an OBD1 S50 powered car and uses only one pre-cat sensor, less expensive than newer sensors for OBDII S52 motor. And if you want, you can get 4 wire heated BOSCH sensor and splice (solder) wiring from your existing sensor, saves quite some money. Most of these sensors are the same, wiring is different (length/connector).

Max

[Bob Pl]

Well, you have about 2 years until the next test ( how many miles is that?), so I would not worry about passing the next test yet. But for better performance/fuel economy, replacement of an old 02 sensor is always a good thing, especially with gas prices going up...
If it is an original 136K mile sensor, I'd replace it. I believe it's an OBD1 S50 powered car and uses only one pre-cat sensor, less expensive than newer sensors for OBDII S52 motor. And if you want, you can get 4 wire heated BOSCH sensor and splice (solder) wiring from your existing sensor, saves quite some money. Most of these sensors are the same, wiring is different (length/connector).

Max

Figure about 8-10k miles per year & pretty sure cat & o2 original.

It's s50 obd1 so far as I am aware. It would be interesting to put in (just) a sensor & retest to see if it cleans NO up.

THX

[Giovanni Jaramillo]

Congratulations! Your motor runs perfect, that's just how they are, not low on CO/HC but not too good on Nox, they tend to run lean.All numbers look good, the way they should be. Our 99 M3 with 59K smogged the same.

Bob, Max is right. Even on my E46 M3 I smogged it and it passed (just shy of almost failing in one category) and that's just how they are. Even off the showroom floor dealers have said they run lean.