I have a '88 S4. I have to get emissions testing done one more time in St. Louis because they are doing away with testing next year for 96-older cars. This is a great thing except that I have to pass one more time.

Anyway, I thought I would give it a try without changing my current setup. I have:
Motorsport X-pipe/no cats/no air pump
stock GT resonators/stock S4 muffler
Performance chips
cam timing advanced
LH rebuilt this year
MAF rebuilt this year
new air filter/fuel filter/etc

So here is my baseline, but I did fail:

HC STD .80 gr/mi MEAS 2.6407 FAIL
CO STD 15.0 gr/mi MEAS 14.3677 PASS
NOx STD 2.0 gr/mi MEAS 5.0178 FAIL

What do you guys think is causing me to fail. I could throw the original cats and air pump back on, but it is alot of effort for a one time thing. I know that one of my GT resonators is coming apart and could be sucking in extra oxygen. I could seal it up with muffler butter for the test if this would help. How about changing back to my stock chips? Someone let me know if I am wasting my time with anything but throwing the old cats back on. Suggestions?

 

With no cats at all I wouldn't expect it to pass. Most S4's running clean are borderline passing with no cats but that is with no modifications at all. The chips and exhaust change the operating parameters of the engine considerably. You will probably pass easily if you throw some cats on, either our high flow ones or the factory ones.

 

If the chips are easier to change you could try that before putting the cats back on - you are high for both HC and NOx but only borderline for CO leading me to believe the issue is as much timing as it is fuel. I don't know, but I suspect the chips alter both the ignition timing and the fuel delivery. The cam timing change is an unknown (at least to me) so you might need the cats to eliminate the cam timing change influence.

 

My 88 S4 has a GT muffler, and no cats. It has always passed emissions testing easily. That would suggest that your problem lies in the chips, or cam timing.

 

Dave, how much are the performance cats again? Has there been any progress on the 32V cat-back. As you read in my previous post, my GT resonators are coming apart. Which mufflers are you thinking of using now, Flowmasters?

Michael, St. Louis does their testing on a dynometer type machine that actually drives the car through a series of increasing/decreasing speeds. Does Las Vegas do this or just the sniffer test up the tail pipe? Are your required numbers the same as mine? I hope so, you are giving me hope!

 

If you bought an "X", the cats are $299.95 a pair. We will be using either Flowmasters or Dynomax mufflers, we are just waitiing for our manufacturer to finish up another big job so he can get back to our stuff. We tested Spintech's but they were excessively noisy.

 

Dave,
You previously mentioned that you were doing the 16v cat-back first. Is this still the plan? Any idea when the 32v will be available?

 

I'm hoping the 16v catback will be available soon. We try to keep the prices down by sneaking in on their slack time, if we try to compete with their big jobs our prices go up drastically.

 

I finally got my chips swapped out. How long do I need to drive it for the chip change to take effect?

 

mmmmmm

I converted to gr/km so I could compare Mike's '88S4 with no cats to my 88S4SE with no cats. I guess Mike's test was a similar test to my IM240 - got to be a dyno type test to get results in gr/mile or kilometre.
pass meas
gr/km gr/km
0.50 1.64 HC US Mike
0.93 2.77 HC AUS Jon

9.32 8.93 CO US Mike
9.30 43.40 CO AUS Jon

1.24 3.12 Nox US Mike
1.93 1.38 NOx Aus Jon

At first glance it would seem that Mikes car is running lean - CO passes but Nox is high versus my car running well rich - CO way high and NOx low.

Both cars have high HC - mine is understandable, neat unburnt gas pouring out of the exhaust but Mike's running lean should be low?

In my reading about Aus standards I came across some government research into ways of cleaning up the older car population (Aus has a lot of older cars) and one of the conclusions they reached was that HC emissions from older cars could be reduced dramatically by renewing the charcoal canister.

As well as sorting the rich mixture, I'm now wondering if for the purposes of next emissions test I should disconnect the pipe from the charcoal canister to the inlet manifold, plug the manifold and let the canister vent to atmosphere.

And another question - if the engine is breathing some oil which at 130,000 miles it probably is, presumably that would also increase the HC figure - so would it be a good idea to temporarily vent the crankcase to atmosphere?

 

Well, I took it back for a retest after I swapped chips back to stock. It really did not make much difference.

Results:
HC STD .80 gr/mi MEAS 2.47 FAIL
CO STD 15.0 gr/mi MEAS 13.8 PASS
NOx STD 2.0 gr/mi MEAS 4.78 FAIL

Anyway, I bit the bullet and threw the cats and air pump back on. I unplugged the vacuum line to the air pump valve and convinced the tester to drive the car in 3 instead of D during the test. It passed easily.

HC STD .80 gr/mi MEAS 0.1051 PASS
CO STD 15.0 gr/mi MEAS 0.6055 PASS
NOx STD 2.0 gr/mi MEAS 0.1860 PASS

I guess if you have to do a dyno rolling test, a catless 928 will not pass. My car seems to be in a good state of tune with a MAF and LH less than 6 months old. Thank goodness this is over. No more emissions testing for 96-older cars starting next year!

 

Congrats! Amazing what the cats can do isn't it?

 

With OBDII type cats you might get away without the air pump.

 

Jon, I do agree with disconnecting the charcoal canister, no need to do this for just getting through emissions though.
With regards to venting to atmo with the crank case, I would only do this if you were converting to an air oil seperator and were prepaired to rerun all the lines and cap some spots under the manifold.

 

Lizard

My ideas re disconecting the charcoal canister and venting the crankcase were purely an interim measure to pass the emissions test.

The reason why - I imported the car to Australia (along with my wifes 90GT) Complicated reasons why but the GT came in as personal import (car owned and used for 12months + in another country) and is as such is free from most requirements other than basic safety - brakes and lights rust etc.

The 88SE I am trying to get through emissions came in under a separate rule (Pre '89 year of manufacture) which means it has to meet the intent of the OZ rules appropriate in this case for a car manufactured between '86 and '91. Most OZ delivered cars from 86 on had cats fitted to meet the emissions requirement, including OZ delivered 928s. However the Engineer that will certify the car is allowed some leeway in what he accepts, this includes accepting it without cats if I can show that it meets or nearly meets the actual standard for gases emitted as in my post above.

If I can get it to nearly pass the gas emissions test without cats, "No Cats required" will go on the import plate, and it will never need them in future. I'ld like to keep it without Cats if at all possible to keep it original as it didn't have them fitted as standard (also saves me money). Hence my desire to do eveything possible to temporarily reduce emissions. The test is purely a gas emissions test - no inspection of the vehicle - so I can revert everything back to normal afterward, and the subsequent engineering inspection will never know!