spyder348

Ok so my 87 930 has no cats and I need 1 more emissions test before its exempt. I entered in my 930 registration and ran my 87 944 na. Very close but nox is too high. How can I bring down nox without boosting hcs and co. My ideas so far were fuel system cleaning methanol or water injection using highest Octane or even some Alchohol in the gas tank. Please help my 930 tags expire this month.

johnsjmc

If you are very close and can test it easily to see the effect. I would try retarding the timing a couple degrees. Nox is formed during high temperature combustion.

spyder348

I know. It's just what steps should I try to pass. Retarding timing will reduce nox but raise hcs. Sorry I'm not on 944 forum I don't get along with those people. They seem very angry. Maybe because the 0 to 60 time is 9 sec. Lol. Anyways ill try Retarding the timing and creating a vac leak. Maybe inject some washer fluid. It's cheap methanol.

johnsjmc

A vac leak will probably raise Nox because a lean burn will be hotter. Yes a change in timing will affect HC .You are trying to find a point where the curves cross and all 3 gases are below the limits. You might have room to raise your HC and CO a little if it lowers your Nox. Alcohol in the fuel might help or make it worse I am not sure.The aditives sold to help pass the test can also lower the emissions slightly but don,t count on a major drop with any of these suggestions. The conventional strategy is to use exhaust gas recirculation.(a hot cam can act like EGR.,but the stock turbo cam isn,t very wild). Tinker with the timing and A/F ratios.Then a 3 way cat.

spyder348

Maybe ill register in a no emissions state for a year

johnsjmc

How far from passing are you? Can you post numbers as tested and required limits?

spyder348

I will asap

Ken D

If I understand you correctly, you are using a 944 as a surrogate for your 930 for emissions testing (definitely not legal).
You cannot adjust the timing in a 944. Has its DME been chipped? If so replace with the factory chip.

911rudy

I have an '87 930 also and I have always used, successfully, the old trick of running the car on turbo for a sprint just before going into the test. The theory is that the exhaust becomes so much hotter than a normal car that any gases wanted or not seem to be cooked. Anyway I have done this several times and have always passed the tests in Ga. My car is pretty normal with no fuel mods.

Garrison

Here in Colorado, my 930 had a rough time at first in passing emissions and it was all due to the WUR. Once we replaced it, the car passed with flying colors.

A trick I have seen people use is to put a bottle of "HEET" into the tank right before the emissions test. Not sure how it helps, or if it will work for you, but I have seen cars that have failed, go back and take the test again with nothing different except the "HEET" in the gas tank.

johnsjmc

I wondered about the 944 surrogate thing also but thought since the poster was talking about passing without his cat we were testing the 930. What car are we talking about testing? A modded 930 or a stock 944?

A930Rocket

I entered in my 930 registration and ran my 87 944 na.

My understanding is that he entered his 930 VIN and ran his 944 on the dyno or sniffer. BTDT.

spyder348

Hey guys been so busy but yes using my stock 87 944 as the tester for the 930 registration. The limits are very close on these two cars. Seems like nox failed previously. I was running 87 Octane as well. I ran a bottle of g2p through. Checked the 02 and it is lazy. I'll replace that tom. Along with 93 Octane. Drive it hard for 30 mins. And retest. Have a gallon of alky in the trunk if it doesn't work but that stuff scares me and is a last resort. Can't find any vac. Leaks. Also sucks that the n/a does not have the timing fqs switch like on the 951s.

Ken D

Actually it does, I don't know if that alone will get you to pass the test. Here are the settings.

http://www.motronic.ws/fqs.htm

spyder348

I'll be pulling the dme out tom and hoping to see the switch. Thanks for the post. Put the new 02 in and no more fluctuating idle. Means it did something.93 is in the tank. I'll run it in the morning when its coldest out. I'll do one test then if it doesn't work start with fqs position 4.