Well, I failed emissions again. CO and HC were exceptionally low. HC was .62, limit 1.2. CO was .31, limit 20.00. NOx is what I failed however, 3.45, limit 2.50. My EGR is functioning properly, and I have a fresh Catco cat on there. All smog equip is intact and I'm running a stock .bin. I remember Glenn commenting on how quickly the car goes into open loop with a prolonged idle so I blipped the gas a few times before backing onto the rollers. My timing was stock, and its in good tune. BTW its a 91 Z 305 TPI.

I'm at my wits end here. I'm thinking of running a 160 stat to lower cc temp's, and maybe that will richen the mix a bit. I don't have chip burning abilities yet so I guess I have to fool the computer into richening it up a little. Does anyone have any ideas? Tim, how was your NOx?

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-Jason M. 1991 Camaro Z28

 

Jason,

Try richening it up. This will increase the HCs but will reduce the NOx. Try 14.4. Go lower if necessary.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Thats what I'd do if I could burn a chip. Would running a lower temp t-stat or putting a resistor in place of the CTS make the ECM run in cold start enrichment, or would that run so excessively rich that it could cause me to fail HC's?

EDIT: I should add that I'm just trying to get a sticker, not work my 305. This engines coming out in 3 months and I'll have plenty of chip tuning with the new TFS headed 350! Maybe I should just invest in PROM stuff now so I can change the stoich A/F ratio and get this hog to pass...

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-Jason M. 1991 Camaro Z28

[This message has been edited by Jason M 91Z (edited September 20, 2001).]

 

A colder T-stat MIGHT work, provided you have the fans working to keep the engine cooler.

But, I would get the equipment NOW. It is far easier to start learning on a stock engine than a modified engine. With a stock engine, you are just "tuning". With a modified engine you will face the issue of "trying to make it run right". Learning is far easier on a stock eprom.

 

With that high of NOX, your engine was probably running HOT. Make sure your engine is not hot when they run the test...warm is good. Wire your fan(s) so that they are running during the test to keep it from heating up. I had the same problem, and that was the only thing I needed to change to pass.

One other note: You can have a functioning EGR and still have it be clogged. Make sure you clean out all your EGR passages (especially with the TPI), as they can quickly become clogged.

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Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
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