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CA Smog Inspection Definition Possibilities?

Post by bird93sc » Tue Feb 16, 2021 2:14 am

A humble hello to all. I am extremely new to the Tune world. I am tech savvy and mechanically capable however i know nothing about vehicle electronics, sensors & such. maf curves, fuel injection voltage/spray, etc. etc.
I am old school Rotary Engine Holly Electronic Ign. Exhaust. Physically Tuned. Simple Sweet.

Now i have 93 Super Coupe currently NOS refurbished crank cam sensors dis pcm idle throttle sensors coil pack wires temperature sensors etc. Everything is fresh and Factory Stock.

Goal is a 13 sec 1/4. Bolt on mods. No more no less. Roller rockers and ported sc cai exhaust is good enough approx 300+/- hp ideal end setup.
First things first. 100%carb compliance & legal Stock setup Failed CA Smog. Nox way high.

Question is can I put a Definition in place that would assist in a Passing Test.
I have QH & F3 chip burn R/W hardware/cable. I Bought BE EEC dongle & sailorbob GSALl strategy Has NO Definition yet.
It is auto tran U2Y EEC IV the 93 SC is kinda on its own in between paired 94/95.or 92/91? I am a DIY person and financially depleted and irresponsible.
Sorry so much bio details. I am excited to find this "temple" of ford gurus I hope this is the place and people I have been seeking? Thank you all for your time & consideration.

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Re: CA Smog Inspection Definition Possibilities?

Post by cgrey8 » Tue Feb 16, 2021 7:44 am

NOx high suggests you are running either slightly lean during the test (too lean for the CATs to overcome) and/or your ignition timing is just too high.

Assuming your setup is testing with Closed Loop fueling, usually you can knock NOx way down by doing nothing but retarding the timing during the test. I don't know what your testing RPM/Load is, but my guess is whatever it is, you could setup a "smog" tune that never commands anything above, say 15 degrees and that would likely take care of it. If you were really concerned that even that wouldn't be enough, drop it to 10. Quite often, this is all it takes particularly if all other aspects of your Closed Loop control strategy are using stock values. If you are running Open Loop for some reason, you basically have a glorified good luck passing with that.

If the CATs are brand new, this should be enough. CAT technology is FAR more efficient than it was 20-30 years ago WHEN COMBINED with Closed Loop fueling. Although I've heard of people retarding the heck out of engines and getting them to pass with no CATs! I can't say whether that's true or not. It's just what I've heard. However I can say, from personal experience, that when I had my high compression 331 smog tested, I proactively retarded timing to 18, and it had no problems passing. Numbers were WELL below allowed levels for my year/make truck.

The other thing you could do IF the above didn't work is check your HEGO Bias table to see if it is commanding lean (positive) values at the testing RPM/Load. IF it is, zero-out the bias. I doubt you'd need to rich-bias it any since the stock HEGO switchpoint is already .42v. Being a 93, you might already have rich-bias (negative) values in your HEGO Bias table. But if the above didn't work to get it low enough, then this would be your next move. However, I wouldn't recommend doing this unless the above failed. You might over-compensate and cause it to fail on the rich side (high HC and CO) especially if you don't have a smog pump. Smog pumps help old-gen CATs to digest HC, which becomes an issue with wide-duration cams.

And of course if you had access to E85, that would be another route you could take. Either retune for E85 or blend yourself up an E40ish blend and test on that. Ethanol burns cooler than gasoline does, so that alone should get your combustion temps lower to avoid the NOx production. But this shouldn't be necessary if you only have mild mods and an emission-legal cam.

Another "gimick" people do is play around with injector timing. I don't have any real world reason to believe that this helps anything. But people do it with various theories and results. It might help, it might not. I don't really know to be honest. The only theory that makes any sense to me is delaying injector firing until AFTER the exhaust valve has completely closed to ensure you aren't firing fuel into air that's slipping out the exhaust while the intake and exhaust valve are both open at the same time. It's an interesting theory, but I'm not sure how applicable it is to relatively low RPM/Load conditions. Exhaust scavenging is a condition that happens due to the momentum of LOTS (high load) of FAST-moving (high RPM) exhaust through the exhaust system creating a vacuum in its wake as the exhaust flow from the cylinder slows. But it's my understanding this only happens under HEAVY load and high RPMs. At lighter RPM/Loads, it seems more likely to me that exhaust is actually being sucked back into the cylinder. With my stock Explorer 302 with dual exhaust (the engine I ran before replacing it with the 331), one of the things I could do is take a rag and hang it over my tailpipe while the engine idled. You'd think the exhaust would be a smooth stream of gasses flowing out pushing the rag outward. But what I noticed is the rag got sucked into the exhaust an inch or so every cylinder fire before being blown back out. If there's that much reversion at the tailpipe at idle with a STOCK cam that has relatively low valve overlap, I have to believe there's still a fair amount even at cruising RPM/Loads. Increase the overlap with a higher performance cam and I can't help but believe this condition gets worse for lower RPM/Loads. Your setup may show something different. So if you read about injector timing being used to pass emissions, I wouldn't bet on this being the thing that makes the real differences. This is kind of a something-to-try last resort when all other mitigation strategies ALMOST have you passing, and you just need that little extra something to get your numbers under the limit.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA


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Re: CA Smog Inspection Definition Possibilities?

Post by MarcoAmara » Fri Sep 17, 2021 1:30 am

Tech savvy here.Yeah injector timing makes all the differences.

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