Twin Plug California Smog in an 86

[johnca]

Before I make decisions on which way to rebuild my engine, I'd like to know if twin plugging my 3.2 build will cause smog failure. Via searching, it looks like lots of folks on here have twin plug engines in California but unsure about smog. Can anyone enlighten me ?

[faapgar]

Lets see.More complete combustion?Probably not.Ciao Fred

[darrin]

no first hand knowledge, but seems clear from prior comments that CA smog goes pretty deep into the weeds with visual inspections and that since twin plugging would be an obvious visual change, it would be foreseeable that doing so would cause it to fail visual. Similarly, seems to me that folks that drive modified cars in CA that are subject to smog tests have other "handshake" arrangements in place to "handle" these issues.

FWIW, I chose not to go the twinplug route when I rebuilt my 3.2 to a 3.4 using mahle motorsports 3.4 p&c -- as I was advised that twin plugging a motronic engine would yield minimal additional HP over a single plug 3.4 but would add several thousand dollars to my build cost. I'm VERY happy with the extra "butt dyno" power that the my 3.4 conversion's added displacement and compression has yielded while remaining Colorado smog legal (I'm still using the factory headers with a M&K active cat).

[salayc]

Originally Posted by darrin

no first hand knowledge, but seems clear from prior comments that CA smog goes pretty deep into the weeds with visual inspections and that since twin plugging would be an obvious visual change, it would be foreseeable that doing so would cause it to fail visual. Similarly, seems to me that folks that drive modified cars in CA that are subject to smog tests have other "handshake" arrangements in place to "handle" these issues.

FWIW, I chose not to go the twinplug route when I rebuilt my 3.2 to a 3.4 using mahle motorsports 3.4 p&c -- as I was advised that twin plugging a motronic engine would yield minimal additional HP over a single plug 3.4 but would add several thousand dollars to my build cost. I'm VERY happy with the extra "butt dyno" power that the my 3.4 conversion's added displacement and compression has yielded while remaining Colorado smog legal (I'm still using the factory headers with a M&K active cat).

CA does have a visual inspection but it's limited. They're supposed to check for all smog equipment in place and working, a CA or 50 state emissions sticker (if applicable) and for a CARB compliant Catalytic Converter. I've had lots of exotics and modified cars and never had a problem with the visual inspection.

[Flat Six]

Unless you live in one of the few really rural counties in the People's Republic, you're subject to annual smog testing. If all you're outwardly changing is 6 to 12-plug, then you might get past the visual inspection. But -- correct me if I'm wrong -- if you build your engine such that you need twin plugs, you probably also will have to change induction and exhaust, in which case those items will cause you to fail the visual inspection. Regardless of the results of the tailpipe sniffer on the roller dyno, you still fail.

[FrontGarage911]

If it is a modification that is not original to the car's year/make/model it is a fail for CA smog.

[Joe Bob]

Depends on if the tech is smart enough to spot it. Best to call the BAR and DMV to discuss the issue.

Personally, an engine swap is a less slippery slope.

[spyerx]

Will fail visual.
Your build will depend on if it fails sniffer.
Most techs will not notice
But start removing cats, or a itb induction or things that look like mods
Expect deeper inspection
High lift cams can cause fail depending on tune

[famoroso]

It's at increasing risk of failing the visual. More so today than yesterday. More so tomorrow than today. Also, if caught, you run the risk of getting flagged in CA's system. In which case your car will undergo increased scrutiny for emissions tests going forward.

See what happened to this poor guy..
https://bringatrailer.com/listing/2001-porsche-911-turbo-124/
...he ended up selling the car to someone from out of state and taking a loss as opposed to going through the mental and financial anguish of removing all the Ruf goodies to return the engine to stock configuration.

I have a perfect example from last week. A local friend with a stock 997 GT3 brought his car to the same emissions testing shop that he's successfully used the past four years and they failed him visually because the tech thought the cats looked different (from the pictures the tech is compelled to compare to). They weren't different. The friend brought the car to a different testing shop and passed. Point is, the procedure is a PITA, even for newer cars and is clearly fraught with risk in CA. Not worth the dice roll in my opinion.

For my 3.4 build, I diverted budget from a twin plug setup and put it towards Carillo rods, lightweight flywheel, spring centered clutch disc and aluminum pressure plate (G50). As a result, we took 20 pounds out of the reciprocating & rotating assembly. Stealthy / invisible. That's a benefit that can be felt at all times, regardless of induction / injection / ignition / exhaust setup. Win / win in my book.

[dannobee]

Unlike others here, I actually was a CA licensed smog technician for 30 years.

Do you really think that a smog tech, any smog tech, couldn't tell the difference between a distributor with six spark plug wires and a single coil and one with twelve spark plug wires and two coils? And what about the ignition timing? If it varies from the stock setting, it's a functional check failure too.

There was a thread on similar CA Smog Test issues a few months ago where I commented on how it all works.

https://forums.pelicanparts.com/porsche-911-technical-forum/1070716-bitz-efi-ca.html

[johnca]

Thanks everyone for the info. Looks like single plug it is

[famoroso]

Originally Posted by dannobee

Unlike others here, I actually was a CA licensed smog technician for 30 years.

Do you really think that a smog tech, any smog tech, couldn't tell the difference between a distributor with six spark plug wires and a single coil and one with twelve spark plug wires and two coils? And what about the ignition timing? If it varies from the stock setting, it's a functional check failure too.

There was a thread on similar CA Smog Test issues a few months ago where I commented on how it all works.

https://forums.pelicanparts.com/porsche-911-technical-forum/1070716-bitz-efi-ca.html

You're the man. Loved your responses in the linked thread. Thanks for sharing your expertise.

[FrontGarage911]

If anyone is in the SF East Bay that needs a legal smog place, I'm an owner and operator of 17
years.