gas for emission testing

[zmaster]

I really couldn't find any good threads that had what i was looking fr so heres a question. does anyone know what octane is best for emission testing? 87, 91, or 97 octane. I think my 280z will pass emissions, but i want to do everything i can to make sure it will be a sure thing for it to pass. rubbinng alchohol in the gas and all of those little tricks people do like that.

[woldson]

Get it running really well (as best as you can) and take it there with what ever tricks and post your results.

[Pete84]

My brother and I always run a tank of Chevron through with the extra Techron addative. Then warmed the cat up nice and hot with a good bit of driving, then dropped it off at the smog station. We try and schedule early in the morning so there isn't too much of a wait built up from delayings during the day. Hot cat helps alot!

 

Or so we are told and now practice.

[m4xwellmurd3r]

he shouldn't have a cat since he's not in Cali. IIRC only cali Z's had cat's till they were mandated across the country (my 78 has only lived in AZ, and has no cat)

 

Make sure EVERYTHING is clean, all connections filters and plugs.

[MJLamberson]

make it run very lean for the test... Also, there is this stuff at kragens the refunds double what you paid if you use it and dont pass... not sure if they live up to that because I never ad a chance to ak for the refund, my car passed. run bg44k through the tank before you smog, dont smog it with the stuff in the tank, just right after you run it through

[zmaster]

so you mean i can take my cat off since i don't live in california??? idf so I will gain a lot of horse power...or so i'm told

[Evan Purple240zt]

^ you have a cat on your car? ^

 

If so leave it on for the emissions testing, you will pass for sure if its in good shape.

 

Evan

[jkh280zx]

zmaster,

Good info here.

See: http://forums.hybridz.org/showthread.php?p=829852

Good Luck.

john

[rudypoochris]

make it run very lean for the test... Also, there is this stuff at kragens the refunds double what you paid if you use it and dont pass... not sure if they live up to that because I never ad a chance to ak for the refund, my car passed. run bg44k through the tank before you smog, dont smog it with the stuff in the tank, just right after you run it through

 

 

Why would you make it run very lean? If you made it run lean wouldn't you just fail the NOx test?

[Gollum]

Too lean is NOT good. 14.7 IS IDEAL.

 

 

There's a reason most new cars shoot for 14.7 at cruising conditions.

 

As far as which gas... well that's hard to say. Some say highest octane you can get, some say lowest. I don't think it makes a large enough difference to matter much. It's much more important that the engine be as hot as you can safely get it before testing. Heat produces NOx, but olders cars are more likely to fail from unburnt fuel than NOx.

[rudypoochris]

Here is a fuel table for a standard EEC-IV car. I think right under 14.7:! is where you want to be at. (Like 14.6 or so).

 

 

Note in the case of light load (say 15mph or 25mph rolling test) the AFR would probably be around 14:1 though. Interesting...

[Gollum]

You'd be surprised how much load they actually put on the car for that very reason. Those dyno drums have brakes that are applied to simulate the vehicles weight.

 

To me they seem to add more resistance than if the car was just driving at 15 or 25 miles an hour, but I don't have definitive data on the subject. I've smogged quite a few cars though.

[rudypoochris]

Oh, interesting!

[m4xwellmurd3r]

it depends if your state tests for nox or not. in AZ they don't. when I get my emissions slip, it only has HC and CO%, no nox. also, on the AZ mvd site i can't find ANYWHERE that shows the nox level limits.

if you have a cat, keep it though, it'll help

[zmaster]

UPDATE. I called thew bmv in my area, and got the phone number for my local emissions test site. This is EXACTLY what they said...." We do NOT test 1975 and earlier vehicles, you do NOT need emissions" I am so happy, and i even asked them if it would then be legal to take my cat off and they said "you could do whatever you want". so now I will be getting in a few months my 3 inch full exhaust without the cat. can anyone say more horses.

[MJLamberson]

but olders cars are more likely to fail from unburnt fuel than NOx.

 

well Thats why I said lean, not arguing with you, its just what Ive read.

[woldson]

Just to throw this out here, would meth injection change the results? Of couse you have to set it to run for that test?

[Gollum]

That's a good quesion woldson, because now that I think about it I know that alcohol burns a lot cleaner than petrol which is why everyone was talking about the possability of everyday cars running on it (note that ethanol is alcohol).

 

Now the term "ethanol" is huge and we don't think about it as "alcohol"... drag racers have been running alcohol in certain clases for decades now so it has it's advantages.

 

So I guess I'll do some research of methanol emission charts... Would be a really compelling reason to add meth if you had a car that needed to be smogged.