Here in north Texas we now have chassis dyno smog testing done when getting a vehicle inspected. I have always heard that a modified engine with no converters could burn as clean as a stock one with cats, but have never had a chance to test the theory.
Apparently there is some truth to that. My truck has a roller 351 with a stock intake, GT40 heads, E303 cam, hedman headers, a gutted two into one (2 1/4" into 3") preheater and a single 3" pipe, and a (3" into dual 2 1/2" exit) flowmaster with dumps. I have zero smog equipment sans an air pump that isn't connected to anything on the engine or exhaust.
After running a high speed and low speed load test, it passed with emmisions numbers well under the specified regulations. I was suprised and very happy with the results and I just wanted to share my experience.

 

You say you have zero smog equipment, but did you plug or disable the EGR, PCV, EVAP, O2 sensor, etc. As long as the stock computer ignition and fuel injection system is running at peak efficiency, the cats should have little to clean up. Does Texas have a NOX standard, or only CO and HC?

We have similar testing here in this part of California, but because my loaded truck is over 6000 lbs, they did not put it on the dyno.

Jim

 

Do they give you a printout with the numbers? I keep mine just to shut up the inlaws that talk about emissions being "double" etc on trucks suv's etc. I always tell them "2 times -0- is still -0-", as the numbers I get on my 85 e150 and the other junkers we have are just about zero.


You can't pass w/o cats in CA, as they measure CO vs CO2. You'll never pass that without a cat. Nothing like these guys who got the deal of the century on an older BMW only to find it's got two dead cats. Or the pot-metal motors passing enough oil to poison the cats.

 

Yeah, my printout has a 25mph and 15mph test, these are the 25mph results:
25mph test
-------Standard------Current reading
HC------137------------89
CO------1.52-----------1.30
NOX-----1406-----------1137
Dilution-->6.0----------14.5

 

Ok, I spent too long doing this the first time and it didn't take. Trying again.

85 E150 6, mt, 25 mph tested 12/2000

---------standard------------reading

HC.......168max/52average........68

CO%.....1.06max/.17 average....---.04

NOXPPM 1103max/387avg, ------950

No Dilution measured.

97 Olds Silly minivan, tested 1/01

HC ----81max/5avg.--.......... 1

CO%---.84max/.03avg---- -0-

NOX ---785max/106avg-------...-0-


98 exploder 4x4 test in park,

657rpm

HC---100max/17avg................1

CO%---1max/.00avg.................000

2500RPM

HC----170max/12avg...............3

CO%---1.00max/.10avd...........-0-


No NOX tested on exploder.

Cats kill the CO, efi and cats kill the HC, EGR & compression lower NOX.

So you would fail CO, probably pass the HC, and fail the NOX unless the standard went up depending on year, model.

You would fail visual, though, as they still have to see everything in CA. But heck, you're darn close, but of course, you put out:

130% of the CO,
85 times the HC, and
and 3 to 10 times the NOX

of whatever standard I choose to compare you to of these 3 vehicles, which would be the way the tree-hugger crowd would say it.

Breath deep.

 

On the visual, I have a cat and smog pump in place. The pump is routed to dummy lines and the cat is empty, so it actually passed our visual as long as they don't pull out the shematic for the truck.
Looks like I would be over on Cali standards, though.

 

If you have that stuff and pass visual, then the next step would be to "prove up" that you spent so much money to make it pass, and if it still blew those numbers, you might get an exemption.

 

Ah, I didn't know they would pass a vehicle that wouldn't pass if you have relpaced everything.
Oh well, it passes here!