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Emissions Tampering

Now listen... You know I live in Turkey and I own a 95 Coupe. Previous owner emptied the cats (how stupid to gain only a few Hp's). I had the car checked for exhaust emmissions (it is also mandatory here) and it passed the test quite well, I mean not marginal but well within the limits.

What does that tell you??? Maybe our emission standards are too loose or the cats are too much?

Cheers all,

Selim
 
Hi SS,
As mentioned in my last post, if a engine, any engine, is PROPERLY tuned and MAINTAINED it will not produce improper emissions.....that is why all the "Junk" such as Cats, computers, sensors etc. So when a car isn't maintained well the computer can controll SOME of the emissions and still meet the standards.....anyway that is my opinion. If it meets the specs I would not worry about it...just enjoy the ride. " Get in, sit down, hold on and enjoy the ride".
 
Tim,

I am very much doing that buddy. I love cruising with my Vette. It is a lovely peace of powerful equipment except for a few hick ups (such as vibration noise from the passanger side airbag area)...
 
SS,
Thanks for the reply....Happy Holidays from The U.S.A. and...."Keep On 'Vettin'"
Tim
 
Question: If I add some TPIS long tube headers and new y-pipe I lose my precats (my front Y is OEM just replaced last year). Is this illegal? Also would it affect emissions enough to impact the environment or cause me to fail the test? I just got my smog test here in Ohio and I read the results and my '91 is CLEAN. The only mods it has is a K&N, High flow main cat, and Magnaflow cat-back. The rest was good maintenance; plugs, cap, wires, rotor, egr, O2 sensor, fuel filter, etc.
 
It all depends on how good the tune is on the car. Technically I think it is illegal since it had precats, and you took them off, but I could be mistaken.
 
Mods?

If the car is basically stock headers and no cats and a free flowing exhaust my not see big returns in HP or times at the track. Now if the engine has been modified like head work, cam, and fuel delivery ,yes the free flowing emissions will give better results
 
Yeah..That's Me ...Mr. Nice Guy...I keep My Vette Mantained and.....

Don't mean to cross post but it is related to this thread...Sorry Mod's....
I'm just torqued off...!!!!!!!

The old spec from what I understand used to be C0% ... (1.5) now it's .05..!!!!!
Nothing like changing the ruels during the game..!!!!!:mad

And I take care of my Vettes emission System's. There all in tack and up to spec..:mad



http://www.corvetteactioncenter.com/forums/showthread.php?t=73004
 
If an engine is running right, open headers will really make no difference in real emissions level. The cat converts pollutants to sulpher. If an engine is running correctly it is BURNING the vast majority of the fuel rather than introducing unburned fuel to the atmosphere.

An engine that isn't running right but does have a cat, is polluting more than your engine with open headers assuming that it is tuned properly and in good shape.

Have a great day,
 
That particular discussion on Pobst's book is a pretty credible postion however, iMO, in general Mr. Pobst's book, Corvette Fuel Injection & Electronic Engine Management. is poorly written and full of technical errors. It's not a book I'd rely upon if I were looking for accurate information.

The book has been reviewed unfavorably here on CAC, on Amazon and Barnes and Noble.
 
Dyno ?

Has ayone done a dyno test after removing the cats and air pump ? Just curius I have been thinking of it myself and puting a true set of duels on it I would like to here it a little better when I open it up.
 
WhalePirot said:
and that's a maybe.

I ran my car for a short while with a 'test pipe' in place of the cat. There was little, if any, difference.

Bet you didn't run it on a dyno.
There's a good 20+ HP to be gained with exhaust modifications on an L98 motor.
C4s built before '91 had prohibitively high exhaust backpressure, some in the catalyst and some in the mufflers. While going to low-restriction mufflers would get a big boost in hp, removing the cats will give a further appreciable increase.

A single dyno test is worth a thousand seat-of-the-pants "feelings."
 
airman said:
Has ayone done a dyno test after removing the cats and air pump ? Just curius I have been thinking of it myself and puting a true set of duels on it I would like to here it a little better when I open it up.

Yes, lots of people have reduced the exhaust backpressure on the L98 motor, including Chevrolet themselves. When they tested with open exhaust, neither mufflers nor cats but with a straight pipe, they showed about another 30 HP.

The airpump, however, only draws about 1 HP max, so while removing it will give you an improvement in fuel economy (since your car only requires about 14 HP to drive it down the road at 60 mph), there won't be a measurable change in performance.
 
A properly maintained C2 corvette will not produce any more polutants than a brand spanking new C6. This has been proved time and again.

I hope you don't really believe that.
It's not even close to being true, your wishful thinking notwithstanding.
 
Redbob said:
Bet you didn't run it on a dyno.
There's a good 20+ HP to be gained with exhaust modifications on an L98 motor.
C4s built before '91 had prohibitively high exhaust backpressure, some in the catalyst and some in the mufflers. While going to low-restriction mufflers would get a big boost in hp, removing the cats will give a further appreciable increase.

A single dyno test is worth a thousand seat-of-the-pants "feelings."

Eh... I would believe the man. Whalepirot knows his stuff. I have a test pipe in my car for a while and I did not notice that big of a difference either, if anything I think I lost some top end since I don't have any back pressure.
 
Vettefan87 said:
Eh... I would believe the man. Whalepirot knows his stuff. I have a test pipe in my car for a while and I did not notice that big of a difference either, if anything I think I lost some top end since I don't have any back pressure.

Not in this regard he doesn't; I do.
Like I said: if he doesn't think he got an improvement from taking off his cat, I KNOW he didn't run his car on a dyno.

I did the exhaust design and development for the C5's, and all early development work was based on C4 L98s (such as I own) and ZR-1s.
I was the Engineering Manager, Exhaust Systems for Calsonic, and myself and my engineers put the exhaust systems on the flowstand, and ran the cars on the chassis dyno. As I said before, one dyno test is worth a thousand "feelings."

Ask Zolton Varga, the engineer at Chevrolet responsible for Corvette exhaust at the time - he'll remember me as "Robert."

And as for you last comment about having "lost some top end because I don't have any backpressure:" that just doesn't make any sense unless you've got a "speed-density" calibration; any car with a mass-air meter is going to run better with lower backpressure, unless your EGO sensor is failing to heat up.
And if that's the case, you put in a heated EGO sensor.
 
sothpaw said:
He's right, Bush is having the EPA make it easier on industry. They can replace some stuff as "rountine maint." and it will pollute more, but remain legal.

So if they can pollute more, why should I care?

You should have seen the 18 wheeler on I-95 the other day, trailing big, thick, streams of black smoke from the stack. Where's
the emission police for this guy?


In arizona the bus companies use natural gas... BUT its not better...(actualy worse) you just dont see the smoke that comes out...so people think its better than diesel...
(my dad works for the bus company)
 
Redbob said:
Not in this regard he doesn't; I do.
Like I said: if he doesn't think he got an improvement from taking off his cat, I KNOW he didn't run his car on a dyno.

I did the exhaust design and development for the C5's, and all early development work was based on C4 L98s (such as I own) and ZR-1s.
I was the Engineering Manager, Exhaust Systems for Calsonic, and myself and my engineers put the exhaust systems on the flowstand, and ran the cars on the chassis dyno. As I said before, one dyno test is worth a thousand "feelings."

Ask Zolton Varga, the engineer at Chevrolet responsible for Corvette exhaust at the time - he'll remember me as "Robert."

And as for you last comment about having "lost some top end because I don't have any backpressure:" that just doesn't make any sense unless you've got a "speed-density" calibration; any car with a mass-air meter is going to run better with lower backpressure, unless your EGO sensor is failing to heat up.
And if that's the case, you put in a heated EGO sensor.

Well this sounds pretty reliable but I thought there was kind of like a "law of diminishing returns" with back pressure on L98's. That is, after you eliminate some back pressure, there isn't really any more to be gained from eliminating more back pressure? Or something like that.
 
milehigreg said:
Emissions controls have made automobliles in general burn 80% cleaner.

Make that "99.9% cleaner" and you'd be right: it's not uncommon for a new car in a rathole like L.A. to have cleaner air coming out the tailpipe than what went into the aircleaner.

Some cities are just located such that atmospheric conditions are right for the photochemical process that makes smog: L.A., of course, which had "smog" before the white man even found it; Denver, sitting in that little bowl in the mountains; Phoenix, sitting in a HOT bowl surrounded by mountains.

For the rest of us, "smog" is just a word that gives bureaucrats a reason to try to run our lives.
Eff 'em.
 

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