1993 LT1 Emissions

[LastOfTheV8's]

what are the emissions on a 1993 c4 ? Or what should they be ? I am wondering if mine will pass a test here in ireland, it can't exceed 200ppm hydrocarbons, and 0.5% carbon monoxide at idle.

 

[twiget]

Welcome to the LastOfTheV8's. I'm going to put this post in its own thread. That way it will be a little more visable.

I do not know what the emissions requirements were for cars in 1993. Are there automobile shops in Ireland that you could take your 'Vette to and have it tested before you get the official test done?

Jason

 

[Stuart]

I had mine tested in March of this year.
At a throttle reading of about 1318 RPM my car registered the following:
HC ppm 4
CO % 0.02
NOx ppm 149
CO+CO2 % 15.0

FYI
At a throttle reading of about 2029 RPM those numbers go up to:
HC ppm 9
CO % 0.03
NOx ppm 287
CO+CO2 % 14.9

 

[LastOfTheV8's]

Thanks for that! gives me a little more confidence in her chances of passing the emissions test here. Your vette certainly would anyway, what mileage do you get stuart ? Mine is poor enough, 14mpg urban, 22 on the highway (about 75mph)..

 

[LastOfTheV8's]

Thanks Jason, I guess I should at least try an auto shop first, although knowledge of american cars here is non existent!

 

[Hib Halverson]

If youre car is running nicely, I'd go test. My guess is you'll pass easily. The standards you cited are way above what the car ought to run if it's running properly.

 

[LastOfTheV8's]

Thanks Hib. I had the water pump and optispark replaced just this week, she seems to be running fine, although at a slightly higher temperature than before, now at 93 degrees Celsius (i think about 198 degrees F ?) rather than 89 which she used to run before, any ideas why this change would occour? The mechanic (an american who actually owns 2 C4 vettes and works here in ireland) who worked on her says that the cats were clogged and will take a while to clear again. I was just wondering would this cause the engine to run hotter ? Or have I missed something obvious here..

 

[Hib Halverson]

4°C difference is nothing to worry about. In fact, the thermostat opening value is between 88.9°C and 90.6°C so your coolant temp is right there where it should be, however, you should always do an annual check of the area inside the cooling stack to make sure there is no debris on the fact of the hvac condenser or the radiator. You have to remove the upper cooling system shround to see between the hvac and the radiator.

If your service tech said the cats are "clogged", I'd hold-off on the emissions test until you are sure they are clear. I'll add that, typically, cats that are truly clogged do not "repair" themselves. If the engine runs well under high load and at high rpm, it is unlikely the cats are clogged. If they are temprarily "clogged" you can clear them by running the engine hard.

 

[LastOfTheV8's]

Thanks for the info, I really would be lost without the expertise found on these forums. And my vette probably would be on the scrapheap. I appreciate you taking the time to reply in depth like that. I see you have a 95 ZR1 ? How does it compare with your Z06 to drive ? Which do you prefer ? And what engine is in your 71 coupe ? 454 big block ? I read somewhere that there were only 90 of those cars built in 71 ? They must be some of the most sought after corvettes..

There is another aspect of my vette's behaviour I want to ask about, as a rule I keep an eye on the digital coolant guage while driving and as I mentioned she always sat at 89 degrees before, but once or twice suddenly dropped to 85 during 'normal' driving at around 55mph... the thing is the car would accelerate noticeably harder when the guage indicated a lower temp.... was I imagining this ?? I suspect so! I have noticed that when driving at 70 or 80 mph the engine runs at a lower temp than at 40 or 50 mph, but in this case the car just seemed to get cooler by itself... Does any of this make sense ?? ;P

 

[Hib Halverson]

Thanks for the info, I really would be lost without the expertise found on these forums. And my vette probably would be on the scrapheap. I appreciate you taking the time to reply in depth like that. I see you have a 95 ZR1 ?

Yep. I do.

How does it compare with your Z06 to drive ? Which do you prefer ?

One easy question, one tough question. The Z06 drives nicer, mainly because it's lighter and handles better. Also, it's easier ingress/egress. As to which I prefer...depends on my mood. The Z06 only revs to 6800 by the LT5 goes to 7000 and the sound of the four-cam V8 is unique. I like the ZR-1 on long drives because it carries more stuff.

And what engine is in your 71 coupe ? 454 big block ?

Basically, yes. It's actually a 460 because of oversize pistons.

I read somewhere that there were only 90 of those cars built in 71 ?

BBC production in 71 was 5285--188 high-perf versions and the rest low-performance.

They must be some of the most sought after corvettes..

Big-Blocks are popular, no doubt

There is another aspect of my vette's behaviour I want to ask about, as a rule I keep an eye on the digital coolant guage while driving and as I mentioned she always sat at 89 degrees before, but once or twice suddenly dropped to 85 during 'normal' driving at around 55mph... the thing is the car would accelerate noticeably harder when the guage indicated a lower temp.... was I imagining this ??

Hard for me to say without driving the car. You might see a slight increase in perforamance with lower coolant temp but I'm not sure what the spark tables do when coolant temp changes

I suspect so! I have noticed that when driving at 70 or 80 mph the engine runs at a lower temp than at 40 or 50 mph, but in this case the car just seemed to get cooler by itself... Does any of this make sense ?? ;P

C4s run slightly hotter when the trans is in overdrive (auto) or sixth gear (man) and your are going 40-50. This is because the engine rpm is so low that flow through the cooling system decreases slightly.

 

[LastOfTheV8's]

Thanks once again Hib. I read an article you wrote in 1996 looking back on the C4, (for the idaho corvette page) it's interesting that even with the (well deserved) mention of the faults inherent in this generation vette, and despite also how eagerly anticipated the C5 was at the time; the fifth generation vette didn't make it into your collection Or at least, you don't have one today. Did chevrolet forget to cater to the 'lunatic fringe' ? Kidding, I enjoyed the article of course.
I have been advised to fit a 'superchip', which would allow the cooling fan to run at a lower temp, rather than the 210 to 220 degrees or so it seems to operate at now.. would it be pointless to change the chip without also fitting a 'performance exhaust' system? I have heard how temperamental and troublesome c4 computers can become.. maybe I shouldn't mess with it at all ?

I realise I am getting way off the subject of this thread, but I have just so many questions and find it difficult to navigate around a forum with such a vast amount of information...

 

[Hib Halverson]

Thanks once again Hib. I read an article you wrote in 1996 looking back on the C4, (for the idaho corvette page) it's interesting that even with the (well deserved) mention of the faults inherent in this generation vette, and despite also how eagerly anticipated the C5 was at the time; the fifth generation vette didn't make it into your collection Or at least, you don't have one today.

My 04 is a C5.

Did chevrolet forget to cater to the 'lunatic fringe' ? Kidding, I enjoyed the article of course.

I think that the C5 Z06 was about as close to a lunatic-fringe Corvette has GM has come since the 1960s and early 70s, and...it's the last time it'll get that close, too. With GM, now, for the most part, a Government-supported jobs program, you can bet that cars for a narrow, performance-oriented audience are a piece of history.

I have been advised to fit a 'superchip', which would allow the cooling fan to run at a lower temp, rather than the 210 to 220 degrees or so it seems to operate at now.. would it be pointless to change the chip without also fitting a 'performance exhaust' system?

I disagree. While, you'd gain some performance with the low restriction exhaust, you won't loose anything by adding the Superchips calibration without the exhaust. You can just add the exhaust later.

I have heard how temperamental and troublesome c4 computers can become.. maybe I shouldn't mess with it at all ?

They are no tempermental and troublesome than any other PCM. Disconnect the battery or pull the ECM fuse then change the chip. Reconnect the battery or reinstall the fuse then go for a drive. The car might run a little funny in the first mile or so but after that, it'll be fine. No big deal.

 

[LastOfTheV8's]

Ah you have a C5, I guess the car lived up to the hype after all
Thanks again Hib, I see no reason now not to fit a new chip, other than 'if it ain't broke... etc' I will see to passing the emissions test first, the testers here are real nazis about it.

 

[LastOfTheV8's]

exhaust, you won't loose anything by adding the Superchips calibration without the exhaust. You can just add the exhaust later.
They are no tempermental and troublesome than any other PCM. Disconnect the battery or pull the ECM fuse then change the chip. Reconnect the battery or reinstall the fuse then go for a drive. The car might run a little funny in the first mile or so but after that, it'll be fine. No big deal.

Can you recommend a particular brand of chip? I am superstitious to the point of panic at the thought of modifying anything on my vette's engine management, feeling very secure with all things OE. That said, I value informed opinions and the vast experience of the owners and writers contributing to this forum.