EPA Emissions Regulations Key Factor?

[Rob]

In my continued effort to stir the pot some more here, as read on a GM forums web site, supposedly the current LS7 engine in the Z06 will not pass emissions in another year or two due to stricter emissions regulations coming into play.

As a result, GM had to find an alternative for the Z06 - hence, an engine smaller than 427ci, and supercharged.

What do you think? Fact or fiction?

[GerryLP]

It would almost be fiction, except for that time in the early 1970's, so at least there is precedence already established.

It is hard to believe that given the advances in engine and emission controls design, that it would be hard to retrofit the LS7 engine to meet the new requirements.

Is current technology stuck in a plateau?

GerryLP

[Rob]

Originally Posted by GerryLP

It would almost be fiction, except for that time in the early 1970's, so at least there is precedence already established.

It is hard to believe that given the advances in engine and emission controls design, that it would be hard to retrofit the LS7 engine to meet the new requirements.

Is current technology stuck in a plateau?

GerryLP

Mmmm....but one of the reasons why the ZR-1 met its demise is because the LT5 engine would not pass upcoming stricter emissions regulations without a significant re-engineering that would have cost more money than GM wanted to spend - especially in light of the 300 hp LT1 engine debuting in '92.

[Evolution1980]

What is the physics in the idea that adding additional cylinders or bore or stroke increases emissions? (or the converse)
Or is it just simple math? If one cylinder produces 1% emissions, then eight cylinders would produce 8% emissions?

But if you supercharge something, you are simply increasing the amount of air/fuel being burned. So, (using simple numbers) if you are burning 2x as much air/fuel in four cylinders than in normally aspirated eight, aren't the percentages of emissions the same still?
Or does an efficiency factor come into play here. Such as burning more air/fuel in less cylinders is still more efficient than burning the same amount across more cylinders?

[Evolution1980]

Originally Posted by Rob

the ZR-1 met its demise is because the LT5 engine would not pass upcoming stricter emissions regulations without a significant re-engineering t

Yes, but they would have been re-engineering a technology (DOHC) that they weren't very familiar with in the first place. I'm pretty sure that GM has a firm grasp on how the dinosaur pushrod engine works, as evidenced by the LS7 itself.

[Edmond]

Could it be because the SC kicks in at higher speeds and RPM? When they take you for emissions testing here, the max speed you're at is about 60 MPH to simulate expressway driving. I don't know who drives 60 on the e-way.

Maybe at lower speeds you use less SC?

[Rob]

Originally Posted by Evolution1980

Yes, but they would have been re-engineering a technology (DOHC) that they weren't very familiar with in the first place. I'm pretty sure that GM has a firm grasp on how the dinosaur pushrod engine works, as evidenced by the LS7 itself.

I don't agree with that at all. The development of the LT5 engine was a joint venture between GM Powertrain and Lotus in Hethel, England.

Lotus was not the sole developer of the LT5. GM Powertrain engineers spent just as much time in Hethel, as Lotus Engineers spent in Detroit.

The LT5/ZR-1 program began to come to fruition around the middle to late 1985. The original design intent was not to go with a DOHC architecture. However due to space restrictions under the hood and between the frame rails of the C4, the DOHC architecture was agreed upon between GM Powertrain and Lotus.

The actual manufacturing of the LT5 was contracted out to Mercury Marine, because Mercury Marine had the experience of manufacturing engines in low volumes, which GM, did not.

Take a wild guess where the Cadillac's Northstar engine came from.....that's right, the LT5.

So I don't agree that DOHC technology was something GM Powertrain was not experienced with.

[Evolution1980]

Originally Posted by Rob

I don't agree with that at all.
Take a wild guess where the Cadillac's Northstar engine came from.....that's right, the LT5.

So I don't agree that DOHC technology was something GM Powertrain was not experienced with.

Good point, I forgot about the Northstar. Now that you mention it, I recall asking/suggesting that the C6 be based around the Northstar engine. (This was before anything else had been specified about the C6.)

One of the points I was trying to make in my original post here is that GM has decades more knowledge with the pushrod engine than a DOHC engine, so their grasp on the pushrod should be much greater and deeper.

[Hib Halverson]

Originally Posted by Rob

Mmmm....but one of the reasons why the ZR-1 met its demise is because the LT5 engine would not pass upcoming stricter emissions regulations without a significant re-engineering that would have cost more money than GM wanted to spend - especially in light of the 300 hp LT1 engine debuting in '92.

That's pure bull based on General Motors spin.

In fact, the 475hp, 1995-96 LT5 which would have to have been compliant with the second generation on-board diagnostics (OBDII) requirement for MY96 was already under development with several prototypes of the engine in testing when the LT5 program was killed in 1991.

There was no problem with the engine meeting emissions for 96.

The problem was the cost of upgrading the LT5's engine computer to give it the extra diagnostic abilities required by OBD II. GM decided not to spend the estimated $1,000,000s to do that but really--had politics inside General Motors Powertrain Division not already damped any further enthusiasm for the LT5, they'd have probably spent the money.

More GM spin is the problem of the 92 LT1 being too close in performance. Yeah, the gap would have closed for 1992. But in 93 it widened and, had the 3rd gen LT5 appeared in MY95, it would have further widened.

[Rob]

Originally Posted by Hib Halverson

That's pure bull based on General Motors spin.

In fact, the 475hp, 1995-96 LT5 which would have to have been compliant with the second generation on-board diagnostics (OBDII) requirement for MY96 was already under development with several prototypes of the engine in testing when the LT5 program was killed in 1991.

There was no problem with the engine meeting emissions for 96.

The problem was the cost of upgrading the LT5's engine computer to give it the extra diagnostic abilities required by OBD II. GM decided not to spend the estimated $1,000,000s to do that but really--had politics inside General Motors Powertrain Division not already damped any further enthusiasm for the LT5, they'd have probably spent the money.

More GM spin is the problem of the 92 LT1 being too close in performance. Yeah, the gap would have closed for 1992. But in 93 it widened and, had the 3rd gen LT5 appeared in MY95, it would have further widened.

Interesting. I didn't know any of that. I stand corrected.

[*89x2*]

Originally Posted by Rob

.

As a result, GM had to find an alternative for the Z06 - hence, an engine smaller than 427ci, and supercharged.

What do you think? Fact or fiction?

Callaway Cars' SC560 package w/ their LS2 based Corvettes is 50 state legal - with over 560 hp now, and more in the (near) future, there may be some benefits to forced induction on a smaller displacement engine


The 427 badge has / had a nice ring to it - but other (better) technology is out there

[Aurora40]

I may be wrong, but I don't believe the requirement to meet 50-state emissions legality on an existing car is nearly as strict as the federal and state requirements to sell a car as "new".

As Hib mentioned, OBD-II was more about more sensors and computing than really about tightening any emissions. It was about the car being able to monitor emissions degredation on it's own. The big hurdle for most engines was probably time and cost.

Just since it was mentioned, the Northstar didn't appear until 1992 on a '93 MY Cadillac Allante. The LT5 development would have occurred way before this. However, GM engineers would have had experience with the Oldsmobile Quad-4 which debuted in the 1987 MY. Though I believe the powertrain groups were separate for CPC and BOC (Buick, Olds, Cadillac).

I wouldn't say supercharging is "better" technology. It's different technology. I'm sure a blower on a smaller displacement (but same physical size) motor would result in a heavier car with lower fuel economy numbers. It might be the way the 'vette goes, though. Ford went that way with the Cobra, and I thought the result was absurd. A 400hp Mustang that weighed as much as my Aurora does. The SC and related iron block requirement resulted in a Mustang that weighed almost 2 tons. The GT500 has the same problem. Whether it's the way to go on the 'vette, I guess we'll have to see. No doubt 650hp makes a good argument, though.

[*89x2*]

Bob, you are correct, aftermarket and small volume manufacturers do not have to meet quite as stringent run-arounds to get a car certified for the road.

Point is though, it did go through a process and IS certified.

Diesel requierments are getting tougher this year and I am sure the "greenies" would love to see all internal combustion engines pollute less - nevermind the fact they have never been cleaner...

In essance, the cost to get the car to the emissions standards )whether through cleaner tailpipe numbers or through an OBD II arrangment) did kill off the LT5. The cost to do this killed the LT5 - isn't OBD II about emissions

[Edmond]

How many years of lead time were manufacturers given to comply with OBDII standards? From my recollection, Toyota started doing hybrid type things of OBDII systems in their 1994 vehicles, two years before it was mandated for 1996 vehicles.

[Aurora40]

Originally Posted by *89x2*

In essance, the cost to get the car to the emissions standards )whether through cleaner tailpipe numbers or through an OBD II arrangment) did kill off the LT5. The cost to do this killed the LT5 - isn't OBD II about emissions

OBD-II was about emissions monitoring, not really emissions. It was about monitoring the emissions equipment to ensure it operates properly over time. This is why now you can have your OBD-II car emissions inspected by them just hooking up to the computer and ensuring all the monitoring tests have passed and no codes are present instead of them sniffing the tailpipe.

I'm not an expert, but I don't believe there were any tailpipe emission tightenings with the OBD-II requirement for 1996 MY cars.