Exactly

 

Yeah it's not always about "good tune" vs "bad tune." Does the calibration meet the requirements of the application? When you take your car to a shop and they use HP Tuners or whatever, the requirement is to make as much power as possible without causing long term damage to the main parts of the engine. Everything (ok, almost everything) else is secondary.


California emissions consist of plugging into the OBD port and checking the diagnostic monitors, which GM engineered, and hooking up a basic ppm meter for HC, CO, and NOx concentration. You can't compare that to EPA and CARB test procedures that require millions of dollars in equipment and measure things like particulate number.


That's an oversimplification of the issue. If you're tuning the car for thousands of people in different climates and altitudes, there has to be a margin on the knock limited spark advance and the exhaust temperature limited/combustion stability for spark retard.

It depends on the priorities. High temperature feedgas degrades the catalyst, and so do exothermic reactions inside due to oxidation processes.

But you're right, CO emissions go up and so do CO2 emissions when you enrich. That's only measured on the US06 cycle for the US market though, and any vehicle with a good power to weight ratio will stay at the stoichiometric AFR on that cycle.

The combustion system design and hardware limits have a huge effect on the amount of enrichment required. What you'll see on the latest overhead cam engines are cast-in, water cooled exhaust manifolds to keep exhaust temps down. That limits enrichment requirements. You'll also see on direct injected engines an intake port designed for high tumble to increase knock resistance (the Gen V uses a high swirl concept). So if you take the new VW/Audi 1.8TFSI engine in Europe, with port + direct injection, that's a turbo direct injected engine that runs at Lambda=1 under the entire WOT range.

I haven't examined the oil separator closely on the Gen V, but the newest direct injected engines have pretty elaborate oil separator/breather setups. I agree that early ones, especially the notorious Audi DI engines, needed better separation performance. Typical new design is a module on the crankcase and a module on the valve cover. On naturally aspirated PFI engines like a stock LS1 (I have an LS6 on my CTS-V) it's just not that big of a deal in a fully stock configuration. The port injection washes the valve deposits off, and the knock control system is smart enough to handle and any abnormal combustion from buildup.

It depends on the metric. If the metric is to keep the cat from degrading (the main driver for enrichment), or to keep the combustion from being unstable and causing torque fluctuations (the main limitation on spark retard), or to have robustness for altitude, bad gas, etc (the main limitation on spark advance), well they have those limitations.

It's not flex fuel in part because the government cut the subsidies and fuel economy credits. Plus that would stretch out the development time, and everyone would be complaining that the Gen V took too long.

It's not that they couldn't figure it out, it's that they didn't care. Their job is to meet their targets. They didn't build the vehicle, then put it on a chassis dyno and fiddle with it to crank up the power. If they did, they could have found the same power everybody else is finding. During any development program like that almost everything performance-related is tuned on an engine dyno at the technical center, mostly in steady-state conditions. The main calibrations are frozen according to the development schedule.

Don't mistake a difference in mindset for a difference in ability.

 

GM has a twin turbo 500 hp motor soming. Why would they put the same grunt in the LT1?

 

As a engineer working on a performance team within a major US corporation I feel this sentence perfectly tells the story that most customers never really consider.

 

Quote:
I guess the geniuses with millions of dollars and all the PHd's couldn't figure out what the aftermarket hacks playing on dynos will in the next few months


With all due respect, don't underestimate the ability of all of the aftermarkets tuning capabilities as there are former GM, Chrysler and Ford engineers that now work at several of the well known Performance Shops.

It's my opinion that the car should be tuned individually based on
octane, climate, how the cars being used, the customers expectations as well as several other parameters.

Not at all trying to take away from the knowledge and skill of GM calibration engineers as I am sure they know their stuff.

Best Regards,
John Page
Twenty First Century Muscle Cars
www.21stcentruymusclecars.com

 

I always wondered how "bad" the emissions on a cat-less lean running performance engine would be.
If you run lean and hot, how bad can it be?
I honestly don´t know.

 

This ^

 

Of course. I agree. And what you achieve from doing an individualized tune doesn't somehow mean that GM's factory calibration robbed everyone of the horsepower they were supposed to have.

Different goals. Different mentalities.

 

Lean and hot, your HC emissions will be low even without a cat. The cat does most of its work during start/warm up and maybe WOT. But lean and hot will also send your NOX emissions through the roof. Emissions are very tricky since there is more than one thing you are trying to control and the adjustments you make usually have the opposite effect on the different emissions components.

 

The jagged dyno curve the stock engine displays above 5,500RPM suggests the stock ECM is managing power above that point. If one was to extraploate a strandard dyno curve for a LS-series engine above 5,500, you would see 450RWHP or 500 at the flywheel. Such a level would also be consistent with the typical gains of 15% seen when DI and VVT are applied to an engine. GM elected to keep this engine de-tuned for now, either for relability reasons or for marketing reasons (leaving room for future power upgrades). The LT1 is entirely capable of reaching 500HP in stock form, while meeting all durability, emissions, and fleet mileage requirements.

 

The car tuned by the OP could easily meet the same CARB requirements whether it has been tested for them already or not. Extra fuel getting dumped through the cats and getting ignited in them kills them many times faster than running at 12.0 versus 11.0 (which isn't remotely lean by any standard). The car in question was tuned in the Texas heat in hot temps so it only goes to reason that people in cooler (most other) climates could easily run the same tune - again demonstrating just how much power GM engineers left on the table.

Adding flex fuel to the C7 could have been done for an extra $50 cost to GM so please spare me the lame tax credits argument. On one hand you talk about clean emissions but then fail to acknowledge how much better E85 is in that regard - besides making a lot more power. As far as mindset if that is off target then you are screwed right out of the gate no matter what your ability is. I've been continually underwhelmed by GM's factory calibrations for 15 years now so from my standpoint the C7 ECU's shortcomings are just business as usual.

It's the reason that skilled aftermarket tuners can't keep up with everyone wanting their tunes fixed like they should have been from the factory to start with - and not at the expense of all of the things that you mentioned here

 

For the record my comment wasn't intended to be a dig at the after market community and their abilities; hell the main reason I decided to buy my Vette was because of the strong aftermarket support. My point is that "in general" customers are little too quick to voice how the designers/engineers should have made the car better by giving more of this or that... And for the highlighted comment above, I agree with you to a point, because if any OEM did exactly that they would go out of business because everyone would want something different. I feel the Corvette team did the best they could with the new PTM and driving modes, and for that I am thankful.

It has been a good thread so far, and as I'm deciding on which route I plan on going with my LS3 I look forward to what's in store when I finally get to upgrade to a C7.

 

 

I realize I'm not going to change any minds here, but maybe for entertainment's sake...

On a new car that's hard to say without running the test cycles. If it only affected WOT, then that's basically off-cycle. If the cat temperature increases, it's possible the car would fail the long term in-use testing mandated by the EPA. So you wouldn't know until 4 years from now. That's because every time you have an excursion into high catalyst brick temperatures, you degrade conversion efficiency and oxygen storage capacity. The catalyst diagnostic monitor (the thing that throws a catalyst efficiency code) can model the degradation to detect when the cat is way past dead, but you need lab-grade equipment to know whether it's working right or not.

You have to put a temperature sensor/thermocouple in the middle of the catalyst brick to really know what's going on. You also need the right gas analyzer/emissions bench. If the feed gas to the cat is rich with high CO and low O2, it will cool the cat. If the O2% is high, which is usually due to scavenging or incomplete combustion, then oxidation reactions occur. That will overheat the cat.

So what you're describing can happen, but you need oxygen to have the reaction you are describing. That's realistically not going to happen with the stock cam. You typically see that on DOHC turbo engines with VVT on intake and exhaust. On deceleration, the cat load up with oxygen. Then on tip-in, the cams will dial in overlap, the engine goes in-cylinder rich, and the turbo throws extra air out the exhaust valve. It can be a major consideration for transient scavenging calibration.

Manufacturers don't do a whole lot of tuning for power on the vehicle. By the time the engine goes into the mule vehicles, the tune was set on a dyno under controlled conditions. It has to meet the full load targets in a lab. The stuff in the vehicle is mostly torque model calibration, pedal mapping, etc.

Multiply $50 times the number of vehicles that will be produced and that's a lot of money. If the government isn't giving a benefit and most owners percentage-wise who actually buy the car new don't care about flex fuel, that's a lot of money for nothing.

It doesn't matter whether it's cleaner or not cleaner. Some emissions go up, some emissions go down; there's always a tradeoff. It's really a certification issue. There's no fuel economy credit and no financial incentive to certify a Corvette on E85. Plus it adds to development time. So the costs go up, most customers (middle aged guy who won't drive it much and won't mod it) won't take advantage of it, and the car is late to market.

Well, you can't please everybody, and you certainly can't have a factory tune built around satisfying some small percentage of owners. Unless there's some really blatant issue, usually the people who complain the most about the factory tune are the people who will never buy the car new--they want it to be perfect for modding right when it comes off warranty and has depreciated. And if there was very little power to be gained from aftermarket tuning, everyone would be complaining about that too--ask an Rx-8 owner. People will complain because they picked up so much power from aftermarket tuning (because the stock tune "held back"), and they will complain because they didn't pick up enough power from aftermarket tuning (because the stock tune was "maxed out").

You can go any way you want in the aftermarket. But if it were that easy to do so from the factory, the guys who made the engine would have done it.

 

I fail to see the problem.
The car is plenty fast as is for 99.9% of owners, the sub 1% that want more can do so in the aftermarket.
Everybody wins.

 

Its never fast enough!!

 

Of course not. That's why you and I members of the 0.1% club

 

 

As I said before if your focus is way off then the final product will also be way off. Shipping the car with a factory calibration that allows for the 1% of owners who will put 87 octane in the car and drive it hard severely compromises the car for the other 99% who aren't idiots. But that seems to be what happened here due to the power gains from a tuned bone stock car. Perhaps they de-tuned the C7 due to possible reliability concerns with the LT1 so who knows?

Either way 460hp was a joke right out of the gate

 

Not long ago there wasn´t even a 460 Hp Vette and a 8l v10 made 450 Hp...
So calling it a joke is a bit unwarranted I would think.