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Emissions legal tunes

18K views 109 replies 20 participants last post by  DieselDrax 
#1 ·
For the emissions compliant tunes such as from GDE, that bump the power up by a significant margin plus reduce the EGR usage; if such an improvement was possible, why didn't Chevy/GM do this from the factory? There must be a logical reason and corresponding trade-off. Was Chevy just being sure they pass emissions by a fat margin? Or maybe the power was turned down so the user could pretty well run it at 100% without worry of breaking any hard parts? Does the new tune increase EGT possibly shortening the life of the emissions parts (DPF, SCR)?

Everything in life has trade-offs, I'm just trying to understand this one to help me make a decision on buying the tune when my warranty is up. Truth be told, I would personally prefer a reduced-EGR tune that kept the stock power numbers, though I do understand that might not sell as well to the general public as a power boosting tune.
 
#3 ·
I tow a lot, both stop and go and highway. The transmission takes a beating in stop and go towing as it is, so I'm curious if the extra power would cause the torque converter or transmission to wear out significantly faster than with a stock tune when doing a lot of towing. And does EGT with the new tune run significantly hotter than the stock tune when towing on the highway?
 
#4 ·
Not sure about the newer trucks, but the transmission settings in the older ones were way too "soft" with lots of slipping going on. Tuning the trans to shift more firmly has to help it live longer. The factory engine tuning leaving quite a bit to be desired would not surprise me though, as the OEM transmission settings on my '17 were such a complete mess.
 
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#7 ·
A sniffer test is a complete joke. To be emission street legal you need to pass the following EPA mandated emission tests, same as original manufacturer: FTP75, HWFEC, US06 and SC03 To date Green Diesel Engineering is the only after-market tune that has accomplished this.

Snipesy, There are no legalities pertaining to EGR directly, you just need to meet tailpipe requirements in the said four tests above.

FYI, we have the emission results posted on our website for all to see, including the EPA. The trade-offs are clear in those results. We thought it was a good idea to lower CO2, since this is a virtually a 1:1 inverse relation to fuel economy.
 
#8 ·
I'm surprised people think that GM is the end all be all when it comes to any aspect of their vehicles. Sure they are good, heck even down right decent at most things, but not the best. This is why the aftermarket exists...
 
#9 ·
car manufacturers have to compromise. they have to make a decent product within a budget so the vehicle is competitively priced, and it also has to be reliable and not only last through the warranty period, but the target is to last much longer. its a very complex balancing act. it also has to pass NVH standards along with emissions and safety.

the aftermarket exists because a small portion of vehicle buyers want to make things better. often you sacrifice something when modding a vehicle, be it noise emission, longevity, etc.
 
#11 ·
the way my truck was stock, it would’ve killed the trans way before 100k. I had shudder and black fluid. At 35k..
GDE tune and hp lv fluid made shifts way better than it ever did by a large margin. After 40,000 miles on the fluid, it is still perfectly clear and red. Will have to see what the long term affect will be using this setup but I can say for sure, it will last much longer than how my truck was delivered.
 
#15 ·
Actually, compliant DOES mean legal in this regard. The EPA even has a "National Compliance Initiative" to crack down on non-compliant products and companies. Any aftermarket company that produces software or hardware products for use on emissions-compliant vehicles has to be able to prove such products don't violate the Clean Air Act and vehicles with these modifications don't exceed EPA emissions limits. That is what GDE has done.

The reason the GDE tune isn't available in California is because CARB has different requirements and any non-factory hardware or software has to be given an E.O. number by CARB in order to pass emissions because of the non-factory calibration ID that would be reported.
 
#16 ·
That sounds convincing enough to me. I read through their site this evening, and saw the CARB exclusion.

I'd still like to know what the compromise is. GM gives us a compromise of a tune to maximize certain parameters. They have a different tune for the military application that maximizes different parameters. What is GDE's tune maximizing, and what are they sacrificing relative to stock? This is more or less the exact same question as the OP phrased slightly differently.
 
#17 ·
IIRC, the military trucks have no emissions equipment or requirements.

The 6L50 for the diesel trucks has a maximum input torque rating of 550Nm which is around 406lb-ft (going by memory). The GDE tune brings the crankshaft torque up to around 420lb-ft peak, again going by memory based on their dyno numbers and doing some math. So there's that, but that also doesn't mean imminent failure.

Based on my experience with my truck towing when stock and monitoring everything I'd have no problem running it at WOT as long as necessary without exceeding any temp limits or triggering any derating. Could that be done with the GDE tune? I have no idea.

Pushing the envelope does make the weaker links easier to find, factory tunes I'm sure are trying to meet fuel efficiency, reliability, and performance targets as best as possible. When it comes to the aftermarket, choose 2. The 3rd is likely to take a hit to a certain degree.

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#18 ·
Based on my experience with my truck towing when stock and monitoring everything I'd have no problem running it at WOT as long as necessary without exceeding any temp limits or triggering any derating. Could that be done with the GDE tune? I have no idea.
this is exactly the info i want to know. other diesels im used to the tuners have multiple levels, either on a switch or a handheld loader with multiple tunes for different applications. GDE doesnt do this. im quite interested to know if their tune is safe for max towing.
 
#25 ·
Higher cylinder pressures does not mean hotter exhaust as fuel has a cooling effect. There is actually a drop in NOx production at full load vs. part load around 70%. We do not change the overheat protection from GM factory settings. Lambda limit is a 15x16 map based on rpm/air mass. GM varies the limit from 0.8 to 1.44. GDE keeps the map much flatter with a range of 0.8 to 1.125. The full emission data is at the link below, so you can see the emission trade-offs we made, the 2019-2021 lists the results for tuned and stock. 2016-2018 is only tuned data.

 
#26 ·
I was referring to combustion temperatures, not EGT. More energy produced necessarily means more heat unless your thermal efficiency is over unity (which is impossible for anyone not hip to the lingo). NOx comes from temperatures getting hot enough during combustion to cause the nitrogen in the charge to combine with excess oxygen. If you're running LOP, you have more oxygen available without any fuel, but then you're also generally running cooler in much the same way as you do when there's soot cooling the combustion chamber in an over rich scenario. I can see where this would be an "on average" scenario based on your 10K' description of the fuel map. If that's the case, that's the case, just trying to figure that sort of thing out.

I don't know what "overheat protection" is exactly. Google returned information about space heaters and electric motors. I was specifically referring to the safety margin in the cooling system. GM will have engineered the system with some % overage to account for losses in efficiency over time, overloading, wear, and various other reasons. If you're making more power, you're necessarily making more heat. That heat has to go somewhere, and that somewhere is the cooling system (unless the cooling system is overloaded, in which case it goes into breaking things). If you're making more energy than stock, you're making more heat than stock, and you're reducing the safety margin in the cooling system by some amount, even if only in very specific circumstances. This isn't necessarily a bad thing as long as there is a reasonable safety margin left, but it's something worth knowing. If someone properly maintains their machine, they should retain a substantial percentage of that margin, even with a fair amount of wear, and it shouldn't be an issue. The question I and others want to know, is how tight is that margin? To answer the OP's question for you, this is necessarily one of the tradeoffs, I just want to hear you say it, and detail the specifics of that compromise, as well as any other similar compromises.

That pdf has been on my desktop for at least a few weeks now. The results look really good, but they don't answer the question of how you got there, and that's really what we're after. There was a similar conversation here or somewhere else a while back with another tuner, and what ended up coming out of it is that particular tuner didn't know his ass from an onion. I wouldn't let one of his tunes near my machine for anything. GDE is the only tuner for these engines I've seen that I've had reason to suspect might know what they're doing, and thereby might not grenade my engine. I'm looking for confirmation of this, as are others. Between voiding warranties without a replacement warranty and the high incidence of tuned engines blowing holes in pistons, we're looking for some reason to think GDE's tune is worth not only the investment, but the risk. In this case, that means customer education.
 
#27 ·
The overheat protection is for preventing thermal issues for coolant, oil and exhaust temps. In normal operating conditions you are never near the limits of 242 F coolant, 270 F oil and exhaust about 1500 F. If you are pulling 7000 lb up Eisenhower pass in CO with 70 F outside temps. With the stock engine tune or GDE tune, the temps will climb as you try maintaining 65mph. Once the temps near the specified limits, the protection kicks in and starts pulling out fueling. This effectively slows the vehicle down to where the heat transfer reaches equilibrium. Basically, in extreme conditions the controls will limit output based on cooling system effectiveness.

There are several instances of holes in pistons on 2016-2018 Colorado diesels, stock and tuned. We have not heard of the same issue on 2019+ as GM changed injectors that year. I are not privy to the internal injector design changes GM made there.

NOX is formed with combustion temps above 2200 F. We work on the flame front propagation to limit time above these temps to minimize NOx formation. In terms of how we got there, it included a lot of trade-off testing running 16-mode steady-state for engine mapping and transient cycles. We also setup DOE (design of experiments) to effectively measure other trade-offs for pilot injection timing, # of events, fuel quantity, boost, fresh mass air vs. make-up from egr, fuel pressure and post injection. With so many variables it would take hundreds of test hours to make single trade-offs, with DOE multiple changes can be applied and evaluated quicker, then look into contribution %. We use Kistler Kibox for all the cylinder pressure and burn rate development. This tool is the gold standard for engine development and will set apart a diesel calibration engineer from aftermarket 'tuner' companies.
 
#28 ·
Jackpot!

The overheat protection is for preventing thermal issues for coolant, oil and exhaust temps. In normal operating conditions you are never near the limits of 242 F coolant, 270 F oil and exhaust about 1500 F. If you are pulling 7000 lb up Eisenhower pass in CO with 70 F outside temps. With the stock engine tune or GDE tune, the temps will climb as you try maintaining 65mph. Once the temps near the specified limits, the protection kicks in and starts pulling out fueling. This effectively slows the vehicle down to where the heat transfer reaches equilibrium. Basically, in extreme conditions the controls will limit output based on cooling system effectiveness.
Ah! So that is the term for the software based safety net. Makes sense. Cue Bob Dylan. If that's untouched, that's a pretty solid safety net to compensate for the otherwise mandatory compromise. As someone who lives near the Eisenhower Tunnel, I can appreciate the example. Those grades, speeds, durations, and altitudes take out unladen stock vehicles every single day. Brutal.

There are several instances of holes in pistons on 2016-2018 Colorado diesels, stock and tuned. We have not heard of the same issue on 2019+ as GM changed injectors that year. I are not privy to the internal injector design changes GM made there.
It's difficult to track too closely on forums. Limited sample size, limited information. It's early days for the 2019+, and they may still prove problematic. I hope you're right. It may be worth doing some sort of analysis to round up all the instances of this occurring, and seeing what can be gathered. With all the hard data in one place vs. the anecdotal scattershot it currently is, it would be interesting to see if any trends appear.

NOX is formed with combustion temps above 2200 F. We work on the flame front propagation to limit time above these temps to minimize NOx formation. In terms of how we got there, it included a lot of trade-off testing running 16-mode steady-state for engine mapping and transient cycles. We also setup DOE (design of experiments) to effectively measure other trade-offs for pilot injection timing, # of events, fuel quantity, boost, fresh mass air vs. make-up from egr, fuel pressure and post injection. With so many variables it would take hundreds of test hours to make single trade-offs, with DOE multiple changes can be applied and evaluated quicker, then look into contribution %. We use Kistler Kibox for all the cylinder pressure and burn rate development. This tool is the gold standard for engine development and will set apart a diesel calibration engineer from aftermarket 'tuner' companies.
That's the sort of information I am personally interested in. Repeating/rephrasing to verify understanding: Contrary to more traditional diesel engines, modern diesels allow for multiple and variable injection events per cycle. By introducing small brief injections early in the cycle, it's possible to create a "soft start" of sorts (this is one way diesel engines have become more "civilized" and less rattle clatter). By manipulating timing, number, and duration of injection events throughout the cycle, you're able to more precisely add power compared to the coal rolling idiots' fuel dump strategy. GDE, unlike most diesel "tuners", has gone a step further and paid attention to figures beyond just POWAH!!! and made an actual comprehensive tune. GDE has invested in actual tools (beyond a rented dyno, false confidence, and grunting) to ensure what they've done actually works, is legal, and hopefully doesn't cause problems. All of this check out?

Back to the OP's question: The ultimate answer would be a replacement warranty wherein any damage that can be demonstrated to be caused by the tune, and is denied by GM, would be covered by said replacement warranty. This is the pinnacle of standing behind your product, but may not be feasible for a small company with a small market (due to the cost of such a policy, regardless the presence or absence of claims). You described a failsafe for the cooling system from the OEM that, to my mind, more or less eliminates one of the presumed mandatory compromises of this sort of manipulation. There's far more to an engine than a cooling system though. What other tradeoffs are made, and what safeguards are there preventing problems associated with those calculated tradeoffs? Just to clarify, these tradeoffs are not in anyway a negative judgement, simply a statement of fact. An engine tune is a zero sum game where the total is the capabilities and limits of the platform, and if you want gains in one area, you must necessarily sacrifice in others. Expanding one capability requires a reduction in another to avoid exceeding the overall limit.
 
#31 ·
Firstly @GreenDiesel thank you very much for the open dialog. To give you one potential customer data point: I'm an engineer who enjoys motors, I understand all of the details you are giving. But to boil down my question; by going with this tune, am I increasing the risk (relative the OEM tune) for any big ticket repairs in the long term, considering I tow a lot? If the answer is yes, then I just want to understand the risks so I can evaluate. It's a lot more power so more risk is not unexpected, I just want to understand what becomes the new weak points with the increased power.

For more details; My primary goal for a tune would be to reduce EGR in an attempt to prolong the inevitable having to clean out the intake side of the motor. My personal main concerns for a tune: (1) early transmission failure from the additional torque, (2) early turbo failure from overspeed (you already addressed this) or higher EGT or (3) early emissions parts failure due to higher temps. You've already addressed peak cylinder pressures and injection timing relative crank position as how it relates to hammering on the bearings. I'm 100% fine with, and appreciate, keeping the OEM fail safes. I've already seen transmission temps over 220F (that only stopped climbing because I stopped driving), so maybe your additional torque converter lock up would actually help in that regard, and I'm guessing would help with torque converter longevity too?
 
#32 ·
MattFL,

1. The stock trans does not seem to have many field failures internally. There are many failures of the stock torque converter in stock and tuned 2.8l vehicles. The OEM converter has a turbine damper with a weak design. Our trans tune helps a little bit in this regard by engaging full TC lock-up. This reduces tranny fluid temps and commands zero slip when in lock-up mode. GM prefers to have a 20-30 rpm slip target, this creates more heat and more clutch disk wear. It does reduce driveline vibration. With the GDE tune the vehicle has a more connected feel to the road.
2. We limit the turbo speeds with respect to Garrett's limits based on frame size and bearing material. The EGTs are self regulating with the overheat protection.
3. The exhaust temps while driving with the GDE tune is very similar to stock. We expect the DPF to last longer with our tune due to the reduced soot (PM) formation in-cylinder. We are burning a bit less fuel with the optimized burn rates. NOx engine out is slightly higher based on load, but the DEF system takes care of that so tailpipe is still well within TierIII, LEV125 SFTP limits.

When towing within the rated limits of the vehicle, we see no risks with our tune. You need to use common sense with an extra 40 hp on tap, no need to hammer down for extended periods of time. That extra power is best for short bursts like passing or on ramps, etc. Most OEMs have different ratings for short term high load tests (20-30 minutes) vs. long term lower load running. If you hammer down on long grades with a big load, it will not take long to reach the EGT limits (within a minute or two) and fuel is pulled out to control temps. You lose some of the available power as well of course.

Tuning is not for everyone. The advantages are measured in miles per gallon and smiles per gallon.
 
#34 ·
1. The stock trans does not seem to have many field failures internally. There are many failures of the stock torque converter in stock and tuned 2.8l vehicles. The OEM converter has a turbine damper with a weak design. Our trans tune helps a little bit in this regard by engaging full TC lock-up. This reduces tranny fluid temps and commands zero slip when in lock-up mode. GM prefers to have a 20-30 rpm slip target, this creates more heat and more clutch disk wear. It does reduce driveline vibration. With the GDE tune the vehicle has a more connected feel to the road.
So some "comfort" and/or "refinement" in exchange for longevity and engagement. That seems like the sort of exchange an OEM would make that a savvy user would prefer the opposite. This is the good kind of tradeoff!

2. We limit the turbo speeds with respect to Garrett's limits based on frame size and bearing material. The EGTs are self regulating with the overheat protection.
How and why does this compare to OEM turbine speed limits? I assume OEM limits exist as well.

3. The exhaust temps while driving with the GDE tune is very similar to stock. We expect the DPF to last longer with our tune due to the reduced soot (PM) formation in-cylinder. We are burning a bit less fuel with the optimized burn rates. NOx engine out is slightly higher based on load, but the DEF system takes care of that so tailpipe is still well within TierIII, LEV125 SFTP limits.
That reduced soot is due to a leaner mixture (makes sense with the fuel savings). A longer lasting DPF sounds great. What was the OEM going for that resulted in their different fueling strategy? What is the tradeoff here? The higher NOx is what I was talking about above, and sounds like the load scenarios where fueling is greater. I'm getting the vibe that there's a steeper slope to that curve such that it's more on/off than gradual, and thus a bit more engaging/fun. If you're burning less fuel and keeping it clean while ALSO making more power, that sounds like it would mean a more pronounced transition. Kinda like tuning the idle jets in a carburetor LOP, the mains ROP, and having a really sharp transition between the two to avoid "the danger zone". It works out that daily driving is pretty chill (and fuel efficient), but then when you need the power and the throttle gets more than halfway down, it just comes on.

When towing within the rated limits of the vehicle, we see no risks with our tune. You need to use common sense with an extra 40 hp on tap, no need to hammer down for extended periods of time. That extra power is best for short bursts like passing or on ramps, etc. Most OEMs have different ratings for short term high load tests (20-30 minutes) vs. long term lower load running. If you hammer down on long grades with a big load, it will not take long to reach the EGT limits (within a minute or two) and fuel is pulled out to control temps. You lose some of the available power as well of course.
What does "common sense" mean in this specific context? How do you define "hammer down" (pedal on the floor? 80-100%? >50%) and "extended period(s) of time"? As someone who lives in the mountains, on a max legal grade road, and needs the truck to do truck things on occasion, would you suggest sticking with the safer factory settings? Is this a flat lander thing? What happens if I need to tow something heavy, and long steep grades are all there is?
 
#33 ·
@GreenDiesel Great info, thank you very much! Final question; relative the OEM tune, do you run higher fuel rail pressures for the same power output?

Allowing the TC to slip slightly to soak up vibrations is an interesting decision on GM's part, perhaps that explains why the OEM tune doesn't lock it up as much (comfort over function). I wonder if that decision led to a lot of the TC shudder issues. Is it plausible that some imperfection led to more slipping than intended, overheating and polishing the clutch surfaces, leading to the shudder when it is intended to slip slightly?

Time to count the days remaining on my warranty. :)
 
#38 ·
Allowing the TC to slip slightly to soak up vibrations is an interesting decision on GM's part, perhaps that explains why the OEM tune doesn't lock it up as much (comfort over function). I wonder if that decision led to a lot of the TC shudder issues. Is it plausible that some imperfection led to more slipping than intended, overheating and polishing the clutch surfaces, leading to the shudder when it is intended to slip slightly?
this is nothing new, gm started this back in the 90s on the 4l60e. when gm added pwm (pulse width modulated) lockup they changed to a carbon fiber clutch material to deal with the heat produced by essentially slipping the lockup clutch. the whole idea is to take the harshness out of the vehicle when the converter is locking and keep things smoother. its common practice during an overhaul on these transmissions to block the pwm lockup valve in the valve body, this eliminates the slipping lockup clutch and lockup is either on or off. this helps with converter clutch longevity and reduces transmission temps.

the converter shudder is essentially caused by the converter clutch grabbing and letting go, real quick. its not really a case of they are slipping too much, more the opposite, they are grabbing more than they should. essentially the engineering team got it wrong, and gm's fix was changing the fluid specs (going to either a more slick fluid, allowing more slip, or a fluid that essentially allows the clutch to bite more), although this is sort of a band aid solution. the aftermarket solution is tuning the pcm to apply the lockup clutch quicker, and run higher pressure to keep the lockup clutch locked at 0 slip, however there can be downsides to this. with no converter slip you will feel more of the engine, especially at low rpm. the other downside here is running higher converter pressure essentially tries to push the converter forward, this puts more stress on the crank thrust bearings. at the modest changes in pressure in tunes, i doubt this would ever present itself in our trucks, but it is something to be aware of.
 
#35 · (Edited)
@spectre6000 leaner mixture is a gas engine thing, there's no such thing with a diesel as they are a lean burn engine. You can't lean out a diesel more for a cleaner burn. Properly running, it's always lean.

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#37 ·
@spectre6000 leaner mixture is a gas engine thing, there's no such thing with a diesel as they are a lean burn engine. You can't lean out a diesel more for a cleaner burn. Properly running, it's always lean.
Lambda... GM varies the limit from 0.8 to 1.44. GDE keeps the map much flatter with a range of 0.8 to 1.125.
While I'll grant you that being afraid of a lean mixture is a gasser thing, it looks like GDE and GM would disagree.
 
#42 ·
Ah! I get you.

"If you try and make it run leaner than it normally would then you just lose power... you are not going to get a diesel to run even leaner while maintaining power/RPM" Completely agree. Making less power is absolutely an option though, and it's one GDE/GM select under certain circumstances. With that lower power comes cooler temps (which corresponds with lower NOx) and a cleaner/less sooty burn; both of these statements are qualified with "below a certain lambda". This must be kept in check in order to meet the emissions testing criteria, which is GDE's party trick, and the reason I'm personally taking them seriously. The opposite is also true, and goes back to the power gains with diminishing returns I mentioned above.

Based on the information available:

  • Both GDE and GM have a min lambda of 0.8
  • GM's max lambda is 1.44 to GDE's 1.125
  • GDE makes more peak power
  • GDE gets better fuel efficiency

Fueling maps are RPM on one axis, and load on the other. For the available information to all check out, in certain circumstances GDE is necessarily running more fuel for a given RPM/load condition (this is a certainty any time GM's tune has a lambda > 1.125). For GDE to get better fuel economy though, there must also be RPM/load intersects where GDE runs higher lambda than GM. For GDE to also make more power, they must be running more fuel than GM at whatever that rpm/load condition is. Based on this, it necessarily follows that a given RPM/load intersect can have more or less fuel, generate more or less power, and generate more or less emissions (soot and/or NOx). The hangup is that there's more to it all than just fuel, and we have no information about those parameters... or nearly no information. I think GDE said they run the EGR less, there's some massaging of the injection frequency and timing, and I'm sure there's some turbo speed control going on (though I don't think it's been mentioned aside from preventing too much speed) to control the air.

I guess bringing it back around, one of the tradeoffs between the OEM tune and GDE is that GDE's is more peaky and abrupt compared to the smoother, wider range of the OEM tune. This is in part, I'm sure, due to the creature comfort/refinement angle GM was going for. Personally, I have no trouble with that. Prefer it even. It's fun; character. It's how I usually tune my DD cars.
 
#43 ·
Ah! I get you.

"If you try and make it run leaner than it normally would then you just lose power... you are not going to get a diesel to run even leaner while maintaining power/RPM" Completely agree. Making less power is absolutely an option though, and it's one GDE/GM select under certain circumstances. With that lower power comes cooler temps (which corresponds with lower NOx) and a cleaner/less sooty burn; both of these statements are qualified with "below a certain lambda". This must be kept in check in order to meet the emissions testing criteria, which is GDE's party trick, and the reason I'm personally taking them seriously. The opposite is also true, and goes back to the power gains with diminishing returns I mentioned above.

Based on the information available:

  • Both GDE and GM have a min lambda of 0.8
  • GM's max lambda is 1.44 to GDE's 1.125
  • GDE makes more peak power
  • GDE gets better fuel efficiency

Fueling maps are RPM on one axis, and load on the other. For the available information to all check out, in certain circumstances GDE is necessarily running more fuel for a given RPM/load condition (this is a certainty any time GM's tune has a lambda > 1.125). For GDE to get better fuel economy though, there must also be RPM/load intersects where GDE runs higher lambda than GM. For GDE to also make more power, they must be running more fuel than GM at whatever that rpm/load condition is. Based on this, it necessarily follows that a given RPM/load intersect can have more or less fuel, generate more or less power, and generate more or less emissions (soot and/or NOx). The hangup is that there's more to it all than just fuel, and we have no information about those parameters... or nearly no information. I think GDE said they run the EGR less, there's some massaging of the injection frequency and timing, and I'm sure there's some turbo speed control going on (though I don't think it's been mentioned aside from preventing too much speed) to control the air.

I guess bringing it back around, one of the tradeoffs between the OEM tune and GDE is that GDE's is more peaky and abrupt compared to the smoother, wider range of the OEM tune. This is in part, I'm sure, due to the creature comfort/refinement angle GM was going for. Personally,
All this talk about fueling and power and no talk about timing and the different injections?
 
#44 ·
I ran through most of a full tank since tuning and the DIC was off by about 1.7mpg. Reported 22.8 on the trip meter, hand calculated it was 21.12. We'll see how subsequent tanks do, but so far I can't complain. Looking forward to seeing how it does towing the boat and on a long road trip.

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#47 ·
Yes it can. We measured a 10 bar drop in cylinder pressure by going main only at WOT conditions. The calibration of injection events are where it is at. We have past experience working with GM on some export projects. It seems they put some younger, inexperienced engineers on this platform and thus the refinement is not the best. The GM calibration changed completely in 2019 and looks like the folks in Torino, IT did the cal work on the newer models. This job was even worse and some of the OEM mapping looks like it was completed on an engine dyno and not even in a vehicle. The consumer market might be giving too many kudos to GM engineering.
 
#49 ·
Injector part number for 2016-2019 - 55594509
Injector part number for a 2019+ - 55504598

Yes, I didn't mess that up. The 2019 model year shows that both part numbers fit, so perhaps it was a mid-year change? The new injectors do look a bit different and like they wouldn't be a drop-in replacement without at least changing the high-pressure lines from the rail to the injectors. Would be curious to know what else changed or why the change was done.
 
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#50 · (Edited)
As you mentioned, the fitting for the feed line is different, the electrical connection appears to be the same. Wondering too if, assuming one can update the feed line, if the new injectors can run off the old ECM, and if they can, if it would be a good "bulletproofing" move to update to the new injectors. I doubt the Denso ECM would play (at least not without changing it's settings) with a different brand of injectors even if the physical electrical connection is the same. Perhaps someone who actually knows this stuff can weigh in.

On to what I can control and do, also wondering if diligently using a good lube/cleaning additive and adding a 2 micron Racor marine filter after the OEM box (the add on filter continues to work perfectly by the way, no affect on the filter life screen, nothing visible in it to date) will help to protect me from the dreaded stuck injector and holed piston nightmare. Those steps can't hurt I suppose.

Old injector:

407330



New injector:

407331
 
#52 · (Edited)
My truck has emissions testing coming up soon and I still had GM's recall cards on my desk, so I finally relented and took my truck in for the recall work. Not sure about my state, but my research suggested that some states will deny registration renewal (CA for sure) if the DMV sees emissions related recall work not completed. To be honest, I also wanted to be on record as completing the recall and purchasing the EPA compliant tune.

After driving home from the dealer with the GM settings, I simply could not bear to drive the truck with the stock settings. I had forgotten just how soggy, numb and awful the stock settings are. The engine didn't even sound as good as it did before, the cool little intake hum at cruise was gone. Clearly my 2.8 was not nearly as happy as it was before I brought it in to the GM dealer.

Purchased and installed GDE's EPA compliant tune ($50 for prior customers, I elected to get the regen notification screen for another $25) and to be honest, I can tell no difference between it and their prior "Pre EPA" tune that I had before. All the same solid, immediate and linear response to any touch of the pedal is back, the quantity of power is back, even the intake hum. I would never be able to definitively tell the difference between pre EPA and EPA compliant settings. If anything, the latest settings seem a bit smoother at low RPM pulling a light load in a tall gear, but that is seriously nit picking. Any differences there may be on the dyno are not readily apparent in actual use.

Transmission settings were much the same, I was running the "09AC" file before, the latest approved settings are slightly more refined, but nothing drastic, a tiny bit smoother but in no way "mushy". I can't imagine a 6L50 trans working any better than this, as GDE can't do anything about turning our 6 speeds into an 8 or 10 speed.

So I have used GDE's pre EPA settings for 40,000 miles, the latest GM settings for 15 miles, and now GDE's compliant settings, so I can say from immediate experience what the differences are. At this point I dunno why GM does not pay GDE a bunch of money and simply use their EPA approved settings, as they are night and day better than the settings GM sends these engines out into the world with.

In their prior post GDE said "most likely, the bench calibration met emissions in the vehicle and not much more effort was resourced for drive ability characteristics". That is a nice way of saying that the stock settings are raw and unfinished, and no refinement or "fun" of any kind was baked into them.

For those who feel they "missed out" on the pre EPA settings, take heart, you really are not missing out. As far as the driving experience goes, all the goodness of the pre EPA settings is still there. I am shocked - really did not expect the compliant settings to be this good and yet they are just as refined and just as much of a kick in the pants too. Kudos GDE, well done :cool:
 
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