QwkTrip

iTrader: (23)

Can somebody please share screen shots of tables in the factory engine ECM that are used during engine warm up (after cold start)? I'm wondering what are the differences of cold start strategy for a factory ECM vs. Holley HP EFI.

I have Holley HP EFI and am having problems with cold start warm up and fuel compensation being appropriate at different ambient temps. For example, the engine needs a LOT more fuel at 70°F coolant temp on a cold day than it does on a warm day. And the difference is far more than can be accounted for with air temp compensation.

I've concluded that oil viscosity is causing the large differences of fuel use. See Section 4.1, https://www.sciencedirect.com/scienc...96890414001939

Factory engine ECM doesn't seem to struggle with such things. Hoping maybe I can replicate some of the tricks used by factory in my HP EFI software.

Project GatTagO

iTrader: (7)

Air temp compensation is not active during cranking. The combination of cranking fuel and IAC Park is what determines your AFR during cranking events. I have also found that increasing the fuel prime value tends to result in faster starts.

Andrew

QwkTrip

iTrader: (23)

I'm interested in the engine warm up cycle. Not having any difficulty with initial start.

Project GatTagO

iTrader: (7)

I warm up the engine in closed loop and use the coolant temperature AFR offset table. This modifies the target AFR table and I generally shoot for about 12.9-13.0 AFR during warm-up (generally no colder than 40 degrees around here). For colder weather I would shoot for around 12.5 AFR and lean it out gradually as you come up to operating temperature.

Andrew

LLLosingit

iTrader: (4)

Not sure how you can say this, You can add a ton of fuel through either air temp and coolant temp compensation or both, Enough that it will kill plugs pretty quickly. I'm not a tuner but have been able to dial in several engines running the Holley systems. I've never had any issues with warm after setting up the initial start up in the software.
Some of the things I could see would cause issues, Vacuum leak/ Idle versus temp compensation set to low/ Target AFR to low at idle, Most seem to like 14.0 more often than 14.7 at idle warm./ Acceleration enrichment to low/ Timing off (Not what the engine like at idle.) LQ4 likes 25* while my supercharged LY6 likes 15*

Can you explain what your setup is and what exactly it's doing?

QwkTrip

iTrader: (23)

Air temp, coolant temp, & oil temp (viscosity really) are all contributors to fuel demand. What I'm learning is that oil temp (viscosity) is a pretty large contributor -- way too large to be ignored. And oil temp rises VERY slow compared to coolant temp, so the engine goes through the whole "cold start warm up cycle" before the oil even comes up to temp.

So what that means is the frictional losses (and fuel consumption) will be different depending what is the oil temp at start up. For example, I can dial in coolant temp enrichment at 70°F from a 20°F start, but that will end up being pig rich when engine is started on a warmer 60°F day because oil is at a much lower viscosity. It's so pig rich that I had to abandon the coolant compensation maps that I developed last winter.

So.... the question is, how do the OEM's deal with this? I want to try to replicate their strategy with custom tables in the Holley HP EFI.

Does MAP and oil viscosity have a tight relationship? Is that how they do it? Currently my coolant compensation tables are the same for all MAP values. I never paid close attention to MAP during startup and maybe that's where I went wrong.

QwkTrip

iTrader: (23)

I just realized I can download and use HP Tuner software without owning a device. Found a stock tune and looking at it.

LLLosingit

iTrader: (4)

You are way overthinking it, Oil viscosity has never been an issue on any engine I've run and if you're going to use that excuse then you might want to throw in thermal expansion throwing off your tune. If it's going pig rich your setup/tune is off somewhere and it's not an oil temp issue.

Project GatTagO

iTrader: (7)

Agreed. ten bucks says his Air temp table modifier table is off...or it's just set to 100% across the temperature range.

Andrew

QwkTrip

iTrader: (23)

I take PayPal.

https://forums.holley.com/showthread...le-Fine-Tuning

QwkTrip

iTrader: (23)

After a little more thought and discussion with a friend, I think MAP vs. Coolant temp is the answer because MAP is the only means a speed density system has to sense load on engine. Higher viscosity oil (colder oil temp) will put more load on the engine.

That's probably why Holley put a MAP axis in the coolant temp enrichment tables. I think from now on what I need to do is pay closer attention to MAP during engine start up. So basically I just went round circle back to the beginning. But at least I have a better understanding how things work and what I need to focus on.

QwkTrip

iTrader: (23)

Pig rich was an over exaggeration on my part. But it's definitely overly rich during the warm-up cycle now that weather is warmer. Scan the white paper I linked, you'll find parts of it interesting.

LLLosingit

iTrader: (4)

This is why I asked what setup you're running and exactly what it's doing> Do you run cats on the engine? One thing I run into quite often is people aren't used to the smell of an engine that's not running catalytic converters and they think there is something wrong because of the smell when it's quite normal.
Are you running a non stock camshaft? This can also cause an engine to smell somewhat rich at idle.
Timing can also alter emissions at idle and light throttle.
This is one of the reasons I like running E85 or Methanol, It still has a strong smell but the smell isn't as obnoxious as gasoline.

Project GatTagO

iTrader: (7)

Why aren't you running in closed loop during the warm up cycle?!?!? There is a very convenient AFR vs. coolant offset table specifically for this.

Andrew

ddnspider

iTrader: (26)

What is "overly rich on cold start"? The factory put the car in the 11's at cold start.

Project GatTagO

iTrader: (7)

Yup. In my AFR offset table I have values as high as -3.5. This means that the ECU will target my base AFR table (set to 14.7 at idle) minus 3.5, which puts me at 11.2. This is at temperature around 20 or lower F.

Andrew

smokeshow

iTrader: (17)

Ignoring some of the smaller details, there are two main contributing factors to determining how your equivalence ratio needs to be set during engine warm up. There is some overlap in their authority and capability but they can be mostly addressed individually to ease your calibration process. One is how much fuel can vaporize before it enters the cylinder and the other is how much of the fuel present in the cylinder can actually contribute to burning and generating torque. I'll summarize each one as it pertains to a stock LS1.

1) GM has historically used an intake valve temperature model for PI engines (and DI too, actually) to estimate how much extra fuel needs to be injected due to what isn't vaporizing. As you well know...only the fuel vapor is combustible. When I was at Chrysler we used a pretty clever model that estimated the actual mass ratio of the fuel that is vaporized and available for combustion called Burnable Vapor in Suspension (BVS). I still like to think of it using this model - the BVS ratio is used to calculate how much extra fuel must be injected to make up for the discrepancy caused by some fraction of the fuel not vaporizing during cold/cool engine temps. GM doesn't make this term explicitly calibratable, so you have to rely on the IVT gain tables to make up the fuel difference. For example, if the IVT, IAT, injector tip temp, air flow rate, compression, fuel RVP (more below), etc all come together and make it so that only 2/3 of the fuel injected is actually vaporizing, the IVT gain at that point must be 1.5. So with that initial 2/3 multiplied by 1.5, you're back up to 100% of the actual burnable fuel that is needed.

2) The other big player is figuring how much of the fuel that does vaporize actually burns and isn't lost to things like cold ring seal and other cold engine heat-sapping dynamics. Cold rings are an obvious one...some of that vapor will just push past the compression rings and be lost to the crankcase, so that must be accounted for. However the biggest component here is the fact that fire doesn't like cold. It is harder to initiate combustion in the cold, and since a cold engine saps away combustion heat to the heads, cylinder walls and piston, less heat is available to sustain the combustion as well. So more fuel must be injected to make sustaining combustion possible in an environment not well suited to burning stuff. The key takeaway: decreased temperatures reduce flammability. With a lower flammability limit, you have to provide more fuel. That's what open loop EQ ratio tables do - they provide more fuel to move the fuel concentration above the lower flammability limit based on ECT and IAT. For example, if the engine and conditions produce an environment where the lower flammability limit of your fuel is 20% but the amount of fuel you're injecting only nets a 10% concentration, you'd need to double that open loop EQ ratio to get to at least the minimum amount of fuel required for combustion. And then you'd need to find the optimum EQ ratio within those flammability limits to keep combustion variability minimized.

Another variable outside the control of the software and calibrations is the Reid Vapor Pressure of your particular fuel which is determined by the alcohol content of the fuel and when (on the calendar) you fill your tank up. You'll be familiar with the summer/winter fuel blends...this fuel change can have dramatic impacts on startability and warmup combustion stability if not also accounted for. There are various ways to handle this, but for another time.


That's probably way too much information but it should cover all the fundamentals for cold start and warmup fueling for a production ECM. Holley will do some things differently, but the physics remains the same. Just find the **** available to turn with the Holley software that accomplishes something analogous so those topics above and it should run while cold, no problem.

QwkTrip

iTrader: (23)

No, not too much info. Fantastic explanation. Thank you!!! You didn't have to spend your time doing that and I very appreciate you did. Not to mention you're the first person that listened...

LLLosingit

iTrader: (4)

I listened and asked you twice exactly what issue you were having and you just ignored it, It's hard to help someone when they don't care to share info on the problem they are having.