gemellocattivo.com

Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
It is currently Mon Nov 19, 2018 5:52 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 17 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Tue Mar 22, 2016 10:22 pm 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 122
mk e wrote:
One thing with enginelab is you can make changes to the control model on the fly......[alt s] to stop the ECU,
[Ctrl Space] to open the model logic, make your change and [alt R] to start it running. Very fast. The down side is that by far the easiest way to work with enginelab is using sub models and a build script which is instantly outdated when you work directly in the complete model....but if you jot down where you made changes you can export that part of the full model back to the sub-model. You can also do most of the debugging in the simulator so on engine debugging is mostly just confirming inputs are what was expected...like batter voltage showing 2.19 instead of 12.5.



Even if you can fix it quickly, that usually requires stopping the engine.

In general, the startup/idle/warmup calibration is some of the most difficult calibration work, but it has to be done first to be able to calibrate the rest of the engine, without a motoring dyno. In an ideal world, you can calibrate all of the nominal, loaded points (>idle at fully warm temperature) first, then the cold (and occasionally hot) adjustments. This way, your nominal surfaces aren't skewed by bad warmup enrichments, etc.

What sort of coolant system do they have? Engines on dynos tend to run at high loads for a long time. Also, do they have a fuel system with a good fuel flow meter? Fuel flow is invaluable to steady-state dyno calibration.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 8:38 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 2241
apalrd wrote:
Even if you can fix it quickly, that usually requires stopping the engine.

In general, the startup/idle/warmup calibration is some of the most difficult calibration work, but it has to be done first to be able to calibrate the rest of the engine, without a motoring dyno. In an ideal world, you can calibrate all of the nominal, loaded points (>idle at fully warm temperature) first, then the cold (and occasionally hot) adjustments. This way, your nominal surfaces aren't skewed by bad warmup enrichments, etc.

What sort of coolant system do they have? Engines on dynos tend to run at high loads for a long time. Also, do they have a fuel system with a good fuel flow meter? Fuel flow is invaluable to steady-state dyno calibration.


Yes, fixing anything in the model requires shutting down the engine

Yes, I ALWAYS tune the nominal steady state stuff first with warmup and other corrections disabled. I sometimes rough in a warm up to get it started and up to temp, but then disable it before doing any real tuning.

With the idle control turned OFF the throttle defaults to what's in the pedal > throttle table and I've set that up to act a lot lot a normal throttle stop so that simplifies what needs to be done to keep the engine running.

The dyno comes with a system capable of sustaining 700hp so they have at least that....and I won't be running this engine near that point for more than a seconds or 2 at a time....too scary :shock: But it will see 200-300 hundred hp for extended periods because that's the sweet spot for street use so I want it tuned well and they should be able to handle that no problem

They should have fuel flow and a fuel pump because it should come with the dyno package....but I need to confirm that. I'm not that concerned about this one though....I don't have any fuel mileage targets or goals to worry about so fuel flow is and BSFC are more interesting than needed. The ECU can log what it thinks is being delivered so better than nothing it it turns out nothing is available.

First things first though....it needs to actually run :)

....and last night I drained quite a lot of coolant from the headers :(


Attachments:
Throttle pedal.JPG
Throttle pedal.JPG [ 70.83 KiB | Viewed 4945 times ]
Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 9:41 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 122
mk e wrote:
The dyno comes with a system capable of sustaining 700hp so they have at least that....and I won't be running this engine near that point for more than a seconds or 2 at a time....too scary :shock: But it will see 200-300 hundred hp for extended periods because that's the sweet spot for street use so I want it tuned well and they should be able to handle that no problem


I agree, it's scary to run at high load for a long time, and I'm always hesitant at the beginning of my dyno sessions to do it. But, when doing steady-state mapping, it usually helps to stabilize at a point for at least 10 seconds. Normally when doing engine mapping, I do a 'grid' run, where I start at the lowest speed/load I can achieve and step through every cell in the table that the engine can reach, one at a time. This sequence tends to group a lot of high load points together, since they are all run in sequence. It's quite possible to spend a half hour or more running high load points. If the cooling systems can keep the temperatures stable and safe, it's not usually a problem for the engine.

mk e wrote:
They should have fuel flow and a fuel pump because it should come with the dyno package....but I need to confirm that. I'm not that concerned about this one though....I don't have any fuel mileage targets or goals to worry about so fuel flow is and BSFC are more interesting than needed. The ECU can log what it thinks is being delivered so better than nothing it it turns out nothing is available.


I use fuel flow for a lot of things other than fuel economy. I have a filtered BSFC on my dyno screen which I use for spark cal. I start at a very conservative advance and advance in steps until BSFC starts to flatten. I datalog and average 10sec of BSFC at a time at each spark step, when I'm done with a spark sweep the trend in the each log point will show where MBT is (unless I reach audible knock first, then I back off 2 degrees and stop there).

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 10:06 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 2241
apalrd wrote:
I use fuel flow for a lot of things other than fuel economy. I have a filtered BSFC on my dyno screen which I use for spark cal. I start at a very conservative advance and advance in steps until BSFC starts to flatten. I datalog and average 10sec of BSFC at a time at each spark step, when I'm done with a spark sweep the trend in the each log point will show where MBT is (unless I reach audible knock first, then I back off 2 degrees and stop there).


Why don't you look at torque directly for MBT? It seems like you're inferring using BSFC vs directly measuring?

I've also seen min EGT used to set below WOT timing figuring the point is max efficiency which should be where the least heat is coming out the exhaust pipe. I haven't messed with this much over the years but was considering giving it a try this time vs just trusting the factory timing like I normally do because I don't care that much about power at low power as long as it's not knocking.....but that almost certainly is leaving fuel mileage on the table.


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 10:33 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 122
mk e wrote:
Why don't you look at torque directly for MBT? It seems like you're inferring using BSFC vs directly measuring?

I've also seen min EGT used to set below WOT timing figuring the point is max efficiency which should be where the least heat is coming out the exhaust pipe. I haven't messed with this much over the years but was considering giving it a try this time vs just trusting the factory timing like I normally do because I don't care that much about power at low power as long as it's not knocking.....but that almost certainly is leaving fuel mileage on the table.


Torque would show a similar trend to BSFC, but obviously inverted. I'm mostly concerned with efficiency, so looking at BSFC made sense to me.

In general I care about all points equally, most of the points can be run at MBT without knock (on my engine), and always running MBT spark greatly improves fuel economy.

EGT is really only good at indicating if things will melt, and it's also one of the cheapest ways to look at cyl-cyl variations, but I haven't found it useful for anything else.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 11:05 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 2241
apalrd wrote:

EGT is really only good at indicating if things will melt, and it's also one of the cheapest ways to look at cyl-cyl variations, but I haven't found it useful for anything else.


You should NEVER trust it for cyl-cyl variation. There are just too many factors that can cause differences to know what the numbers mean. If you're on a budget and want cyl-cyl info then plug reads are about the only option, low resolution but they can't be wrong. With a slight budget I think NBO2 sensors are going to work.....I just need to prove it. EGT is normally used to look at change with time.....but I'm pretty sure setting spark to min EGT at any given mixture should be peak efficiency but it seems the same should be true for MBT and I guess BSFC too.

I'll need to ponder the BSFC thought. Efficiency can be improved with EGR and/or lean mixture but both require both fuel and spark changes....if mixture is fixed it seems like you'll never find optimal but would have the min BSFC...or are you changing fuel and spark looking at BSFC and basically ignoring mixture?


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 11:35 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 122
mk e wrote:
You should NEVER trust it for cyl-cyl variation. There are just too many factors that can cause differences to know what the numbers mean. If you're on a budget and want cyl-cyl info then plug reads are about the only option, low resolution but they can't be wrong.


I usually use EGT to point at which cylinder is having issues. But, the absolute numbers aren't useful on their own.

mk e wrote:
With a slight budget I think NBO2 sensors are going to work.....I just need to prove it. EGT is normally used to look at change with time.....but I'm pretty sure setting spark to min EGT at any given mixture should be peak efficiency but it seems the same should be true for MBT and I guess BSFC too.

I'll need to ponder the BSFC thought. Efficiency can be improved with EGR and/or lean mixture but both require both fuel and spark changes....if mixture is fixed it seems like you'll never find optimal but would have the min BSFC...or are you changing fuel and spark looking at BSFC and basically ignoring mixture?


I usually do a three-step process:
-First, VE is calibrated at stoichiometric using only O2 feedback. This establishes that the f/a ratio commanded should equal the f/a ratio the engine operates at. Spark is safely retarded here, and so efficiency will be bad. The entire VE surface is mapped this way.
-Second, the lean limit (or EGR limit) is established, making a 'lean limit' surface of target F/A ratios. The right way to do this is to look at CoV IMEP, but without cylinder pressure sensors I use hydrocarbon emissions. Without an emissions bench, I would probably have to look for a steep increase in BSFC and then back off a bit. Torque numbers aren't very valid because spark is retarded and fixed and MBT varies with F/A ratio or EGR %, so neither is BSFC, but a steep BSFC trend will show the onset of misfire, and hydrocarbons/CO will show that sooner and are unrelated to actual torque produced.
-Third, the spark is calibrated at the lean or EGR limit. Now, the torque numbers can be trusted and the final BSFC should be good. When the spark mapping is done, the data collected can be compiled into a BSFC map of the engine, which is really useful for analysis later.


I've never calibrated EGR before, but we're designing an EGR system now so that should be fun. I suspect the three-step process will turn into a five-step process - Spark should be calibrated stoich before introducing EGR, and spark air temp corrections need to be done without EGR since EGR changes air temp.

I might take your suggestion of using narrowband sensors per cylinder. Are you controlling their heater temperature?

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 12:20 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 2241
apalrd wrote:
I usually use EGT to point at which cylinder is having issues.

I guess...but normal cyl-cyl variation can be pretty big...50C? so it's hard to know if there's a problem or not just looking at cyl-cyl EGT.

apalrd wrote:
I usually do a three-step process:......

Have you ever gone back and re-looked at the lean limit after you've set the timing? I'm told the leaner you go the more timing it needs to run properly so I'd expect the lean limit to be something you'd need to sneak up on by alternating leaning the fuel and advancing the timing . The same is true for peak hp, normally it's 4-5 steps with fuel/spark before max output is found


apalrd wrote:
I might take your suggestion of using narrowband sensors per cylinder. Are you controlling their heater temperature?


No control on the heater. It's normally just on and it self limits pretty well. I've pondered if monitoring the heater current could give a decent temp so the output and with temp the sensor could be calibrated to give a lambda say 1.0 +/- 0.1 instead of just 1.0 rich/lean...but that will be a project for another day...or year :)


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 12:56 pm 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 122
mk e wrote:
Have you ever gone back and re-looked at the lean limit after you've set the timing? I'm told the leaner you go the more timing it needs to run properly so I'd expect the lean limit to be something you'd need to sneak up on by alternating leaning the fuel and advancing the timing . The same is true for peak hp, normally it's 4-5 steps with fuel/spark before max output is found


No, I don't usually go back, although I do sometimes re-run a few points to verify them.

As you go leaner (or more EGR), you get two things:
-Burn rate becomes slower, this increases the MBT spark angle slightly requiring more advance
-Combustion becomes less stable, this can be overcome by over-advancing spark so more of the combustion cycles burn at/above MBT phasing and less misfire.

If I am only looking at HC emissions, I will see a power drop and efficiency drop as I go lean, but HC's will stay very low until I approach instability. When I calibrate spark properly, power is still lower than stoich (which is good at part throttle) and efficiency should be higher (lower BSFC). If I was looking at BSFC alone, I would probably alternate a few times.

mk e wrote:
No control on the heater. It's normally just on and it self limits pretty well. I've pondered if monitoring the heater current could give a decent temp so the output and with temp the sensor could be calibrated to give a lambda say 1.0 +/- 0.1 instead of just 1.0 rich/lean...but that will be a project for another day...or year :)


That's why I've asked, the curve of O2 voltage vs lambda changes with temperature but you can measure temperature of the heater and correct the curve, giving a bigger usable window. Production ECU's will instead PWM the heater to a target temperature (using the heater's resistance as a temperature sensor and measuring current to calculate resistance), and use the O2 voltage to lambda curve at that temperature.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Wed Mar 23, 2016 1:20 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 2241
apalrd wrote:

That's why I've asked, the curve of O2 voltage vs lambda changes with temperature but you can measure temperature of the heater and correct the curve, giving a bigger usable window. Production ECU's will instead PWM the heater to a target temperature (using the heater's resistance as a temperature sensor and measuring current to calculate resistance), and use the O2 voltage to lambda curve at that temperature.


Are you sure they do that with NB sensors? It sounds possible but I've not hear of anyone doing it on anything but WB sensors.

On my setup I have a WB sensor in the bank collector and plan to use that reading to "calibrate" the cylinder NB cylinder readings....haven't written that code yet though. For now I'll just check the cyl-cyl variation at 1.0 lambda and call it a day but I know the system can do more than that with a little work.


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 17 posts ]  Go to page 1, 2  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group