Table resolution and size

Testing and development of Megasquirt 3

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Peter Florance
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Re: Table resolution and size

Post by Peter Florance »

Also most engines have a range of AFR where they are insensitive to changes.
Peter Florance
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AbeFM
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Re: Table resolution and size

Post by AbeFM »

I'm not sure if I should put this in feature requests or in here - but while I agree wholeheartedly with the idea of keeping the VE and ignition tables at the already large sizes they are.... The VVT table is limiting. I was recently taking some data DIY had shared from a well tuned VVT car and found that there were many significant peaks and valleys in their map, and had to do a lot of soul searching to figure out just how I would capture all the peaks in the limited space provided. At least at lower pressures, the table is a function of MAP as well as RPM, and a 2D table with lots of resolution really is needed. It might not need to be 16x16, but the 8 entry table was very tight.

I would recommend adding a few rows (12 by 12 should have breathing room, though one could argue that having it match the VE table would be nice?) would be a big help. With 10x10 I would feel I was getting enough to do the job, but just barely.
-Abe.
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Re: Table resolution and size

Post by muythaibxr »

for VVT weay be able to take that into consideration. I am not sure off the top of my head if there is any free space in the associated firmware pages, but I can look.


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Re: Table resolution and size

Post by AbeFM »

Awesome. It does seem like one of the few places where it would translate to increased performance. Perhaps gathering more data would help but it looked useful to me.

FYI:
Image

You can see there's many non-linear regions in there. The differences aren't huge, but they are there.
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Peter Florance
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Re: Table resolution and size

Post by Peter Florance »

AbeFM wrote:Awesome. It does seem like one of the few places where it would translate to increased performance. Perhaps gathering more data would help but it looked useful to me.

FYI:
Image

You can see there's many non-linear regions in there. The differences aren't huge, but they are there.
Do you have a legend of what load each trace represents?
Peter Florance
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AbeFM
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Re: Table resolution and size

Post by AbeFM »

Sorry, not handy. From memory, though, it's 20, 30, 40, 60, 80, 82 and 85 or something very close to that. Lowest lines are lowest values. Table seemed flat above 85 kpa
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Peter Florance
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Re: Table resolution and size

Post by Peter Florance »

AbeFM wrote:Sorry, not handy. From memory, though, it's 20, 30, 40, 60, 80, 82 and 85 or something very close to that. Lowest lines are lowest values. Table seemed flat above 85 kpa
Thanks!
Peter Florance
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AbeFM
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Re: Table resolution and size

Post by AbeFM »

I hope this doesn't step on any toes, but
Image

If this is getting too public, let me know, I'll pull it down.
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Re: Table resolution and size

Post by coyoteboy »

I always find this discussion interesting because while in practice ive not struggled to work with 12x12, I know oems are upward of 50x50 these days and I've seen the horrendous nonlinearity they endeavour to tune for.
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Re: Table resolution and size

Post by muythaibxr »

coyoteboy wrote:I always find this discussion interesting because while in practice ive not struggled to work with 12x12, I know oems are upward of 50x50 these days and I've seen the horrendous nonlinearity they endeavour to tune for.
Somehow I missed this comment at some point....

But where do you get your data from? The OEM setups I've seen are only marginally larger than what we have in areas where they still use tables. I read about the Mitsubishi Lancer Evolution where they only had something like 16x22 or similar for the tables I looked at.

Ken
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Re: Table resolution and size

Post by coyoteboy »

A couple of modern European Ford items under development (nothing high end) and recently seen an F1 fuel table that's upward of 80cells across base with several layers of adjustment maps of the same sizes.

As I say, from my own tuning I don't see much need (I think time is better spent on things like AE tuning) but I do see the OEM guys with plenty of dyno time seem to make use of it.
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Re: Table resolution and size

Post by muythaibxr »

I was under the impression that F1 and OEMs these days are going to model-based algos... I don't have a good idea of what tables that involves but clearly it's different from what we're doing, so I'm not sure if that is a good comparison point.

Ken
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Re: Table resolution and size

Post by coyoteboy »

The f1 one certainly isn't model based. The oem one was partially but only in certain operating regimes (idle etc).
tpsretard2
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Re: Table resolution and size

Post by tpsretard2 »

i would love to see a few extra rpm based rows, or an easier way to tune when you have table switching turned on.

2 of my engines are impossible to tune for performance and drive-ability with just 16, however 32 is not needed ether, there are a lot of zero's in the second table, i think i am using 21. But then there are about 10 other engines that i have a ms on, and 16x16 is enough. It totally depends on what the engine and car is being used for.

I think that if a tuning wizard could be made to use the table swith, but put it all in one window that it would satisfy people that need the extra table space. right now tuning the 2 tables separate is nothing more than a giant pain in my ass.
Toma
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Re: Table resolution and size

Post by Toma »

In systems that allow it, I run the minimum resolution. For instance, Haltech, my default table is set up to have rpm breakpoints at 500, 1000, 1500, 2000, 2500, 3000, 4000, 5000, 6000, 7000, 8000

Then, my load breakpoints are 25, 50, 75, 100 kpa, then 133, 166, 200....

Then, I tune the car. IF during the turning, there is a sudden VE shift, I add rows or colums as I need them.

This way, with a true VE system, I can breeze through the part throttle (upto 100kpa steady state on the dyno), in about 15 minutes. That tells me where the VE needs to be at WOT and boost, I "guess that" and fill that in, and start making wot sweeps.

So I waste tops an hour, and by that time, I know if the tune will go well. Then I go back, and re-do the part throttle, making sure IAT and coolant corrections are close, and again add load points if my actual does not match my target at any "in between" load point.

This is why I like the Haltech so much. You can start with a 8x8 table, then add rows and columns anywhere without messing up your tuned areas. Believe it or not, many systems don't let you eliminate "redundant" load points.

I was at Sema a while back, checking out some new systems, and I was annoyed how many go with crazy 20x20 or 24x resolution, and you cannot cut that down. Your only option is to assign usable points and only use the lower parts of the table, but then if you need a point here or there, you cant just add it, you are in the ugly position of copy and pasting values into new columns, to free up a lower one....

Anyway.... my experiences. 12 x 12 is usually lots. more are typically needed for rpm, versus map.
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Re: Table resolution and size

Post by AbeFM »

That last bit should be pretty reasonable, can't you grab entire rows in TS and just cut/paste a section of table to move it over?
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Re: Table resolution and size

Post by nathaninwa »

Yea, you can copy and paste. Im doing table switching at 3000 rpm and effectivly have a 26x31 table. lots of my bins are in the vacuum region, and with a tuned afr table, veal made tuning the first table easy. The second table is mostly boost, I put a boost bin every 20kpa, and was able to rpm every 200 right around peek tq for good fueling. It didnt take that much longer to setup and tune, and drivability went way up in the cruise section.
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