VE Table 4

[Maddog6961]

Would it be possible to add an additional VE table for table switching? I would love to be able to have an idle map, a cruise map, and a WOT map. I think that would help megasquirt get a lot closer to a lot of factory ECUs.

My ideal situation would be to have one map under 1000rpms from 100 kpa to 20 kpa, a second map switching above 1000 rpms for cruise from 1000 rpms to redline and 110 kpa to 20 kpa, and a third map switching based on kpa from 1000 rpms to redline and above 110 kpa.

Does anyone else here agree? Is this a possibility?

[hassmaschine]

you don't need multiple tables for that - idle and WOT only take up a small part of the table (lower left and the top row), leaving you ~224 VE bins for the rest of the map. basically, using a whole table for just idle, cruise and WOT is redundant and will just make it more difficult to tune (trust me, I've been down that road already).

I think the real purpose of table switching is for running different fuels and boost levels - IE you want to run ethanol and a shot of nitrous in addition to a regular gasoline N/A tune.

[Maddog6961]

Except that I can get more resolution using more tables, which I don't NEED but would like to have. Every other stand alone engine management system I have used has had at least a cruise map and WOT map. The more expensive ones will allow for an idle map also.

[Maddog6961]

Also, I could end up killing my first 5 or 6 rpm bins tuning for idle to get a perfect mixture at all times.

I want high resolution in the cruise area because thats where I spend most of my time driving and more control will allow me to run leaner more reliably.

I want the WOT map so that I can have precise control to combat problem fueling areas at high RPMs. I don't just want to throw more fuel at an area of the map thats causing the problems. I want to be able to adjust the fuel exactly.

[muythaibxr]

and using a 16x16 fuel table isn't enough to do this?

There's no more room for any more tables by the way, so the answer is no, we aren't going to put in a VE 4.

Also, I think having an Idle map, cruise map, and WOT map are WAY overkill when the same effect can be attained using smart placment of the load and rpm bins in the 16x16 table.

Just because the "other guys" do it doesn't mean it's the best way... or even that it's necessary.

Ken

[hassmaschine]

Also, I could end up killing my first 5 or 6 rpm bins tuning for idle to get a perfect mixture at all times.

I want high resolution in the cruise area because thats where I spend most of my time driving and more control will allow me to run leaner more reliably.

I want the WOT map so that I can have precise control to combat problem fueling areas at high RPMs. I don't just want to throw more fuel at an area of the map thats causing the problems. I want to be able to adjust the fuel exactly.

you already have a WOT map - you can set the top portion of your map to whatever VE you wish.

the advantage we have is the ability to set the scale of our tables any way we like - meaning, we can group our load and RPM bins where they can be the most effective, instead of requiring a ton more load sites to achieve the same resolution.

once you spend some time tuning you will realize there are large flat spots in the VE of your engine - where a large table would just be wasted space and additional tuning effort, and a flexible table (like what we have) can eliminate redundant/flat VE areas and use that resolution for important areas like WOT, cruise and idle.

here is my VE map for example:


see how I have groupings of load/RPM, and some areas where there are large flat spots? for example, the VE is flat between 2300-3100rpm, 4400-5200, and 5700-6700. I have more bins grouped near my idle (~900-1100rpm), and freeway curising (3100-3500rpm). I could improve this even more (I don't need the 300rpm and 43kpa areas) but you get the idea. originally, I had two tables for the same map - which was twice as much tuning effort for the exact same results.

[Maddog6961]

I would love to see some datalogs of close to perfect tunes along with an MSQ file. Seeing successful tunes would definitely curve my opinion on this issue.

[hassmaschine]

when I get my EAE dialed in (I just figured something major out the other day) I'll definitely do that - but without any accel enrich at all, my AFRs are pretty much exactly where I want them.

[mops]

hm....

ok, i didnt bother to read everything....

but really, 16x16 map is plenty, provided you can define your own bins (which you can)

it is hard if not impossible to tune the fuel map to 0.1afr accuracy. it will change with humidity and temperature, baro, etc. there are corrections but you will spend lifetime adjusting corrections to perfection, and that is not really necessary.

basically for cruise you want as lean as you can go without any hicckups/surges, etc. depending on engine (and timing) that might be in the range of 16-19. eg my 2 valve bmw m20 engine likes no leaner than 17.5 cruise, will sort of tolerate up to 18.0:1, but generally i try to avoid over 18:1. running on the edge of lean will require well tune AE, any even small throttle movements will force mixture temporarily lean, and for smoothness you do want to avoid lean misses. it is really challenging to get fast gear changes behaving smoothly in the 'lean cruise' territory (hey, it's called a map after all )

I had not much luck using automatic EGO correction. in always it seems to overshoot and therefore oscillate. i admit i havent tried advanced ego algorithms. i do not use ego correction at all.

likewise on WOT.
not sure whether you noticed... on lower gears wot is leaner than on higher gears. because engine is accelerating faster at lower gears. what i do there is put it on 4th gear (out of 5) and tune wot there to 12.5-12.8ish
that will ensure that on low gears 1st, 2nd, the mixture is slightly leaner producing slightly more power for short periods (which is ok), while once you are on 3rd, 4th it gets to very safe 12.5ish, and slightly rich at 5th (think long highway hill climb on top gear, wot, where rpm's do not change)

as well here air temp and baro corrections have some effect and it is hard to tune to the 0.1 accuracy. but again that's not needed.

besides, in wot region engines behave in a very stable manner, and WOT curve can be very well approximated with just few points... for every engine i think...

[edit]
and regarding idle...
again hard to tune to perfection. i normally just put idle on 1 plane, defined but 4 vertexes, and i generally set them all the same. that produces very stable PW for idle. same with timing. stable idle and timing produces stable idle. sometimes not at the rpm's that you want but that's what closed look idle control is for.

[hassmaschine]

mops, what settings were you using for EGO control?

I had mine working very well, but then I realized it was causing full lean spikes off-throttle - that I had been trying to tune out with EAE. I have it turned off for now - but I never had any problems with it oscillating. it always seemed to respond fast and fairly accurately.

[Maddog6961]

basically for cruise you want as lean as you can go without any hicckups/surges, etc. depending on engine (and timing) that might be in the range of 16-19. eg my 2 valve bmw m20 engine likes no leaner than 17.5 cruise, will sort of tolerate up to 18.0:1, but generally i try to avoid over 18:1.

Can you email me your timing map? I am curious about what kind of timing you are running to be able to have that lean of a mixture.

george.carstens@gmail.com

[mops]

basically for cruise you want as lean as you can go without any hicckups/surges, etc. depending on engine (and timing) that might be in the range of 16-19. eg my 2 valve bmw m20 engine likes no leaner than 17.5 cruise, will sort of tolerate up to 18.0:1, but generally i try to avoid over 18:1.

Can you email me your timing map? I am curious about what kind of timing you are running to be able to have that lean of a mixture.

george.carstens@gmail.com

do you really need my timing map ?
it's pretty simple - at idle it's 20 deg. wot is pretty much as much as i can get without detonation (backoff 2-3 deg away from first sign of detonation)
as for cruise... you are right. high timing is the key for lean cruise (and idle for that matter). more timing will allow leaner mixture to burn.

if memory serves me right on overrun i run 45 degrees. and in crusie areas as much as 42 degrees. but definitely aroundish 40 degrees total timing at high speed cruise.

i'm slowly research ion sensing. i'd like to build one of those one day (hopefully soon). ion sensing can tell you when peak cylinder pressure is, in terms of degrees of crank rotation. then you can set your whole timing so all the time you get peak pressure at 15-17 degrees ATDC in all conditions and that gives you most efficient engine. advancing any further is only risking detonation and not making much more power (we are talking less than 1%-2% here). not worth it IMHO, and stresses on internals are noticeably lower.

[Maddog6961]

I really just wanted to know what you were running under cruise....thats a lot of timing.

[mops]

I really just wanted to know what you were running under cruise....thats a lot of timing.

yes and no.
it depends on the engine.
i'm aware that some older v8's run as much as 50 degrees on cruise, and more.

Aswell older design 2 valve hears (like nissan z240 engine) runs in vicinity of 50 degrees on cruise.

aswell there's this old trick to run massive advance on overrun, to actually slow down the engine more effectively...

and it further depends on cam and other things.

so the rule applies, give the engine what it wants. under cruise it can actually make less power with more timing without detonation. i havent had that thing on dyno yet....

i'm by no means a tuning guru.