VEMS economy map

[Jamo]

Since I have dual map switching on my VEMS unit I was thinking of making a economy map with boost limited to wastegate boost ( 0.9 bar )

Has anybody done something similar and what AFR have you set as your target throughout the range?

Anyone got a screenshot of the lambda larget for example?

[A80Avant]

from my recent long drive to greece, i realised that vems was not as efficient in keeping good economy as motronic was,no matter how much i leaned out the afr, or tweaked the timing.i believe that it has to do withe the lack of airflow metering data that the ecu can use to continuesly adjust the afr to the desired levels.

what i also noticed was that in different heivhts from sea level,and iats, ego correction was reaching different levels of either adding or substracting fuel, without me touching the map.Hence if lamda pid control is mot adjusting as fast,or ve table is way off the desired lamda, it may be bad for consuption.

on my old setup i used up to 1.05 lamda.it also depends on your desired egt cruising levels and your knock threshold.

[GazzaG60]

gotta say i dont agree. my vems is good on the juice compared with motronic.

i dont limit boost. economy is not a boost thing its a crusie thing for me. boost is go-go and i want my cake and to eat it.

bigger injectors require more load sites below 100kpa. this is how best to get good economy. fine control is a must.

thinking of this how many boost setting you use can help with how many rows above 100kpa. we look for quick spool so not too many needed.

lambda targets vary very slightly between builds. set rules such a stoich and boost at say 11.5 are rules of thumb.

on idle i aim for a lean mix. you willk never do harm down there. think i see 1.1 or so there. maybe 1.12-1.15.

as i cruise i see 1-1.1. as she comes on boost well it dips to 0.7 and then up to say 0.82 or so. some fine tuning needed there.

best advice is feel for it. keep an eye on egt. bigger turbo and compression lower will mena you can add more timing.

feel for a change in smoothness. listen for a more lumpy running sound. as you load it up it needs more then less as you maintain speed.
clever use of acel enrichment here can help as that is effectively what we are after. a lean cruise and enough juice to pick up speed or hills.
too much timing brings no increase in power. it feeds back a kind of buzzing feel to me too much.

another option is narrowband input. wideband is great at the ranges at the wide ends so 8:1 to 12:1 or so and the high side too. it reacts slower to changes than narrow in the narroe zone. narrowband is very quick so can tell the ecu to change a lot faster.

as with any ecu dont use acel to compensate for the ve table.

your in now jamo. the never ending pursuit to tweak it a little more. i need to get that mojo back. had verms for what 3 years or so and my mapping time is still in hours and not days. car is currently no mot or tax or daylight to it.

[Rocco]

good explanation Vasilis , and Gary

for Vems users... and economic map for crusing would be good AFR 15,3?? and with a boost control with only 1bar ( for example) AFR values in WOT like 12´3 could be perfect??

you guys with Vems Ecus can mod anything :mischeif:

[Jamo]

I don't know if VEMS at the moment can do dual Wide and Narrow I'm sure I saw Rob comment on the VEMS forum it wasn't available or else I would have had an extra lambda probe point mounted.

If it can then it's a trip ti a local exhaust place

How many rows under 100 do you have at present? I have 5 at present.

I've changed injectors to a more VEMS friendly make and gone from 4 bar to 3.8 bar FPR to help with low end resolution.

My EGT's I could do with logging them on the motorway they were fine during mapping though.

I am using the enleanment setting which has helped on the old go juice http://www.vems.hu/wiki/index.php?pa...rey%2FFuelFilm

[A80Avant]

gary, i agree, but every time i tried going less than 1:08 the car didnt like it.it may be the small turbo and backpressure,as my egt went to 800 on cruising 6th gear and 80mph.

ill see how it goes with the next setup.

[GazzaG60]

like i say each engine is different and i think my larger turbo and tubular helps here with cruise. then the 7a cams. more na motor below 4k than anything else.

i have 2 probes. interesting is the differerences bettwen the values at the 2 points..

i run 12x12 so low number of columns. 6 below the 102kpa row. so majority down there. still not upgraded lol.

ROCCO. at lower rpm and crusing a 15:1 mix works for me. all the way to 80mph or so. above that it gets hot so i add a fraction of juice.

yoour correct standalone lets you do anything. that includes blowing it up.
i remember when i was messing with MSNS (megasquirt and spark) it was touted as a petrol strimmer to a 16000 rpm 8 pot IIRn't
everything that worked on a subaru too works here. even cars that wobble naturally can take lean mix and importantly timing. a properly tuned subaru doesn't chug. its pretty smooth. tubes are common on those due to engine design. they dont like running as lean though on boost. thats what happens when you make a block out of poor metal (aside from the ej22t the non intercooled legacy AKA 22b block) and run no shells. the crank sits on the machined block on those. sorry more non audi ramblings.

in summary i believe and trust in the principle rich ish on boost and leanburn cruise to clean it up.

[A80Avant]

gary, what is your max timing that you have used on 3000ish+rpm and from 70-90kpa ? and what lamda on those areas as well?

[pnanassy]

This is the BEAUTY of a standalone.AND also the hard part!

good explanation Vasilis , and Gary

for Vems users... and economic map for crusing would be good AFR 15,3?? and with a boost control with only 1bar ( for example) AFR values in WOT like 12´3 could be perfect??

you guys with Vems Ecus can mod anything :mischeif:

[GazzaG60]

not sure vas. not seen the car for 3 months. hope its still there, lol

i will do some logging and let you know. at a rough guess IIRC around 33 on timing, 600egt, mine is in the higher vac areas around 50-65 id say. 1.05 lambda. i run it to the edge of smooth here. motorway speeds are where the economy counts most.

bigger turbo and tubes i think help here and maybe the 7a.

peter i have an untested theory about req_fuel having an impact on this. whats your thoughts on that. i was thinking that higher may produce a better economy figure wth ve matched than a lower figure with ve matched

[Billman]

My experience is also that VEMS had better fuel economy than motronic. Not much but better (ca. 0,5 l / 100 km) on crouising at 130-160 km/h

[GazzaG60]

think it takes a very good motronic map to match it. most who do this dont fix what isn't broken so only change the uper limits where boost is changed.

to get a good map will take some time too so it will cost. then if you want a change it will cost again. at this stage cost-benifit analysis says vems.

[A80Avant]

thanks, that does asnwer part of my question.

it will be much different on the holset i believe.

[Jamo]

not sure vas. not seen the car for 3 months. hope its still there, lol

i will do some logging and let you know. at a rough guess IIRC around 33 on timing, 600egt, mine is in the higher vac areas around 50-65 id say. 1.05 lambda. i run it to the edge of smooth here. motorway speeds are where the economy counts most.

bigger turbo and tubes i think help here and maybe the 7a.

peter i have an untested theory about req_fuel having an impact on this. whats your thoughts on that. i was thinking that higher may produce a better economy figure wth ve matched than a lower figure with ve matched

Peter told me the opposite, the lower the req_fuel the larger the VE will be so you can get better multiplication resolution.

Mind you on the higher firmware as starting is done on req_fuel now you have to be careful with the req_fuel value or the car won't start

Anyhow getting my thread back on topic Gazza have you got a a screenshot of you lambda target you could send me?

I've had helpful advice offline from Repo about this so I will be tuning an economy map next just need to find a driver!