Motorcycle ITB idle issue/ help setting switchpoint curv

[jdmckechnie]

Ive got a 1978 Suzuki GS1000 running MS2extra 3.4.1 and ive recently switched from straight speed density to ITB mode. Ive had success running the bike VERY briefly on a dyno above 1500 RPM trying to collect information to set the switch point curve.. but i cannot for the life of me get the thing to idle.. The bike typically idles around 55-60kpa in SD mode, and ive tried to increase resolution in the SD portion of the VE table to allow a bit more control over the idle and off idle operation- no luck. please help!

my datalog was 10 MB, i cant figure out how to attach it- here is alink to the datalog in my drop box https://www.dropbox.com/s/e8ivz4qqjkq50 ... 3.msl?dl=0

[jdmckechnie]

Am i missing any information for people to help me out with this? please let me know if the dropbox link is working or not !

[grom_e30]

what elevation do you live at? it appears when you engine is not running you are seeing about 89kpa. itb needs 90kpa to switch from sd to tps so i'm not sure this will work to well for you.

[elutionsdesign]

There is quite a bit of lost sync in that, reason 0.

[2swe]

what elevation do you live at? it appears when you engine is not running you are seeing about 89kpa. itb needs 90kpa to switch from sd to tps so i'm not sure this will work to well for you.

afaik, itb mode switches to SD when MAP is higher than 90% baro (90% of initial MAP reading) and TPS above ITB switch point, so when you start the engine at 89kPa it will be switching at 80,1kPa until the next start..

[2swe]

Am i missing any information for people to help me out with this? please let me know if the dropbox link is working or not !

link is working, but the datalog is useless, there is no data needed to set the ITB TPS switchpoint curve..
you were running this same engine in SD mode before '? do you have some datalogs ?

[jdmckechnie]

what elevation do you live at? it appears when you engine is not running you are seeing about 89kpa. itb needs 90kpa to switch from sd to tps so i'm not sure this will work to well for you.

I lived in calgary, and will be running this bike on the bonniville salt flats this year ( hopefully ). so altitude will be my enemy, and if theres any way to make this work id like to know how. I was under the impression that the switch point was 90%of the measured baro at the time of start up. I read it some where on another post from someone a few years back.

Am i missing any information for people to help me out with this? please let me know if the dropbox link is working or not !

link is working, but the datalog is useless, there is no data needed to set the ITB TPS switchpoint curve..
you were running this same engine in SD mode before '? do you have some datalogs ?

Yep ive got the same engine running in SD before, but i experienced alot of weird issues trying to tune it. some of which might be due to lack of experience, as im only a casual MS user with a few bikes worth of experience under my belt. Here is a link to the other tune in SD, which was taken out on the back roads near Okotoks alberta ( also high elevation ). https://www.dropbox.com/s/l9fmvf3dxqsyn ... 0.msl?dl=0

There is quite a bit of lost sync in that, reason 0.

How do i fix this lost sync? would that cause spikes in my tach input ( up to say 20,000rpm??) im running fuel only off one of the coil -ve's.


Thank you every one for your help!

[2swe]

open your datalogs in MLV, go to scatter plots, selec rpm - X, tps - Y and map - Z

then apply data filter with this formula : [Field.MAP]/[Barometer]<0.89 || [Field.MAP]/[Barometer]>0.91

now you are looking at your ITB load TPS switchpoint curve.

[jdmckechnie]

2swe: thank you for that! i wish there was a super detailed and spelt out explanation for all of this. i know there is some writing about ITB mode in the manual, but it doesnt tell you how to filter your log to see the switch point or even HOW to create filters for MLV. Ive figured a few of them out, like viewing datapoints above a certain MAP, or engine rpm, but thats just from copying the format of the other filters already on MLV. Id never have figured it out on my own. I know what data i was looking for ( tps @90% baro) but being able to come up with those filters is beyond me! thanks a bunch.

as for my idle issue.. anyone have any ideas whats been happening? If i have the engine programmed to SD it idles perfectly fine. as soon as its in ITB mode it stops idling and just wants to s*** the bed below 1400ish rpm. occasionally i could get it to hang out around 1100-1000 rpm, but the afr had to stay super rich and any attempt to lean it out would bring the rpm back up and it would just fall on its face if i lowered the idle speed. The thing is, i think its in my set up ( programming issue ) because having adjusted nothing, going back to SD fixes all idle issues. ive tried even giving the VE table 100% SD authority at idle and up to 3000 rpm or so by allocating the bins on the VE table to SD near idle kpa, and tapering it down towards 3000rpm.

[2swe]

are your throttle bodies properly balanced ?

I would recomend some VE table changes :
you don't need 85,95,98% load rows, 80,90,100 is enough.
but you need more resolution in your idle area, and in area where load is going from SD to AN and back. I have 3% between rows here.
your engine idles at 32-33%load, but you need some rows below idle for light throttle cruising, I'm sure the load will go as low as 15-20%

I don't think you need 300rpm resolution between VE table columns - 7900,8200,8500
but you need 1 or 2 columns below your idle rpm, I'd add 700 rpm column, and maybe increase cranking rpm to 700, so when idle falls down , aditional fuel will kick it back..

[jdmckechnie]

are your throttle bodies properly balanced ?

I would recomend some VE table changes :
you don't need 85,95,98% load rows, 80,90,100 is enough.
but you need more resolution in your idle area, and in area where load is going from SD to AN and back. I have 3% between rows here.
your engine idles at 32-33%load, but you need some rows below idle for light throttle cruising, I'm sure the load will go as low as 15-20%

I don't think you need 300rpm resolution between VE table columns - 7900,8200,8500
but you need 1 or 2 columns below your idle rpm, I'd add 700 rpm column, and maybe increase cranking rpm to 700, so when idle falls down , aditional fuel will kick it back..

Yea my VE table has some interesting numbers on it yet, im sure i could refine the load and rpm cells a bit. but my question for you is this: if it idled perfectly fine in SD , is changing the resolution near idle going to help? my understanding was that if i have my 'load at switch point' curve set so idle and off-idle loading is speed density still, it should idle somewhat similar to my old SD tune?
The reason ive got 7900,8200,8500 all bunched up is because thats where the bike is going to be making max power and its where it will spend most of its time racing. i figured a bit of extra resolution there would be a good thing?
I will try increasing cranking rpm! hopefully it doesnt come to that. As well, i will add some bins below my idle rpm and see if that helps.

[2swe]

Yea my VE table has some interesting numbers on it yet, im sure i could refine the load and rpm cells a bit. but my question for you is this: if it idled perfectly fine in SD , is changing the resolution near idle going to help? my understanding was that if i have my 'load at switch point' curve set so idle and off-idle loading is speed density still, it should idle somewhat similar to my old SD tune?

when you look at your older SD datalogs, was the idle rpm, map, pw and afr similar to what you see now ?
I think changing the VE table resolution around idle must help, just look at your datalog, engine is trying to idle outside the VE table..

The reason ive got 7900,8200,8500 all bunched up is because thats where the bike is going to be making max power and its where it will spend most of its time racing. i figured a bit of extra resolution there would be a good thing?

in high rpm/ high load area the engine breathing tendst to be very linear, so it's unlikely you will need more resolution here, but if you will, you can use table switching..

[whittlebeast]

See http://www.msextra.com/forums/viewtopic ... 34&t=63074

It is simply behaving like a typical ITB motor.

I use blended Speed Density and Alpha N on my motor but my tuning method is not really for a beginner. we can go that direction if you want.

Andy

[jdmckechnie]

im not much of an advanced tuner yet. ive read a few of your other posts on the ITB topic wittlebeast, and i think your method of tuning is a bit too complex for the limited time i have with this motorcycle to run/tune it before we race. any other suggestions on how to correct the idle?