Few questions concerning MS3 Anti Lag (ALS) and Roving idle

[mrx79]

Hallo,
i plan to activate ALS and roving idle this winter in my project car and before i try to fidle out all the details i would ask some questions which come into my mind during reading the manual and looking and the calibration possibilities.

I put my questions in to parts to hopefully make it easier to answer them seperatly.

1a) in the MS3 precalibration roving idle fuel-cut percentage is 60@800rpm / 50@1000rpm 40@1200rpm 20@1400rpm (all at 0% TPS)
Why is it that way? i would assume that it gets higher the higher the rpm is above the target idle, as for example in a group N car you have the throttle permanently too wide opened for target idle, so rpm will increase and is catched with cutting more cylinders!?!

1b) Do you adjust the minimum TPS adc count for the increased throttle angle? or will TPS with the foot of the throttle e.g. 4-5% in a group N configuration?

1c) Why is there no lead (MAP) input for roving idle?

1d) i guess closed loop idle is not possible at all in roving idle configuration, so rough target idle has to be calibrated as a compromise of air supply and fuel cut percentage?!

2) What is ALS fuel cut used for? the other 3 parameters are clear, but fuel cut would just push fresh/cool air thru the turbo, wouldn't it be easier just to reduce the throttle opening/bypass then? what are the pro's and con's of less air/no fuel cut vs. more air and fuel cut at a certain point?

Thanks for your help...

PS: i would also like to get in touch with some ppl who have sucessfully tuned MS3 ALS to share some experiences... there seem to be very little detail information out there on calibration strategy... seems as if this is everyones best kept secret ;-)

[Suprazz]

I'm interested too

[mrx79]

hm, unfortunatly no reply's yet...

[tpsretard2]

you jack the throttle open to where you want, every setup is different, but an example my subaru i set it to 25% jacked throttle,

then you re calibrate the throttle so it read 0 without touching,

then you enable the roving idle and setup all the conditions and away you go.
You only need enough cut to keep the engine running at a low RPM, on my car it is not possible to idle lower than 1800rpm.

you never want a map load for roving idle as once the als is off it will always be atmosphere.
Some parts of the map you need to use fuel cut (off throttle) to stop very large back fires and to stop the engine pushing on, can also be used to help with EGT's


If you have never played with real ALS (like this) i recomend an EGT guage as egt can go sky high at a rate that will alarm you.

[mrx79]

Hi tpsretard2,
thanks for your answers.

Just a quick confirmation, as for rowing idle, do you agree that the cut percentage will need to be higher at higher rpm's rather then the opposite around like in the default calibration? Do you know what i mean?

As for ALS fuel cut, i understand... thanks a lot.

Best regards

[tpsretard2]

As rpm and load (tps) go up you will need less and less roving idle cut %

[mrx79]

As rpm and load (tps) go up you will need less and less roving idle cut %

hm, i'am sorry to ask again, but maybe i have still a miunderstanding here.
Just to avoid any confusion.
100% in the roving idle cut % = all cylinders shut off => engine speed will go down
0% in the roving idle cut % = all cylinders are on => engine speed will go up depending on ALS trottle up angle (as you saied ~20-25% in your example).

So if i target for a rough 1500rpm target idle and have 20% TPS as smallest angle and i have TPS=0 (as you saied, recalibrated the 20%, so MS will read it as 0% TPS / so actualy true closed throttle woule be -20%) the resulting engine speed with all cylinders firing would be of course >5000rpm (maybe redlline).

So i would assume (as saied no foot on the gas pedal) that as RPM increases, i increase the roving idle cut %'age, eventualy killing so much torque that the engine speed stops rising and falls back to my targeted 1500rpm.

Of course with roving idle a smooth idle is not possible, because i can only work in 25% increments (on a 4-cylinder engine) or to say it differently i can only decice every 180°CRK to fire or not fire a cylinder, and ever firing cylinder will fire with ~100kPa MAP = lot torque which will push the rpm's a little higher.

Where is my misunderstanding here, why cut %'age should to lower with rising rpm?

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Cf course if you drive off, you have to ramp out the cut %'age, to get the car going and drive off normaly in a "smooth" manner.
Cutting too much will propably result in a slugish/jerking drive off, too less cut %'age should create in something like a jump start i would assume.

Anything wrong here?

Hope you can clear up my mistake if there is any...
Best regards

[tpsretard2]

higher rpm = more air need by the engine = less cut needed.
higher load = more air needed by the engine = less cut needed.

there is no such thing as a smooth driving a car with roving idle.

This video kinda shows how jerky the car can get
https://www.youtube.com/watch?v=7nNikXYqYAM