E38 without VSS

[lysergic]

I read somewhere that if the e38 doesn't receive a VSS it will use the base spark table only. Is this true? I am trying to pinpoint a possible reason for my car not responding too well to tuning on the dyno and being consistently low on power.

I have a TH400 without a speed sender in it.

Also, does no VSS have any impact on the throttle not staying open throughout the rev range or anything like that?

[Matty85]

Ive got the same question

[07GTS]

u will need a VSS otherwise it will think its always stationary, so many tables wont get used as they should, idle spark table is only used for idle soon as u get a few percent throttle into it it will go into the main spark table and then coastdown uses its table also, i cant see it working too well without it

[Matty85]

Ok thank you very much, what do I need to change in the editor if I put in the Dakota digital vss sensor in?

[Matty85]

Which vss from Dakota should I get for a th400? 128k? I?m not running a speedo

[07GTS]

im not sure on the pulse range needed but i think its adjustable for a curtain range in the tune, i think its up there tho cos it can come from the abs sensors

[lukearmstrong1990]

typically the VSS the PCM sees without an input it 255mph all the time. the speedo on the dash may use a wheel sensor source as default and work.

the E38 I have done with TH400 use the wheel sensors for the dash cluster speedo and the PCM sees a constant 255mph input.

the PCM think the car is always moving. you may have some issues coming to a coasting stop and returning to idle with no road speed. the E38 controls idle best in adaptive idle strategy. I usually just set the enable VSS limit to a max value meaning adaptive idle will always try to control and maintain idle despite what is occurring dynamically. I have found that with aftermarket cams adaptive idle is the most capable as opposed to trying to control everything without adaptive idle airflow corrections.