E38 Throttle command cranking?

[DVR IMP]

06 vette only commands 29.4% with key-on, then while cranking it drops to 20.2%. Is there a spot to adjust only the cranking position of the throttle plate?

[Evolution]

Reducing the value of B1650 increases the throttle angle while cranking, but it also seems to change the calculation of the VVE table. I always change this value first to get the car to start on big cam set ups, then tune the VVE table. There are a few other things you may need to do to get your idle and coast down to idle sorted.

I've started to make a rough yet reliable base idle procedure for the E38's. No more holes in throttle bodies or touching the pedal during start up.

Some of the E38 operating systems are trickier than others to get right, so some patience is required.

[swingtan]

FYI: The amount of "throttle" or "Air flow" commanded during cranking, is set in {B1832}. Obviously, higher numbers give more airflow.

{B1650} is a value that the ECM uses to "calculate how much throttle opening may be needed for a given airflow". Hence why reducing that number makes the throttle open more. Reducing the figure tells the ECM there is less throttle area at WOT, so the ECM opens the throttle more to get the amount of open throttle area it thinks it needs.

Simon

[Evolution]

I've found that increasing B1832 still wont command enough airflow for a large cam, so I just stick with B1650.

[swingtan]

I guess it depends on the term "big"..... If you were trying to get a "huge" amount of cranking air, then {B1650} possibly helps, I've never used it for that. I've usually been able to get sufficient cranking air from {B1832} alone and only use {B1650} for idle control. Will be interesting to do some tests to see if {B1650} has a big effect on the cranking mode.

Simon.

[DVR IMP]

Comp Cams 54-469-11, "big" exh duration for sure. It sounds like there is an exhaust leak in the Fast 102 intake manifold!

[DVR IMP]

{b1650} @ 4000mm2 = 23.5% cranking. no change to {b1832}
@ 3000mm2 = 23.5% cranking. " "

I also tried the above with {b1832} maxed out and no different than above.

[swingtan]

Maybe you should describe the issue you are trying to fix and post a copy of the tune with a log. That would probably help.

Simon

[Evolution]

I guess it depends on the term "big"..... If you were trying to get a "huge" amount of cranking air, then {B1650} possibly helps, I've never used it for that. I've usually been able to get sufficient cranking air from {B1832} alone and only use {B1650} for idle control. Will be interesting to do some tests to see if {B1650} has a big effect on the cranking mode.

Simon.

The most I've been able to get with B1832 is 25%, but not all operating systems will let it go that high, some stop at 22.5%. But reducing B1650 by about 300-500, and setting B1832 to similar values of actual idle airflow (logged at idle) will let you get approx 30% throttle on start up.

[DVR IMP]

The issue I'm trying to cure is at the top of this post. I need close to 30% while cranking.

The OS 12614682 & Cal 12605731. I didn't save any of the logs for the cranking, too many. The airflow @ cranking would start @ 3mg/s and once it reached 250-300 rpm airflow would reach 6-7mg/s. So I left the stock values in because they seemed reasonable. I increased {B1832} 10% 3 times and seen no change and then maxed it out and seen no change.

[Evolution]

Post your tune so we can make some mods and see if we can get it sorted for you.

[DVR IMP]

here it is, and if anyone knows where to get an 06 6.0L auto stock file I'd appreciate it.