Xtau and MAP range

jonfx4com · Post by **jonfx4com** » Mon Jun 05, 2006 11:51 am

1.
Very impressed with the new Xtau stuff. Worked straight out of the box, just had to scale the time table by 0.5 as it was a bit too much for my setup.

2.
Is there a reason that the table gen wants idle to be >60KPA. Mine is much higher than that and really I want my entire map range to be compressed into the 65KPA to 100KPA range since my ITB's and lumpy cam never let it below 65 and all my drving is between 90 and 100 so I want more steps at the top end of MAP.

Jon

Bernard Fife · Post by **Bernard Fife** » Mon Jun 05, 2006 12:36 pm

Jon,

Great about the X-Tau.

For the table generator, the reason it doesn't like high idle MAP values is that such values indicate that the engine has a relatively radical cam, etc., making it much harder to model with simple parameters (the same is true for very small engines, very high rpm engines, or very high specific output engines).

So in those cases manual tuning is the best bet.

Lance.

jonfx4com · Post by **jonfx4com** » Mon Jun 05, 2006 2:16 pm

Lance,

what is the absolute resolution of MAP in the code. If all my MAP's are in a 20KPA range will I have a resolution problem?

IE if I go up in steps of 3 at higher map am I trying to measure it at a higher resolution that the ADC actually converts it?

Jon

Post by **grippo** » Wed Jun 07, 2006 7:20 am

jonfx4com wrote:Lance,

what is the absolute resolution of MAP in the code. If all my MAP's are in a 20KPA range will I have a resolution problem?

IE if I go up in steps of 3 at higher map am I trying to measure it at a higher resolution that the ADC actually converts it?

Jon

The ADC is 10-bit, so the resolution is 1 part per 1000. The processor works in tenths of a kPa, but the ADC resolution for a 250 kPa sensor is .25 kPa, so this is the actual resolution. Throwing real world noise etc, the practical resolution is probably about 0.5 kPa. So definitely better than 3 kPa.