I'm still not clear on how to tune x-tau - but then, I am blond.
Here's a scenario. The engine is at 2000 rpm, 30kpa (very light throttle), 5th gear. I now step on the gas and MAP moves to 70kpa. AFR spikes lean, then rich (according to AE wizard) then settles on the AFR as per the VE table. Rpm has stayed at 2000rpm being in 5th.
Which cells on the Tau table do I have to adust? Just the 30kpa cell, just the 70 kPa cell or all in between? In other words, which cells are being used by the x-tau algorithm during an AE event such as this?
X-tau tuning
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
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Philip Lochner
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X-tau tuning
Best regards
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
The X part is the % of the air fuel mix that goes onto the walls. This is a function of how well the fuerl is mixed, the port geometry, the temperature, and a bunch of other things. The tau part is how fast the fuel is sucked into the air stream after it is initially deposited. This is a function of rpm (or air speed) and map. At high rpm the fuel is sucked off the walls immediately, just like blowing on spilled water on a table will dry it out quickly. That is why you don't need much accel enrichment at high rpm. High MAP holds fuel on the wall from the pressure, while high vacuum quickly sucks it off. Note that rpm and map fight each other when you nail the throttle, but rpm wins out eventually.
To answer your question, the tau table vs rpm and map is just like the ve table, you have to tune all the points involved in going from rpm1,map1 to rpm2, map2.
To answer your question, the tau table vs rpm and map is just like the ve table, you have to tune all the points involved in going from rpm1,map1 to rpm2, map2.
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Philip Lochner
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Thanks Mr Grippo!!
That gives rise to two more questions, if you'll bear with me.
1) Does that then mean that if I have eg 7 cells between 30kpa and 100kpa at 2000rpm in 5th (meaning rpm is "fixed"), that the Tau times of those 7 cells will be implemented consequtively, as in, added together?
2) Would it be sensible to attempt tuning the Tau table by moving the operating point between two adjacent cells? (Not that I think this will be easy)
That gives rise to two more questions, if you'll bear with me.
1) Does that then mean that if I have eg 7 cells between 30kpa and 100kpa at 2000rpm in 5th (meaning rpm is "fixed"), that the Tau times of those 7 cells will be implemented consequtively, as in, added together?
2) Would it be sensible to attempt tuning the Tau table by moving the operating point between two adjacent cells? (Not that I think this will be easy)
Best regards
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
The taus do not add as you move across the rpm, map grid. There is just one tau at any time (interpolated from the current rpm, map) and it appears in a control loop that is always trying to converge to a stable point (that is to no fueling correction). 1/ tau is the gain, so the smaller the tau the quicker it will converge.
As far as tuning, I haven't had the time to try tuning it, but Lance and others have, and Lance has some advice in the manual. If I were doing it I guess I would datalog some mild to severe accelerations and then look at the cells that were traversed. Then I would reduce the AE enrichments by 25-50%, turn on the tau correction and go from there. If it bogged I would richen the initial tau cells. If I had black smoke or other overrich indication at the end of the accel, I would lean out (lower) those tau cells.
As far as tuning, I haven't had the time to try tuning it, but Lance and others have, and Lance has some advice in the manual. If I were doing it I guess I would datalog some mild to severe accelerations and then look at the cells that were traversed. Then I would reduce the AE enrichments by 25-50%, turn on the tau correction and go from there. If it bogged I would richen the initial tau cells. If I had black smoke or other overrich indication at the end of the accel, I would lean out (lower) those tau cells.