TPSACC spikes

jonfx4com · Post by **jonfx4com** » Sun Jan 29, 2006 9:14 am

can anyone figure out whats happening here. I get idle speed dips and its the TPSACC spiking the mixture up to way too rich. In the graph you can see the tpsacc goes up but the TP never moves. Not sure if its a general issue or a ms2 issue so I thought I would post it here first and if it gets bumped thats OK.

Bernard Fife · Post by **Bernard Fife** » Sun Jan 29, 2006 9:48 am

Jonfx4com,

Do you have MAPdot accel enrichment enabled?

Lance.

jonfx4com · Post by **jonfx4com** » Sun Jan 29, 2006 10:32 am

Yes I do it seems to work better with the ITB's

I added MAP and mapdot to the graph they seem OK, the map rises as the engine stutters but that seems to be effect not cause. BTW Is there a way to shorten a data log. This one is 2.5mb and it won't let me upload it.

Jon

jonfx4com · Post by **jonfx4com** » Sun Jan 29, 2006 10:37 am

I figured out how to get a section of the log so here it is.

jonfx4com · Post by **jonfx4com** » Sun Jan 29, 2006 11:31 am

Lance,
I think I found the problem. It is actually MAPDOT enrichment not TPSDOT, looks like megatune makes no distinction between map and tp enrichment and shows the two combined as TPSACC. Should ideally be split into two parameters or renamed as MAP/TPSACC to remove the confusion. Anyway it seems to be my MAPDOT settings that were wrong. I misunderstood how to populate the MAP enrichment bins, I had a very small KPA change giving a big splurge of fuel. When I say small, I mean smaller than the highest peaks of the noise on top of the signal due to the individual cylinder pulses! I havn't tried it yet as its now cold and dark in the UK. Will update this thread tommorow.

Jon

Bernard Fife · Post by **Bernard Fife** » Sun Jan 29, 2006 11:35 am

Jon,

Cool, I'm glad you got it sorted. I'm sure it will help to do as you describe.

Yeah, TPSaccel and MAPaccel are reported together, which is confusing (but also why I asked about the MAPdot accel).

Lance.

jonfx4com · Post by **jonfx4com** » Sun Jan 29, 2006 11:49 am

Lance,

It was your question that prompted me to look again at what TPSACC really means!

one more quick question while your online.

adv_deg = adv_offset + ign_table(rpm, kpa) + cold_adv_deg

does this mean that if I change my offset figure from 7 degrees to 17 degrees I can can subtract 10 degrees from each bin in the advance table which will make it *look* a lot more realistic (I guess my trigger wheel is not accuratley at 10deg BTDC)

Bernard Fife · Post by **Bernard Fife** » Sun Jan 29, 2006 12:16 pm

Jon,

The advance shown in the MegaTune spark table is the actual advance (Â°BTDC), and accounts for the trigger offset (the trigger offset is subtracted out before the timng is calculated). So you can change the trigger offset without affecting the timing table at all. However - this only applies if the trigger offset is accurate (i.e. MegaTune setting matches the actual physical offset).

If your offset is wrong, i.e. MegaTune doesn't match the physical set-up (it sounds like you think yours is), then changing the offset has a real effect on the spark table. In that case, a strategy might be to change the actual offset - by rotating the distributor or moving the pick-up, so that your actual timing matches the values in the Megatune.

However, you *should* be able to do as you say - add to the offset and subtract from the table.

I'd make sure to 'calibrate' the trigger offset quite accurately using a timing light and the 'Trigger Wizard' in MegaTune. There's more on that here:

http://www.megasquirt.info/megatune.htm#og

Lance.

jonfx4com · Post by **jonfx4com** » Mon Jan 30, 2006 12:27 pm

jonfx4com wrote:Lance,
I think I found the problem. It is actually MAPDOT enrichment not TPSDOT, looks like megatune makes no distinction between map and tp enrichment and shows the two combined as TPSACC. Should ideally be split into two parameters or renamed as MAP/TPSACC to remove the confusion. Anyway it seems to be my MAPDOT settings that were wrong. I misunderstood how to populate the MAP enrichment bins, I had a very small KPA change giving a big splurge of fuel. When I say small, I mean smaller than the highest peaks of the noise on top of the signal due to the individual cylinder pulses! I havn't tried it yet as its now cold and dark in the UK. Will update this thread tommorow.

Jon

Yup, that was it. My MAPDOT bin 1 value was adding 15ms of squirt for a 5kpa change, a flea fart at 25 feet was enough to make it think I had buried the throttle in the carpet. Problem now solved.

Jon

Bernard Fife · Post by **Bernard Fife** » Mon Jan 30, 2006 12:46 pm

Jon,

Great - I'm glad that fixed it!

Lance.