Nissan ECU Tuning

Herb-86T · Joined: 15 Oct 2007 Posts: 18

Well, First off, im trying to tune my z31 but im having a few little problems. its an 88T ecu and im using a romulator. ive upgraded to 440cc injectors and rescaled all my ttp min and max values, k value, and injector latency values. My idle seems pretty rich, usually around 10 afr. but, whenever im driving around, it shoots up to 14 or even 15 and is pretty consistant. any ideas on what needs to be changed? ive bumped my k value up over and over but that doesnt seem to help too much. its already at 0190h. liveedit suggests 0167 i believe, so i think if anything the k needs to be reduced. I have a feeling it has to do with the latency, but i dont know what common symptoms are of having a miss-calibrated value. any ideas where i should look?

Herb-86T · Joined: 15 Oct 2007 Posts: 18

also, they are injectors from a mkiii supra, listed as 430cc actually. I found the pdf of injector specs, and these injectors seem relativly fast, so maybe my void didnt need much changing from stock value?

Herb-86T · Joined: 15 Oct 2007 Posts: 18

ANY input?? im at a loss here Sad

Bernardd · Joined: 15 Nov 2003 Posts: 111

It could be many things. First,
Start with a new binfile

change the k value mathematically

reduce the ttpmin table by the same factor.

reduce the tp scales on both timing and fuel maps by the same factor

set the entire fuel map 14.7

start car, let it warm up to operating temp, this is critical

rev car to various rpms and note afr, you want it to match the commanded afr between 2500 and 3500

if it goes rich when reving (holding the rpm) reduce the latency, if it goes lean increase the latency.

adjust the fuel map to a 12.1 afr

repeat latency adjustment, you want it to match the commanded afr between 2500 and 3500

if you can't get it too match exactly, err on the rich side

that should get you started. post up when you've get this far if you want more help.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

well i havent done everything there yet, but i did all the math, and using that pdf of injector values i came up with a new void and it seems like a MUCH better baseline tune so far. its running in much nicer AFR ranges and feels like it has more power. but one thing ive noticed is when coming to a stop and i put the car in neutral, the rpm's drop down to like 500 and feels like it almost stalls. Am i correct in thinking this is this a TTP min thing i should bump up a bit more?

Bernardd · Joined: 15 Nov 2003 Posts: 111

do the afr's match the fuel map most of the time? exactly which injectors are you using? it could be any # of thing causing it to stall or go to low rpm.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

im using injectors from the 7m-gte supra engine, 430-450cc about. using live edit set to show afrs on the fuel map, im running richer than those at idle, but up in the map its closer. i guess the void still needs some tweaking to fix that problem.

bemis · Joined: 14 Nov 2006 Posts: 17

Are those fuel injectors Peak-and-Hold or Saturated? With an 88T ECCS, they should be high impedance, or of the saturated variety.

Did you start out with the orginal software that came with the ECCS and then make your changes, or did you use something that is floating around the internet?

Also, make sure to turn off feedback control when your tuning.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

alright, i made a map set to 14.7 and tried wat benard asked me to do. well, at idle, it runs a full 1 afr notch richer, about 13.5-6. when i rev it up to around 2900 or so and hold it with little load, the afrs go richer by about 1 more to about 12.5. i guess the k and void both need some more adjustment.

nzniggles · Joined: 26 Aug 2006 Posts: 56 Location: New Zealand

"Also, make sure to turn off feedback control when your tuning."

What's the best way of achieving this?

Bernardd · Joined: 15 Nov 2003 Posts: 111

unplugging the o2 is the easiest way to turn off the sensor.

@ Herb - make sure your entire fuel map is set 0 in hex view and or unplug o2, i forgot to mention that before.

reduce your kvalue by observed afr/commanded afr = 12.5/14.7= .85 x current kvalue. don't forget to rescale your ttpmin-max, tp scales and make damn sure the car is fully warmed up or it won't match up.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

yes, i took the car for a drive first with my initial tune, then let it run in the driveway for a bit. i forgot to mention i set the closed loop bit to FF for the 14.7 afr map to disable it.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

ok, some new data:
With the fuel map completely set to 0hex, 14.7 afr and the Void set to 3A, TP scales scaled properly for each of the following 3 K values, and the o2 disabled....

K= 0148 hex, idle afr ~14.4 and AFR @ 2500rpm ~11.6

K= 0130 hex, idle afr ~15.3 and AFR @ 2500rpm ~12.3

K= 0162 hex, idle afr ~13.5 and AFR @ 2500rpm ~11.0

seems like i need to reduce my latency some more? Its at 3A, that already seems low to me... but i'll try it.

Herb-86T · Joined: 15 Oct 2007 Posts: 18

if datsunboy's post "standard CA18DET 370cc injectors have a 37 latency
" is correct, and the info on http://www.williams.co.tt/s15/inj_top-en.htm is also correct, then i guess my latency will infact be below 3A, and probably less than 37 also. ill use this info to come up with something to start with.

Bernardd · Joined: 15 Nov 2003 Posts: 111

looks like they should have a latency of 36 according to the link above. don't forget to lower your ttpmin as well.