Leeroy_25

Hi Guy's I need to try and look at my cold start and idle as it runs pig rich when cold and even when warm I would say is still a bit rich. Can anyone give me pointers as to what sort of AFR's I should be expecting to see from cold idle and as it warms up to normal operating temp. At the moment we are at 10-15°C cold start maybe.
I gather I might need to warm it up first and check the AFR at warm idle and see if that is okay and then pull some fuel out if need be and check idle again from cold. I think it isn't far out when warm as it idles okay. just a bit smoggy but that could be the premix as well.
any idea what sort of temp correction values I am likely to be looking at for a guide? And if I should be putting in any timing correction too?
I am running a microtech LTX-12 ECU by the way. My tuner is on holiday for a bit and plus I want to learn some basic tuning myself and have wanted to for a while. Now I have a laptop, leads and software it's ideal!

Cheers
Lee

j9fd3s

iTrader: (3)

idle is the perfect place to start tuning, worst thing you can do is stall it, and all the same principals apply at higher rpms/loads too, its just that they happen faster.

anyways, Mazda picks a fairly rich AFR for idle, its around 12.2:1, although at idle what you want is the highest vacuum/most stable rpm. i don't know the microtechs, but the haltech looks at the cells around where you are, so you need to kind of make those the same, and then fine tune it. don't be afraid to try a little lower rpm than idle, and then a few rpm points off idle too (1000, 1500)

timing at idle is -5L and -20T, but that is mainly for emissions, the non emissions cars ran 0 and -15T. you might also try running the leading and trailing together.

for the cold start stuff, Mazda has it off by 65c, and when its on, you'll just have to see what your engine likes, the older haltechs aren't great at this part.

for the air temp vs fuel and timing, i'd wait until the other maps are ok, and then circle back, i'd expect to add a small amount of fuel at low temps, and then maybe pull a degree or two at high load and low temp

t-von

iTrader: (8)

Hmm never knew Mazda had the mixture that rich at idle. Which model is that? I've gotten my 20b to 13.7 without the air pump running on negative split with my Haltech E11v2.

Leeroy_25

I guess I will just see what it is happy at. but I have a starting point either way.

What do you mean by negative split by the way?

Thank you
Lee

KNONFS

iTrader: (14)

Negative split means that the Trailings fire before the Leadings. Normally, the Leadings fire first, and the Trailings fire 10-15 degrees AFTER the Leadings.

Leeroy_25

I thought it sounded Timing related! Is that a usual thing to do? Would that only be done on idle? I assume there is no advance happening at idle. Just the 5deg and 20deg firing? So maybe I can play with the trailing timing if my ecu allows and see what happens.
On a side note. AFR's mentioned above are presumably for warm idle. How much richer would you normally expect to be when cold? I know that has a lot of factors and will be different per engine but for instance would you be going down into the 11's or 10's even? Or should it stay fairly close?
Thanks
Lee

Leeroy_25

I am going to move this over to the ECU section now.. I
made a start today and need some more pointers! if you can help pop over to the microtech thread in the ECU section please.
Thank you
Lee

j9fd3s

iTrader: (3)

all of the Rx7's, and cosmo idle at -5L and -20L, the Rx8 will idle at -5 and anywhere between +10 and +15T. the pre-emissions 13B idled at 0 and -15.

Mazda picked a warmed up idle AFR that resulted in zero misfires, as a misfire = high emissions. they then add the air pump, so that the extra fuel can burn in the exhaust/cat. it sounds a bit wonky, but it actually runs quite clean.

one of the goals of the Rx8 engine was to be able to run 14.7:1 AFR without misfires, as this means they wouldn't need the airpump, and efficiency would improve too (although they then put it in a heavy car with low gears...). moving the ports was the big change that let them do this, but they also changed to a better spark plug and ran the different trailing timing.

for warm up afr, i don't run too much richer, maybe 1/2 point?

Leeroy_25

Thanks for then info.. Dors moving the timing make it run leaner in itself or five you scope to pull out more fuel? Just curious.
Also, I am trying to get a picture of what and idle curve should look like and a water and air temp correction curve should look like to see if mine are heading the right way. I posted in the ecu section but no reply yet. Can you offer any pointers? Should it lean out on over run for instance? Or be richer that it is at idle?
Also my water temp correction values seem really high as a percentage but obviously that's what the motor seems to want to get a decent AFR. Definitely wants to be on the richer side though so it seems.
Thanks for assistance

j9fd3s

iTrader: (3)

changing the timing might affect AFR a little, but with the Rx8, the timing change is one of the things that allowed them to run it leaner, along with a knock sensor.

for the temp vs fuel curve it can be really big, the stock one is HUGE. just go by how the car runs.

at overrun, it can almost have no fuel at all, although every stock ecu puts a little in, to keep the cat happy.

once you get the thing running nicely, you can try leaning it out here and there. i dont know about the microtech but the haltech interpolates between maps and cells, so you kind of need to be in the ball park first, and then fine tune from there

Brekyrself

iTrader: (30)

Perhaps I can't find the thread however are stock Mazda maps available for the FD? I know were talking about early 90's ecu's with much less capability however would like to take a peek and what they were doing.

j9fd3s

iTrader: (3)

ive never seen an FD map. the Rx8 map is pretty easy, you can just log the car and drive around, and the FC maps have been posted. i think i've posted the 20B maps too, its 2"x2" and its rpm and LOAD, so it defies translation into rpm and manifold pressure