dwink

iTrader: (1)

Hey all- my Miata starts and idles like a champ when cold or warm.

When hot- it won't idle without me helping with the throttle for a few seconds.

Once I get going, things are fine.

dwink

iTrader: (1)

Pic below

dwink

iTrader: (1)

Taper settings

18psi

iTrader: (76)

why is it not linear, or close to it?
and why is the taper so ridiculously high?

dwink

iTrader: (1)

I don't really know the answer to either. I believe this is how the base map looked when I got the initial tune.

Any better starting points are appreciated!

rwyatt365

Think about what ASE is doing for a minute...

Let's say that "hot" is 190*F. Your ASE settings are telling the MS to add 32% more fuel after starting for about 2 minutes.

Do a log when you perform a hot start. Are you pig-rich? This (above) is the reason why. You don't say what car this is, so it's really hard to know what's going on.

I have a 99 with the return-less fuel system. On hot starts the fuel has a tendency to heat-soak in the fuel rail (because it has nowhere to go) so when the hot fuel hits the hot manifold it vaporizes quicker than normal (as in "no puddle in the manifold") so the engine will run very lean for about 3/4 of a minute in a hot start. So I have to do some weird things with ASE to "flush out" that hot fuel with a bigger than normal ASE percentage for just under a minute. If you've got a full-return system, you shouldn't have to deal with that. And even with this "flush", my ASE percentage doesn't go above 20% when "hot".

dwink

iTrader: (1)

Super helpful! That makes a lot of sense.

Car is a 94 with no mods to the fuel return, so I suspect that is the problem. It does run rich and is fussy for a couple of minutes. I suspect I could bring that down close to 100%.

aidandj

iTrader: (5)

You have a return fuel system then. So that problem wouldn't affect you.

rwyatt365

^^^^ This...

Your ASE percentage should drop as CLT increases - how much is dependent on your car. Follow this simple rule, "Tweak. Measure. Analyze. Adjust. Repeat." Also, make sure that you note (or log) what the starting CLT is. If you don't, you'll be chasing you tail if the start temps vary by a lot (i.e. cold mornings vs warmer afternoons).

Likewise, your ASE taper should drop as CLT increases. Remember, the taper is measured in cycles so the length of time that the ASE is in effect (dictated by the taper) depends on your idle RPM divided by the taper cycles (in minutes). My rule of thumb with the taper is, "The hotter the start temp, the shorter the taper time".

Enjoy!

curly

iTrader: (25)

Whats your warmup enrichments look like?

rwyatt365

Yeah...watch out for those too 'cause they're "on" even after ASE shuts down (typically).

Braineack

iTrader: (62)

post a log.

ASE lasts like a few seconds. warmup is what matters, but it could also be your intial idle duty table or even just the AIT corrections from heatsoak (where is your AIT located?).

Braineack

iTrader: (62)

2 minutes? ~400 cycles is like 2 seconds (unless seconds was selected -- think ms3 can do that).

ASE should only be active for a few moments.


this is why we need to see a log and msq for all MS tuning questions.

18psi

iTrader: (76)

step 1: learn exactly what ASE is, how it works, and how it affects your tune.
you cannot move forward until you do

but like already said: it's very short and if your car has issues longer than a few seconds after start, then you have other things that are off

DNMakinson

iTrader: (3)

ASE taper can be set to be seconds or cycles. The graph will show cycles regardless. With the information given we don't know if the taper is 400 cycles or 400 seconds.

RWyatt: Hot fuel on restart actually affects injector coil temps, and therefore dead time. That is the leaning effect you see, rather than a change in fuel evaporation rate.

rwyatt365

Since I saw "cycles" in the plot, that's what I based my comment on.

Thanks for the info about the inj coil temps. So, am I just cooling the coils by flowing more fuel through the injectors on hot starts (not to hijack the thread)?

DNMakinson

iTrader: (3)

I think that is the correct perspective. Jason was the first to propose hot coils, and it makes good sense as higher temp = higher resistance which yields the same effect as low voltage (both reduce coil current), and we all know low voltage increases dead time.

noname4me

One comment... Lean running on hot restarts is definitely an issue with the OEM NB2 injectors, MS3X, and the NA return type fuel system! I have been fighting that problem for a while now...

Braineack

iTrader: (62)

where is your AIT located?

rwyatt365

AIT is just before the TB, in the tube from the IC.