ahawks9er

iTrader: (1)

Thanks for posting those, DNM. I may also give those settings a go and see if it helps my hot restart AFRs.

Zaphod

I am also very interested in the results of these settings, please post your findings...!

noname4me

I posted about having the same issues with my NB2 engine swapped into a 97 chassis with a Reverant built MS3X (OEM NA return type fuel system including FPR, OEM NB2 injectors). I moved my intake to the cold side, switched to the fully plastic body GM IAT sensor, and added hood louvers... Mechanical fuel pressure gauge shows OEM NA FPR working as expected with vacuum reference. Net result is that it still goes lean on hot restarts.

Plastic bodied GM IAT sensor has greatly increased accuracy reading the actual IAT as I can see the temps go up/down in the logs much more quickly in response to changes in conditions (ex: idling vs driving). Cold side intake and louvers are worth a solid 10 deg reduction in IAT's under hot, summer time conditions with lot's of full throttle and high rpm running. IAT's go down quickly once the car starts moving. So lot's of goodness with these changes, but it didn't solve the lean hot restart issue.

Lowering the MAT compensation values at high temp points helps the lean condition on hot restarts, but then it idles/runs rich outside of the hot restart condition.

I will give these tuning suggestions a shot, but I may not have the car out again for a couple of weeks. If anyone tries them and they help this lean on hot restart issue, please post up the results and details of your settings/tables.

ScottyP3821

iTrader: (2)

So what were every ones results? Just run more ase at higher temps??

EO2K

iTrader: (37)

I've seen this mentioned in the past, but never actually seen a part number. Is there a part number/manufacturer/source for this particular variation of the sensor?

HHammerly

iTrader: (3)

You can also add fuel on start enrichment taper when the engine is hot and add longer taper time, that seemed to solve it for me.
Here is the sensor you need
http://www.diyautotune.com/catalog/gm-open-element-iat-sensor-with-pigtail-p-62.html?osCsid=6096b400ab7db1a708383b5590c2df15

EO2K

iTrader: (37)

That looks like the metal bodied one. Isn't there one where the brass section is made of plastic?

DNMakinson

iTrader: (3)

Let me add info re: my post 19. The long ASE at temp works well to let the EGO take over and keep the AFR in line. However, please ignore my cold start settings, as my cold start is really bad.

ScottyP3821

iTrader: (2)

Thanks David!

HHammerly

iTrader: (3)

That is the fast responce unit, it has a plastic shroud with holes and a low mass sensor in it that reacts very fast to temp changes i bave been using that sensor. Read the description, in my opinion you DO NOT WANT THE BRASS ONE.

ScottyP3821

iTrader: (2)

Isnt the Brass for water though? Everyone uses the caged one its the best cause air hits the sensor directly.

deezums

iTrader: (3)

There's open and closed element brass sensors, open responds much faster, but still has a brass housing. I have a GM closed brass element CLT sensor, but DIYautotune open air IAT, as an example.

Some GMs had totally plastic IAT sensors, like late 90's s10/blazers.



My lean restarts have nothing to do with IAT, and I use diyautotune brass housing open element one. You do want the brass one, I don't see how you'd ever seal a GM plastic one against boost.

ScottyP3821

iTrader: (2)

With the last few firmwares. IAT heatsoak correction is what I am willing to say. Under control. I just would like to put I final say on whether or not it is boiling fuel or injectors causing the issues.

deezums

iTrader: (3)

I'd say the coils of the injectors might drift with heat, the kind they might see sitting directly next to the head with no fuel flow. More heat = higher resistance = less actual open time for the same PW? That's my take on it, at least.

I've managed to get mine under control by letting the motor rev high for a few seconds on a hot restart by using the cranking idle valve position, crank taper time, and a little foot manipulation. ~20-30 seconds of elevated idle, then my AFR settles down to 15.0 or so which is close enough for me.

I don't really know how it's possible, but I can rather smoothly idle 15-16.5+ or so AFRs at 850RPM or so. Quick throttle blips idling those AFRs are a little rough, they tend to bog the motor down below 850rpm but I still never stall. Seeing as how I don't stall, and how quick it goes away when I move, I don't really let it concern me any longer.

DNMakinson

iTrader: (3)

Use EGO. There has been consensus for some time that the issue is injector coil resistance increasing dead time. This is true both at MT and the MS forums. Although my method works, I don't like compensating for things that can be inherently fixed. How to fix? I see two approaches that can be applied singly or in combination: EV14 injectors, and return type fuel supply.

ScottyP3821

iTrader: (2)

On my old setup running rx7 460cc I used ego with it delayed for 19s which was when ase taper stopped. I would use tons of ego correcttion and it would blip into the 18s for a few sec and then settle around 16-15.7 till I started moving the car. It did idle fine. I'm thinking for my next go on the rx8 550s I'll add more ase above 130 cause Ive have it happen at that temp pretty regularly as the lowest temp.

aceswerling

I know this is a bit of an old thread but I'm having the same lean AFRs on hot restart that the rest of you are describing.

I can see the WB O2 come online and then the AFRs hang out around 17 until they slowly converge to the expected value around stoich.

When I started troubleshooting this, it seemed reasonable to guess that the problem was caused by ASE not running long enough. I set my ASR taper the same as DMakinson suggested and the rest of my settings were pretty close already. I'm still seeing the problem even with the extended ASE times though.

Is this something we just have to live with because of the heat soak on the IAT sensor? In my case, MAT doesn't look that high in the beginning so I wouldn't expect the MS to lean things out because it's excessively hot. Also, I'm using the GM sensor that Rev sent along with my MS3 and that seems to be the one people like.

I'm attaching a small log file in case it'll help. Many thanks in advance...

deezums

iTrader: (3)

Extending the ASE time is not enough, you need to increase the ASE percentage as well.

Are your MATs really that high on a hot restart? I doubt they are, it's nearly always in the injectors. They're little solenoids, they react different when they're hot. They only get hot when the fuel stop flowing.

That's my take on it.

aceswerling

Thanks, Deezums. My ASE % was already higher than was suggested so I figured I was OK there. You can see my graph below.

I'm running the Flow Force injectors everybody likes so I was hoping they'd be OK in handling the heat.

deezums

iTrader: (3)

If you are having hot restart problems you're going to want that graph to look like the letter "u"

You shouldn't be having lean hot start problems from ev14's though, not anything like on old injectors. You could try adding some extra priming pulsewidth at high coolant temps, or even more cranking pulsewidth. You might also try and hold 1200 rpm for ten seconds after you start instead of 850, the extra rpm will increase pulsewidth and make the problem less noticeable.