Hard starting when warm.

Sam Powell · Post subject: Hard starting when warm. (Mon May 23, 2011 6:51 am)

STill have the old MSI ECU in place. Cold starts are not bad. It could use a little more after-start-enrichment, but it is already maxed out. And the fuel map is respectable. It is a little rich, with a few cells that are richer yet, but nothing affecting drivability.

When I start it up warm, it takes about a full minute for it to run right. I have to keep poking the throttle to keep it going, and this is when the error codes for the Inovate sensor pop up. The gauge is reading way lean at this point, except this could be from a too rich misfire.

I know the intake manifold gets VERY hot when parked. I have not wired the fan yet to keep it running when shut down. Ed gave me a circuit diagram about a year ago for a circuit that would allow it to run initially, but then stay off after it shut off one time, but I have not done this yet.

So for now, is there tuning I could do that would improve the hot start? With the old Excell ECU there was a tuning table for hot start that was keyed to a sensor on the intake. When tuned to enriched the mixture when the manifold was hot, this hot start problem was mitigated. I kind of think the design of the slant intake creates a challenge in this regard for some reason. I kind of remember all my carbureted slants having a similar nature.

Thanks for any tips.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Dart270 · Post subject: (Mon May 23, 2011 8:50 am)

Sounds like more cold enrichment (overall) is probably needed, and drop the "prime" pulse and/or after start at higher IATs. I have had this problem, but fixed it this way. I ended up with WAY more cold enrichment values than I would have imagined.

Lou

_________________
Balancing out the driver's weight for more than 50 yrs

Dart270 · Post subject: (Mon May 23, 2011 8:52 am)

Also, I don't think MSI has enough settings available (# of variables) to really make it perfect, unless you rig up an IAC or use a big enough idle speed kickup (solenoid). Compromises will have to be made, I believe (like high idle during mid-late warmup).

Lou

_________________
Balancing out the driver's weight for more than 50 yrs

Sam Powell · Post subject: (Mon May 23, 2011 7:31 pm)

Thanks Lou, this is exactly the kind of feed back I was hoping for. Are cold start enrichment values in play for a warm start? OH, maybe after start enrichments are, and they are the culprit? I cannot remember off hand, is there a pw value for after start, or just time?

Sam[/i]

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Dart270 · Post subject: (Mon May 23, 2011 9:08 pm)

Not the cold start overall enrichment, but the prime pulse and afterstart enrichment. I think both of the latter have a temp dependence you can tune. Man, it's been a while since I played in Megatune... Next week I'll get back into that on the turbo '68 Dart.

Lou

_________________
Balancing out the driver's weight for more than 50 yrs

Sam Powell · Post subject: (Tue May 24, 2011 4:48 am)

Let me run this by you again to be sure I understand what your thinking is.

So you think maybe the lean reading on the gauge is false, created by a rich misfire? And this rich misfire is caused by too much prime pulse when hot, and too much afterstart inrichment when hot? I will hook up the laptop tonight and see what options there are. This is a pretty important thing to get worked out. It is kind of a pain to drive locally now.

Matt says he has put the MSII on the stym, and it is working OK. Now he is to put my distributor on their machine and spin it with a mock up of my ignition to test the entire set up. When he gets around to this hopefully it will not be too long before I can get the MSII back on.

As soon as this is done, I can get your MSI back to you, along with the relay box, as I am buying a new one of those in this deal.

IN the mean time I will check on what the tunable parameters of MSI start up are.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Dart270 · Post subject: (Tue May 24, 2011 5:04 am)

I don't know anything from the O2 gauge on startup. I would not trust any values there until the engine has run for a minute or two at least. I am just saying those two parameters might be set too rich when hot.

Lou

_________________
Balancing out the driver's weight for more than 50 yrs

Sam Powell · Post subject: (Tue May 24, 2011 7:40 pm)

HI Lou, I fussed with the prime pulse and it got better, but still not great. It was set at 6 ms above 170, and now it is 4.5ms. When I put it down to 3ms, it would not start at all. It now starts with just a little more cranking, which seems to be maybe a good thing. It then ran better after warm start than it did before the change, but not well for almost a minute. It really seems to call for opening the throttle just a hair for the first minute on a warm start. I wonder if I could engineer something there?

It seems as if the after start enrichment is not temp variable. It just is what it is. Maybe MSII is. I don't remember.

I did take the car out and tuned for half an hour this evening, and leaned out some of the rich cells. I also cut down on the TPS enrichment some, and cut some fuel out on the decel. I took fuel out until it bucked when I let up on the gas, and then took it back up just a bit until the buck went away. I could likely fine tune it a bit more.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Dart270 · Post subject: (Wed May 25, 2011 5:03 am)

Sounds great. You may have too much afterstart enrichment (too many pulses, length of its effect)?

Lou

_________________
Balancing out the driver's weight for more than 50 yrs

GunPilot · Post subject: (Wed Jun 01, 2011 3:09 pm)

I was having a similar problem (still am) but I made it better using a thing called 'additional fuel' under Other Fuel Settings (I'm using Tuner studio, so I don't know what it is under Megatune, although most things are the same.)

I set the number of cycles to 200 and it did improve the hot starts. No idea why but it did.

I'll rant some about my throttle body over in my FI thread...

_________________
It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Sam Powell · Post subject: (Thu Jun 02, 2011 11:51 am)

The tuning settings are a function of the firmware in your ECU, not the tuning software. The tuning choices that show up on your screen actually come out of the firmware. I understand nothing about that beyond what I just wrote.

It became clear to me that this engine wanted to have the throttle cracked a bit when first started up warm. I designed and built a choke cable activated slide gizzmo which pokes out and slides between the idle set and adjustment screw thus lifting it a bit. This improved the warm start situation considerably.

However, there is an idle air control valve in the TB that is a stepper motor type. I was wondering if it is possible to control this motor's position with a rotary knob or maybe a momentary DPDT rocker switch. Is there a circuit that can be made, or purchased to control a stepper motor of this type? That would be more flexible than my choke cable set up.
Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Sam Powell · Post subject: (Fri Aug 05, 2011 4:51 am)

Got new AEM wide band gauge installed and working. Since this one comes on line instantly, without the annoying time delay of Innovate's start up song and dance, I can tell the engine is dying from going lean. When the afterstart enrichment runs it's course the AF ratio goes from 14.5:1 to 17.5:1 and it stalls.

Any suggestions from that information about what tuning tweaks I could make?

Good things are happening now. Peter Florance is in the loop, and we are making plans for me to get down to VA beach and get my MS II installed and running. I am certain he will have the knowledge to fool with the start up settings. When I first contacted him, he was keeping a client's Dodge Dart for for a few days which he had installed MS II on, for the purpose of tweaking the start up settings. I did not ask, but suspect it was a v-8, and not a slant.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Matt Cramer · Post subject: (Fri Aug 05, 2011 12:50 pm)

Sam Powell · Post subject: (Fri Aug 05, 2011 6:23 pm)

Mat, I think you are right. Absolutely. It is only a problem when I drive a short distance, and the engine is not fully warmed up, shut it off, and then restart it and drive. For about the first mile or so it runs extremely lean, then gradually returns to a good range. I am sure the computer is getting the message that the engine is fully warmed up, but in fact is not.

You are a bright young man. I have two sensors. One is in the block and feeds the gauge. The other is behind the thermostat, and the stock position. It makes tons of sense that the water behind the thermostat, which may not even have opened yet has gotten near boiling. You know, that temp when the gauge spikes right before the thermostat opens.

When I first installed Mega Squire maybe 5 or 6 years ago, I had the ECT sensor reading from the block location. It took so long to warm up, that I switched it over to the thermostat housing location mainly for quicker warm up and better mileage. Sometimes the block temp would not get above 150 by the time I got to work. I switched on the advice of several forum members back then.

Any ideas about a strategy here now. I could wire in a SPDT switch to temporarily raise the AF ratio during the warm up by switching back over to the block sensor during the one or two minutes the engine thought it was warmer than it was during the restart situation. This is a pretty important idea for us slanters trying to build drivability into an EFI slant.

I guess I can see that going back to the block location might be fine, but I would have to recalibrate the warm up coefficients.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

Sam Powell · Post subject: (Sat Aug 06, 2011 3:21 am)

Would someone discuss please, the impact of location of IAT on things? Why should the actual temp of the intake air right before the TB not be the best place to sample air temp. If the air there is indeed warmer,why would this mislead the ECU into thinking the engine is warmer than it is. I guess I do not understand how the ECU uses this information in the fueling strategy. Is it supposed to be sampling actual air temp as it enters the TB or temp of air outside engine compartment?

1. Can the sensor being in a warm environment create a reading hotter than the air itself?

2. Should not the sensor be placed AFTER the intercooler? It was suggested putting it in the air filter. Would this not then give a false reading any time it went into boost? I don't know. This is an honest question. I am not arguing for one thing or the other. I am just trying to understand the practice and science. I could go look at my Toyotas but they are NA, and not boosted.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

	Slant Six Forum, Forum Index -> Fuel Injection	All times are GMT - 7 Hours Goto page 1, 2 Next
Page 1 of 2