The Silver Buick's well Silver Buick!

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

I'll look for one Scott, I believe I made one or two in the last month.

Before starting it for the day, I'd leave the key on until the O2 started reading, then fire it up, and it'll run pretty rich, 9.5-10.5:1'ish (work on that later) for a couple seconds, then start leaning out until it's at 16:1 AFR and stall. Then I'll fire it right back up and it'll start rich until the ASE tapers off and idle at 12.5-14.0AFR during warm up, and eventually 14.5+:1 AFR around 140*F.

[squirrel]

Re: The Silver Buick's well Silver Buick!

Need to deburr the linkage on the vacuum choke pull off.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

yuk yuk yuk.

[squirrel]

Re: The Silver Buick's well Silver Buick!

sounds like a weird problem, do you think it can be fixed by changing some parameter? almost sounds like a software bug?

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

I thought software too, but it seemed to go away when I had the 290-08H cams in it. Plus it doesn't do it at all when warmed up.

As I said, I think it has something to do with where the Idle Air Control valve is during cranking versus where it's at when the engine is cold, and it can't handle the air flow change with out the fuel change. Because it fires up so quickly on the second try of the key, I'm thinking the IAC doesn't have the time to reset into the cranking position. The problem is more apparent/worse at lower elevations, I'm guessing it leans out easier with the denser air?

[squirrel]

Re: The Silver Buick's well Silver Buick!

interesting. I like a fast idle screw on a choke mechanism better, because it doesn't starve it for fuel as it increases idle air (it just holds the throttle open more).

Is there any way to link IAC position with temperature to control the mixture?

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

Actually yes they are linked. The warm up % table and the IAC table are linked by temperature. So if you are on the IAC table and have the IAC openning more at 120*F instead of the point at 100*F (allowing 20*F more warm up before dropping the idle) the warm up % point automatically moves from 100*F to 120*F. I just have to adjust what that percentage more fuel should be. To set it, I just fire up the car cold, adjust the IAC to get a good high idle rpm, then adjust the warm up % to a health warm up AFR (~13-13.5%), then as it warms up I check the IAC and warm up % settings, the x-axis it coolant temp.

Just a week or so ago I found a setting I didn't know about for the IAC during cranking. It has a place to set the IAC for cranking above(hot) or below(cold) a temperature of my choosing. My cold value was set at 0*F so it always cranked on the warmed up setting. So I think my issues were starting there.

Then of course, since I decided to add a ton of ignition advance to the system, I leaned out a bunch of the lower load areas of the VE table, so that it idled fine warm, but I had to bump my warm up mixture a bit to keep it idling cold and getting the ~13.5 AFR (now 15'ish warm).

**Oh, and it's a six point table, and it has a linear interpolation between the points.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

For clarification, it treats cranking differently than running/idling.

The settings allow you to set it so that you can give it more or less air during cranking than at idling, and a cranking pulse width on the fuel injectors can be adjusted, so that between the two you can set the AFR for cranking independantly from while it's running. I think Scott wants to see my pulsewidth while cranking to see if that's my issue, the transistion from cranking pulsewidth to idling pulsewidth maybe fubar'd.

And the After Start Enrichment (ASE) lets you have it run a tad richer after it fires up, so if you have a very lean idle setting it'll stay running right after start up and gradually lean out over a specified amount of time.

[SuperBuickGuy]

Re: The Silver Buick's well Silver Buick!

how do you like the new cam?

[dieselgeek]

Re: The Silver Buick's well Silver Buick!

interesting. I like a fast idle screw on a choke mechanism better, because it doesn't starve it for fuel as it increases idle air (it just holds the throttle open more).

Is there any way to link IAC position with temperature to control the mixture?

The IAC should act exactly as someone pressing their foot on the accellerator pedal. I.e, only allows more air into the engine. There shouldn't be a link between IAC position and mixture, however the rest of the calculations should handle the proper mixture.

I am betting what's going on is he has a wildly varying pulsewidth during the transition from cranking to running. If that's an issue (almost a guarantee), then the next step is to figure out which input or parameter is causing the fueling to do what he's seeing. I'm thinking the IAC is only adding confusion to the issue, a lot of times I make guys unhook the IAC and first sort out the tune using their foot as the IAC. If the engine is turning slow at cold start, add a little air with your foot - if just a slight crack of the throttle doesn't solve the issue, then the issue isnt' related to airflow, it's related to fuel flow (not matching airflow).

My preferred way of observing this is to watch the PW1 line in the datalogs or strip charts, during a startup where the problem happens.

So post us up a pic of a log Randal!!

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

how do you like the new cam?

Pulls more vacuum, I think it definately is working well with the 3.08 gears, even towing a trailer. Haven't been to a track yet.



You can tell this start up issue is really just a small annoyance in the grand scheme of things since I've logged several (tens of? now..) thousands of miles on the car since the EFI conversion.

[squirrel]

Re: The Silver Buick's well Silver Buick!

interesting. I like a fast idle screw on a choke mechanism better, because it doesn't starve it for fuel as it increases idle air (it just holds the throttle open more).

The IAC should act exactly as someone pressing their foot on the accellerator pedal. I.e, only allows more air into the engine. There shouldn't be a link between IAC position and mixture, however the rest of the calculations should handle the proper mixture.

The carb fast idle works by acting as if someone is pushing the throttle, as you say. But the carb automatically adds more fuel as it adds more air, because that's how carbs work. With EFI you need to add more fuel because of the IAC adding more air...it doesn't do it automatically, does it?

Looks like fun to figure this out, I'm sure Randal will get it done (especially if he gives you the data so you can help diagnose it!)

[dieselgeek]

Re: The Silver Buick's well Silver Buick!

interesting. I like a fast idle screw on a choke mechanism better, because it doesn't starve it for fuel as it increases idle air (it just holds the throttle open more).

The IAC should act exactly as someone pressing their foot on the accellerator pedal. I.e, only allows more air into the engine. There shouldn't be a link between IAC position and mixture, however the rest of the calculations should handle the proper mixture.

The carb fast idle works by acting as if someone is pushing the throttle, as you say. But the carb automatically adds more fuel as it adds more air, because that's how carbs work. With EFI you need to add more fuel because of the IAC adding more air...it doesn't do it automatically, does it?

The EFI works the same as the carb (at least, the way Randal is using it). Opening the IAC, just as opening the throttle, will cause the manifold pressure to increase (less vacuum). That in turn causes the EFI to see "more load" thus, it adds the extra fuel that's scheduled for whatever load & rpm point the engine runs at when the IAC opens up.

You may be thinking of Alpha-N type EFI where the throttle position is the "Y" axis on a fuel table. In that case you'd be correct, but in Randal's case - he's using the Speed Density method, which uses the MAP sensor's data as it's "Y" axis on a fuel table. RPM is the X axis in both cases.

Looks like fun to figure this out, I'm sure Randal will get it done (especially if he gives you the data so you can help diagnose it!)

When debugging little issues like he's working on now, I found it's better to lean back on "old school experience" that the carb guys have plenty of. If something doesn't look, sound, or behave properly, look at the simple stuff first. With EFI there are so many variables that you can apply to fueling quantity, it's very easy to do too much, and have fuel delivery that's all over the place. That's likely what's going on here.

[squirrel]

Re: The Silver Buick's well Silver Buick!

Ok, it makes sense now.

I have a pellet stove, that heats the house. Sometimes parts of it act up, and I go looking for info. The brand name pops on on various fori, and folks talk about their good or bad experiences with the company getting tech support. Seems a common theme is that the guy says "put the phone next to the stove, so I can hear what it's doing". That's a very good way to troubleshoot over long distances! but some stove owners think it's the stupidest thing they've ever heard of. Of course those are the same people who buy a complex machine that requires regular maintenance, then bitch when it breaks because they don't maintain it.

Just thought I'd throw that out there.

[TheSilverBuick]

Re: The Silver Buick's well Silver Buick!

The EFI works the same as the carb (at least, the way Randal is using it). Opening the IAC, just as opening the throttle, will cause the manifold pressure to increase (less vacuum). That in turn causes the EFI to see "more load" thus, it adds the extra fuel that's scheduled for whatever load & rpm point the engine runs at when the IAC opens up.

Not quite as I understand it Scott. The IAC opens, but unless the engine is actually under load, the vacuum does not drop, the engine idles up as it gets more air and the fuel matches it on the table. Usually the vacuum will go up because the extra rpm.

I don't think Jim was clear in his statement, because the carb's fast idle is supposed to work in conjunction with a choke butterfly to actually richen the fuel mixture during high idle too. Open lower throttle blades, but close off the upper throttle blades. That's what I'm trying to simulate by opening up the the IAC cold (attains more rpm) and then using the warm up % to richen the mixture at that rpm and load from where it is fully warmed up.

My warm up works pretty good. I have a cranking to running transition issue, I think. Because once it starts it warms up just fine and the idle drops as it crosses set temperature thresholds, and the AFR's gradually lean out to the warmed up AFR's as the rpm's drop (which it would be richening up if the fuel was left alone).