After-start idle control (cold)

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Jim_Blackwood
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After-start idle control (cold)

Post by Jim_Blackwood »

I can't seem to find the right place to control the idle behavior coming off initial cold start. The engine fires up after a second or two of cranking and then it just dies unless I have my foot on the throttle. If I keep it running then it settles into a fast idle and is fine after that. I'd like to hear suggestions.

Jim
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Re: After-start idle control (cold)

Post by turbo conversion »

:msq:

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

Yeah, sorry I just realized I didn't leave enough to go on. It's MS-II with PWM IAC.

.msq below.

Jim

Oh, also I have a very large plenum volume due to the supercharger, intercooler intake, and air filter housing (Enderlie style) behind the throttle body. I'm not sure if this or the EDIS is causing the delay while cranking. The injectors are right above the ports.

J
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Re: After-start idle control (cold)

Post by turbo conversion »

Need a data log too please.

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

OK this is way rich so I'm going to have to go back through everything to see what changed. But if you look at the first start-up you'll see where the engine fires off and then dies. That's where I need help.

Jim

What I think would help would be if I could set the IAC to let more air in right in the transition from cranking to fast idle. There's just a second or two there where it needs more air to keep running.

J
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Re: After-start idle control (cold)

Post by Matt Cramer »

Your MAP sensor has become disconnected. MAT sensor readings seem to have a similar problem.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

Thanks Matt, that made a huge difference. (Of course. It popped off as I was mounting the box apparently.)

At present I do not have a MAT sensor installed, it's something I plan to work on soon but hasn't been a big priority. The entire inlet system is custom and exposed to view so I have to make it look right, plus it is all under vacuum prior to the blower, vacuum and pressure after it. Then there is the intercooler. Is it better to measure the inlet temp before or after the blower or after the intercooler? Three choices there. An informed opinion here would be very helpful.

But if you will look at the RPM dips in the attached datalog I think it may illustrate what I'm trying to fix. The first big dip is immediately after the engine fires. If I could prevent that one I don't think I would have to deal with the subsequent ones as eventually they settle out.

Jim
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Re: After-start idle control (cold)

Post by turbo conversion »

Do you know that without a completed intake system and a mat sensor every time ambient temperature changes your tune will be off.

You really need to complete your install before you start doing any serious tuning or your tune will not be consistent.

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
kaeman
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Re: After-start idle control (cold)

Post by kaeman »

you want to sense the temp after the intercooler, that will be closest to the temp the air is hitting the heads at. closer to the valve the better for good temp accuracy.
I am having a temp issue, my intake manifold has a location for the temp sensor that always seems to be heat soaked, during cruising on a cool evening my MAT will be 40 degrees warmer than the outside air temp This manifold mounted the MAT sensor in a spot under the throttle body that seems to be out of the air flow.
My old manifold ITB's had the sensor mounted in the velocity stack on cylinder 7 (SBC) Just above the butterfly and it never ran more that 5 degrees warmer than the outside air temp unless I was idling in the staging lanes, then the under hood temps would get into the 150 to 170 ranges, but a soon as I started moving the air temps went back to normal.
64 el camino, 383 SBC, 11.7 to1 CR, accufab tb/rhs intake, 44lb injectors, trick flow heads, xr292r solid roller cam, belt drive camshaft, dry sump oil system, 2400 stall, turbo 350, spooled 9 inch, strange axles, 3.89 gears, dual wideband, full sequential fuel/cop, MS3x using 1.4.1 code.
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Re: After-start idle control (cold)

Post by turbo conversion »

My mat sensor is also mounted post intercooler about 8" before the throttle body.

I know it is easier said than done but don't get in a big hurry to get it running, take your time and complete the install.

I guarantee it will make all the difference, every time you add or take away something the tune will change.

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

I do appreciate the advice. I have thermocouples positioned above and below the intercooler core so the best approach will probably be to figure out a way to use a thermocouple input on the MAT. There really isn't a practical way to install a different type sensor unless I could find a long extended sensor that would fit in a 1/8" NPT hole. To get to the center of the intake and IC core (air/fluid type) it needs to be about 4" long, then I'd need to be able to map it. But, to input the thermocouple I need a thermocouple amp, and that's one of the last bits that need done. The car's been down about 9 years on the powertrain upgrade, and dammit, I'm going to drive it. Running perfect or not.

I get what you are saying about the tune changing though. Still, this isn't my first rodeo so I pretty well know where I stand by not having it hooked up. I remember the first units. Forget the guy's name now but he had a class C van camper and cooked a helluva steak. Some of you will surely know what I'm talking about. Restaurant owner, liked to play with really high voltages. He loved to claim that all you needed was the ignition signal and a vacuum line. And he was right, for a very basic engine you could do that and it'd make that Briggs and Stratton run better than a stock carb. So yeah, it'll run without the MAT, even be driveable but you are right. Better to have it working. And nobody likes to spend longer tuning than they need to. It's a price I'm willing to pay, and I'll get-'er-done in due time but I still need to sort out the details. Ain't like I can just go out and plug it in.

In the meantime, in the midst of all this shake-down it'd be really nice if I could sort out this start-then-die issue. Maybe you guys are right, maybe it's just a matter of getting the mixture and the timing perfect. But here's my question:

If the engine will light off (which it does), shouldn't there be a way to keep it going? Here's the timeline in approximates, the datalog will be considerably more exact.:

Cranking: ~3-5 seconds
Engine fires off: Maybe half a second or less.
Engine dies. Or revs drop so far that it almost dies but then recovers, revs back up, dips back down, and oscillates until it settles out in a fast idle.

Now starting from a cold engine, I don't think the MAT is going to have a tremendous affect on that as everything is at ambient and morning temperatures are running pretty consistent right now, it'll just vary the length of the oscillations or let the engine die. So starting from cold this is something that I should be able to tune out so it repeats fairly closely each morning.

The problem is that I haven't found any way to increase the airflow at that point immediately when the engine lights off. If I could it would keep running and then presumably I could taper it back to a good fast idle. That's the thing I'm asking you guys for help on.

Is it because I'm using a Mustang IAC? Because I do have plans in the works to change over to a GM 4 wire. I have the impression most of you are GM guys so it'd be better to do that anyway, but I have to look at the required changes in the controller and what else that will affect when it is changed, what with the limited number of pins and all.

So with the Ford IAC is there a setting that will increase airflow immediately as the engine lights off? That's where the problem is.

Jim
kaeman
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Re: After-start idle control (cold)

Post by kaeman »

You should be able to go to idle control, and set your idle control to run the current idle air valve, you will choose on/off valve or pmw duty valve, (the stepper is the gm/Subaru) it is one of the regular settings, then set your warmup curve and keep increasing the duty until the engine stays running without your foot. Then you can set the warm up curve to apply enough air to keep the car running.

Good Luck. I just changed over to using idle control feature and understand what you are going through ( my old manifold was a hilborn ITB with no provisions for IAC valve or stepper motor control).....
64 el camino, 383 SBC, 11.7 to1 CR, accufab tb/rhs intake, 44lb injectors, trick flow heads, xr292r solid roller cam, belt drive camshaft, dry sump oil system, 2400 stall, turbo 350, spooled 9 inch, strange axles, 3.89 gears, dual wideband, full sequential fuel/cop, MS3x using 1.4.1 code.
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Re: After-start idle control (cold)

Post by turbo conversion »

I did notice in your log the afr is a consistent 17, what is the reason for that?

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

Not sure, but almost certainly something went off in the MS setup. I don't think it's possible the WB-O2 has failed. Another thing for me to troubleshoot. Using the JimStim it acts a lot like the controller is set up for NB-O2 but I've double checked the setting a couple times. I'm probably missing something. I'm sure it was working before the MS-II failed.

I found an AEM 1/8" MAT sensor and ordered it. Shorter than I'd like, it'll be at the side of the IC instead of out in the middle where the thermocouple is. But it'll be easier to hook up than the thermocouple. If I'm not happy with that, I do have a bag of thermistors and could play around with making up an extended sensor. But maybe the AEM will work OK and if it does I might use another one to replace the thermocouple above the IC as well.

The next thing I think I'll try on this idle problem is to change the setting on the PWM motor to "always on". Maybe that will do some good.

I looked at the wiring for the GM IAC and for some reason on my schematics I have a connection penciled in between S4 and S5. This has to do with the SAW signal and probably physical issues with the main board, but whether the V 3.57 or 2.2 board I couldn't say without looking at the board itself (the 2.2 board is now in one of Dan's cars). So I'll need to see what's going on there before I can go any farther with converting to a 4 wire IAC. But I think I'll take a closer look at the settings for the GM. Seems to me the PWM IAC controls have always been a little wonky. I was one of the first guys to use it and I've never really been happy with the control set. With my first controller on initial start up it always started then died and after that it was great. I never was able to figure out why. But this has not been a problem with Dan's 4 wire.

Jim
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

Right, so it looks like I've got the WB working again by selecting the LC-1 under the AFR Calibrate dialog. Should have been the default but who knows.

Changing Idle Control/Run before start to "ON" seemed to have no effect. Still got that dip immediately after start.

Jim
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

I think I've finally figured out what is going on here with these IAC motors but I could be wrong. Maybe you guys will know.
Let's start with the differences in the way they work. The 4 wire, being a stepper motor is driven to an open position and also has to be driven to a closed position. By contrast the PWM is normally closed, being driven to an open position by the PWM signal.

Now with this understanding, clearly to maintain uninterrupted airflow at all times in the starting process power must be maintained in the PWM IAC. Any interruption for more than a few milliseconds is going to make a change in the flow of idle air and affect the startup. By contrast, once the stepper IAC is in position it will stay there until commanded to move so power or command fluctuations will not affect the idle or startup.

I think there is an interruption of signal to the PWM IAC driver during the startup process. Whether this happens as a result of processor sequencing or power cycling is an unknown at present but for me it matters little. Since the big Mustang IAC is noisy anyway the obvious solution is to convert to GM. It just may take me a little while to get it done.

Jim
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Re: After-start idle control (cold)

Post by turbo conversion »

Try this, turn the key on and let the o2 warm up (come on line) then start the data log.

Once the log is running start the engine and we should be able to see what the afr is doing once it starts.

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

OK, did that.

Jim
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Re: After-start idle control (cold)

Post by turbo conversion »

Not sure why but it looks like it is very rich.

Looking at your msq it seems to me it would be lean not rich.

I don't know what to tell to look for, sorry.

Anyone?

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
Jim_Blackwood
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Re: After-start idle control (cold)

Post by Jim_Blackwood »

Yes, it is rich. I do intend to lean it out.
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