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Unread 03-27-2013, 01:26 AM   #1
Rich Z
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Default Cold start tuning

The moderator at EFILive (joecar) took a look at my tune file, and made some suggestions to me on some tables to take a look at for the rough cold start idle problems I've been having. Seemed like rather minor changes, but they made a world of difference when I loaded the tune that I modified with these changes.



Start up is MUCH better. Doesn't try to stall out on me and run extremely rough like it used to.

The changes made were:
  • B3618 - increased richness of cells below 1600 rpm.
  • A0002 - set percentage to 100%
  • A0008 - increased commanded fuel multiplier at ECT values below 90 C.

OLD:


NEW:


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OLD:


NEW:


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OLD:


NEW:


I think A0008 was probably the table that really made all the difference, as at idle, power enrichment isn't even being triggered. I may take the car out for a spin to see if the changes to B3618 made any difference to throttle response. I'm thinking a bit more fuel might help, since from what I've seen of the logs I've taken, throttle blips tended to make a lean spike and the A/F ratio.
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Unread 04-29-2013, 02:50 PM   #2
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The cold start tuning has been coming along pretty well, so I made up a video showing the progression along the way.



I was feeling pretty good about the progress I made when I started up the car on Saturday morning to go along on a cruise up to Thomasville. In the past when I would start the car up, I would just leave my foot off of the gas pedal completely the entire time till I let the car warm up a bit, but this time I goosed it a little bit and the engine just fell right on it's face when the rpms came back down to what should have been idle speed. So yesterday I set up the laptop for logging and also had video running when I did another cold start to check out this problem. I then took video off of the laptop and merged that video with the audio of the car actually running so I could watch the log data while listening to what the engine is actually doing.



So apparently I still have more work to do in this department concerning the cold start process. The engine is running in open loop at this time, so I need to figure out what tables would be active when the engine is coming down from an abrupt blip to the gas pedal and try to compensate for this transition that allows the rpms to drop down into a stall.
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Unread 04-30-2013, 01:26 AM   #3
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Well, the most obvious event I can see when the engine stalls after the throttle blips is that the throttle blade opening goes from the normal 17.3 percent down to 14.1 percent, so apparently the engine is starving for air flow, which chokes the engine at the lower ECT (engine cooling temp) levels. Once the temps reach a higher level, then that throttle blade choke doesn't affect the engine as drastically.

So, I just need to find the table(s) that will get that throttle blade to come back down and STAY at 17.3 percent after the jabs at the gas pedal.

Sounds simple enough.....
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Unread 04-30-2013, 07:04 PM   #4
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I see a second career as a tuner in your future, Rich! You would probably
be better than 90 per cent of the guys out there........
Andy
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Unread 04-30-2013, 09:12 PM   #5
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Quote:
Originally Posted by navy2kcoupe View Post
I see a second career as a tuner in your future, Rich! You would probably
be better than 90 per cent of the guys out there........
Andy
Thanks, but nah, not my cup of tea. I'm not about to pretend I know what the heck I am doing with this stuff.

Besides, I would need to have access to a dyno, and that certainly isn't going to happen. I only know of a two places with dynos around here and I'm not likely to ever step foot in their shops again.
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Unread 04-30-2013, 09:47 PM   #6
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Crawfordville Timing Association and Dyno Tuning Facility has a nice ring to it!
Just think of the sign........R. Zuchowski, Prop.
Makes you wanna jump right in there don't it!
Andy
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Unread 05-01-2013, 01:44 AM   #7
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Quote:
Originally Posted by navy2kcoupe View Post
Crawfordville Timing Association and Dyno Tuning Facility has a nice ring to it!
Just think of the sign........R. Zuchowski, Prop.
Makes you wanna jump right in there don't it!
Andy


But no, not going to happen. I'm making a modest income off of my websites (well, not THIS one, of course) by doing practically nothing and I can spend my retirement just puttering around with whatever I want to. Why in the world would I want to give that up and then have the pressures and headaches of clients to have to deal with every day? Nope. I had my fill of retail sales with the snake business, so I'm done with that sort of thing.

That's not to say that I wouldn't help out anyone with advice (such that it is) if they need it. But no guarantees would be expressed nor implied other than the 2 cents it might be worth.
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Unread 05-04-2013, 06:23 PM   #8
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Man, that cold start problem is still beating me up. It's really a minor thing, but it just bugs the hell out of me. I've tried everything I can see in the tuning tables and so far nothing has had any effect. It idles real well at 17.3 percent opening of the throttle plate, but when I blip the gas pedal it will then settle at 14.1 percent and the engine acts like it is just starved for air and will either stall out, or oscillate the engine speed slowly for about 19 seconds. Then the throttle plate opens back up to 17.3 percent and the idle stabilizes. Once the engine cooling temps reach around 100 degrees, then it doesn't stall, and seems much happier when the throttle blade wants to be at 14.1 percent.

Well, it's GOT to be SOMETHING! Just damned if I can figure out WHAT.....
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Unread 05-05-2013, 06:07 PM   #9
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Well finally! Something I did made a difference. I made changes to 13 tables that I thought might make a change to that stalling problem. Apparently one or more of them did the trick. Now this really isn't the recommended way to do tuning on a car, especially if you don't know what you are doing (like me) as most people will recommend only making a single change each time and then test the results. But this would take forever with the cold start issues. The iterative process is pretty drawn out because of the time necessary for the engine coolant to cool back down in between runs. So I can only get maybe two runs per day to check out the changes I make.

Anyway, here's where I am now...



The stalling has ceased, probably because the throttle blade doesn't drop down below 16.9 percent. But there is still a loping of the idle after the gas pedal blip. And apparently idle is revving up quite high as the engine warms up right before going into closed loop mode.

Some of the difficulties of this stuff is trying to figure out whether the chicken or the egg came first when looking at the results seen in the log data. You can see the RESULTS, but what is the actual CAUSE of what you see? Is airflow, or the AFR mix causing the timing to change, or visa versa?

So I'm going to make changes to each of those 13 tables mentioned above, in order, to try to get the idle to come back down to a more normal speed. The engine loping is still an issue, but it's not really a killer like the stalling issue was. I may or may not spend time trying to track that down and fix it immediately, as I want to move on to throttle response as soon as I can.

But at least now I feel that I am moving forward...
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Unread 05-08-2013, 02:07 AM   #10
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Well, apparently one or more changes I made to fix the stalling issue at cold start brought back another problem I had earlier. While driving and coming to a stop light, when I would push in the clutch pedal, the engine would rev up to around 1400 to 1500 rpm until coming to a dead stop. Then at a dead stop, the idle would drop down to a more reasonable 1000 rpm. Still a little higher than I would like it to be, but better than 1500 rpm.

The data log shows that timing is apparently causing this to happen by staying too high, as the throttle plate doesn't move during that time to change the air flow. So I went back to tune #20 (I am now on iteration #25) and pulled the two base spark timing tables (B5932 & B5933) from that tune into the new tune.

I'm hoping that this isn't a tradeoff whereby I have to choose between having stalling at cold start when I blip the gas pedal, and having the engine rev up higher than I would like when the transmission is taken out of gear coming to a stop. If they are tied together, I will have to see if I can figure out a compromise point between the two problems.

Other than that, the car ran really well today when I took it out for a drive. Throttle response feels improved from the last time I took it out, which is on the plus side. Cold start is much improved, but that rpm oscillation is still there, as I could hear it when backing out of the garage.
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