With fuel injection you can pick an amount of timing to add or subtract for various engine coolant temps. This is not a question about what initial timing on a conventional distributor gives the best pderformance over all. Simply what timing values do you think work best to get the slant started? Think of the various ways you have set the initial advance, and how it started relative to each one. And then consider how engine coolant temperature affects this. I can set this to be a different advance value for the various temp ranges in warm up.

Do you think the slant starts better when dead cold at TDC, 2.5 BTDC, 10BTDC. I can actually advance it as much as 30 degrees BTDC if I want. What would you do here?

The baseline start up timing is set at 6 degrees. The default table, which would be for a SBC adds 20 degrees to the base start up timing at 20 degrees ECT, which would be dead cold on a winter day. It curves down to 0 degrees start up timing added at 123 dgrees ECT. It then curves on further down as the ECT goes up to where 10 degrees are taken out of the start up timing at 185 degrees ECT. It seems as if that is a bit too much start up timing to take out of what would be a low compression engine by SBC race car standards.

Thanks for thinking about this. Any advice based on real experience, or even theories you have read are valuable here. Hopefully we wil all learn from any discussion that comes out of this question.
Sam

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I simply had mine locked at 10 degrees BTDC while cranking. Then again, I hadn't gotten the cold start settings dialed in before the latest round of upgrades anyway.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

I don't know how far South Oxford is. I know Atlanta can get some pretty fierce ice storms. Maybe your weather is more moderate than ours. How does your slant start? Do you have to baby it and tease it to get it going? I know MS has a clear flood mode which makes things less tense.

Sam

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Too much or too little advance adversely affects cold starting. Too little (zero or ATDC) and there's just not enough bang to get the engine to keep running after initial fire. Too much, and the cylinder explosions will fight against the starter. In extreme cases of kickback, starter parts can actually be broken. From everything I've experienced and read, something between 0 and perhaps 5° BTDC is probably ideal for cold-engine cranking and startup, with more advance added immediately once the engine actually starts. Chrysler themselves did a great deal of cold-engine start tests in the '60s, and one of the things they found was that when the base timing was advanced much beyond the factory spec, engines tended to get consistently harder to start and keep running from cold.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It's rare for the temperature here to drop below 30. However, I only had it running for a few months before I tore it apart to put in some non-EFI related upgrades and never did get the cold start settings working well. However, it seems they had almost as much to do with my inadequate charging system as the fuel settings - I had a 45 amp alternator with enough things to draw lots of current, and I couldn't keep the battery charged.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

So Dan, It seems as if I most likely have way too much timing in at cold startup. And, since this is not a high compression race SBC, maybe I should go to 5-6 degrees total for start up even when it is warm. Would you agree with that? As it stands now, it is trying to start cold with about 25 degrees of advance. I can phase out the after start advance at any rate I want, to any value I want. This is exciting information. maybe I can get this thing to fire off just like an OEM EFI car.


Sam

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Eek! Yeah, I would pull 20° of startup advance out of it all at once. I can only imagine your cold lightoff getting significantly better, not worse. Remember, stock carbureted slant-6s with everything adjusted to spec tend to light off immediately, hot or cold, and their cranking-and-lightoff timing is somewhere in the 0° to 5° BTDC range. (we're ignoring extended hot crank due to carburetor percolation, extended cold crank due to choke maladjustment, and we're entirely disregarding how they run immediately after lightoff, because all of this is largely down to carburetion factors and you haven't got a carburetor).

Do keep in mind that a stock slant gets a large dose of advance added in as soon as the engine lights off from cold: it's on the fast idle cam, so there's a significant amount of mechanical and vacuum advance. It's not uncommon to see the timing jump to 25° within a second or so of initial cold lightoff. Does your ECU have configurable advance during _cranking_, or maybe a crank-retard function, or some other way of achieving 3 to 5 degrees' advance during cranking and keeping ~20 degrees or so for cold idle?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yes, and thank you very much. I can set the cold idle speed at 1200 and have that cell read 15 degrees. Or, I can set after start advance to be higher when it is cold. I will go fool with this right now. No wonder it didn;t start reliably.

Sam

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I agree that cold engne needed bit of help to stay alive by higher idle rpm than usual for first several seconds (even longer if temp is even colder). On mine, it will die if I bump off choke too soon because I set up the fast idle bit lower since I don't like factory recommandation for 1700rpm so I set mine 1600. The first step on fast idle is around 2200rpm, slowest rpm is 1600 on final step. 2.2L BTW.

Oh yes, 2.2L does light off instantly after I poke the gas pedal and turn key.
chug-chug-vroom!

Cheers, Wizard

Dan you are a genius! I set the baseline cranking timing at 6 degrees, and removed all additional timing coefficients during cranking for all temps. It fired off after 4 fast spins of the mini starter. I raised the fuel a bit, and it fired off at 3 fast spins of the mini starter. There is a timing map that manages after-start timing. I need to make sure this is not added to cranking before I add more timing there. Hopefully Accel will answer their phone one of these days. The manual is not clear on this. No surprise there.

This is good enough for now. I feel like I can trust this car to drive anywhere once again. Thank you, thank you, thank you. I think eventually, between the two of us, we could serve as a tech line for Accel.

Sam

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The only thing that kinda sticks out at me here is...why do you need such a fast idle on cold startup? The purpose of fast idle on a wet-manifold system is to get enough airflow through the manifold to sweep some of the fuel that's condensed on all that cold metal back into the intake charge so there's something to burn in the cylinders. With a carburetor, the fast idle has to be really fast, so there's enough of a vacuum signal to yank fuel from all the discharges with the choke closed. With throttle body injection, you don't need nearly as fast of a cold idle, because fuel flow into the manifold is controllable independently of system airflow. With port fuel injection, you've got a dry-manifold system, so while a slightly higher idle speed is beneficial for the first short while, you shouldn't need a very high or long-duration fast idle. I don't know how fine the adjustability is on your system, but offhand, I can't imagine a need to go much above 1000 rpm, and even that for only 5 to 10 seconds or so, depending on how cold it is.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Tremendous! I think I would keep an ear/eye on it over the next few cold starts and see how it behaves over time before making the next round of adjustments.
Glad to help out! My own EFI tinkering (on the truck) seems to have been all for the good — cold startup and driveoff is noticeably better — though I still haven't been in for an emission test yet. Before I do that, I want to wrap both branches of the headpipe with Thermo-Tec wrap.
From everything you've reported, they certainly haven't got a good one themselves!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The target idle speed is absolutely adjustable by a number of temp break points. It is easy to do. I can refine this as I get more comfortable with it. I think I set it that high simply becasue it didn;t run very well at first, and I was just trying to be sure it did not die. I will try setting both the cold idle, and warm idles a little lower. The warm idle is set at 750 right now. I noticed that my Toyota idles at 650, as does my buddies Nissan minivan.

One thing I have learned is that if I set the idle area timing lower, the idle air control opens more to compensate, which, for what it is worth, should burn a little cleaner. At idle the timing bounces around to keep the idle steady, in addition to the idle air solenoid.

Maybe I will lower the cold idle down to 1100 PRM and drive it a bit like that. It might save a little gas. I really appreciate your suggestions. It is your educated touch that takes my raw, but creative confidence to a new level of refinement.

The next step is to figure out how this manifold temp vrs engine coolant temp is tuned, so I can even out this change in AF ratiio that happens when the car is driven for a longer period of time. I am going to start recording both the inatke port temp and ECT temp and compare those at various levels and see how they are effecting AF ratio. There is a VE coefficient that can be added to the fueling strategy that utilizes this relationship on a temp based map. I just don;t know how it effects things yet. I will start collecting my own data, since Accel hasn;t been much help.

Sam

Sam

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