Commanded Fuel when Cranking

[gpr]

Since the temps are getting colder my car isn't starting up as well now that it is running on e85. It seems as if it needs more fuel when cranking, so I have increased B3604 by about 20 percent. However it seems to make little to no difference. I'm confused on what this table is actually displaying? What are the values in this table?

Mine goes from a vaule down at 1.2 at temps of -40 up to 25. But what are these values exactly? is it eq ratio? the description doesn't really say other than it is the commanded fuel. Is it grams/sec or volume of fuel? is it a/f ratio?????

Also I'm thinking to help cold starts to increase the initial prime when the key is turned on?

[joecar]

Can you post a pic of that table.

[gpr]

14307

here is the table i'm talking about. Was hoping increasing it would help with my e85 cold starts.

[joecar]

If you look at the upper right of the 3D view you will see that the units are AFR...

( the contents of that table don't look right )

[gpr]

If that is afr, how could it command those values? If i look at the stock tune they are very close and very similar values.

What is the best table to add fuel during cold starts? I'm also going to go add some more timing as well when cold.

[DrkPhx]

That table is very sensitive to adjustments and hard to pinpoint when it transitions to the OL commanded fuel table so tread carefully. I wouldn't do wholesale adjustments based on a %, but target a specific AFR value. If you look at a stock table you can see where the first couple of cranks per 90 degree (columns) are typically leaner, then richen upout for each crank after that. As Joecar mentions above, those values do look odd. You also have to consider the Afterstart Enrichment tables as well which are displayed in EQ ratio. Does the engine crank, but doesn't catch to hold a steady idle? If so, look at OL commanded table and Afterstart tables. Also note, E85 is not really E85 in Winter time because gas stations switch to a lower enthanol content for more gas to provide better cold weather starts, so you may have to actually lean it out. you can also use the DVT controls in the scan tool to play around with commanded AFR to see what the engine actually needs.

[gpr]

No the engine will crank and crank and crank and not fire up. So i will shut it off and turn it on and the second time it cranks a little while then finally fires up. Once it is running it is fine, but for some reason when it is cold it does not want to fire off right away. After it is started i noticed it is a little leaner than it should be, thus why I want to richen it up while cranking, then a bit more when ect are low.

[slows10]

Did you post the tune and a log showing the problem? I did not see one. Is this O/S 12212156?? What are you tuning? What are your mods? B3201 does not look close to what it should be, if I /we think you may be tuning, if we knew what you were tuning. What is B3202,3203,3204,3205,3623 set at. What does the wideband say? I dont understand how others can tell you what to adjust, when they arent sure what your running for mods or stock. Especially when you dont even list engine size? Whats wrong with 1.2 at -40 ? Is the table B3201 stock?? Can you post up your current tune for a more realistic approach at helping you fix your problem?

[gpr]

Here is my tune. it is a 2002 camaro and it has headers, full exhaust. There is also a cam installed in it, but I don't know the specs as it was there when i bought it. I put a racetronix wire harness and fuel pump in, then switched it over to e85. runs great the only issue is the cold starting. As the first try it seems like it will crank forever and not fire. Try it a second time and it will fire up.

[gpr]

BTW, i have changed the commanded fuel when cranking table. After realizing it is showing afr, but multiplying it by 20% this actually leaned out the table. So i put it to stock then increased the afr in the ranges i am having issues. Also i changed a lot of the starting tables back to stock that i had changed trying to help the starting issues. I will post new tune when i get a chance.

Anyway after making these changes I tried it again. Does essentially the same thing. The car cranks and cranks the first time and never fires. Let off and hit it again and it fires immediately. I have no idea why it is doing this, and it is only when the engine is cold.... I'm not even power cycling the key, I simply let off from cranking wait one second then try again and it fires immediately... I'm wondering if it isn't a tune issue but something else?

[joecar]

29° spark timing at high load seems too much (but I see you're running E85 even tho you have not edited B3601)... do you see/hear any spark knock...?

[O1Z06]

Not too long ago I got a new engine up and running and the startup is a pain in the buns. Here is what I did. First, that cranking EQ table does some very strange things based on other linked table influences. I said the heck with logging it and used IBPW instead. This gives a much better representation of what is going on. Also, logging with the V2 instead of the V7.5 scan during startup where everything happens quickly will help insure you don't drop or loose frames. Are you logging WB and is it on during cranking or is it switched of ignition which cycles when you crank?

Regarding which tables to work, I would download a LQ9 LS1B truck .tun from the repository. I used this as a reference and it got me close but because I have a big cam and bigger engine, I had to keep adding some here and there. Set the cranking EQ table, cranking VE, initial fuel, first fuel pulse and after start to LQ9 tune. The cranking VE made the biggest difference. With my setup, I have a A1000 FPR and twin intank pumps. So there are no check valves and the system does not have full pressure until about a 1/2 second after you turn the key. Do you still have a check valve? The reason I ask is because the first fuel pulse B3204 has a timer then dumps an appropriate mass unit of fuel. If you watch IBPW you will see a spike where this happens. You have it at 3 seconds. Mine is at 14 ref pulses. Also, I don't use the second pulse, just added first and second into the first pulse. I don't even use the initial prime, just dump it all in the first pulse. The initial may help you though as it would dump fuel before you crank, allowed more time for the stingy alcohol to evaporate.

When the temps get cold, alcohol doesn't have good volatility like gasoline does. The refinery tries to aid this by changing the blend slightly during winter. So with the LQ9 tune being for a larger engine, it may be all you need. But, if your still having issues, you might be able to increase the injection timing or EOIT. Taking out %20 from B3702 might help and let the fuel evaporate a bit longer, I don't know how much of an effect this will be on start up but I know it does make a difference once running especially with my cam. Hope this helps.

[gpr]

joecar,
The only knock issues i have had was with burst knock when i would stab the throttle. I zero'd out the burst knock tables and haven't had an issue. I believe I changed the high spark table based on someones reference on here when they were tuning e85. I also didn't change b3601 because to tune for the e85 I did it the lazy way, but changing the fuel injector flow table instead. I tried the correct method of changing b3601 and all the tables to run e85 and it was a tuning nightmare starting from scratch. Also I live at high elevation so might also be why i get away with more timing.

I think i'm gonna go change b5910 Spark ECT Table, so it adds a few more degree's of timing when ect are low.

01Z06, thank you for the help. I will go look at doing some of that stuff. I was thinking that changine the VE while cranking table is where i need to look to add more fuel when starting. I'm wondering if this second fuel prime isn't what is causing me confusion.

My issues is i turn the key on and let it sit till i hear the fuel pump turn off, and know the system is up to pressure. Then I will crank and crank on it, and the engine will not start. I won't turn the key off and let it sit a second or two then try cranking again, and it will fire up almost immediately! So there must be some sort of fuel prime happening on that second crank that is why it is firing.

I will go add more fuel to the first initial prime and hope that helps. Also would it be good to shorten the time from 3 seconds down to 1? that way it is giving it more fuel immediately?

[gpr]

01Z06,

I think using the lq9 files should help. Just comparing them the commanded fuel when cranking table seems to make much more since. Also the other tables are a tad richer. I have copied the tables over and will give this a try tonight.

Thank you both for the help, I will let you know if it helped.

[O1Z06]

Increase the pulse delay to 14. We're talking milli seconds here. The difference between 3 and 1 is negligible. Make sure to take a log of startup with the V2 BBX and log IBPW PID.

[gpr]

I'm confused, if it is milliseconds why would going from 3 to 14 make much of a difference? Less time for the alcohol to evaporate????

thanks again for the help.

[joecar]

More time for the fuel puddle to form on the port wall (so the dynamic wall wetting model could get going)...?

[O1Z06]

Using 150 rpm cranking, 1 ref pulse is .016 seconds, 3 ref pulses is .05 seconds, 14 ref pulses is .233 seconds and so on. During the batch fire pulse, the PCM looks at the mass of fuel requested and injector flow. After this pulse, it goes back to crank ve and cmd afr. You have scaled injectors? You would have to scale ve and pulse mass as well.

[GMCtrk]

Any update on this? I'm having this same issue. Perfect starts on gasoline, but cold starts on E85 takes 2 cranks and sometimes it struggles to idle for a couple seconds after startup.

[joecar]

Any update on this? I'm having this same issue. Perfect starts on gasoline, but cold starts on E85 takes 2 cranks and sometimes it struggles to idle for a couple seconds after startup.What is your B3601 set to...?

[gpr]

Doing the recommendations from 01z06 did help improve cold starting with e85. it isn't perfect but is better. I needed more time to get it perfect, but have torn the car apart to build a turbo kit.

From what i have seen running on e85 it requires a lot of fuel when cold.

[GMCtrk]

What is your B3601 set to...?

10.09, commanded AFR part throttle is 9.76. Running OLSD in COS3.

I've tried lowering cranking AFR with no effect. Put in the cranking VE table and commanded fuel on startup from a flex fuel tahoe with no difference.

I cannot log AFR with my wideband on startup because the NGK AFX takes 20 seconds to read after starup

[joecar]

I thought E85 had a stoich AFR closer to 9.6...

[GMCtrk]

I thought E85 had a stoich AFR closer to 9.6...

Stoich is 9.765 for true E85. But the stuff in the pump right now is winter blend, E70. So stoich is probably closer to 10.2. I don't see that making the difference here. 2 cranks tells me it needs more fuel dumped in, but I don't know how to get it in there in the tune.

[GMCtrk]

Anyone?

[joecar]

Post your tune file.

[DrkPhx]

Cold start E85 tuning is hard to nail down. Have you tested the fuel to see what the actual ethanol content is? You would be surprised how much it varies. Something to consider is to increase the stoich to help compensate for the winter blend which has more gasoline and less ethanol. When I ran E85 I settled on 10.76 stoich for the "off months". It took a lot of incremental experimenting using the DVT controls to settle on this value. I'm not saying that value will work for your set up; but you should use that feature to help pin point the required fueling. Have you logged commanded AFR in the scan tool to confirm what the cold start AFR is? If it's richer than main commanded table; the adder/multiplier tables are probably adding fuel. Look at the Afterstart ECT Enrichment table which adds fuel on startup based on ECT. It's in EQ ratio (not lambda).

[GMCtrk]

Cold start E85 tuning is hard to nail down. Have you tested the fuel to see what the actual ethanol content is? You would be surprised how much it varies. Something to consider is to increase the stoich to help compensate for the winter blend which has more gasoline and less ethanol. When I ran E85 I settled on 10.76 stoich for the "off months". It took a lot of incremental experimenting using the DVT controls to settle on this value. I'm not saying that value will work for your set up; but you should use that feature to help pin point the required fueling. Have you logged commanded AFR in the scan tool to confirm what the cold start AFR is? If it's richer than main commanded table; the adder/multiplier tables are probably adding fuel. Look at the Afterstart ECT Enrichment table which adds fuel on startup based on ECT. It's in EQ ratio (not lambda).

Cold start AFR is less than 6, that's all the gauge will read down to, maybe I can reconfigure it

The only issue I have is cranking basically. Once the engine fires its smooth sailing. The blend right now has to be e70 minimum by law. But you are right, without testing I have no way of knowing the AFR. What I do know is that my ngk wideband reads 14.57 on the gauge when lambda = 1. And my AFR sits around that mark cruising and idling which means I'm near stoich. AFR and ethanol % is pretty irrelevant to me then.

As far as cold start goes, it 2 cranks which would indicate more fuel is needed. Maybe I need to adjust that ECG table you mentioned. And it's also worth adding, cold temps aren't playing a role here down south. It's usually 65-70 degrees in my garage.

[DrkPhx]

That's rich for E70. Adjust the Afterstart table in increments either way to see what the engine responds to. I would also try adding some timing on start up as well.

[GMCtrk]

Solved the cold start issue...had to add a 0.2 oz initial fuel prime. Starts instantly like on gasoline. My only problem now is that anytime I turn the key on fuel is being squirted into the cylinder. If I don't start the engine I don't really want ethanol leaking down into my oil. I wonder if adding to the initial sequential fuel pulse would also solve the issue, without having fuel dumped with the key to the on position.

[joecar]

Which table id...?

[GMCtrk]

B3204