Cranking FA and VE table quick question

[oakley6575]

Do the cranking FA stage tables reference the cranking VE table? So if I have .62 in the FA table, is it multiplying the cranking VE by that while it cranks? THanks

[oakley6575]

Anyone?

[oakley6575]

bump ttt

[homebuilt]

I was thinking the multiplier is used in conjunction with the OLFA table. I saw your latest updated in another thread but it would be nice to know exactly how these tables work.

I'm working through the exact problem.

[oakley6575]

So I have a pretty good understanding of what all the cranking tables do now. It first starts with all the pulse tables (prime pulse, first pulse mass, second pulse mass). When the key is turned to the run position it will reference the prime pulse which will deliver a pusle through all injectors before cranking starts. After the prime pulse, you will start cranking the engine over where the first pulse mass is delivered after the delay is passed. Then after the second delay, the second pulse mass is delivered. Inbetween and after all the pulses, the injectors will deliver a steady amount of fuel from the numbers in your cranking VE table. So while the cranking ve is being referenced, the FA table is being referenced at the same time. The FA number is mulplied by the cranking ve number to give a steady amount of fuel while cranking. I hope that makes sense

[oakley6575]

So basically the FA is just a multiplyer table that references the cranking ve to answer my original question

[outcastdon]

I believe you're correct.
I have had to raise my stage 1 cranking fuel and lower the VE cranking air to get my 408 to start quickly.
Interested in other opinions.

[homebuilt]

So basically the FA is just a multiplyer table that references the cranking ve to answer my original question

What cranking pulse width did it like after a heat soak? Also what is your pulse width at idle. I would like to see how this percentage difference compares to mine. My idle is ~1.9 -2.0 and the hot cranking PW is 3.7

[oakley6575]

My pulse width at idle is 3.9. But I'm not sure what it is cranking. It is very high with the initial pulse and that is where it fires. I'm not sure the exact pw though

[homebuilt]

Ok, thank you. I start the logging before cranking so I can see what is going on. I was thinking you had to do the same.

Can you post your latest tune?

[oakley6575]

Hells yea. Seems like my truck is liking the current tune. I saw that the first pulse was somewhere around 27ms in my last log. I didn't get to see cranking pulsewidths because it fired so fast. But I think I remember seeing it around 4.7 at operating temp when it wouldnt fire on the first pusle mass. But my idle pulsewidths are defintily around 3.7-4.0 at hot idle.

[oakley6575]

So it likes a bigger shot then I thought. I'm getting the first pulse mass tuned to where it fires first piston up it seems like. I'm so glad I found the fix

[vltrb-0]

So I have a pretty good understanding of what all the cranking tables do now. It first starts with all the pulse tables (prime pulse, first pulse mass, second pulse mass). When the key is turned to the run position it will reference the prime pulse which will deliver a pusle through all injectors before cranking starts. After the prime pulse, you will start cranking the engine over where the first pulse mass is delivered after the delay is passed. Then after the second delay, the second pulse mass is delivered. Inbetween and after all the pulses, the injectors will deliver a steady amount of fuel from the numbers in your cranking VE table. So while the cranking ve is being referenced, the FA table is being referenced at the same time. The FA number is mulplied by the cranking ve number to give a steady amount of fuel while cranking. I hope that makes sense

assuming this is correct info, really good post the standard descriptions are fairly confusing

[BAD LS1]

So it likes a bigger shot then I thought. I'm getting the first pulse mass tuned to where it fires first piston up it seems like. I'm so glad I found the fix

Good deal! Thanks for being another contributing part to helping sort this odd issue out!

[homebuilt]

Thank you for posting your tune. What was the reason you zeroed out the prime pulse? I've wondered if this is only applicable to the original non-return fuel system.

Also was your starting problem happening always when hot or just after a heat-soak? Mine starts ok while hot but cranks for ~6 seconds after a heat soak.

I'm going to grab a few more logs and post them. I want to see what is happening with a cold start, hot start, and an hour of heat soak start.

[oakley6575]

Mine would false start if the ect was anywhere over 100 degrees. The prime pulse was zeroed in the stock file for my year truck. So I just decided to leave it that way and play with the first pulse mass. Post up some logs and a video of it starting and it would help to see which way you should move fuel.

[homebuilt]

Post up some logs and a video of it starting and it would help to see which way you should move fuel.

Sure. He is one for now just in case I might receive some feedback before working on it this weekend.

I have another log where I tried opening the throttle. I thought it was helping so I initially thought it was rich. But after looking at it further I think it was more a function of time and not the throttle position. It cranked for about the same 6 second duration. The start was not with any authority like it is when cold (for me cold is 90F right now).

For reference, I tried some of the math from the Mega-squirt tuning guide. They have a starting point guideline for the PW at 170 (23% the REQ_FUEL). This would put me at 1.4 ms.

One thing that puzzles me is the commanded AFR during cranking. It goes to 16.00. I tried to see how the VCM was arriving at that value from the calibration and I couldn't get anything in the ballpark. The OLFA value is 1.13 - 1.14 and the multiplier is between 0.85 and 1.15. Perhaps the commanded equivalence ratio is not a simple product of the "Multiplier" and the OLFA???

[oakley6575]

Sure. He is one for now just in case I might receive some feedback before working on it this weekend.

I have another log where I tried opening the throttle. I thought it was helping so I initially thought it was rich. But after looking at it further I think it was more a function of time and not the throttle position. It cranked for about the same 6 second duration. The start was not with any authority like it is when cold (for me cold is 90F right now).

For reference, I tried some of the math from the Mega-squirt tuning guide. They have a starting point guideline for the PW at 170 (23% the REQ_FUEL). This would put me at 1.4 ms.

One thing that puzzles me is the commanded AFR during cranking. It goes to 16.00. I tried to see how the VCM was arriving at that value from the calibration and I couldn't get anything in the ballpark. The OLFA value is 1.13 - 1.14 and the multiplier is between 0.85 and 1.15. Perhaps the commanded equivalence ratio is not a simple product of the "Multiplier" and the OLFA???

What mods are you working with. Looks like your cranking tables are stock for an F body. You should try my cranking settings and see how the car reacts. Or multiply the cranking fuel tables by three and see what that does.

[homebuilt]

I tried a hot start with the first and second pulse doubled above 90 degrees. It fired a little right away but then continued to crank for a while before starting. You can't see it in the video but there was a puff of black smoke.

Here are the links: http://www.youtube.com/watch?v=yu_Ua...e_gdata_player

http://www.youtube.com/watch?v=_3wPL...e_gdata_player

I'm not sure how to proceed. Maybe take the pulse tables back and try reducing the cranking multipliers by 10% in the warm regions?

[oakley6575]

I tried a hot start with the first and second pulse doubled above 90 degrees. It fired a little right away but then continued to crank for a while before starting. You can't see it in the video but there was a puff of black smoke.

Here are the links: http://www.youtube.com/watch?v=yu_Ua...e_gdata_player

http://www.youtube.com/watch?v=_3wPL...e_gdata_player

I'm not sure how to proceed. Maybe take the pulse tables back and try reducing the cranking multipliers by 10% in the warm regions?

Yea if you think it is rich then back the pulses down. Did try setting your cranking tables up like the trucks have them. Just with a first pulse instead of the prime, first, and second pulses? Just something to try. But I can take a vid of my truck starting lean and rich so you can see how mine reacts. I don't know if that would help you or not.