Math for the VE multiplier

[Beer99C5]

Howard got me set up w/ my head cam, and now I want to play more with COS5.

How do I estimate what I need for the VE multiplier if I want say 11.8 for my AFR above 3000 RPM...

Basically I start lean (so I want to add some fuel down low 3000's), and as it goes to 6000 RPM it goes rich to 10's and 11's for AFR (so I want to lean it out upper RPM).

I want to make the VE multipliers to try and manage this w/ the nitrous toggle is enabled.

Whats the math to do this? Guessing I use MAF Grams/Sec as a starting point, then refer to the appropiate VE cells? and do what next?

http://www.retrorelics.net/jim/Boards/EFILive/COSN2OMonVEmult.jpg

[Doc]

You have to have your commanded vs. actual AFR's very tight to begin with. Assuming you do, if you have an area that when on the motor alone you are commanding say 12.5 AFR, (1.17 EQ Ratio) and you want to be 11.8 AFR (1.239 EQ Ratio) then your difference would be .7 AFR (.069 EQR).

Notice how the table units are in "FACTOR", this is how the pcm crunches the numbers, as you should also. AFR is logrithmic and the pcm cannot do the higher math to come up with the new enrichment number. You would need a multiplier of 1.069 in the rpm cell(s) that you want the enrichment to happen in.

Remember, EFI Live provides the AFR units just for our motorhead brains as a crutch. It's best to start walking like an Egyptian or pcm in this commanded fueling business.

[Beer99C5]

You have to have your commanded vs. actual AFR's very tight to begin with. Assuming you do, if you have an area that when on the motor alone you are commanding say 12.5 AFR, (1.17 EQ Ratio) and you want to be 11.8 AFR (1.239 EQ Ratio) then your difference would be .7 AFR (.069 EQR).

Assuming the case above, Its commanding 12.5 and N/A I get 12.5 +/- and I want 11.8 @ 3000 RPM instaed of the 12.5 when spraying...I enter 1.069 on the 3000 RPM entry?

As it goes Lean to rich, I should end up say at .931 if I am 11.1 AFR @ 6000when spraying (to get 11.8 ) ?

[joecar]

Question: can it be calculated like this instead: 1.239/1.17 = 1.059...?

(i.e. treated purely as an EQ multiplier without thinking of AFR difference)

[Doc]

Assuming the case above, Its commanding 12.5 and N/A I get 12.5 +/- and I want 11.8 @ 3000 RPM instaed of the 12.5 when spraying...I enter 1.069 on the 3000 RPM entry?

Yep


As it goes Lean to rich, I should end up say at .931 if I am 11.1 AFR @ 6000when spraying (to get 11.8 ) ?

As it goes Lean to rich, -ummh???!!!???

[Beer99C5]

Yep



As it goes Lean to rich, -ummh???!!!???

Here is a screen (this is a 50 Dry @ 2800 and a 50 wet @ 4000), this shows the fuel pressure drop, when the wet kicks on @ 4000 RPM.
With the drop you can see the AFR rise until the pump recovers.

http://www.retrorelics.net/jim/Boards/EFILive/HCdrywetshot.jpg

I want to counter the AFR Spike, so I intend to use the multiplier to try and get a steady 11.8 or so during the entire Nitrous run. Near the end of the run you can see its 10.00's, I want to raise that so I would be looking at .9XX or so for the multipler there?

[Redline Motorsports]

Beer,

I don't think the PCM can respond fast enough to get rid of one spike. Nor is it detrimental to the motor. You need to look at average trends for your changes. What size and combination are you going to stick with? 50/50?

I would make a quick spreadsheet noting actual AFR vs requested AFR (on spray) and calculate of the percentage of difference. This then can be converted to EQ ratio and used in that table.

[Beer99C5]

OK just to make sure I understand...

http://www.retrorelics.net/jim/Boards/EFILive/1COSSpreadsheet1.jpg

Based on Dry Log...
http://www.retrorelics.net/jim/Boards/EFILive/1COSAFRdry.jpg

Gives me something like this

http://www.retrorelics.net/jim/Boards/EFILive/1COSVEmulti.jpg

For KR combined shot...

http://www.retrorelics.net/jim/Boards/EFILive/1COSKRcombined.jpg

http://www.retrorelics.net/jim/Boards/EFILive/1COSTiming.jpg

[Doc]

Are you not running a upgraded pump and wiring kit? I can't remember.

[Beer99C5]

Are you not running a upgraded pump and wiring kit? I can't remember.

Yes have the Racetronix pump and hotwire kit...

Seems to have been a waste of time and money, shoulda just done a BAP with the stocker.

[Doc]

Have you tried logging batt V / monitor Alt output? I found that my stock alt couldn't keep up with running the fans more, bottle heater, LC-1, FP sensor, Big Bon Jovi stereo, etc. Granted the Vette has a larger alt than the Fbody but, still before you condem the pump you have to ask yourself is it getting enough juice?

[Beer99C5]

Have you tried logging batt V / monitor Alt output? I found that my stock alt couldn't keep up with running the fans more, bottle heater, LC-1, FP sensor, Big Bon Jovi stereo, etc. Granted the Vette has a larger alt than the Fbody but, still before you condem the pump you have to ask yourself is it getting enough juice?

LOL Bon Jovi? You from Jersey? What Exit :D

I will check it out and log voltages, but back on topic...is the math on track that I got going?

[Doc]

I think you are on track for with the math but, I wouldn't want you trying to enrich to overcome a possible physical/electrical weakness of your fuel system.

[Beer99C5]

I think you are on track for with the math but, I wouldn't want you trying to enrich to overcome a possible physical/electrical weakness of your fuel system.

I am actually trying to lean out the 10.9 to get mid 11's-11.8 at the tail end of the dry nitrous runs. The richening is in the beginning and is less than a second.