VE of 53 to idle at 13.5 AFR - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-29-2015, 01:19 AM   #1
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Default VE of 53 to idle at 13.5 AFR

Attached:
MSQ
MSL

Stock 94
DIY MS2
Map to get around with using PNP tune as a starting point.
- over all, AFRs stay close to 14.7
- No Accell Tip in
- Warm up only

I have a feeling that something is off because VE #'s are around 53 in order to idle at 13.5 AFR. I did find someone in the 40's that asked but the responses said it was pretty normal.
Car is warmed up and most other tables I see have 40's and some 30's for idling.
Idle PW is 1.8 - 1.9

Req fuel is:
Disp: 1839
Cyl: 4
Inj Flow: 254
AFR: 14.7

Trying to make sure I don't have something an issue w/ something fundemental like Req fuel before I start putting a bunch of time into the tuning.

Thanks and please let me know if there is anything else I can provide to help you help me.
Attached Files
File Type: msl 2015-07-25_23.31.43.msl (873.2 KB, 89 views)
File Type: msq HiVENumbers.msq (110.6 KB, 66 views)
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Old 07-29-2015, 05:19 AM   #2
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<p>If you're idling at an AFR you're happy with the actual numbers in the VE table are pretty meaningless. You could make them read 140 at idle and the same AFR if you really wanted to.</p>
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Old 07-29-2015, 05:50 AM   #3
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Double req fuel and half the table and idle in the 25's, or half the req fuel double the table and idle in the 100's. He's right, VE values are useless without context.

Personally, I'd go for the latter as it gives you more fueling resolution on older ms1/2 units.
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Old 07-29-2015, 08:02 AM   #4
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how does halfing one number to double another give you greater resoultion?
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Old 07-29-2015, 08:34 AM   #5
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<p>
Quote:
Originally Posted by Braineack View Post
how does halfing one number to double another give you greater resoultion?
</p><p>&nbsp;</p><p>It doesn't, but it does mean each VE 'point' has less overall effect on the amount of fuel injected, so you gain granularity when tuning.</p><p>&nbsp;</p><p>It's really only useful for tuning idle IMO, particulalry with old/poor/extremely large injectors</p>
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Old 07-29-2015, 10:46 AM   #6
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Huh, borrow a bit from reqfuel, use it in the VE. Makes everything less intuitive, but not a terrible idea. You could theoretically also get a bit or more from the injector table I bet.

To the OP, characterization of the injector at pulse widths where the dead-time is a significant portion of the pulse width is a tedious effort. It gets MUCH harder with old tech injectors. My advice would be to tune VE generally rich down there, and let EGO correction pull fuel.

I think that you will find that ~most~ VE tables are empirically derived look up tables as opposed to a representation of actual system performance.
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Old 07-29-2015, 10:56 AM   #7
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Quote:
Originally Posted by Ted75zcar View Post
Huh, borrow a bit from reqfuel, use it in the VE. Makes everything less intuitive, but not a terrible idea. You could theoretically also get a bit or more from the injector table I bet.

To the OP, characterization of the injector at pulse widths where the dead-time is a significant portion of the pulse width is a tedious effort. It gets MUCH harder with old tech injectors. My advice would be to tune VE generally rich down there, and let EGO correction pull fuel.

I think that you will find that ~most~ VE tables are empirically derived look up tables as opposed to a representation of actual system performance.
Gotcha. Thanks for the tip.

Thanks everyone else as well. I just didn't want to get into tuning and find out I had something in the configuration wrong putting me back to square 1.
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