Delphi 25168491 AFM Question

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ev351
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Delphi 25168491 AFM Question

Post by ev351 »

Hi everyone,

I am preparing to use a larger AFM on a VS V6 SC with stock ECU to allow tuning of more boost. I purchased a Delphi 25168491 AFM off a wrecker in SA on Ebay. I saw that most of them have the (for want of a better term) honeycomb in them. The one I recieved does not.

My question is :

Should the 25168491 have the honeycomb in it? And if it does not, is the AFM still usable or should I return it to them?

Thanks.

Ev.
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The1
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Re: Delphi 25168491 AFM Question

Post by The1 »

25168491 comes with honeycomb from the factory, so id say it was removed.

The ACDelco ones have two versions with and without honeycomb. As detailed in the enhanced general PDF.

ACDelco 15900023 (With Honeycomb) 15900024 (Without)

http://pcmhacking.net/forums/viewtopic.php?f=27&t=2518
ev351
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Re: Delphi 25168491 AFM Question

Post by ev351 »

Thank you for that. Im assuming that it would make a detrimental change to the AFMs measurements and output? .I know many people believe that GM installed this special resctrictor int he form of this honeycomb, but im sure it has some higher purpose like smoothing out turbulence to enable accurate flow measurement :)

Ev.
VX L67 Getrag
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Re: Delphi 25168491 AFM Question

Post by VX L67 Getrag »

I've never found the reason for it, I assumed it was to attempt to collect anything missed by the filter, but we know what to assume spelt backwards means!

In any way you need to re-tune to suit that maf so it won't be detrimental, let's just hope it's 1 of the higher freq reading maf's!
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VL400
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Re: Delphi 25168491 AFM Question

Post by VL400 »

The honeycomb serves a purpose. It’s to straighten out the turbulent air so when measured it is laminar, removing it from a MAF will change the characteristics and possibly make it harder to get a consistant airflow reading.
ev351
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Re: Delphi 25168491 AFM Question

Post by ev351 »

Thanks VL400, Thats what I was looking for. The jokers who sent it can send me another... Not thats its really their fault, they most likely have loads of them and the apprentice packs the ebay orders boxes....

Thanks.
Ev.
ev351
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Re: Delphi 25168491 AFM Question

Post by ev351 »

So I have finally managed to get the hardware side of my 25168491 install complete. After reading through the enhanced mod pdf, I see that fueling needs to be adjusted across the board to allow the new MAF to work. From the description it says that this maf is compatible with the stock frequency range, so does that mean fueling needs to adjusted by a continuous or linear change or do I need to tune for it? If there is a constant value change, can anyone tell me where to find it?

Ev.
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Re: Delphi 25168491 AFM Question

Post by VX L67 Getrag »

Everyone has there own way, some like to scale the MAF & some just change the inj rate so it's close & then use inj mul to trim the rest.

Personally I use the 2nd mentioned option as with scaling MAF it's more fiddly & your changing the style of the curve fitting it to a different setup is was originally intended/tuned for anyway.

SO yeah turn off LTFT & get the inj rate rate so the STFT is as close to zero in most ranges & then start tuning the inj mul table.
ev351
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Re: Delphi 25168491 AFM Question

Post by ev351 »

Ok so there is a fair amount involved, do u think it would be advisable to do the real time programming mod before attempting this? It sounds like I would be in for a lot of EPROM writing and erasing??
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Holden202T
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Re: Delphi 25168491 AFM Question

Post by Holden202T »

the question is how much time do you want to waste ?? :)
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