Author Topic: AHU vs. AFN  (Read 4199 times)

March 09, 2020, 06:42:02 pm

Achilles3588

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AHU vs. AFN
« on: March 09, 2020, 06:42:02 pm »
I just took receipt of an m-TDI from what I understood to be a reputable builder based here in the US.
This is for a swap of a 1.6L JX to a 1.9L TDI, intended as an AHU. For a '91 Syncro Doka.
With the understanding that the stock JX turbo would work (even w/o an intercooler) with the AHU.
However what was delivered was an AFN block.
Now, I am being reassured "every[t]hing is the same. no difference what ever between a afn longblock and 1z/ahu. only the turbo is different and the nozzle in the injectors. the head is identical, block, crank, pistons all the same"
This does not disturb me greatly, as again I'm being told "afn=1z=ahu, same thing but higher hp rating. the afn came with a vnt turbo"
The only worry I have is with the turbo. I refurbished (new cartridge) my original JX turbo.

Is the VNT turbo required for the AFN? Or is this simply a nice to have for optimal HP, the original will work 'just fine'?
Does the AFN require an intercooler (had not planned one since the original configuration had none)? Or again, nice to have for performance reasons?


'91 1.9L TDI 'AFN' Syncro Doka

Reply #1March 09, 2020, 07:00:16 pm

libbydiesel

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Re: AHU vs. AFN
« Reply #1 on: March 09, 2020, 07:00:16 pm »
What you have been told is accurate.  The AHU and AFN long block are interchangeable. 

If you are running with a mechanical pump, the JX turbo will work fine.  Similarly, no an intercooler is not required.  If running the full electronic engine management you might toss a code and go into limp mode with the turbo change or without the intercooler, but with a mechanical pump it is a non-issue.

Reply #2March 09, 2020, 09:04:58 pm

Achilles3588

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Re: AHU vs. AFN
« Reply #2 on: March 09, 2020, 09:04:58 pm »
 :D
'91 1.9L TDI 'AFN' Syncro Doka

Reply #3March 10, 2020, 12:51:57 am

fatmobile

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Re: AHU vs. AFN
« Reply #3 on: March 10, 2020, 12:51:57 am »
    It's a stock VW 1.6 TD turbo?
 Something like a k24 or garret?
 
 Keep the VNT turbo.
 You might want to upgrade later.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #4March 10, 2020, 01:58:55 am

libbydiesel

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Re: AHU vs. AFN
« Reply #4 on: March 10, 2020, 01:58:55 am »
The JX has the K14 stock.  It's a decent match to the AHU in a Vanagon.  The VNT17 gives better performance (as does the intercooler), but the wastegated turbo is simpler.