AHU to AFN

**spud28** · 02-05-2009,05:41 PM

Hello people I'm new to this site, hopefully some one out there can help me.

I am have great difficulty finding out about the compatibility between AFN and AHU engine codes. I have an Audi A4 tdi with a 110 AFN engine(broken) and when I ordered a replacement from a breakers they delivered a 90 AHU engine,

They say that the engines are the same and that all I have to do is change over my existing turbo and exhaust manifold and the AHU becomes an AFN.

Is this true? I don't wount to go to the trouble and expense of changing it over to find it's not true but I can't seem to find anything definite,

Any answers or suggestions would be much appreciated,

Thanks, macspud28

HomerSimpson · 03-05-2009,02:59 PM

Hi Spud,
I don`t think it is quite as easy as that!! I think that somebody is trying to pull the wool over your eyes. I am led to belive from my brother in law who is a mechanic, that you would also need to change the ecu as well. Sorry to be the bearer of bad news, I only know that because I too had to change my engine and had to get an AFN engine. One word of warning though when you are hunting for your engine, always ask what you are getting for your money. I made the mistake when I bought mine, I asked for a complete engine. What I got was just the engine block, no sensors, flywheel, turbo, etc. When I complained I was told I should have asked for a Full engine. Yes I know what you are thinking, Whats the difference? So as I say just check before you buy as it could cost you money having to send it back!
Hope this is of some help.

**Crasher** · 03-05-2009,03:11 PM

The AHU and AFN base units (head and block) are identical, if you were to order a genuine VAG exchange base unit they are the same part number. You will also need to swap over the injectors

**spud28** · 03-05-2009,04:22 PM

Originally Posted by HomerSimpson

Hi Spud,
I don`t think it is quite as easy as that!! I think that somebody is trying to pull the wool over your eyes. I am led to belive from my brother in law who is a mechanic, that you would also need to change the ecu as well. Sorry to be the bearer of bad news, I only know that because I too had to change my engine and had to get an AFN engine. One word of warning though when you are hunting for your engine, always ask what you are getting for your money. I made the mistake when I bought mine, I asked for a complete engine. What I got was just the engine block, no sensors, flywheel, turbo, etc. When I complained I was told I should have asked for a Full engine. Yes I know what you are thinking, Whats the difference? So as I say just check before you buy as it could cost you money having to send it back!
Hope this is of some help.

Hello Homer,

Thanks for the reply, that is what I've been worried about. I've already got the engine and unfortunately it's been lying for 6 weeks at the garage waiting to be fitted as they've been very busy. It looks exactly the same on the out side so they hadn't noticed until this week when they when to fit it and happened to mention it to me, I told them to stop while I checked things out. The brokers are saying that they told me it was an AHU at the time and that anyway it's just those two things to swap. That's not true but they're not budging.

I need to get as much amunition as possible if I'm to get any joy out of them, as they've already said that I'll have to take them to court. So I need a definitive answer to see which will be the easiest coarse for satisfaction.

It'll cost £250 minimum extra with the return dilivery costs + 25%

My lucks not in, it'll be ages until I get another slot at the garage too. Thems the knocks eh, when your lucks not in your lucks not in. Getting fit with all the walking ;-)

**spud28** · 03-05-2009,04:40 PM

Originally Posted by Crasher

The AHU and AFN base units (head and block) are identical, if you were to order a genuine VAG exchange base unit they are the same part number. You will also need to swap over the injectors

Hello Crusher,

What, is this some good news? It's a bit like a rollercoaster ride up and down.

That is good news. Can you tell me where I can get or see the specifications, I had no luck with any of the Audi dealers I phoned on friday.

Cheers, Iain (spud28)

**kenney** · 03-05-2009,05:17 PM

AHU 1.9 ltr.Output kW at rpm 66/4000. Torque Nm at rpm 202/1900
AFN 1.9 ltr Output kw at rpm 81/4150. Torgue Nm at rpm 235/1900
Compression ratio on both engines 19.5

**Crasher** · 03-05-2009,05:30 PM

You don’t need any specifications and if you took them to court you should lose as you would be in the wrong. Every single part inside the engine including the block and the head is the same for an AHU and an AFN, the difference in power is by the turbo and the injectors as well as by ECU mapping. In fact it could be argued that an AHU is a better bet as it has been subjected to less stress during its service life than an AFN.

**spud28** · 03-05-2009,05:32 PM

Thanks Kenny, it was more the actual phyical differences I was asking about.

**ini** · 03-05-2009,05:41 PM

As Crasher said, the bare block and head are identical, same mechanicals, same valve sizes, same everything.

If the 90bhp AHU replacement engine is used and complete with ancillaries, you will obviously want to use your original AFN injectors, boost/egr system, turbo etc etc.

**spud28** · 03-05-2009,05:46 PM

Thanks Crasher,

That's what I wanted to hear. I wouldn't want to take anyone to court, What I meant wasn't true was that they had told me on the phone. I didn't know if it was true or not and was hoping it was but so many people had been sceptical including audi dealers that I had to make very sure. It was them who mentioned court. I just want my car back on the road. I had checked with a few audi dealers and other garages in no one seemed to know and all thought it would be a bad idea.

So all that needs doing is the existing turbo,exhaust manifold and injectors swapped across?

What about the fuel pump?

Your help is much appreciated, Iain.