Author Topic: Feasibility of an AAV turbo as a daily  (Read 8473 times)

Offline Fred

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Re: Feasibility of an AAV turbo as a daily
« Reply #15 on: May 27, 2010, 08:45:12 pm »
Wasn`t their a guy at DK`s while scrapping that 1 Ltr polo that had a Turbo`d AAV and had been using it for 18 Month
or so with no problems.
Would be nice to here the full build of what he`s done with it.

Fred.

Offline cheys03

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Re: Feasibility of an AAV turbo as a daily
« Reply #16 on: May 27, 2010, 09:51:31 pm »
The only AAV turbo I'm aware of was Tommo's before it was replaced for an ABD with machined-down pistons as (I believe) one of the head bolt threads in the AAV block got stripped. I'm sure Tommo will correct if I'm wrong, but I think he had a fair bit of boost going through it too.
I found another thread on a golf forum for someone turbo-ing an NZ (same engine block/head basically as AAV) in 2003, apparently lasting only a month or so it didn't like a bar of boost. The headgasket went so it may have simply been a pending failure anyway as there is no mention of it being a fresh gasket.

http://www.clubgti.com/forum/showthread.php?t=3170

But if the AAV you mention Fred isn't Tommo's, any info would be very interesting as you say
« Last Edit: May 27, 2010, 09:58:12 pm by cheys03 »

Offline Andy

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Re: Feasibility of an AAV turbo as a daily
« Reply #17 on: May 28, 2010, 10:48:50 am »
What have you done for a catalyst on your Polo? On your CP blog it looks like you've got a standard CAT welded to the downpipe?

I've done a little research into the knock sensor used by the G40 management. In a couple of other threads here you mention the simplistic nature of this sensor and raise doubts as to it's effectiveness. Clearly it's there for a reason, but in your opinion is it worth fitting? Perhaps in order to fool the ECU into not raising a knock sensor fault a suitable resistor could be attached across the relevant terminals? I'd happily avoid having to remove the engine and get the block tapped if knock can be addressed using another method...?
Got my downpipe from eBay.de, so it came like that. There's definitely the shell of a catalyst there. ;)

Very good geekery about knock sensors here:
http://www.rhinopower.org/knock/knock.html
http://www.rhinopower.org/knock/docs/bosch_ks_ds.pdf
http://www.picoauto.com/tutorials/knock-sensor.html

As you can see, the knock sensor input doesn't go through simple passive input circuitry - so the ECU diagnostic is unlikely to be fooled by just sticking a resistor across the terminals. Personally, I'd fit it - at least to the wiring harness. If you don't mount the sensor to the block you'd have to make sure you secured it somewhere properly - could probably mount it to the inlet manifold fairly easily. There'd be a risk that it'd pick up vibrations from wherever you mount it and mis-interpret it as knock though.

So:

- Least risk would be to machine your block (ensure the boss is machined flat as well as tapping the hole) and fit it there.

- Easiest would be to bolt it to the inlet manifold, though there's a risk you might have to move it if it picks up vibrations that confuse it!

Offline cheys03

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Re: Feasibility of an AAV turbo as a daily
« Reply #18 on: May 30, 2010, 04:05:27 pm »
Hehe, thought it might be but a shell of its former self…!
Thanks for the knock sensor links, some very interesting, detailed information. I can understand why you say a resistor is unlikely to fool the ECU.
I’ll probably find a suitable aluminum cylindrical 'bush' or get one machined, and welded to the inlet manifold with a captive nut on the non-knock sensor end -  a) Because I'd like to use as standard an AAV engine as possible in case it goes boom (easy replacement) and b) because I'm interested to see if it works! If it doesn’t work, at least we’ll know.
The parts gathering process has begun…

Offline hayesey

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Re: Feasibility of an AAV turbo as a daily
« Reply #19 on: May 31, 2010, 09:36:45 pm »
why dont you just bolt the knock sensor to the block rather than going to all that effort for no benefit?

Offline cheys03

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Re: Feasibility of an AAV turbo as a daily
« Reply #20 on: May 31, 2010, 10:05:25 pm »
It's a fair point. My main reason is that I'd have to remove the block to get access to drill it, possibly then take it to a machine shop to make sure it's dead-centre and the face is flat. As it's my daily driver I'm looking to do the work within 1-2weeks and removing the engine would be quite a pain. I've a spare GT inlet manifold on which the knock mount can be made while I'm collecting parts.
If the inlet manifold position turns out to be OK, I've saved the hassel of removing the engine. If the position is not OK, it's cost me a little time and a few pennies.

But I welcome alternatives, other methods etc. Especially if the block could be drilled&tapped&flat the face without removing the engine or if you can recommend a proceedure to drill&tap&flat the face myself without having to take the engine to a machine shop.

Edit: I can drill & tap, but can't think of a way to skim the face
« Last Edit: May 31, 2010, 10:16:33 pm by cheys03 »

Offline hayesey

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Re: Feasibility of an AAV turbo as a daily
« Reply #21 on: June 01, 2010, 09:32:23 am »
I'd just be worried about it picking up false positives when it's in a non-standard place, it might even pick up the sound of the throttle plate opening and closing.  I'd prob just fine somewhere else on the block to attach it.

Offline cheys03

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Re: Feasibility of an AAV turbo as a daily
« Reply #22 on: June 01, 2010, 10:03:35 am »
That's a good idea - if not the std postition on the block perhaps there is another possible position that won't require the engine to be removed. Thanks

Offline PeteG40

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Re: Feasibility of an AAV turbo as a daily
« Reply #23 on: June 01, 2010, 10:15:36 am »
does the face have to be skimmed? theres a stub there anyway - could you not just crudely skim it with a file?

Offline hayesey

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Re: Feasibility of an AAV turbo as a daily
« Reply #24 on: June 01, 2010, 10:27:57 am »
yeah I'd have thought you'd get away without skimming it properly but you will need to drill and tap it which I can't imagine is going to be easy (or possible) with the block in-situ.

Offline Andy

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Re: Feasibility of an AAV turbo as a daily
« Reply #25 on: June 01, 2010, 10:44:06 am »
The surface MUST be flat for the sensor to work properly - bolting it to a crusty block won't do, that'd be riskier IMO than trying it on the inlet manifold. You'll end up picking up all the vibrations in the scabs/flakes of rust. Dressing it with a file should be okay though - ultimately will depend on how crusty the block is!

It might pick up false knock on the inlet manifold, but given that the input is highly filtered you'd have to be fairly unlucky to get a repetitive vibration at the same frequency as knock. Also bare in mind that the inlet and head aren't exactly isolated from vibration in the block (and vice versa) anyway!

Offline Fred

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Re: Feasibility of an AAV turbo as a daily
« Reply #26 on: June 01, 2010, 08:22:54 pm »
As said by Andy it needs to be smooth and flat + the tapped hole needs to be square to the machined face.
Its possible with patience to file it but after that i`d lap it with wet an dry wrapped round a block of alloy or
hardwood perhaps.

Fred.

Offline cheys03

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Re: Feasibility of an AAV turbo as a daily
« Reply #27 on: June 01, 2010, 10:57:07 pm »
Thanks everyone for the information and debate - it's very interesting to me and I appreciate all the ideas and advice.

Have possibly found a solution after studying a spare engine -





The highlighted bolt hole is M8 and fairly deep, but isn't used (at least on my AAV). It's at the bottom of the block near the sump (knock sensors are at the top near the cylinder chambers to be in a better position to detect knock?) but hopefully can be made useful with a light file and wet&dry. Providing the standard knock sensor loom is long enough...
What do you think?

Offline PeteG40

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Re: Feasibility of an AAV turbo as a daily
« Reply #28 on: June 02, 2010, 08:26:55 am »
not sure the loom will be long enough - but you could try it.  The stud above it is normally where the hole is.

That thred is for a support bar for the inlet manifold btw

Offline Yoof

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Re: Feasibility of an AAV turbo as a daily
« Reply #29 on: June 03, 2010, 05:55:30 pm »
I'd use the stock location- what little calibration there is on these sensors will require it to be in the standard location.

Last thing you want is knock being mis-detected by the ecu. With some patience you could easily drill the necessary hole and flat the surface- worth getting this right early on.