Audi Quattro rebuild

[Alan]

Hi Guy,
I have not been on your site lately but it looks like you have been busy!
Not much done with my 131 but I have got stuck into rebuilding the engine in my 1988 ur-quattro.
The engine is coded MB, 5 cylinder 10 valve, turbocharged, Bosch CIS mechanical injection, Hitachi ECU controlling ignition and boost.
Its ancestry is the VW 4 cylinder engine with an extra cylinder stuck on.
Essentially a flashing oil light and smoke on boost prompted my to check the oil pressure with a gauge, which showed only 1.8 Bar cold, quickly dropping off to little over 1 Bar.
I pulled the caps of a few of the bottom end bearings to find scoring on both the journal and shells:

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I also found this goo in the intake at various areas:

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It would appear by the amount of petrol in the oil that I have a leaking injector to blame for this wear.

I have removed the engine from the car:

DSCF2635.jpg (60.6 KiB) Viewed 18273 times

And stripped all the ancillaries:

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Before removing the head:

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After removing the cam, there are signs of wear on the cam itself and also the bearings as the scoremarks show on this montage:

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There seems to be about 0.3mm radial play at worst in the cam.
Is this an acceptable amount of wear of is my head unuseable?

I have to admit that this is my first proper engine rebuild, and it’s a serious undertaking.
This may not be an engine you usually deal with but any advice that you can offer would be much appreciated (and hopefully some interesting reading for your forum).
Kind regards,
Alan.

[andy97]

If I may (and with Guys permission) can I suggest that you talk to Roger Galvin at the "quattro workshop" in Lutterworth. He looks after my quattro & has done for over 10 years; he is the tech secretary for the quattro owners club, looks after nothing but quattros & even Audi ask him for advice these days.

[Alan]

Hi Andy,
Thanks for the reply.
I have spoken to Roger in the past, a martyr to the quattro at this stage, and very helpful.
As this is an engine rebuild though, I thought that the techniques and expertise in relation to engine rebuilding my be easier found on a forum dedicated to just that, which I posted here.
It may be an oddball engine being an I5, but its still an engine that could be in any car, not necessarily a quattro.

I hope to find out if its possible to line bore the head and fit some from of shell bearing and regrind the cam journals suit.
Any takers??

[4v6]

Hi Alan, ive been working on these particular engines for a while also as im in the midst of a rebuild on a 1984 Ur Quattro.

The cam bearing journals in the head when worn are specified by the manuals as being not repairable, hence it would mean a replacement head.
However, im wondering if you could get the bearing locations line bored as you suggested but have a camshaft ground with an oversize journal to save the head that way, or maybe have the journal built up by some kind of metal spraying or deposition process?
Ive tended to plastigauge the cam journals to establish oil clearances but there does not appear to be a figure specified for these, only an acceptable end thrust figure for the cam itself.
I recently plastigauged a set of these cam journals which came out at 3 to 3.5 thou across the range and i have not yet found any larger than that so far.
I hope this post is of some use to you.

Tony.

[Alan]

Thanks Tony.
From the data I have regarding the MB, the radial clearance on the cam bearings when using Plastigauge is .1mm, so at .0035" you are nicely in tolerance.
I hope to find out more info about the line boring process this week, failing that its a head replacement (not impossible to get uesd).
I am still trying to get to the root of the engine wear in the first place.
I did a leakdown test on the engine before all this, and found the pressure loss was consistent across the 5 cylinders at 10 PSI (100 PSI input, 90PSI on the restrictor side), which I believe is OK.
After measuring the piston skirts they were about .015mm outside the factory tolerance of 80.98mm -.04mm.
The cylinder bores should be 81.01 to 81.09mm, 4 of the bores measured about 81.07 and no 5 (rear of the engine) 81.11.
I dont know if this would affect the performance, perhaps someone might be able to offer some general advice on this.
The looseness of the bearings on the cam would obviously lead to reduced oil pressure, and the same at the bottom end.
Here is what one of the crank mains looked like (these got progressively worse towards the rear, the oil pump is at the front):

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For a device immersed in oil, the pump seems badly scored to me, but perhaps its normal:

DSCF2687.jpg (67.75 KiB) Viewed 18034 times

Any information greatly appreciated...
Al.

[Guy Croft]

There are rebuilds and 'rebuilds'.

Given that GC Q&A is for competition engine related Q's only - is this such a thing? And if yes, and given the huge scope of the subject - you better outline your suggested rebuild spec before I comment.

The other thing you must do is get a Haynes manual and read it thoroughly.

GC

[andy97]

Guy

I'm not sure that Haynes manuals exist for the proper Quattro - the engines are unique, although based on simlar architecture as others in the Audi range.
The Quattros were designed as homologation specials and not meant for long term serial production hence the reason why Haynes didn't cover them; they were hand finished and not many Quattros are actually identical in many details. I think that Roger Galvin has original Audi workshop manuals and micro-fiche.

[Guy Croft]

OK, doesn't matter overmuch as the strip, inspect and overhaul details of engines are pretty generic. Get any Haynes manual for a similar engine (even if 4 cyl) and that will be a big help. Some data eg: crankshaft adn rod dimensions might be listed in things like Vandervell bearing catalogues that I have here.

Now: For competition or road? is this just a strip, check and rebuild 'as-is' or is it overhaul and modify?

Although GC Q&A is for competition engines only I am prepared to help in this case.

The first job, FWIW (!) is a total strip and clean, all parts laid out ready for dimensional checking. Those parts an expert might ordinarily throw away after a quick look (bearings, seals etc) retain for reference.

It will help you greatly if you document the strip with detailed photos.

GC

[Alan]

Hi Guy.
To answer your first question, I am planning to upgrade the car to a higher performance spec, but the closest to competing will be track days, so not really a competition car.
My current plans are to remove the CIS injection system and run full EFI with COP, upgraded turbo, and a manifold to relocate turbo to the unused CIS space.
The standard output is 200 BHP, and when the project is complete I am aiming for around 300 at the wheels.
The typical route is to fit one of the 20v I5’s from later models such as the 1996 S6, but it doesn’t have the raw scream of the 10v and most aim for much bigger power with the 20v anyway.
For now though I need a solid engine, and having had a good chat with a machine, I am most likely going to go the whole hog on the rebuild, custom pistons and so on.
With regard to a Haynes manual, as Andy mentioned, there never was one. Too few of these were made (around 11,000) I suppose.
I do have a lot of the original factory manual which is where I have got my data to date.
I have loads of photos taken of the strip down; I can post more pics if you like.

I hope this makes some sense.
Regards,
Alan.
PS, I have thrown nothing out!

[Guy Croft]

Yes, re Haynes manual I take the point about non-aval but you must get hold of any engine manuals you can (Toyota ones are especially well illustrated & written) and study them from cover to cover. You have indicated it's your first engine build so to compensate for lack of exp you have to read extensively! Engine building of all kinds is fraught with hazard, even for the pro. It is in the nature of engines that they really do want to break.

I trust you take my point!

Now, to give you an idea of what's involved I have drawn up a typical engine overhaul/mod list, it's the kind of thing I use routinely when costing things at GCRE. I cannot guarantee it's 'exhaustive' but it is a very good start. You should never overhaul or modan engine without something like this because you'll miss an op or get it out of sequence. It is, by the way, written in a reasonably logical sequence.

Hope_this_helps

G

[Alan]

Thanks for the list Guy, very useful.

With regard to the head, would there be any advantage in opening up the ports and doing other head work being its turbocharged?

Al.

[andy97]

Not sure wheher this is very helpful comment or not but is it worth looking at what Audi did with their original rally car engines - talk to someone at David Sutton (Historic Motorsport) in Daventry & there might be some basic (but useful) info on the engine prep in some of the Quattro books that were written. Also, there is a goy called John Hanlon who has at least two ex works Group B quattros in captivity and he might be a helpful source of info & contacts. Again, Roger Galvin will have contact details via the quattro owners club.

[Guy Croft]

"...any advantage in opening up the ports and doing other head work being its turbocharged?"

Kind of depends who does it really...

G

[Alan]

But of course Guy!
Im just wondering if there are as significant gains to be had reworking a turbo head as a NA head, especially from a cost/power increase point of view.
Alan.

[Guy Croft]

Yes, Alan, as has been said many times by me here, it can be the case.

I have not yet met the head that could not be improved - though some may exist. Heads vary from very good to pretty dire, and the more modern the head the harder it is to generate gains. Not because they are all so good but because, increasingly, OE designs have design features - for cost-saving and because of the architecture of the engine layout - that stand in the way of tuning modification.

Gains can come from in/ex/inlet manifold & port mods (shape, size) and/or valve/seat mods.

I bought my Superflow flowbench some 5 years ago specifically so I could assess these things and take the er, guesswork out of this vast subject.

I can't tell you what gains are to be had and what mods are needed/desirable on your particular head because I have never worked on one. But given it's age I figure there are significant gains to be had.

GC