Swap AUA engine with AUB

67boris

A2OC Donor
Hi,
After big trouble of finding an AUA engine from Polo van that DID NOT FIT, I got an AUB engine that seems it will fit. Gearbox mounting holes are the same (not the case with Polo AUA engine). Has anyone done that? I forgot to mention I live in Cyprus and there might be a total of 10-20 A2s here.

Any info will be much appreciated!!

Regards to all,

Boris
 
I'm surprised the Polo AUA engine could not be rebuilt to suit your A2. You may have done this already but for others who don't know, normal procedure is to stand the engines side by side and swap all the parts from one engine to the other. Usual things are the intake system, alternator and aircon, oil fill and dipstick etc. For the gearbox mounting there should be a backplate bolted on the rear of the cylinder block and swapping this over normally resolves any transmission mounting problems.

As for the AUB engine, it's never been an option for the A2 in the UK so I don't think anyone here will be able to advise. Even if it can be made to fit mechanically my concern would be compatibility of the engine ECU and all the sensors.

Best of luck

Spike
 
Thanks Spike,
AUA engine I got was without ancillaries and back plate, the idea was as you suggested. I was told by local mechanic that AUB will fit, but to swap all sensors and to count notches on crankshafts to make sure they are same. I guess I'll find out soon enough. I'll keep you posted. In what car was AUB used in the first place?

Thanks,
Boris
 
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Thanks Spike,
AUA engine I got was without ancillaries and back plate, the idea was as you suggested. I was told by local mechanic that AUB will fit, but to swap all sensors and to count notches on crankshafts to make sure they are same. I guess I'll find out soon enough. I'll keep you posted. In what car was AUB used in the first place?

Thanks,
Boris

The AUB is a tuned up more powerful version of the AUA fitted to the Polo model. It has revised cams, inlet manifold and throttle on the engine amongst other things to develop a peak 100 BPH albeit with less low down torque compared to the 74BHP of the AUA.

There is a discussion on upgrading the A2 AUA to AUB spec here:

http://www.a2oc.net/forum/showthread.php?23321-differences-between-AUA-and-AUB-engine

I would say that given the different valve timing you would probably need an AUB compatible ECU to provide the correct map for the engine.

There is a variation of the AUA engine with a different flywheel and starter motor arrangement, fitted to some Skoda models I think. The gearbox mountings are not the same so that's probably what you have as the "standard" gearbox would not fit that engine.

regards

Andrew
 
Thanks Andrew,

Do you have the torque figures for these engines, I wonder how big the difference is?

As a starting point we're thinking of swapping over manifolds and throttle body and try it with the AUA ECU. If it does not work out, I'll get an AUB ECU and put it on together with the AUB manifold and throttle body. Any thought are welcome!

Boris
 
Thanks Andrew,

Do you have the torque figures for these engines, I wonder how big the difference is?

As a starting point we're thinking of swapping over manifolds and throttle body and try it with the AUA ECU. If it does not work out, I'll get an AUB ECU and put it on together with the AUB manifold and throttle body. Any thought are welcome!

Boris

Hi,

I had a look into that a while ago as I have an AUA and wanted to see if there was anyway to increase the power. There are articles in the VW forums with people with Lupo and Polo cars swapping engines and parts of engines to upgrade their power output. From what I have read, it seems to be that low down torque is less and power is more, but "it all happens above 4000 RPM".

I have found this site which lists power and torque curves for various cars and engines:

http://rototest-research.eu/index.php?DN=29&List=U-Z

It doesn't say which engine code, but assuming this is the 1.4 AUA 74ps

http://rototest-research.eu/popup/performancegraphs.php?ChartsID=539

and 1.4 AUB 100ps

http://rototest-research.eu/popup/performancegraphs.php?ChartsID=336

you can download a PDF of the power and torque curve for the engine.

On these it doesn't actually look that bad. The AUB is less until 4000 RPM when it overtakes

Torque lb-ft
RPM AUA AUB
1510 72.4 66.9
2018 79.0 72.6
2513 83.0 77.0
3009 84.6 82.9
3608 87.8 85.4
4009 87.2 87.3
4511 86.4 89.0

(roughly, the RPM figures for the 2 engines don't quite match up).

regards

Andrew
 
Thanks Andrew,
That was very informative! Torque difference is less than 10%, I don't think it will be that noticeable.
I'll write more when things start happening.

Regards,

Boris
 
Hi everyone,

As I said before I'll write more after the engine is in. It started on third attempt on the button! Running smoothly and quietly. I'm very happy!

We took manifolds of the AUA and put them on AUB, nothing else was done, apart from the new clutch kit, water pump and timing belt kit. It runs on AUA ECU!
Successful test run, waiting for the MOT, I'll keep you posted.

Regards,
Boris
 
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Well done. I always admire people that listen to all the things that can go wrong.............then do it anyway.

The fact that the engine runs may indicate you could get the AUA ecu remapped with AUB data

Cheers Spike
 
Nice! Good job! Please post some photos and a write up when you have time. This is very interesting.
 
Thanks guys,

Here are the latest news. It flew through the MOT!

Spike, an AUB ECU has been purchased and is on its way.

I noticed slight pinking in the lower rev range 1500-2000rpm on acceleration and even higher up under load 2500-2700rpm going uphill. I run it on 95 RON, but will try on 98 next fill up to see if it makes any change.

Regarding doing things my own way.... There was no other option, remember I live in Cyprus and here are very few A2s on the road, let alone crushed ones for spares. I had an AUA engine that did not fit, found an AUB that fitted the gearbox, so I decided to give it a try. They look physically same, don't know internally. They apparently have different output, maybe a different compression ratio, that's why I'm thinking of higher octane petrol.
Will put some photos soon, thanks for you replies!
Boris
 
Hi Andrew,

So I was right earlier, but I realized today that I have a four year old petrol in the tank and thought that was the cause of pinking.

Obviously, AUB engine must have a higher compression ratio than AUA, hence 98 Ron specified. Thanks for bringing it out!!

Regards,

Boris
 
Me again,

I was ahead of myself.
Just checked the specifications of both engines and the compression is the same 10,5:1.
Anybody with more wisdom?

Boris
 
Me again,

I was ahead of myself.
Just checked the specifications of both engines and the compression is the same 10,5:1.
Anybody with more wisdom?

Boris

The different cams on the AUB engine might require different ignition timing to run properly which your AUA programmed ECU won't be supplying. If you getting an AUB ECU that might sort that out.

regards

Andrew
 
Boris, if you get chance why not start a project thread? Your little A2 is goingbthrough a major overhaul at present. Would be great to see some pictures of its revival.
 
Anyone tried a CGGA or CGGB 1.4 16v swap? Can ECU from modern cars be used with A2 wiring?
 
need to look into the engine more to see, but this engine has less power than the AUB anyway. one thing is that you will need to a car with BBY engine to start with because of the coil packs. AUA and AUB run a single coil pack.
 
Yes individual coil packs from BBY onwards. Will try AUA setup first else get CGGB ECU and associated electronics a/r.
 
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