Has the time finally come for a DS3 Racing engine rebuild??

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xantia_v6
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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by xantia_v6 » 01 Oct 2019, 07:57

notrix wrote:
30 Sep 2019, 21:58
So I did a compression test today.. I got about 185psi or just shy of 13bar across all the cylinders.. seems a bit high heh??
I would put the brakes on here, just a little.

I think that it is more probable that your compression gauge is inaccurate than all cylinders have an abnormally high compression pressure.

If your compression pressure was really too high, then the engine ECU would be throwing knock and super-knock fault codes all the time.

I am not aware that these engines have any history of carbon build-up in the cylinders themselves, just in the inlet ports, which is a different set of symptoms.

I think that all of the symptoms that you initially listed could be caused by a failed PCV valve, or perhaps by bad turbo seals allowing an abnormal quantity of oil into the engine.

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by notrix » 01 Oct 2019, 11:29

I would like to try and diagnose the PCV system. I have the OEM PCV blanking caps lying around (OEM part #0361.S4). Do you think installing these would help me diagnose a faulty PCV valve? The caps are for blanking off the rear PCV connection between the rocker cover and the intake manifold.

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by xantia_v6 » 01 Oct 2019, 14:06

Yes, fitting those caps blocks off the rear PCV valve (the one that I suspect has failed), and with that blocked off, it does not matter if the front PCV is leaking, as there is no source of suction to suck excessive fumes from the crank-case. In fact on my car (which has a good vapour separator fitted), I have left the front PCV valve open, so prevent the slight pressurisation of the crankcase that can encourage oil leaks.

With the rear PCV blocked off, any blow-by past the piston rings will come out the front breather and be easy to detect (there will normally be some, but not an excessive amount at idle.

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by notrix » 01 Oct 2019, 14:48

Ok.. I'm a bit worried about possibly increasing the cranckcase pressure if I fit the caps but I guess for testing purposes it should be ok. I'm gonna install the catch cans I have soon but I need to figure out if the rear PCV system has failed anyways so..

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by xantia_v6 » 01 Oct 2019, 14:58

Any positive pressure in the crankcase is vented via the front pcv valve to the turbo input, as it always was when the engine is on boost.
For test purposes I would leave the front pcv hose disconnected so that you can see how much vapour is ejected.

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by notrix » 01 Oct 2019, 15:03

Allright.. Cheers. I'll try that :)

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by notrix » 03 Oct 2019, 22:28

I just installed the rear PCV blanking caps. No difference regarding the rough idle. I filmed a short video of the front PCV hose after blanking off the rear one. Of course I forgot to check how it was before :?

Here's the clip;


If you're on a computer sorry for the aspect ratio :lol:
Last edited by myglaren on 03 Oct 2019, 22:47, edited 1 time in total.
Reason: YouTube link

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by Nemo26 » 05 Oct 2019, 20:26

I've seen high pressure fuel pumps failures in the way that the fuel leaks through them in oil line. Remove crankcase pipe and block the hole to engine temporary and check fuel trims before and after. You'll see improvement. Fuel evaporetes from oil sump and creates rich condition, there is basicly one more fuel source and that is fuel vapour from oil sump which goes trough crankcase breather pipe in intake manifold. Ecu tries to compensate and cuts flow trough injectors (rough idle).

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by notrix » 06 Oct 2019, 12:24

Nemo26 wrote:
05 Oct 2019, 20:26
I've seen high pressure fuel pumps failures in the way that the fuel leaks through them in oil line. Remove crankcase pipe and block the hole to engine temporary and check fuel trims before and after. You'll see improvement. Fuel evaporetes from oil sump and creates rich condition, there is basicly one more fuel source and that is fuel vapour from oil sump which goes trough crankcase breather pipe in intake manifold. Ecu tries to compensate and cuts flow trough injectors (rough idle).
Thanks for the tip. Do you mean that fuel could leak from the pump internally in the engine block?

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Re: Has the time finally come for a DS3 Racing engine rebuild??

Post by Nemo26 » 07 Oct 2019, 04:34

Yes, hp pump is lubricated with engine oil.