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Polo 86c: Reduce Diesel Particulate Filter (DPF)

 
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PoloTD



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Post13-10-2017, 2:39    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

Hi!
My name is Frithjof, and I'm new here.
I own two Polo 86c cars, both with the 1W diesel engine.
One of them has been modified with a K03 turbocharger and is registered with 68 horsepower.
Unfortunately, I didn't perform a complete overhaul, but rather a modification.
That brings us to my problem.
The head gasket (soft material/metal) was defective (it had blown between the 1st and 2nd cylinders at a boost pressure of 1.2 bar) and I thought I was doing the engine a favor by replacing the head gasket with a compression reduction kit using two metal head gaskets. I calculated that this would reduce the compression ratio to 19:1 instead of the original 22.5:1. According to general calculation formulas, this is the range where I should be able to achieve a boost pressure of 1.2 bar.
Unfortunately, the engine is now emitting white smoke and has virtually no power, let alone boost pressure (at most 0.3 bar). The smoke is clearly free of water and only smells like diesel. The engine also runs very unevenly, meaning with significant fluctuations in RPM and misfires. Starting is difficult (it takes 7-12 seconds of cranking).
Now, I've discussed with two colleagues what might be going on.
"Some people say that the compression is now too low, which is why the diesel fuel evaporates to a greater or lesser extent."
The other person simply said that the fuel injection pump (Bosch VE) is broken.
I've been thinking about whether a swirl chamber diesel engine requires a higher compression ratio than, for example, an older TDI engine.
I also wanted to measure the compression, but I have no idea what it should be; although I suspect it should be at least 20 bar.
Why am I having all these problems? I'm at my wit's end (and my nerves are shot)!
Thank you for your responses.
Best regards,
Frithjof


Translated on 29-09-2026, 2:03.
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Post13-10-2017, 6:40    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

Hello,

Okay, so, with two head gaskets - sorry, that's nonsense.
I would have accepted a maximum of three holes, but this is too much.

I mean:
Even if you want a compression reduction, SO does not work with a swirl chamber diesel engine;

So:
Install the correct head gasket, and if there's no enrichment system on the pump, what's the purpose of such high boost pressure?


Translated on 29-09-2026, 2:06.
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Herbert
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Post13-10-2017, 9:30    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

That's all that needs to be added: you didn't perform the required compression test, and the lower compression anyway brought the reading closer to the wear limit, making the test pointless.
Based on the symptoms, it appears that there simply isn't enough hot air to ignite the fuel.
hg
Herbert.
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Translated on 29-09-2026, 2:08.
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Post13-10-2017, 9:55    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

"@Gremlin, I have a larger pump with LDA lying around. It was already running with the previous owner. And you misunderstood me about the gaskets. I installed them the same way as in a turbo conversion for a gasoline engine: metal head gasket - reducer plate - metal head gasket."

"@Herbert, after installing a new head gasket/reducer, I have never measured anything before. It has always worked like this."

How does the compression ratio work in this engine, and is 19.5:1 too low for this type of motor?


Translated on 29-09-2026, 2:09.
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Post13-10-2017, 10:16    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

To ensure this continues, please review and post here:
- Compression test of individual cylinders (cold).
- Function of the preheating system;
- Valve timing (NW camshaft, ESP control unit hub on the camshaft).

hg
Herbert.
Horch A4 8K CJCD
Golf 7 DDYA
(+ Audi 80 Avant B4 1Z 475Tkm - habe ich vom ersten bis zum letzten Tag gerne gefahren)
(+ Passat Variant 32B CY 400Tkm)


Translated on 29-09-2026, 2:10.
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Post13-10-2017, 10:17    Subject: Polo 86c: Reduce Diesel Particulate Filter (DPF) Quote

Hello,

I completely understand how it was done, but it's still "poorly executed" or "sloppy work."

Please do some research to find out where the combustion chamber is located in a vortex or pre-combustion chamber diesel engine; then you'll understand what I'm talking about.

Just a side note:
RA/SB diesel engines (like the 80hp Golf 2, with an intercooler) have a slightly higher compression ratio and slightly smaller injector nozzles compared to the standard 72hp TD engine.

I would like to stop here and continue with the original compression process.


Translated on 29-09-2026, 2:11.
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