Ping Pong

[zain_c]

stock cam Panic.

[joggiep]

Ok I'll try but .. first things first..

Comp tests revealed nothing wrong. Constant comp of 9.5 in 3 of the cylinders and for some kind of strange reason (think it is mass production factory cast error) the 3rd cylinder was 10.5

A compression test unless you have skimmed the poor head to hell and back will not help point you to the reason why the car is pinging. Generally a
5-10% diffrence in compression is ok so that 1 piston is borderline..

In my mind and the way I understand the old K-jet system is that you have a base fueling and timing and timing gets advanced via a vacuum system.. So firstly make sure that the vacuum lines are all still in good nic.
Then was deg of timing are you currently running at idle ? have you shot the timing with a timing light and is so was it a decent quality gun ?

The reason Panic is asking you to run octain booster is to see if it's an setup of hardware issue (if we are on the same page). Have you checked the pluggs yet ? what pluggs are in there and what is the gap set at ?

[panic-mechanic]

Timing is advanced by centrifugal weights. Vacuum advance will add to it under partial cruising throttle and that should be taken out if you put your foot down.
Yes i advised octane booster as that will tell you if it is a high CR issue. You can probaly improve on it by running a longer cam.

[HendrikCTI]

Well, the first thing we did was to do a comp test to see if it is not comp related as I wasn't the first owner of the car. We didn't know if the head was possibly previously removed before and incorrectly skimmed. That is mos the easiest, cheapest and quickest way to see if something is wrong. Or am I wrong.

Sorry for hijack

[joggiep]

To add to what I said if to be very carefull of the diffrence between Compression Ratio (High CR could cause pinging) ie 10:1 CR
and a compression test reading of say 10.5 bar on one piston.
Take my Jetta for an exsample I know my CR is 8.5:1 but when I do a compession test I get 140/145/140/140Psi or 9.6/10/9.6/9.6 Bar.

[zain_c]

@panic...dumb question. But by saying longer cam i'm assuming you mean a wilder cam like a 272 or 276?

[panic-mechanic]

Somehow people still think that a compression test and compression ratio are the same thing. Compression test will tell if the rings and valves are in good condition and that is that. It will tell you absolutely nothing aout CR.

[panic-mechanic]

@panic...dumb question. But by saying longer cam i'm assuming you mean a wilder cam like a 272 or 276?

Yes. It has rhe effect of lowering the effective CR until higher in the rev band.

[HendrikCTI]

I am curious.Why is your car also having a slightly higher comp only on one piston? Not saying something is wrong, it is just that I am curious to understand this strange thing.
No worry, I understand the comp thing. I knew that the 10.5 is acceptable and would not cause the pinging problem I had. But mechanic told me that we must first do a comp test to see as I never did one before to check it anyway.

Sorry again for hijack

[joggiep]

Stephan thinking of it I remember those little cetrifugal weight now.. it's the same jobbies that is basicly the RPM limiter IIRC.. Could it be that those "springs" get worn and it's adding to mutch timing to quickly ? In that case it might be worth is trying to find a diffrent dizzy and testing ?

Easiest way to see it the head has been worked on is to do the timing as the timing marks on the cam pulley won't line up with the block..(assuming that you still have a stock cam pulley).

[panic-mechanic]

The weights does not do the rpm limit no. What does happen though is that the springs get tired so it adds timing too fast. Somebody like distributor remanufacturers can probably fix it and also change the max timing allowed etc. Ie. they can basically recurve the advance curve.

[HendrikCTI]

This now makes sense. When I still had the car back in the day I also concluded that it must be something in the distributor but there are no local distributor remanufacturers and I didn't want to look for a second hand one that might also have worn springs and possibly a million km's on it. So I opted for that vacuum trick to lock the dizzy. As mentioned, it is gone now and I do still miss that power when it was setup like it should with timing and the vacuum advance pipe to the distributor. That thing with it's long gear ratio would still spin happily in first gear when you pull away from a robot and quickly put your foot down and the torque comes in at 2500rpm. Was later my wife's car and she numerous times said she enjoy's the car's power.

Sorry again for the hijack.

[VWicked]

interesting read...

[vdub caddy]

What about the type of fuel,

You only get 95 at the coast right?

[joggiep]

Fuel could potencially be the issue however it sould be solved by slightly retarting the base timing on the dizzy by moving it a little.. seems that he has already done that and it is still pinging. Same reason Stephan asked him to add octaine booster .. see if it can be solved by timing..

Still belive that that is not the issue.. Seems to me like it's adding to mutch timing to fast.. and base timing won't really sort that out.

[turbodub]

is the ping really an issue though under these circumstances ?
when i had my 1800 8v Gti mk2 I also would have a similiar issue but there was no way we could get rid of it and from what i was led to believe it is an issue common to the motor . I did lots of hard km's as did the next owner and the car is still running sweetly with 300000km on the clock . Also was the original motor from the mk1 Gti not designed for leaded petrol and now it is running unleaded ?

[joggiep]

Also was the original motor from the mk1 Gti not designed for leaded petrol and now it is running unleaded ?

Thats got nothing to do with the pinging of the motor.

Look on a NA motor pinging is not as bad as on a turbo motor but thats not to say that it's good for the motor either. I have seen even on NA motor where a High RPM ping under load has caused a motor to say goodbey to this world.. Just as Rinus.

[VWicked]

well yes, detonation is never good. I doubt its motor related, perhaps a new dizzy would help as well

[Jetta2]

You only get 95 at the coast right?

No, 95 Octane has been available everywhere (well, almost everywhere) around the country for yonks already.

[vdub caddy]

You only get 95 at the coast right?

No, 95 Octane has been available everywhere (well, almost everywhere) around the country for yonks already.

Maybe I should have phrased that better.

They only have 95, whereas we have 93 and 95.

I remember being in Durban and they didn't have any 93 at the pumps, but that was only at one garage.

[VWicked]

yes 95 only at coast... no 93 in durban.

[zain_c]

will my car use the same dizzy as a that of a CTI?

[joggiep]

If it's stock K-jet still then yes.

[zain_c]

yes it is.

Thanks guys

[maranou]

once on a gti mk2 with k-jet i saw the pipe running to the distr had a sqaure move thing on there where the pipe goes in from intake and then out to distibutor,think it was shot as kar pulled very k@k,removed and the think came alot alive,so maybe try that,and make sure all facume line's are ok,and your injectors spray also ok, remove injectors from intake buy pulling out (and get new seals before hand as they wil kaka) and then lift up airbox and move feul arm up so they can spray and watch the spray patern if ok and making a mist.not a dripp,the esiets way would be to fit mp9 head and loom and decoded box,all your warries gone