Originally posted by Wizard-of-OD
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LOL, I was waiting for someone to ask that. took that pic after I popped the pistons back in this afternoon, the caps are off, hopefully get it all bolted up tomorrow.Mark - Modded -
I see what you mean about the colour. Something has been going on in there for sure on the 2 cyls at each end. God knows what tho at the moment. If you get it all back together and that noise is still there then i will take a trip to yours and have a listen if you like.sigpic
Tom C - www.rcmr.co.uk
Audi UR Quattro
Audi 100 C3 2.0 5 cyl 115ps
Audi S2 - 07k engine project aiming for 800ps
Audi B5 RS4 645ps 911nmComment
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Originally posted by audiman
Cheers Tom, hopefully wont come to that. Bottom end is all built up again, I'll get the head back on it soon.Mark - ModdedComment
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I have had the motor up and running for the last four days, it is still making a noise (rattling type of knocking sound) when it is cold, as soon as it and the oil (10W/60) warm up it more or less dissapears.
Now I know that there is nothing wrong with the bearings as I have checked them, even changed the big ends, it is not any of the driven ancillaries (PS pump/alternator) as it still does it with the belt removed.
I also have a problem with a fooked CV joint, but that is easily sorted, the noise from the engine is not and it is turning into a PITA for me.
Other than that the engine runs OK, but I have no idea what the problem is, does anyone have any idea where to look or what it could be?Mark - ModdedComment
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Is it still coming from the bottom end mark and not the head areaComment
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Noise in engine
Have you looked at your valve springs. I had an inner spring break on my 20vOriginally posted by Mark Halligan
7a engine. There was a rattle from the top end of the motor which sounded as if the distributor gear & camshaft gear were worn out. Also, check the timing chain between the two camshafts."Nulla tenaci invia est via"Comment
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Martin,Originally posted by martinjs
sounds to me as if it is coming from the cylinder area, but I could be wrong.Mark - ModdedComment
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I havent yet, what sort of sound did it make, did it quieten down when the engine was hot?Originally posted by TECH48
Mark.Mark - ModdedComment
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Mark,
Sorry to hear that.
Could it be "piston slap". That normally occurs when cold and disappears when things warm up due to the expansion of the pistons. Not sure what JE specified for bore clearance. Was it greater than std?
Is it a different noise to the one that started the tear down?
Are others running JE pistons experiencing similar symptoms? Doug!!Comment
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Mark.
If I remember correctly "piston slap" came fitted as std on the 2WD Cozzy, larger displacement Range Rovers and apparently the 97/98 Scooby. I'm pretty sure that the solution was, at least on the Cozzy and Rover, to offset the piston pin. Obviously not a solution for you. Can you consult JE for guidance? Question is, what if any, damage is being caused. Scuffing of the bore might be one.Comment
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I do not experience this on mine.Originally posted by twoqu
I don't think Mark did the first few days it was running either? I never noticed it when he was in Scotland.
What do you mean be offset the pin? I thought our rods were not quite in the centre of the pin - I think that Jeffer or Cees designed their own JE pistons with that in the centre - I might be wrong.S2,RS2,S4 WB,RS4,S4 B8,RS6 C5,RS6 C6,R8Comment
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Yes Doug you are right on that, Cees and I designed our own pistons together with our workshop and have the wrist pin in dead center.Originally posted by Doug_RS2
But besides of that, JE pistons are known to have very little expansion, opposite to other piston brands like e.g. Ross. So that would imply that they have zero to no slap.......
CheersComment
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Just to recap the motor ran without any noise other than normal for 2k plus miles, following the overboost incident during the mapping session it started making the noise. This caused me to take it apart and find the damaged pistons which were then repaired, but its still doing it when cold, once the engine is hot the noise can just barely be heard.
Using a digital micrometer I did measure the bores when I had it out and I got a bore figure of 81.48mm and a piston at 81.35mm, giving a clearance of 0.13mm. Whilst I am not the greatest at using a micrometer, I believe these are fairly accurate readings.
If it was piston slap wouldn't it have done it straight away when started for the first time?Mark - ModdedComment
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That's a bitch - maybe its a small-end ??? BUt then that would make a noise hot or cold ???
PaulPaul Nugent
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Using a digital micrometer I did measure the bores when I had it out and I got a bore figure of 81.48mm and a piston at 81.35mm, giving a clearance of 0.13mm. Whilst I am not the greatest at using a micrometer, I believe these are fairly accurate readings.
Mark,
I'm not saying it is definately piston slap, but merely chucking in suggestions. It would certaintly suggest something changing due to heat.
Out of interest, why were the pistons not specced to Audi bore sizes. I know JE have a particular way of measuring the piston. However, if the std Audi o/s dimensions are 81.51mm bore and the piston is 81.48mm that is a piston bore clearance of 0.03mm. From your calculations, you have an extra 0.10mm clearance. Dosen't seem to fit other peoples claims that the JE's are tighter.
I thought forged pistons generally were run looser as they expand more. After all, racers are only interested in what the engine does when hot. I remember standing near the 205T16 when it fired up and it sounded like a bag of nails!
Doug or anyboby else, what are your clearances?Comment
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