A guide to preventing detonation

[Taggy]

With the recent spate of people melting pistons on new builds etc I thought it was important to go over a few points so it helps other people from happening to them and costing them an expensive rebuild.

I found a REALLY good video on youtube about it and its also helped me uderstand a few areas which i didnt get and also more importantly should you use a higher octane fuel on a car thats not mapped for it.

He talks about what is detonation and how to prevent it

The effects of having too much advance on your timing

Reasons to reduce your compression ratio i.e use thicker head gaskets

and what happens when you increase the compression ratio, bad! i.e having head skimmed, oversize bores etc.

Well worth a watch

I also liked the fact that higher octane fuel is much less likely to det, even if its not mapped for it, so its safer to run it in general (which i didnt agree with before) as if your timing is out its less likely to det on you and cause other problems.

100 ron it is then

Edited April 20, 2013 by Taggy

[micky boy]

Exhaust temp gauge is a good investment they can tell you more then you think

Not a bad vid that

[AdamB]

Thats just the basics.

You need to look at silly little things like the quench area, the distance between piston rings, valve positioning, connecting rod stretch.

One reason why the Wiseco pistons are very good is that they maximise the quench area and yet still retain a dish, this dish in the centre of the piston helps reduce the compression ratio, but at the same time, the outer edge of the piston still forces the mixture in towards the spark plug. Remember that the initial flame starts in the centre and works its way outwords.

Some pistons which are able to run a tight oil clearences have an increase in silicone, this is great for N/A engines where it can withstand higher temperatures and is much more hard wearing. However on forced inducted motors, as the increase in silicone in the material makes them brittle and prone to breaking.

The top ring is the first compression ring and 70-80% of combustion heat is lost through the top ring into the water jacket, the second ring takes around another 10-15% and the oil control ring takes like 5%. The distance between them is crucial as the crown of the piston will retain heat and turn to chocolate. As the piston rings wear, the oil control ring is placed with a larger task of transfering heat into the water jacket, which is bad!

Remembering also that as heat and rpm increases the connecting rods stretch, this changes the piston to valve clearence. Having the pistons at the same deck height in all cylinders helps equalise the compression pressures.

Edited April 20, 2013 by AdamB

[Taggy]

Sounds like you know your stuff Adam! I have just put the head back on my car hoping to get it back together today touch wood and get a beer in!

[triple j]

Good thread, Adam what do u think of these, http://www.ebay.co.uk/itm/Turbo-Cars-Knock-Det-Alarm-Engine-Detonation-Detector-Visual-LED-Alarm-/190816183362?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2c6d87e442

Edited April 20, 2013 by triple j

[Patches]

Cool video. Learn something new every day

[AdamB]

Good thread, Adam what do u think of these, http://www.ebay.co.uk/itm/Turbo-Cars-Knock-Det-Alarm-Engine-Detonation-Detector-Visual-LED-Alarm-/190816183362?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2c6d87e442

Similar idea as to what I've got in mind making mate, although is far too complex than it needs to be. Only need one light, knock is knock, don't need various lights to tell you its there. Plus I can probably make one for about £20 I might try this at uni on Tuesday if I can get hold of the equipment.