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Destruction testing...

2376 Views 25 Replies 16 Participants Last post by  04siguy
Without any hard data to go on, I decided to see exactly what a stock K20A and K20A2 could stand up to RPM wise, and what would break first.

First the K20A2, this was out of a UK Civic Type R, it had dome some 5K miles before I got hold of it...

We ran it for just over 4 hours at between 8,250 and 8,750 RPM on 100% throttle, when this happend!

one of the inlet valves snapped off just below the collet, dropping the valve down the bore (in the pic, the head is just rested back on it's seat).

looking at the bit's that are left, there is no clear reason why the valve failed, the break is clean and it's not where we expected it to fail (was expecting the head to fall off or the like).

clearly it's made a mess of the piston and head, but that's the total extent of the damage.

The K20A was next up.

this was subjected to the same treatment, after 4 hours it was fine, so we increased the revs to 9,000, then 9,250, and kept going till...

this ultimatly went big time!

one piston has completely dissapeared (there are bit's of it all around the engine and spat out the inlet and exhaust), and the other was beeten into a ball of ali (placed ontop of another piston in the pic)

one of the rods has snapped, and the remaining bit punched out the side of the cylinder bore, also one of the valve heads has got pushed ou the side of the block by the crank.

this happend at ~9,700 (hard to be exact!) but at this point it had been running non-stop for some 6 hours at WOT.

clearly looking at what is left, they cannot stand these sorts of revs, below 9,000 it was OK, however, how much further before this happens is in the lap of the gods...

what you make of this is up to you, suffice to say that for a stock engine we are not going to be running them in a race car at over 8,600.
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nikos said:
Simon, I do need to ask... What made you sucrifice these motors? And how did you do it? I mean on a car? engine dyno?
all done on the dyno, the idea of having an engine let go in a car is not my idea of fun!

dyno was configured to cycle the engine through a pre-set rev range at WOT, then log all the temps/pressures on the way, we has an oil cooler from hell on them so as to eliminate any oil temp issues (oil held at 110C), same for the water (86C) etc etc.


basically, I am racing with one in endurance races from 100mins to a full 24H race in a couple of months time, Having an engine let go when out racing is not an option, appart from the pain and heartache of DNF's, you get to learn very little as by the time you get the car back most of the detail you needed to know has gone and all you have is a smashed up engine.

People have gon on an on about what they will take/not take, so I decided to find out.

only problem with this is that it's just two engines, and this cannot be used as some kind of garentee that all will behave the same, that said, it's a good indication of what they will put up with.

currently, I am limiting the race cars engine to 8,600 which seems like a reasonable compromise (assuming that you can 100% control the oil and water temps). I will be trying the same tests with uprated internals as an when we decide which way to go.

one thing that stands out for us in all this is that the valve stems are painfully thin, so we are looking about for a more robust valve at the moment. (interestinly, the K20A2 engine showed zero sighns of any valve contact with the pistons etc. with stock springs.)
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nikos said:
The top two pictures look like the good piston has a high pent-roof style piston found in the Type R.

The bottom two pictures show a flatter top piston.

Are you sure they are not reversed?
don't get much past you guys :p

the pistons on the K20A2 had been changed.. it was running 12.5 CR. (this was one of the reasons for the test on this one to make sure they were not inferior to stock ones)

rsxmachine said:
curious, what valve spring & retainer combo were on each?
Valves & springs were stock, the valve actually broke just below the collet grove (as in at it's full diameter, not in the grove itself).

I would be interested to hear in anybody else has had valves fail like this and what other valves have been tested...
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