B20-CRV VTEC - Why it Blows.....

na_power

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na_power

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if me playing vtec, b16b or b18c enough la with stroker kit, no need b20b, big block make the car heavier. :p. plus if bukak bonnet, b16b/b18c only maaa :biggrin:
 

shiroitenshi

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shiroitenshi

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loo, that doesn't seem typical of a detonated piston. Detonated piston have telltale signs of melting at the edges, and pitted surfaces. Which aren't apparent in your example.

It looks more like a head piston contact, or piston valve contact, and not at high rpms. coz at high rpms, all you get is a 3-20 pieces of piston in the windage tray, if the tray hasn't broken yet.

I also seen another forged piston (CP) with that kind of breakage. the piston actually hits the head at high rpm because the piston head clearance (or quench, as I've seen it referred to in some books)

Piston to deck height 0mm, while the minimum required clearances are usually 1-3mm, depending on the rod materials used.

Since people over here are the trial and error type, I think these things started not to surprise me a long time ago.

I think even some people can mess up degreeing s2 pro cams because they don't come with the typical cam setting numbers :P

Back to the b20b blowing issue.
Anyway, sometimes it's a stuck valve (valve sticks, piston meets valve, or valve drop due to retainer failing).

There's a recent one with a stuck valve (retainer is okay, it's just that the valve stays open because the valve got stuck in the guide.) The block is a goner though. the rod spun quite a few times inside it.

There's so many point of failures that it's hard to pinpoint to one source.

There's also possibility of rings seizing due to lack of proper clearances. people like to run tight ring clearances for power, but there's the risk they'll overheat if they can't get the proper clearances when they're very hot. You should try taking out the rings and bending them 90 degs. If they bend without breaking, the rings are 'fried', meaning they were heating up so much they seized. new rings that are not overheated, or 'annealed' will break if you even try bending them 45 degs. Detonation will also give the same effect, so it's not the 'end all' way of trying to see what part fails, so if the pistons have signs of detonation, it's likely the rings are not the cause, but if the piston is clean, it's likely the rings. I don't think people even check for vertical ring clearances over here.

Anyway, most ring packs in forged pistons packets need to be shaved to adequate clearances before use. I'm not sure I've seen anyone do it in a careful manner here.

Well, if people still think b20b are inherently weak, they are right.. but most are not due to the block, since if you talk to the americans.. b20b is weak because they can't stand the pressures of turbocharging.. not because they are weak that even NA setups can break them.
 

D-IV

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D-IV

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Exactly my point, i was looking through loo's piston picture last night and running lean is outta the question. It's rich enough but i'm not sure how much timing was ran on the piston because that may be the culprit too. Tight clearance on CP? Big mistake but i don't think that was the mistake because the coating looks fine to me (not sure what was the milleage before it did this though). A clearer picture would be easier, especially picture of the combustion chamber, valves and pistons....

What also bugs me is the crown looks ok and rich but the side picture looks pretty pitted. So too much timing is a maybe and valve contact can do such thing. But honestly its my first time seeing this kinda damage to a piston :hmmmm: We need to post more aftermath of blown engines and its anatomy :rofl:
 

dcloo

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dcloo

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loo, that doesn't seem typical of a detonated piston. Detonated piston have telltale signs of melting at the edges, and pitted surfaces. Which aren't apparent in your example.

It looks more like a head piston contact, or piston valve contact, and not at high rpms. coz at high rpms, all you get is a 3-20 pieces of piston in the windage tray, if the tray hasn't broken yet.

I also seen another forged piston (CP) with that kind of breakage. the piston actually hits the head at high rpm because the piston head clearance (or quench, as I've seen it referred to in some books)
if you saw detail of the piston its was melt cause by detonation,If valve touching its won't be on a side and you can saw a very new hit mark by valve , if head touching you can saw their the mark was around the piston if i can get back the picture piston touching the head i will post it here

For NA CP piston i not like much i have tested to install on 2 engine and its generate 2 much heat at valve pocket(hot spot) but for turbo i could tell you YES its really a nice piston i ever saw for turbo after MAHLE & Fierra
 

shiroitenshi

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shiroitenshi

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if you saw detail of the piston its was melt cause by detonation,If valve touching its won't be on a side and you can saw a very new hit mark by valve , if head touching you can saw their the mark was around the piston if i can get back the picture piston touching the head i will post it here

For NA CP piston i not like much i have tested to install on 2 engine and its generate 2 much heat at valve pocket(hot spot) but for turbo i could tell you YES its really a nice piston i ever saw for turbo after MAHLE & Fierra
The hot spots are always near the valve pockets because even on the stock engine, the hot spots are there as well. I think there's a picture I posted a while back of my engine with detonation signs on pistons, and as can be seen, it's localized to the valve pocket area mostly.. then again, most other engine too. I don't think it's cureable, because of the distance between the two exhaust valves, and that thin slice of aluminium seperating them.

If it's melted, usually in won't break off at one edge.. it's near impossible for detonation damage to be localised to one place.

Valve hit is possible, because if the valve 'floats', it's usually individual, and it's not that the valvespring is not working, it's more of because the valve didn't return to the seat fast enough.

Then again, I'm apt to think it hit the head, because the one I saw with the same breakage had this tiny little ring at the top of the piston that when measured, the diameter is the same with the hole in the head that was opened up. It did appear to have melted edges, because the chamber width was wide enough to 'fold' the sides to make it look like it melted.

I'm just giving my insight though. If you think it's detonation, then I think you already decided on possible ways of curing that problem.

I'm really not thinking much about detonation beign a prime cause for engine damage anymore, because seems like most people aren't running stupid high 6-8cc domes on the B20B anymore, so it's unlikely that detonation continue to be a major cause of engine blowing. most are in the region of low 12 or less. You can even see from the pistons that are brought in by tuner shops in Malaysia for B20B builds to be of average compression for street use, compared to the old days of bigger dome = better.

Frankly, I don't think NA engines output enough pressure to easily break any FORGED parts. Even the stock cast pistons can withstand knock somewhat. (usually the heat kills them first, aka piston seized) or the crank bearings get loose (due to knocking).

It's like the old days of overreving B16as for power.. most damage will be blamed on overreving, which is true, but even damage unrelated to overrevving gets blamed on overrevving.
 
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D-IV

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D-IV

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Would turbocharged motors tuned at 2.0bar boost running pump gas cylinder pressure be greater than NA car cylinder pressure when detonating?

Rod bearings will go first rather than crank bearing though. Ruining a crank is the last thing i want to happen, thats why i really stressed others who builds themselve to take it seriously :smokin:
 

J101

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J101

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am just wondering why would u want to risk driving a timebomb with compression that high with normal pump gas?

unless ure part of the mythbuster show lah trying to prove something :driver:

no matter what stand alone ECU/Piggyback you tuning your car running in 13.5:1 < CR with pump gas (petronas,sheel,mobil,bla bla bla) daily driving confirm your piston will melt/blow your engine

some sample picture show below using wesico 12.5:1 CR and skim head&block and around 13.5++:1 CR after 15000 KM tune with microtech LT 10s
 

D-IV

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D-IV

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Missed that statement. So it actually ran 15000km. Low fuel pressure due to pump, low fuel level and clogged injectors might be the culprit too then.
 

pencalat

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pencalat

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bro..
asking only..
thought ure using Jun3 in b20b..
did u do some mod on p3f for valve clearance(i mean valve pocket) to support high lift frm tht cam?
yeah dulu la for jun3 cams.... now skunk2 cam..
after nightmare come to my engine....
valve pocket i think my mech didn't done it..
i'll confirm with him later....
 

shiroitenshi

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shiroitenshi

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actually high lift is not the only problem. occasionally, it's the wrist pin location of the piston that can be an issue.

When running high lift cams, you should have at least 3mm clearance, esp. if using forged aluminum rods. at 8Krpm, should be okay with less than 3mm, but 9k+, better safer side with 3mm+, and sacrificing a little compression.

a lot of people never measure piston face to block deck height. This is important. It's more likely you get loose head bolts because of this, and not because of the high compression.
 

laut

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laut

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hi there
sorry i'm new in here
i'm not quite understand some info in here
so i want to ask some question
actually i'm interested to get honda with oredi change the block to b20b and b16a head
what i want to ask is the reliability compared to the standard one, like b16a, b18c
not rojakla, like i mention just now
is there any restriction that to be observe when using this setup:adore:
 

jessie

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jessie

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hi there
sorry i'm new in here
i'm not quite understand some info in here
so i want to ask some question
actually i'm interested to get honda with oredi change the block to b20b and b16a head
what i want to ask is the reliability compared to the standard one, like b16a, b18c
not rojakla, like i mention just now
is there any restriction that to be observe when using this setup:adore:
Do NOT VTEC 8,200 rpm all the way KL to Ipoh..............
 

laut

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laut

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Do NOT VTEC 8,200 rpm all the way KL to Ipoh..............
so the limit for this setup is 8000rpm compared to standard can stand 9000rpm rite
but i think standard also canot tahan if vtec all the way kl to ipoh, am i rite:hmmmm:
 
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