:::RHMT::: Real Home Made Turbo
General Category => Forced Induction => Topic started by: turbohf on July 26, 2014, 02:59:47 PM
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what is the appeal of Vitara pistons? they are still cast pistons, have stupid low compression usually. is the low compression the reason people are using these? or are they actually stronger than a standard D-series piston??
might seem like a stupid newb question, but the lower compression number is the only "benefit" i have heard people talk about... and really i think thats just some bullshit (that 7:1cr is a good thing).
edumacate me? ::)
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Thicker ringlands, and they are a hypereutectic. Hypereutectic pistons are still cast pistons, but they use a higher percentage of silicon in the base material, which makes them stronger than a standard cast piston.
That being said alot of people think that they are weaker than forged pistons. Stock lsx use hypereutectic and we have all seen how much power those take.
So they lower the comp, and you can pick them up for dirty prices. Alot of people think that if you lower the compression your loosing mass amounts of power. When in fact that's not all ways the case. Case in point. My ls setup.... 100% stock obd0 ls head, 8.0:1 comp 81.50mm weisco pistons and a obd0 exhaust manifold through stock exhaust and a obd0 pr4 ecu and it made better than stock numbers. If i recall right it was 126hp/119tq. And it was over a full point lower on compression. It was peppy na. Boosted it did ok but the stock head and small exhaust housing was the problem with that setup.
And the other reason is you can generally make more power on pump gas when it's boosted with lower compression.
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They are super low compression, cheap pistons you can hang on aftermarket rods.
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Just cause they are cheap that's why all the little fucks round here use them
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idk. just not sure that a cheap ass china piston is really gonna be any stronger than an OEM Honda piston. i mean i have seen broken/melted Vitara pistons just the same. real advantage i see that was noted above is that they can be mounted on an aftermarket rod with ease. and the low compression eases tuning also for those that are newbs.
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i did find this...
(https://realhomemadeturbo.com/forum/proxy.php?request=http%3A%2F%2Frushi.kapsi.fi%2Fpics%2Fvitarapistons%2FDSC00451.JPG&hash=08491dec9914b3680ccc199910cfc759707208ff)
picture borrowed from somewhere... ::)
looks like PM3 on the left. Vitara on the right.
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There cheap, and I made 500hp on them.
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idk. just not sure that a cheap ass china piston is really gonna be any stronger than an OEM Honda piston.
If you look at that vitara picture, it has a lot of improvements beyond material. Extra oiling holes in the oil control ring AND an extra oiling groove below it. The ringland between the compression rings (the one that usually breaks) is fatter and they even have more taper to account for the extra heat they're designed for. I can't say 100% if the newer Vitaras for real 75mm & 75.5mm bores are as tapered, but the "original" 74.96mm set I measured had a lot of taper above the oil rings.
The lower compression does help, and can be combated with more timing. The lower compression is more forgiving with crappy fuel and detonation, since the air charge is that much farther from auto-ignition temps. The 4g63 has a stock compression ratio of 7.8:1, and those pistons can make high power for a LOT more miles than a stock 9:1 or 10:1 Honda block.
The Honda H22 Type-S piston is a good example of how weak Honda cast pistons can be - they can break ringlands from just NA power. The clearances are set knowing they'll make more power than stock, so it's just plain old weak pistons. If you look at K20 pistons, the ringlands are MUCH thicker than B/D/H ringlands. They're actually thicker than Wiseco's & CP's forged K20 piston ringlands. That's one big reason B/D/H pistons can't take as much abuse as K20 stockers.
Regardless of how it can be explained, people have consistently made power & contained that power. There are no doubt several cars that dyno'd 500+ whp from stock pistons, but they either set power much lower to keep them together or blow them after some abuse at full power. I've never heard of a 500+ stock Honda that was driven at the level 100% of the time AND held together for a several thousand miles.