ok, so i've heard that hypereutectic pistons are pretty good, but i just read on a website that they arent so hot. anyone with a mild performance engine run with them? they would be going onto my ls eagle rods and i want to rev to 9k+ with 11.5-11.8:1 cr. let me know what you guys think. (please, dont throw useless opinions at me, i would prefer people who have experienced these)

unless someone makes me think other wise, shotpeened ls rods with arp rodbolts is out of the question. i really dont think that this would be safe, and i definitely could not rev over 8k w/o holding my breath and praying that my rods wont break. i would also grind off the groove on the side and balance them, i think its called flashover. thanks ahead of time.
nate

 

oops

 

Well, you speak in such big words, but they are not neccesary. Just say FORGED pistons.

And why do you want to rev over 9k rpm? It's useless unless your setup actually makes power there. And with a non-vtec engine, i'm not saying it's impossible, but highly unlikely, and probably not streetable.

Furthermore, just buying forged components doesn't grant you the freedom of revving high without problems. If you used forged components that are of the same dimensions as stock, then you really aren't doing much for yourself. You need to get your R/S ratio atleast to 1.75 before thinking of revving that high. The LS r/s ratio is 1.56 (if I remember correctly) and that will sideload the pistons waayy too much, and you're just asking for trouble.

So, before you go diving into an expensive and important process like this, make sure you cover 110% of everything that is going to make the engine work better and achieve your goals.

 

first of all: i got the valvetrain to support it
second: the topic is LS VTEC... so dont you think that i would have a vtec head
third: what do you mean overloading the sidewalls, im not running THAT high of a cr.
fourth: hypereutectic is not forged, 2 completely different things
fifth: dont flame unless you know what your talking about

anyone with a legitament response?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ScreaminTeg &raquo;</TD></TR><TR><TD CLASS="quote">Well, you speak in such big words, but they are not neccesary. Just say FORGED pistons. </TD></TR></TABLE>
Proll because hypereutectic pistons are not forged, they are cast. They are based on a very hild silica alloy, 390? I think.

At any rate, HR pistons are great for MILD engines, emissions, and fuel economy. Since they are very hard, you can run very tight piston/wall clearances. The problem with them is that they are VERY succeptible to detonation. Consider them nearly as fragile as, say, a rotor (from a wankel).

All in all, I wouldn't do it for performance, forged pistons are much more forgiving.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RevenantAE &raquo;</TD></TR><TR><TD CLASS="quote">
Proll because hypereutectic pistons are not forged, they are cast. They are based on a very hild silica alloy, 390? I think.

All in all, I wouldn't do it for performance, forged pistons are much more forgiving.</TD></TR></TABLE>

Correct. Hypereutectic is something like 15% or more silicon...doh

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dcb16 &raquo;</TD></TR><TR><TD CLASS="quote">first of all: i got the valvetrain to support it
second: the topic is LS VTEC... so dont you think that i would have a vtec head
third: what do you mean overloading the sidewalls, im not running THAT high of a cr.
fourth: hypereutectic is not forged, 2 completely different things
fifth: dont flame unless you know what your talking about

anyone with a legitament response?</TD></TR></TABLE>

I wasn't flaming you first of all. Don't be so defensive. I'm actually here to try and help, otherwise I wouldn't have posted at all.

What are you talking about a VTEC head to support it? To support what? 9k rpms Revs? That's great if it can 'support' it...but will it actually make power that high? What transmission are you going to use? That will play one of the biggest roles as to where your powerband lies.

With the R/S ratio of the LS, if you try to rev it to 9k rpm, you WILL side load the piston at an uneccesary rate, and will cause more stress, wear, and vibration against the cylinder walls. Thus, resulting in cylinder failure. The weight of the rods also plays a role in piston sideloading, and, not to mention, since the B18 doesn't have a great rod angle, it's going to contribute to more pressure against the cylinder wall at high revs.

If you don't want to consider any of that, it's fine. It makes no difference to me. I was trying to help you out...good luck with your engine, hope it works for you.

 

ill be using skunk stage 2's to make power 8k+ rpms. and to solve the r/s ratio problem i got some arp's. but please explain the side loading the pistons to me. anyone got more suggestions?

 

Ok..well, as far as sideloading a piston goes, this happens with poor R/S ratios which in turn leads to bad rod angles. Basically, what's happening is, the rod is forcing the piston against the cylinder wall instead of straight up or down. If serious enough, this can result into launching a rod through the cylinder wall.

I tried to come across some picture for you, here is one site that has some illustrations that might help understand it.

Piston side loading

I hope that helps you out. And I'm not trying to tell you that this is going to happen to your car, I am just trying to toss this info out to you so that you can better understand how the engine works. And since you are using the cams that are going to make power over 8k rpms, I can only assume that you are going to rev that high, so it would be my best opinion that the bottom end should be taken care of to be able to withstand those forces.

 

coo, thanks for the good info
when you say taken care of what exactly do you mean? sleeved? cuz i dont have the money for that...
and i was wondering, would a block gaurd or "posting" be helpful? thx man

 

You would not neccisarily need to sleeve the bottom end, but, maybe look at forged rods and pistons. Those shouldn't break the wallet, and would probably be wise. I've only seen a few applications where the block was "posted", so, I cannot give you accurate information on that. I haven't read up on it enough to understand it nor to recommend it for any application.

Just look for something that is going to give you a rod/stroke ratio of atleast 1.75.

That is rod length(mm) / stroke length(mm) = R/S ratio. You'll be much safer, whether or not the internals are forged or not.

 

i cant get a better r/s ratio unless i destroke (gsr crank) or overbore a lot. i can only bore out so much on my stock sleeves... so there really arnt any options, im just gonna do what i can with what i have. im polishing the rods and getting arp rod bolts. i honestly think that would be fine for a dailly driver and occasional trips to the drag.