RazielDelSol

The stock pistons, or stock conrods in a d15b vtec?

I found a great set of rods ill be buying, but can't find a solid set of pistons at a decent price, was wondering if i could cheap out on pistons SLIGHTLY (not getting ebay **** for the engine haha)

I'm planning a lowish compression boost build for a swap and just need to know what's the weakest part of this.

NotARaCist

iTrader: (1)

Low CR is stupid. Stop it. Stop it right the **** now. Stay at stock CR, or higher. Period. End of story.

Supertech pistons are your winning answer for an affordable, good piston. The rods are the weak point for any D series engine. Aftermarket rods don't play well with OEM pistons, though - you can't mix and match floating pin with pressed pin, and the machine work to convert is prohibitively expensive when you compare it to the cost of a good set of pistons.

purgat0ry

iTrader: (3)

Why mod the d15b?
Your getting shoe horned into a narrow parts catalog right out of the gate.

tony_2018

I guess thats why the D-series was so popular, CHEAP.

RazielDelSol

Boost + high comp ratio is a bad idea. Not interested in arguing this point at all. But thanks for telling me about the piston compatibility issue, i hadn't thought of that, so I'll have to find a set of pistons too.

And i'm interested in the d15b because i can find more of those in my area, it seems the d16s get snatched up quickly.

VegaS10

Goddamnit.

NotARaCist

iTrader: (1)

You're wrong. There's no point to argue, because it's a known fact - you're wrong.

TheShodan

iTrader: (14)

Just let him, go, man.... let him drink the kool-aid.

NotARaCist

iTrader: (1)

The key difference, though, is that the ones who drank it in Jonestown died, and the stupid died with them. This "low CR for boost" idiocy won't die unless we shoot it in the face with a 12 gauge.

m4xwellmurd3r

You gotta make sure to double tap it to make sure it doesnt come back as a bloody zombie.

PyroProblem

Guys..

"Low" and "high" or totally subjective terms and can be different for everybody.
The question should be...

"What compression ratio works with the type of fuel I'll be using?"
The next question should be "how much do you trust your TUNER?"

TheShodan

iTrader: (14)

The level of questioning you make is great, but moot for purposes here.

NotARaCist

iTrader: (1)

Low and high aren't really subjective, for the sake of this argument. Stock is stock. Low is lower than stock. High is higher than stock. Low is wrong. High is right.

PyroProblem

When I hear low compression. I think 8-9 to 1.
When I hear high compression, I think 13:1+

What's too HIGH and what's too low. Dont think he mentioned what type of fuel he using. Doesn't that play a factor of what's too high?

PyroProblem

But anyway OP, not to stray off topic. Just upgrade both a both and be done. Its worth the extra few hundred bucks.
Good luck.

Aradin

Wouldn't go too high on a 1.5L. There's only so much real estate inside those little bitty cylinders. More piston = less real estate = less overall power potential. It's not like he's building the next 800hp D series though.

As a general rule I agree though; anything under 10:1 is dumb for a street car. Speaking from experience, I went from an 8.8:1 F22 to a 11:1 F22 and the high compression motor was superior in every way.

m4xwellmurd3r

And if you go broke building up the engine for boost and cant boost it, it still makes for a fun na engine hah

wantboost

iTrader: (2)

It's always the rods in D series engines

/thread.

Flr Power

Low CR build is not stupid. People and OEM often use around 9:1 CR because the engine will see no better than 91 oct. High CR and high boost don't mix.

Ultimately, you will make more power with a lower CR/high boost than a high CR/low boost with 91 oct. I understand that if you have two engines with the same horsepower then the bigger engine or the higher CR engine would be better on a track.

Just stop saying high CR is always the way to go, unless you have deal with pistons company.

OP, I would change both but it would be better to go to a different engine.

NotARaCist

iTrader: (1)

For this argument, OEM doesn't matter. OEM doesn't mean ****. OEM has the same "lowest common denominator" problem as the old FMU hack bullshit did, but on a much larger scale - they make thousands of engines, with thousands of components, and still need those engines to be reliable, both to keep warranty costs down, as well as to keep customer retention and satisfaction up.

We are talking about building engines for boost. I've already gone over all of this. I don't know why I need to say it again. Low CR is wrong. "Low CR/high boost" shouldn't even be a thing, either. When you are building a motor, if you build it correctly, with quality parts, there is absolutely nothing stopping you from running high CR along with high boost.

Or do you need a primer in turbo 101?

m4xwellmurd3r

Also low comp high boost, and high boost low comp, will make nearly the exact same hp if youre limited to 91 octane. Octane limits power. A 10.5:1 low boost setup will make roughly the same hp as a 8.5-9:1 comp high boost setup.

But high comp will whoop its *** lol.

Flr Power

No that's another myth. The fact is pressure inside the cylinder before the burning takes place sets the limit before detonation can occur.
Pressure is heat and low octane fuel is not good at resisting detonation. So, octane does not limit power per say since you could have a big engine running mild CR and have lots of power....

Schister66

That's all i came here to say. IIRC, D15 rods aren't the easiest/cheapest aftermarket piece to find.


Also, just to beat the horse a little further, skip the low comp idea - its an argument based on 1990s technology and is long outdated

m4xwellmurd3r

Im talking about two engines running the same displacment with the only variation being boost pressure and compression ratio.

No **** a bigger displacment engine can make more power with the same octane.

RazielDelSol

i was certain that i was acting with a pretty civil attitude when i posted.

regardless of whatever insult you fling my way or how angry you get behind your keyboard, i am not going to make any counter points, and will be doing what i see fit with my motor / money.

which is low comp + boost.

Thank you guys for the helpful imput though. Will be replacing rods & pistons when I do build it.