bipedbear

alright, i wanna know, why are low compression pistons or "dished" pistons so much better for turbo, then stock or domed? and dont fill the screen with a bunch of math, i just want a straight out answer

ive also heard people say after market cams arent great with running a turbo either, im going to be building a motor and i wanna know what i should get..... what kind of a cam, and should i get 9:1 compression JE pistons for my b18a1 when running a t3....

Mindless

Higher compression isn't bad for boosting but lower compression means there's a less chance of detonation. I think I said that right.

IDk about how great turbo cams are. It seems to me that the any gains that you are going to get from a couple hundred dollar set of cams could easily be had by turning the boost up a little.

bipedbear

i think i just need a brainfart but what is detonation again, melting of the pistons or a ---- up in the ignition?

Scott-EP

its when it fires before the plug sparks cause of too high of temperatures and too much compression in a simple way of explaining it

BarelyBoosted

Low compression pistons make tuning a little easier also, more dependable but loss in low-end power. You gotta find that sweet spot.

As for cams, Not sure by your origanal post but there are NA cams(majority of aftermarket cams) and turbo cams.
NA cams suck on FI applications due to the amount of overlap(time when intake valve and exhaust valve are open at the same time), Allowing boost in go in and right back out. Someone correct me if i'm wrong.

Foowee

NA cams suck in constant pressure turbo systems where the exhaust manifold pressure is greater than the intake manifold pressure. If you have emp>imp situation when both valves are open reversion will occur. If you're emp<imp compression and overlap become your friends. Superchargers are the easy FI example of this. A higher imp than emp will clear the cylinder of heat and spent exhaust gasses that can cause detonation. I know there are turbo systems that exist where this situation also occurs, but I'm still gathering info.

Here's a good read:

http://forum.pgmfi.org/viewtopic.php?t=5148

and a couple examples of pulsed setups:

http://www.gurneyflap.com/zakspeedengine.html
http://www.gurneyflap.com/bmwturbof1engine.html

bipedbear

well i was going to go with the crower stage 2 cams which required a valve spring upgrade, but then i realized, i dont want want all that stiffness slapping the valves back against the seat on my daily driver car do i? do you guys know what i mean?

like those springs are going to mess up the valves and the seats over time correct? especially on a daily driver... maybe im just stupid, i dunno

Foowee

Honestly I'd say stick with the stock valvetrain. I don't think you would gain too much from cams & springs with a t3 on a ls. I'd also agree with your statement on the stiffer valve springs snapping the valves shut. I think cams are designed to gently set the valve into the seat, but when it's cold and there is clearance from the lash, I'd think the valves would definately be getting slammed into the seats with more force than the stock stuff. This is just my rambling though, I have no experience with aftermarket cams or springs for your setup.

beerbongskickass

First of all you need to get a vtec head. It will probably add 50whp give or take over the stock LS head. I would look for a complete b18c1/5 head or B16 head with gsr/itr cams. The b18a1 head is the worst head known to mankind and the cams suck *** (quoting Mr. Frank himself). Dyno sheets will prove how bad the top end is and we all know hondas are all top end. I would also get nothing less than a t3/t4 on any b-series motor.

The reason why low compression pistons are "better" is pretty much what everybody else has been saying. It will give you more room for error when your tuning... detonation = bad. Also remember you will be running pump gas, and you will be able to make more power safely running lower compression. Tuning will have to be perfect with higher compression and if your at the limit already, one bad tank of gas could mean a blown motor.

Here is a good article to read about high and low compression...

http://forums.evans-tuning.com/viewtopic.php?t=19