CammedEvo

iTrader: (5)

So, back in 06 i bought a stroker kit from a vendor on here. Got a really good deal on it.

Wiseco pistons
manley turbo tuffs
new mitsu crank
acl bearings

$1840.

Well over the last 5 years my car has had really bad detonation problems on pumpgas. Jestr e-flashed my car originally in 06 and he thought something was wrong because of how bad it wanted to detonate.

I learned to tune around the knock on pumpgas with really low timing numbers and eventually just turned the filters down and kept it out of 5th.

So it seems the same part number K596M855 is the 7bolt 2g piston and our piston.
Thing is when I put in all the stats from our cars i come up with 9.5-9.8 compression.

Someone please explain to me how the same piston in a car with a 4mm smaller combustion chamber and .24mm thinner headgasket equates even close to the same compression.

Is my logic off? or what am I missing here.

Ted B

iTrader: (6)

If we take a 4G63 with 100mm stroke, assume a 17cc piston dish, 44.5mm combustion chamber, 0.63mm compressed gasket thickness, and 0.1mm of deck height, we get a 9.7:1 SCR.

If we remove 4cc from the chamber, that brings us to 10.4:1.

If we trim 0.24mm from the compressed gasket thickness, that brings us to 10.6:1. In other words, one could end up with a full point higher SCR than expected.

Is this an aggravating factor? If they've goofed and the piston is identical, it would certainly seem reasonable to assume so.

What cams are you using presently?

xRoguex

iTrader: (15)

2.3 or 2.4?

I have a 2.4 with the "clock trick" done with stock cam gears. Had knock problems.

Degreed cams with adjustables. All gone.

CammedEvo

iTrader: (5)

GSC280's.. the og ones.

E85 solved the knock problem. There wasn't a knock problem on lower boost or low timing numbers.

Ted the piston is identical from what I can gather. Peep there catalogue same gram weight and part number/dish listed under both evo/late dsm

when i put in all the values for other evo pistons the numbers work out.

My car also has been milled twice, block and head.

My invoice gives the part number... I remember the box saying 4g63 and nothing about a evolution.

JohnBradley

iTrader: (30)

Older DSM pistons were also "timed" the pin was offset .020 and this can cause add'l issues that most people dont want to think about. Geometry changes as the piston is moving in addition to the normal changes makes things really interesting.

CammedEvo

iTrader: (5)

so help me understand this guys.

Look at wiseco's 2011 catalogue for sport compacts pg 52.

Evo pistons.. VS DSM pistons

Esp the e85 series.. Wouldn't the evo have a higher C:R with the thinner gasket and smaller chamber......... yet same piston has "higher" compression in a 2G.


http://www.wiseco.com/Catalogs/Sport...eteCatalog.pdf

CammedEvo

iTrader: (5)

bump for more feedback on this..

looks like next time i'll ask what BOV i should get or how much boost i can run.

n2oiroc

iTrader: (33)

the compression they list is often a rough estimate. so many little things change it and like ted b said it all adds up. dont really know what else you want to know. it sounds like your compression is too high. there are a few things you can do to prevent detonation. get the combustion chambers ported a bit, mine wound up at 48cc after porting. change cams/cam timing, etc.

CammedEvo

iTrader: (5)

Thank you for your feedback but if you'll re-read. I don't have a knock problem anymore.


I'm more or less asking how can wiseco est the same CR for both the evo and dsm apps with the differences in size of combustion chamber and hg

JohnBradley

iTrader: (30)

I saw that the other day when I was looking for high compression 2.3 pistons. My bet is it is backwards. 10:1 with big chamber, 10.5 in an Evo.

CammedEvo

iTrader: (5)

JB, The thing is check the weights/part #'s

they are est the same compression for the 2g and evo with the exact same piston WTF?

I'm trying to bring it to peoples attention that their "8.8:1" wiseco strokers are almost 10:1 if they've been decked!!!!!