ok well me and my freind where arguing about the different pistons and compression ratios and it got me thinking ..anyways which is better for forced induction and why my friend said that the dished pistons create a "vortech" in the cylinder creating more power .. any ways this whole argument started when i told him that 8.8 :1 compresion on a GSR motor is not enough and then he said well ill be running a minimum of 14 psi ... also hiw motor is going to be running a PRO_Charger setup and the block is mostly built minus sleeves ,,....what do u guys think about the compression ratio ? and also which pistons do you run (flat top or dished) ? and why

also i seawrched (flat top piston, dished piston with no results)

 

have you tried searching for low compression vs. high compression? ill bet you'll find more than you can read in a day.

 

but this is low compression vs low compression so thhose thread wont help me too much ,.... but ill stil read them

 

ROFL, a vortech, never heard that before, I learn something new here every day. You may also want to look up "effective compression". I haven't seen much on H-T about it, but you can Google it, or try Googling "turbo effective compression".

 

yeah i thought the "vortech" thing was pretty funny also ... but really all i want to know is 8.8:1 on a a semi built GSR going to be better than say the flat top 9 :1 compressions pistons with the PRO charger set up ?

 

One thing that could make a huge difference is how the piston top reacts with the combustion chamber. I'm more familiar with DSMs and the 4G63, but it should relate on Hondas.

To get the flat top piston to have the same compression as a dished piston, you would have to increase the deck height, basically putting the piston down the bore at TDC. I have heard greatly conflicting points of view on this aspect. Many will say that it ruins the quench area and will lead to increased detonation potential.

However, on the later EVOs, they went to a nearly flat top piston, but put the piston down the bore to reduce the compression ratio. The motors need less timing advance to make a given power which suggests improved burn properties. Others have said that the typical burn pattern is much better then the burn pattern on a standard mitsubishi Eclipse 4G63 dished piston.

Either way, I picked up my pistons in a flat top flavor. Now I just have to decide on deck height and head gasket thickness to make this thing work.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slo_crx &raquo;</TD></TR><TR><TD CLASS="quote">yeah i thought the "vortech" thing was pretty funny also ... but really all i want to know is 8.8:1 on a a semi built GSR going to be better than say the flat top 9 :1 compressions pistons with the PRO charger set up ?</TD></TR></TABLE>


Not necessarily better or worse, a lower compression piston will make less power with no boost, but it will allow you to run more boost and more timing than a higher compression piston will on the same octane gas. Overall I think you can make more power by running more boost and timing on lower compression pistons, but I'm no expert, and there's plenty of H-T threads that deal with that issue.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slo_crx &raquo;</TD></TR><TR><TD CLASS="quote">yeah i thought the "vortech" thing was pretty funny also ... but really all i want to know is 8.8:1 on a a semi built GSR going to be better than say the flat top 9 :1 compressions pistons with the PRO charger set up ?</TD></TR></TABLE>

There is no such thing as a flat top 9:1 compression piston for your GSR unless you mill about 10CC's out of your cylinder head. I don't think you're really understanding this. A flat top piston is a 9:1 piston in a B16. Flat tops in a GSR give you around 10:1 compression, not 9:1. And think twice about buying a procharger, they're inferior compared to turbos.

Dished piston &gt; flat top &gt; dome

Read up for more info

 

ok well the pistons are relatvly flat top ... wiseco 9:1 's ... any ways its not my setup its my friends and he already baught the procharger ... so too later for him

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slo_crx &raquo;</TD></TR><TR><TD CLASS="quote">ok well the pistons are relatvly flat top ... wiseco 9:1 's ... any ways its not my setup its my friends and he already baught the procharger ... so too later for him </TD></TR></TABLE>

9:1 wiseco's have a 12CC dish, which are absolutely not a flat top.



If he got sold a piston that looks like the one on the bottom and they said it was a 9:1 flat top that piston is going to give him right around 10:1 compression, because the person sold it thinking it was a B16 9:1 flat top.

And who cares if he already has the procharger, sell it or take it back and get a real power adder. Centrifugally blown cars don't get 200 pound weight breaks and still run slower in domestic race classes because they're a great power adder.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">Not necessarily better or worse, a lower compression piston will make less power with no boost, but it will allow you to run more boost and more timing than a higher compression piston will on the same octane gas. Overall I think you can make more power by running more boost and timing on lower compression pistons</TD></TR></TABLE>I agree with you on this point. Much easier to tune for more boost made power when the compression ratio is lower.

 

i was gonna go 10.0:1 flat top in my ls vtec, that was with the b16a head on there. with the ls head it was like 9.6 or 9.7:1 that was zero deck height. i got a -9.3cc je piston now running zero deck height in the ls vtec now, so that gives me 9.3:1 ISH! due to slight decking to true the surfaces, they prolly went up to 9.4:1 tops.

 

So whats the final word? Which style is better for boost?
9:1 Flat top or 9:1 Dished?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">So whats the final word? Which style is better for boost?
9:1 Flat top or 9:1 Dished?</TD></TR></TABLE>

Read that link I posted. General consensus from around a dozen of the best engine and race car builders is that dished pistons are the best choice. This is a moot point though, because nobody is going to have a 9:1 flat top for a GSR/LSVTEC motor, it has to be dished.

 

thank you for every ones input im gonna make sure he can see this thread