TwinTurboM3

why do many choose a 10:1 compression when they get a stroker kit?

any reason to raise compression?

still*boostn

iTrader: (15)

with the better tuning tools these days there is no need to run lower comp with a turbo. your limited on pump(kinda), but you get quicker spool. I was 30-32psi on pump and 10:1 on my 2.4 and it spooled like a stock turbo.

plus with a "stroker", or in my case just a bigger motor, we are limited to revving, so the extra CR helps with spool. and with e85 popn up everywhere you cant go wrong!

Im no expert, just my 2 cents.

Ted B

iTrader: (6)

Actually, the effect of raising the SCR delays spool, not quickens it. A higher SCR tends to make the engine feel a little peppier off-boost, so that tends to offset the effect to the perception of the driver.

One reason why engines with a short R/S ratio (strokers) are more forgiving to higher SCRs because the piston dwell at TDC is shorter for any given rpm, which means static cylinder pressure is reduced more rapidly per degree of crank rotation for any given rpm.

The theoretical difference in torque potential between 9:1 and 10:1 is small (<5%), so it's really a matter of fuel octane. Since many who put together 10:1 motors expect to run E85, the higher SCR is a non-issue.

n2oiroc

iTrader: (33)

bigger cams also tend to lower dynamic compression ratio, what exactly happens at high rpm and under boost with the added cylinder fill from the cams i have no idea how to calculate. i think the basic dynamic compression ratio calculators become void a bit past idle.

Tonba

iTrader: (1)

I thought bigger cams effected DCR and did nothing too SCR..

Also, I still think there is merit to having lower comp (say 8.5:1 or 9.0:1 over 10.0:1) on an E85 car.. as you could run more timing in the midrange/spool up where E85 is most prone to pre-det..

n2oiroc

iTrader: (33)

no you are right, i typed fast without thinking too much.

SeanC

iTrader: (7)

10.0:1 CR is very popular in E85 fueled engines, or one that uses higher octane fuel.

JE Pistons has 10.0:1 pistons for non-strokers available off-the-shelf.
http://www.jepistons.com/Catalogs/Sp...i/4g63_22.aspx

alanarias22

iTrader: (39)

sorry to bring back an old thread, but with a 10:1 cr on a 2.0 is it safe to tune at atleast 25psi on 93oct?

the car is running e85 at the moment but i would also like to have a 93oct map..

edit: these are the mods for a better response

Built 2.0
JE Pistons .20 over 10:1 upgraded wrist pins and coated sides
BC Rods w/ 625 bolts
Manley Crank
Balance shafts removed
Supertech stock size valves
Supertech Dual Valve Springs
Supertech Viton Seals
Supertech valves
ARP L19 head studs
Cosworth M2 cams

Svendiesel

iTrader: (25)

What kind of turbo is on your car? Youll probably be fine at 25psi...unless youre running a 42R or something mega that pushes a poopton of air lol.

My car with an FP Black on 93oct was at 28psi with 10:1cr.

alanarias22

iTrader: (39)

^^nice, and yeah, i have an fpblack also..
may i ask how much power you made?

Blue91lx

iTrader: (44)

I ran 24# on a 35r 10:1 2.0L, and it was extremely conservative. Made ~480whp.

I would think you could easily get away with 27-28lbs.

stunt2

iTrader: (8)

so in general, if using pump only and not E85, stick with slightly lower CR ? (2.3 stroker)

alanarias22

iTrader: (39)

nice, well the fp black has a 25psi actuator so my plans is to leave it at 25psi for the pump gas tune and have the mbc set to 35 psi for the e85 tune so when i switch maps all i have to do is connect the mbc

Blue91lx

iTrader: (44)

Meh, not really. You're still extremely limited using pump whether your compression is 9:1. The most you're gonna run on pump either way is ~30lbs. Most tuners can make 10:1 work on pump pretty well at higher boost levels anyway.

Blue91lx

iTrader: (44)

Sounds like a fantastic idea.